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   27742篇
  免费   137篇
  国内免费   295篇
系统科学   440篇
丛书文集   409篇
教育与普及   89篇
理论与方法论   90篇
现状及发展   11102篇
研究方法   1119篇
综合类   14291篇
自然研究   634篇
  2013年   307篇
  2012年   625篇
  2011年   1239篇
  2010年   424篇
  2009年   401篇
  2008年   682篇
  2007年   805篇
  2006年   803篇
  2005年   721篇
  2004年   547篇
  2003年   470篇
  2002年   513篇
  2001年   823篇
  2000年   850篇
  1999年   595篇
  1992年   470篇
  1991年   401篇
  1990年   422篇
  1989年   386篇
  1988年   374篇
  1987年   405篇
  1986年   372篇
  1985年   460篇
  1984年   430篇
  1983年   303篇
  1982年   321篇
  1981年   313篇
  1980年   342篇
  1979年   803篇
  1978年   646篇
  1977年   589篇
  1976年   521篇
  1975年   557篇
  1974年   682篇
  1973年   572篇
  1972年   570篇
  1971年   684篇
  1970年   813篇
  1969年   639篇
  1968年   682篇
  1967年   695篇
  1966年   612篇
  1965年   461篇
  1964年   200篇
  1959年   238篇
  1958年   387篇
  1957年   272篇
  1956年   220篇
  1955年   231篇
  1954年   204篇
排序方式: 共有10000条查询结果,搜索用时 0 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.
Summary The effects of time and various doses of testosterone on the responsiveness of lactate dehydrogenase of pituitary of 7-, 38- and 78-week-old rats were studied. The activity of the enzyme increases in 78-week-old rats. Castration decreases the enzyme activity at all ages. Maximum increase in the enzyme activity is seen with 50 and 100 g of testosterone 4 h after administration of hormone to castrated rats. No further time and dose-dependent effect is observed. The magnitude of increase for the enzyme is higher at the age of 38 weeks and decreases in 78-week-old rats.To whom all correspondence should be addressed. The authors are grateful to Professor M.S. Kanungo, Biochemistry Laboratory, Department of Zoology, Banaras Hindu University for the suggestions and encouragement. K.V.G. thanks the PL-480 for a research fellowship.  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.
A L Newsome  J P Harley 《Experientia》1978,34(12):1567-1568
Daily administration of vitamin D3 (75,000 IU/kg b. wt) for 7 days accelerated Trichinella spiralis cyst calcification in rats with a 14-week-old infection. When disodium ethane-1-hydroxy-1, 1-diphosphonate (EHDP) was administered (50 mg/kg b. wt) from 2 days before until 2 days after vitamin D3 treatment, cyst calcification was inhibited. Thus, the ability to inhibit E. spiralis calcification has demonstrated for the first time.  相似文献   
95.
96.
A minute amount of serotonin injected in the nodose ganglion circulation area develops abrupt myosis and general electrocortical synchronization activity in "encéphale isolé" Cat preparation. This hypnogenic effect of serotonin can still be reproduced after transection of vago-aortic nerves caudally to the nodose ganglia. The same injections become ineffective after rostral transection of the same pathway. These results suggest that serotonin may trigger some signs of sleep through peripheric nervous elements in which are probably localized in the nodose ganglia.  相似文献   
97.
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   
98.
M T Lin  A Chandra  Y F Chern  B L Tsay 《Experientia》1980,36(9):1077-1078
At ambient temperatures (Ta) of both 8 and 22 degrees C, intraventricular administration of TRH (10-80 microgram) produced a dose-dependent hypothermia in rats. The hypothermia was due to both decreased metabolic heat production and cutaneous vasodilatation. In contrast, at 30 degrees C Ta, TRH increased metabolic heat production (due to behavioral excitation) and led to hyperthermia.  相似文献   
99.
Summary Silver-staining has been used to identify the nucleolus organizer regions (NORs) in the bharal. These show homology with sheep, goat, cattle and aoudad. The association of the NORs on both telomeres of chromosome 3 results in a ring chromosome.  相似文献   
100.
Summary The hemolymph volume ofHeliothis zea larvae was determined by the amaranth dye method and found to vary from 28 to 288 l. It averaged 30.6% of b.wt, a value comparable to that obtained with C14 inulin. Amaranth became evenly distributed in the hemocoele in 3–5 min.  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