全文获取类型
收费全文 | 21466篇 |
免费 | 3670篇 |
国内免费 | 4300篇 |
专业分类
化学 | 16907篇 |
晶体学 | 316篇 |
力学 | 1273篇 |
综合类 | 334篇 |
数学 | 2628篇 |
物理学 | 7978篇 |
出版年
2024年 | 51篇 |
2023年 | 377篇 |
2022年 | 717篇 |
2021年 | 774篇 |
2020年 | 875篇 |
2019年 | 896篇 |
2018年 | 728篇 |
2017年 | 726篇 |
2016年 | 1135篇 |
2015年 | 1150篇 |
2014年 | 1348篇 |
2013年 | 1701篇 |
2012年 | 1706篇 |
2011年 | 1856篇 |
2010年 | 1453篇 |
2009年 | 1469篇 |
2008年 | 1683篇 |
2007年 | 1397篇 |
2006年 | 1305篇 |
2005年 | 1106篇 |
2004年 | 976篇 |
2003年 | 772篇 |
2002年 | 988篇 |
2001年 | 779篇 |
2000年 | 680篇 |
1999年 | 470篇 |
1998年 | 347篇 |
1997年 | 243篇 |
1996年 | 275篇 |
1995年 | 210篇 |
1994年 | 222篇 |
1993年 | 190篇 |
1992年 | 124篇 |
1991年 | 149篇 |
1990年 | 121篇 |
1989年 | 71篇 |
1988年 | 66篇 |
1987年 | 53篇 |
1986年 | 52篇 |
1985年 | 53篇 |
1984年 | 26篇 |
1983年 | 33篇 |
1982年 | 14篇 |
1981年 | 18篇 |
1980年 | 9篇 |
1979年 | 13篇 |
1978年 | 6篇 |
1974年 | 4篇 |
1957年 | 3篇 |
1936年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Jing Zhihong Ling Baoping Yu Yang Qi Wei Zhang Shufang 《Journal of Sol-Gel Science and Technology》2015,73(1):112-117
Journal of Sol-Gel Science and Technology - A novel gas sensing material, La–Y co-doped TiO2 nanoparticles, was synthesized by sol–gel method and applied to detect organic pollutants... 相似文献
2.
3.
Highly dispersed palladium nanoclusters incorporated in amino‐functionalized silica spheres for the selective hydrogenation of succinic acid to γ‐butyrolactone 下载免费PDF全文
Highly dispersed palladium nanoclusters incorporated on amino‐functionalized silica sphere surfaces (Pd/SiO2‐NH2) were fabricated by a simple one‐pot synthesis utilizing 3‐(2‐aminoethylamino)propyltrimethoxysilane (AAPTS) as coordinating agent. Uniform palladium nanoclusters with an average size of 1.1 nm can be obtained during the co‐condensation of tetraethyl orthosilicate and AAPTS owing to the strong interaction between palladium species and amino groups in AAPTS. The palladium particle size can be controlled by addition of AAPTS and plays a significant role in the catalytic performance. The Pd/SiO2‐NH2 catalyst exhibits high catalytic activity for succinic acid hydrogenation with 100% conversion and 94% selectivity towards γ‐butyrolactone using 1,4‐dioxane as solvent at 240°C and 60 bar for 4 h. Moreover, the Pd/SiO2‐NH2 catalyst is robust and readily reusable without loss of its catalytic activity. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
4.
5.
Metabolic profiles of dioscin in rats revealed by ultra‐performance liquid chromatography quadrupole time‐of‐flight mass spectrometry 下载免费PDF全文
He Zhu Jin‐Di Xu Qian Mao Hong Shen Ming Kong Jian‐Ping Chen Song‐Lin Li 《Biomedical chromatography : BMC》2015,29(9):1415-1421
Dioscin (DIS), one of the most abundant bioactive steroidal saponins in Dioscorea sp., is used as a complementary medicine to treat coronary disease and angina pectoris in China. Although the pharmacological activities and pharmacokinetics of DIS have been well demonstrated, information regarding the final metabolic fates is very limited. This study investigated the in vivo metabolic profiles of DIS after oral administration by ultra‐performance liquid chromatography quadrupole time‐of‐flight mass spectrometry method. The structures of the metabolites were identified and tentatively characterized by means of comparing the molecular mass, retention time and fragmentation pattern of the analytes with those of the parent compound. A total of eight metabolites, including seven phase I and one phase II metabolites, were detected and tentatively identified for the first time. Oxidation, deglycosylation and glucuronidation were found to be the major metabolic processes of the compound in rats. In addition, a possible metabolic pathway on the biotransformation of DIS in vivo was proposed. This study provides valuable and new information on the metabolism of DIS, which will be helpful for further understanding its mechanism of action. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
6.
7.
8.
The first α‐diimine nickel(I) complex having a chloro bridge is reported. The centrosymmetric dinuclear structure of {[ArN?C(Me)C(Me)?NAr]NiCl}2[Ar?2,6?C6H3(i‐Pr)2] features two chelating α‐diimine ligands and two bridged chlorine atoms, so that a distorted tetrahedral N2Cl2 coordination geometry for nickel results. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
9.
10.
A lithium(I) coordination polymer has been formed from LiClO4 and the 2,2′‐bipyrimidine (bpym) ligand in which each square pyramidal lithium(I) atom is coordinated in the basal plane by four nitrogen donor atoms derived from two bpym ligands and one water molecule at the apical position. These are connected into a layer structure via hydrogen‐bonding interactions involving the perchlorate anions. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献