全文获取类型
收费全文 | 10116篇 |
免费 | 555篇 |
国内免费 | 42篇 |
专业分类
化学 | 7434篇 |
晶体学 | 36篇 |
力学 | 172篇 |
数学 | 1539篇 |
物理学 | 1532篇 |
出版年
2023年 | 76篇 |
2022年 | 79篇 |
2021年 | 155篇 |
2020年 | 236篇 |
2019年 | 201篇 |
2018年 | 146篇 |
2017年 | 120篇 |
2016年 | 418篇 |
2015年 | 379篇 |
2014年 | 407篇 |
2013年 | 490篇 |
2012年 | 672篇 |
2011年 | 719篇 |
2010年 | 514篇 |
2009年 | 417篇 |
2008年 | 659篇 |
2007年 | 585篇 |
2006年 | 551篇 |
2005年 | 562篇 |
2004年 | 476篇 |
2003年 | 346篇 |
2002年 | 318篇 |
2001年 | 165篇 |
2000年 | 137篇 |
1999年 | 152篇 |
1998年 | 118篇 |
1997年 | 169篇 |
1996年 | 121篇 |
1995年 | 120篇 |
1994年 | 114篇 |
1993年 | 97篇 |
1992年 | 98篇 |
1991年 | 63篇 |
1990年 | 50篇 |
1989年 | 72篇 |
1988年 | 67篇 |
1987年 | 39篇 |
1986年 | 41篇 |
1985年 | 53篇 |
1984年 | 46篇 |
1983年 | 31篇 |
1982年 | 56篇 |
1981年 | 38篇 |
1980年 | 31篇 |
1979年 | 30篇 |
1978年 | 31篇 |
1977年 | 24篇 |
1976年 | 17篇 |
1975年 | 25篇 |
1968年 | 18篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
171.
Vijayasarathi Nagarajan Barbara Müller Oksana Storcheva Klaus Köhler Andreas Pöppl 《Research on Chemical Intermediates》2007,33(8):705-724
Interactions and binding sites of the solvent molecules chloroform and ethanol to bis(acetylacetonate)oxovanadium(IV) (VO(acac)2) complexes in (frozen) solutions have been investigated by pulsed electron nuclear double resonance, sum peak electron spin
echo envelope modulation and hyperfine sublevel correlation spectroscopy. The experimental proton hyperfine coupling data
of coordinating solvent molecules have been interpreted using quantum chemical calculations (density functional theory). Experimental
and computed hyperfine couplings indicate that ethanol coordinates to vanadium in the equatorial plane of VO(acac)2 and chloroform interacts via hydrogen bonding to oxygens of the acac ligands. 相似文献
172.
Numerical Algorithms - A two-step quadratic spline collocation method is formulated for the solution of the Dirichlet biharmonic problem on the unit square rewritten as a coupled system of two... 相似文献
173.
Klaus-Werner Brzezinka Peter Reich Andreas Hampe Eckhard Schulz 《Fresenius' Journal of Analytical Chemistry》1995,352(5):486-488
An example is given for the application of Raman spectroscopy in material characterization. Raman spectra of carbonaceous materials obtained with the microscope attachment have been used to study orientation of graphite planes in a single carbon fibre under stress with a lateral resolution of 1 m.Dedicated to Professor Dr. H. Kriegsmann on the occasion of his 70th birthday 相似文献
174.
We show that certain manpower scheduling problems can be modeled as the following constrained matching problem. Given an undirected graphG = (V,E) with edge weights and a digraphD = (V,A). AMaster/Slave-matching (MS-matching) ofG with respect toD is a matching ofG such that for each arc (u, v) A for which the nodeu is matched, the nodev is matched, too. TheMS-Matching Problem is the problem of finding a maximum-weight MS-matching. Letk(D) be the maximum size of a (weakly) connected component ofD. We prove that MS-matching is an NP-hard problem even ifG is bipartite andk(D) 3. Moreover, we show that in the relevant special case wherek(D) 2, the MS-Matching Problem can be transformed to the ordinary Matching Problem.This research was supported by Grant 03-KL7PAS-6 of the German Federal Ministry of Research and Technology. 相似文献
175.
Asynchronous two-stage iterative methods 总被引:9,自引:0,他引:9
Summary.
Parallel block two-stage iterative methods
for the solution of linear systems of algebraic equations are studied.
Convergence is shown for monotone matrices and for -matrices.
Two different asynchronous versions of these methods
are considered and their convergence investigated.
Received September 7, 1993 / Revised version received April
21, 1994 相似文献
176.
The job-shop problem is one of the most difficult NP-hard scheduling problems. A 10×10-problem published in 1963 has been solved only recently by Carlier and Pinson using a branch and bound method. Other branch and bound algorithms have been developed recently. The efficiency of all these branch and bound methods relies on the concept of immediate selection which allows to introduce order relations on the setI of all operations to be processed on the same machine before branching. We present new algorithms for immediate selection. Among them are
- anO(max {n logn,f})-algorithm for fixing all disjunctions induced by cliques;
- anO(n 2)-algorithm based on concepts which are different from those used by Carlier and Pinson.
177.
178.
179.
It is shown that the axiom For any points x, y, z such that y is between x and z, there is a right triangle having x and z as endpoints of the hypotenuse and y as foot of the altitude to the hypotenuse, when added to three-dimensional Euclidean geometry over arbitrary ordered fields, is weaker than the axiom Every line which passes through the interior of a sphere intersects that sphere. 相似文献
180.
The characterisation and optimisation of an optical immunoassay with label free detection based on Reflectometric Interference Spectroscopy (RIfS) is presented. The immunoprobe is operated in a sequential scheme, where Fab-fragments react with analyte molecules in a first step. In a second step the optical transducer is used to quantify the amount of unoccupied Fab- fragments in the reaction mixture binding to the hapten-modified transducer surface. For optimisation of the test, the Fab-fragment concentration was varied between 2x10(-8) mol/l and 2.5x 10(-9) mol/l. Down to a concentration of 5x10(-9) mol/l a reduction in the limit of detection has been observed. At the lowest concentration investigated no further improvement has been found due to a reduced binding of the analyte and a strong decrease of antibody binding at the transducer surface. This finding could be explained by the thermodynamics of the antigen-antibody reaction and the performance of the optical transducer used. The limit of detection obtained is discussed with respect to thermodynamics, transducer characteristics and immunoprobe test format. 相似文献