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   30972篇
  免费   492篇
  国内免费   37篇
教育   22506篇
科学研究   2701篇
各国文化   358篇
体育   2221篇
综合类   39篇
文化理论   296篇
信息传播   3380篇
  2022年   164篇
  2021年   285篇
  2020年   457篇
  2019年   649篇
  2018年   908篇
  2017年   1017篇
  2016年   938篇
  2015年   597篇
  2014年   782篇
  2013年   6245篇
  2012年   725篇
  2011年   811篇
  2010年   667篇
  2009年   614篇
  2008年   708篇
  2007年   704篇
  2006年   618篇
  2005年   573篇
  2004年   537篇
  2003年   480篇
  2002年   514篇
  2001年   548篇
  2000年   517篇
  1999年   528篇
  1998年   318篇
  1997年   342篇
  1996年   368篇
  1995年   352篇
  1994年   331篇
  1993年   293篇
  1992年   412篇
  1991年   399篇
  1990年   426篇
  1989年   408篇
  1988年   390篇
  1987年   338篇
  1986年   348篇
  1985年   416篇
  1984年   371篇
  1983年   345篇
  1982年   300篇
  1981年   277篇
  1980年   230篇
  1979年   310篇
  1978年   293篇
  1977年   267篇
  1976年   224篇
  1975年   186篇
  1974年   176篇
  1973年   206篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
972.
The innovative performance of companies has been studied quite extensively and for a long period of time. However, the results of many studies have not yet led to a generally accepted indicator of innovative performance or a common set of indicators. So far the variety in terms of constructs, measurements, samples, industries and countries has been substantial. This paper studies the innovative performance of a large international sample of nearly 1200 companies in four high-tech industries, using a variety of indicators. These indicators range from R&D inputs, patent counts and patent citations to new product announcements. The study establishes that a composite construct based on these four indicators clearly catches a latent variable ‘innovative performance’. However, our findings also suggest that the statistical overlap between these indicators is that strong that future research might also consider using any of these indicators to measure the innovative performance of companies in high-tech industries.  相似文献   
973.
We present a practical way of adapting and using four research-based assessments for different purposes in an electricity and magnetism course for K-8 science teachers. The course is designed to accomplish conceptual change toward accepted scientific conceptions as well as introducing teachers to materials and activities appropriate for their classrooms. Our data support that using the research-based tests to identify alternative conceptions and discuss test results with teachers is a promising way to use the knowledge of alternative conceptions in professional development. We also identify some mismatches between the research of conceptual change and its use in programs of professional development.
Ji ShenEmail:
  相似文献   
974.
This updated edition of Care Practice Paper #3 presents the evidence for the benefits of continuous support in labor. The role of the doula is explained. Women are encouraged to plan for continuous support during labor and to consider including a woman experienced with childbirth among their labor support team.  相似文献   
975.
Focus-on-form English teaching methods are designed to facilitate second-language learners' noticing of target language input, where "noticing" is an acquisitional prerequisite for the comprehension, processing, and eventual integration of new grammatical knowledge. While primarily designed for teaching hearing second-language learners, many focus-on-form methods lend themselves to visual presentation. This article reports the results of classroom research on the visually based implementation of focus-on-form methods with deaf college students learning English. Two of 3 groups of deaf students received focus-on-form instruction during a 10-week remedial grammar course; a third control group received grammatical instruction that did not involve focus-on-form methods. The 2 experimental groups exhibited significantly greater improvement in English grammatical knowledge relative to the control group. These results validate the efficacy of visually based focus-on-form English instruction for deaf students of English and set the stage for the continual search for innovative and effective English teaching methodologies.  相似文献   
976.
A student in a Lamaze Childbirth Educator Program expresses concern that some Lamaze Certified Childbirth Educators (LCCE educators) do not teach classes that reflect Lamaze standards. In this column, the ethical and professional standards of the LCCE educator and the challenges the childbirth educator experiences while practicing in the current maternity-care environment are presented and discussed. Lamaze International's Code of Ethics for Lamaze Certified Childbirth Educators provides guidance when dealing with these challenges.  相似文献   
977.
Over the last decade, researchers have developed sophisticated online learning environments to support students engaging in dialogic argumentation. This review examines five categories of analytic frameworks for measuring participant interactions within these environments focusing on (1) formal argumentation structure, (2) conceptual quality, (3) nature and function of contributions within the dialogue, (4) epistemic nature of reasoning, and (5) argumentation sequences and interaction patterns. Ultimately, the review underscores the diversity of theoretical perspectives represented within this research, the nature of dialogic interaction within these environments, the importance of clearly specifying theoretical and environmental commitments throughout the process of developing or adopting an analytic framework, and the role of analytic frameworks in the future development of online learning environments for argumentation.
Douglas B. ClarkEmail:
  相似文献   
978.
In four experiments with rats, we examined the persistence of behavior when reinforcement was switched from immediate to delayed. In Experiment 1, lever pressing elicited by instrumental training with immediate reinforcement continued when a 20-sec delay of reinforcement was introduced (easy-to-hard condition), whereas when the delay condition was introduced from the start (hard-to-hard condition), responding remained low throughout. A similar result was obtained in Experiment 2, in which lever pressing was elicited by a classical conditioning (autoshaping) procedure. In Experiment 3, rats initially trained with delayed reinforcement continued to respond at a low rate when switched to immediate reinforcement (hard-to-easy condition). By measuring magazine entry (goal tracking) as well as lever pressing (sign tracking) in Experiment 4, we confirmed that such transfer effects at least partly involve the persistence of whatever type of behavior was initially dominant.  相似文献   
979.
Goat ovaries were collected from the slaughterhouse and categorized as right, left, corpus luteum (CL)-present and -absent group and evaluated on the basis of weight (g), length (cm), width (cm), number of follicles, follicles aspirated and number and state ofcumulus-oocyte-complexes (COCs). Comparatively higher weight [(0.66±0.02) vs (0.64±0.02) g], length [(1.17±0.02) vs (1.1 ±0.02) cm] and width [(0.77±0.02) vs (0.74±0.02) cm] were found in right ovaries than those of left. On the other hand significantly (P〈0.05) higher weight [(0.71±0.03) vs (0.64±0.01) g] and width [(0.76±0.03) vs (0.75±0.01) cm] were found in CL-present group than those of CL-absent group of ovaries. The left ovaries contained comparatively higher number of normal COCs [(1.06±0.09) per ovary] than fight ovaries [(1.03±0.10) per ovary] and the similar trend was found in total number of follicles [(4.51±0.25) vs (4.30±0.23) per ovary] and follicles aspirated [(2.55±0.14) vs (2.52±0.12) per ovary]. But the total COCs per ovary was almost similar in both ovaries [right and left: (1.85±0.12) and (1.85±0.11) per ovary, respectively]. Higher number of total COCs [(1.87±0.09) vs (1.76±0.16) per ovary], total number of follicles [(4.45±0.19) vs (4.16±0.37) per ovary], follicles aspirated [(2.55±0.10) vs (2.48±0.21) per ovary] and normal COCs [(1.12±0.07) vs (0.76±0.14) per ovary] were found in CL-absent group than those of CL-present group of ovaries.  相似文献   
980.
Supplemental instruction classes have been shown in many studies to enhance performance in the supported courses and even to improve graduation rates. Generally, there has been little evidence of a differential impact on students from different ethnic/racial backgrounds. At San Francisco State University, however, supplemental instruction in the Introductory Biology I class is associated with even more dramatic gains among students from underrepresented minority populations than the gains found among their peers. These gains do not seem to be the product of better students availing themselves of supplemental instruction or other outside factors. The Introductory Biology I class consists of a team-taught lecture component, taught in a large lecture classroom, and a laboratory component where students participate in smaller lab sections. Students are expected to master an understanding of basic concepts, content, and vocabulary in biology as well as gain laboratory investigation skills and experience applying scientific methodology. In this context, supplemental instruction classes are cooperative learning environments where students participate in learning activities that complement the course material, focusing on student misconceptions and difficulties, construction of a scaffolded knowledge base, applications involving problem solving, and articulation of constructs with peers.  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