全文获取类型
收费全文 | 26872篇 |
免费 | 73篇 |
国内免费 | 120篇 |
专业分类
系统科学 | 106篇 |
丛书文集 | 196篇 |
教育与普及 | 71篇 |
理论与方法论 | 79篇 |
现状及发展 | 11684篇 |
研究方法 | 1184篇 |
综合类 | 13402篇 |
自然研究 | 343篇 |
出版年
2013年 | 211篇 |
2012年 | 404篇 |
2011年 | 700篇 |
2010年 | 177篇 |
2008年 | 479篇 |
2007年 | 553篇 |
2006年 | 521篇 |
2005年 | 530篇 |
2004年 | 496篇 |
2003年 | 521篇 |
2002年 | 460篇 |
2001年 | 896篇 |
2000年 | 882篇 |
1999年 | 563篇 |
1994年 | 349篇 |
1992年 | 537篇 |
1991年 | 398篇 |
1990年 | 468篇 |
1989年 | 429篇 |
1988年 | 420篇 |
1987年 | 469篇 |
1986年 | 431篇 |
1985年 | 576篇 |
1984年 | 416篇 |
1983年 | 380篇 |
1982年 | 388篇 |
1981年 | 337篇 |
1980年 | 354篇 |
1979年 | 911篇 |
1978年 | 684篇 |
1977年 | 628篇 |
1976年 | 551篇 |
1975年 | 590篇 |
1974年 | 694篇 |
1973年 | 653篇 |
1972年 | 630篇 |
1971年 | 708篇 |
1970年 | 921篇 |
1969年 | 742篇 |
1968年 | 756篇 |
1967年 | 718篇 |
1966年 | 658篇 |
1965年 | 463篇 |
1959年 | 241篇 |
1958年 | 426篇 |
1957年 | 276篇 |
1956年 | 254篇 |
1955年 | 230篇 |
1954年 | 208篇 |
1948年 | 196篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
191.
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
192.
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
193.
Summary 5-bromo-2-deoxyuridine (BUdR) removal from liver DNA in newborn and young adult rats has been demonstrated: it forms the basis of a reliable method to measure DNA repair in tissues provided with detectable DNA synthetic activity.This work was supported by a grant from Consiglio Nazionale delle Ricerche, Rome, and Donazione Teston, Bologna, Italy. 相似文献
194.
Summary 2 populations of rat fleas,Xenopsylla astia, collected from (A) Bombay and (B) Trivandrum, were found to differ in chromosome number as follows; (A) 2n=10 in both sexes; (B) 2n=18 (male) and 20 (female). Preliminary observations have further shown that the 2 populations differ in certain morphological characters and that their reciprocal hybrids are sterile in the male and partially sterile in the female sex.Acknowledgments. We wish to express our deepest gratitude to Dr Robert E. Lewis, Professor of Entomology, Iowa State University, USA, for confirming our identification of the 2 samples of rat fleas. We are indebted to Dr N.R. Prabhoo, Reader in Zoology, University of Kerala, Trivandrum, for his advice and helpful suggestions. We are also indebted to Prof. K.M. Alexander, for encouragement and providing facilities. Financial help of the University Grants Commission, India, to one of us (C.T.) is also gratefully acknowledged. 相似文献
195.
B. Stankiewicz-Choroszucha J. Górski 《Cellular and molecular life sciences : CMLS》1978,34(3):357-358
Summary It was shown in the rat that mobilization of intramuscular triglyceride during exercise is controlled by the adrenergic system.Acknowledgments. The work was supported by the Polish Academy of Sciences, grant No. 10.4.2.01.3.2. 相似文献
196.
B. Jazdowska-Zagrodzińska B. Matuszewski 《Cellular and molecular life sciences : CMLS》1978,34(6):777-778
Summary Lamellar structures in oogonial and spermatogonial cells of gall midges were found to form a complicated system of intranuclear compartments inside which all heteropycnotic chromosomes present in the germ-line cells of these insects are located. In this way, the heteropycnotic S-chromosomes are separated by the nuclear lamellae from the remaining, decondensed chromosomes (E-chromosomes) of the interphase germ-line nucleus.This investigation was supported in part under Contract DPKBN/52/76-II.1.3.10. with the Polish Academy of Sciences. 相似文献
197.
Summary The seedling growth ofBrassica campestris var.varuna, has been studied, as affected by water-stress and gibberellin treatments. A boost in the net GA response due to water-stress, has been observed. Thus presence of GA can overcome the water-stress effects.Publication No. 26 from Dept of Biosciences, Himachal Pradesh University, Simla. Authors are grateful to CSIR, New Delhi, for JRF to SB. 相似文献
198.
Summary A 2-dimensional thin-layer method has been developed for the separation on cellulose of adenine and guanine derivatives. Using incubated rat cerebral cortex slices it was shown that noradrenaline and acetylcholine stirnulated cAMP and cGMP production respectively but glutamate and -aminobutyric acid stimulated production of both cyclic nucleotides. 相似文献
199.
Z. Ben-Ishay F. Reichert S. Sharon 《Cellular and molecular life sciences : CMLS》1978,34(10):1369-1370
Summary Eradication of replicating bone marrow cells of rat by means of combined administration of single doses of hydroxyurea and vinblastin is followed within 9–10 h by an inflow of lymphoid cells of extramedullary origin in the range of 13,200,000/femur. The rat bone marrow with a high content of lymphoid cells was previously shown to be concentrated in stem cells. The factor(s) which convey the information of decrease of replicating marrow cells to extramedullary sites is at present unknown.Acknowledgment. This study was supported by a grant from the Chief Scientist Office, Ministry of Health, Israel.Hydroxyurea for this investigation was given as a gift by the Squibb Institute of Medical Research, Princeton, N.J. USA, to which the authors are indebted. 相似文献
200.
Summary A relatively safe and simple procedure was developed for the induction of hepatomas in the rat by the s.c. administration of powdered 3-methyl-p-dimethylaminoazobenzene. 相似文献