首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   2234篇
  免费   35篇
  国内免费   1篇
教育   1475篇
科学研究   275篇
各国文化   15篇
体育   187篇
综合类   8篇
文化理论   11篇
信息传播   299篇
  2022年   22篇
  2021年   21篇
  2020年   26篇
  2019年   46篇
  2018年   50篇
  2017年   79篇
  2016年   70篇
  2015年   60篇
  2014年   67篇
  2013年   398篇
  2012年   58篇
  2011年   63篇
  2010年   52篇
  2009年   37篇
  2008年   48篇
  2007年   47篇
  2006年   37篇
  2005年   29篇
  2004年   40篇
  2003年   32篇
  2002年   28篇
  2001年   25篇
  2000年   42篇
  1999年   52篇
  1998年   21篇
  1997年   14篇
  1996年   19篇
  1995年   16篇
  1993年   14篇
  1992年   21篇
  1991年   33篇
  1990年   45篇
  1989年   34篇
  1988年   30篇
  1987年   21篇
  1986年   32篇
  1985年   39篇
  1984年   34篇
  1983年   28篇
  1982年   26篇
  1981年   22篇
  1980年   18篇
  1979年   27篇
  1978年   29篇
  1977年   20篇
  1976年   17篇
  1974年   17篇
  1971年   17篇
  1970年   14篇
  1968年   19篇
排序方式: 共有2270条查询结果,搜索用时 15 毫秒
31.
The dynamics of the impact and coalescence of droplets on a solid surface   总被引:1,自引:0,他引:1  
A simple experimental setup to study the impact and coalescence of deposited droplets is described. Droplet impact and coalescence have been investigated by high-speed particle image velocimetry. Velocity fields near the liquid-substrate interface have been observed for the impact and coalescence of 2.4 mm diameter droplets of glycerol∕water striking a flat transparent substrate in air. The experimental arrangement images the internal flow in the droplets from below the substrate with a high-speed camera and continuous laser illumination. Experimental results are in the form of digital images that are processed by particle image velocimetry and image processing algorithms to obtain velocity fields, droplet geometries, and contact line positions. Experimental results are compared with numerical simulations by the lattice Boltzmann method.  相似文献   
32.
Aprototype kit for the detection of occurrence of ovulation based on urinary pregnanediol glucuronide estimations by ELISA was developed in our laboratory. This kit was sent for evaluation at 4 centres in Bombay and Pune, India. The diagnosis of ovulation/anovulation based on the results of the kit is comparable with that based on reference parameters commonly used (ultrasonography of ovarian follicles and serum progesterone estimations). The accuracy of the test was 93.5%, specificity was 87.5% and sensitivity was 95.7%. This rapid indigenous test can be very useful in assessing ovulatory status of the woman by the clinicians in their offices.  相似文献   
33.
Higher-order statistics (HOS) are well known for their robustness to additive Gaussian noise and ability to preserve phase. HOS estimates, on the other hand, have been criticized for high complexity and the need for long data in order to maintain small variance. Since rank reduction offers a general principle for reduction of estimator variance and complexity, we consider the problem of designing low-rank estimators for HOS. We propose three methods for choosing the transformation matrix that reduces the mean-square error (MSE) associated with the low-rank HOS estimates. We also demonstrate the advantages of using low-rank third-order moment estimates for blind system estimation. Results indicate that the full rank MSE corresponding to some data length N can be attained by a low-rank estimator corresponding to a length significantly smaller than N.  相似文献   
34.
35.
A 64-year-old security guard and longstanding known hypertensive presented with hypertensive heart disease (HHD), weight loss, an enlarged prostate, and a spontaneously fractured rib. Malignancy of the prostate with possible metastases to the ribs was strongly suspected. Biochemical profiling revealed a paraprotein. Other biochemical and hematological correlates that were on hand before serum protein electrophoresis were rather atypical. Paraprotein studies by immunofixation revealed IgA myelomatosis. Unlike previous reports from Caucasians there was normocalcaemia, normal protein level, microcytic hypochromia, low MCHC, cholesterol level at the lower limit of the reference range and normal urea level (in the face of markedly raised creatinine level). Nutritional modulation of the classical laboratory features of this disease may account for the fairly atypical laboratory picture. The need to appreciate the influence of nutritional status on the laboratory (especially biochemical) features of a disease and thus interpretation of diagnostic tests appears of exceptional current importance, given the widening gap in socioeconomic status and the level of poverty between the resource poor and developed countries from which the classical, clinical and laboratory features of most diseases were first described. This case report reminds of the need not only to recognize theoretically the impact of nutritional status on the laboratory characteristics of a disease but of the practical application of the nutritional perspective in the interpretation of diagnostic investigations, especially in nutritionally disadvantaged communities.  相似文献   
36.
37.
The purpose of this investigation was to examine the efficacy of a new preschool oral language and early literacy curriculum package (Teaching Early Literacy and Language [TELL]) for children with developmental speech and/or language impairment (DSLI) either as a primary (e.g., specific to speech and/or language) or secondary impairment (e.g., developmental delay that includes DSLI). Participants included 118 children (30 females, 88 males, M age = 53.58 months) with DLSI and their 29 preschool teachers. The design was a randomized controlled trial (RCT) with assignment to experimental versus contrast conditions at the classroom level. Teachers in TELL classes received formal training, in-class support, and mentoring to implement the curriculum. Dependent measures for the children included scores on the Clinical Evaluation of Language Fundamentals-Preschool 2nd edition (CELF-P2), the Phonological Awareness Literacy Screening for Preschool (PALS-PreK), the Renfrew Bus Story (BUS), and a receptive and expressive vocabulary measure developed for this investigation (VOCAB). Results indicated that when compared to the contrast group, children in the TELL condition demonstrated greater gains on the phonological awareness subtest of the CELF-P2, the sentence length score of the BUS, the letter sounds, beginning sound awareness, and rhyme awareness subtests of the PALS-PreK, and VOCAB. Results suggest that the TELL curriculum package has promise for promoting gains in early literacy and oral language skills in preschool children with DLSI.  相似文献   
38.
Scholars who have taken interest in Theaetetus' educational theme argue that Plato contrasts an inferior, even dangerous, sophistic education to a superior, philosophical, Socratic education. I explore the contrasting exhortations, methods, ideals and epistemological foundations of Socratic and Protagorean education and suggest that Socrates' treatment of Protagoras as educator is far less dismissive than others claim. Indeed, Plato, in Theaetetus, offers a qualified defence of both Socrates and Protagoras. Socrates and Protagoras each dwell in the middle ground between the extremes presented in the dialogue's digression, which contrasts the life of the philosopher and the life of the courtroom orator. Both Socrates and Protagoras demonstrate a serious engagement with both politics and philosophy. Theodorus presents an educational option in which theory is divorced from politics while an ignoble sophistic education is presented as political but divorced from theory. Protagorean education, in Theaetetus, emerges as superior to a base sophistic education, though it remains inferior to Socratic education.  相似文献   
39.
The main aspects of the creation of a monitoring system for the research activities of the members of a higher-education institution are considered. The scientific activities of the lecturers and members of Turgenev Orel State University is used as the basis. It is expected that this system will be an efficient tool for optimal managerial decisions at all levels.  相似文献   
40.
1.Introduction The reproduction systems of 3D images without using eyeglasses and other special accessories has always attracted attention and aroused great interest of developers and consumers of such equipment because of totally accurate image and method of its presentation.Such systems can be used and are already partially used in advertising,television,different devices (i.e.smartphones,tablet computers),at the exhibitions,etc.,as well as in various technical applications,training systems,simulators,etc.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号