全文获取类型
收费全文 | 2162篇 |
免费 | 59篇 |
国内免费 | 4篇 |
专业分类
化学 | 1654篇 |
晶体学 | 4篇 |
力学 | 18篇 |
数学 | 326篇 |
物理学 | 223篇 |
出版年
2023年 | 29篇 |
2022年 | 19篇 |
2021年 | 23篇 |
2020年 | 61篇 |
2019年 | 50篇 |
2018年 | 27篇 |
2017年 | 17篇 |
2016年 | 40篇 |
2015年 | 28篇 |
2014年 | 39篇 |
2013年 | 66篇 |
2012年 | 68篇 |
2011年 | 95篇 |
2010年 | 38篇 |
2009年 | 44篇 |
2008年 | 69篇 |
2007年 | 62篇 |
2006年 | 71篇 |
2005年 | 68篇 |
2004年 | 55篇 |
2003年 | 43篇 |
2002年 | 38篇 |
2001年 | 17篇 |
2000年 | 21篇 |
1999年 | 15篇 |
1998年 | 18篇 |
1996年 | 14篇 |
1995年 | 20篇 |
1994年 | 20篇 |
1991年 | 21篇 |
1990年 | 15篇 |
1987年 | 15篇 |
1986年 | 17篇 |
1985年 | 27篇 |
1984年 | 29篇 |
1983年 | 25篇 |
1982年 | 38篇 |
1981年 | 22篇 |
1980年 | 24篇 |
1979年 | 42篇 |
1978年 | 25篇 |
1977年 | 34篇 |
1976年 | 27篇 |
1975年 | 24篇 |
1974年 | 19篇 |
1973年 | 15篇 |
1967年 | 19篇 |
1959年 | 14篇 |
1956年 | 20篇 |
1934年 | 23篇 |
排序方式: 共有2225条查询结果,搜索用时 15 毫秒
991.
Katsonis N Marchenko A Taillemite S Fichou D Chouraqui G Aubert C Malacria M 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(11):2574-2581
We recently discovered that a linear multifunctional trimethylsilylacetylene (TMSA) compound forms long-range and highly stable self-assembled monolayers (SAMs) on reconstructed Au(111). To better understand the interactions governing self-assembly in this new system, we synthesized a series of homologue organosilanes and performed scanning tunneling microscopy (STM) measurements at the Au(111)/n-tetradecane interface. The four TMSA-terminated linear silanes that we synthesized self-assemble in similar ways on gold, with the molecules standing upright on the surface. In contrast, compounds with a slightly modified terminal group but the same polyunsaturated linear chain above the TMSA head do not self-assemble. In particular, substituting a methyl group of TMSA with a more bulky one prevents self-assembly. Removing the C triple bond C triple bond of TMSA or substituting the Si atom by a C atom also hinders self-assembly. Finally, substituting one methyl group of TMSA by a hydrogen atom induces self-assembly but in a different geometry, with the molecules lying flat on the gold surface in a quasi-epitaxy mode. Our molecular approach demonstrates the key role played by the TMSA head in self-assembly, its origin being twofold: 1) the TMSA layers are commensurate to the Au(111) adlattice along the <112> direction, and 2) the C triple bond C triple bond of TMSA activates the Si atom and induces the creation of a surface Si-Au chemical bond. The highly stable TMSA-based SAMs appear then as promising materials for applications in surface modification. 相似文献
992.
Max Vecchi Willy Walther Ernst Glinz Thomas Netscher Rudolf Schmid Michel Lalonde Walter Vetter 《Helvetica chimica acta》1990,73(4):782-789
Separation and Quantitation of All Eight Stereoisomers of α-Tocopherol by Chromatography The results of the analysis of several derivatives of (all-rac)-α-tocopherol by HPLC on a chiral stationary phase and by capillary GC on a achiral stationary phase are reported. Consecutive application of both methods to the ethyl-ether derivative allows the separation and quantification of all eight possible stereoisomers of (all-rac)-α-tocopherol. 相似文献
993.
Zusammenfassung Lösungen von Kartoffelamylopektin und Kartoffelamylosen zeigen in einer Apparatur, welche die Empfindlichkeit= 1 besitzt, keine Strömungsdoppelbrechung. Durch Vergleich der Rotationsdiffusionskonstante, welche aus der durch die Empfindlichkeit der Apparatur geschätzten Maxwellschen Konstante folgt, und des für kugelige Teilchen berechneten Wertes findet man, daß sowohl das Amylopektin wie auch die Amylose Moleküle besitzen, die nicht wesentlich von der Kugelgestalt abweichen. 相似文献
994.
Isolation and Structure Elucidation of 36 Diterpenoids from Leaf-Glands of Plectranthus edulis (VATKE ) T.T. AYE Analysis of the polar diterpenoids from the yellow glands of the title plant from Kenya and Abyssinia led to the identification of several novel abietanoids. Main compound is the known edulon A ( 40 ), a 5(4→3) abeo-abietane. Minor compounds include 6 different royleanones, 15 spirocoleons, 3 vinylogous quinones, 8 acylhydroquinones (as their 6,7-dioxo compounds or the tautomeric disophenols), 2 naphthaquinones (as the 1,10-seco-abietanoids), and deacetyledulon A. The known coleon-A-lactone (37) now has also been found in Plectranthus edulis. The intermediacy of the γ-enollactol 44 , combined with a leaving group on C(3) is postulted to explain the biogenesis of the unusual 4H-5-oxaaceanthrylen skeleton of edulon A. 相似文献
995.
996.
997.
998.
999.
Erik Pettersson Patrik L. Ståhl Hovsep Mahdessian Max Käller Joakim Lundeberg Afshin Ahmadian 《Electrophoresis》2009,30(21):3691-3695
We report on the incorporation of the Visual DNA concept in a genotyping assay as a simple and straightforward detection tool. The principle of trapping streptavidin‐coated superparamagnetic beads of micrometer size for visualization of genetic variances is used for PrASE‐based detection of a panel of mutations in the severe and common genetic disorder of cystic fibrosis. The method allows a final investigation of genotypes by the naked eye and the output is easily documented using a regular hand‐held device with an integrated digital camera. A number of samples were run through the assay, showing rapid and accurate detection using superparamagnetic beads and an off‐the‐shelf neodymium magnet. The assay emphasizes the power of Visual DNA and demonstrates the potential value of the method in future point‐of‐care tests. 相似文献
1000.