全文获取类型
收费全文 | 13396篇 |
免费 | 269篇 |
国内免费 | 74篇 |
专业分类
化学 | 8342篇 |
晶体学 | 133篇 |
力学 | 453篇 |
数学 | 1956篇 |
物理学 | 2855篇 |
出版年
2022年 | 131篇 |
2021年 | 145篇 |
2020年 | 181篇 |
2019年 | 174篇 |
2018年 | 135篇 |
2017年 | 116篇 |
2016年 | 277篇 |
2015年 | 245篇 |
2014年 | 310篇 |
2013年 | 682篇 |
2012年 | 635篇 |
2011年 | 708篇 |
2010年 | 361篇 |
2009年 | 419篇 |
2008年 | 652篇 |
2007年 | 657篇 |
2006年 | 620篇 |
2005年 | 562篇 |
2004年 | 530篇 |
2003年 | 436篇 |
2002年 | 385篇 |
2001年 | 240篇 |
2000年 | 246篇 |
1999年 | 141篇 |
1998年 | 137篇 |
1997年 | 139篇 |
1996年 | 187篇 |
1995年 | 138篇 |
1994年 | 195篇 |
1993年 | 195篇 |
1992年 | 197篇 |
1991年 | 141篇 |
1990年 | 142篇 |
1989年 | 150篇 |
1988年 | 120篇 |
1987年 | 139篇 |
1986年 | 126篇 |
1985年 | 223篇 |
1984年 | 183篇 |
1983年 | 128篇 |
1982年 | 157篇 |
1981年 | 136篇 |
1980年 | 157篇 |
1979年 | 144篇 |
1978年 | 150篇 |
1977年 | 128篇 |
1976年 | 144篇 |
1975年 | 117篇 |
1974年 | 143篇 |
1973年 | 132篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
Monica L. Smith 《Complexity》2007,12(4):28-35
When depicted on maps as homogenous territorial wholes, ancient states are visually summarized as static entities in a way that conceals the highly fluid dynamics of polity formation, maintenance, and growth. Models derived from studies of animal behavior show that “territory” does not consist of an undifferentiated use of the landscape. Instead, the concept of territory can be parsed into a series of resource‐rich nodes linked by corridors of access, surrounded by unutilized regions and boundaries marked at points of competition. Ancient human groups also can be analyzed as having perceived and occupied landscapes through strategies of flexible networks in which nodes and corridors were surrounded by unutilized spaces around which boundaries were selectively identified and defended. This strategy is identifiable in human social groups at different levels of complexity ranging from hunter‐gatherers through ancient chiefdoms and states. © 2007 Wiley Periodicals, Inc. Complexity 12: 28–35, 2007 相似文献
993.
Wael Abu-Shammala Alberto Torchinsky 《Proceedings of the American Mathematical Society》2007,135(9):2839-2843
In this paper we present an atomic decomposition of integrable functions. As an application we compute the distance of in to the Hardy space .
994.
We examine the problem of building or fortifying a network to defend against enemy attacks in various scenarios. In particular,
we examine the case in which an enemy can destroy any portion of any arc that a designer constructs on the network, subject
to some interdiction budget. This problem takes the form of a three-level, two-player game, in which the designer acts first
to construct a network and transmit an initial set of flows through the network. The enemy acts next to destroy a set of constructed
arcs in the designer’s network, and the designer acts last to transmit a final set of flows in the network. Most studies of
this nature assume that the enemy will act optimally; however, in real-world scenarios one cannot necessarily assume rationality
on the part of the enemy. Hence, we prescribe optimal network design algorithms for three different profiles of enemy action:
an enemy destroying arcs based on capacities, based on initial flows, or acting optimally to minimize our maximum profits
obtained from transmitting flows. 相似文献
995.
We present a new linearized model for the zero-one quadratic programming problem, whose size is linear in terms of the number of variables in the original nonlinear problem. Our derivation yields three alternative reformulations, each varying in model size and tightness. We show that our models are at least as tight as the one recently proposed in [7], and examine the theoretical relationship of our models to a standard linearization of the zero-one quadratic programming problem. Finally, we demonstrate the efficacy of solving each of these models on a set of randomly generated test instances. 相似文献
996.
Abstract Let p be a prime integer and M a Krull monoid with divisor class group
. We represent by S the set of nontrivial divisor classes of
which contain prime divisors. We present a new inequality for the elasticity of M (denoted ρ (M)) which is dependent on the cardinality of S and argue that this inequality is the best possible. If M as above has | S| = 3, then it is known that
, but for large p, not all the values in this containment set can be realized. For each | S| = 3, we produce a submonoid
of
such that
Keywords: Krull monoid, Block monoid, Elasticity of factorization
Mathematics Subject Classification (2000): 20M14, 20D60, 13F05 相似文献
997.
In this paper we deal with nonlinear second-order boundary value problems with impulses. The impulsive functions depend implicitly on the different considered variables and the boundary value conditions are nonlinear. In both cases functional dependence on the solution is allowed. The existence results follow from the existence of a pair of well-ordered lower and upper solutions. 相似文献
998.
Alberto Damiano 《Advances in Applied Clifford Algebras》2007,17(3):343-355
This paper is a short report on the generalization of some results of our previous paper [12] to the case of spin j/2 Dirac operators in real dimension three for arbitrary odd integer j. We use an explicit formula for the local expression of such operators to study their algebraic properties, construct the
compatibility conditions of the overdetermined system associated to the operator in several spatial variables, and we prove
that its associated algebraic complex, dual do the BGG sequence coming from representation theory, has substantially the same
pattern as the Cauchy-Fueter complex.
The author is a member of the Eduard Čech Center and his research is supported by the relative grants. 相似文献
999.
Narciso Martí-Oliet Miguel Palomino Alberto Verdejo 《Journal of Algorithms in Cognition, Informatics and Logic》2007,62(3-4):95-116
By means of several examples of structural operational semantics for a variety of languages, we justify the importance and interest of using the notions of strategies and simulations in the semantic framework provided by rewriting logic and implemented in the Maude metalanguage. On the one hand, we describe a basic strategy language for Maude and show its application to CCS, the ambient calculus, and the parallel functional language Eden. On the other hand, we show how the concept of stuttering simulation can be used inside Maude to show that a stack machine correctly implements the operational semantics of a simple functional language. 相似文献
1000.
We prove some extension theorems for analytic objects, in particular sections of a coherent sheaf, defined in semi q-coronae of a complex space. Semi q-coronae are domains whose boundary is the union of a Levi flat part, a q-pseudoconvex part and a q-pseudoconcave part. Such results are obtained mainly using cohomological techniques. 相似文献