全文获取类型
收费全文 | 18075篇 |
免费 | 3105篇 |
国内免费 | 2823篇 |
专业分类
化学 | 13184篇 |
晶体学 | 354篇 |
力学 | 1095篇 |
综合类 | 277篇 |
数学 | 2001篇 |
物理学 | 7092篇 |
出版年
2024年 | 68篇 |
2023年 | 350篇 |
2022年 | 646篇 |
2021年 | 650篇 |
2020年 | 673篇 |
2019年 | 737篇 |
2018年 | 615篇 |
2017年 | 615篇 |
2016年 | 787篇 |
2015年 | 843篇 |
2014年 | 1078篇 |
2013年 | 1429篇 |
2012年 | 1626篇 |
2011年 | 1772篇 |
2010年 | 1280篇 |
2009年 | 1239篇 |
2008年 | 1265篇 |
2007年 | 1245篇 |
2006年 | 1044篇 |
2005年 | 877篇 |
2004年 | 751篇 |
2003年 | 566篇 |
2002年 | 550篇 |
2001年 | 480篇 |
2000年 | 493篇 |
1999年 | 318篇 |
1998年 | 262篇 |
1997年 | 209篇 |
1996年 | 215篇 |
1995年 | 166篇 |
1994年 | 173篇 |
1993年 | 139篇 |
1992年 | 136篇 |
1991年 | 110篇 |
1990年 | 112篇 |
1989年 | 97篇 |
1988年 | 61篇 |
1987年 | 50篇 |
1986年 | 47篇 |
1985年 | 49篇 |
1984年 | 34篇 |
1983年 | 25篇 |
1982年 | 11篇 |
1981年 | 18篇 |
1980年 | 13篇 |
1979年 | 14篇 |
1978年 | 11篇 |
1977年 | 8篇 |
1976年 | 10篇 |
1975年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
11.
12.
Adsorption, desorption and activities of acid phosphatase on various colloidal particles from an Ultisol 总被引:1,自引:0,他引:1
Adsorption, desorption and activity of acid phosphatase on various soil colloidal particles and pure clay minerals were studied. Higher adsorption amounts and low percentage of desorption of acid phosphatase were found on fine soil clays (<0.2 μm). Electrostatic force and ligand exchange are the major driving forces that are involved in the adsorption of enzymes on soil clays. More enzyme molecules were adsorbed on soil clays in the presence of organic components. However, enzymes on organic clays were more easily released. One-third of the enzyme on goethite was adsorbed via ligand exchange process. Some other interactions, such as van der Waals force, hydrophobic force and hydrogen bonding may be more important in the adsorption of enzyme on kaolinite and the enzyme in this system cannot be easily removed. Coarse clays (0.2–2 μm) and inorganic soil clays had higher affinities for enzyme molecules than fine clays and organic clays, respectively. The activity of enzyme bound on soil clays was inhibited and the thermal stability was increased in the presence of organic matter. Data obtained in this study are helpful for a better understanding of the interactions of enzymes with inorganic and organic constituents in soil and associated environments. 相似文献
13.
Shen YH Li SH Li RT Han QB Zhao QS Liang L Sun HD Lu Y Cao P Zheng QT 《Organic letters》2004,6(10):1593-1595
Both coriatone (1). a novel highly oxygenated picrotoxane-type sesquiterpene, and corianlactone (2). with an unprecedented sesquiterpene basic skeleton, named coriane, were isolated from Coriaria nepalensis Wall. The structures of 1 and 2 were determined by analysis of their two-dimensional NMR data, and the structure of 2 was confirmed by X-ray analysis. Compounds 1 and 2 showed no remarkable inhibitory activity toward K(562) cells. They are cytotoxic with IC(50) > 50 microg/mL (cis-platinim: IC(50) = 0.49 microg/mL). 相似文献
14.
15.
Liang Chen 《Communications in Mathematical Physics》1995,167(2):431-469
A class of differential operator Lie algebras on the unit circle is introduced and discussed. They are the natural generalizations of the Witt algebra and the Virasoro algebra. Among them are the higher-spin algebrasW
1+ andW
which occur in the physics literature. 相似文献
16.
17.
18.
19.
A water-soluble nanometer-scale metallocapped polyrotaxane has been prepared by the inclusion complexation of azo-calixarenes with metallo-bridged bis(beta-CD)s, displaying highly selective binding for Ca(2+). 相似文献
20.
Liang SC Wang H Zhang ZM Zhang X Zhang HS 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2002,58(12):2605-2611
A new thiol weak-fluorescence probe, 5-maleimidyl-2-(m-methylphenyl)benzoxazole (MMPB), gives a highly fluorescence product in the presence of Cys. In this paper, MMPB has been developed for the fluorimetric determination of cysteine (Cys). At lambda(ex)/lambda(em) = 305.6/425.6 nm, the linear range is from 0 to 3.3 x 10(-7) mol l(-1) and the detection limit (sigma = 3) of 6.2 x 10(-10) mol l(-1). The main advantage of this method lies in the relative high selectivity compared with the methods using other N-substituted maleimide type of thiol reagents, in which 0.15-fold (molar ratio) of GSH is allowed and most of other amino acids at 100-fold (molar ratio) level had no obvious effect on the results. The proposed method has been applied to the determination of Cys in real samples. 相似文献