全文获取类型
收费全文 | 12110篇 |
免费 | 98篇 |
国内免费 | 70篇 |
专业分类
系统科学 | 52篇 |
丛书文集 | 108篇 |
教育与普及 | 17篇 |
理论与方法论 | 19篇 |
现状及发展 | 5354篇 |
研究方法 | 600篇 |
综合类 | 6019篇 |
自然研究 | 109篇 |
出版年
2013年 | 95篇 |
2012年 | 189篇 |
2011年 | 303篇 |
2010年 | 75篇 |
2008年 | 226篇 |
2007年 | 267篇 |
2006年 | 217篇 |
2005年 | 227篇 |
2004年 | 339篇 |
2003年 | 192篇 |
2002年 | 201篇 |
2001年 | 439篇 |
2000年 | 407篇 |
1999年 | 289篇 |
1992年 | 216篇 |
1991年 | 188篇 |
1990年 | 173篇 |
1989年 | 153篇 |
1988年 | 165篇 |
1987年 | 186篇 |
1986年 | 167篇 |
1985年 | 242篇 |
1984年 | 204篇 |
1983年 | 166篇 |
1982年 | 140篇 |
1981年 | 162篇 |
1980年 | 171篇 |
1979年 | 407篇 |
1978年 | 330篇 |
1977年 | 282篇 |
1976年 | 246篇 |
1975年 | 267篇 |
1974年 | 341篇 |
1973年 | 275篇 |
1972年 | 302篇 |
1971年 | 354篇 |
1970年 | 452篇 |
1969年 | 340篇 |
1968年 | 326篇 |
1967年 | 330篇 |
1966年 | 303篇 |
1965年 | 236篇 |
1964年 | 74篇 |
1959年 | 91篇 |
1958年 | 172篇 |
1957年 | 123篇 |
1956年 | 111篇 |
1955年 | 87篇 |
1954年 | 118篇 |
1948年 | 77篇 |
排序方式: 共有10000条查询结果,搜索用时 359 毫秒
101.
I. J. Miller N. K. McCallum C. M. Kirk B. M. Peake 《Cellular and molecular life sciences : CMLS》1982,38(2):230-231
Summary The free radical oxidation of 1 and 6-tetrahydrocannabinol has been examined by spin trapping techniques and intermediates that would lead to cannabinol have been trapped. The 1st step in the oxidation of 1-THC involves the removal of 3-H, while for 6-THC, either 2-H or 5-H. Intermediates were isolated which could be pyrolysed to the diene and cannabinol. 相似文献
102.
I. Yuli S. Incerpi P. Luly M. Shinitzky 《Cellular and molecular life sciences : CMLS》1982,38(9):1114-1115
Summary Basal and insulin-stimulated transport of 2-deoxy glucose and of -aminoisobutyric acid in mouse 3T3 fibroblasts were modulated by increasing the lipid microviscosity of the cell plasma membrane. The kinetics indicate that the insulin effect is induced either by recruitment of new transport carriers or by reduction of the translocation activation energy.This investigation was supported by grant No.5-R01-CA-27471-02, awarded by the National Cancer Institute, Department of Health, Education and Welfare. 相似文献
103.
Summary Leydig cell nuclear area and
5-3-hydroxysteroid dehydrogenase activity were increased in the testis ofBufo melanostictus 2 days after a single short-term cold exposure. Both parameters returned to normal values 4 days later. 相似文献
104.
C Radanyi G Redeuilh E Eigenmann M C Lebeau N Massol C Secco E E Baulieu H Richard-Foy 《Comptes rendus des séances de l'Académie des sciences. Série D, Sciences naturelles》1979,288(2):255-258
The antibodies against estrogen receptor were obtained after injecting Rabbits with a cytoplasmic receptor fraction isolated from Calf uterus. The estrogen receptor was partially proteolysed by the action of trypsin and subsequently purified by affinity chromatography (purification 4,000 to 10,000 fold, to a purity of 5-20%). The affinity of the antibody for the proteolysed receptor is KD approximately 1 nM and serum titres have reached values of approximately 50 nM. The values remained constant after the third injection. Preliminary results indicate that the antibody has approximately the same affinity for "native" cytoplasmic estrogen receptor from Calf uterus, as well as for the "trypsinized" forms of estrogen receptor isolated from Calf uterine cytosol and Hen oviduct nuclei. 相似文献
105.
S André N Farjaudon C Pareyre E Séguin 《Comptes rendus des séances de l'Académie des sciences. Série D, Sciences naturelles》1979,288(14):1095-1097
Comparing cytotoxicity of tubulosine and of six newly synthesized pseudo-tubulosines in the Allium test, we have characterized all the current features of protein inhibition. Nevertheless cytotoxicity of the six pseudotubulosines is much weaker. Furthermore, "floating poles anaphasis", a disturbance characteristic of the action of tubulosine, has been found with a lesser intensity with the other compounds. 相似文献
106.
Effects were examined of atropine, diazepam, pethidene, promethazine, scopolamine, omnopon and papaverine on basal and noradrenaline-stimulated lipolysis in rat isolated fat cells and on rat adipose tissue cyclic AMP phosphodiesterase activity. Papaverine at high concentration (1 mM) inhibited both basal and hormone-stimulated lipolysis, whereas diazepam enhanced basal lipolysis. At a 'clinical dose', omnopon increased both basal and noradrenaline-stimulated lipolysis. Adipose tissue cAMP phosphodiesterase activity was strongly inhibited by 1 mM diazepam, papaverine, promethazine and omnopon (280 microgram ml-1). Lack of enhancement of lipolysis by the established cAMP phosphodiesterase antagonist papaverine, is compatible with simultaneous inhibition also of adipose adenyl cyclase. Diazepam-stimulated lipolysis is compatible with its phosphodiesterase inhibitory activity. It is proposed that papaverine-containing omnopon may offer some survival advantages during surgical stress by facilitating a caloric supply. 相似文献
107.
Field stimulation of isolated, spirally-cut cervix from day-22 pregnant rats produced contractions which could be inhibited by tetrodotoxin or hyoscine and potentiated by propranolol. The rat cervix would appear to receive both cholinergic and noradrenergic innervations whose transmitters activate muscarinic cholinoceptors and beta-adrenoceptors respectively. 相似文献
108.
Suppressor cell induction can be demonstrated during antigen specific blastogenesis by using the same methods which have shown induction of suppressor cells by Con A. Since suppressor cells are rapidly generated during antigen specific blastogenesis, they must regulate the final level of blastogenesis induced during the seven day in vitro incubation. 相似文献
109.
Summary Viable cerebellar perikarya of mixed cell type obtained from 7–9-day-old rats were maintained in monolayer culture for up to 12 days. During this time extensive neurite formation and outgrowth occurred. The large majority of the cells developing in culture were tentatively identified as granule neurons. This identification was based on the large number isolated from the starting tissue, and the cells general morphological features in culture such as perikaryal and nuclear size, the bipolar nature of neurite extension, and their migratory behaviour.D.N. Currie was supported by a grant from Hoechst Pharmaceuticals, Ld, U.K.J.C. was supported by an S.R.C. Grant to S.P.R. RoseThe authors would like to thank Kathleen Tear for excellent technical assistance and members of the Brain Research Group for helpful discussions. 相似文献
110.