全文获取类型
收费全文 | 28311篇 |
免费 | 68篇 |
国内免费 | 83篇 |
专业分类
系统科学 | 129篇 |
丛书文集 | 284篇 |
教育与普及 | 56篇 |
理论与方法论 | 128篇 |
现状及发展 | 11187篇 |
研究方法 | 1264篇 |
综合类 | 14857篇 |
自然研究 | 557篇 |
出版年
2013年 | 257篇 |
2012年 | 427篇 |
2011年 | 987篇 |
2010年 | 183篇 |
2008年 | 505篇 |
2007年 | 563篇 |
2006年 | 580篇 |
2005年 | 559篇 |
2004年 | 546篇 |
2003年 | 491篇 |
2002年 | 486篇 |
2001年 | 973篇 |
2000年 | 949篇 |
1999年 | 592篇 |
1992年 | 532篇 |
1991年 | 420篇 |
1990年 | 443篇 |
1989年 | 464篇 |
1988年 | 446篇 |
1987年 | 427篇 |
1986年 | 432篇 |
1985年 | 551篇 |
1984年 | 434篇 |
1983年 | 355篇 |
1982年 | 332篇 |
1981年 | 306篇 |
1980年 | 350篇 |
1979年 | 843篇 |
1978年 | 648篇 |
1977年 | 630篇 |
1976年 | 539篇 |
1975年 | 614篇 |
1974年 | 823篇 |
1973年 | 682篇 |
1972年 | 715篇 |
1971年 | 845篇 |
1970年 | 1077篇 |
1969年 | 802篇 |
1968年 | 849篇 |
1967年 | 761篇 |
1966年 | 707篇 |
1965年 | 505篇 |
1964年 | 127篇 |
1959年 | 293篇 |
1958年 | 499篇 |
1957年 | 339篇 |
1956年 | 282篇 |
1955年 | 253篇 |
1954年 | 276篇 |
1948年 | 214篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
181.
182.
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
183.
184.
G. D. Ledney H. M. Gelston Jr S. R. Weinberg E. D. Exum 《Cellular and molecular life sciences : CMLS》1982,38(10):1228-1230
Summary Wound trauma-induced survival from radiation may be related to increased mitosis in hematopoietic cells. This is supported by the cell cycle-dependent drug hydroxyurea, which 1. blocked survival of wounded mice injected 2 or 3 days after 900 rad and 2. reduced the number of endogenous CFU-s in wounded mice injected shortly before 700 rad.Supported by the Armed Forces Radiobiology Research Institute, Defense Nuclear Agency, under Research Work Unit MJ00018. Views presented in this paper are those of the authors; no endorsement by the Defense Nuclear Agency has been given or should be inferred.Research was conducted according to the principles enunciated in the Guide for the Care and Use of Laboratory Animals prepared by the Institute of Laboratory Research, National Research Council. 相似文献
185.
Summary The flavoprotein ferredoxin reductase catalyzed the oxidation of styrene to styrene oxide in the presence of NADPH. This reaction was inhibited by the addition of catalase and superoxide dismutase. The addition of the nonheme iron protein ferredoxin partially inhibited styrene oxidation. H2O2 was also able to catalyze this reaction when added to the enzyme in the absence of NADPH.Acknowledgments. This work was supported by C.N.R. (National Research Council), Rome, Italy contract No. 79.03197.04. 相似文献
186.
G. Zamboni E. Perez P. L. Parmeggiani 《Cellular and molecular life sciences : CMLS》1982,38(10):1188-1189
Summary In rats adapted to a 1212 h light-dark (LD) schedule, cyclic AMP concentration in the preoptic region showed a L minimum and D maximum. No significant fluctuations were observed in the parietal cortex.Supported by grant No. 79.01946.04 awarded by the National Research Council (CNR), Rome, Italy. 相似文献
187.
Captopril (SQ 14,225): In vitro and in vivo influence on the proliferative response of rat lymphocytes 总被引:1,自引:0,他引:1
Lise Binderup E. Bramm E. Arrigoni-Martelli 《Cellular and molecular life sciences : CMLS》1982,38(3):399-401
Summary Captopril in vitro (50–500 g/ml) increased3H-TdR incorporation in unstimulated and mitogen-stimulated cultures of rat lymphocytes. Unseparated spleen and lymph node cells of rats orally treated with captopril (50 mg/kg/day×4) showed decreased basal and mitogen stimulated3H-TdR incorporation. The removal of macrophages abrogated this inhibitory effect. Leucine aminopeptidase activity of macrophages was reduced — in vivo and in vitro — by captopril.Acknowledgments. The authors thank the Squibb Institute for Medical Research for the gift of Captopril. The excellent technical assistance of Ms B. Hasselriis, Ms B. Rumler and Ms E. Greve Petersen is gratefully acknowledged. 相似文献
188.
The identification of ecdysterone (20-hydroxyecdysone) in 3 species of molluscs (Gastropoda: Pulmonata) 总被引:1,自引:0,他引:1
Summary Ecdysterone has been identified in the schistosomiasis vectorBiomphalaria glabrata Say and inHelix aspersa Müller as well as inLymmaea stagnalis L. by chromatography, bioassay, radioimmunoassay, derivatization and by mass spectroscopy. Analysis of the food, faeces and hepatopancreas suggest that the sterol is derived from the diet. The probable function of ecdysterone in relation to calcification of the shell is discussed in this paper.We wish to thank Professor P. Karlson and Dr J. Koolman (Phillips University, Marburg-Lahn, FRG) for providing facilities for RIA. The initial study was begun at the University of Sussex and continued at the Courtauld Institute of Biochemistry, Middlesex Hospital Medical School, London, while D.L.W. was supported by the Ministry of Overseas Development. London and the Medical Research Council of Great Britain (grant G974/525/T). We thank Mr P. Mellon for the mass spectrum and Dr G.B. Russell for his interest in the earlier part of this study. We also thank Professor E. Scherer and Dr Q. Uwe (University of Essen, FRG) for their help in the irradiation ofL. stagnalis.Gauss Str. 82, D-4630 Bochum 5 (Federal Republic of Germany). Research results usingL. stagnalis were submitted for the Philips Europa Wettbewerb für junge Forscher und Erfinder (1979) in a thesis entitled Zur Frage der Existenz von Steroiden und Gonadoliberin bei der Grossen Schlammschnecke (Lymmaea stagnalis L.): ein Beitrag zur Evolution der Insekten- und Wirbeltierhormone. 相似文献
189.
Summary The defense secretion of soldiers ofReticulitermes lucifugus has been shown to contain, predominantly, (R)-(–)-(E,E)-geranyllinalool together with germacrene A and -farnesene.This report covers part of a collaborative study with J.-L. Clément, Lab. d'Evolution, Université P. et M. Curie, Paris, to whom we are grateful for supplies of material and discussions. We also thank Dr O.T. Jones for collections ofReticulitermes lucifugus. 相似文献
190.
V. Lattanzio V. V. Bianco D. Lafiandra 《Cellular and molecular life sciences : CMLS》1982,38(7):789-790
Summary A HPLC assay for L-Dopa, convicine, and vicine in broad-bean extracts has been developed. The distribution of these compounds in the different organs of the plant has been studied, especially in the seeds, where their presence may cause favism if the beans are used as food.Work supported by C.N.R. through Progetto Finalizzato Miglioramento delle produzioni vegetali per fini alimentari ed industriali mediante interventi genetici. Sottogrogetto leguminose da granella. Paper No. 200. 相似文献