全文获取类型
收费全文 | 24073篇 |
免费 | 692篇 |
国内免费 | 149篇 |
专业分类
化学 | 14764篇 |
晶体学 | 180篇 |
力学 | 758篇 |
综合类 | 1篇 |
数学 | 3608篇 |
物理学 | 5603篇 |
出版年
2023年 | 135篇 |
2022年 | 184篇 |
2021年 | 299篇 |
2020年 | 358篇 |
2019年 | 353篇 |
2018年 | 268篇 |
2017年 | 246篇 |
2016年 | 565篇 |
2015年 | 484篇 |
2014年 | 555篇 |
2013年 | 1109篇 |
2012年 | 1141篇 |
2011年 | 1340篇 |
2010年 | 832篇 |
2009年 | 739篇 |
2008年 | 1156篇 |
2007年 | 1249篇 |
2006年 | 1123篇 |
2005年 | 1180篇 |
2004年 | 960篇 |
2003年 | 760篇 |
2002年 | 719篇 |
2001年 | 560篇 |
2000年 | 510篇 |
1999年 | 311篇 |
1998年 | 288篇 |
1997年 | 292篇 |
1996年 | 351篇 |
1995年 | 312篇 |
1994年 | 290篇 |
1993年 | 343篇 |
1992年 | 312篇 |
1991年 | 292篇 |
1990年 | 242篇 |
1989年 | 237篇 |
1988年 | 248篇 |
1987年 | 237篇 |
1986年 | 205篇 |
1985年 | 287篇 |
1984年 | 283篇 |
1983年 | 214篇 |
1982年 | 231篇 |
1981年 | 221篇 |
1980年 | 217篇 |
1979年 | 210篇 |
1978年 | 219篇 |
1977年 | 159篇 |
1976年 | 172篇 |
1975年 | 148篇 |
1974年 | 172篇 |
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
161.
E. Maria Claesson Nilesh C. Mehendale Robertus J.M. Klein Gebbink Gerard van Koten Albert P. Philipse 《Journal of magnetism and magnetic materials》2007
Monodisperse magnetizable colloidal silica particles in a stable dispersion have been functionalized with a homogeneous catalyst: a PCP–pincer Pd-complex. In a proof-of-principle experiment we demonstrate the catalytic activity of the colloids in a C–C bond formation reaction. Advantages of the magnetic silica carriers are the large surface-to-volume ratio and the easy recovery by magnetic separation. After magnetic separation, the catalyst-loaded particles are readily redispersed for further use. 相似文献
162.
Long-Mei Zeng Xiong Fu Jing-Yu Su Florecita De Guzman J. Francis Schmitz M. Bilayet Hossain Dick van Der Helm 《中国化学》1991,9(2):136-143
Three pyrrololactam alkaloids have been isolated from the marine sponge Phacellia fusca Schmidt collected from the South China Sea, and their structures were determined as 1–3 , on the grounds of spectral data. This is the first report of these compounds from this sponge. The structure of 1 was confirmed by X-ray analysis. 相似文献
163.
164.
Martin van Gemmeren 《Transactions of the American Mathematical Society》1996,348(6):2413-2426
In the first part we prove an extension of the Chern-Lashof inequality for noncompact immersed manifolds with finitely many ends. For this we give a lower bound of the total absolute curvature in terms of topological invariants of the manifold. In the second part we discuss tightness properties for such immersions. Finally, we give an upper bound for the substantial codimension.
165.
Vasyl Kinzhybalo Jan Janczak 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(3):m105-m107
The crystals of the title compound, [Mg(C32H16N8)(H2O)]·2C3H9N, are built up from MgPc(H2O) [Pc is phthalocyaninate(2−)] and n‐propylamine molecules that interact via O—H⋯N hydrogen bonds. The MgPc(H2O) molecule is non‐planar. The central Mg atom is coordinated by the four equatorial isoindole N atoms of the Pc ring system and by the O atom of an axial water molecule. The Mg atom is displaced by 0.509 (1) Å from the N4 plane towards the water O atom. MgPc(H2O)·2(n‐propylamine) molecules related by the inversion centre are linked by N—H⋯O hydrogen bonds to form a dimeric aggregate. 相似文献
166.
Modelling financial and insurance time series with Lévy processes or with exponential Lévy processes is a relevant actual practice and an active area of research. It allows qualitatively and quantitatively good adaptation to the empirical statistical properties of asset returns. Due to model incompleteness it is a problem of considerable interest to determine the dependence of option prices in these models on the choice of pricing measures and to establish nontrivial price bounds. In this paper we review and extend ordering results of stochastic and convex type for this class of models. We also extend the ordering results to processes with independent increments (PII) and present several examples and applications as to α-stable processes, NIG-processes, GH-distributions, and others. Criteria are given for the Lévy measures which imply corresponding comparison results for European type options in (exponential) Lévy models. 相似文献
167.
168.
169.
170.
Let be a bounded, connected linearly convex set in with boundary. We show that the maximal ideal (both in ) and ) consisting of all functions vanishing at is generated by the coordinate functions .
Received: 2 July 2001; in final form: 26 September 2001 / Published online: 28 February 2002 相似文献