全文获取类型
收费全文 | 12226篇 |
免费 | 471篇 |
国内免费 | 93篇 |
专业分类
化学 | 8244篇 |
晶体学 | 103篇 |
力学 | 303篇 |
综合类 | 1篇 |
数学 | 1931篇 |
物理学 | 2208篇 |
出版年
2023年 | 81篇 |
2022年 | 112篇 |
2021年 | 214篇 |
2020年 | 232篇 |
2019年 | 261篇 |
2018年 | 175篇 |
2017年 | 166篇 |
2016年 | 411篇 |
2015年 | 313篇 |
2014年 | 355篇 |
2013年 | 675篇 |
2012年 | 697篇 |
2011年 | 781篇 |
2010年 | 500篇 |
2009年 | 449篇 |
2008年 | 676篇 |
2007年 | 721篇 |
2006年 | 589篇 |
2005年 | 649篇 |
2004年 | 536篇 |
2003年 | 433篇 |
2002年 | 419篇 |
2001年 | 216篇 |
2000年 | 192篇 |
1999年 | 110篇 |
1998年 | 121篇 |
1997年 | 129篇 |
1996年 | 144篇 |
1995年 | 110篇 |
1994年 | 119篇 |
1993年 | 136篇 |
1992年 | 117篇 |
1991年 | 115篇 |
1990年 | 99篇 |
1989年 | 87篇 |
1988年 | 65篇 |
1987年 | 66篇 |
1986年 | 88篇 |
1985年 | 126篇 |
1984年 | 119篇 |
1983年 | 99篇 |
1982年 | 79篇 |
1981年 | 83篇 |
1980年 | 82篇 |
1979年 | 77篇 |
1978年 | 80篇 |
1976年 | 50篇 |
1975年 | 64篇 |
1974年 | 64篇 |
1973年 | 59篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
Jan Annaert Griselda Deelstra Michèle Vanmaele 《Insurance: Mathematics and Economics》2007,41(3):299-316
In this paper, we elaborate a formula for determining the optimal strike price for a bond put option, used to hedge a position in a bond. This strike price is optimal in the sense that it minimizes, for a given budget, either Value-at-Risk or Tail Value-at-Risk. Formulas are derived for both zero-coupon and coupon bonds, which can also be understood as a portfolio of bonds. These formulas are valid for any short rate model that implies an affine term structure model and in particular that implies a lognormal distribution of future zero-coupon bond prices. As an application, we focus on the Hull-White one-factor model, which is calibrated to a set of cap prices. We illustrate our procedure by hedging a Belgian government bond, and take into account the possibility of divergence between theoretical option prices and real option prices. This paper can be seen as an extension of the work of Ahn and co-workers [Ahn, D., Boudoukh, J., Richardson, M., Whitelaw, R., 1999. Optimal risk management using options. J. Financ. 54, 359-375], who consider the same problem for an investment in a share. 相似文献
33.
Upon irradiation, cyclic enol ethers such as 1-methoxy-cyclopentene (4) mainly add across the cyano group of benzonitrile (1), under formation of 2-azabutadienes of an imidoester type. This is in agreement with the so-called Δ G-correlation which was reported earlier (ref. 5 and 6). 4-Phenyloxazole (9) is formed from 1 and 1,3-dioxole (5) probably by a similar photochemical process followed by electrocyclic ring opening and hydrolysis. The low yield of the latter photoreaction and the almost exergonic electron transfer between 5 and 1 may point to back electron transfer as the main energy wasting process. From 1 and 2,3-dihydrido-furan (2) only the ortho cycloadduct 6 has been isolated in low yields. 相似文献
34.
35.
36.
37.
Jan P. Boroński 《Topology and its Applications》2007,154(18):3156-3166
A set (or a collection of sets) contained in the Euclidean space Rm is symmetric if it is invariant under the antipodal map. Given a symmetric unicoherent polyhedron X (like an n-dimensional cube or a sphere) and an odd real function f defined on vertices of a certain symmetric triangulation of X, we algorithmically construct a connected symmetric separator of X by choosing a subcollection of the triangulation. Each element of the subcollection contains the vertices v and u such that f(v)f(u)?0. 相似文献
38.
What features characterize complex system dynamics? Power laws and scale invariance of fluctuations are often taken as the hallmarks of complexity, drawing on analogies with equilibrium critical phenomena. Here we argue that slow, directed dynamics, during which the system's properties change significantly, is fundamental. The underlying dynamics is related to a slow, decelerating but spasmodic release of an intrinsic strain or tension. Time series of a number of appropriate observables can be analyzed to confirm this effect. The strain arises from local frustration. As the strain is released through “quakes,” some system variable undergoes record statistics with accompanying log‐Poisson statistics for the quake event times. We demonstrate these phenomena via two very different systems: a model of magnetic relaxation in type II superconductors and the Tangled Nature model of evolutionary ecology and show how quantitative indications of aging can be found. © 2004 Wiley Periodicals, Inc. Complexity 10: 49–56, 2004 相似文献
39.
Il Bong Jung Alan Lambert Jan Stochel 《Proceedings of the American Mathematical Society》2004,132(8):2291-2302
The concept of backward extension for subnormal weighted shifts is generalized to arbitrary subnormal operators. Several differences and similarities in these contexts are explored, with emphasis on the structure of the underlying measures.
40.
We perform three tests on our proposal to implement diffeomorphism invariance in the non-abelian D0-brane DBI action as a base-point independence constraint between matrix Riemann normal coordinate systems. First, we show that T-duality along an isometry correctly interchanges the potential and kinetic terms in the action. Second, we show that the method to impose base-point independence using an auxiliary dN2-dimensional nonlinear sigma model also works for metrics which are curved along the brane, provided a physical gauge choice is made at the end. Third, we show that without alteration this method is applicable to higher order in velocities. Testing specifically to order 4, we elucidate the range of validity of the symmetrized trace approximation to the non-abelian DBI action. 相似文献