全文获取类型
收费全文 | 7458篇 |
免费 | 739篇 |
国内免费 | 653篇 |
专业分类
化学 | 523篇 |
晶体学 | 15篇 |
力学 | 130篇 |
综合类 | 222篇 |
数学 | 7135篇 |
物理学 | 825篇 |
出版年
2024年 | 19篇 |
2023年 | 111篇 |
2022年 | 208篇 |
2021年 | 171篇 |
2020年 | 279篇 |
2019年 | 285篇 |
2018年 | 279篇 |
2017年 | 287篇 |
2016年 | 208篇 |
2015年 | 160篇 |
2014年 | 245篇 |
2013年 | 625篇 |
2012年 | 306篇 |
2011年 | 427篇 |
2010年 | 432篇 |
2009年 | 599篇 |
2008年 | 519篇 |
2007年 | 448篇 |
2006年 | 439篇 |
2005年 | 352篇 |
2004年 | 321篇 |
2003年 | 275篇 |
2002年 | 260篇 |
2001年 | 239篇 |
2000年 | 222篇 |
1999年 | 200篇 |
1998年 | 182篇 |
1997年 | 129篇 |
1996年 | 98篇 |
1995年 | 84篇 |
1994年 | 79篇 |
1993年 | 47篇 |
1992年 | 51篇 |
1991年 | 27篇 |
1990年 | 29篇 |
1989年 | 27篇 |
1988年 | 23篇 |
1987年 | 20篇 |
1986年 | 10篇 |
1985年 | 23篇 |
1984年 | 26篇 |
1983年 | 7篇 |
1982年 | 17篇 |
1981年 | 12篇 |
1980年 | 8篇 |
1979年 | 11篇 |
1978年 | 4篇 |
1977年 | 9篇 |
1976年 | 4篇 |
1975年 | 4篇 |
排序方式: 共有8850条查询结果,搜索用时 140 毫秒
161.
Thomas Unnerstall 《Journal of statistical physics》1989,54(1-2):379-403
The irreversible macroscopic dynamics of the Josephson junction coupled to external wires acting as a current source is derived rigorously from the underlying microscopic Hamiltonian quantum mechanics. The external systems are treated in the singular coupling limit. The use of this limit is explicitly justified via an interpretation of the singular coupling limit in terms of the relative magnitudes of system, reservoir, and coupling energies. The qualitative behavior of the macroscopic dynamical equations is shown to depend sensitively and crucially on the interaction between the wires and the superconductors and on the size of the wires: the dc Josephson effect only happens when one lets Cooper pairs be driven into the junction by collective (i.e., small) reservoirs. 相似文献
162.
V. A. Pankratov Ts. M. Frenkel A. E. Shvorak S. V. Lindeman Yu. T. Struchkov 《Russian Chemical Bulletin》1993,42(1):81-87
A 11-complex of trinitrophenol with benzyldimethylamine (1) and a 111-complex, the product of the interaction of benzyldimethylamine, glycidyl phenyl ether, and phenol (2), have been synthesized and characterized by means of X-ray analysis. Complex1 is a precursor for the catalysts of selective isocyanate cyclotrimerization, while complex2 is one of those catalysts. In the crystal structure complex1 forms H-bonded cationic-anionic aggregates with proton transfer from phenol to the N-atom of the tertiary amine. Complex2 crystallizes as a monohydrate (2a) with a strong H-bond between the quaternary ammonium and phenolic components, and exists in crystals in the form of globular H-bonded dimeric hydrates. Possible pathways of dissociation of complex2a are discussed. The data obtained may be used as a basis for further interpretation of the regularities of cyclotrimerization of isocyanates catalyzed by complexes of this type.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No 1, pp. 92–97, January, 1993. 相似文献
163.
Jean Bricmont Joel L. Lebowitz Christian Maes 《Journal of statistical physics》1987,48(5-6):1249-1268
We derive a number of new results for correlated nearest neighbor site percolation onZ
d. We show in particular that in three dimensions the strongly correlated massless harmonic crystal, i.e., the Gaussian random field with mean zero and covariance –, has a nontrivial percolation behavior: sites on whichS
x
h percolate if and only ifh
c
. with0
c
< . This provides the first rigorous example of a percolation transition in a system with infinite susceptibility. 相似文献
164.
Tomislav Došlić 《Journal of mathematical chemistry》2007,41(3):217-229
A global forcing set in a simple connected graph G with a perfect matching is any subset S of E(G) such that the restriction of the characteristic function of perfect matchings of G on S is an injection. The number of edges in a global forcing set of the smallest cardinality is called the global forcing number
of G. In this paper we prove several results concerning global forcing sets and numbers of benzenoid graphs. In particular, we
prove that all catacondensed benzenoids and catafused coronoids with n hexagons have the global forcing number equal to n, and that for pericondensed benzenoids the global forcing number is always strictly smaller than the number of hexagons. 相似文献
165.
Unicyclic Graphs with Minimal Energy 总被引:7,自引:0,他引:7
Yaoping Hou 《Journal of mathematical chemistry》2001,29(3):163-168
If G is a graph and 1,2,...,
n
are its eigenvalues, then the energy of G is defined as E(G)=|1|+|2|++|
n
|. Let S
n
3 be the graph obtained from the star graph with n vertices by adding an edge. In this paper we prove that S
n
3 is the unique minimal energy graph among all unicyclic graphs with n vertices (n6). 相似文献
166.
Jia-you Shu Mo Zhu Yi Shu Qi-jun Liu Tong Li 《高分子科学》2006,(4):395-401
The new chelate resins, abbreviated as PNBMZs and PBBMZs based on epoxide polymer, were synthesized by polycondensation of N,N-diglycidyl-4-glycidyloxyaniline or 1,4-bis(2,3-epoxypropyl)benzene with the primary amine group of 1,3-bis(benzimidazol-2yl)propylamine (BBPAH). The ion exchangers contain 2.71-3.23 mmol of the ligand contents per gram of the resin. Batch extraction capacities were determined for the metal chloride salts in buffer solutions in the pH range from -1 to 6.0. The chelate resins were very selective for Cu^2+, Zn^2+, Cd^2+ in the presence of other divalent transition metal ions. The maximum uptake capacities of PNBMZ (synthetic molar ratio = 1:1.5) under non-competitive condition were found to be 0.94 mmol/g for Cu^2+ at pH = 2, 1.3 mmol/g for Cd^2+ at pH = 1 and 1.75 mmol/g for Zn^2+ at pH = -1 respectively. While in the case of PBBMZ, it was 1.39 mmol/g for Cd〉 at pH = 1. The metal-uptake behaviors for both of them showed strong pH dependence, and their extraction capacities increase with decreasing pH. The uptake of Cu^2+ by the resin PNBMZs at pH = 1 was found to be rather fast with t1/2 = 18 min. Metal-uptake experiments under competitive conditions also confirm that the chelate resins have a high selectivity for Cu^2+, Zn^2+, Cd^2+ and the contrary pH dependence. 相似文献
167.
Summary In this paper an application is presented of the median molecule workflow to the de novo design of novel molecular entities with a property profile of interest. Median molecules are structures that are optimised to be similar to a set of existing molecules of interest as an approach for lead exploration and hopping. An overview of this workflow is provided together with an example of an instance using the similarity to camphor and menthol as objectives. The methodology of the experiments is defined and the workflow is applied to designing novel molecules for two physical property datasets: mean molecular polarisability and aqueous solubility. This paper concludes with a discussion of the characteristics of this method. 相似文献
168.
Let G be a simple graph with adjacency matrix A(G) and (G,x) the permanental polynomial of G. Let G × H denotes the Cartesian product of graphs G and H. Inspired by Kleins idea to compute the permanent of some matrices (Mol. Phy. 31 (3) (1976) 811–823), in this paper in terms of some orientation of graphs we study the permanental polynomial of a type of graphs. Here are some of our main results.1.If G is a bipartite graph containing no subgraph which is an even subdivision of K
2,3, then G has an orientation G
e such that (G,x) = det (xI-A(G
e
)), where A(G
e
) denotes the skew adjacency matrix of G
e.2.Let G be a 2-connected outerplanar bipartite graph with n vertices. Then there exists a 2-connected outerplanar bipartite graph
with 2n+2 vertices such that (G,x) is a factor of
.3.Let T be an arbitrary tree with n vertices. Then
, where
1
,
2
, ...,
n are the eigenvalues of T. 相似文献
169.
N. SanzJ. Zaccaro L. DelmotteC. Le Luyer A. Ibanez 《Journal of solid state chemistry》2002,165(1):25-34
Organic nanocrystals of N-4-nitrophenyl-l-prolinol (NPP) have been grown in sol-gel matrices prepared from silicon alkoxide precursors. Our process is based on the control of the nucleation and growth kinetics of the dye in the pores of dense gels. Nanocomposites gel-glasses are obtained with a high optical quality due to the small size of the nanocrystals (10-20 nm). Differential scanning calorimetry experiments evidenced clearly the melting point of NPP nanocrystals, which is registered 51°C above that of NPP powder. Micro-Raman and solid state NMR spectroscopies allowed us to demonstrate that our nanocrystallization process does not chemically modify NPP molecules. We specified also the nature of interactions existing between the NPP nanocrystals and the xerogels. These strong interactions, which explain the important increase of the melting point of the nanocrystals in comparison to the NPP powder, are hydrogen bonds between nitro groups of NPP and uncondensed silanol functions of the silicate network. 相似文献
170.
Ariel Fernández 《Theoretical chemistry accounts》1985,67(3):229-233
A structurally stable model of the standard adiabatic gradient field of the potential energy surface for certain pericyclic reactions is derived.These reactions are not subjected to the principles of orbital isomerism or to the Woodward-Hoffmann rules.Use is made of a principle established by Ariel Fernández and Oktay Sinanolu which precludes direct meta-IRC connections between transition states.It is shown that Jahn-Teller isomers of the singlet biradicals involved in the process are not interconvertible since the biradical configuration is not a transition state but a critical point with Hessian matrix with two negative eigenvalues.The topological features of the PES obtained by combinatorial methods are in full agreement with earlier results obtained from MINDO calculations. 相似文献