全文获取类型
收费全文 | 98701篇 |
免费 | 14225篇 |
国内免费 | 11482篇 |
专业分类
化学 | 68357篇 |
晶体学 | 1110篇 |
力学 | 6149篇 |
综合类 | 992篇 |
数学 | 12111篇 |
物理学 | 35689篇 |
出版年
2024年 | 273篇 |
2023年 | 1664篇 |
2022年 | 2931篇 |
2021年 | 3078篇 |
2020年 | 3279篇 |
2019年 | 3299篇 |
2018年 | 2954篇 |
2017年 | 2722篇 |
2016年 | 4138篇 |
2015年 | 4326篇 |
2014年 | 5234篇 |
2013年 | 6967篇 |
2012年 | 8175篇 |
2011年 | 8505篇 |
2010年 | 6028篇 |
2009年 | 6002篇 |
2008年 | 6474篇 |
2007年 | 5882篇 |
2006年 | 5556篇 |
2005年 | 4785篇 |
2004年 | 3950篇 |
2003年 | 3156篇 |
2002年 | 3193篇 |
2001年 | 2683篇 |
2000年 | 2348篇 |
1999年 | 2230篇 |
1998年 | 1763篇 |
1997年 | 1541篇 |
1996年 | 1546篇 |
1995年 | 1335篇 |
1994年 | 1245篇 |
1993年 | 1085篇 |
1992年 | 963篇 |
1991年 | 811篇 |
1990年 | 683篇 |
1989年 | 594篇 |
1988年 | 445篇 |
1987年 | 415篇 |
1986年 | 353篇 |
1985年 | 351篇 |
1984年 | 232篇 |
1983年 | 198篇 |
1982年 | 161篇 |
1981年 | 128篇 |
1980年 | 100篇 |
1978年 | 81篇 |
1977年 | 62篇 |
1976年 | 61篇 |
1975年 | 63篇 |
1973年 | 64篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
In recent years, the synthesis of chiral tetrahedral clusters has been studied extensively and various types are accessible , which are a kind of organometallic compounds with greatly growing interest due to their potential application to asymmetric reaction catalysts. As an efficient 相似文献
992.
DongJunWANG QunLUO DanDanJIA XiaoDongLI XinQiouWANG YongHuang ZhenZHEN XinHouLIU 《中国化学快报》2003,14(12):1306-1308
The hydrolysis of tetraethoxysilane (TEOS) occurred on the surface of poly(methyl methacrylate) (PMMA) microshperes immediately after these microshperes were prepared in TEOS. Micron-sized hollow SiO2 spheres were obtained by calcination of the coated PMMA microshperes. It was found that the final hollow spheres were constituted by small SiO2 particles. 相似文献
993.
Novel chiral iPr-tris(oxazoline)/Cu(ClO4)2 x 6H2O catalyzed coupling of terminal acetylenes and nitrones to afford cis-disubstituted beta-lactams is described; the choice of base proves essential to both the diastereoselectivity and the enantioselectivity. 相似文献
994.
Chen T Wang L Jiang G Wang J Dong X Wang X Zhou J Wang C Wang W 《The journal of physical chemistry. B》2005,109(10):4624-4630
The electrochemical behavior of poly(ferrocenyldimethylsilane-b-dimethylsiloxane) (PFDMS-b-PDMS) films deposited on a glassy carbon electrode was investigated by means of cyclic voltammetry (CV). The influences of the solvent, film thickness, temperature, and PDMS block length in PFDMS-b-PDMS on the electrode process were discussed. It was found that in 0.1 M aqueous LiClO(4) the electrochemical processes of the films on a glassy carbon electrode were complex and have a low rate of electron transport and mass diffusion. The kinetic parameters obtained indicated that the electrode process was controlled by both the electrode reaction and mass diffusion. 相似文献
995.
996.
997.
Yong Ding Baochun Ma Qiang Gao Guixian Li Liang Yan Jishuan Suo 《Journal of molecular catalysis. A, Chemical》2005,230(1-2):121-128
The epoxidation of cyclopentene with hydrogen peroxide catalyzed by 12-heteropolyacids of molybdenum and tungsten (H3PMo12−nWnO40, n = 1–11), 12-tungstophosphoric acid and 12-molybdophosphoric acid combined with cetylpyridinium bromide as a phase transfer reagent was carried out in acetonitrile. Among 13 heteropolyacids investigated, catalyst of H3PMo6W6O40 showed the highest activity, giving a conversion of 60% and a selectivity of 95% in the epoxidation of cyclopentene. The fresh catalysts and the catalysts under reaction condition were characterized by UV–vis, FT-IR and 31P NMR spectroscopy, which has revealed that all of the molybdotungstophosphoric acids were degraded in the presence of hydrogen peroxide to form a considerable amount of phosphorus-containing species. The active species resulted from H3PMo6W6O40 are new kinds of phosphorus-containing species, which is different from {PO4[WO(O2)2]4}3−. 相似文献
998.
Kebin Zhou Hongde Chen Qun Tian Dixin Shen Xiaobai Xu 《Reaction Kinetics and Catalysis Letters》2002,77(1):65-72
Pd/LaFe0.8Co0.2O3 was found to be more active than the Pd/Al2O3 catalyst in propane oxidation. Activity and the oxidation state of palladium were strongly affected by the redox ratio (S) of reactants. Higher propane conversion could be obtained under rich conditions at higher temperatures, contributing to steam reforming. The presence of excess steam would bring about inhibition and oscillation. 相似文献
999.
1000.