全文获取类型
收费全文 | 31355篇 |
免费 | 43篇 |
国内免费 | 69篇 |
专业分类
系统科学 | 154篇 |
丛书文集 | 717篇 |
教育与普及 | 79篇 |
理论与方法论 | 200篇 |
现状及发展 | 13501篇 |
研究方法 | 1347篇 |
综合类 | 15100篇 |
自然研究 | 369篇 |
出版年
2013年 | 174篇 |
2012年 | 419篇 |
2011年 | 832篇 |
2010年 | 180篇 |
2008年 | 552篇 |
2007年 | 539篇 |
2006年 | 596篇 |
2005年 | 591篇 |
2004年 | 517篇 |
2003年 | 567篇 |
2002年 | 566篇 |
2001年 | 978篇 |
2000年 | 896篇 |
1999年 | 598篇 |
1992年 | 569篇 |
1991年 | 462篇 |
1990年 | 486篇 |
1989年 | 489篇 |
1988年 | 490篇 |
1987年 | 498篇 |
1986年 | 490篇 |
1985年 | 599篇 |
1984年 | 494篇 |
1983年 | 404篇 |
1982年 | 346篇 |
1981年 | 340篇 |
1980年 | 448篇 |
1979年 | 967篇 |
1978年 | 855篇 |
1977年 | 846篇 |
1976年 | 580篇 |
1975年 | 630篇 |
1974年 | 931篇 |
1973年 | 785篇 |
1972年 | 804篇 |
1971年 | 1017篇 |
1970年 | 1339篇 |
1969年 | 1004篇 |
1968年 | 945篇 |
1967年 | 988篇 |
1966年 | 829篇 |
1965年 | 609篇 |
1964年 | 148篇 |
1959年 | 360篇 |
1958年 | 522篇 |
1957年 | 443篇 |
1956年 | 366篇 |
1955年 | 316篇 |
1954年 | 363篇 |
1948年 | 193篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
181.
182.
The spontaneous locomotor activity of the laboratory mouse is significantly depressed by the ingestion of deuterium oxide. The response, which is reversible, is a retilinear one with up to 70% reduction in activity with the administration of 25% heavy water. 相似文献
183.
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
184.
Summary The effect of dipyridamole on platelet phospholipids has been studied. After the platelet incubation with dipyridamole, a 38% reduction in the concentration of the sphingomyelin and a 21% increase in phosphatidyl choline were produced. 相似文献
185.
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
186.
A. J. Rein D. D. Saperstein S. H. Pines P. C. Radlick 《Cellular and molecular life sciences : CMLS》1976,32(10):1352-1354
Summary Using Raman spectroscopy, we demonstrate that low levels of -carotene, lycopene, and xanthophyll give rise to resonance enhanced bands in blood plasma. These results explain the significance of previously unidentified spectral maxima which have been related to the state of health of the blood donor. 相似文献
187.
J. Damas 《Cellular and molecular life sciences : CMLS》1976,32(6):725-727
Summary In normal rats, prostaglandin F2 is a potent vasoconstrictor. The corresponding systemic hypertension is progressively attenuated by tachyphylaxis, revealing a longlasting fall of blood pressure. Tachyphylaxis is accelerated by previous injection of arachidonic acid and bradykinin. The vasodepressive activity of PGF2 is inhibited by indomethacin.
Nous remercions vivement le docteurPike (Upjohn, Kalamazoo) qui nous a fourni gracieusement ces prostaglandines. 相似文献
Nous remercions vivement le docteurPike (Upjohn, Kalamazoo) qui nous a fourni gracieusement ces prostaglandines. 相似文献
188.
R. G. G. Andersson H. J. Arnqvist L. Lundholm 《Cellular and molecular life sciences : CMLS》1976,32(5):601-602
Summary The incorporation of leucice-14C into protein in bovine mesenteric arteries was augmented by cyclic GMP (10–3
M) and decreased by cyclic AMP (10–3
M). There was no effect of 5 AMP (10–3
M). The phosphodiesterase inhibiting drugs theophylline (10–3
M) and papaverine (5×10–5 g/ml) both decreased the leucine-14C incorporation.We are indebted to Mrs.Lena Burlin for hear assistance. Finacial support has been provided by the Swedish State Medical Research Council (No. 04X-101X-4498). 相似文献
189.
H. N. Nigg J. A. Svoboda M. J. Thompson S. R. Dutky J. N. Kaplanis W. E. Robbins 《Cellular and molecular life sciences : CMLS》1976,32(4):438-439
Summary An ecdysone 20-hydroxylase enzyme system that converts -ecdysone to 20-hydroxyecdysone was prepared from the midgut of the tobacco hornworm prepupa. This partially purified enzyme is NADPH dependent and is localized in the mitochondrial fraction of the midgut tissue. 相似文献
190.