全文获取类型
收费全文 | 15029篇 |
免费 | 395篇 |
国内免费 | 239篇 |
专业分类
化学 | 928篇 |
晶体学 | 23篇 |
力学 | 199篇 |
综合类 | 25篇 |
数学 | 13439篇 |
物理学 | 1049篇 |
出版年
2023年 | 28篇 |
2022年 | 32篇 |
2021年 | 46篇 |
2020年 | 63篇 |
2019年 | 404篇 |
2018年 | 483篇 |
2017年 | 251篇 |
2016年 | 165篇 |
2015年 | 193篇 |
2014年 | 486篇 |
2013年 | 918篇 |
2012年 | 541篇 |
2011年 | 905篇 |
2010年 | 818篇 |
2009年 | 1151篇 |
2008年 | 1207篇 |
2007年 | 1179篇 |
2006年 | 927篇 |
2005年 | 564篇 |
2004年 | 497篇 |
2003年 | 466篇 |
2002年 | 359篇 |
2001年 | 316篇 |
2000年 | 307篇 |
1999年 | 374篇 |
1998年 | 321篇 |
1997年 | 245篇 |
1996年 | 318篇 |
1995年 | 328篇 |
1994年 | 329篇 |
1993年 | 223篇 |
1992年 | 162篇 |
1991年 | 103篇 |
1990年 | 87篇 |
1989年 | 102篇 |
1988年 | 62篇 |
1987年 | 55篇 |
1986年 | 53篇 |
1985年 | 86篇 |
1984年 | 88篇 |
1983年 | 45篇 |
1982年 | 91篇 |
1981年 | 80篇 |
1980年 | 50篇 |
1979年 | 26篇 |
1978年 | 34篇 |
1977年 | 27篇 |
1976年 | 29篇 |
1974年 | 14篇 |
1973年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
981.
Let E→M be a holomorphic vector bundle over a compact Kähler manifold (M,ω). We prove that if E admits a ω-balanced metric (in X. Wang’s terminology (Wang, 2005 [3])) then it is unique. This result together with Biliotti and Ghigi (2008) [14] implies the existence and uniqueness of ω-balanced metrics of certain direct sums of irreducible homogeneous vector bundles over rational homogeneous varieties. We finally apply our result to show the rigidity of ω-balanced Kähler maps into Grassmannians. 相似文献
982.
By the application of the coinduction method as well as the Magri method to the ideal of real Hilbert–Schmidt operators we construct the hierarchies of integrable Hamiltonian systems on Banach Lie–Poisson spaces which consist of such types of operators. We also discuss their algebraic and analytic properties and solve them in dimensions, N=2,3,4. 相似文献
983.
984.
Constructive theories usually have interesting metamathematical properties where explicit witnesses can be extracted from proofs of existential sentences. For relational theories, probably the most natural of these is the existence property, EP, sometimes referred to as the set existence property . This states that whenever (∃x)?(x) is provable, there is a formula χ(x) such that (∃!x)?(x)∧χ(x) is provable. It has been known since the 80s that EP holds for some intuitionistic set theories and yet fails for IZF. Despite this, it has remained open until now whether EP holds for the most well known constructive set theory, CZF. In this paper we show that EP fails for CZF. 相似文献
985.
986.
In this paper we study the reverse mathematics of two theorems by Bonnet about partial orders. These results concern the structure and cardinality of the collection of initial intervals. The first theorem states that a partial order has no infinite antichains if and only if its initial intervals are finite unions of ideals. The second one asserts that a countable partial order is scattered and does not contain infinite antichains if and only if it has countably many initial intervals. We show that the left to right directions of these theorems are equivalent to ACA0 and ATR0, respectively. On the other hand, the opposite directions are both provable in WKL0, but not in RCA0. We also prove the equivalence with ACA0 of the following result of Erdös and Tarski: a partial order with no infinite strong antichains has no arbitrarily large finite strong antichains. 相似文献
987.
For α∈R, let pR(t,x,x) denote the diagonal of the transition density of the α-Bessel process in (0,1], killed at 0 and reflected at 1. As a function of x, if either α≥3 or α=1, then for t>0, the diagonal is nondecreasing. This monotonicity property fails if 1≠α<3. 相似文献
988.
We develop a technique for the construction of random fields on algebraic structures. We deal with two general situations: random fields on homogeneous spaces of a compact group and in the spin line bundles of the 2-sphere. In particular, every complex Gaussian isotropic spin random field can be represented in this way. Our construction extends P. Lévy’s original idea for the spherical Brownian motion. 相似文献
989.
This paper extends the works of Kang and Ramanan (2010) and Kaspi and Ramanan (2011), removing the hypothesis of absolute continuity of the service requirement and patience time distributions. We consider a many-server queueing system in which customers enter service in the order of arrival in a non-idling manner and where reneging is considerate. Similarly to Kang and Ramanan (2010), the dynamics of the system are represented in terms of a process that describes the total number of customers in the system as well as two measure-valued processes that record the age in service of each of the customers being served and the “potential” waiting times. When the number of servers goes to infinity, fluid limit is established for this triple of processes. The convergence is in the sense of probability and the limit is characterized by an integral equation. 相似文献
990.
We study the asymptotic behaviour of Markov chains (Xn,ηn) on Z+×S, where Z+ is the non-negative integers and S is a finite set. Neither coordinate is assumed to be Markov. We assume a moments bound on the jumps of Xn, and that, roughly speaking, ηn is close to being Markov when Xn is large. This departure from much of the literature, which assumes that ηn is itself a Markov chain, enables us to probe precisely the recurrence phase transitions by assuming asymptotically zero drift for Xn given ηn. We give a recurrence classification in terms of increment moment parameters for Xn and the stationary distribution for the large- X limit of ηn. In the null case we also provide a weak convergence result, which demonstrates a form of asymptotic independence between Xn (rescaled) and ηn. Our results can be seen as generalizations of Lamperti’s results for non-homogeneous random walks on Z+ (the case where S is a singleton). Motivation arises from modulated queues or processes with hidden variables where ηn tracks an internal state of the system. 相似文献