全文获取类型
收费全文 | 935篇 |
免费 | 19篇 |
国内免费 | 8篇 |
专业分类
化学 | 572篇 |
晶体学 | 9篇 |
力学 | 23篇 |
数学 | 185篇 |
物理学 | 173篇 |
出版年
2023年 | 2篇 |
2022年 | 10篇 |
2021年 | 12篇 |
2020年 | 22篇 |
2019年 | 15篇 |
2018年 | 18篇 |
2017年 | 8篇 |
2016年 | 24篇 |
2015年 | 16篇 |
2014年 | 22篇 |
2013年 | 52篇 |
2012年 | 55篇 |
2011年 | 52篇 |
2010年 | 47篇 |
2009年 | 40篇 |
2008年 | 60篇 |
2007年 | 55篇 |
2006年 | 44篇 |
2005年 | 39篇 |
2004年 | 27篇 |
2003年 | 39篇 |
2002年 | 30篇 |
2001年 | 19篇 |
2000年 | 20篇 |
1999年 | 8篇 |
1998年 | 17篇 |
1997年 | 13篇 |
1996年 | 11篇 |
1995年 | 15篇 |
1994年 | 12篇 |
1993年 | 15篇 |
1992年 | 7篇 |
1991年 | 17篇 |
1990年 | 7篇 |
1989年 | 7篇 |
1988年 | 9篇 |
1987年 | 4篇 |
1986年 | 5篇 |
1985年 | 10篇 |
1984年 | 12篇 |
1983年 | 6篇 |
1982年 | 13篇 |
1981年 | 11篇 |
1980年 | 9篇 |
1979年 | 6篇 |
1978年 | 5篇 |
1977年 | 2篇 |
1976年 | 5篇 |
1974年 | 2篇 |
1933年 | 1篇 |
排序方式: 共有962条查询结果,搜索用时 31 毫秒
101.
Diana Cruz-Garritz Juventino Garcia-Alejandre Hugo Torrens Cecilio Alvarez Raul A. Toscano Rene Poilblanc Alain Thorez 《Transition Metal Chemistry》1991,16(1):130-135
Summary The thiolato-bridged dinuclear compounds [Rh(-SR)-(COD)]2, where R=p-C6HF4 (1),p-C6H4F (2) and CF3 (3), are obtained from the chloro-bridged analogue by ligand exchange.Compound (1) crystallizes in the space group P1 with a=9.740(3)Å, b=11.642(4)Å, c=13.997(6)Å, =103.87(3)°, =106.98(3)° and =105.10(2)°; z=2. In this dinuclear molecule both Rh atoms have a square planar coordination sharing one edge, namely the two sulphur bridging atoms. The Rh—Rh separation of 2.96 Å is consistent with at most a very weak metal-metal interaction. Upon addition of CO the dimeric [Rh(-SR)(CO)2]2 (4), (5) and (6) are obtained, but addition of PPh3 affords the monomeric species [Rh(SR)(PPh3)-(COD)] (7), (8) and (9). Reactions of the dimeric tetracarbonyl derivatives with PPh3 vary with the nature of R; [Rh(-SR)(PPh3)(CO)]2 is obtained when R=p-C6H4F (10) and CF3 (11) but monomeric [Rh(SR)-(PPh3)(CO)2] (12) is produced when R=p-C6HF4. The latter mononuclear compounds, with R=p-C6H4F (13) and CF3 (14), are also formed by reaction of [Rh(SR)-(PPh3)(COD)] with CO. 相似文献
102.
The quantitative electrochemical generation of bromine at a platinum electrode in acetic acid is described. Coulometric methods for the determination of hydroquinone and 2-methylhydroquinone are reported. The best results are obtained with 0.7–1.1 M potassium acetate solutions as supporting electrolyte, and biamperometric end-point detection. The effects of water and acetic anhydride on the accuracy of titrations are discussed. Determination of the formal redox potential of the Br2/Br- system in a 0.9 M potassium acetate solution in acetic acid showed that bromide is oxidized directly to bromine at a platinum electrode with 100% current efficiency. 相似文献
103.
R. Garibay-Alonso J. Dorantes-Dávila G. M. Pastor 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,52(1-3):167-170
Finite temperature magnetic properties of small FeN clusters (N ≤6) are determined in the framework of a spin-fluctuation itinerant-electron theory based on a functional integral formulation of the canonical partition function and derived statistical averages. The free energy associated to each configuration of the exchange fields throughout the cluster are calculated by using Haydock-Heine-Kellys recursion method. The statistical averages of physical interest are obtained by performing parallel-tempering Monte Carlo simulations. Representative results are discussed for the average magnetization per atom as a function of temperature. The interplay between local environment and magnetization curves is analyzed by considering the low-temperature limit of the local spin-fluctuations energies ΔFl(ξ) at different atoms l. The electronic calculations are contrasted with the predictions of simple of phenomenological Heisenberg-like models. 相似文献
104.
García Ruano JL Martín-Castro AM Tato F Pastor CJ 《The Journal of organic chemistry》2005,70(18):7346-7352
[reaction: see text] Optically pure functionalized cyanohydrins derived from 1-[2-(p-tolylsulfinyl)phenyl] ethanone can be obtained by the reaction of 2-p-tolylsulfinyl benzaldehyde derived cyanohydrins with bases and further treatment with suitable electrophiles. High yields and excellent stereoselectivities (up to de >98%) were obtained for these remote 1,4-asymmetric induction processes controlled by a sulfinyl chiral inductor. 相似文献
105.
106.
107.
The paper is devoted to a numerical limit analysis of a hollow spheroidal model with a von Mises solid matrix. To this purpose, existing kinematic and static 3D-FEM codes for the case of spherical cavities have been modified and improved to account for the model of a spheroidal cavity confocal with the external spheroidal boundary. The optimized conic programming formulations and the resulting codes appear to be very efficient. This framework is then applied to the derivation of numerical upper and lower anisotropic bounds in the case of an oblate void. The numerical results obtained from a series of tests are presented and allow to assess the accuracy of closed-form expressions of the macroscopic criteria proposed by
[Gologanu et al., 1994] and [Gologanu et al., 1997] for porous media with oblate voids. 相似文献
108.
Marino Vega‐Vazquez Juan Carlos Cobas Manuel Martin‐Pastor 《Magnetic resonance in chemistry : MRC》2010,48(10):749-752
A parallel localized spectroscopy (PALSY) method is presented to speed up the acquisition of multidimensional NMR (nD) spectra. The sample is virtually divided into a discrete number of nonoverlapping slices that relax independently during consecutive scans of the experiment, affording a substantial reduction in the interscan relaxation delay and the total experiment time. PALSY was tested for the acquisition of three experiments 2D COSY, 2D DQF‐COSY and 2D TQF‐COSY in parallel, affording a time‐saving factor of 3–4. Some unique advantages are that the achievable resolution in any dimension is not compromised in any way: it uses conventional NMR data processing, it is not prone to generate spectral artifacts, and once calibrated, it can be used routinely with these and other combinations of NMR spectra. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
109.
In this paper, we construct all 3-connected binary matroids with circumference equal to 6 or 7 having large rank. 相似文献
110.