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   21555篇
  免费   100篇
  国内免费   73篇
系统科学   209篇
丛书文集   127篇
教育与普及   55篇
理论与方法论   142篇
现状及发展   9367篇
研究方法   939篇
综合类   10577篇
自然研究   312篇
  2018年   182篇
  2017年   219篇
  2012年   299篇
  2011年   725篇
  2010年   178篇
  2008年   363篇
  2007年   626篇
  2006年   348篇
  2005年   410篇
  2004年   396篇
  2003年   448篇
  2002年   418篇
  2001年   693篇
  2000年   698篇
  1999年   486篇
  1994年   323篇
  1992年   446篇
  1991年   352篇
  1990年   396篇
  1989年   357篇
  1988年   357篇
  1987年   368篇
  1986年   337篇
  1985年   477篇
  1984年   345篇
  1983年   298篇
  1982年   287篇
  1981年   260篇
  1980年   290篇
  1979年   681篇
  1978年   528篇
  1977年   480篇
  1976年   416篇
  1975年   458篇
  1974年   494篇
  1973年   462篇
  1972年   528篇
  1971年   565篇
  1970年   694篇
  1969年   562篇
  1968年   579篇
  1967年   536篇
  1966年   519篇
  1965年   336篇
  1959年   174篇
  1958年   317篇
  1957年   210篇
  1956年   175篇
  1955年   152篇
  1954年   141篇
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
1.
 从“十四五”保护与发展的生态关系角度,探讨了生态保护与绿色发展的十大生态关系,阐述了生态保护和绿色发展中的一系列有关生态关系的生态智慧及生态技术,并对长江、黄河等流域的生态保护和修复提出了相关建议。  相似文献   
2.
We measure and predict states of Activation and Happiness using a body sensing application connected to smartwatches. Through the sensors of commercially available smartwatches we collect individual mood states and correlate them with body sensing data such as acceleration, heart rate, light level data, and location, through the GPS sensor built into the smartphone connected to the smartwatch. We polled users on the smartwatch for seven weeks four times per day asking for their mood state. We found that both Happiness and Activation are negatively correlated with heart beats and with the levels of light. People tend to be happier when they are moving more intensely and are feeling less activated during weekends. We also found that people with a lower Conscientiousness and Neuroticism and higher Agreeableness tend to be happy more frequently. In addition, more Activation can be predicted by lower Openness to experience and higher Agreeableness and Conscientiousness. Lastly, we find that tracking people’s geographical coordinates might play an important role in predicting Happiness and Activation. The methodology we propose is a first step towards building an automated mood tracking system, to be used for better teamwork and in combination with social network analysis studies.  相似文献   
3.
G protein-coupled receptor (GPCR) signalling is mediated through transactivation-independent signalling pathways or the transactivation of protein tyrosine kinase receptors and the recently reported activation of the serine/threonine kinase receptors, most notably the transforming growth factor-β receptor family. Since the original observation of GPCR transactivation of protein tyrosine kinase receptors, there has been considerable work on the mechanism of transactivation and several pathways are prominent. These pathways include the “triple membrane bypass” pathway and the generation of reactive oxygen species. The recent recognition of GPCR transactivation of serine/threonine kinase receptors enormously broadens the GPCR signalling paradigm. It may be predicted that the transactivation of serine/threonine kinase receptors would have mechanistic similarities with transactivation of tyrosine kinase pathways; however, initial studies suggest that these two transactivation pathways are mechanistically distinct. Important questions are the relative importance of tyrosine and serine/threonine transactivation pathways, the contribution of transactivation to overall GPCR signalling, mechanisms of transactivation and the range of cell types in which this phenomenon occurs. The ultimate significance of transactivation-dependent signalling remains to be defined but it appears to be prominent and if so will represent a new cell signalling frontier.  相似文献   
4.
B S Qiu  C H Cho  C W Ogle 《Experientia》1992,48(4):389-391
Ten-day treatment with nicotine (5, 25 or 50 micrograms/ml drinking water) dose-dependently intensified gastric ulceration induced by cold-restraint, and emptying rate. Stomach contractions produced by graded doses of bethanechol i.v. were elevated further by nicotine treatment. It is suggested that chronic nicotine administration produces hypersensitivity of the gastric muscarinic receptors; stomach hypermotility contributes to the ulcer-worsening action of the alkaloid.  相似文献   
5.
6.
7.
8.
Cholinesterases     
AUGUSTINSSON KB 《Nature》1948,162(4109):194
  相似文献   
9.
10.
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