全文获取类型
收费全文 | 32263篇 |
免费 | 136篇 |
国内免费 | 296篇 |
专业分类
系统科学 | 431篇 |
丛书文集 | 538篇 |
教育与普及 | 130篇 |
理论与方法论 | 105篇 |
现状及发展 | 13042篇 |
研究方法 | 1178篇 |
综合类 | 16618篇 |
自然研究 | 653篇 |
出版年
2013年 | 353篇 |
2012年 | 615篇 |
2011年 | 1261篇 |
2010年 | 433篇 |
2009年 | 420篇 |
2008年 | 730篇 |
2007年 | 831篇 |
2006年 | 815篇 |
2005年 | 749篇 |
2004年 | 661篇 |
2003年 | 542篇 |
2002年 | 545篇 |
2001年 | 858篇 |
2000年 | 923篇 |
1999年 | 638篇 |
1994年 | 341篇 |
1992年 | 490篇 |
1991年 | 419篇 |
1990年 | 472篇 |
1989年 | 439篇 |
1988年 | 429篇 |
1987年 | 462篇 |
1986年 | 449篇 |
1985年 | 542篇 |
1984年 | 435篇 |
1983年 | 381篇 |
1982年 | 354篇 |
1981年 | 342篇 |
1980年 | 405篇 |
1979年 | 879篇 |
1978年 | 721篇 |
1977年 | 700篇 |
1976年 | 533篇 |
1975年 | 658篇 |
1974年 | 844篇 |
1973年 | 737篇 |
1972年 | 734篇 |
1971年 | 910篇 |
1970年 | 1027篇 |
1969年 | 886篇 |
1968年 | 881篇 |
1967年 | 848篇 |
1966年 | 755篇 |
1965年 | 551篇 |
1959年 | 304篇 |
1958年 | 524篇 |
1957年 | 407篇 |
1956年 | 321篇 |
1955年 | 335篇 |
1954年 | 313篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
181.
In vivo studies indicated that the primary effects of E. coli endotoxin on hepatic clearance of sulfobromophthalein were at the excretory level. Newborns were more sensitive to the LPS than older animals. 相似文献
182.
J. Kapitola H. Dlouhá Dr. J. Křeček J. Zicha 《Cellular and molecular life sciences : CMLS》1977,33(12):1615-1616
Summary Neurohypophyseal blood flow increases in water-deprived rats. This increase is independent of vasopressin release, since it occurs even in rats with hereditary defect of hypothalamic vasopressin synthesis.Acknowledgment. The technical assistance of D. Vilimovská is acknowledged. 相似文献
183.
H Meves Y Pichon 《Comptes rendus des séances de l'Académie des sciences. Série D, Sciences naturelles》1977,284(14):1325-1328
Most of the effects of 4-aminopyridine on the potassium conductance of the giant axon of the Squid can be explained in terms of a simple model based on the physicochemical properties of the molecule and what is known about the structure of the potassium "channels". 相似文献
184.
Summary The binding of coumarin to serum proteins of the rat has been demonstrated. Of the total bound coumarin (37% of injected dose), 36% was bound to the slow and fast 1 globulins, 11% to the post albumins, 10% to globulin and 9% to albumin. 相似文献
185.
A. R. Jones Carole Murcott D. H. Milton Jennifer Flynn 《Cellular and molecular life sciences : CMLS》1977,33(7):934-935
Summary The male antifertility agent 1-amino-3-chloropropan-2-ol (ACP,I) has been shown to be metabolized to-chlorohydrin (III) and metabolites of-chlorohydrin. This accounts for the similar antifertility and renal toxicity effects of both compounds. 相似文献
186.
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
187.
H. -J. Hess J. S. Bindra J. W. Constantine W. Elger O. Loge E. Schillinger W. Losert 《Cellular and molecular life sciences : CMLS》1977,33(8):1076-1077
Summary N-methanesulfonyl 16-phenoxy--tetranor PGE2 is a prostaglandin analog which is markedly more tissue selective than PGE2. This compound is 10–30 times more potent than PGE2 in animal models which are considered relevant to antifertility effects in humans. In pharmacological tests which are believed to be predictive for side effects in humans, the compound has potency either equal to or less than that of PGE2. 相似文献
188.
Transposable genetic elements as agents of gene instability and chromosomal rearrangements. 总被引:31,自引:0,他引:31
Transposable genetic elements in prokaryotes and eukaryotes, when inserted at a given locus, can control expression of the locus and cause large scale rearrangements of adjacent DNA sequences. Striking similarities in genetic behaviour between the two groups of elements have led to the proposal of a molecular model of eukaryotic controlling elements, and to suggestions about the part such elements may play in evolution and differentiation. 相似文献
189.
190.
Summary Using the Fell technique of organ culture of cartilage in a chemically defined medium, it has been shown that prostaglandin A1 at a concentration of 25 g/ml caused chondrocyte death in chick embryonic limb rudiments. An equimolar concentration of PGE2 was not toxic to the cells.Acknowledgments. We are grateful for the support of C. J. K. by the Medical Research Council and of D. L. G. by the Arthritis and Rheumatism Council for Research. Our thanks are due to Dame Honor Fell, F. R. S. for invaluable advice and guidance, to Dr J. Pike (Upjohn Co.) for supplies of prostaglandin A1, and to Dr Sylvia Fitton-Jackson for the gift of culture medium. 相似文献