全文获取类型
收费全文 | 30115篇 |
免费 | 79篇 |
国内免费 | 110篇 |
专业分类
系统科学 | 118篇 |
丛书文集 | 275篇 |
教育与普及 | 89篇 |
理论与方法论 | 102篇 |
现状及发展 | 12611篇 |
研究方法 | 1170篇 |
综合类 | 15481篇 |
自然研究 | 458篇 |
出版年
2013年 | 257篇 |
2012年 | 374篇 |
2011年 | 831篇 |
2008年 | 458篇 |
2007年 | 550篇 |
2006年 | 538篇 |
2005年 | 526篇 |
2004年 | 551篇 |
2003年 | 509篇 |
2002年 | 514篇 |
2001年 | 1019篇 |
2000年 | 1019篇 |
1999年 | 597篇 |
1994年 | 343篇 |
1992年 | 532篇 |
1991年 | 452篇 |
1990年 | 507篇 |
1989年 | 501篇 |
1988年 | 482篇 |
1987年 | 483篇 |
1986年 | 519篇 |
1985年 | 594篇 |
1984年 | 450篇 |
1983年 | 446篇 |
1982年 | 375篇 |
1981年 | 363篇 |
1980年 | 414篇 |
1979年 | 947篇 |
1978年 | 754篇 |
1977年 | 689篇 |
1976年 | 576篇 |
1975年 | 673篇 |
1974年 | 901篇 |
1973年 | 739篇 |
1972年 | 747篇 |
1971年 | 973篇 |
1970年 | 1136篇 |
1969年 | 882篇 |
1968年 | 907篇 |
1967年 | 765篇 |
1966年 | 730篇 |
1965年 | 515篇 |
1964年 | 164篇 |
1959年 | 284篇 |
1958年 | 511篇 |
1957年 | 391篇 |
1956年 | 293篇 |
1955年 | 297篇 |
1954年 | 284篇 |
1948年 | 246篇 |
排序方式: 共有10000条查询结果,搜索用时 515 毫秒
201.
H. Watanabe J. A. Menzies J. C. K. Loo 《Cellular and molecular life sciences : CMLS》1981,37(8):883-884
Summary Isonicotinic acid hydrazide (isoniazid) was shown to react readily with 17-ethinyl-17-hydroxyestr-4-en-3-one (norethindrone) to form the isonicotinyl hydrazone of the steroid under conditions likely to exist in the stomach. The hydrazone was detected in guinea-pig, but not rat, plasma following its oral administration. Rat liver tissue metabolized the compound more rapidly than guinea-pig liver in vitro which probably accounts for the failure to detect the hydrazone in rat plasma. 相似文献
202.
D. Sabourault Françoise Bauché Y. Giudicelli J. Nordmann R. Nordmann 《Cellular and molecular life sciences : CMLS》1981,37(3):227-229
Summary After 3 weeks of continuous ethanol intoxication by inhalation, the maximal number and affinity of the -and -receptors of rat heart were unchanged. These data indicate that adrenergic receptor disturbances are not involved in the mechanism of chronic ethanol-induced triglyceride deposition in the heart.Acknowledgments. This work was supported by grants from the Institut National de la Santé et de la Recherche Médicale. We wish to thank Mr M. Clément for skilled technical assistance in performing chronic ethanol inhalation treatments. 相似文献
203.
B. Lejczak H. Starzemska P. Mastalerz 《Cellular and molecular life sciences : CMLS》1981,37(5):461-462
Summary Analogues of glutamic acid, -methylglutamic acid and glutamine in which the -or -COOH groups are replaced by PO3H2 or P(O)(OH3)OH functions competitively inhibit rat liver glutamine synthetase. The K1 values are comparable to or lower than KM for L-glutamate.This study was supported by grant R.1.9. 相似文献
204.
R. Lenzhofer C. Cerni I. Fröhlich J. Prager H. Pointner 《Cellular and molecular life sciences : CMLS》1981,37(9):1015-1017
Summary The influence of somatostatin on tumor cell growth was studied in vivo in mice (sarcoma 180 ascites tumor and Lewis lung tumor) and in vitro on nontransformed and polyoma-transformed cell lines. 4 or 20 g/100 g of cyclic somatostatin and 4 g/100 g of linear protamin Zn-bound somatostatin were injected s.c. twice daily in the in vivo study. Cyclic somatostatin (1, 4 or 10 g/ml) was added twice daily to the cell cultures. Somatostatin administration influenced neither the survival of animals nor the growth rate of cultured cell lines. *** DIRECT SUPPORT *** A2025117 00011 相似文献
205.
Summary Thymidylate synthetase (methylenetetrahydrofolate: 2-deoxyuridine-5-monophosphate C-methyltransferase; EC 2.1.1.45) from neonatal mouse liver has been purified 714-fold by affinity chromatography on aminohexylsepharose bound 10-methyl-5,8-dideazafolate.Supported by grant CA22754, awarded by the National Cancer Institute, DHEW. 相似文献
206.
Summary A simple device is described, which permits us to quantify several parameters of spontaneous behaviour of small animals. Using this device with mice we obtained statistically satisfactory results, showing a strong genetic influence on the behavioural characteristics tested.We wish to thank Mr R. Laplace for technical help, Mr J. P. Arnould for electronic work as well as I.N.S.E.R.M.-SCR 3. 相似文献
207.
H. Takeuchi T. Morimasa M. Matsumoto 《Cellular and molecular life sciences : CMLS》1977,33(7):938-939
Summary Several peptides were separated from-chymotrypsin-treated physalaemin by high voltage paper electrophoresis, and inhibition of the excitability of a molluscan giant neurone (tonically autoactive neurone) by the tripeptide, Lys-Phe-Tyr, was demonstrated.We thank Dr Sadaaki Iwanaga of Osaka University and Dr Atsuo Inoue of Daiichi Pharmaceutical CO for their helpful advice and the donation of the tripeptide (Lys-Phe-Tyr). 相似文献
208.
For the identification of a peptidyl principle inducing sexual agglutination in the yeast, 2 supposed hexapeptides (1a, b) were synthesized by the conventional method. The 1a (H-Arg-Gly-Pro-Phe-Pro-Ile-OH) revealed complete identity with the natural peptide in TLC, MS and biological property on agglutination. The 1b showed the sexual agglutinability in the same degree as 1a, though distinct differences were observed in the chemical data. Both 1a and 1b had a strong bitter taste. 相似文献
209.
The ontogeny and localization of the gamma crystallins in Discoglossus pictus lens development has been determined. Using antibody specific for amphibian gamma crystallins in the immunofluorescence technique, it was found that gamma crystallins first appear in primary lens fibre cells in the lens rudiment, and continue to be restricted to the fibre area as lens development progresses. Thus the role of gamma crystallins as indicators of a differentiated state remains constant in amphibian evolution, having been demonstrated in the most archaic anuran superfamily, as well as in others more recently evolved. 相似文献
210.
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