全文获取类型
收费全文 | 27465篇 |
免费 | 3852篇 |
国内免费 | 2022篇 |
专业分类
化学 | 5000篇 |
晶体学 | 100篇 |
力学 | 4998篇 |
综合类 | 488篇 |
数学 | 10556篇 |
物理学 | 12197篇 |
出版年
2024年 | 61篇 |
2023年 | 291篇 |
2022年 | 785篇 |
2021年 | 770篇 |
2020年 | 906篇 |
2019年 | 795篇 |
2018年 | 742篇 |
2017年 | 1022篇 |
2016年 | 1198篇 |
2015年 | 875篇 |
2014年 | 1476篇 |
2013年 | 2128篇 |
2012年 | 1521篇 |
2011年 | 1814篇 |
2010年 | 1557篇 |
2009年 | 1833篇 |
2008年 | 1692篇 |
2007年 | 1715篇 |
2006年 | 1438篇 |
2005年 | 1290篇 |
2004年 | 1193篇 |
2003年 | 1013篇 |
2002年 | 969篇 |
2001年 | 765篇 |
2000年 | 729篇 |
1999年 | 639篇 |
1998年 | 583篇 |
1997年 | 432篇 |
1996年 | 370篇 |
1995年 | 357篇 |
1994年 | 324篇 |
1993年 | 271篇 |
1992年 | 246篇 |
1991年 | 186篇 |
1990年 | 166篇 |
1989年 | 124篇 |
1988年 | 123篇 |
1987年 | 131篇 |
1986年 | 109篇 |
1985年 | 128篇 |
1984年 | 132篇 |
1983年 | 72篇 |
1982年 | 97篇 |
1981年 | 61篇 |
1980年 | 29篇 |
1979年 | 37篇 |
1978年 | 29篇 |
1977年 | 28篇 |
1976年 | 15篇 |
1973年 | 22篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
981.
本文应用谱分析理论研究了剪切湍流场中的压力脉动,包括功率谱、均方值等.通过对压力脉动Possion方程的Fourier变换,首先将压力脉动谱表示成速度脉动谱的形式.利用Navier-Stokes方程的形式解及准正态分布假设,可以进一步将压力脉动功率谱表达式中所包含的速度脉动的三阶相关与四阶相关表示成速度脉动的二阶相关(功率谱).最后,引入高雷诺数流的速度脉动功率谱模型,导出了由湍动e0,耗散ε,雷诺应力-iuj>及时均速度梯度表示的压力脉动均方值的湍流模式,并同现有数据进行了比较. 相似文献
982.
构建一类具有时滞效应的多商品非均衡蛛网模型.然后建立一个广义时滞差分不等式,在此基础上讨论该蛛网模型的平衡点存在性,并着重对其稳定性进行分析. 相似文献
983.
Combining grey relation and TOPSIS concepts for selecting an expatriate host country 总被引:7,自引:0,他引:7
As international corporate activities increase, their staffing involves more strategic concerns. However, foreign assignments have many differences, and dissatisfaction with the host country is a known cause of expatriate failure. From the point of view of an expatriate candidate, the decision of whether to take an expatriate assignment can be regarded as a FMCDM (fuzzy multiple criteria decision making) problem. This paper describes a fuzzy AHP (fuzzy analytic hierarchy process) to determine the weighting of subjective judgments. Using the Sugeno integral for λ-fuzzy measure, and using the nonadditive fuzzy integral technique to evaluate the synthetic utility values of the alternatives and the fuzzy weights, then the best host country alternative can be derived with the grey relation model. The authors further combine the grey relation model based on the concepts of TOPSIS (technique for order preference by similarity to ideal solution) to evaluate and select the best alternative. A real case of expatriate assignment decision-making was used to demonstrate that the grey relation model combined with the ideas of TOPSIS results in a satisfactory and effective evaluation. 相似文献
984.
We briefly describe the theory of root transfer matrices for four-line models with the field in the new indexless form. We
use theoretical and numerical methods to reveal new effects in the theory of singular points and phase transitions. A substantial
part of the results is obtained using a numerical algorithm that drastically (at least exponentially) reduces the computational
complexity of Ising-type models by using the extremely sparse root transfer matrix.
__________
Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 149, No. 2, pp. 281–298, November, 2006. 相似文献
985.
986.
987.
J. K. Ghorai 《Annals of the Institute of Statistical Mathematics》1991,43(4):747-760
The problem of estimating a smooth quantile function, Q(·), at a fixed point p, 0 < p < 1, is treated under a nonparametric smoothness condition on Q. The asymptotic relative deficiency of the sample quantile based on the maximum likelihood estimate of the survival function under the proportional hazards model with respect to kernel type estimators of the quantile is evaluated. The comparison is based on the mean square errors of the estimators. It is shown that the relative deficiency tends to infinity as the sample size, n, tends to infinity. 相似文献
988.
989.
990.
Using the Lowry-Garin model as an example, we illustrate the complexity of bifurcation and aggregation issues in urban/regional spatial systems. As a first step, a disaggregate version of the Lowry-Garin model is formulated. Then the general conditions for bifurcation are identified in terms of disaggregate labor-force participation rate, population-serving ratio and accessibility indices. Physical interpretation of these conditions is also given. 相似文献