全文获取类型
收费全文 | 1254篇 |
免费 | 24篇 |
国内免费 | 12篇 |
专业分类
教育 | 815篇 |
科学研究 | 226篇 |
各国文化 | 24篇 |
体育 | 100篇 |
综合类 | 5篇 |
文化理论 | 9篇 |
信息传播 | 111篇 |
出版年
2023年 | 9篇 |
2022年 | 11篇 |
2021年 | 27篇 |
2020年 | 30篇 |
2019年 | 41篇 |
2018年 | 49篇 |
2017年 | 72篇 |
2016年 | 49篇 |
2015年 | 38篇 |
2014年 | 49篇 |
2013年 | 190篇 |
2012年 | 47篇 |
2011年 | 53篇 |
2010年 | 51篇 |
2009年 | 38篇 |
2008年 | 46篇 |
2007年 | 39篇 |
2006年 | 30篇 |
2005年 | 34篇 |
2004年 | 19篇 |
2003年 | 26篇 |
2002年 | 25篇 |
2001年 | 28篇 |
2000年 | 24篇 |
1999年 | 27篇 |
1998年 | 4篇 |
1997年 | 6篇 |
1996年 | 13篇 |
1995年 | 11篇 |
1994年 | 8篇 |
1992年 | 12篇 |
1991年 | 13篇 |
1990年 | 7篇 |
1989年 | 7篇 |
1987年 | 10篇 |
1986年 | 8篇 |
1985年 | 17篇 |
1984年 | 12篇 |
1983年 | 12篇 |
1982年 | 10篇 |
1981年 | 5篇 |
1980年 | 7篇 |
1979年 | 5篇 |
1978年 | 7篇 |
1977年 | 4篇 |
1975年 | 11篇 |
1974年 | 6篇 |
1973年 | 7篇 |
1971年 | 7篇 |
1970年 | 4篇 |
排序方式: 共有1290条查询结果,搜索用时 15 毫秒
121.
122.
This paper presents the applications of the stability-equation method to the analysis and design of linear systems. Control systems with multiple inputs and outputs are considered; the absolute stability and relative stability characteristics are analyzed. Stability conditions for control systems with a transport lag or a distributive lag are presented. Finally, the stability characteristics of a system with a distributive parameter are analyzed. 相似文献
123.
Y. P. Bhandary K. N. Krithika Sandeep Kulkarni M. V. R. Reddy B. C. Harinath 《Indian journal of clinical biochemistry : IJCB》2006,21(1):1-7
Lymphatic filariasis caused mainly by infection fromW. bancrofti andB. malayi remains a major cause of clinical morbidity in tropical and subtropical countries. Analysis ofB. malayi mf, infective larval and adult worm lysates for the activity of enzymes led to the demonstration of activities of three key
enzymes of carbohydrate metabolism viz., Malate dehydrogenase (MDH), Malic enzyme (ME) and Glucose-6-phosphate dehydrogenase
(G6PDH) in all the three stages of the parasite. The specific activity of all the three dehydrogenases was significantly high
in mf lysate compared to their activity in lysates of the other two stages (P<0.001). Analysis by native polyacrylamide gel
to their activity inlysates of the other two stages (P<0.001). Analysis by native polyacrylamide gel electrophoresis (PAGE)
using 7.5% non-gradient gel showed the presence of two isoforms of each of the three enzymes (MDH, ME & G6PDH) in mf lysate,
while only one form of each enzyme was present in L3 larval and adult worm lysates. Further proteolytic enzyme activity was demonstrated both in microfilarial and infective larval
lysates ofB. malayi. While both mf and L3 larval lysates showed optimal protease activity at alkaline pH of 9.0, the mf lysate showed increased activity also at pH
3.0. The infective larval lysate was markedly inhibited by Tosylamide-L-Phenylalanine chloromethyl ketone (TPCK), a thiol
protease inhibitor, while the protease activity in mf lysate was significantly inhibited by both TPCK and a serine protease
inhibitor Phenyl Methyl Sulphonyl Flouride (PMSF). In sodium do-decyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE),
using gelatin copolymerized gel, the microfilarial lysate showed 3 protease molecules of 40 kDa, 180 kDa and 200 kDa and the
L3 larval lysate had 6 protease molecules of 18, 25, 37, 49, 70 and 200 kDa size. 相似文献
124.
K. S. Motghare Anil Bhutey B. B. Murrhar Madhur Gupta A. W. Meshram Y. Balsubramanium 《Indian journal of clinical biochemistry : IJCB》2001,16(2):213-215
With the growing interest in the concept of free radicals in the pathogenesis of myocardial ischemia, it was thought worthwhile
to study the changes in lipid peroxides and antioxidant enzyme glutathione peroxidase (GPx) in ischemic heart disease (IHD).
The study was carried out on 76 patients of IHD-38 of acute myocardial infarction (AMI) and 38 of stable ischemic heart disease
(SIDH). They were age and sex matched with 38 normal healthy controls. A significant increase (p<0.001) in lipid peroxides
as malondialdehyde (MDA) (5.9±0.7 mmol/L) and a decrease in GPx (24.6±2.2 U/gmHb) was found in patients of AMI when compared
with controls. There was no significant difference in these values in SIHD. Thus this study confirms the earlier findings
that MDA and GPx are useful parameters in IHD and their magnitude is dependent on severity and/or duration of ischemia. We
suggest that these tests would be of use in smaller institutions with limited facilities. 相似文献
125.
Several studies employing the "20 questions" test reported that reflective children asked proportionally more constraint-seeking (CS) questions than did impulsive children. The finding was interpreted as supporting the generally accepted view that reflective children are more mature and more efficient problem solvers than impulsive children. Inexplicably, the reflectives' higher proportion of CS questions was not associated with fewer questions to solution, that is, with greater efficiency. The present study examined an alternative hypothesis that differences in performance of impulsive and reflective children on the "20 questions" test are due to individual differences in preferred perceptual processing strategy rather than in cognitive maturity of problem-solving strategy. Efficiency of performance of reflective and impulsive children was shown to be related to type of stimuli and experimental conditions employed, supporting a perceptual rather than cognitive-maturational interpretation. 相似文献
126.
127.
Using a random sample of 389 grade 11 science students, the factor structure of the Longeot test (a measure of logical thinking) is investigated and some psychometric properties of the test items are determined. Varimax rotation on six principal component factors resulted in a simple structure. An attempt is made to interpret the obtained orthogonal factors. Implications of the findings on the “unity hypothesis” of the Piagetian construct of logical thinking and, consequently, on grade 11 science education are discussed. 相似文献
128.
Gifted girls of color represent a potentially untapped resource for increasing and sustaining a diverse science, technology, engineering, and mathematics (STEM) workforce. Girls of color possess unique mathematics and science gifts and talents that can remain unrealized if not addressed before middle school. Culturally responsive STEM out-of-school-time (OST) activities can be an effective means to develop STEM capacity in gifted girls of color. The researchers present three considerations to support the implementation of STEM OST. First, they offer a rationale for culturally relevant STEM enrichment activities for gifted girls of color. Next, the researchers consider how culturally relevant STEM OST activities can help to close the achievement gap. Finally, they explain how professional mentorship opportunities within OST activities can help gifted girls of color navigate the STEM pipeline. 相似文献
129.
Instructional design is not a linear process: designers have to weigh the advantages and disadvantages of alternative solutions,
taking into account different kinds of conflicting and changing constraints. To make sure that they eventually choose the
most optimal one, they have to keep on collecting information, reconsidering continuously whether their own decisions are
still justified in the light of the latest insights. We have studied the role of iteration during instructional design. For
our research, we have used an ISD-based method for the specification of training simulators. During our empirical evaluation
study, we introduced five events that are likely to cause iteration. The results show that the quality of the designs is not
directly related to the amount of iteration. We conclude that there are different kinds of iteration, triggered by different
kinds of actions and events. We propose a list of triggers for iteration some of which originate from outside (new information,
new opinions/arguments and acquisition procedures); others are caused by, or evolve from interaction with the design process
itself (discovery of missing input, need to repair errors, new insights based on work later on in the design process, and
new ideas of the designers).
in final form: 4 August 2005 相似文献
130.
The study examined whether schools for the deaf were providing services to assist parents in communicating with their children about sexuality (including sexual signs) and whether parents were involved in the sexuality education curriculum within their child's school. The Sexuality Curriculum Questionnaire for Educators of Students Who Are Deaf (Getch & Gabriel, 1998) was completed by 71 educators teaching sexuality curricula in schools for the deaf across the United States. Results indicated that parents were more likely to be involved in approval and development of their children's sexuality education than to receive assistance with sexuality education from the schools. Although the level of parental participation in curriculum development and approval is encouraging, the number of parents actually participating in curriculum development and approval remains low. 相似文献