全文获取类型
收费全文 | 79972篇 |
免费 | 374篇 |
国内免费 | 384篇 |
专业分类
化学 | 25431篇 |
晶体学 | 820篇 |
力学 | 6741篇 |
数学 | 32328篇 |
物理学 | 15410篇 |
出版年
2018年 | 10441篇 |
2017年 | 10272篇 |
2016年 | 6083篇 |
2015年 | 861篇 |
2014年 | 312篇 |
2013年 | 407篇 |
2012年 | 3823篇 |
2011年 | 10555篇 |
2010年 | 5651篇 |
2009年 | 6078篇 |
2008年 | 6673篇 |
2007年 | 8814篇 |
2006年 | 282篇 |
2005年 | 1407篇 |
2004年 | 1591篇 |
2003年 | 2039篇 |
2002年 | 1084篇 |
2001年 | 286篇 |
2000年 | 324篇 |
1999年 | 177篇 |
1998年 | 229篇 |
1997年 | 173篇 |
1996年 | 248篇 |
1995年 | 159篇 |
1994年 | 126篇 |
1993年 | 135篇 |
1992年 | 88篇 |
1991年 | 91篇 |
1990年 | 83篇 |
1989年 | 88篇 |
1988年 | 93篇 |
1987年 | 87篇 |
1986年 | 81篇 |
1985年 | 73篇 |
1984年 | 77篇 |
1983年 | 56篇 |
1982年 | 64篇 |
1981年 | 79篇 |
1980年 | 82篇 |
1979年 | 75篇 |
1978年 | 57篇 |
1977年 | 45篇 |
1976年 | 38篇 |
1975年 | 40篇 |
1973年 | 51篇 |
1914年 | 48篇 |
1913年 | 40篇 |
1912年 | 47篇 |
1909年 | 47篇 |
1908年 | 40篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
241.
The periodic precipitation pattern formation in gelatinous media is interpreted as a moving boundary problem. The time law,
spacing law and width law are revisited on the basis of the new scenario. The explicit dependence of the geometric structure
on the initial concentrations of the reactants is derived. Matalon—Packter law, which relates the spacing coefficient with
the initial concentrations is reformulated removing many ambiguities and impractical parameters. Experimental results are
discussed to establish the significance of moving boundary concept in the diffusion controlled pattern forming systems 相似文献
242.
The rate-dependent effects in metallic ferromagnetic materials with magnetization processes attributed to domain-walls motion were studied. The experimental method for eddy-current relaxation time determination was proposed. Some discrepancies between the data and theoretical predictions were observed and discussed. The origin of these discrepancies is accounted for by the decrease of viscous-type relaxation process as the rate of change of averaged magnetization is approaching zero. 相似文献
243.
244.
The Nambu-bracket quantization of the hydrogen atom is worked out as an illustration of the general method. The dynamics of topological open branes is controlled classically by Nambu brackets. Such branes then may be quantized through the consistent quantization of the underlying Nambu brackets: properly defined, the quantum Nambu-brackets comprise an associative structure, although the naive derivation property is mooted through operator entwinement. For superintegrable systems, such as the hydrogen atom, the results coincide with those furnished by Hamiltonian quantization - but the method is not limited to Hamiltonian systems. 相似文献
245.
Arnold Neumaier 《Journal of Global Optimization》2003,25(2):175-181
A family of multivariate rational functions is constructed. It has strong local minimizers with prescribed function values at prescribed positions. While there might be additional local minima, such minima cannot be global. A second family of multivariate rational functions is given, having prescribed global minimizers and prescribed interpolating data. 相似文献
246.
林诒勋 《高校应用数学学报(英文版)》2003,18(3):361-369
§ 1 IntroductionThe cutwidth problem for graphs,as well as a class of optimal labeling and embed-ding problems,have significant applications in VLSI designs,network communicationsand other areas (see [2 ] ) .We shall follow the graph-theoretic terminology and notation of [1 ] .Let G=(V,E)be a simple graph with vertex set V,| V| =n,and edge set E.A labeling of G is a bijec-tion f:V→ { 1 ,2 ,...,n} ,which can by regarded as an embedding of G into a path Pn.Fora given labeling f of G,th… 相似文献
247.
In this paper a tripartite qualitative design combining abservation, stimulated recall and interview is presented and discussed. This three-step-design makes it possible to get insight into the interaction of internal and external processes when solving mathematical tasks. The data analysis depends on the research question and the methodological approach. In the light of two research projects in mathematics education two different methods of data analysis are presented and methodologically reflected. 相似文献
248.
We draw upon the concepts of knowledge market, organizational tacit knowledge, credit assignment, and single-loop learning in proposing a market-based conceptual model for collaborative organizational learning. Our proposed model is characterized by the local competition among seller agents and the global collaboration among winner agents in forming a plan, through a chain of ‘upstream–downstream’ working relationship, for task accomplishment. This feature is achieved through three closely coupled processes: the expert selection process, the capital reallocation process, and the plan formation process. Our model is intended for multiple-step learning environment in which each task consists of a sequence of single-step learning tasks. Learning at the global level is the result of a sequence of nested single-loop learning at the local level. 相似文献
249.
In this paper, we investigate the exact distribution of the waiting time for ther-th ℓ-overlapping occurrence of success-runs of a specified length in a sequence of two state Markov dependent trials. The
probability generating functions are derived explicitly, and as asymptotic results, relationships of a negative binomial distribution
of orderk and an extended Poisson distribution of orderk are discussed. We provide further insights into the run-related problems from the viewpoint of the ℓ-overlapping enumeration
scheme. We also study the exact distribution of the number of ℓ-overlapping occurrences of success-runs in a fixed number
of trials and derive the probability generating functions. The present work extends several properties of distributions of
orderk and leads us a new type of geneses of the discrete distributions. 相似文献
250.