全文获取类型
收费全文 | 40680篇 |
免费 | 102篇 |
国内免费 | 216篇 |
专业分类
系统科学 | 184篇 |
丛书文集 | 647篇 |
教育与普及 | 100篇 |
理论与方法论 | 147篇 |
现状及发展 | 19179篇 |
研究方法 | 1539篇 |
综合类 | 18668篇 |
自然研究 | 534篇 |
出版年
2013年 | 331篇 |
2012年 | 517篇 |
2011年 | 1026篇 |
2008年 | 673篇 |
2007年 | 737篇 |
2006年 | 721篇 |
2005年 | 712篇 |
2004年 | 757篇 |
2003年 | 687篇 |
2002年 | 683篇 |
2001年 | 1184篇 |
2000年 | 1125篇 |
1999年 | 780篇 |
1994年 | 386篇 |
1992年 | 744篇 |
1991年 | 551篇 |
1990年 | 648篇 |
1989年 | 624篇 |
1988年 | 608篇 |
1987年 | 701篇 |
1986年 | 651篇 |
1985年 | 818篇 |
1984年 | 632篇 |
1983年 | 552篇 |
1982年 | 484篇 |
1981年 | 509篇 |
1980年 | 636篇 |
1979年 | 1250篇 |
1978年 | 1070篇 |
1977年 | 1021篇 |
1976年 | 842篇 |
1975年 | 915篇 |
1974年 | 1185篇 |
1973年 | 1069篇 |
1972年 | 1106篇 |
1971年 | 1272篇 |
1970年 | 1541篇 |
1969年 | 1233篇 |
1968年 | 1215篇 |
1967年 | 1163篇 |
1966年 | 1017篇 |
1965年 | 708篇 |
1964年 | 263篇 |
1959年 | 389篇 |
1958年 | 697篇 |
1957年 | 507篇 |
1956年 | 439篇 |
1955年 | 412篇 |
1954年 | 405篇 |
1948年 | 308篇 |
排序方式: 共有10000条查询结果,搜索用时 797 毫秒
251.
Summary The secondary disease in PF1 strain combination depends upon the immune status of both partners. It is most clearly expressed if both donors and recipients are immunologically crippled by thymectomy and irradiation. Conspicuous reduction in the immune potential of parental parabionts induced by thymectomy and irradiation displayed their marked incidence of parabiotic death. 相似文献
252.
M. Schwab J. Haas S. Abdo M. R. Ahuja G. Kollinger A. Anders F. Anders 《Cellular and molecular life sciences : CMLS》1978,34(6):780-782
Summary Specific genotypes of the xiphophorine fish develop neoplasms following treatment with N-methyl-N-nitrosourea or X-rays. Several of these neoplasms can be related to the presence of specific chromosomes. The implications of these findings are discussed.Supported by Deutsche Forschungsgemeinschaft through Sonderforschungsbereich 103 Zellenergetik und Zelldifferenzierung, Marburg (projects C 9 and C 10), and by Justus-Liebig-Universität Giessen. We are indebted to Prof. K. Frese, Veterinär-Pathologisches Institut, Giessen and Dr H. D. Mennel, Pathologisches Institut, Freiburg, for their help in the classification of neoplasms. We furthermore thank K. Klinke for breeding the fish. Dedicated to Prof. C. Kosswig on the occasion of his 75th birthday.The paper contains parts of the dissertations of S. Abdo, J. Haas and G. Kollinger.supported by the Egypt ministry of education. 相似文献
253.
H. Kemona J. Prokopowicz N. Wotosowicz 《Cellular and molecular life sciences : CMLS》1978,34(2):257-257
Summary It has been shown that there is a higher count of blood platelets and thrombopoietic activity of plasma in women than men. 相似文献
254.
M. Tardy B. Rolland J. Bardakdjian P. Gonnard 《Cellular and molecular life sciences : CMLS》1978,34(9):1137-1138
Summary -(4-chlorophenyl)-GABA, a GABA mimetic compound, acts as an inhibitor of GABA metabolism in both synaptosomal and extrasynaptosomal compartments. It has no significant action on GABA or Glu uptake by synaptosomes. 相似文献
255.
Summary Pentobarbital concentrations of 10–100 M selectively inhibited the noradrenaline release evoked by activation of the nicotinic receptors on the terminals sympathetic nerves of the rabbit heart. Higher concentrations also decreased the noradrenaline release induced by KCl or by electrical stimulation of the nerve axons.This paper is dedicated to Professor Dr. G. Malorny on the occasion of his 65th birthday.Acknowledgment: We thank Mrs G. Thielecke for technical assistance. 相似文献
256.
Summary The effects of L-glutamic acid and of some glutamate analogues have been studied on the central nervous system of the snailHeobania vermiculata, using conventional electrophysiological techniques. The glutamate H-response had the mean equilibrium value of-(57±4) mV and was associated with a Cl– conductance change. The D-response to glutamate application showed an involvement of sodium ions. Aspartate was agonist of glutamate action and displayed similar equilibrium value of the H-response, whereas quisqualate H-response was non-invertible.The authors wish to express their thanks to Prof. A. Curatolo for his continual interest and advice, and to Dr J. Stinnakre for the criticism of the text. 相似文献
257.
Summary 7 monoterpenes, -pinene, -pinene, myrcene, p-cymene, limonene, neral and geranial, were identified together with n-undecane in the scent scales ofP. melete, and also, together with considerable amounts of linalool, in the scent scales ofP. napi. Content ratio of neral to geranial inP. melete ranged from 0.77 to 1.04, and that inP. napi from 1.84 to 2.43. The present chemotaxonomic approach shows the 2 species ofPieris to be distinct.The authors thank Dr T. Yushima (National Institute of Agricultural Science, Japan) for supplying the references 3 and 4. 相似文献
258.
M. Marušić Nikša Allegretti F. Čulo 《Cellular and molecular life sciences : CMLS》1978,34(10):1355-1356
Summary Cyclophosphamide given to rats 2 or 5 days after an injection of Yoshida ascites sarcoma cured approximately the same proportion of animals, but the resistance to a subsequent tumor challenge was found only in rats treated with the drug 5 days after tumor injection. 相似文献
259.
The effect ofγ-irradiation on soil enzyme stability 总被引:1,自引:0,他引:1
R. G. Burns Lindsay J. Gregory G. Lethbridge N. M. Pettit 《Cellular and molecular life sciences : CMLS》1978,34(3):301-302
Summary Arylsulphatase, -1,3 glucanase, phosphatase and urease responded differently to -irradiation (5–50 Mrad) in air-dried and moist soils. In all instances phosphatase was the most stable. The variability between enzymes may be due to inherent biochemical and stuctural characteristics or to their location within the soil microenvironment.Supported by a grant from the NERC. 相似文献
260.
Large-scale purification of hepatitis B surface antigen using affinity chromatography 总被引:2,自引:0,他引:2
A. R. Neurath A. M. Prince J. Giacalone 《Cellular and molecular life sciences : CMLS》1978,34(3):414-415
Summary Large-scale purification of hepatitis B surface antigen, applicable to the preparation of potential vaccines for prevention of hepatitis B, is described. The method involves the following steps: precipitation of serum with polyethylene glycol 6000, affinity chromatography on concanavalin A-Sepharose and on -aminononyl-Sepharose, and isopycnic centrifugation.This study was supported by grant 09011 from the National Heart, Lung and Blood Institute. We thank Dr. B. Hollinger for testing HBsAg samples by a complement fixation test. 相似文献