全文获取类型
收费全文 | 351448篇 |
免费 | 31695篇 |
国内免费 | 20242篇 |
专业分类
电工技术 | 22909篇 |
技术理论 | 52篇 |
综合类 | 42958篇 |
化学工业 | 47704篇 |
金属工艺 | 14255篇 |
机械仪表 | 19690篇 |
建筑科学 | 42832篇 |
矿业工程 | 16900篇 |
能源动力 | 11424篇 |
轻工业 | 23904篇 |
水利工程 | 15510篇 |
石油天然气 | 14183篇 |
武器工业 | 3597篇 |
无线电 | 26186篇 |
一般工业技术 | 30338篇 |
冶金工业 | 19174篇 |
原子能技术 | 5153篇 |
自动化技术 | 46616篇 |
出版年
2024年 | 1209篇 |
2023年 | 3936篇 |
2022年 | 7459篇 |
2021年 | 9133篇 |
2020年 | 9709篇 |
2019年 | 8630篇 |
2018年 | 8057篇 |
2017年 | 9487篇 |
2016年 | 10896篇 |
2015年 | 11687篇 |
2014年 | 19933篇 |
2013年 | 19528篇 |
2012年 | 23448篇 |
2011年 | 25292篇 |
2010年 | 19618篇 |
2009年 | 20310篇 |
2008年 | 18991篇 |
2007年 | 24305篇 |
2006年 | 22827篇 |
2005年 | 19849篇 |
2004年 | 16900篇 |
2003年 | 15308篇 |
2002年 | 12713篇 |
2001年 | 10703篇 |
2000年 | 9073篇 |
1999年 | 7336篇 |
1998年 | 5675篇 |
1997年 | 4951篇 |
1996年 | 4523篇 |
1995年 | 3795篇 |
1994年 | 3437篇 |
1993年 | 2561篇 |
1992年 | 2273篇 |
1991年 | 1724篇 |
1990年 | 1446篇 |
1989年 | 1249篇 |
1988年 | 1017篇 |
1987年 | 733篇 |
1986年 | 568篇 |
1985年 | 491篇 |
1984年 | 449篇 |
1983年 | 319篇 |
1982年 | 292篇 |
1981年 | 249篇 |
1980年 | 186篇 |
1979年 | 143篇 |
1978年 | 88篇 |
1977年 | 86篇 |
1976年 | 68篇 |
1975年 | 69篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
993.
994.
将Mo与Al2O3粉体按摩尔比为0.3、0.4、0.5配料,混合均匀后通过粉末冶金法制成3种Mo-Al2O3金属陶瓷试样。在1800℃,2h氢气气氛中烧结后,试样的气孔率随Mo含量的增加呈降低趋势,而强度呈增加趋势。同时,随Mo含量增加,金属陶瓷中Al2O3的晶粒尺寸减小,Mo的形态从以弥散状为主转变为以连续状为主。研制的高温型Mo-Al2O3金属陶瓷测温套管(金属与陶瓷摩尔比为0.4)在真空或N2保护条件下测量高温合金熔液温度时,平均使用寿命达到100次。 相似文献
995.
Robustness analysis of responses of vibration control structures with uncertain parameters using interval algorithm 总被引:1,自引:0,他引:1
Variations in system parameters due to uncertainties may result in system performance deterioration. Uncertainties in modeling of structures are often considered to ensure that control system is robust with respect to response errors. Hence, the uncertain concept plays an important role in vibration control of the engineering structures. The paper discusses the robustness of responses of vibration control systems with the uncertain parameters. The vibration control problem of an uncertain system is approximated by a deterministic one. The uncertain parameters are described by interval variables. The uncertain state matrix is constructed directly using system physical parameters and avoided to use bounds in Euclidean norm. The feedback gain matrix is determined based on the deterministic systems, and then it is applied to the actual uncertain systems. A method to calculate the upper and lower bounds of responses of the closed-loop system with uncertain parameters is presented. The upper bounds of responses can be used to estimate the robustness of responses of the controlled system with uncertain parameters. Two numerical examples are given to illustrate the applications of the present approach. 相似文献
996.
计算机系统在钢卷库库区管理上的应用 总被引:1,自引:0,他引:1
主要介绍了钢卷库过程计算机系统(CYC)管理库区的方法,包括钢卷的堆放方式、库区管理的策略,以及平整生产等内容,并且简述了CYC系统的运行情况。 相似文献
997.
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
998.
Four oil families are identified in the southern Gulf of Suez, through high-resolution geochemical studies including gas chromatography, gas chromatography-mass spectrometry, and carbon isotope analyses. Biological features characterize oils in family 1a, suggesting tertiary carbonate source rocks for these oils, rich in type II organic matter and deposited under anoxic depositional environment. Family 1b oil shows minor variations in the source of organic matter and the depositional environment, as it was derived from carbonate source rock with more algal and bacterial contribution and minor input of terrestrial organic sources, deposited under less saline condition compared to family 1a oil. Family 2 oil, although genetically related to family 1a oil, has some distinctive features, such as diasterane to sterane and pristane to phytane ratios, which suggest clay-rich source rocks and a more oxic depositional environment. Also, the lack of oleanane indicates pre-tertiary source rocks for this oil. In contrast, family 3 oil is of mixed sources (marine and non-marine), generated from low sulfur and clay-rich source rock of tertiary and/or younger age. Family 4 oil seems to be mixed from family 1b and family 3 oils, sourced mainly from carbonate source rocks rich in clay minerals with algal and bacterial contributions. Family 4 oil is highly mature, family 1b oil lies within equilibrium values (peak oil generation stage), while the other families are more or less near equilibrium. 相似文献
999.
通过一起由二次回路接线错误引发的事故分析,阐述二次回路的重要性。从设计、安装、调试和管理上对二次回路进行探讨,提出反事故措施和对策,以防止类似事故的发生。 相似文献
1000.
[Correction Notice: An erratum for this article was reported in Vol 20(2) of Canadian Journal of Behavioural Science Revue canadienne des Sciences du comportement (see record 2007-09831-001). The abstract accompanying the original article was incorrect; the correct abstract (in French) is presented in the erratum.] We know little about individuals who are declared unfit to stand trial and/or not guilty by reason of insanity. The few existing studies are characterized by methodological weaknesses, notably by short follow-up periods and a lack of external validity. The present investigation, which aims to evaluate and explain readmissions that occurred during a seven- to nine-year period, corrects only some of these weaknesses. Sixty-one per cent of the subjects were rehospitalized during the period of study. It proved difficult to identify the factors associated with readmission. However, males with a diagnosis of schizophrenia and who had committed violent crimes were found the most likely to be readmitted. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献