全文获取类型
收费全文 | 33648篇 |
免费 | 142篇 |
国内免费 | 266篇 |
专业分类
系统科学 | 491篇 |
丛书文集 | 624篇 |
教育与普及 | 94篇 |
理论与方法论 | 162篇 |
现状及发展 | 14215篇 |
研究方法 | 1322篇 |
综合类 | 16442篇 |
自然研究 | 706篇 |
出版年
2013年 | 376篇 |
2012年 | 681篇 |
2011年 | 1402篇 |
2010年 | 461篇 |
2009年 | 410篇 |
2008年 | 756篇 |
2007年 | 860篇 |
2006年 | 883篇 |
2005年 | 818篇 |
2004年 | 753篇 |
2003年 | 560篇 |
2002年 | 566篇 |
2001年 | 866篇 |
2000年 | 888篇 |
1999年 | 640篇 |
1992年 | 520篇 |
1991年 | 433篇 |
1990年 | 456篇 |
1989年 | 425篇 |
1988年 | 389篇 |
1987年 | 419篇 |
1986年 | 427篇 |
1985年 | 541篇 |
1984年 | 424篇 |
1983年 | 358篇 |
1982年 | 352篇 |
1981年 | 352篇 |
1980年 | 402篇 |
1979年 | 982篇 |
1978年 | 787篇 |
1977年 | 784篇 |
1976年 | 571篇 |
1975年 | 688篇 |
1974年 | 992篇 |
1973年 | 813篇 |
1972年 | 835篇 |
1971年 | 949篇 |
1970年 | 1147篇 |
1969年 | 943篇 |
1968年 | 909篇 |
1967年 | 953篇 |
1966年 | 794篇 |
1965年 | 643篇 |
1964年 | 211篇 |
1959年 | 329篇 |
1958年 | 528篇 |
1957年 | 398篇 |
1956年 | 312篇 |
1955年 | 328篇 |
1954年 | 309篇 |
排序方式: 共有10000条查询结果,搜索用时 515 毫秒
261.
262.
263.
264.
The DNP fibres gamma-irradiated under aerobic condition showed a reduction of their diameter, while no remarkable changes were observed in the DNP fibres irradiated under hypoxic condition by scanning electron microscopy. 相似文献
265.
266.
Summary The C-11 proton of an aprophine possessing a C-1,2 methylenedioxy group falls relatively upfield between 7.47 and 7.86. Additionally, the i.c.s. for the two protons of the methylenedioxy group is large (4–12 Hz). The presence of a methylenedioxy at C-3,4 in a phenanthrene alkaloid also results in an upfield shift ( 8.95–9.00) of the C-5 proton.This project was supported by NIH research grant No. HL-12971, awarded by the National Heart and Lung Institute, PHS/DHEW. 相似文献
267.
V. R. Osório E Castro M. G. P. Vale A. P. Carvalho 《Cellular and molecular life sciences : CMLS》1976,32(4):424-426
Summary The effect of the antibiotic X-537A on the phosphorylated ATPase (EP) was investigated. The results show that X-537A depresses the level of EP which is dependent on the Ca2+ gradient, while the Ca2+-independent EP is not affected.
Acknowledgments. This work was supported by grants from the Instituto de Alta Cultura of the Portuguese Ministry of Education (No. CB/2) and the Calouste Gulbenkian Foundation. 相似文献
268.
G. M. Hanozet M. Simonetta D. Barisio A. Guerritore 《Cellular and molecular life sciences : CMLS》1976,32(10):1246-1249
Summary The three enzymes of ethanol metabolism alcohol dehydrogenase, aldehyde dehydrogenase and acetyl-CoA synthetase in the obligate aerobic yeastRhodotorula gracilis are repressed by glucose and induced by C2 metabolic fuels with a regulatory pattern indicating a correlation in the control mechanisms. To try an identification of the molecular signals involved in the transmission of the inducing stimulus, experiments were carried out by blocking with 2 mM pyrazole the ethanol acetaldehyde metabolic step. Results indicate that ethanol is not specifically required as a molecular signal for induction.This work was supported by a grant from the Italian Consiglio Nazionale delle Ricerche. 相似文献
269.
Summary Adenylate kinase activity of intact mitochondria is strongly inhibited by Ap5A, i.e.p
1,p
5-Di (adenosine-5-) pentaphosphate, whereas oxidative phosphorylation is not affected. Therefore, Ap5A is a useful tool to distinguish between oxidative and non oxidative ATP generating reactions.Acknowledgment. The generous support of Prof. Dr.Walther Lamprecht is gratefully acknowledged. J. L. thanks the Stipendienfonds des Verbandes der Chemische Industrie for a scholarship. 相似文献
270.
Summary Tryptic treatment of muscle thick filaments reveals the underlying backbones of aggregatedl-meromyosin as a coli of 3 secondary filaments (helical repeat 130 nm) each in turn a coli of a 3 finer ones. 相似文献