全文获取类型
收费全文 | 15179篇 |
免费 | 227篇 |
国内免费 | 15篇 |
专业分类
教育 | 10551篇 |
科学研究 | 1857篇 |
各国文化 | 133篇 |
体育 | 1134篇 |
综合类 | 29篇 |
文化理论 | 195篇 |
信息传播 | 1522篇 |
出版年
2022年 | 117篇 |
2021年 | 178篇 |
2020年 | 247篇 |
2019年 | 357篇 |
2018年 | 501篇 |
2017年 | 528篇 |
2016年 | 458篇 |
2015年 | 308篇 |
2014年 | 434篇 |
2013年 | 2439篇 |
2012年 | 388篇 |
2011年 | 356篇 |
2010年 | 361篇 |
2009年 | 297篇 |
2008年 | 323篇 |
2007年 | 332篇 |
2006年 | 311篇 |
2005年 | 297篇 |
2004年 | 329篇 |
2003年 | 318篇 |
2002年 | 307篇 |
2001年 | 373篇 |
2000年 | 368篇 |
1999年 | 273篇 |
1998年 | 146篇 |
1997年 | 185篇 |
1996年 | 183篇 |
1995年 | 132篇 |
1994年 | 140篇 |
1993年 | 121篇 |
1992年 | 202篇 |
1991年 | 192篇 |
1990年 | 219篇 |
1989年 | 223篇 |
1988年 | 183篇 |
1987年 | 196篇 |
1986年 | 177篇 |
1985年 | 214篇 |
1984年 | 154篇 |
1983年 | 135篇 |
1982年 | 131篇 |
1981年 | 114篇 |
1980年 | 116篇 |
1979年 | 177篇 |
1978年 | 135篇 |
1977年 | 119篇 |
1976年 | 92篇 |
1975年 | 95篇 |
1974年 | 102篇 |
1973年 | 96篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
We report a case of a diabetic, heterozygote with near normal hematology, marginally low level of hemoglobin A2(HbA2) having an increased level of hemoglobin F(HbF) that was pancellularly distributed among the red cells. BioRad DiaSTAT measurements
gave a high glycated hemoglobin A1c(HbA1c) of 31.5% and the BioRad Variant analyzer recorded an HbA1c value which was very
low, in discordance with the detected blood glucose levels. Flow cytometry and polymerization chain reaction (PCR) based studies
were carried out which revealed the case to be that of the common hereditary persistence of fetal hemoglobin (HPFH)-3, an
Asian Indian mutation. Fructosamine estimation and HbA1c by Boronate affinity chromatography were able to resolve the discordant
value detected and was able to confirm the diabetes status. The case would have been a diagnostic dilemma, if reported without
correlation. 相似文献
992.
India seems to have the highest prevalence of osteoporosis. With growing awareness of osteoporosis and its impact on life
span especially in India, special attention is being paid to early detection, management and treatment of postmenopausal osteoporosis
in women. Measurement of BMD and osteocalcin are of value in estimating bone turnover rates. The aim of this study is (1)
to measure the specific, sensitive bone formation marker such as osteocalcin and BMD in postmenopausal osteoporosis women
and postmenopausal non-osteoporosis women; (2) the follow up study to evaluate the impact of specific antiresorptive therapy
(alendronate + calcium + vitamin D) regimen in postmenopausal osteoporosis by assaying osteocalcin and BMD. Sixty clinically
diagnosed postmenopausal osteoporosis patients and 60 normal subjects (postmenopausal non-osteoporosis women) were recruited
as control. Mean bone mineral density T score and Z score was significantly decreased (P < 0.001) in postmenopausal osteoporosis patients as compared to controls. Highly significant increase in the mean score of
BMD—T score and Z score from baseline to post therapy of 3 months was observed in postmenopausal osteoporosis women. Serum osteocalcin levels
were significantly increased (P < 0.001) as compared to control group. Serum osteocalcin levels were decreased significantly (P < 0.001) from baseline to post therapy of 3 months in postmenopausal osteoporosis women. BMD is the best quantifiable predictor
of osteoporotic fracture and osteocalcin is specific, sensitive, promising, currently used marker for better prognosis of
osteoporosis and for monitoring responses to antiresorptive therapy. 相似文献
993.
Franky D. Shah Rasheedunnisa Begum Bhairavi N. Vajaria Kinjal R. Patel Jayendra B. Patel Shilin N. Shukla Prabhudas S. Patel 《Indian journal of clinical biochemistry : IJCB》2011,26(4):326-334
Oral cancer has emerged as an alarming public health problem with increasing incidence and mortality rates all over the world.
Therefore, the implementation of newer screening and early detection approaches are of utmost importance which could reduce
the morbidity and mortality associated with this disease. Sensitive and specific biomarkers for oral cancer are likely to
be most effective for screening, diagnosis, staging and follow-up for this dreaded malignancy. Unlike other deep cancers,
oral cancer is located in oral cavity. Hence, the direct contact between saliva and oral cancer lesion makes the measurement
of tumor markers in saliva an attractive alternative to serum and tissue testing. The DNA, RNA and protein molecules derived
from the living cancer cells can be conveniently obtained from saliva. Thus, salivary biomarkers, a non-invasive alternative
to serum and tissue-based biomarkers may be an effective modality for early diagnosis, prognostication and monitoring post
therapy status. In the current post-genomic era, various technologies provide opportunities for high-throughput approaches
to genomics and proteomics; which have been used to evaluate altered expressions of gene and protein targets in saliva of
oral cancer patients. The emerging field of salivary biomarkers has great potentials to prove its clinical significance to
combat oral cancer. Hence, we have reviewed importance of several salivary genomics and proteomics biomarkers for oral cancer. 相似文献
994.
The European university landscape: A micro characterization based on evidence from the Aquameth project 总被引:2,自引:0,他引:2
Cinzia Daraio Andrea BonaccorsiAldo Geuna Benedetto LeporiLaurent Bach Peter BogetoftMargarida F. Cardoso Elena Castro-MartinezGustavo Crespi Ignacio Fernandez de LucioHarold Fried Adela Garcia-AracilAnnamaria Inzelt Ben JongbloedGerhard Kempkes Patrick LlerenaMireille Matt Maria OlivaresCarsten Pohl Tarmo RatyMaria J. Rosa Cláudia S. SarricoLéopold Simar Stig SlipersaeterPedro N. Teixeira Philippe Vanden Eeckaut 《Research Policy》2011,40(1):148-164
This paper provides a new and systematic characterization of 488 universities, from 11 European countries: Finland, France, Germany, Hungary, Italy, Netherlands, Norway, Portugal, Spain, Switzerland and UK. Using micro indicators built on the integrated Aquameth database, we characterize the European university landscape according to the following dimensions: history/foundation of university, dynamics of growth, specialization pattern, subject mix, funding composition, offer profile and productivity. 相似文献
995.
The aim of this paper is to present a reliability modeling and analysis of a two-unit system of a continuous casting (CC) plant. Real maintenance data of a steel production plant have been used for the purpose. Three types of failures were noted: repairable, replaceable and reconditioning/reinstallation. The two-unit system is operating in parallel, on full-reduced installed capacity. Upon the unit failure, an inspection is carried out to decide the type of maintenance task to be performed. Optimized reliability indices of the plant such as mean time to system failure, availability, expected busy periods of the repairman for various maintenance tasks, expected number of visits by the repairman, expected number of repairs, replacements and reconditioning/reinstallation are obtained. Semi-Markov processes and regenerative point techniques are used for the analysis. Profit incurred to the CC plant is also evaluated and related graphs are plotted to demonstrate the results. 相似文献
996.
Analytical expressions are derived from a single symmetrical relay feedback test for the identification of open loop stable and unstable non-minimum phase processes. The second derivative of the limit cycle output helps in finding the time delay of the process. The derived expressions can be used to identify the process models with up to five unknowns. The effectiveness of the proposed identification method is verified through different simulation results. 相似文献
997.
This paper studies bounded input bounded output (BIBO) stability for a class of neutral systems with time-varying delays. Based on Lyapunov method and linear matrix inequalities, some new BIBO stability criteria are established. The numerical simulation is made to demonstrate the effectiveness of the theoretical results obtained in this paper. 相似文献
998.
A simple design method for the cosine-modulated filter banks using weighted constrained least square technique 总被引:1,自引:0,他引:1
This paper presents a simple and efficient design method for cosine-modulated filter banks with prescribed stopband attenuation, passband ripple, and channel overlap. The method casts the design problem as a linear minimization of filter coefficients such that their value at ω=π/2M is 0.707, which results in a simpler, more direct design procedure. The weighted constrained least squares technique is exploited for designing the prototype filter for cosine modulation (CM) filter banks. Several design examples are included to show the increased efficiency and flexibility of the proposed method over the exiting methods. An application of the proposed method is considered in the area of sub-band coding of the ECG and speech signals. 相似文献
999.
Tércia Zavaglia TorresAuthor VitaeIvo Pierozzi Jr.Author Vitae Nadir Rodrigues PereiraAuthor VitaeAlexandre de CastroAuthor Vitae 《International Journal of Information Management》2011,31(2):121-127
The great contemporary organizational challenge for enterprises is to create a conceptual and methodological framework allows the management of knowledge by means of networks designed for social interaction. This statement is based on the premise that the competitive drive and sustainable success of the company depend on the introduction of new forms of production innovative processes, which can only be ensured through integrated approaches to knowledge management and the incorporation information technologies (IT). This is a reality that has already been accepted by the Brazilian Agricultural Research Corporation (Embrapa, its acronym in Portuguese), a Brazilian research, development, and innovation (RD&I) institution supporting agricultural sector. For some years now, Embrapa has been incorporating what it has learned about knowledge management into its strategic planning process. In this paper, we present a new approach to managing knowledge and information, and we analyze the need for research institutions to administer the knowledge they produce through an RD&I management model based multi- and inter-disciplinary teams, and multi-institutional research networks. 相似文献
1000.
Lidwien van de WijngaertAuthor Vitae Willem PietersonAuthor Vitae Marije L. TeerlingAuthor Vitae 《International Journal of Information Management》2011,31(5):415-419
Information technology allows national and local governments to satisfy the needs of citizens in a cost effective way. Unfortunately, citizens still tend to prefer traditional, more costly channels, such as the front desk, phone and mail. Through pilot projects government agencies attempt to influence this behavior of citizens, directing them towards the online channel. With this paper we provide insight into the possibility to influence citizens’ behavior in the complex landscape of multi-channel service provision. The paper systematically compares five pilot projects using a framework that is based on organizational and marketing literature. The results show that socio-psychological factors are crucial in multi-channel management, much more than the technology itself. We conclude that citizens can be directed towards the online channel. However, not all projects are successful. Economic and legal instruments tend to sort more direct effects than communication or service instruments. Moreover, organizational factors such as bureaucracy often hinder eventual success. Choosing a smart and relatively small scope and strong project manager may help to evoke success in directing citizen online behavior. 相似文献