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   23918篇
  免费   347篇
  国内免费   14篇
教育   17058篇
科学研究   1938篇
各国文化   261篇
体育   2340篇
综合类   7篇
文化理论   222篇
信息传播   2453篇
  2021年   241篇
  2020年   380篇
  2019年   580篇
  2018年   783篇
  2017年   712篇
  2016年   708篇
  2015年   417篇
  2014年   554篇
  2013年   4354篇
  2012年   494篇
  2011年   542篇
  2010年   408篇
  2009年   446篇
  2008年   483篇
  2007年   445篇
  2006年   420篇
  2005年   360篇
  2004年   395篇
  2003年   312篇
  2002年   327篇
  2001年   459篇
  2000年   511篇
  1999年   437篇
  1998年   255篇
  1997年   250篇
  1996年   310篇
  1995年   246篇
  1994年   259篇
  1993年   222篇
  1992年   350篇
  1991年   368篇
  1990年   339篇
  1989年   365篇
  1988年   337篇
  1987年   328篇
  1986年   325篇
  1985年   370篇
  1984年   293篇
  1983年   305篇
  1982年   240篇
  1981年   247篇
  1980年   259篇
  1979年   349篇
  1978年   258篇
  1977年   238篇
  1976年   199篇
  1975年   181篇
  1974年   182篇
  1973年   177篇
  1971年   174篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
971.
A recent meta-analysis performed by Wellman, Cross, and Watson clears the air surrounding young children's performance on tests of false belief by showing that it is highly likely that there is some type of conceptual development between 3 and 5 years of age that supports improved task performance. The data concerning the evolutionary origin of these abilities, however, is considerably less clear. Nonetheless, there is some reason to suspect that theory of mind is unique to our species, and that its original function was to provide a more abstract level of describing ancient behavioral patterns (such as deception, reconciliation, and gaze following)-behaviors that humans share in common with many other species. Thus, the initial selective advantage of theory of mind may have been because it increased the flexibility of already-existing behaviors, not because it generated scores of radically new ones.  相似文献   
972.
Previous studies of the concept of entropy have indicated that before 7 to 9 years of age, children have difficulty understanding the effects of randomizing forces and often predict highly improbable events, such as a return to the original ordered state. In the present research, 306 children between 3 and 11 years of age were asked directly whether undifferentiated forces, such as the wind or objects being thrown into the air, could create order or disorder in a set of objects. The results showed that even 4-year-olds are sensitive to the asymmetrical effects of such events. Older children apply this principle more consistently and are able to use it in explaining their answers.  相似文献   
973.
Reading readiness varies as a function of family and environmental variables. This study of 11-year-old children (N = 39) was designed to determine if there was an additional or interactive contribution of brain structure. Evidence is presented that both environmental and biological variables predict phonological development. Temporal lobe (planar) asymmetry, hand preference, family history of reading disability, and SES explained over half of the variance in phonological and verbal performance. The results demonstrate a linear association between cerebral organization and phonological skill within socioeconomic groups. These data provide concrete evidence to support the commonly held assumption that both environmental and biological factors are independent determinants of a child's ability to process linguistic information.  相似文献   
974.
975.
OBJECTIVE: The research sought to examine the overlap in coverage between several health-related databases, thus enabling the identification of the most important sources for searching for information on the rehabilitation of people with severe mental illness. METHODS: The literature was searched within a systematic review. Several health-related databases were retrieved (Cumulative Index to Nursing and Allied Health Literature, The Cochrane Library, MEDLINE, PsycLIT, Sociofile, and Social Science Citation Index), noting their source and comparing results retrieved from each database. FINDINGS: The total number of studies retrieved from each database varied. Almost a third of the papers retrieved from each database were unique to that source. Forty-two percent of the papers were only found in one database. Restricting a search to one database alone would miss many papers and could affect the results of a systematic review. PsycLIT was the most useful database for this topic area, containing 44% of the papers. MEDLINE, the database of first choice for many health professionals, held only 29%. CONCLUSIONS: No database was determined to be significantly more useful than any other--each warranted inclusion in the study. Reliance cannot be placed on one database alone, and other methods such as hand searching should also be used. Although this may not be new information for information professionals, it is likely to be new for health professionals and researchers who are increasingly performing their own literature searches. Information professionals have an important role to play in conveying this message to those outside their profession.  相似文献   
976.
The annual Janet Doe Lecture was established in 1966 to honor Janet Doe, emerita librarian of the New York Academy of Medicine. The lecture focuses on either the history or philosophy of health sciences librarianship. This lecture addresses three fundamental values of the field, highlighting basic beliefs of the profession that are at risk: privacy, intellectual property rights, and access to quality information. It calls upon readers to make the everyday choices required to keep the value system of health sciences librarianship in place. Robert Frost's poignant poem "The Road Not Taken" provides the metaphor for examining choices in an information economy.  相似文献   
977.
PURPOSE: Identify journal collection access and use factors. SETTING AND SUBJECTS: University of North Carolina at Chapel Hill's Health Sciences Library patrons. METHODOLOGY: Survey forms and user interactions were monitored once a week for twelve weeks during the fall 1997 semester. The project was based on a 1989 New Mexico State University study and used Kantor's Branching Analysis to measure responses. RESULT: 80% of reported sought journal articles were found successfully. Along with journal usage data, the library obtained demographic and behavioral information. DISCUSSION AND CONCLUSIONS: Journals are the library's most used resource and, even as more electronic journals are offered, print journals continue to make up the majority of the collection. Several factors highlighted the need to study journal availability. User groups indicated that finding journals was problematic, and internal statistics showed people requesting interlibrary loans for owned items. The study looked at success rates, time, and ease of finding journals. A variety of reasons contributed to not finding journals. While overall user reports indicated relatively high success rate and satisfaction, there were problems to be addressed. As the library proceeds in redesigning both the physical space and electronic presence, the collected data have provided valuable direction.  相似文献   
978.
The paper considers how attributes and skills fundamental to the information profession may be applied to the development and management of Web-based services and resources. It also looks at the need for the acquisition of new skills as part of a continuing professional development programme. The report considers the changing role of the Webmaster and the implications this might have in terms of the role of information professionals. To offer a practical example, from within the healthcare sector, the article goes on to describe the development of BMA Library Online. This is the BMA Library's own suite of Web-based information services and resources for personal members, institutional members and staff. The library's own Web team has been responsible for the development and maintenance of BMA Library Online. To conclude, the paper looks forward to future possibilities for information professionals as Web developers and at how this might be influenced by changes in the Webmaster role. It is crucial that skills and expertise are shared as the roles that go to make up a Webmaster or Webmaster team continue to merge and evolve, and with the possible wider distribution of provision of Web content within organizations.  相似文献   
979.
We examined the supposition that swimmers may exhibit an imbalance in bilateral arm power output during simulated swimming exercise. Ten competitive front crawl swimmers (5 males, 5 females; age 20.5+/-2.3 years; height 1.74+/-0.09 m; body mass 72.0+/-16.7 kg; 400 m freestyle swim time 278+/-20.5 s; mean +/- s) performed four incremental (10 W x min(-1)) swim ramp tests on a computer-interfaced biokinetic swim bench ergometer. External power output from each arm was measured continuously to exhaustion. The results showed that, throughout the course of the simulated swim, external power output clearly favoured the left arm (F1,9 = 12.5, P= 0.006). This was especially evident in the final 30 s to exhaustion, when 54.0+/-3.87% of external power output was derived from the left arm versus 46.0+/-3.87% from the right arm. The disparity in external power output was further highlighted when the participants were grouped into unilateral and bilateral breathers. Unilateral breathers (n = 5) produced 57.1+/-2.62% of external power output from the left armversus 42.9+/-2.62% from the right arm (P= 0.001). Bilateral breathers (n = 5) exhibited a more balanced external power output of 51.0+/-1.82% from the left arm and 49.0+/-1.82% from the right arm (P = 0.177). Evidence of power imbalance in the simulated swimming stroke may have important implications for optimizing swim performance. The observed power imbalance may be reduced when a bilateral breathing technique is adopted.  相似文献   
980.
To determine the daily energy requirements of professional soccer players during a competitive season, we measured total energy expenditure in seven players (age 22.1+/-1.9 years, height 1.75+/-0.05 m, mass 69.8+/-4.7 kg; mean +/- s) using the doubly labelled water method. Energy intake was simultaneously estimated from 7 day self-report dietary records. Mean total energy expenditure and energy intake were 14.8+/-1.7 MJ x day(-1) (3532+/-408 kcal x day(-1)) and 13.0+/-2.4 MJ x day(-1) (3113+/-581 kcal x day(-1)), respectively. Although there was a significant difference between total energy expenditure and energy intake (P < 0.01), there was a strong relationship between the two (r= 0.893, P< 0.01). Basal metabolic rate and recommended energy allowance calculated from the Recommended Dietary Allowances for the Japanese were 7.0+/-0.3 MJ x day(-1) (1683+/-81 kcal x day(-1)) and 15.6+/-0.8 MJ x day(-1) (3739+/-180 kcal x day(-1)), respectively. A physical activity level (total energy expenditure/ basal metabolic rate) of 2.11+/-0.30 indicated that, during the competitive season, professional soccer players undertake much routine physical activity, similar to that of competitive athletes during moderate training. Energy intake estimated using dietary records was under-reported, suggesting that its calculation from these data does not predict energy expenditure in soccer players.  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