全文获取类型
收费全文 | 777篇 |
免费 | 19篇 |
国内免费 | 2篇 |
专业分类
化学 | 517篇 |
晶体学 | 4篇 |
力学 | 11篇 |
数学 | 125篇 |
物理学 | 141篇 |
出版年
2023年 | 8篇 |
2022年 | 24篇 |
2021年 | 27篇 |
2020年 | 35篇 |
2019年 | 33篇 |
2018年 | 22篇 |
2017年 | 16篇 |
2016年 | 22篇 |
2015年 | 18篇 |
2014年 | 23篇 |
2013年 | 49篇 |
2012年 | 54篇 |
2011年 | 61篇 |
2010年 | 36篇 |
2009年 | 20篇 |
2008年 | 33篇 |
2007年 | 31篇 |
2006年 | 47篇 |
2005年 | 53篇 |
2004年 | 23篇 |
2003年 | 19篇 |
2002年 | 24篇 |
2001年 | 9篇 |
2000年 | 4篇 |
1999年 | 8篇 |
1998年 | 10篇 |
1997年 | 9篇 |
1996年 | 2篇 |
1995年 | 7篇 |
1994年 | 4篇 |
1993年 | 5篇 |
1992年 | 4篇 |
1990年 | 5篇 |
1989年 | 4篇 |
1985年 | 4篇 |
1984年 | 4篇 |
1982年 | 2篇 |
1978年 | 2篇 |
1976年 | 2篇 |
1975年 | 4篇 |
1973年 | 3篇 |
1972年 | 2篇 |
1969年 | 3篇 |
1955年 | 2篇 |
1937年 | 2篇 |
1936年 | 1篇 |
1935年 | 2篇 |
1930年 | 1篇 |
1926年 | 1篇 |
1925年 | 1篇 |
排序方式: 共有798条查询结果,搜索用时 0 毫秒
781.
Vladislav B. Kovchegov 《The Journal of mathematical sociology》2013,37(4):315-332
Given is a review of the substantial theories of cognitivist's trend and also of static and dynamic models of group structures that are based on them. A model of human institutiosn is constructed that explains the origin of balanced structures. This model is realized by a system of locally interacting automatons which are connected by a system of relations and endowed with the ability to react. 相似文献
782.
An n-dimensional submanifold X of a projective space P
N
(C) is called tangentially degenerate if the rank of its Gauss mapping gamma;; X G(n, N) satisfies 0 < rank < n. The authors systematically study the geometry of tangentially degenerate submanifolds of a projective space P
N
(C). By means of the focal images, three basic types of submanifolds are discovered: cones, tangentially degenerate hypersurfaces, and torsal submanifolds. Moreover, for tangentially degenerate submanifolds, a structural theorem is proven. By this theorem, tangentially degenerate submanifolds that do not belong to one of the basic types are foliated into submanifolds of basic types. In the proof the authors introduce irreducible, reducible, and completely reducible tangentially degenerate submanifolds. It is found that cones and tangentially degenerate hypersurfaces are irreducible, and torsal submanifolds are completely reducible while all other tangentially degenerate submanifolds not belonging to basic types are reducible. 相似文献
783.
Aleksey A. Yaremchenko Vladislav V. Kharton Evgeny N. Naumovich Alim A. Vecher 《Journal of Solid State Electrochemistry》1998,2(3):146-149
The minimum concentration of niobium to stabilize the fluorite-type f.c.c. phase in the Bi2O3–Nb2O5 oxide system at temperatures below 996 K was ascertained to be about 10 mol%. Thermal expansion, electrical conductivity
and crystal lattice parameters of the Bi(Nb)O1.5+δ solid solutions decrease with increasing niobium content. Thermal expansion coefficients were calculated from the dilatometric
data to be (10.314.5)×10−6 K−1 at temperatures in the range 300–700 K and (17.526.0)×10−6 K−1 at 700–1100 K. The conductivity of the Bi1−
x
Nb
x
O1.5+δ ceramics is predominantly ionic. The p-type electronic transference numbers of the Bi(Nb)O1.5+δ solid solutions in air were determined to be less than 0.1. Annealing at temperatures below 900 K results in a sharp decrease
in conductivity of the Bi1−
x
Nb
x
O1.5+δ ceramics.
Received: 18 August 1997 / Accepted: 20 October 1997 相似文献
784.
Holger F. Bettinger Angela D. Rabuck Gustavo E. Scuseria Nai-Xing Wang Vladislav A. Litosh Rajesh K. Saini W. E. Billups 《Chemical physics letters》2002,360(5-6):509-514
The thermolysis of C60H2 to yield C60 and H2 was studied by hybrid density functional theory (B3LYP/6-311G**//B3LYP/3-21G). The concerted loss of dihydrogen requires an activation energy of 92 kcalmol−1 atT=452 K. An alternative radical mechanism, which is first order in the C60H2 concentration, has an activation energy at 452 K of only 61 kcalmol−1. Monitoring of the C60H2 decomposition in 1,2-dichloro-[D4]-benzene solution by NMR spectroscopy indicates a pseudo first-order reaction with an activation energy of 61.38±2.35 kcalmol−1. 相似文献
785.
P. Auban-Senzier C. Lenoir P. Batail D. Jérome S. Tomić 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,7(4):529-532
An investigation of the different contributions leading to charge localization in a 1/2 or 1/4 filled band 1D conductor has
been conducted through a study of transport properties in the solid solution [(TMTSF)1-x (TMTTF) x]2ReO4. The existence of an ordering transition of the anions allows to identify two contributions to the electronic potential with
wave vector 4kF. A dominant on-site 4kF potential besides the bond contribution is revealed when Umklapp scattering is pertinent via the weakening of the localization arising at the (0, 1/2, 1/2) anion ordering which is stabilized under pressure in the compound
[(TMTSF) 0.5 (TMTTF)0.5]2ReO4
at variance with the enhancement of localization observed in the homomolecular (TMTTF)2ReO 4 material.
Received: 13 May 1998 / Revised: 8 July 1998 / Accepted: 9 July 1998 相似文献
786.
Vladislav Kargin 《Journal of statistical physics》2014,157(1):70-83
The paper provides a new integral formula for the largest Lyapunov exponent of Gaussian matrices, which is valid in the real, complex and quaternion-valued cases. This formula is applied to derive asymptotic expressions for the largest Lyapunov exponent when the size of the matrix is large and compare the Lyapunov exponents in models with a spike and no spikes. 相似文献
787.
788.
Monika Kovačević Lidija Barišić Rosana Ribić Vesna Petrović Peroković Srđanka Tomić Vladimir Rapić 《应用有机金属化学》2012,26(2):74-79
Bacterial adhesion, mediated through interaction of bacterial lectins with carbohydrate structures presented on the surface of the host cells, is a prerequisite for infection. Anti‐adhesion therapy, based on the inhibition of lectins by suitable carbohydrates, has been considered as a weapon for the combat of microbial diseases. Structural alteration of aglycon portions of mannose derivatives strongly influences their inhibitory potency toward type 1 fimbriated Escherichia coli. Thus several conjugates of mannose‐containing ferrocene aglycon moieties were synthesized and tested. The novel ferrocene conjugates 10, 12 and 14 were obtained by esterification of O‐mannosylated propionic acid 1 with ferrocene alcohols R‐Fn‐(CH2)n‐OH (Fn = 1,1'‐ferrocenylene; 2, n = 1, R = COOMe; 7, n = 1, R = NHBoc; 8, n = 2, R = H) in the presence of Boc2O/DMAP with subsequent debenzylation of the intermediate O‐protected esters. Performed hemagglutination inhibitory tests showed that the examined bioorganometallics exhibit better inhibitory activity than known inhibitor methyl α‐d ‐mannoside. Thus ferrocene–mannose conjugate 14 with the dimethylene spacer between ferrocene core and chiral linker displayed the best inhibitory efficiency. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
789.
S. Tomić D. Grgičin T. Ivek T. Vuletić S. Dolanski Babić R. Podgornik 《Physica B: Condensed Matter》2012,407(11):1958-1963
We overview the study of biopolyelectrolytes by dielectric spectroscopy technique by primarily focusing on the case of repulsive regime of intersegment interactions mediated by univalent counterions. Two observed dielectric relaxations in 100 Hz–100 MHz frequency range due to diffusive motion of counterions are related to polyelectrolyte structural properties: the high frequency mode probes the structural organization of the polyion network in solution, while the low frequency mode is correlated with single polyion conformational properties. Open issues are highlighted and prospects for further research with polyvalent counterions are designated in order to study the crossover from repulsive to attractive regime of intersegment interactions. 相似文献
790.
Vladimir A. Zubkov Alexander V. Yakimansky Svetlana E. Bogdanova Vladislav V. Kudryavtsev 《Macromolecular theory and simulations》1994,3(2):497-509
Semiempirical PM-3 calculations of the mechanisms of the decomposition of oxazole and maleimide have been carried out. It has been shown that thermal decomposition of the considered heterocycles proceeds via a consecutive breaking of two ring bonds, the breaking of the second bond being the rate-determining step. Both an activation barrier of heterocycle decomposition and its dissociation energy (ED) can be used as a measure of heterocycle thermal stability. The correlation between ED values of azole and imide containing model compounds and the initial degradation temperatures of corresponding heteropolymers makes it possible to clarify some essential features of the thermal degradation of polyazoles, polybenzazoles and polyimides. 相似文献