全文获取类型
收费全文 | 15975篇 |
免费 | 1383篇 |
国内免费 | 1328篇 |
专业分类
化学 | 4965篇 |
晶体学 | 123篇 |
力学 | 1207篇 |
综合类 | 256篇 |
数学 | 8146篇 |
物理学 | 3989篇 |
出版年
2024年 | 26篇 |
2023年 | 132篇 |
2022年 | 312篇 |
2021年 | 330篇 |
2020年 | 446篇 |
2019年 | 410篇 |
2018年 | 404篇 |
2017年 | 436篇 |
2016年 | 513篇 |
2015年 | 419篇 |
2014年 | 698篇 |
2013年 | 1118篇 |
2012年 | 644篇 |
2011年 | 761篇 |
2010年 | 709篇 |
2009年 | 869篇 |
2008年 | 1006篇 |
2007年 | 1083篇 |
2006年 | 890篇 |
2005年 | 782篇 |
2004年 | 673篇 |
2003年 | 701篇 |
2002年 | 704篇 |
2001年 | 556篇 |
2000年 | 481篇 |
1999年 | 437篇 |
1998年 | 442篇 |
1997年 | 332篇 |
1996年 | 349篇 |
1995年 | 282篇 |
1994年 | 238篇 |
1993年 | 201篇 |
1992年 | 165篇 |
1991年 | 140篇 |
1990年 | 104篇 |
1989年 | 88篇 |
1988年 | 94篇 |
1987年 | 76篇 |
1986年 | 72篇 |
1985年 | 90篇 |
1984年 | 68篇 |
1983年 | 40篇 |
1982年 | 74篇 |
1981年 | 64篇 |
1980年 | 36篇 |
1979年 | 50篇 |
1978年 | 37篇 |
1977年 | 31篇 |
1976年 | 31篇 |
1973年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
121.
We consider an extension of the Feynman path integral to the quantum mechanics of noncommuting spatial coordinates and formulate the corresponding formalism for noncommutative classical dynamics related to quadratic Lagrangians (Hamiltonians). The basis of our approach is that a quantum mechanical system with a noncommutative configuration space can be regarded as another effective system with commuting spatial coordinates. Because the path integral for quadratic Lagrangians is exactly solvable and a general formula for the probability amplitude exists, we restrict our research to this class of Lagrangians. We find a general relation between quadratic Lagrangians in their commutative and noncommutative regimes and present the corresponding noncommutative path integral. This method is illustrated with two quantum mechanical systems in the noncommutative plane: a particle in a constant field and a harmonic oscillator. 相似文献
122.
This paper investigates regression quantiles (RQ) for unstable autoregressive models. The uniform Bahadur representation of the RQ process is obtained. The joint asymptotic distribution of the RQ process is derived in a unified manner for all types of characteristic roots on or outside the unit circle. It involves stochastic integrals in terms of a sequence of independent and identically distributed multivariate Brownian motions with correlated components. The related L-estimator is also discussed. The asymptotic distributions of the RQ and the L-estimator corresponding to the nonstationary componentwise arguments can be transformed into a function of a normal random variable and a sequence of i.i.d. univariate Brownian motions. This is different from the analysis based on the LSE in the literature. As an auxiliary theorem, a weak convergence of a randomly weighted residual empirical process to the stochastic integral of a Kiefer process is established. The results obtained in this paper provide an asymptotic theory for nonstationary time series processes, which can be used to construct robust unit root tests. 相似文献
123.
Three protocols for shotgun process are put forth in which simultaneous multi-fold reactions occur exclusively to each other. The first one involves simple combination of selective and non-selective reactions. Even if the simple protocol fails to give rise to the high selectivity, satisfactory outcome can be achieved by kinetic control or adjustment of functional groups. 相似文献
124.
研究了Banach空间中拟-似变分包含解的存在与逼近问题.给出了一种寻求解的新的迭代算法,建立了具混合误差的Ishikawa型迭代序列强收敛到解的充要条件.所得结果推广了一些相关的结果. 相似文献
125.
Frank N. Proske Madan L. Puri 《Proceedings of the American Mathematical Society》2003,131(9):2937-2944
In this article we prove a strong law of large numbers for Borel measurable nonseparably valued random elements in the case of generalized random sets.
126.
A Kind of direct methods is presented for the solution of optimal control problems with state constraints.These methods are sequential quadratic programming methods.At every iteration a quadratic programming which is obtained by quadratic approximation to Lagrangian function and Linear approximations to constraints is solved to get a search direction for a merit function.The merit function is formulated by augmenting the Lagrangian funetion with a penalty term.A line search is carried out along the search direction to determine a step length such that the merit function is decreased.The methods presented in this paper include continuous sequential quadratic programming methods and discreate sequential quadrade programming methods. 相似文献
127.
We first note that Gentzen's proof-reduction for his consistency proof of PA can be directly interpreted as moves of Kirby-Paris' Hydra Game, which implies a direct independence proof of the game (Section 1 and Appendix). Buchholz's Hydra Game for labeled hydras is known to be much stronger than PA. However, we show that the one-dimensional version of Buchholz's Game can be exactly identified to Kirby-Paris' Game (which is two-dimensional but without labels), by a simple and natural interpretation (Section 2). Jervell proposed another type of a combinatorial game, by abstracting Gentzen's proof-reductions and showed that his game is independent of PA. We show (Section 3) that this Jervell's game is actually much stronger than PA, by showing that the critical ordinal of Jervell's game is φω (0) (while that of PA or of Kirby-Paris' Game is φ1 (0) = ?0) in the Veblen hierarchy of ordinals. 相似文献
128.
Zhi Shui HU Chun SU 《数学学报(英文版)》2007,23(7):265-1270
Let {X(t), t ≥ 0} be a Lévy process with EX(1) = 0 and EX^2(1) 〈 ∞. In this paper, we shall give two precise asymptotic theorems for {X(t), t 〉 0}. By the way, we prove the corresponding conclusions for strictly stable processes and a general precise asymptotic proposition for sums of i.i.d. random variables. 相似文献
129.
We consider a composite material composed of fibres included in a resin which becomes solid when it is heated up (reaction of reticulation). The mathematical modelling of the cure process is given by a kinetic equation describing the evolution of the reaction of reticulation coupled with the heat equation. In this paper, we are interested in the computation of approximate solutions. We propose a family of discretized problems depending on two parameters (β1, β2) ε [0, 1]2 which split the linear and non‐ linear terms in implicit and explicit parts. We prove the stability and convergence of the discretization for any (β1, β2) ε [½, 1 ] × [0, 1]. We present also some numerical results. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
130.
Wensheng Wang 《Annales de l'Institut Henri Poincaré (B) Probabilités et Statistiques》2007,43(5):619-631
The almost sure sample function behavior of the vector-valued fractional Brownian sheet is investigated. In particular, the global and the local moduli of continuity of the sample functions are studied. These results give precise information about the continuity and the oscillation behavior of the sample functions. 相似文献