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   16083篇
  免费   41篇
  国内免费   61篇
系统科学   46篇
丛书文集   98篇
教育与普及   34篇
理论与方法论   44篇
现状及发展   7066篇
研究方法   742篇
综合类   7976篇
自然研究   179篇
  2013年   137篇
  2012年   264篇
  2011年   415篇
  2010年   104篇
  2008年   254篇
  2007年   309篇
  2006年   285篇
  2005年   300篇
  2004年   306篇
  2003年   276篇
  2002年   275篇
  2001年   525篇
  2000年   472篇
  1999年   347篇
  1992年   317篇
  1991年   238篇
  1990年   266篇
  1989年   243篇
  1988年   256篇
  1987年   275篇
  1986年   207篇
  1985年   325篇
  1984年   245篇
  1983年   213篇
  1982年   218篇
  1981年   181篇
  1980年   225篇
  1979年   536篇
  1978年   409篇
  1977年   385篇
  1976年   350篇
  1975年   397篇
  1974年   437篇
  1973年   416篇
  1972年   448篇
  1971年   478篇
  1970年   605篇
  1969年   477篇
  1968年   507篇
  1967年   467篇
  1966年   444篇
  1965年   296篇
  1964年   86篇
  1959年   142篇
  1958年   265篇
  1957年   177篇
  1956年   155篇
  1955年   140篇
  1954年   123篇
  1948年   108篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
Summary Rats given aluminium hydroxide after cold-restraint stress but before the post-stress delay period, ulcerated significantly less severely and less frequently than rats given the drug before cold-restraint stress or those given water at either time period. Both aluminium hydroxide treated groups exhibited less ulceration than non-drug groups. These data suggest profound parasympathetic and hence, gastric acid, involvement in restraint delay-induced ulceration in rats.  相似文献   
102.
Summary The activity of (Na++K+)-ATPase and acetylcholine esterase were folloed in rat brain cerebral cortex, caudate, thalamus, hippocampus and medulla after i.v. administration of physostigmine. Both enzymes were found to be inhibited in a dose-dependent manner. The most pronounced inhibition of (Na++K+)-ATPase was found in caudate. where the highest activity of acetylcholine esterase is found.These studies were supported by a grant from the Union of Science of Republic Serbia, No. 40404-14.  相似文献   
103.
Summary Analogues of glutamic acid, -methylglutamic acid and glutamine in which the -or -COOH groups are replaced by PO3H2 or P(O)(OH3)OH functions competitively inhibit rat liver glutamine synthetase. The K1 values are comparable to or lower than KM for L-glutamate.This study was supported by grant R.1.9.  相似文献   
104.
Summary The influence of somatostatin on tumor cell growth was studied in vivo in mice (sarcoma 180 ascites tumor and Lewis lung tumor) and in vitro on nontransformed and polyoma-transformed cell lines. 4 or 20 g/100 g of cyclic somatostatin and 4 g/100 g of linear protamin Zn-bound somatostatin were injected s.c. twice daily in the in vivo study. Cyclic somatostatin (1, 4 or 10 g/ml) was added twice daily to the cell cultures. Somatostatin administration influenced neither the survival of animals nor the growth rate of cultured cell lines. *** DIRECT SUPPORT *** A2025117 00011  相似文献   
105.
Summary Food ingestion of male guinea-pigs was restricted to 10 g/day. Total carnitine content of liver of the underfed animals fell to 3.75 moles per liver (46.1% of control). Serum level of total carnitine was 35.0 nmoles/ml (64.4%) in the underfed animals while they developed high ketonemia, 384.2 nmoles/ml (555.2%). In restricted animals the carnitine levels also decreased in the muscles.  相似文献   
106.
107.
Summary Goat placental lactogen was partially purified from a medium collected after placental tissue incubation. The data obtained by disc electrophoresis and isoelectric focusing experiments, as well as by means of radioreceptor assay methods, provide evidence of the similarity between the goat and ovine placental lactogen.The careful technical assistance of L. Tichovská is gratefuly acknowledged.  相似文献   
108.
The use of the stable isotopes 6 and 7 of lithium, and detection with the ionic analyser, allow the measurement of unidirectional transepithelial Li-fluxes, between "external" and "internal" solutions which both contain 80% Na and 20% Li. Efflux was found to be bigger than influx. An important lag-phase on the curve, reveals the interference of a Li-compartment, with a high capacity, in the epithelium itself.  相似文献   
109.
Summary The binding of coumarin to serum proteins of the rat has been demonstrated. Of the total bound coumarin (37% of injected dose), 36% was bound to the slow and fast 1 globulins, 11% to the post albumins, 10% to globulin and 9% to albumin.  相似文献   
110.
Summary Abnormal-8-tetrahydrocannabidiol (ABN-8-THC) failed to elicit central nervous system and cardiovascular effects in laboratory animals. Abnormal-cannabidiol (ABN-CBD) was also devoid of overt behavioral effects but produced marked hypotension with only slight bradycardia in anesthesized dogs.Acknowledgment. This work was supported by NIDA (grant No. DA-00574-01 and DA-00490) and Virginia Heart Society (grant No. RR-05697)  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