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   13441篇
  免费   201篇
  国内免费   21篇
教育   9390篇
科学研究   1521篇
各国文化   125篇
体育   1148篇
综合类   6篇
文化理论   98篇
信息传播   1375篇
  2021年   139篇
  2020年   195篇
  2019年   268篇
  2018年   368篇
  2017年   351篇
  2016年   357篇
  2015年   238篇
  2014年   315篇
  2013年   2317篇
  2012年   294篇
  2011年   319篇
  2010年   279篇
  2009年   218篇
  2008年   267篇
  2007年   238篇
  2006年   232篇
  2005年   208篇
  2004年   229篇
  2003年   207篇
  2002年   175篇
  2001年   446篇
  2000年   292篇
  1999年   253篇
  1998年   118篇
  1997年   155篇
  1996年   132篇
  1995年   123篇
  1994年   144篇
  1993年   110篇
  1992年   181篇
  1991年   191篇
  1990年   194篇
  1989年   200篇
  1988年   165篇
  1987年   159篇
  1986年   168篇
  1985年   206篇
  1984年   161篇
  1983年   151篇
  1982年   128篇
  1981年   122篇
  1980年   116篇
  1979年   163篇
  1978年   131篇
  1977年   117篇
  1976年   92篇
  1975年   112篇
  1974年   100篇
  1973年   107篇
  1971年   98篇
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
981.
多种原因造成了知识产权担保在发放信贷方面的重要性不如其他财产的担保。原因之一是知识产权具有一些特殊属性,一些潜在贷款人对这种财产属性缺乏了解。另一个原因是对许多知识产权的估价存在困难,相关法律在调整这些法定权利上的担保权益方面也不甚健全。尽管金融机构及其法律顾问已经越来越多地理解了知识产权担保借贷中的诸要素,但以知识产权担保的融资仍处在初期阶段。这是一个无论在法律领域,还是在信贷实践方面都很复杂的问题。立法者在回应专门立法需求以促进其发展方面也行动缓慢。这就进一步增加了用知识产权这种价值可能很大、但寿命又可能很短的财产做担保提供信贷的不确定性。  相似文献   
982.
Synchronous data transmission systems that transmit information over dispersive channels often employ adaptive equalization techniques in the processing of the received signals. Most equalizers presently used in communication systems are of the tapped delay line (TDL) type. In this paper, we propose a class of adaptive equalizers of which the TDL equalizer is a member. Another interesting member of this class is the Laguerre adaptive equalizer which is to be introduced in this paper. The configuration of the Laguerre equalizer is developed. It is found, as shown by the examples, that the Laguerre equalizer is more accurate, and is less sensitive to timing error than the conventional TDL equalizer.  相似文献   
983.
984.
Lymphatic filariasis caused mainly by infection fromWuchereria bancrofti andBrugia malayi remains as the major cause of clinical morbidity in tropical and subtropical countries. Development of vaccine against filarial infection can act as additional measure to the existing therapeutic and vector control methods in the control of this disease. The main hurdles in the development of anti-filarial vaccine are the strict primate specificity ofWuchereria bancrofti, the paucity of parasite material, the diversity of clinical manifestations and their associated complex immune responses, lack of clear understanding on host-parasite interactions and the mechanisms involved in protective immunity. However in the past few years, the information generated in immuno-epidemiological studies, correlated with observations in experimental animals suggests that a filarial vaccine is feasible. Initially live irradiated infective larvae have been successfully used to induce high level of protective immunity in several animal models. Applying diverse strategies, variety of purified or recombinant filarial antigens have been explored for their ability to induce protection in different host-parasite systems. Some of these targeted filarial antigens induced high level of resistance in experimental animals against challenge infections. More focussed studies on thorough characterization of parasitological and immunological changes associated with resistance induced by such candidate protective antigens and on delivery mechanisms and safety aspects will be crucial in their selection for possible use in humans.  相似文献   
985.
超过7000万人感染HIV、2000万人死亡,艾滋病是医学史上最严重的流行病之一.  相似文献   
986.
987.
988.
Poly A RNA status and itsin vitro translation in a rabbit reticulolysate cell free system, were assessed in the skeletal muscle of young boys with Duchenne muscular dystrophy. Compared to normals there is a significant 48% increase in poly A RNA content of dystrophic muscle and its translatability was increased by 56% based on35S methionine incorporation into total protein systhesised. Immunoprecipitation of the translated products with monospecific antibodies showed that there is a 2.6 fold and a 2 fold increase in m and μ calpains respectively. This underlines the importance of both synthetic and degenerative activities in the early pathology in DMD muscle.  相似文献   
989.
In previous work it was established that the U.K. tractor industry was characterised by a high degree of technical change and that this was brought about by a process of more or less continuous incremental innovation. What was lacking was an analysis of how much technical change had been introduced and an indication of the role played by technical change in determining the performance of the U.K. tractor industry internationally. This paper concludes that on the average technical change in the industry had increased by as much as 150 percent during the years 1959–1977, though there is some indication that the rate of change might now be slowing somewhat.In order to determine the relative importance of technical change a method was developed to operationalise the distinction between price and non-price competition as well as the idea of intrinsic (technical) and associative (non-technical) factors as constituents of the latter. Based on cross-sectional data for the year 1978, it has been possible to show that British manufacturers tend to produce moderately priced tractors of low to medium technical sophistication: that German manufacturers produced the most technically sophisticated tractors; that the Italian manufacturers are not generally more sophisticated, technically, than the British producers except with respect to their development of four-wheel drive; and that COMECON-based producers combine a very low price with some degree of technical sophistication. Finally, it has been possible to show that the tractors with the highest sales are among the less sophisticated in each of the power ranges investigated and that new entrants used technical sophistication as an element of their entry strategy. The answer to the question of what allows the market leader to be market leader required the development of measures for associative non-price factors, such as the availability of a dealer network brand loyalty, resale prices of tractor models, etc. By performing a regression analysis on these measures along with previously derived measures of quality-adjusted price and relative technical sophistication it has been possible to show that market leadership is achieved as a result of a balance of a number of factors, the most important of which are the size of the dealer network, warrants cost, advertising, technical sophistication and price.  相似文献   
990.
A diverse sample of doctoral students completed an on-line questionnaire assessing their supervisors' academic, personal and autonomy support and their research self-efficacy. The more task-related help and personal support students received, the more positively they evaluated their supervision. The degree to which supervisors encouraged students to think and act autonomously (autonomy support) was not uniquely associated with students' supervision satisfaction but predicted greater research self-efficacy. A combination of high levels of autonomy and academic support was associated with the highest levels of research self-efficacy, whereas when greater levels of personal support were accompanied by low levels of autonomy support, students reported lower research self-efficacy. These results indicate that effective doctoral supervision involves supporting students to voice and act on their own ideas while simultaneously providing guidance on how to complete research tasks.  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