全文获取类型
收费全文 | 42052篇 |
免费 | 4241篇 |
国内免费 | 7363篇 |
专业分类
化学 | 35340篇 |
晶体学 | 1926篇 |
力学 | 2332篇 |
综合类 | 333篇 |
数学 | 2358篇 |
物理学 | 11367篇 |
出版年
2024年 | 99篇 |
2023年 | 381篇 |
2022年 | 831篇 |
2021年 | 872篇 |
2020年 | 1193篇 |
2019年 | 1091篇 |
2018年 | 950篇 |
2017年 | 1152篇 |
2016年 | 1602篇 |
2015年 | 1543篇 |
2014年 | 1902篇 |
2013年 | 3001篇 |
2012年 | 3416篇 |
2011年 | 2406篇 |
2010年 | 2052篇 |
2009年 | 2575篇 |
2008年 | 2738篇 |
2007年 | 2836篇 |
2006年 | 2653篇 |
2005年 | 2438篇 |
2004年 | 2390篇 |
2003年 | 2032篇 |
2002年 | 2172篇 |
2001年 | 1391篇 |
2000年 | 1426篇 |
1999年 | 1150篇 |
1998年 | 1014篇 |
1997年 | 829篇 |
1996年 | 830篇 |
1995年 | 732篇 |
1994年 | 691篇 |
1993年 | 526篇 |
1992年 | 539篇 |
1991年 | 321篇 |
1990年 | 268篇 |
1989年 | 200篇 |
1988年 | 201篇 |
1987年 | 139篇 |
1986年 | 123篇 |
1985年 | 136篇 |
1984年 | 109篇 |
1983年 | 87篇 |
1982年 | 83篇 |
1981年 | 75篇 |
1980年 | 72篇 |
1979年 | 72篇 |
1978年 | 57篇 |
1977年 | 56篇 |
1974年 | 44篇 |
1973年 | 50篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
A. Khrennikov 《Annalen der Physik》2003,12(10):575-585
We study the probabilistic consequences of the choice of the basic number field in the quantum formalism. We demonstrate that by choosing a number field for a linear space representation of quantum model it is possible to describe various interference phenomena. We analyse interference of probabilistic alternatives induced by real, complex, hyperbolic (Clifford) and p‐adic representations. 相似文献
12.
V. V. Kozlov 《Functional Analysis and Its Applications》2005,39(4):271-283
We discuss the symplectic geometry of linear Hamiltonian systems with nondegenerate Hamiltonians. These systems can be reduced to linear second-order differential equations characteristic of linear oscillation theory. This reduction is related to the problem on the signatures of restrictions of quadratic forms to Lagrangian planes. We study vortex symplectic planes invariant with respect to linear Hamiltonian systems. These planes are determined by the solutions of quadratic matrix equations of a special form. New conditions for gyroscopic stabilization are found. 相似文献
13.
14.
What Is Its Real Existing Form?——Theoretical and Experimental Studies on 2-Mercaptobenzothiazole 总被引:1,自引:0,他引:1
1 INTRODUCTION The study of heterocyclic molecules with aroma- tic rings and their absorptions on metals is of con- siderable importance from both theoretical and te- chnological points of view. These molecules are in- teresting because of their applications as corrosion inhibitors and flotation collectors, and their abilities to form self-assembly layers[1]. 2-Mercaptobenzo- thiazole (C7H5NS2, in the following MBT) is an important heterocyclic molecule, which can be used as corrosion … 相似文献
15.
Shinji Takesue 《Journal of statistical physics》1989,56(3-4):371-402
This is the first part of a series devoted to the study of thermodynamic behavior of large dynamical systems with the use of a family of fully-discrete and conservative models named elementary reversible cellular automata (ERCAs). In this paper, basic properties such as conservation laws and phase space structure are investigated in preparation for the later studies. ERCAs are a family of one-dimensional reversible cellular automata having two Boolean variables on each site. Reflection and Boolean conjugation symmetries divide them into 88 equivalence classes. For each rule, additive conserved quantities written in a certain form are regarded as a kind of energy, if they exist. By the aid of the discreteness of the variables, every ERCA satisfies the Liouville theorem or the preservation of phase space volume. Thus, if an energy exists in the above sense, statistical mechanics of the model can formally be constructed. If a locally defined quantity is conserved, however, it prevents the realization of statistical mechanics. The existence of such a quantity is examined for each class and a number of rules which have at least one energy but no local conservation laws are selected as hopeful candidates for the realization of thermodynamic behavior. In addition, the phase space structure of ERCAs is analyzed by enumerating cycles exactly in the phase space for systems of comparatively small sizes. As a result, it is revealed that a finite ERCA is not ergodic, that is, a large number of orbits coexist on an energy surface. It is argued that this fact does not necessarily mean the failure of thermodynamic behavior on the basis of an analogy with the ergodic nature of infinite systems. 相似文献
16.
K. C. Kumara Swamy E. Balaraman M. Phani Pavan N. N. Bhuvan Kumar K. Praveen Kumar N. Satish Kumar 《Journal of Chemical Sciences》2006,118(6):495-501
The diversity of products in the reaction of diethyl azodicarboxylate (DEAD)/diisopropyl azodicarboxylate (DIAD) and activated
acetylenes with PIII compounds bearing oxygen or nitrogen substituents is discussed. New findings that are useful in understanding the nature
of intermediates involved in the Mitsunobu reaction are highlighted. X-ray structures of two new compounds (2-t-Bu-4-MeC6H3O)P (μ-N-t-Bu)2P+[(NH-t-Bu)N[(CO2]-i-Pr)(HNCO2-i-Pr)]](Cl-)(2-t-Bu-4-MeC6H3OH)(23)and [CH2(6-t-Bu-4-Me-C6H2O)2P(O)C(CO2Me)C-(CO2Me)CClNC(O)Cl] (33) are also reported. The structure of23 is close to one of the intermediates proposed in the Mitsunobu reaction. 相似文献
17.
The first α‐diimine nickel(I) complex having a chloro bridge is reported. The centrosymmetric dinuclear structure of {[ArN?C(Me)C(Me)?NAr]NiCl}2[Ar?2,6?C6H3(i‐Pr)2] features two chelating α‐diimine ligands and two bridged chlorine atoms, so that a distorted tetrahedral N2Cl2 coordination geometry for nickel results. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
18.
The title compound is a centrosymmetric dimer with each cadmium in a distorted CdS5 square pyramidal geometry. The Cd–S bond distances range from 2.5626(11) to 2.8459(11) Å. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
19.
A lithium(I) coordination polymer has been formed from LiClO4 and the 2,2′‐bipyrimidine (bpym) ligand in which each square pyramidal lithium(I) atom is coordinated in the basal plane by four nitrogen donor atoms derived from two bpym ligands and one water molecule at the apical position. These are connected into a layer structure via hydrogen‐bonding interactions involving the perchlorate anions. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
20.
Fei Chang Dongheng Zhang Haijian Yang Haibin Song 《Journal of organometallic chemistry》2004,689(5):936-946
The synthesized 1-aryliminomethylenylnaphthalen-2-ol derivatives reacted with nickel chloride to form bis(1-aryliminomethylenylnaphthalen-2-oxy)nickel complexes. All resultant compounds were structurally characterized by elemental analyses, IR and H NMR, and the structures of the formed complexes were elucidated by X-ray crystal structure analysis. The complexes show high catalytic activities for the vinyl polymerization of norbornene in the presence of methylaluminoxane. The catalytic activity variations have been followed by gas chromatography through monitoring the conversion of norbornene. 相似文献