全文获取类型
收费全文 | 6731篇 |
免费 | 228篇 |
国内免费 | 50篇 |
专业分类
化学 | 4714篇 |
晶体学 | 38篇 |
力学 | 157篇 |
数学 | 1221篇 |
物理学 | 879篇 |
出版年
2024年 | 11篇 |
2023年 | 51篇 |
2022年 | 165篇 |
2021年 | 206篇 |
2020年 | 134篇 |
2019年 | 154篇 |
2018年 | 119篇 |
2017年 | 96篇 |
2016年 | 234篇 |
2015年 | 195篇 |
2014年 | 247篇 |
2013年 | 413篇 |
2012年 | 457篇 |
2011年 | 529篇 |
2010年 | 336篇 |
2009年 | 325篇 |
2008年 | 404篇 |
2007年 | 424篇 |
2006年 | 390篇 |
2005年 | 373篇 |
2004年 | 282篇 |
2003年 | 201篇 |
2002年 | 210篇 |
2001年 | 89篇 |
2000年 | 70篇 |
1999年 | 61篇 |
1998年 | 48篇 |
1997年 | 49篇 |
1996年 | 78篇 |
1995年 | 48篇 |
1994年 | 41篇 |
1993年 | 37篇 |
1992年 | 45篇 |
1991年 | 36篇 |
1990年 | 22篇 |
1989年 | 29篇 |
1988年 | 23篇 |
1987年 | 22篇 |
1986年 | 28篇 |
1985年 | 36篇 |
1984年 | 28篇 |
1983年 | 25篇 |
1982年 | 30篇 |
1981年 | 20篇 |
1980年 | 22篇 |
1979年 | 15篇 |
1978年 | 12篇 |
1977年 | 12篇 |
1975年 | 8篇 |
1934年 | 9篇 |
排序方式: 共有7009条查询结果,搜索用时 15 毫秒
31.
32.
Mikhael Balabane Thierry Cazenave Luis Vázquez 《Communications in Mathematical Physics》1990,133(1):53-74
We prove the existence of stationary states for nonlinear Dirac equations of the form (E) $$i\sum\limits_{\mu = 0}^3 {\gamma ^\mu \partial _\mu \psi - M\psi + F\left( {\bar \psi \psi } \right)\psi = 0,} $$ whereM>0 andF is a singular self-interaction. In particular, in the model case whereF(s)=?s ?α, for some 0<α<1, and for every ω>M, there exists a solution of (E) of the form ψ(t, x)=e iωt?(x), wherex 0=t andx=(x 1,x 2,x 3), such that ? has compact support. IF 0<α<1/3, then ? is of classC 1. If 1/3<α<1, then ? is continuously differentiable, except on some sphere {|x|=R}, where |??| is infinite. 相似文献
33.
The Radiative Transfer Equation is the nonlinear transport equation
相似文献
34.
Generalized solutions are defined for stochastic evolution equations of the formdY
t
=A
*
Y
t
dt + dZ
t
on the nuclear triplel(R
d
) L2(R
d
) l(R
d
), whereA does not mapl(R
d
) into itself. One case which is treated in detail involvesA = –(–)
/2
,0 < < 2. This example arises as the Langevin equation for the fluctuation limit of a system of particles migrating according to a symmetric stable process and undergoing critical branching in a random medium.The research of D. A. Dawson was supported by the Natural Sciences and Engineering Research Council of Canada. L. G. Gorostiza's research was supported in part by CONACyT Grants PCEXCNA-040319 and 140102 G203-006, Mexico. 相似文献
35.
Amorín M Castedo L Granja JR 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(22):6543-6551
Here we report the preparation and structural characteristics of self-assembling peptide tubelets composed of 32-membered rings formed of alternating alpha-amino acids and cis-3-aminocyclohexanecarboxylic acids. The tubelets possess a partial hydrophobic core environment, provided by the projection of the cyclohexane C2 methylene moiety into the lumen, and a Van der Waals pore diameter of about 7 A. 相似文献
36.
37.
38.
Luis JM Torrent-Sucarrat M Solà M Bishop DM Kirtman B 《The Journal of chemical physics》2005,122(18):184104
Our new simple method for calculating accurate Franck-Condon factors including nondiagonal (i.e., mode-mode) anharmonic coupling is used to simulate the C2H4+X2B3u<--C2H4X1A(g) band in the photoelectron spectrum. An improved vibrational basis set truncation algorithm, which permits very efficient computations, is employed. Because the torsional mode is highly anharmonic it is separated from the other modes and treated exactly. All other modes are treated through the second-order perturbation theory. The perturbation-theory corrections are significant and lead to a good agreement with experiment, although the separability assumption for torsion causes the C2D4 results to be not as good as those for C2H4. A variational formulation to overcome this circumstance, and deal with large anharmonicities in general, is suggested. 相似文献
39.
ZHOU Cheng-He Juan F.Miravet M.Isabel Burguete Santiago V.Luis BAI Xue YUAN Yong 《有机化学》2004,24(Z1):380
Polynitrogen receptors such as bis-histidine peptides possess strong ability to bind metals, which play much important roles in medicinal, bioinorganic, bioorganic, biomimetic and supramolecular chemistry. In order to investigate the interaction of these hosts with a variety of neutral, cationic and anionic guests, several techniques, for example, NMR,potentiometric tirations and monocrystal X-ray diffraction have been employed. Among them NMR is a powerful technique for unraveling the structure of polynitrogen receptors as long as they are in solution where the rapid tumbling of molecules averages out the anisotropies such as chemical shift and dipole-dipole interactions. General 1H NMR approach has been widely used for the study of host-guest interaction, but it is difficult for the accurate measurement in complexes structures, particularly metal complexes structures in which how the polynitrogen receptors bind metal, and which nitrogen binds metal and so on. 相似文献
40.
Coordination of dinitrogen to Sellmann-type iron (II) complexes in a sulfur-dominated coordination sphere, which emulates
the environment of iron centers in the FeMo-cofactor of nitrogenase, is analyzed with respect to spin states, spin barriers,
and the effect of trans-ligands. Such detailed investigations became only recently feasible when the reliability of density functional methods, which
are the only quantum chemical methods capable of describing large transition metal complexes, could significantly be improved
for the calculation of energies for states of different spin. It is found that the actual binding energy of dinitrogen is
of sufficient magnitude for a reasonably strong fixation of N2 by Sellmann-type coordination compounds. However, potential fixation is determined by additional factors which reduce the
binding energy. One factor is the change in spin state of the N2-free metal fragment, which lowers the total energy and quenches the thermodynamic stabilization effect of the binding energy.
In addition, the metal fragment rearranges and gains even more stabilization energy for the un-coordinated state. Apart from
these thermodynamical effects, the existence of spin barriers, which must be overcome upon binding of dinitrogen, leads to
kinetical effects, which cannot be neglected. 相似文献
|