全文获取类型
收费全文 | 42771篇 |
免费 | 6159篇 |
国内免费 | 5379篇 |
专业分类
化学 | 31499篇 |
晶体学 | 558篇 |
力学 | 2268篇 |
综合类 | 426篇 |
数学 | 5387篇 |
物理学 | 14171篇 |
出版年
2024年 | 89篇 |
2023年 | 703篇 |
2022年 | 1145篇 |
2021年 | 1324篇 |
2020年 | 1536篇 |
2019年 | 1525篇 |
2018年 | 1325篇 |
2017年 | 1265篇 |
2016年 | 1802篇 |
2015年 | 1852篇 |
2014年 | 2167篇 |
2013年 | 2929篇 |
2012年 | 3558篇 |
2011年 | 3917篇 |
2010年 | 2722篇 |
2009年 | 2608篇 |
2008年 | 2980篇 |
2007年 | 2656篇 |
2006年 | 2334篇 |
2005年 | 2069篇 |
2004年 | 1636篇 |
2003年 | 1377篇 |
2002年 | 1415篇 |
2001年 | 1173篇 |
2000年 | 909篇 |
1999年 | 859篇 |
1998年 | 712篇 |
1997年 | 631篇 |
1996年 | 669篇 |
1995年 | 577篇 |
1994年 | 527篇 |
1993年 | 455篇 |
1992年 | 437篇 |
1991年 | 374篇 |
1990年 | 313篇 |
1989年 | 248篇 |
1988年 | 208篇 |
1987年 | 165篇 |
1986年 | 162篇 |
1985年 | 188篇 |
1984年 | 115篇 |
1983年 | 76篇 |
1982年 | 76篇 |
1981年 | 61篇 |
1980年 | 53篇 |
1979年 | 58篇 |
1978年 | 40篇 |
1976年 | 37篇 |
1974年 | 41篇 |
1973年 | 45篇 |
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
101.
QuanXiangwu YanPingSHI LiYANG 《中国化学快报》2004,15(12):1441-1444
From the alcoholic extract of the whole plant of Ligularia virgaurea spp. oligocephala, three novel eremophilane sesquiterpene lactones, 6α, 10α-dihydroxy- 1-oxoeremophila-7(11), 8(9)-dien-8, 12-olide, 613, 10α-dihydroxy-1-oxoeremophila-7 (ll), 8 (9)-dien-8, 12-olide and 10α-hydroxy-1-oxoeremophila-7(l 1), 8(9)-dien-8, 12-olide were isolated. Their structures were elucidated by various spectroscopic methods including intensive 2D NMR techniques (COSY,HMQC, HMBC and ^1H-^1H NOESY) and HR-MS. 相似文献
102.
NianYuanTAN XiaoMingXIAO ZeLinLI TakekoMATSUMURA-INOUE 《中国化学快报》2004,15(6):687-690
A new cobalt(Ⅱ) complex with tridentate ligand 2, 6-bis (benzimidazol-2-yl)pyridine has been synthesized by microwave irradiation method and characterized by elemental analysis,electrochemical and spectral methods. The binding of the complex with calf thymus DNA has also been investigated by absorption and fluorescence spectra. 相似文献
103.
XiangGuoSHI DaFangZHONG YuMingSUN YuFengZHANG 《中国化学快报》2004,15(4):431-434
A sensitive analytical method to identify active metabolites of bitespiramycin in rat urine and bile was developed by liquid chromatography-electrospray ionization tandem mass spectrometry(LC/ESI-MS^n).Bitespiramycin and its major active metabolites in rat urine and bile were isolated and identified as M1 serial(spiramycin Ⅰ,Ⅱ,Ⅲ),M2 serial(platenomycin A1,josamycin and leucomycin A1) and M3 serial(deisovalerylplatenomycin A1,deisovaleryljosamycin,deisovalerylleucomycin A1). 相似文献
104.
Baker‘s yeast mediated reduction of optically active diketone is described. The two keto groups are efficiently differentiated and the ee value of the recovered material is considerably raised. It affords highly optically active key intermediates efficiently for the synthesis of natural polyhydroxylated agarofuran products. 相似文献
105.
DongXiangLI WanGuoHOU ShuPingLI MingTuHAO GaoYongZHANG 《中国化学快报》2004,15(2):224-227
The relation of the isoelectric point (IEP) and the point of zero net charge (PZNC) of the hydrotalcite-like compounds was discussed. It was found that the IEP does not equal to the PZNC and the IEP is higher than the PZNC. The structural positive charges existing in the HTlc,which cause the difference between the IEP and the PZNC. The effects of the structural positive charges of the HTlc on its IEP and PZNC are the same as the specific adsorption of metal cations. 相似文献
106.
XiangBaoMENG HuiLI QingLI ZhongJunLI 《中国化学快报》2004,15(7):777-778
An unusual reductive ring-opening reaction of phthalimide with sodium hydride in anhydrous DMF was observed for the first time. The presumed mechanism was described in detail. 相似文献
107.
108.
Thermal oxidation of polyethylene filled with dispersed copper and containing an amine antioxidant was studied. The concentration ranges in which the catalytic effect of the metal on the polymer oxidation or the stabilizing effect of the antioxidant prevails were determined. Under certain conditions, dispersed copper enhances the stabilizing effect of the antioxidant. 相似文献
109.
Lin Huaxin 《数学年刊B辑(英文版)》1993,14(3):387-396
The author studies the problem whether a multiplier of a hereditary C^*-subalgebra B of a C^*-algebra A can be extended to a multiplier of A. One related problem is the Hahn-Banach extension theorem for Hilbert modules over C^*-algebras. It is shown that every self-dual Hilbert module over W^*-algebra or an injective C^*-algebra is injective. 相似文献
110.