全文获取类型
收费全文 | 9450篇 |
免费 | 131篇 |
国内免费 | 161篇 |
专业分类
系统科学 | 107篇 |
丛书文集 | 123篇 |
教育与普及 | 20篇 |
理论与方法论 | 39篇 |
现状及发展 | 3683篇 |
研究方法 | 452篇 |
综合类 | 5228篇 |
自然研究 | 90篇 |
出版年
2016年 | 67篇 |
2014年 | 84篇 |
2013年 | 78篇 |
2012年 | 143篇 |
2011年 | 253篇 |
2010年 | 88篇 |
2009年 | 82篇 |
2008年 | 191篇 |
2007年 | 218篇 |
2006年 | 184篇 |
2005年 | 192篇 |
2004年 | 320篇 |
2003年 | 288篇 |
2002年 | 426篇 |
2001年 | 496篇 |
2000年 | 417篇 |
1999年 | 302篇 |
1992年 | 133篇 |
1991年 | 135篇 |
1990年 | 113篇 |
1989年 | 106篇 |
1988年 | 115篇 |
1987年 | 129篇 |
1986年 | 123篇 |
1985年 | 169篇 |
1984年 | 133篇 |
1983年 | 103篇 |
1982年 | 95篇 |
1981年 | 124篇 |
1980年 | 120篇 |
1979年 | 269篇 |
1978年 | 216篇 |
1977年 | 202篇 |
1976年 | 156篇 |
1975年 | 170篇 |
1974年 | 229篇 |
1973年 | 182篇 |
1972年 | 209篇 |
1971年 | 227篇 |
1970年 | 300篇 |
1969年 | 226篇 |
1968年 | 201篇 |
1967年 | 222篇 |
1966年 | 199篇 |
1965年 | 158篇 |
1959年 | 54篇 |
1958年 | 105篇 |
1957年 | 81篇 |
1956年 | 77篇 |
1954年 | 74篇 |
排序方式: 共有9742条查询结果,搜索用时 171 毫秒
91.
Summary Autoradiographic, stereological and histological studies have been carried out to determine the origin of muscle fibre splitting which supposedly occurs during muscle hypertrophy. The results obtained clearly indicate that the supposedly split fibres are a transient response probably derived from satellite cells and are not derived from pre-existing fibres by true splitting. Similarly, increases in muscle fibre size are not achieved by recruitment of satellite structures as indicated by lack of myonuclear recruitment.Acknowledgment. This work was carried out with the aid of a grant from the Medical Research Council of Great Britain. The authors are grateful for the excellent technical assistance of Miss H. Caulton, M.J. Wild and M. Fenner. 相似文献
92.
G. Cimino A. Crispino S. De Rosa S. De Stefano G. Sodano 《Cellular and molecular life sciences : CMLS》1981,37(9):924-926
Summary Several high molecular weight polyacetylenes have been isolated from the spongePetrosia ficiformis found in dark caves. These compounds are related to, but different from, the polyacetylenes isolated from the same sponge living in its usual habitat.This work is a part of the Progetto finalizzato per l'Oceanografia e i Fondi Marini, CNR, Roma.The authors thank Mr G. Scognamiglio for the HPLC work, Mr C. Di Pinto for the NMR spectra and Mr G. Villani for the collection of the sponge. 相似文献
93.
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
94.
Incorporation of 32P into adrenal mitochondrial phospholipids (PL) incrased in ACTH-treated rats, but it decreased in diabetics, inspite of the fact that these animals showed adrenal overacity. Since diabetics did not show increased 11 beta-hydroxylation. as opposed to ACTH-treated rats, it is suggested that the stimulation of this enzyme activity by exogenous ACTH is related to an increased turnover of PL at the mitochondrial membrane. The process is impaired in diabetics and prevents the stimulation of 11 beta-hydroxylation. 相似文献
95.
Summary Effects of N6, O2 dibutyryl adenosine 3,5-cyclic monophosphate (db-cAMP) and theophylline (Th) on cultured rat embryonic shields were studied. After addition of db-cAMP to the culture medium, an increase of the weight of explants and of the incidence of the skeletal muscle was observed. Theophylline seems to be ineffective. 相似文献
96.
Summary RIA of ecdysones are made on nymphal extracts ofPisaura mirabilis during the intermoulting cycle. The hormone level is low during exuviation and the greatest part of the intermoulting period but increases notably before and after ecdysis. The main hormonal peak or pre-ecdysial peak is due to -ecdysone, characterized by combined TLC/RIA.Acknowledgment. We wish to thank Dr M. Hirn for his help during the manipulations and J. Britton who has translated the text into English. 相似文献
97.
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
98.
R. K. Raina D. Njoroge J. N. Ng'ang'a B. V. Telang 《Cellular and molecular life sciences : CMLS》1977,33(11):1499-1500
Summary
Naja mossambica pallida venom administered i.v. (300 /kg) produces an initial brief fall in blood pressure, due to a direct myocardial depressant effect, and a sustained fall due to central depressant effect.This study was supported by University of Nairobi research grants (670–376). We also thank Mr E. Njogu for photographic assistance. 相似文献
99.
I. J. Miller N. K. McCallum C. M. Kirk B. M. Peake 《Cellular and molecular life sciences : CMLS》1982,38(2):230-231
Summary The free radical oxidation of 1 and 6-tetrahydrocannabinol has been examined by spin trapping techniques and intermediates that would lead to cannabinol have been trapped. The 1st step in the oxidation of 1-THC involves the removal of 3-H, while for 6-THC, either 2-H or 5-H. Intermediates were isolated which could be pyrolysed to the diene and cannabinol. 相似文献
100.
Summary Leydig cell nuclear area and
5-3-hydroxysteroid dehydrogenase activity were increased in the testis ofBufo melanostictus 2 days after a single short-term cold exposure. Both parameters returned to normal values 4 days later. 相似文献