全文获取类型
收费全文 | 28867篇 |
免费 | 80篇 |
国内免费 | 158篇 |
专业分类
系统科学 | 139篇 |
丛书文集 | 499篇 |
教育与普及 | 42篇 |
理论与方法论 | 100篇 |
现状及发展 | 13451篇 |
研究方法 | 1279篇 |
综合类 | 13199篇 |
自然研究 | 396篇 |
出版年
2013年 | 269篇 |
2012年 | 411篇 |
2011年 | 809篇 |
2010年 | 168篇 |
2008年 | 523篇 |
2007年 | 576篇 |
2006年 | 576篇 |
2005年 | 535篇 |
2004年 | 539篇 |
2003年 | 498篇 |
2002年 | 500篇 |
2001年 | 936篇 |
2000年 | 865篇 |
1999年 | 615篇 |
1992年 | 595篇 |
1991年 | 414篇 |
1990年 | 486篇 |
1989年 | 494篇 |
1988年 | 460篇 |
1987年 | 546篇 |
1986年 | 474篇 |
1985年 | 596篇 |
1984年 | 484篇 |
1983年 | 364篇 |
1982年 | 340篇 |
1981年 | 367篇 |
1980年 | 462篇 |
1979年 | 889篇 |
1978年 | 757篇 |
1977年 | 740篇 |
1976年 | 611篇 |
1975年 | 632篇 |
1974年 | 845篇 |
1973年 | 756篇 |
1972年 | 779篇 |
1971年 | 840篇 |
1970年 | 1073篇 |
1969年 | 813篇 |
1968年 | 820篇 |
1967年 | 795篇 |
1966年 | 681篇 |
1965年 | 472篇 |
1964年 | 156篇 |
1959年 | 249篇 |
1958年 | 440篇 |
1957年 | 292篇 |
1956年 | 259篇 |
1955年 | 246篇 |
1954年 | 239篇 |
1948年 | 162篇 |
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
141.
M. D. Adams J. T. Earnhardt B. R. Martin L. S. Harris W. L. Dewey R. K. Razdan 《Cellular and molecular life sciences : CMLS》1977,33(9):1204-1205
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
142.
Cell lineage analysis of germ cells of Drosophila melanogaster. 总被引:1,自引:0,他引:1
143.
Proton pump coupled to cytochrome c oxidase in mitochondria. 总被引:1,自引:0,他引:1
M K Wikstrom 《Nature》1977,266(5599):271-273
144.
M. B. Castillo M. D. Gonzalez G. Burton C. P. Lantos A. Roldán 《Cellular and molecular life sciences : CMLS》1983,39(6):617-618
Summary A dissociation between inhibition of RNA synthesis and cell lysis was observed when thymocytes of adrenalectomized rats were incubated with high concentrations of pregn-4-ene-11-ol-3, 20-dione and pregna-1,4-diene-11-ol-3,20-dione. In contrast, no dissociation of these effects was found with the typical glucocorticoids cortisol and corticosterone, nor with their 1,4-diene analogs under the same conditions.Acknowledgments. This work was supported by grants from the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina to the Instituto de Biologia y Medicina Experimental and the Programa de Regulación Hormonal y Metabólica as well as by financial help from the Secretaría de Ciencia y Tecnología. 相似文献
145.
M. Szmitkowski 《Cellular and molecular life sciences : CMLS》1983,39(7):771-772
Summary Normal and chloroform-extracted human sera, fractionated by Sephadex column chromatography, have been tested for inhibitory activity on granulocyte-macrophage (GM) colony formation. It was found that this activity is connected with lipoproteins (inhibitors of granulocyte-macrophage colony stimulating factor) and low molecular weight substances (7000; 13,000) which can act as specific polypeptide chalones. 相似文献
146.
J. J. Cazzulo Berta M. Franke de Cazzulo 《Cellular and molecular life sciences : CMLS》1982,38(11):1335-1337
Summary Cell-free extracts ofTrypanosoma cruzi contain proteolytic activity able to degrade endogenous substrates. The activity was maximal at pH 3 to 4, had an optimal temperature of 65°C, and was strongly inhibited by N--p-tosyl-L-lysine chloromethyl ketone.This investigation received financial support from the UNDP/World Bank/WHO Special Programme for Research and Training in Tropical Diseases, the Fundación Julio Cherny, and the Ministerio de Salud Pública y Medio Ambiente de la República Argentina. The authors gratefully acknowledge the technical assistance of Mr Esteban Bontempi. 相似文献
147.
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
148.
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
149.
M. Karydis 《Cellular and molecular life sciences : CMLS》1982,38(10):1185-1186
Summary The importance of phytoplankton in stabilizing oil-in-water emulsion and affecting hydrocarbon distribution in the sea was studied by using marine diatoms. All microalgae tested increased emulsion stability and favored the presence of polycyclic aromatics in the sea water. 相似文献
150.
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