全文获取类型
收费全文 | 105868篇 |
免费 | 17108篇 |
国内免费 | 12305篇 |
专业分类
化学 | 74271篇 |
晶体学 | 1136篇 |
力学 | 5979篇 |
综合类 | 667篇 |
数学 | 12691篇 |
物理学 | 40537篇 |
出版年
2024年 | 351篇 |
2023年 | 2067篇 |
2022年 | 3667篇 |
2021年 | 3837篇 |
2020年 | 4177篇 |
2019年 | 3957篇 |
2018年 | 3713篇 |
2017年 | 3333篇 |
2016年 | 5021篇 |
2015年 | 4960篇 |
2014年 | 6054篇 |
2013年 | 7841篇 |
2012年 | 9333篇 |
2011年 | 10050篇 |
2010年 | 6904篇 |
2009年 | 6617篇 |
2008年 | 6702篇 |
2007年 | 5988篇 |
2006年 | 5625篇 |
2005年 | 4767篇 |
2004年 | 3983篇 |
2003年 | 3168篇 |
2002年 | 2876篇 |
2001年 | 2420篇 |
2000年 | 2019篇 |
1999年 | 2092篇 |
1998年 | 1780篇 |
1997年 | 1591篇 |
1996年 | 1577篇 |
1995年 | 1395篇 |
1994年 | 1262篇 |
1993年 | 1051篇 |
1992年 | 952篇 |
1991年 | 808篇 |
1990年 | 671篇 |
1989年 | 517篇 |
1988年 | 381篇 |
1987年 | 339篇 |
1986年 | 336篇 |
1985年 | 262篇 |
1984年 | 190篇 |
1983年 | 153篇 |
1982年 | 125篇 |
1981年 | 78篇 |
1980年 | 59篇 |
1979年 | 26篇 |
1978年 | 23篇 |
1976年 | 22篇 |
1975年 | 22篇 |
1957年 | 27篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
A hybrid cluster complex, formed by chelating a chromogenic ligand to a [2Fe-2S] cluster, sensitively exhibited differential colorimetric responses towards Hg2+, Cd2+, Cr3+, Pb2, Sn2+, Cu2+, Zn2+, Fe3+ and Co2+ in water at physiological pH. Speciation of some of these metal elements, such as Cr(III) and Sn(IV), was also studied by UV/Vis absorption. 相似文献
92.
Raymond Mackay Jie Zhang Qi Wu Yuzhuo Li 《Colloids and surfaces. A, Physicochemical and engineering aspects》2004,250(1-3):343-348
The longitudinal relaxation times (T1) of water in concentrated silica and alumina slurries were measured as a function of solids content. It was shown that the results could be fit very well with a two-phase fast-exchange model between free and surface-bound water. As expected, values of T1 for bound water were in the order of 20–2000 times lower than that for free water, indicating a higher effective viscosity of the surface-bound water. The strength of the interaction depended on the particular surface, and all of the aluminas examined interacted more strongly with water than the two silicas studied, which themselves differed considerably. The chemical mechanical polishing (CMP) removal rate of tantalum by silica slurries was shown to be directly correlated with the interaction parameters, derived from the NMR relation times rather than with total surface hydroxyl group concentration. 相似文献
93.
94.
LI Shufeng LI Qian YANG Xinlin HUANG Wenqiang** State Key Laboratory of Functional Polymer Materials for Adsorption Separation Institute of Polymer Chemistry Nankai University Tianjin China 《Chinese Journal of Reactive Polymers》2004,(Z1)
1. INTRODUCTION The development of efficient polymer-supported catalysts has attracted much attention [1]. For obtaining polymeric catalysts, catalytically active groups were introduced onto polymers mostly by copolymerization of the appropriate monomers bearing the desired catalyticfunctionalities (e.g. imidazole, OH, and COOH) or by modification of preformed polymers.Another possibility involves the attachment of side chains, containing the desired arrangement of functional groups, o… 相似文献
95.
96.
5,6-Dihydro-OSW-1 (1) was synthesized following our previous procedure for the total synthesis of OSW-1. This compound demonstrated slightly stronger potency than that of OSW-1 against the growth of cancer cells. 相似文献
97.
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
98.
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
99.
Zhong Hong YAN Chun Hao YANG Xi Han WU Yu Yuan XIEDivision of Chemistry Shanghai Second Medical University Shanghai Sate Key Laboratory of Drug Research Shanghai Institute of Materia Medica Shanghai Institutesfor Biological Sciences Shanghai 《中国化学快报》2004,(4)
The first and facile synthesis of (±)syringaresinol was described. 相似文献
100.
Ming Zhao WANG Guan Liang CAI Ling XIA Jun Jian YAO Hong Yan CHEN Zhao Xing MENG Bo Li LIUDepartment of Chemistry Beijing Normal University Beijing Chemical Defense Institute PLA Beijing 《中国化学快报》2004,15(4):495-497
The crystal structures of two potential tumor imaging agents and therapeutic agents -copper(Ⅱ) complexes with salicylidene-tyrosinato Schiff base and nitrogen-donor chelating Lewis base, [Cu(sal-tyr)(bipy)] 1 and [Cu(sal-tyr)(phen)]2CH3OH 2 are presented. Our work is helpful to get deep understanding of novel 64Cu tumor imaging agents and therapeutic agents. 相似文献