全文获取类型
收费全文 | 19987篇 |
免费 | 2886篇 |
国内免费 | 1087篇 |
专业分类
化学 | 20600篇 |
晶体学 | 68篇 |
力学 | 591篇 |
综合类 | 46篇 |
数学 | 289篇 |
物理学 | 2366篇 |
出版年
2024年 | 32篇 |
2023年 | 271篇 |
2022年 | 713篇 |
2021年 | 763篇 |
2020年 | 1381篇 |
2019年 | 1035篇 |
2018年 | 857篇 |
2017年 | 752篇 |
2016年 | 1400篇 |
2015年 | 1206篇 |
2014年 | 1215篇 |
2013年 | 1404篇 |
2012年 | 1095篇 |
2011年 | 1219篇 |
2010年 | 1002篇 |
2009年 | 1052篇 |
2008年 | 1006篇 |
2007年 | 953篇 |
2006年 | 906篇 |
2005年 | 801篇 |
2004年 | 816篇 |
2003年 | 683篇 |
2002年 | 1317篇 |
2001年 | 337篇 |
2000年 | 215篇 |
1999年 | 234篇 |
1998年 | 273篇 |
1997年 | 200篇 |
1996年 | 125篇 |
1995年 | 141篇 |
1994年 | 73篇 |
1993年 | 46篇 |
1992年 | 45篇 |
1991年 | 42篇 |
1990年 | 40篇 |
1989年 | 25篇 |
1988年 | 33篇 |
1987年 | 25篇 |
1986年 | 72篇 |
1985年 | 16篇 |
1984年 | 13篇 |
1983年 | 8篇 |
1981年 | 8篇 |
1980年 | 9篇 |
1979年 | 11篇 |
1978年 | 10篇 |
1977年 | 8篇 |
1972年 | 11篇 |
1970年 | 7篇 |
1966年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
81.
Saeed Balalaie Elahe Kowsari Mehri S. Hashtroudi 《Monatshefte für Chemie / Chemical Monthly》2003,134(3):453-456
Summary. Three component condensation of alkylacetoacetates, primary amines, and alkyl cyanoacetates catalyzed by solid supports under
microwave irradiation gave N-alkyl 3-cyano-6-hydroxy-2(1H)-pyridinones with high yields. Upon carrying out the reaction under the same condition on acidic alumina, zeolite HY, silica
gel, and montmorillonite K-10, the best yields were achieved by silica gel.
Corresponding author. E-mail: balalaie@yahoo.com
Received August 28, 2002; accepted September 3, 2002 相似文献
82.
介绍未确知数学方法,并用未确知数学方法分析处理物理实验数据,与传统的数据处理方法比较,未确知数学方法不必对数据作任何假设,因此更合理,也更符合实际。 相似文献
83.
Tetraalkyltin complexes, SnR4 (R = Me, Et, Pr, Bu) could react with Pt/HY at 193, 243, 273 and 333 K, respectively. The reactions occurred on the surface of the zeolite and the organotin grafted zeolites were characterized in detail. The framework and the microporous structure of the grafted Pt/HY zeolites were retained. However, the modified zeolites showed better size selectivity in the absorption of hydrocarbons. 相似文献
84.
85.
大学物理实验教学改革的实践与思索 总被引:10,自引:0,他引:10
本主要介绍了我校近年来在大学物理实验课程体系和教学内容改革的实践及下一步改革的思路。 相似文献
86.
87.
Future pathways for combinatorial chemistry 总被引:1,自引:0,他引:1
David Brown 《Molecular diversity》1997,2(4):217-222
Summary Investment in combinatorial chemistry (combichem) in the pharmaceutical industry is being driven by the need for increased efficiency. Results from pioneers in the field have demonstrated where mixture or discrete compound synthesis is useful, and what mixture sizes and compound concentrations are appropriate. To make the techniques of combichem of general utility in drug discovery, a broad range of advances is still required. Conversion of organic chemistry to solid phase conditions is key, as are developments in linkers and resins. Library design methodology requires further development. Combinatorial biosynthesis of focused libraries of natural products holds great promise for capitalising on hardwon natural product leads. Miniaturisation of screens is required to reduce the cost of screening combinatorial libraries. Developments in the processes preceding and following synthesis are required to enable the flow of increased numbers of compounds without new bottlenecks developing. The impact of combinatorial chemistry will be greatly enhanced by synergy with ongoing parallel developments in genetic technologies, screening technologies and bioinformatics. 相似文献
88.
89.
90.
Serge Palacin Christophe Bureau Julienne Charlier Guy Deniau Brigitte Mouanda Pascal Viel 《Chemphyschem》2004,5(10):1468-1481
Electrografting is a powerful and versatile technique for modifying and decorating conducting surfaces with organic matter. Mainly based on the electro-induced polymerization of dissolved electro-active monomers on metallic or semiconducting surfaces, it finds applications in various fields including biocompatibility, protection against corrosion, lubrication, soldering, functionalization, adhesion, and template chemistry. Starting from experimental observations, this Review highlights the mechanism of the formation of covalent metal-carbon bonds by electro-induced processes, together with major applications such as derivatization of conducting surfaces with biomolecules that can be used in biosensing, lubrication of low-level electrical contacts, reversible trapping of ionic waste on reactive electrografted surfaces as an alternative to ion-exchange resins, and localized modification of conducting surfaces, a one-step process providing submicrometer grafted areas and which is used in microelectronics. 相似文献