全文获取类型
收费全文 | 3806篇 |
免费 | 41篇 |
国内免费 | 24篇 |
专业分类
化学 | 2547篇 |
晶体学 | 41篇 |
力学 | 56篇 |
数学 | 558篇 |
物理学 | 669篇 |
出版年
2024年 | 12篇 |
2023年 | 39篇 |
2022年 | 71篇 |
2021年 | 113篇 |
2020年 | 118篇 |
2019年 | 147篇 |
2018年 | 126篇 |
2017年 | 86篇 |
2016年 | 145篇 |
2015年 | 131篇 |
2014年 | 156篇 |
2013年 | 204篇 |
2012年 | 242篇 |
2011年 | 267篇 |
2010年 | 175篇 |
2009年 | 116篇 |
2008年 | 246篇 |
2007年 | 242篇 |
2006年 | 214篇 |
2005年 | 191篇 |
2004年 | 148篇 |
2003年 | 120篇 |
2002年 | 99篇 |
2001年 | 47篇 |
2000年 | 33篇 |
1999年 | 40篇 |
1998年 | 36篇 |
1997年 | 22篇 |
1996年 | 31篇 |
1995年 | 23篇 |
1994年 | 29篇 |
1993年 | 15篇 |
1992年 | 11篇 |
1991年 | 11篇 |
1989年 | 9篇 |
1988年 | 11篇 |
1986年 | 7篇 |
1985年 | 6篇 |
1984年 | 11篇 |
1983年 | 9篇 |
1982年 | 10篇 |
1981年 | 6篇 |
1980年 | 9篇 |
1979年 | 8篇 |
1977年 | 5篇 |
1976年 | 12篇 |
1975年 | 11篇 |
1973年 | 8篇 |
1972年 | 4篇 |
1954年 | 5篇 |
排序方式: 共有3871条查询结果,搜索用时 0 毫秒
11.
Vladimir Müller Pavel Pták Josef Tkadlec 《International Journal of Theoretical Physics》1992,31(5):843-854
LetL be a concrete (=set-representable) quantum logic. Letn be a natural number (or, more generally, a cardinal). We say thatL admits intrinsic coverings of the ordern, and writeL
C
n
, if for any pairA, BL we can find a collection {C
i
iI}, where cardI<n andC
i
L for anyiI, such thatA B=
il
C
i
. Thus, in a certain sense, ifLC
n
, then the rate of noncompatibility of an arbitrary pairA,BL is less than a given numbern. In this paper we first consider general and combinatorial properties of logics ofC
n
and exhibit typical examples. In particular, for a givenn we construct examples ofL
C
n+1\C
n
. Further, we discuss the relation of the classesC
n
to other classes of logics important within the quantum theories (e.g., we discover the interesting relation to the class of logics which have an abundance of Jauch-Piron states). We then consider conditions on which a class of concrete logics reduce to Boolean algebras. We conclude with some open questions. 相似文献
12.
The atmospherically and technologically very important process of brine rejection from freezing salt solutions is investigated with atomic resolution using molecular dynamics simulations. The present calculations allow us to follow the motion of each water molecule and salt ion and to propose a microscopic mechanism of brine rejection, in which a fluctuation (reduction) of the ion density in the vicinity of the ice front is followed by the growth of a new ice layer. The presence of salt slows down the freezing process, which leads to the formation of an almost neat ice next to a disordered brine layer. 相似文献
13.
We investigate the properties of the path integral over reparametrizations (or the boundary value of the Liouville field in string theory). Discretizing the path integral, we apply the Metropolis–Hastings algorithm to numerical simulations of a proper (subordinator) stochastic process and find that typical trajectories are not Brownian but rather have discontinuities of the type of Lévy's flights. We study a fractal structure of these trajectories and show that their Hausdorff dimension is zero. We confirm thereby previous results on QCD scattering amplitudes by analytical and numerical calculations. We also perform Monte Carlo simulations of the path integral over reparametrization in the effective string ansatz for a circular Wilson loop and discuss their subtleties associated with the discretization of Douglas' functional. 相似文献
14.
Zusammenfassung Einige Änderungen an der Apparatur zur Stickstoffschnellbestimmung nachMerz wurden vorgenommen. Dadurch wird erreicht, daß zwischen den einzelnen Verbrennungen Sauerstoff das Verbrennungsrohr durchspült und vor dem Reduktionsrohr nach außen tritt. Der Verbrennungsraum ist daher bereits zu Beginn jeder Analyse mit Sauerstoff gefüllt, wodurch günstigere Bedingungen für die schlagartige Verbrennung erzielt werden. Der Umbau der von der Firma Heraeus gelieferten Apparatur und die Herstellung eines Oxydationskatalysators (Kobaltoxid-Wolframoxid) werden beschrieben.
Contribution to the rapid nitrogen determination according to merz
Summary The apparatus for rapid nitrogen determination according toMerz has been modified. Between each two combustions, oxygen is flushed through the combustion tube and is vented before the reduction tube. Therefore, at the beginning of each analysis, the combustion chamber is filled with oxygen, providing a more favorable atmosphere for the rapid ignition. The alterations in the Hereaus apparatus and the preparation of an oxidation catalyst (cobalt oxide and tungsten oxide) are described.相似文献
15.
The problem of obtaining the matrix elements of Hartree-Fock Hamiltonians for alkanes using the EO method is considered. It has been shown that the data on the electronic structure of diamond together witht 1/e splitting in the neopentane photoelectron spectrum are helpful to produce such EO method parameter scale which involves even “through space” interactions. In terms of the EO method the photoelectron spectra of propane, butane, isobutane, and neopentane are interpreted. The valence band structure of polyethylene in analytical form is obtained. 相似文献
16.
17.
Kyril Dimov Pavel Pavlov 《Journal of polymer science. Part A, Polymer chemistry》1969,7(10):2775-2792
The possibility of obtaining modified cellulose products by reacting cellulose xanthogenate in solutions containing oxidizers and acrylonitrile was studied. The ability of the cellulose xanthogenate–hydrogen peroxide redox system to initiate graft copolymerization of acrylonitrile on the cellulose was demonstrated. The influence of various factors on the processes was investigated. An attempt was made to clarify the nature of the reactions involved. 相似文献
18.
Zusammenfassung In der vorliegenden Arbeit wird die Herstellung des Chlorids (1), von Estern (2a, 2b), Amiden (3a-3g), des N-Hydroxyamids (3h) und Hydrazids (3i) der 1-Phenyl-6-azauracil-5-carbonsäure beschrieben. 相似文献
19.
20.
Plasma Chemistry and Plasma Processing - 相似文献