全文获取类型
收费全文 | 31122篇 |
免费 | 3168篇 |
国内免费 | 2320篇 |
专业分类
电工技术 | 2203篇 |
技术理论 | 1篇 |
综合类 | 5539篇 |
化学工业 | 2497篇 |
金属工艺 | 927篇 |
机械仪表 | 1807篇 |
建筑科学 | 1924篇 |
矿业工程 | 614篇 |
能源动力 | 886篇 |
轻工业 | 1256篇 |
水利工程 | 936篇 |
石油天然气 | 1856篇 |
武器工业 | 376篇 |
无线电 | 3041篇 |
一般工业技术 | 3791篇 |
冶金工业 | 760篇 |
原子能技术 | 480篇 |
自动化技术 | 7716篇 |
出版年
2024年 | 91篇 |
2023年 | 338篇 |
2022年 | 594篇 |
2021年 | 670篇 |
2020年 | 846篇 |
2019年 | 876篇 |
2018年 | 849篇 |
2017年 | 972篇 |
2016年 | 1010篇 |
2015年 | 1042篇 |
2014年 | 1625篇 |
2013年 | 2070篇 |
2012年 | 2252篇 |
2011年 | 2248篇 |
2010年 | 1775篇 |
2009年 | 1859篇 |
2008年 | 1780篇 |
2007年 | 1997篇 |
2006年 | 1846篇 |
2005年 | 1603篇 |
2004年 | 1385篇 |
2003年 | 1210篇 |
2002年 | 1042篇 |
2001年 | 844篇 |
2000年 | 817篇 |
1999年 | 759篇 |
1998年 | 636篇 |
1997年 | 573篇 |
1996年 | 491篇 |
1995年 | 485篇 |
1994年 | 390篇 |
1993年 | 335篇 |
1992年 | 276篇 |
1991年 | 239篇 |
1990年 | 197篇 |
1989年 | 158篇 |
1988年 | 113篇 |
1987年 | 73篇 |
1986年 | 54篇 |
1985年 | 41篇 |
1984年 | 32篇 |
1983年 | 17篇 |
1982年 | 22篇 |
1981年 | 24篇 |
1980年 | 10篇 |
1979年 | 11篇 |
1978年 | 4篇 |
1977年 | 5篇 |
1959年 | 4篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
将任意差分精细积分法用于三维波动方程地震正演,关键在于如何消除数值计算中有限波场区域边界引起的边界反射。文中采用Berenger给出的电磁波完全匹配层吸收边界条件,推导出三维波动方程任意差分精细积分法地震正演的完全匹配层吸收边界条件计算公式,并给出了完全匹配层吸收边界条件算例。计算结果表明,此方法压制边界反射效果明显。三维波动方程地震正演模拟实例表明,完全匹配层吸收边界条件的任意差分精细积分法为复杂区地震波传播规律研究提供了一种实用的正演模拟工具 相似文献
93.
I. N. Ishchuk 《Measurement Techniques》2007,50(10):1081-1086
A three-dimensional solution of the direct problem of heat conduction when a linear pulsed heat source acts in the plane of
contact of two semibounded bodies is presented. The solution is obtained by the method of finite differences. An example of
the modeling is considered.
__________
Translated from Izmeritel’naya Tekhnika, No. 10, pp. 42–45, October, 2007. 相似文献
94.
Sánchez-Meca Julio; Marín-Martínez Fulgencio; Chacón-Moscoso Salvador 《Canadian Metallurgical Quarterly》2003,8(4):448
It is very common to find meta-analyses in which some of the studies compare 2 groups on continuous dependent variables and others compare groups on dichotomized variables. Integrating all of them in a meta-analysis requires an effect-size index in the same metric that can be applied to both types of outcomes. In this article, the performance in terms of bias and sampling variance of 7 different effect-size indices for estimating the population standardized mean difference from a 2 × 2 table is examined by Monte Carlo simulation, assuming normal and nonnormal distributions. The results show good performance for 2 indices, one based on the probit transformation and the other based on the logistic distribution. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
95.
F-X域粘弹性波动方程保幅偏移 总被引:6,自引:1,他引:5
提出了一种利用粘弹性声波波动方程进行偏移的新方法。其基本思路是,修改成像条件,使修改后的成像方程中考虑振幅补偿,然后利用粘弹性、单程波动方程在F-X域对震源和接收点波场进行延拓,进而完成散射、透射等补偿。理论数据处理和实际地震资料处理表明,该方法理论基础可靠,处理效果明显,能较好地解决实际地质问题。 相似文献
96.
Tokar David M.; Withrow Jason R.; Hall Rosalie J.; Moradi Bonnie 《Canadian Metallurgical Quarterly》2003,50(1):3
Structural equation modeling was used to test theoretically based models in which psychological separation and attachment security variables were related to career indecision and those relations were mediated through vocational self-concept crystallization. In contrast to previous studies, which have found either weak or no support for a relation between separation or attachment security variables and career indecision, results based on a sample of 350 college students indicated that some components of separation and attachment security did relate to career indecision in a theoretically supportable direction. Results also revealed that regardless of whether global or component career indecision measures were used, separation and attachment security effects on indecision were at least partially mediated through vocational self-concept crystallization. The strongest mediated relations were observed for the effects of attachment anxiety and maternal separation. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
97.
A detection-theoretic analysis of the auditory localization of dual-impulse stimuli is described, and a model for the processing of spatial cues in the echo pulse is developed. Although for over 50 years "echo suppression" has been the topic of intense theoretical and empirical study within the hearing sciences, only a rudimentary understanding of its mechanisms has emerged. In this article, psychometric functions and results from matching studies are used in developing a model that specifies the perceived position of the echo pulse as a normal deviate, with an expectation that is a logistic function of the echo delay and a variance that depends on interaural time difference. Loss of information in the echo event is quantified as a decline in the efficiency with which the binaural system receives information from the lag impulse. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
98.
Jiři Gregor 《Mathematics of Control, Signals, and Systems (MCSS)》1991,4(2):205-215
A significant part of the theory of one-dimensional linear shift-invariant systems is based on the concept of weighting function
(or impulse response): the output is the convolution of the weighting function with the input. This paper introduces the concept
of linear translation-invariant systems and uses this notion in studying impulse response, z-transforms, and transfer functions
for multidimensional systems. 相似文献
99.
动态规划模型在生产存贮中的应用 总被引:1,自引:0,他引:1
吴明鑫 《陕西科技大学学报》2003,21(5):29-31
利用动态规划模型研究了生产管理中生产存贮问题的数学模型,给出了动态规划的最优性原理和动态规划基本方程,并给出了该数学模型求解的一个实例。 相似文献
100.
环境试验与可靠性试验的关系 总被引:1,自引:1,他引:0
从环境试验和可靠性试验的相关标准入手,详细论述了两者之间的相互关系与区别:互为补充,互为依存,共同发展,共同为保障产品的环境适应性和使用可靠性发挥作用。最后阐述了加强自然环境试验的重要性,它是检验实验结果的基本标准。 相似文献