全文获取类型
收费全文 | 11686篇 |
免费 | 237篇 |
国内免费 | 43篇 |
专业分类
化学 | 6873篇 |
晶体学 | 102篇 |
力学 | 402篇 |
数学 | 1883篇 |
物理学 | 2706篇 |
出版年
2022年 | 137篇 |
2021年 | 150篇 |
2020年 | 153篇 |
2019年 | 164篇 |
2018年 | 161篇 |
2017年 | 141篇 |
2016年 | 232篇 |
2015年 | 200篇 |
2014年 | 233篇 |
2013年 | 678篇 |
2012年 | 474篇 |
2011年 | 570篇 |
2010年 | 401篇 |
2009年 | 331篇 |
2008年 | 486篇 |
2007年 | 430篇 |
2006年 | 416篇 |
2005年 | 390篇 |
2004年 | 387篇 |
2003年 | 317篇 |
2002年 | 322篇 |
2001年 | 217篇 |
2000年 | 204篇 |
1999年 | 160篇 |
1998年 | 127篇 |
1997年 | 149篇 |
1996年 | 178篇 |
1995年 | 135篇 |
1994年 | 132篇 |
1993年 | 164篇 |
1992年 | 161篇 |
1991年 | 169篇 |
1990年 | 125篇 |
1989年 | 130篇 |
1988年 | 136篇 |
1987年 | 190篇 |
1986年 | 157篇 |
1985年 | 200篇 |
1984年 | 188篇 |
1983年 | 151篇 |
1982年 | 172篇 |
1981年 | 188篇 |
1980年 | 183篇 |
1979年 | 177篇 |
1978年 | 176篇 |
1977年 | 170篇 |
1976年 | 150篇 |
1975年 | 166篇 |
1974年 | 135篇 |
1973年 | 125篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Giang Truong Nguyen Prof. Dr. Liviu Ungur 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(30):e202200227
Employing radical bridges between anisotropic metal ions has been a viable route to achieve high-performance single-molecule magnets (SMMs). While the bridges have been mainly considered for their ability to promote exchange interactions, the crystal-field effect arising from them has not been taken into account explicitly. This lack of consideration may distort the understanding and limit the development of the entire family. To shed light on this aspect, herein we report a theoretical investigation of a series of N -radical-bridged diterbium complexes. It is found that while promoting strong exchange coupling between the terbium ions, the N -radical induces a crystal field that interferes destructively with that of the outer ligands, and thus reduces the overall SMM behavior. Based on the theoretical results, we conclude that the SMM behavior in this series could be further maximized if the crystal field of the outer ligands is designed to be collinear with that of the radical bridge. This conclusion can be generalized to all exchange-coupled SMMs. 相似文献
2.
3.
4.
5.
6.
7.
In this study, stoichiometric protonation constants of L-tyrosine, L-cysteine, L-tryptophane, L-lysine, and L-histidine, and
their methyl and ethyl esters in water and ethanol–water mixtures of 30, 50, and 70% ethanol (v/v), were determined potentiometrically
using a combined pH electrode system calibrated as the concentration of hydrogen ion. Titrations were performed at 25∘C and the ionic strength of the medium was maintained at 0.10 mol⋅L−1 using sodium chloride. Protonation constants were calculated by using the BEST computer program. The effect of solvent composition
on the protonation constants is discussed. The log10 K2 values of esters generally decreased with increasing ethanol content. However, the log10 K1 values of the esters of L-tyrosine, L-cysteine, and L-tryptophane were found to increase with increasing ethanol content
in contrast those of L-lysine and L-histidine esters. 相似文献
8.
Hendrik Van Maldeghem 《Journal of Geometry》1997,58(1-2):192-202
We characterize in a geometrical way those Suzuki-Tits ovoids which are defined over a perfect fieidK (or equivalently living inside a self polar symplectic quadrangle). We simplify our axioms in the particular cases that (1) the associated Suzuki group has exactly two orbits in the set of lines ofPG(3,K), and (2) the ovoid is finite.Senior Research Associate at the Belgian National Fund for Scientific Research 相似文献
9.
Photobleaching was studied during recording of confocal scanning laser microscopy. Studies on fluorescent gels of FITC-labeled
dextran were used to evaluate differential bleaching along thez-axis. Differential bleaching along the z-axis was observed and it was seen that this was related to the numerical aperture
of the objective in use. This points to the conclusion that photon energy flux density is an important parameter in photobleaching.
To check if photon energy flux density heterogeneity is affected by local variation in the refractive index of the sample,
photobleaching rates were calculated for different fluorescent objects (sections of seeds, animal cells stained with nuclear
stains, immunocytochemistry preparations) and a pronounced similarity was found between photobleaching rates and DIC images. 相似文献
10.
C. Daum L. Hertzberger W. Hoogland R. Jongerius S. Peters P. Van Deurzen V. Chabaud A. Gonzalez-Arroyo B. Hyams H. Tiecke P. Weilhammer A. Dwurazny G. Polok M. Rozanska K. Rybicki M. Turala J. Turnau G. Ascoli H. Backer G. Blanar M. Cerrada H. Dietl J. Gallivan M. Glaubmann R. Klanner E. Lorenz G. Lütjens G. Lutz W. Männer U. Stierlin I. Blakey M. Bowler R. Cashmore J. Loken W. Spalding G. Thompson B. Alper C. Damerell A. Gillman C. Hardwick M. Hotchkiss F. Wickens ACCMOR Collaboration 《Zeitschrift fur Physik C Particles and Fields》1981,10(2):95-100
Muon electron pairs were detected in an Al multiplate spark chamber, exposed to a neutrino beam from the CERN PS. The leptons were not accompanied by other particles, except occasionally by protons. The background came mainly from muon associated π0 production, with one decay gamma lost. It was determined empirically, together with the small contribution from υ e reactions. For electron energies above 2 GeV the background is 5.7±1.5 events, whereas 18 (μe)-candidates have been observed. Hence the effect is established, with a rate of about 10?4 as compared to the muonic reactions above 3 GeV. Charm creation as the origin of this (μe)-production process is excluded; heavy neutral lepton production does not fit the kinematics observed. Instead the events are compatible with the two-body decay of an object with variable invariant mass of order 1 GeV, possibly resulting from axion interactions. 相似文献