首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   638篇
  免费   116篇
  国内免费   24篇
化学   124篇
晶体学   5篇
力学   85篇
综合类   4篇
数学   197篇
物理学   363篇
  2024年   1篇
  2023年   14篇
  2022年   11篇
  2021年   12篇
  2020年   11篇
  2019年   16篇
  2018年   11篇
  2017年   16篇
  2016年   20篇
  2015年   18篇
  2014年   37篇
  2013年   59篇
  2012年   46篇
  2011年   55篇
  2010年   44篇
  2009年   67篇
  2008年   48篇
  2007年   66篇
  2006年   32篇
  2005年   24篇
  2004年   18篇
  2003年   16篇
  2002年   16篇
  2001年   9篇
  2000年   11篇
  1999年   6篇
  1998年   11篇
  1997年   7篇
  1996年   8篇
  1995年   7篇
  1994年   9篇
  1993年   6篇
  1992年   8篇
  1991年   5篇
  1990年   7篇
  1989年   4篇
  1988年   10篇
  1987年   3篇
  1986年   5篇
  1980年   1篇
  1977年   1篇
  1972年   1篇
  1970年   1篇
排序方式: 共有778条查询结果,搜索用时 15 毫秒
61.
枸椽酸锗能明显提高小鼠血清溶血素抗体水平,增强二硝基氯苯(DNCB)致小鼠迟发型皮肤过敏反应。增加小鼠免疫器官胸腺和脾脏的重量,表明枸椽酸锗能增强小鼠体液免疫和细胞免疫水平。  相似文献   
62.
This paper proposes a new mathematical model to solve the cell formation, operator assignment and inter-cell layout problems, simultaneously. The objectives of proposed model are minimization of inter–intra cell part trips, machine relocation cost and operator related issues. Since the objective function of the proposed model consists of none commensurable statements, the preferred solution is obtained by the LP-metric approach. In order to validate the proposed model, some numerical examples are generated randomly and solved by branch and bound technique. Moreover; a real case study is illustrated in order to verify its applicability in an automobile producer company. Moreover the sensitivity analysis of proposed model shows that considering the operator assignment problem has significant impact on the overall system efficiency.  相似文献   
63.
Cellular automaton theory has previously been used to study cell growth. In this study, we present a three-dimensional cellular automaton model performing the growth simulation of normal and cancerous cells. The necessary nutrient supply is provided by an artificial arterial tree which is generated by constrained constructive optimization. Spatial oxygen diffusion is approximated again by a cellular automaton model. All results could be illustrated dynamically by three-dimensional volume visualization. Because of the chosen modelling approach, an extension of the model to simulate angiogenic processes is possible.  相似文献   
64.
《随机分析与应用》2013,31(6):1283-1303
Abstract

The evolution of a biological system, like a cellular one, is analyzed by constructing a Markov process on a suitable state space. This is performed by the introduction of an infinitesimal generator for the Markov semigroup associated to this process. A measure valued process is then defined in a natural way and it is proved that his first moment satisfies the Sharpe–Lotka system in a distributional sense. Hence the study of the moments of the process is tried. An involved integral equation for the moment generating functional is derived.  相似文献   
65.
ABSTRACT

In this work, we consider the problem of modelling the phenomenon of forest fires using the cellular automata approach. The proposed model takes into account the main parameters that affect this phenomenon like nature and density of vegetation, humidity, wind, and altitude. We developed a decision-aided tool with JAVA which allows to analyse and format several hybrid collected data (satellite images, Digital Terrain Model) relatively to each studied area. The generated scenarios of forest fire spread in the study area will be considered as a guide for strategies in control and prevention of forest fires. As an application, we consider the watershed Oued Laou (Morocco).  相似文献   
66.
67.
68.
A graph G has the Median Cycle Property (MCP) if every triple (u0,u1,u2) of vertices of G admits a unique median or a unique median cycle, that is a gated cycle C of G such that for all i,j,k∈{0,1,2}, if xi is the gate of ui in C, then: {xi,xj}⊆IG(ui,uj) if ij, and dG(xi,xj)<dG(xi,xk)+dG(xk,xj). We prove that a netlike partial cube has the MCP if and only if it contains no triple of convex cycles pairwise having an edge in common and intersecting in a single vertex. Moreover a finite netlike partial cube G has the MCP if and only if G can be obtained from a set of even cycles and hypercubes by successive gated amalgamations, and equivalently, if and only if G can be obtained from K1 by a sequence of special expansions. We also show that the geodesic interval space of a netlike partial cube having the MCP is a Pash-Peano space (i.e. a closed join space).  相似文献   
69.
Consider the collection of left permutive cellular automata Φ with no memory, defined on the space S of all doubly infinite sequences from a finite alphabet. There exists , a dense subset of S, such that is topologically conjugate to an odometer for all so long as Φm is not the identity map for any m. Moreover, Φ generates the same odometer for all . The set is a dense Gδ subset with full measure of a particular subspace of S.  相似文献   
70.
This work shows that a class of pseudorandom binary sequences, the so-called interleaved sequences, can be generated by means of linear multiplicative polynomial cellular automata. In fact, these linear automata generate all the solutions of a type of linear difference equations with binary coefficients. Interleaved sequences are just particular solutions of such equations. In this way, popular nonlinear sequence generators with cryptographic application can be linearized in terms of simple cellular automata.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号