全文获取类型
收费全文 | 6219篇 |
免费 | 80篇 |
国内免费 | 7篇 |
专业分类
教育 | 4158篇 |
科学研究 | 681篇 |
各国文化 | 58篇 |
体育 | 598篇 |
综合类 | 9篇 |
文化理论 | 98篇 |
信息传播 | 704篇 |
出版年
2023年 | 41篇 |
2022年 | 60篇 |
2021年 | 92篇 |
2020年 | 167篇 |
2019年 | 238篇 |
2018年 | 362篇 |
2017年 | 383篇 |
2016年 | 321篇 |
2015年 | 213篇 |
2014年 | 243篇 |
2013年 | 1152篇 |
2012年 | 221篇 |
2011年 | 225篇 |
2010年 | 173篇 |
2009年 | 144篇 |
2008年 | 128篇 |
2007年 | 155篇 |
2006年 | 98篇 |
2005年 | 104篇 |
2004年 | 96篇 |
2003年 | 84篇 |
2002年 | 79篇 |
2001年 | 110篇 |
2000年 | 85篇 |
1999年 | 73篇 |
1998年 | 70篇 |
1997年 | 55篇 |
1996年 | 64篇 |
1995年 | 42篇 |
1994年 | 41篇 |
1993年 | 30篇 |
1992年 | 59篇 |
1991年 | 53篇 |
1990年 | 42篇 |
1989年 | 46篇 |
1988年 | 39篇 |
1987年 | 34篇 |
1986年 | 35篇 |
1985年 | 43篇 |
1984年 | 42篇 |
1983年 | 24篇 |
1982年 | 35篇 |
1981年 | 29篇 |
1979年 | 36篇 |
1978年 | 33篇 |
1977年 | 24篇 |
1976年 | 19篇 |
1974年 | 22篇 |
1972年 | 26篇 |
1971年 | 20篇 |
排序方式: 共有6306条查询结果,搜索用时 15 毫秒
941.
Casikar V Mujica E Mongelli M Aliaga J Lopez N Smith C Bartholomew F 《Indian journal of clinical biochemistry : IJCB》2010,25(3):311-314
Andean Indians have used coca leaves (Erythroxylon coca and related species) for centuries to enhance physical performance. The benefits and disadvantages of using coca leaf have
been a subject of many political debates. The aim of this study was to investigate the effects of chewing coca leaves on biochemical
and physiological parameters. Cutaneous microdialysis catheters were used to estimate systemic biochemical changes. We subjected
10 healthy adult males (local residents) in Cajamarca (Peru, altitude 2700 m) to a standardised exercise routine on a stationary
cycle ergometer. The blood pressure, oxygen saturation (digital), pulse, VO2 max and ECG (Holter monitor) were recorded before
the exercise. Cutaneous microdialysis catheters were introduced in the forearm. The subjects were given to chew 8 g of coca
leaves with a small amount of lime. They were then placed on the cycle ergometer for 20 min. Blood pressure, oxygen saturation,
pulse, ECG and VO2 max were recorded. Pyruvate, glucose, lactate, glycerol and glutamate levels were estimated. Oxygen saturation,
blood pressure, and pulse rate did not show any significant changes between the two groups. Glucose levels showed hyperglycaemic
response. Glycerol, Lactate and Pyruvate increased. Glutamate remained unchanged. Similar changes were not seen in the controls.
These results suggest that coca leaves have blocked the glycolytic pathway of glucose oxidation resulting in accumulation
of glucose and pyruvate. The energy requirement for exercise is being met with beta-oxidation of fatty acids. The glycerol
released was also getting accumulated since its pathway for oxidation was blocked. These experimental findings suggest that
chewing coca leaves is beneficial during exercise and that the effects are felt over a prolonged period of sustained physical
activity. 相似文献
942.
A. Supriya Simon D. Dinesh Roy V. Jayapal T. Vijayakumar 《Indian journal of clinical biochemistry : IJCB》2010,25(2):164-168
Cardiometabolic syndrome is one of the major public health issues of this century which describes a cluster of clinical characteristics.
Seventy two patients with coronary artery disease (CAD) and cardiometabolic syndrome and forty healthy age and sex matched
normal controls were selected for this study. Detailed clinical epidemiological and anthropometric characteristics were noted.
Lipid profile and Cytokinesis-block micronuclei (CBMN) assay using cytochalasin B were carried out in all the subjects. Serum
total cholesterol, triglyceride and LDL-cholesterol was significantly higher and HDL cholesterol was significantly lower in
patients compared to their normal counter-parts (P<0.05). CBMN frequency of the patients was significantly higher at all ages
compared to their normal counter parts (P<0.05). Various risk factors like diabetes, hypertension, dyslipidemia, abdominal
obesity, smoking and alcoholism were found influenced the CBMN frequency; but the changes were not significant. From this
study it can be concluded that DNA damage was found to be higher in patients with cardiometabolic syndrome which may be attributed
to the generation of free radicals associated with alcohol consumption, tobacco use, dyslipidemia and glucose intolerance
and the accumulation of free radicals with increase in age. 相似文献
943.
Kavita K. Shalia V. K. Shah M. R. Mashru S. L. Soneji J. B. Vasvani S. S. Payannavar A. P. Walvalkar R. A. Mokal S. M. Mithbawkar K. V. Kudalkar A. Abraham P. K. Thakur 《Indian journal of clinical biochemistry : IJCB》2010,25(1):20-28
The study aimed to analyze the circulating levels of thrombotic and haemostatic components; tissue factor, tissue factor pathway inhibitor, tissue plasminogen activator and plasminogen activator inhibitor-1 in patients with acute myocardial infarction at presentation (Group 1, n=49), unstable angina and Non-ST elevated MI after treatment (Group 2, n=22), stable angina (Group 3, n=18) and healthy individuals (Group 4, n=31). Significant finding was increase in tissue factor not only in Group 1 (2.0 fold, P=0.001), Group 2 (2.2 fold, P=0.015) but also in Group 3 (1.8 fold, P=0.018) as compared to controls. In Group 1 Plasminogen activator inhibitor-1 increased significantly (35.8%, P=0.02). Tissue factor pathway inhibitor and tissue plasminogen activator demonstrated increase in Group 1 of age<40 years while insignificant changes in elder patients. Increased thrombotic and decreased fibrinolytic conditions in acute myocardial infarction patients were observed. Increase TF in stable angina demonstrates procoagulant status in these patients as well. 相似文献
944.
Knowledge Management Research & Practice - Being competitive entails continuously performing product and process innovations. The acquisition of externally generated R&D is therefore... 相似文献
945.
Putative Role of Cardio Metabolic Risk Among Poorly Controlled Asthmatics in South Indian Population
Murugaiyan Sathish Babu K. P. Sreesoorya Surendra K. Menon Subiman Saha A. R. Srinivasan S. Arul Vijaya Vani R. Reeta V. Kuzhandai Velu 《Indian journal of clinical biochemistry : IJCB》2017,32(2):225-229
Mortality and morbidity attributed to asthma remains to be the biggest nightmare worldwide. Hence, the study was aimed to compare the cardio metabolic risk factors as assessed by Body mass index (BMI), waist hip ratio (WHR), serum triacylglycerol and uric acid in well controlled and poorly controlled asthmatics and to correlate these parameters with the severity of asthma. A case control study was conducted on 90 subjects who were segregated into well controlled asthmatics (n = 30) and poorly controlled asthmatics (n = 30) who were diagnosed based on Global initiative for Asthma management guidelines and healthy volunteers (n = 30). Centrifuged fasting venous blood samples were used for biochemical analysis, pulmonary function test, BMI, and waist hip ratio (WHR) were measured. The statistical analysis was done using SPSS version 17. There was a significant increase in BMI, WHR, lipid profile, serum uric acid and decrease in forced expiratory volume (FEV1), forced vital capacity (FVC), and FEV1/FVC in poorly controlled asthmatics. There was a significant association between FEV1 and serum uric acid, BMI and Triacylgycerol in poorly controlled asthmatics. Poorly controlled asthmatics have greater risk of developing cardiometabolic problems. Serum uric acid can be used as one of the severity markers in asthma to assess cardio metabolic risk. 相似文献
946.
八、观察断言句 可观察物以这种方式--"每当这样,就那样"组成的普遍性,就是我所称的观察断言句.它是由观察句组成的."每当"不是用来具体化时间,也不是用来量化时间.它是用来表示先于任何对象指称的不可还原的普遍性.它是关于这种效应的普遍性,即某观察句里所描述的情况总是伴以在另一观察句里所描述的情况. 相似文献
947.
Jill V. Jeffery 《Assessing Writing》2009,14(1):3-24
Persistent gaps between optimistic state and pessimistic national academic performance assessment results are increasingly leading to calls for unified national standards in the US. Critics argue that these gaps reveal vast differences in how proficiency is conceptualized; however, little is known about how conceptualizations compare among large-scale US assessments. To explore this issue, the present study investigated constructs of writing proficiency implicated in 41 US state and national high school direct writing assessments by analyzing the relationships between prompt-genre demands and assessment scoring criteria. Results of this analysis suggest that national writing assessments differ as a group from state assessments in the extent to which they emphasize genre distinctions and present coherent conceptualizations of writing proficiency. The implications of these assessment variations for college preparedness are discussed. 相似文献
948.
Antonio Perianes-Rodríguez Zaida Chinchilla-Rodríguez Benjamín Vargas-Quesada Carlos Olmeda Gómez Félix Moya-Anegón 《Journal of Informetrics》2009,3(2):91-101
Governmental initiatives around scientific policy have progressively raised collaboration to priority status. In this context, a need has arisen to broaden the traditional approach to the analysis and study of research results by descending to the group or even the individual scale and supplementing the output-, productivity-, visibility- and impact-based focus with new measures that emphasize collaboration from the vantage of structural analysis. To this end, the present paper proposes new hybrid indicators for the analysis and evaluation of individual research results, popularity and prestige, that combine bibliometric and structural aspects. A case study was conducted of the nine most productive departments in Carlos III University of Madrid. The findings showed hybridization to be a tool sensitive to traditional indicators, but also to the new demands of modern science as a self-organized system of interaction among individuals, furnishing information on researchers’ environments and the behaviour and attitudes adopted within those environments. 相似文献
949.
We analyze the advent and development of eight scientific fields from their inception to maturity and map the evolution of their networks of collaboration over time, measured in terms of co-authorship of scientific papers. We show that as a field develops it undergoes a topological transition in its collaboration structure between a small disconnected graph to a much larger network where a giant connected component of collaboration appears. As a result, the number of edges and nodes in the largest component undergoes a transition between a small fraction of the total to a majority of all occurrences. These results relate to many qualitative observations of the evolution of technology and discussions of the “structure of scientific revolutions”. We analyze this qualitative change in network topology in terms of several quantitative graph theoretical measures, such as density, diameter, and relative size of the network's largest component.To analyze examples of scientific discovery we built databases of scientific publications based on keyword and citation searches, for eight fields, spanning experimental and theoretical science, across areas as diverse as physics, biomedical sciences, and materials science. Each of the databases was vetted by field experts and is the result of a bibliometric search constructed to maximize coverage, while minimizing the occurrence of spurious records. In this way we built databases of publications and authors for superstring theory, cosmic strings and other topological defects, cosmological inflation, carbon nanotubes, quantum computing and computation, prions and scrapie, and H5N1 influenza. We also built a database for a classical example of “pathological” science, namely cold fusion. All these fields also vary in size and in their temporal patterns of development, with some showing explosive growth from an original identifiable discovery (e.g. carbon nanotubes) while others are characterized by a slow process of development (e.g. quantum computers and computation).We show that regardless of the detailed nature of their developmental paths, the process of scientific discovery and the rearrangement of the collaboration structure of emergent fields is characterized by a number of universal features, suggesting that the process of discovery and initial formation of a scientific field, characterized by the moments of discovery, invention and subsequent transition into “normal science” may be understood in general terms, as a process of cognitive and social unification out of many initially separate efforts. Pathological fields, seemingly, never undergo this transition, despite hundreds of publications and the involvement of many authors. 相似文献
950.
A. S. Bugaev E. L. Loginov A. N. Raikov V. N. Saraev 《Scientific and Technical Information Processing》2009,36(1):68-72
The information problems of management in an information and electronic society are considered and the technologies for carrying out statistical analysis with the use of various types of information are evaluated. 相似文献