全文获取类型
收费全文 | 3857篇 |
免费 | 124篇 |
国内免费 | 10篇 |
专业分类
化学 | 3138篇 |
晶体学 | 99篇 |
力学 | 171篇 |
数学 | 106篇 |
物理学 | 477篇 |
出版年
2023年 | 25篇 |
2022年 | 47篇 |
2021年 | 54篇 |
2020年 | 72篇 |
2019年 | 92篇 |
2018年 | 96篇 |
2017年 | 73篇 |
2016年 | 126篇 |
2015年 | 90篇 |
2014年 | 170篇 |
2013年 | 423篇 |
2012年 | 262篇 |
2011年 | 230篇 |
2010年 | 144篇 |
2009年 | 136篇 |
2008年 | 223篇 |
2007年 | 216篇 |
2006年 | 157篇 |
2005年 | 159篇 |
2004年 | 150篇 |
2003年 | 131篇 |
2002年 | 107篇 |
2001年 | 41篇 |
2000年 | 43篇 |
1999年 | 34篇 |
1998年 | 21篇 |
1997年 | 24篇 |
1996年 | 41篇 |
1995年 | 25篇 |
1994年 | 30篇 |
1993年 | 30篇 |
1992年 | 27篇 |
1991年 | 24篇 |
1990年 | 38篇 |
1989年 | 30篇 |
1988年 | 25篇 |
1987年 | 29篇 |
1986年 | 28篇 |
1985年 | 37篇 |
1984年 | 39篇 |
1983年 | 29篇 |
1982年 | 26篇 |
1981年 | 24篇 |
1980年 | 23篇 |
1979年 | 18篇 |
1978年 | 13篇 |
1977年 | 21篇 |
1976年 | 16篇 |
1975年 | 18篇 |
1974年 | 9篇 |
排序方式: 共有3991条查询结果,搜索用时 0 毫秒
991.
Ivan E. Dimitrov Ravinder Reddy John S. Leigh 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2000,145(2):302
Intermolecular 129Xe–1H nuclear Overhauser effects and 129Xe longitudinal relaxation time measurements were used to demonstrate that the dipole–dipole coupling is the dominant relaxation mechanism for 129Xe in water, at room temperature. 129Xe–1H cross-relaxation rates were derived to be ςXeH 3.2 ± 0.3 × 10−3 s−1, independent of xenon pressure (in the range of 1–10 bar) and of the presence of oxygen. Corresponding xenon–proton internuclear distances were calculated to be 2.69 ± 0.12 Å. Using the magnitude of the dipole–dipole coupling and the spin density ratio between dissolved xenon and bulk water, it is estimated that 129Xe–1H spin polarization-induced nuclear Overhauser effects would yield little net proton signal enhancement in water. 相似文献
992.
993.
An inexpensive and safer reagent system comprising of PMHS and ZnCl2 has been developed for the selective reduction of carbonyl compounds to corresponding alcohols. 相似文献
994.
Synthesis and Spectral Characterization of Related Substances of Lacidipine,an Antihypertensive Drug
V. V. N. K. V. Prasada Raju Ganta Madhusudhan Reddy Vedantham Ravindra Vijayavitthal T. Mathad P. K. Dubey 《合成通讯》2013,43(12):2137-2145
Five related substances (impurities) were detected in lacidipine bulk drug substance by a simple high-performance liquid chromatographic method (HPLC) and were identified by liquid chromatography–mass spectrometry (LC-MS). These related substances were independently synthesized, characterized, and co-injected with the sample containing impurities. 相似文献
995.
996.
The synthesis of macrolides1 is currently under intensive investigations because of their diverse biological and physiological activities. The recent developments in their synthetic strategies made the task easier for synthesis of several naturally occurring rnacrolides. 相似文献
997.
The synthesis, characterisation and antifeedant activity of some new angular dicoumarins prepared from 2,4-diacetyl resorcinol has been reported. 相似文献
998.
K. Vyas A. Sivalakshmidevi G. Om Reddy 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(12):e572-e573
Lansoprazole, 2‐({[3‐methyl‐4‐(2,2,2‐trifluroethoxy)pyridin‐2‐yl]methyl}sulfinyl)‐1H‐benzimidazole, C16H14F3N3O2S, is an antiulcerative agent. The molecules in the lattice are held together by intermolecular hydrogen bonds between the NH group of benzimidazole and the sulfinyl O atom. 相似文献
999.
Subash C. Jonnalagadda Steven R. Verga Parth D. Patel A. V. Reddy T. Srinivas Patricia M. Scott Venkatram R. Mereddy 《应用有机金属化学》2010,24(4):294-300
Novel synthetic protocols for the synthesis of lipophilic carboranes were developed utilizing two C? C bond forming reactions, namely Baylis–Hillman and enynedioate cycloaddition reactions. Some of these carboranes were converted into further functionalized carboranes via nucleophilic allylic isomerization. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
1000.
An efficient enantiospecific synthesis of R(+)-α-Lipoic acid (1) a prosthetic group and a vital cofactor in -α-keto acids decarboxylation is described. 相似文献