全文获取类型
收费全文 | 610篇 |
免费 | 16篇 |
国内免费 | 2篇 |
专业分类
化学 | 357篇 |
晶体学 | 9篇 |
力学 | 22篇 |
数学 | 132篇 |
物理学 | 108篇 |
出版年
2023年 | 4篇 |
2022年 | 10篇 |
2021年 | 17篇 |
2020年 | 9篇 |
2019年 | 13篇 |
2018年 | 9篇 |
2017年 | 13篇 |
2016年 | 24篇 |
2015年 | 24篇 |
2014年 | 23篇 |
2013年 | 48篇 |
2012年 | 37篇 |
2011年 | 43篇 |
2010年 | 44篇 |
2009年 | 28篇 |
2008年 | 36篇 |
2007年 | 40篇 |
2006年 | 39篇 |
2005年 | 31篇 |
2004年 | 22篇 |
2003年 | 15篇 |
2002年 | 11篇 |
2001年 | 7篇 |
2000年 | 10篇 |
1999年 | 8篇 |
1998年 | 6篇 |
1997年 | 9篇 |
1995年 | 1篇 |
1994年 | 4篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 4篇 |
1988年 | 1篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1977年 | 2篇 |
1976年 | 3篇 |
1975年 | 4篇 |
1974年 | 1篇 |
1972年 | 2篇 |
1967年 | 1篇 |
1934年 | 1篇 |
1930年 | 2篇 |
排序方式: 共有628条查询结果,搜索用时 15 毫秒
121.
Evgenij V. Zarudnitskii Aleksandr A. Yurchenko Anatolij S. Merkulov Marina G. Semenova Aleksandr M. Pinchuk Andrej A. Tolmachev 《Heteroatom Chemistry》2005,16(7):648-655
The reaction of phosphorus(III) halides with 6‐substituted imidazo[2,1‐b]thiazoles in the presence of bases proceeds regioselectively and affords 5‐phosphinoimidazo[2,1‐b]thiazoles, useful synthons for the preparation of various P(III) and P(V) derivatives. 5‐Phosphinoimidazo[2,1‐b]thiazoles are selectively alkylated at the phosphorus or heterocyclic nitrogen atom, depending on the alkylating agent. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:648–655, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20166 相似文献
122.
Michiel E. Hochstenbach Andrej Muhič Bor Plestenjak 《Linear algebra and its applications》2012,436(8):2725-2743
We present several transformations that can be used to solve the quadratic two-parameter eigenvalue problem (QMEP), by formulating an associated linear multiparameter eigenvalue problem. Two of these transformations are generalizations of the well-known linearization of the quadratic eigenvalue problem and linearize the QMEP as a singular two-parameter eigenvalue problem. The third replaces all nonlinear terms by new variables and adds new equations for their relations. The QMEP is thus transformed into a nonsingular five-parameter eigenvalue problem. The advantage of these transformations is that they enable one to solve the QMEP using existing numerical methods for multiparameter eigenvalue problems. We also consider several special cases of the QMEP, where some matrix coefficients are zero 相似文献
123.
P. M. Polestshuk P. I. Dem’yanov V. S. Petrosyan 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2009,83(11):1913-1923
Density functional theory was used to study the structure of various isomers of (Me2Cu)Li (1), (Me2Cu)Cu (2), (Me2Cu)Li · 2Me2O (3), and (Me2Cu)Cu · 2Me2S (4) in the gas phase. Isomers of 1 and 3 were shown to be typical cuprates, whereas isomers of 2 and 4 should rather be treated as unsolvated and solvated methylcopper dimers, respectively. The reasons for the difference between
structures 2, 4 and 1, 3 were considered. The energies of solvation of 1 by two dimethyl ether molecules (∼34 kcal/mol) and of 2 by two dimethyl sulfide molecules (∼36 kcal/mol) and the dissociation energies of all the compounds to the dimethylcuprate
anion and the corresponding cation were calculated. The energies of solvation of 1 and 2 being almost equal, the transformation of 2 into 4 decreased the dissociation energy much more substantially than the transformation of 1 into 3. 相似文献
124.
Anab initio crystal orbital method is used to calculate the energies of an infinite chain of H atoms and of linear arrangements of H2 molecules with different interatomic distances. The H2 arrangements are not stable in respect to isolated molecules. The cohesive energy of an optimized arrangement of H atoms chain is 0.0354 a.u. 相似文献
125.
Andrej I. Dementev Nikolaj G. Rambidi Vladimir Y.A. Simkin Igor A. Topol Nikolaj F. Stepanov Boris I. Zhilinskii 《Journal of Molecular Structure》1980
The potential surface for the boron(III) oxide (B2O3) ground state has been calculated in restricted HF approximation with a minimal STO—3G basis set. The equilibrium geometry has C2v symmetry; the corresponding structural parameters are as follows: r(Oi—B1)= 1.241 Å; r(Bi—O)= 1.341 Å ; ∠B1QB2 = 142° and ǒO1B1O = 177°. Calculations were also carried out using the SCF-Xα approach for two configurations of B2O3 with C2v and D∞h symmetry. 相似文献
126.
127.
128.
Andrej Ule 《Acta Analytica》2004,19(33):9-30
I analyze some classical solutions of the skeptical argument and some of their week points (especially the contextualist solution).
First I have proposed some possible improvement of the contextualist solution (the introduction of the explicit-implicit belief
and knowledge distinction beside the differences in the relevance of some counter-factual alternatives). However, this solution
does not block too fast jumps of the everyday context (where empirical knowledge is possible) into skeptical context (where
empirical knowledge is impossible). Then I analyze some formal analogies between some modal arguments on the contingency of
empirical facts (and the world as whole) and the skeptical arguments against empirical knowledge. I try to show that the skeptical
conclusion “Empirical knowledge does not exist” is logically coherent with the thesis that they are empirical facts and that
we have true belief on them. In order to do that without contradictions I have to accept a non-classical definition of knowledge:
S knows that p:= S is not justified to allow that non-p. Knowledge and justified allowance function here as some pseudo-theoretical
concepts which allow only some partial and conditional definitions by some “empirical” terms and logical conditions. 相似文献
129.
130.
We formulate coordinate-free conditions for identifying all the symmetry classes of the elasticity tensor and prove that these conditions are both necessary and sufficient. Also, we construct a natural coordinate system of this tensor without the a priory knowledge of the symmetry axes. 相似文献