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991.
Using a geometric model to study the structure of hadrons, baryons having one, two and three heavy quarks have been studied
here. The study reveals diquark structure in baryons with one and two heavy quarks but not with three heavy identical quarks. 相似文献
992.
北大西洋海温与500hPa月平均环流的若干统计特征 总被引:1,自引:0,他引:1
章新平 《新疆大学学报(理工版)》1988,(4)
前言大西洋是仅次于太平洋的水体,它的存在与热变化通过中纬度西风带环流可宜接影响到我国西部地区的天气和气候。过去很长一段时间,在研究海洋对我国天气气候的影响时,人们总是把注意力放在太平洋和印度洋,而对大西洋的研究甚少。近年来,随着海气相互作用研究工作的深入以及资料条件的改善,人们开始注意到大西洋对我国天气气候的影响。本文利用统计关系为基 相似文献
993.
B. T. Meggitt 《Optics & Laser Technology》1989,21(5)
A novel optical technique is described for making geometrical measurements on silica starter tubes. The measurement takes place in an air medium and uses a collimated source and spatial filtering to image the set of transmitted rays onto a CCTV system. An analysis relates this line structure observed to the geometry of the starter tube. 相似文献
994.
Conformational isomerism of 2,2-dithiodi(2-methyl-2,3-dihydro-1,4-thiazino[2,3,4-i,j]quinolinium) has been studied by semiempirical MNDO and AM1 methods. Six symmetrical and unsymmetrical stationary states have been found. Optimum intramolecular rotations around single bonds have been considered. The possibility of the inversion of the reaction centers in nucleophilic and electrophilic reactions depending on the conformational state of the molecule has been shown. The spatial structure of one of the conformers found is similar to that typical of (–)-cystine. The observed constancy of some geometric and electronic parameters makes it possible to study the principal physicochemical properties of dithiazinoquinolinium compounds by the most sophisticatedab initio methods using small model structures, which are constructed by taking into account the variability of other geometric parameters, as an example.Deceased.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2359–2364, December, 1995.The work was supported by the Russian Foundation for Basic Research (Project No. 93-03-18400). 相似文献
995.
We present a log-barrier based algorithm for linearly constrained convex differentiable programming problems in nonnegative variables, but where the objective function may not be differentiable at points having a zero coordinate. We use an approximate centering condition as a basis for decreasing the positive parameter of the log-barrier term and show that the total number of iterations to achieve an -tolerance optimal solution isO(|log()|)×(number of inner-loop iterations). When applied to then-variable dual geometric programming problem, this bound becomesO(n
2
U/), whereU is an upper bound on the maximum magnitude of the iterates generated during the computation.The authors gratefully acknowledge very constructive and insightful comments and suggestions from the two anonymous referees and the correspondence from A. V. Fiacco (Ref. 1). 相似文献
996.
This paper provides two different functions for quantifying geometric chirality. Both are based on Euclidean distances between enantiomer atoms and the best associated RMS, but, depending on the function, atoms are paired without or with constraint. In the first, the best match between the enantiomer atoms is sought by means of a completely new method in which one enantiomer is fitted onto a spline approximation of the other. This method reestablishes the continuity between similarity and dissimilarity, broken in discrete space by atom-per-atom shape recognition treatments. In the second, each enantiomer atom is paired with its mirror image and only the mirror location is optimized. Congruity-based chirality measures are grouped into two classes according to whether the discrimination function between the chiral object and the reference object takes some constraint into account (second class) or does not (first class). In this paper, our constrained or unconstrained chirality function is compared with the continuous chirality measure (second class). It is inferred that only chirality scales of the same class can be correlated. 相似文献
997.
998.
999.
M. Raghavachari 《Mathematical Programming》1977,13(1):156-166
LetD
p
be the set of all doubly stochastic square matrices of orderp i.e. the set of allp × p matrices with non-negative entries with row and column sums equal to unity. The permanent of ap × p matrixA = (a
ij
) is defined byP(A) =
Sp
II
i=1
p
a
i(i)
whereS
p
is the symmetric group of orderp. Van der Waerden conjectured thatP(A) p !/p
p
for all A AD
p
with equality occurring if and only ifA = J
p
, whereJ
p
is the matrix all of whose entries are equal to 1/p.The validity of this conjecture has been shown for a few values ofp and for generalp under certain assumptions. In this paper the problem of finding the minimum of the permanent of a doubly stochastic matrix has been formulated as a reversed geometric program with a single constraint and an equivalent dual program is given. A related problem of reversed homogeneous posynomial programming problem is also studied. 相似文献
1000.
The Euclidean matching problem consists in partitionning a cloud ofn points inton/2 pairs such that the sum of the euclidean distances between the endpoints of each couple is minimized, resp. maximized.In this paper the thermodynamically inspired approach of simulated annealing is applied to find good approximations to large scale problems of the above kind. Also the asymptotic behaviour of random euclidean matching problems is studied, in particular computational results on the rate of convergence towards the asymptote are given.
Zusammenfassung Euklidische Matching-Probleme bestehen darin, eine ausn Punkten bestehende Wolke derart inn/2 Paare zu partitionieren, daß die Summe der Abstände zwischen den Endpunkten der Paare minimal bzw. maximal wird. Vorliegende Arbeit beschreibt die Anwendung der simulierten Abkühlung, eines durch die Thermodynamik inspirierten Verfahrens, zur Lösung großer derartiger Probleme. Zudem wird das asymptotische Verhalten zufälliger euklidischer Matching-Probleme studiert, insbesondere werden numerische Angaben zur Konvergenzrate gegen die Asymptote gegeben.相似文献