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   30430篇
  免费   61篇
  国内免费   109篇
系统科学   198篇
丛书文集   387篇
教育与普及   65篇
理论与方法论   116篇
现状及发展   12321篇
研究方法   1362篇
综合类   15559篇
自然研究   592篇
  2013年   274篇
  2012年   460篇
  2011年   1061篇
  2010年   183篇
  2009年   132篇
  2008年   511篇
  2007年   642篇
  2006年   644篇
  2005年   612篇
  2004年   609篇
  2003年   558篇
  2002年   553篇
  2001年   1081篇
  2000年   1052篇
  1999年   630篇
  1992年   578篇
  1991年   464篇
  1990年   515篇
  1989年   498篇
  1988年   461篇
  1987年   483篇
  1986年   514篇
  1985年   553篇
  1984年   481篇
  1983年   423篇
  1982年   345篇
  1981年   354篇
  1980年   411篇
  1979年   963篇
  1978年   756篇
  1977年   738篇
  1976年   566篇
  1975年   642篇
  1974年   918篇
  1973年   765篇
  1972年   742篇
  1971年   951篇
  1970年   1215篇
  1969年   826篇
  1968年   806篇
  1967年   814篇
  1966年   735篇
  1965年   514篇
  1959年   278篇
  1958年   464篇
  1957年   349篇
  1956年   276篇
  1955年   242篇
  1954年   247篇
  1948年   205篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Summary Phenylketonuric squirrels have shown marked inhibition of alkaline phosphatatase in the olfactory lobes and cerebral hemispheres, whereas the Na+-K+-ATPase remained less altered. In the pathogenesis of phenylketonuria inhibition of alkaline phosphatase at the level of Blood-Brain Barrier (BBB), leads transport system to impaired functioning.This work was done in the Department of Zoology, University of Udaipur, Udaipur-313001, India.  相似文献   
92.
The oxygen consumption of "hibernating" ants shows a grouping effect translated by a significant decrease in the level of oxygen consumption as a function of grouping effect. The general relation between oxygen consumption and the living body mass is the same, if the living material belongs to a single animal, or a social community of ants.  相似文献   
93.
D K Bhatt 《Experientia》1978,34(12):1549-1550
Phenylketonuric squirrels have shown marked inhibition of alkaline phosphatase in the olfactory lobes and cerebral hemispheres, whereas the Na+-K+-ATPase remained less altered. In the pathogenesis of phenylketonuria inhibition of alkaline phosphatase at the level of "Blood-Brain Barrier" (BBB), leads transport system to impaired functioning.  相似文献   
94.
In curarized Rabbits whose cervico-thoracic cord has been isolated through C2 and Th12 transections, a pharmacological activation (nialamide-DOPA) disclosed distinct rhythmic efferent activities, locomotor-like bursts in forelimb muscle nerves and "respiratory" discharges in the phrenic nerves: they originate respectively from a cervico-thoracic locomotion generator and from a "respiration" generator; these spinal generators appear to be interconnected with each other.  相似文献   
95.
The spontaneous conversion of mammalian cyclic GMP-dependent protein kinase (G-PK) into modulator-dependent protein kinase (type II) (M-PKII) in the absence of cGMP or histone was observed in vitro. The findings, together with similarity in substrate protein specificity, suggest that M-PKII is the catalytic subunit of mammalian G-PK.  相似文献   
96.
Summary We analyzed inheritance of 5Es-1 alleles inP. leucopus and found them to be co-dominant and segregating from a single autosomal locus, thereby verifying assumptions of Mendelian inheritance imfield data. We also described an allele that is silent in hemolysate, but is active in liver extract.Acknowledgment. Laboratory analysis was partially supported by a grant-in-aid (No. 0171-02-240-76) to Kaufman from the Research Foundation of State University of New York.  相似文献   
97.
Summary -Terthienyl and 5 polyacetylenes were examined for chromosome damaging activity using Syrian hamster cells. None of these naturally occurring compounds induced sister chromatid exchanges and neither -terthienyl nor phenylheptatriyne induced chromosome aberrations.The authors wish to thank the National Science and Engineering Research Council for financial support of this research.  相似文献   
98.
Summary The effects of selected -agonists and -antagonists on theophylline-induced lipolysis were investigate in isolated hamster white fat cells 2-Agonists (tramazoline, clonidine) inhibited theophylline-induced lipolysis while an 2-agonist (methoxamine) was without any effect. The inhibitory effect of 2-agonists was suppressed by yohimbine (2-antagonist), whereas 2-antagonists were inefficient. This result implies that the -adrenergic receptor of hamster fat cells is of the 2-type, although located postsynaptically.Acknowledgments. This work was supported by grants from CNRS (ERA 412) and DGRST (grant No. 787 1078). We thank M. Dauzats for excellent technical assistance. We thank Prof. H. Schmitt for tramazoline and AR-C 239 and for helpful discussion.  相似文献   
99.
Summary Prostaglandin (PG) release was measured from the isolated perfused rabbit heart. The effects of -adrenergic stimulation and blockade suggest that PG synthesis is regulated in part by adrenergic mechanisms.  相似文献   
100.
Summary After 3 weeks of continuous ethanol intoxication by inhalation, the maximal number and affinity of the -and -receptors of rat heart were unchanged. These data indicate that adrenergic receptor disturbances are not involved in the mechanism of chronic ethanol-induced triglyceride deposition in the heart.Acknowledgments. This work was supported by grants from the Institut National de la Santé et de la Recherche Médicale. We wish to thank Mr M. Clément for skilled technical assistance in performing chronic ethanol inhalation treatments.  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