全文获取类型
收费全文 | 36644篇 |
免费 | 9614篇 |
国内免费 | 1398篇 |
专业分类
化学 | 41737篇 |
晶体学 | 329篇 |
力学 | 540篇 |
数学 | 2175篇 |
物理学 | 2875篇 |
出版年
2023年 | 23篇 |
2022年 | 43篇 |
2021年 | 241篇 |
2020年 | 1284篇 |
2019年 | 2621篇 |
2018年 | 1064篇 |
2017年 | 695篇 |
2016年 | 3470篇 |
2015年 | 3596篇 |
2014年 | 3523篇 |
2013年 | 4193篇 |
2012年 | 3047篇 |
2011年 | 2286篇 |
2010年 | 2941篇 |
2009年 | 2940篇 |
2008年 | 2478篇 |
2007年 | 1814篇 |
2006年 | 1502篇 |
2005年 | 1660篇 |
2004年 | 1466篇 |
2003年 | 1330篇 |
2002年 | 2001篇 |
2001年 | 1373篇 |
2000年 | 1290篇 |
1999年 | 373篇 |
1998年 | 54篇 |
1997年 | 49篇 |
1996年 | 39篇 |
1995年 | 23篇 |
1994年 | 33篇 |
1993年 | 13篇 |
1992年 | 27篇 |
1991年 | 16篇 |
1990年 | 8篇 |
1989年 | 6篇 |
1988年 | 7篇 |
1986年 | 9篇 |
1985年 | 8篇 |
1984年 | 4篇 |
1983年 | 14篇 |
1982年 | 13篇 |
1981年 | 12篇 |
1980年 | 5篇 |
1979年 | 9篇 |
1978年 | 5篇 |
1977年 | 6篇 |
1976年 | 10篇 |
1975年 | 4篇 |
1974年 | 8篇 |
1973年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 218 毫秒
41.
42.
43.
44.
45.
46.
5‐Amino‐4‐methyl‐2‐phenyl‐6‐substitutedfuro[2,3‐d]pyrimidines ( 2a‐c ) were reacted with 2,5‐dimethoxytetrahydrfuran to afford the pyrrolyl derivatives 3a‐c . Compound 3a was chosen as intermediate for the synthesis of poly fused heterocycles incorporated furopyrimidines moiety 4–11 . Some of the synthesized compounds were screened for their antibacterial and antifungal activities. 相似文献
47.
Wen Zhang Hui Huang Yu Ding Margherita Gavagnin Ernesto Mollo Guido Cimino Yue‐Wei Guo 《Helvetica chimica acta》2006,89(4):813-820
Three new polyoxygenated steroids, muricesteroid ( 1 ), and menellsteroids A ( 2 ) and B ( 3 ), were isolated from two species of the South China Sea gorgonian Muricella flexuosa and Menella verrucosa Brundin , respectively. The structures of these new compounds were elucidated on the basis of extensive spectroscopic analysis, chemical methods and comparison with known related compounds. 相似文献
48.
It is proved that the variety of relevant disjunction lattices has the finite embeddability property. It follows that Avron's relevance logic RMI min has a strong form of the finite model property, so it has a solvable deducibility problem. This strengthens Avron's result that RMI min is decidable. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
49.
A.F. Mesquita A.O. Porto G.M. de Lima J.M. Delgado F.S. Lameiras 《Solid State Communications》2005,136(3):133-137
Hexagonal and cubic cadmium selenide were prepared from a chemical route by using cadmium chloride and potassium selenium hydride obtained from reaction of selenium powder and potassium boron hydride. The product obtained was thermally treated under argon flux at 300, 500 and 600 °C for 2 h and characterized by X-ray photoelectron spectroscopy and X-ray diffraction. The X-ray diffraction data were refined by Rietveld method and the structural parameters were determined for the phases of each annealed samples. At 300 °C five phases were identified: Cubic and hexagonal cadmium selenides and the contaminants: Potassium chloride, boron oxide and cadmium boron oxide. At 500 and 600 °C only the hexagonal cadmium selenide phase was identified besides the other above mentioned contaminant. 相似文献