全文获取类型
收费全文 | 18469篇 |
免费 | 118篇 |
国内免费 | 21篇 |
专业分类
化学 | 17399篇 |
晶体学 | 20篇 |
力学 | 125篇 |
数学 | 629篇 |
物理学 | 435篇 |
出版年
2013年 | 156篇 |
2012年 | 214篇 |
2011年 | 249篇 |
2010年 | 157篇 |
2008年 | 170篇 |
2007年 | 187篇 |
2006年 | 191篇 |
2005年 | 188篇 |
2004年 | 176篇 |
1987年 | 136篇 |
1985年 | 187篇 |
1984年 | 203篇 |
1980年 | 328篇 |
1979年 | 238篇 |
1978年 | 1042篇 |
1977年 | 801篇 |
1976年 | 232篇 |
1975年 | 123篇 |
1972年 | 128篇 |
1970年 | 130篇 |
1968年 | 209篇 |
1967年 | 175篇 |
1966年 | 221篇 |
1965年 | 255篇 |
1964年 | 229篇 |
1963年 | 176篇 |
1962年 | 347篇 |
1961年 | 168篇 |
1960年 | 219篇 |
1959年 | 209篇 |
1958年 | 206篇 |
1957年 | 153篇 |
1956年 | 236篇 |
1955年 | 227篇 |
1954年 | 165篇 |
1943年 | 162篇 |
1939年 | 162篇 |
1938年 | 174篇 |
1937年 | 230篇 |
1936年 | 215篇 |
1935年 | 231篇 |
1934年 | 185篇 |
1933年 | 250篇 |
1932年 | 136篇 |
1931年 | 140篇 |
1930年 | 216篇 |
1928年 | 154篇 |
1927年 | 153篇 |
1913年 | 127篇 |
1905年 | 130篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
Investment projects and businesses can be entered or exited at a cost, and the theory of real option teaches us how to find optimal activity levels that should trigger entry or exit. However, in practice, different managers or owners operate under different constraints and might apply different thresholds to the same business. We are interested in the hedging of the risk related to the cost of sub-optimal entry or exit. We introduce a new class of derivative products that can hedge this risk. The pricing of these derivatives involves the joint law of a Brownian excursion and its supremum, which is calculated thanks to Bessel processes-related distribution laws. 相似文献
2.
In this Note, we propose a finite element method with Lagrange multipliers in order to approximate contact problems with friction. The discretized normal and tangential constraints at the candidate contact interface are expressed by using continuous piecewise linear Lagrange multipliers in the saddle-point formulation. An optimal error estimate is established and several numerical studies corresponding to this choice of the discretized normal and tangential constraints are achieved. To cite this article: L. Baillet, T. Sassi, C. R. Acad. Sci. Paris, Ser. I 334 (2002) 917–922. 相似文献
3.
Laurent Gosse. 《Mathematics of Computation》2002,71(238):553-582
This paper investigates the behavior of numerical schemes for nonlinear conservation laws with source terms. We concentrate on two significant examples: relaxation approximations and genuinely nonhomogeneous scalar laws. The main tool in our analysis is the extensive use of weak limits and nonconservative products which allow us to describe accurately the operations achieved in practice when using Riemann-based numerical schemes. Some illustrative and relevant computational results are provided.
4.
If the Riemann–Christoffel tensor associated with a field of class of positive definite symmetric matrices of order three vanishes in a connected and simply connected open subset , then this field is the metric tensor field associated with a deformation of class of the set , uniquely determined up to isometries of . We establish here that the mapping defined in this fashion is continuous, for ad hoc metrizable topologies. To cite this article: P.G. Ciarlet, F. Laurent, C. R. Acad. Sci. Paris, Ser. I 335 (2002) 489–493. 相似文献
5.
A variational approach is proposed to study some properties of the adiabatic Holstein–Hubbard model which describes an assembly of fermionic charges interacting with a static atomic lattice. The sum of the electronic energy and the lattice elastic energy is proved to have minima with a many-polaron structure in a certain domain of model parameters. Our analytical work consists in expanding these energy minima from the zero electronic transfer limit which remarkably holds for a finite amplitude of the onsite Hubbard repulsion and for an unbounded lattice size. 相似文献
6.
J. Krause und F. Umland 《Fresenius' Journal of Analytical Chemistry》1989,335(7):791-795
Summary This paper presents some applications of cyclic voltammetry at the interface of two immiscible electrolyte solutions by means of an experimental set-up described in a former publication. When using special sample preparation good results are obtained for the determination of iodide and quinine in pharmaceutical products as well as for the determination of quinine in tonic water and dodecylsulfate in a tooth-salt.
Herrn Prof. Dr. Günther Tölg zum 60. Geburtstag gewidmet 相似文献
Herrn Prof. Dr. Günther Tölg zum 60. Geburtstag gewidmet 相似文献
7.
We prove that the generalized random walks associated to a root system R in and a nonnegative multiplicity function k defined on R, converge in distribution (if suitably normalized) to a Markov process with càdlàg trajectories and infinitesimal generator a differential-difference operator on which generalizes the usual Laplacian. To cite this article: L. Gallardo, L. Godefroy, C. R. Acad. Sci. Paris, Ser. I 338 (2004). 相似文献
8.
H. Moers H. Klewe-Nebenius G. Pfennig und H. J. Ache 《Fresenius' Journal of Analytical Chemistry》1987,329(2-3):361-366
Summary The adsorption of gaseous molecular iodine on clean silver surfaces proceeds in the first stage by dissociative chemisorption. After the formation of half a monolayer of chemisorbed iodine atoms the formation of silver iodide begins, which forms a very regular overlayer on top of the substrate. Both iodine species can be distinguished due to a difference in chemical shift of the M4N4, 5N4, 5-Auger transitions. After completion of this overlayer further iodine uptake is slowed down significantly. Above an overlayer thickness of about 10 nm a further progress of the reaction cannot be followed anymore due to the limited information depth of XPS. 相似文献
9.
R. Hefelmann P. Mann A. Aignan F. Filsinger und H. Amsel 《Fresenius' Journal of Analytical Chemistry》1902,41(1):66-68
Ohne Zusammenfassung 相似文献
10.
Thorsten Hamann Erin Osborne Heather L. Youngs Julie Misson Laurent Nussaume Chris Somerville 《Cellulose (London, England)》2004,11(3-4):279-286
We have used Affymetrix gene chips to measure the expression of 10 CESA and 29 CSL genes of Arabidopsis in different developmental stages or organs. These measurements reveal that many of the genes exhibit different levels of expression in the various organs. While several CESA genes are highly expressed in all the tissues examined, very few CSL genes approach such high levels of expression. This suggests that the CSL genes either encode enzymes for the synthesis of minor components of cell walls or are expressed only in specific cell types. The expression data also highlights the potential importance of the CESA genes for primary and secondary cell wall formation during different developmental stages and in the different organs examined. 相似文献