全文获取类型
收费全文 | 5983篇 |
免费 | 554篇 |
国内免费 | 463篇 |
专业分类
化学 | 231篇 |
晶体学 | 1篇 |
力学 | 968篇 |
综合类 | 136篇 |
数学 | 4692篇 |
物理学 | 972篇 |
出版年
2024年 | 9篇 |
2023年 | 52篇 |
2022年 | 48篇 |
2021年 | 63篇 |
2020年 | 138篇 |
2019年 | 116篇 |
2018年 | 133篇 |
2017年 | 176篇 |
2016年 | 145篇 |
2015年 | 122篇 |
2014年 | 279篇 |
2013年 | 462篇 |
2012年 | 228篇 |
2011年 | 433篇 |
2010年 | 305篇 |
2009年 | 357篇 |
2008年 | 412篇 |
2007年 | 371篇 |
2006年 | 357篇 |
2005年 | 323篇 |
2004年 | 266篇 |
2003年 | 286篇 |
2002年 | 252篇 |
2001年 | 197篇 |
2000年 | 187篇 |
1999年 | 188篇 |
1998年 | 196篇 |
1997年 | 161篇 |
1996年 | 111篇 |
1995年 | 92篇 |
1994年 | 90篇 |
1993年 | 61篇 |
1992年 | 49篇 |
1991年 | 34篇 |
1990年 | 39篇 |
1989年 | 21篇 |
1988年 | 24篇 |
1987年 | 25篇 |
1986年 | 22篇 |
1985年 | 17篇 |
1984年 | 28篇 |
1983年 | 11篇 |
1982年 | 25篇 |
1981年 | 21篇 |
1980年 | 14篇 |
1979年 | 7篇 |
1978年 | 12篇 |
1977年 | 7篇 |
1976年 | 6篇 |
1973年 | 6篇 |
排序方式: 共有7000条查询结果,搜索用时 15 毫秒
111.
Cheikh Birahim Ndiaye 《Journal of Functional Analysis》2007,251(1):1-58
Working in a given conformal class, we prove existence of constant Q-curvature metrics on compact manifolds of arbitrary dimension under generic assumptions. The problem is equivalent to solving a nth-order non-linear elliptic differential (or integral) equation with variational structure, where n is the dimension of the manifold. Since the corresponding Euler functional is in general unbounded from above and below, we use critical point theory, jointly with a compactness result for the above equation. 相似文献
112.
Seppo Hassi Manfred Mö ller Henk de Snoo 《Proceedings of the American Mathematical Society》2006,134(10):2885-2893
The class of Nevanlinna functions consists of functions which are holomorphic off the real axis, which are symmetric with respect to the real axis, and whose imaginary part is nonnegative in the upper halfplane. The Kac subclass of Nevanlinna functions is defined by an integrability condition on the imaginary part. In this note a further subclass of these Kac functions is introduced. It involves an integrability condition on the modulus of the Nevanlinna functions (instead of the imaginary part). The characteristic properties of this class are investigated. The definition of the new class is motivated by the fact that the Titchmarsh-Weyl coefficients of various classes of Sturm-Liouville problems (under mild conditions on the coefficients) actually belong to this class.
113.
We study Fourier multipliers which result from modulating jumps of Lévy processes. Using the theory of martingale transforms we prove that these operators are bounded in Lp(Rd) for 1<p<∞ and we obtain the same explicit bound for their norm as the one known for the second order Riesz transforms. 相似文献
114.
This paper newly designs the recursive least-squares (RLS) fixed-lag smoother and filter using the covariance information in linear continuous-time stochastic systems. It is assumed that the signal is observed with additive white observation noise and the signal is uncorrelated with the observation noise. The estimators require the covariance information of the signal and the variance of the observation noise. The auto-covariance function of the signal is expressed in the semi-degenerate kernel form. 相似文献
115.
A solution to the BBGKY hierarchy for nonequilibrium distribution functions is obtained within modified boundary conditions. The boundary conditions take into account explicitly both the nonequilibrium one-particle distribution function as well as local conservation laws. As a result, modified group expansions are proposed. On the basis of these expansions, a generalized kinetic equation for hard spheres and a generalized Bogolubov–Lenard–Balescu kinetic equation for a dense electron gas are derived within the polarization approximation. 相似文献
116.
宋敏 《新疆大学学报(理工版)》1993,(2)
本文考虑一类具有耗散与磁场效应的多维非线性Schrdinger型方程组的初边值问题。使用积分估计(包括L~p—L~q估计)证明了整体解的存在性。 相似文献
117.
118.
119.
E. L. Kristallovich A. G. Eshimbetov V. M. Promyslov N. D. Chuvylkin L. I. Belen'kii L. V. Molchanov Kh. M. Shakhidoyatov 《Chemistry of Heterocyclic Compounds》2003,39(11):1516-1520
Quantum-chemical calculations and IR spectroscopy were used to study the conformations as well as the energy and spectral characteristics of 2,3-trimethylene- and 2,3-pentamethylene-3,4-dihydro-4-quinazolinones. The shift of -electron density from the heterocyclic system to the carbonyl group and, thus, the proton affinity of the oxygen atom of this group increase with expansion of the bond angle at the nitrogen atom in going from a five-membered to seven-membered ring. 相似文献
120.
For an arbitrary poset P, subposets {P
i
: 1ik} form a transitive basis of P if P is the transitive closure of their union. Let u be the minimum size of a covering of P by chains within posets of the basis, s the maximum size of a family of elements with no pair comparable in any basis poset, and a the maximum size of an antichain in P. Define a dense covering to be a collection D of chains within basis posets such that each element belongs to a chain in D within each basis poset and is the top of at least k-1 chains and the bottom of at least k-1 chains in D. Dense coverings generalize ordinary chain coverings of poset. Let d=min {|D|–(k–1)|P|}. For an arbitrary poset and transitive basis, a convenient network model for dense coverings yields the following: Theorem 1: da, with equality iff P has a minimum chain decomposition in which every pair of consecutive elements on each chain are comparable in some basis poset. Theorem 2: usda. Theorem 3: s=d iff s=a. The most interesting special case is where the transitive basis expresses P as the product of two posets, in which case u and s measure the minimum and maximum sizes of unichain coverings and semiantichains. 相似文献