全文获取类型
收费全文 | 3467篇 |
免费 | 549篇 |
国内免费 | 581篇 |
专业分类
化学 | 2848篇 |
晶体学 | 46篇 |
力学 | 146篇 |
综合类 | 74篇 |
数学 | 360篇 |
物理学 | 1123篇 |
出版年
2024年 | 6篇 |
2023年 | 60篇 |
2022年 | 95篇 |
2021年 | 118篇 |
2020年 | 142篇 |
2019年 | 174篇 |
2018年 | 124篇 |
2017年 | 140篇 |
2016年 | 186篇 |
2015年 | 168篇 |
2014年 | 210篇 |
2013年 | 229篇 |
2012年 | 298篇 |
2011年 | 319篇 |
2010年 | 236篇 |
2009年 | 222篇 |
2008年 | 250篇 |
2007年 | 225篇 |
2006年 | 191篇 |
2005年 | 171篇 |
2004年 | 159篇 |
2003年 | 114篇 |
2002年 | 136篇 |
2001年 | 120篇 |
2000年 | 82篇 |
1999年 | 61篇 |
1998年 | 38篇 |
1997年 | 33篇 |
1996年 | 42篇 |
1995年 | 47篇 |
1994年 | 36篇 |
1993年 | 19篇 |
1992年 | 20篇 |
1991年 | 27篇 |
1990年 | 23篇 |
1989年 | 23篇 |
1988年 | 10篇 |
1987年 | 10篇 |
1986年 | 7篇 |
1985年 | 7篇 |
1983年 | 6篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1977年 | 1篇 |
1975年 | 3篇 |
1974年 | 1篇 |
1961年 | 1篇 |
1957年 | 1篇 |
1936年 | 1篇 |
排序方式: 共有4597条查询结果,搜索用时 15 毫秒
101.
102.
In this paper, we present some new perturbation bounds for the orthogonal projections onto the column and row spaces of a matrix, which improve some existing results. Numerical examples are presented to illustrate our results. 相似文献
103.
Abstract . The solvothermal reaction between cuprous iodide and the rigid triangular imidazole ligand in mixed N,N′‐dimethylacetamide (DMA)‐acetonitrile solvent leads to the isolation of the 3D metal‐organic framework [(Cu4I4)3(TIPA)4] · 7DMA ( 1 ) [TIPA = tri(4‐imidazolylphenyl) amine], which was characterized by elemental analysis, IR spectroscopy, powder X‐ray diffraction, and single‐crystal X‐ray diffraction. Topologically, the structure of 1 is an unprecedented 3,3,4,4‐connected net with a point symbol of {4.8.10}2{4.82}2{42.82.102}2{84.122}. Compound 1 exhibits orange‐red photoluminescence with an emission maximum at 622 nm at room temperature. 相似文献
104.
Target and non‐target identification of chemical components in Lamiophlomis rotata by liquid chromatography/quadrupole time‐of‐flight mass spectrometry using a three‐step protocol 下载免费PDF全文
105.
106.
Sheng Xia Shan Yin Shimin Tao Yanhui Shi Liangce Rong Xianyong Wei Zhimin Zong 《Research on Chemical Intermediates》2012,38(9):2435-2442
One-pot, multicomponent reaction for the synthesis of novel substituted pyrimidine derivatives: 4-amino-5-carbonitrile-2-nitroaminopyrimidine from aromatic aldehydes, 1-nitroguanidine, and malononitrile under ethanol is described. Because of containing many active functional groups, such as amino, cyan and nitro, these products are important intermediate of organic synthesis. The advantages of this procedure include the short reaction time, mild reaction conditions, and excellent yields. 相似文献
107.
108.
Xiaolan Tong Shan Wang Jun Zuo Yingchong Ge Qiang Gao Suijun Liu Jianhua Ding Fen Liu Jianqiang Luo Jianbo Xiong 《中国化学快报》2021,32(2):604-608
Two new hydrostable two-dimensional(2 D) uranyl coordination complexes [(UO_2)_5(μ_3-O)_2(nbca)_2].7 H_2O(1) and [(UO_2)_3(nbca)_2(H_2O)_3]·2 H_2O(2)(H_3 nbca=5-nitro-1,2,3-benzenetricarboxylic acid) were hydrothermal synthesized.Single-crystal structural refinements reveal that both of the two complexes were formed by the packing of 2D uranyl coordination sheets via the hydrogen bonds.The nbca ligand coordinating to the uranyl polyhedron centers constructed the 2D sheets.There are UO_8 hexagonal bipyramids and UO_7 pentagonal bipyramids in 1 while only U07 pentagonal bipyramids in 2.Photocatalytic degradation of rhodamine B(RhB) in aqueous solution was studied.Complex 2 possesses better performance than 1 with 96.2 % of the RhB was degraded in only 60 min.Mechanism studies reveal that the dissolved oxygens are essential to the RhB degradation.The photocurrent density of 2 is more stable than that of 1,which indicating the stronger ability to separate photoexcited electrons and hole pairs of 2. 相似文献
109.
110.