全文获取类型
收费全文 | 1798篇 |
免费 | 16篇 |
国内免费 | 26篇 |
专业分类
化学 | 927篇 |
晶体学 | 2篇 |
力学 | 29篇 |
数学 | 535篇 |
物理学 | 347篇 |
出版年
2016年 | 14篇 |
2015年 | 11篇 |
2014年 | 20篇 |
2013年 | 69篇 |
2012年 | 57篇 |
2011年 | 56篇 |
2010年 | 47篇 |
2009年 | 37篇 |
2008年 | 51篇 |
2007年 | 59篇 |
2006年 | 64篇 |
2005年 | 57篇 |
2004年 | 54篇 |
2003年 | 50篇 |
2002年 | 54篇 |
2001年 | 37篇 |
2000年 | 29篇 |
1999年 | 30篇 |
1998年 | 34篇 |
1997年 | 35篇 |
1996年 | 39篇 |
1995年 | 33篇 |
1994年 | 37篇 |
1993年 | 23篇 |
1992年 | 31篇 |
1991年 | 22篇 |
1990年 | 26篇 |
1989年 | 21篇 |
1988年 | 18篇 |
1987年 | 29篇 |
1986年 | 23篇 |
1985年 | 44篇 |
1984年 | 23篇 |
1983年 | 21篇 |
1982年 | 28篇 |
1981年 | 50篇 |
1980年 | 42篇 |
1979年 | 29篇 |
1978年 | 31篇 |
1977年 | 44篇 |
1976年 | 45篇 |
1975年 | 36篇 |
1974年 | 37篇 |
1973年 | 43篇 |
1972年 | 18篇 |
1971年 | 14篇 |
1970年 | 14篇 |
1969年 | 15篇 |
1968年 | 27篇 |
1967年 | 13篇 |
排序方式: 共有1840条查询结果,搜索用时 15 毫秒
1.
The extended Airy kernel describes the space-time correlation functions for the Airy process, which is the limiting process for a polynuclear growth model. The Airy functions themselves are given by integrals in which
the exponents have a cubic singularity, arising from the coalescence of two saddle points in an asymptotic analysis. Pearcey
functions are given by integrals in which the exponents have a quartic singularity, arising from the coalescence of three
saddle points. A corresponding Pearcey kernel appears in a random matrix model and a Brownian motion model for a fixed time. This paper derives an extended Pearcey kernel by scaling the Brownian motion model at several times, and a system of partial differential equations whose solution determines
associated distribution functions. We expect there to be a limiting nonstationary process consisting of infinitely many paths,
which we call the Pearcey process, whose space-time correlation functions are expressible in terms of this extended kernel. 相似文献
2.
Harold Steinacker 《Communications in Mathematical Physics》1998,192(3):687-706
We study irreducible unitary representations of U
q
(SO(2,1)) and U
q
(SO(2,?3)) for q a root of unity, which are finite dimensional. Among others, unitary representations corresponding to all classical one-particle
representations with integral weights are found for , with M being large enough. In the “massless” case with spin bigger than or equal to 1 in 4 dimensions, they are unitarizable only
after factoring out a subspace of “pure gauges” as classically. A truncated associative tensor product describing unitary
many-particle representations is defined for .
Received: 27 November 1996 / Accepted: 28 July 1997 相似文献
3.
Harold A. Scheraga 《International journal of quantum chemistry》1992,42(5):1529-1536
Various methods are used to surmount the multiple-minima problem that is encountered in the multidimensional conformational energy surface of a polypeptide. A summary is given here of two of these methods: (i) The build-up procedure that is modified to include statistical data on the positional frequencies of occurrence of amino acid residues along the chain, and (ii) the diffusion equation method that smoothes out the potential surface, leaving only the potential well containing the global minimum. 相似文献
4.
Parkansky N. Boxman R.L. Goldsmith S. Rosenberg Yu. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1997,25(4):543-547
Electrical contact lifetime is often directly determined by arc erosion. A method for reducing are erosion was developed consisting of injecting from an external current source an additional electrical current flowing parallel to the contact surface. This method was examined in three are environments using the additional transverse electrical current with a density less than 1 A/mm2: 1) automobile ignition contacts; 2) pulsed air arc; and 3) low pressure (P=100 mTorr) arc in nitrogen, SEM and X-ray examination showed that application of a transverse current in a contact during arcing changed the phase composition and microstructure of the contact surface. Under optimal conditions, the microstructure which is formed is significantly more erosion resistant than without the transverse current injection 相似文献
5.
An algorithm has been developed for packing polypeptide chains by energy minimization subject to regularity conditions, in which regularity is maintained without the addition of pseudoenergy terms by defining the energy as a function of appropriately chosen independent variables. The gradient of the energy with respect to the independent variables is calculated analytically. The speed and efficiency of convergence of the algorithm to a local energy minimum are comparable to those of existing algorithms for minimizing the energy of a single polypeptide chain. The algorithm has been used to reinvestigate the minimum-energy regular structures of three-stranded (L -Ala)8, three-stranded (L -Val)6, five-stranded (L -Ile)6, and the regular and truncated three-stranded (Gly-L -Pro-L -Pro)4 triple helices. Local minima with improved packing energies, but with essentially unchanged geometrical properties, were obtained in all cases. The algorithm was also used to reinvestigate the structures proposed previously for the I and II forms of crystalline silk fibroin. The silk II structure was reproduced with slightly improved packing and little other change. The orthorhombic silk I structure showed more change and considerably improved packing energy, but the new regular monoclinic silk I structure had considerably higher energy. The results support the structure proposed previously for silk II and the orthorhombic structure, but not the monoclinic structure proposed for silk I. © 1994 by John Wiley & Sons, Inc. 相似文献
6.
7.
8.
A necessary and sufficient condition for regularity of the
-Neumann operator on (0,q)-forms in a smooth bounded pseudoconvex domain in Cn is that the orthogonal projections onto
-closed forms of degrees (0,q−1), (0,q), and (0,q+1) all be regular.
The first author partially supported by NSF Grant DMS-8701038 相似文献
9.
Dimitrakakis E Haberhauer-Troyer C Abe Y Ochsenkühn-Petropoulou M Rosenberg E 《Analytical and bioanalytical chemistry》2004,379(5-6):842-848
The use of solid-phase microextraction (SPME) with gas chromatography coupled to microwave-induced plasma atomic-emission detection (GC–MIP-AED) is described for selenite [Se(IV)] speciation. Aqueous standards were derivatised with sodium tetraethyl- or tetrapropylborate and extracted by SPME. Headspace extraction of the ethyl and propyl derivatives was studied. Relevant experimental conditions were optimised, including conditions for derivatisation and extraction and those of gas chromatographic analysis. The limits of detection achieved for headspace sampling of derivatised Se(IV) were in the low ng mL–1 range for both ethylation and propylation. When the method was applied to analysis of selenite in selenised yeast reference material results were in good agreement with the indicated values. 相似文献
10.
J. Griffith R. J. Rosenberg O. Díaz-Rizo E. González 《Journal of Radioanalytical and Nuclear Chemistry》1996,213(1):71-78
Thermal and epithermal non-destructive activation analyses have been performed on samples of final molasses from 14 different sugar factories, covering the most important regions in Cuba. From the first measurement after irradiation at the Triga Mark reactor (VTT), the concentration of more than 15 elements is reported. The almost constant elemental composition shows that they can be used equally for different purposes as animal foodstuff and for the manufacture of biotechnological products. This work is part of a research project developed in order to establish a complete characterization of Cuban sugar molasses. 相似文献