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   38939篇
  免费   68篇
  国内免费   105篇
系统科学   184篇
丛书文集   779篇
教育与普及   99篇
理论与方法论   239篇
现状及发展   17196篇
研究方法   1545篇
综合类   18560篇
自然研究   510篇
  2013年   246篇
  2012年   524篇
  2011年   1065篇
  2010年   232篇
  2008年   653篇
  2007年   671篇
  2006年   707篇
  2005年   718篇
  2004年   642篇
  2003年   694篇
  2002年   667篇
  2001年   1149篇
  2000年   1055篇
  1999年   731篇
  1992年   696篇
  1991年   558篇
  1990年   602篇
  1989年   596篇
  1988年   599篇
  1987年   612篇
  1986年   578篇
  1985年   737篇
  1984年   584篇
  1983年   494篇
  1982年   444篇
  1981年   434篇
  1980年   572篇
  1979年   1214篇
  1978年   1031篇
  1977年   1020篇
  1976年   758篇
  1975年   823篇
  1974年   1127篇
  1973年   1008篇
  1972年   1066篇
  1971年   1256篇
  1970年   1631篇
  1969年   1259篇
  1968年   1212篇
  1967年   1240篇
  1966年   1060篇
  1965年   755篇
  1964年   191篇
  1959年   446篇
  1958年   682篇
  1957年   542篇
  1956年   455篇
  1955年   396篇
  1954年   424篇
  1948年   269篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
Humoral immune reactions to heat shock proteins (hsp) from microorganisms are one aspect of microbial infections in humans. The production of antibodies which are specific to epitopes present on procaryotic hsp leads also to the appearance of cross-reactive serum antibodies in the host organism that react with human hsp. This article discusses the consequences of such autoreactive antibodies for the host in context with the development of immune tolerance and autoimmune diseases, especially rheumatoid arthritis (RA), and in experimental animal models for arthritis such as adjuvant arthritis in rats. On the basis of epitope cross-reactivity between hsp and other host proteins, a hypothesis is presented for the development of autoimmune disease following the production of hsp-specific antibodies.  相似文献   
13.
14.
15.
This paper assesses the information content of two survey indicators for consumption developments in the near future for eight European countries in the period 1985–1998. Empirical work on this topic typically focuses on consumer confidence, the perceptions of buyers of consumption goods. This paper examines whether perceptions of sellers of consumption goods, measured by retail trade surveys, may also improve short‐term monitoring of consumption. We find that both consumer confidence and retailer confidence embody valuable information, when analysed in isolation. For France, Italy and Spain we conclude that adding retail confidence does not improve the indicator model once consumer confidence has been included. For the UK the reverse case is obtained. For the remaining four countries we show that combining consumer sentiment and retail trade confidence into a composite indicator leads to optimal results. Our results suggest that incorporating information from retail trade surveys may offer significant benefits for the analysis of short‐term prospects of consumption. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   
16.
17.
A linear regression model with random walk coefficients is extended to allow for linear restrictions between the coefficients to be satisfied at each point in time. Estimation in this model is shown to be no more involved than estimation in the standard model. It is also demonstrated how, after a slight modification to the testing problem, classical test procedures may be applied to the problem of testing for such restrictions. The performance of the Lagrange Multiplier test for a variety of different restrictions is then investigated via simulation. An empirical application involving testing for homogeneity in a random walk coefficient version of the AIDS model is given.  相似文献   
18.
We recently reported on a linkage study within a Quarter Horse lineage segregating hyperkalaemic periodic paralysis (HYPP), an autosomal dominant condition showing potassium-induced attacks of skeletal muscle paralysis. HYPP co-segregated with the equine adult skeletal muscle sodium channel alpha subunit gene, the same gene that causes human HYPP. We now describe the Phe to Leu mutation in transmembrane domain IVS3 which courses the horse disease. This represents the first application of molecular genetics to an important horse disease, and the data will provide an opportunity for control or eradication of this condition.  相似文献   
19.
Summary Immunohistochemistry revealed an Ig-A-like substance on the luminal surface of the pineal follicles and in the parafollicular layer. This substance was observed around 1 week of age and disappeared by 8 weeks at the time when the transformation of the follicular pattern leads to an adult-type pineal tissue.  相似文献   
20.
Summary The tissue specificity of lactate dehydrogenase (EC 1.1.1.27) in brain and eye of the teleostPhallichthys amates was examined by acrylamide gel electrophoresis. It is suggested that subunit association is a function of gene product accessibility superimposed upon genetic restriction of assembly.  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