全文获取类型
收费全文 | 81754篇 |
免费 | 8545篇 |
国内免费 | 5516篇 |
专业分类
电工技术 | 6184篇 |
技术理论 | 1篇 |
综合类 | 9720篇 |
化学工业 | 8222篇 |
金属工艺 | 6781篇 |
机械仪表 | 6807篇 |
建筑科学 | 10360篇 |
矿业工程 | 4630篇 |
能源动力 | 2636篇 |
轻工业 | 4348篇 |
水利工程 | 3606篇 |
石油天然气 | 4223篇 |
武器工业 | 1002篇 |
无线电 | 5786篇 |
一般工业技术 | 9475篇 |
冶金工业 | 4341篇 |
原子能技术 | 766篇 |
自动化技术 | 6927篇 |
出版年
2024年 | 322篇 |
2023年 | 961篇 |
2022年 | 2563篇 |
2021年 | 2738篇 |
2020年 | 2380篇 |
2019年 | 2147篇 |
2018年 | 2048篇 |
2017年 | 2661篇 |
2016年 | 2873篇 |
2015年 | 3075篇 |
2014年 | 4712篇 |
2013年 | 4617篇 |
2012年 | 5569篇 |
2011年 | 6106篇 |
2010年 | 4646篇 |
2009年 | 4889篇 |
2008年 | 4668篇 |
2007年 | 5733篇 |
2006年 | 5058篇 |
2005年 | 4302篇 |
2004年 | 3743篇 |
2003年 | 3313篇 |
2002年 | 2885篇 |
2001年 | 2466篇 |
2000年 | 2076篇 |
1999年 | 1699篇 |
1998年 | 1348篇 |
1997年 | 1168篇 |
1996年 | 934篇 |
1995年 | 765篇 |
1994年 | 629篇 |
1993年 | 532篇 |
1992年 | 475篇 |
1991年 | 348篇 |
1990年 | 293篇 |
1989年 | 257篇 |
1988年 | 177篇 |
1987年 | 119篇 |
1986年 | 89篇 |
1985年 | 58篇 |
1984年 | 73篇 |
1983年 | 27篇 |
1982年 | 48篇 |
1981年 | 25篇 |
1980年 | 25篇 |
1979年 | 39篇 |
1964年 | 12篇 |
1959年 | 16篇 |
1957年 | 8篇 |
1955年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
ABSTRACTIn this paper, we review some algebraic control system. Precisely, linear and bilinear systems on Euclidean spaces and invariant and linear systems on Lie groups. The fourth classes of systems have a common issue: to any class, there exists an associated subgroup. From this object, we survey the controllability property. Especially, from those coming from our contribution to the theory. 相似文献
2.
Temperature history can have a significant effect on the strength of water-saturated chalk.In this study,hydrostatic stress cycles are applied to understand the mechanical response of chalk samples exposed to temperature cycling between each stress cycle,compared to the samples tested at a constant temperature.The total accumulated strain during a stress cycle and the irreversible strain are reported.Chalk samples from Kansas(USA)and Mons(Belgium),with different degrees of induration(i.e.amount of contact cementation),were used.The samples were saturated with equilibrated water(polar)and nonpolar Isopar H oil to quantify water weakening.All samples tested during 10 stress cycles with varying temperature(i.e.temperature cycled in between each stress cycle)accumulated more strain than those tested at constant temperatures.All the stress cycles were performed at 30℃.The two chalk types behaved similarly when saturated with Isopar H oil,but differently when saturated with water.When saturated with water,the stronger Kansas chalk accumulated more total strain and more irreversible strain within each stress cycle than the weaker Mons chalk. 相似文献
3.
Role stress has received a lot of research attention in psychological, sociological, and organizational studies over the last several decades. Based on a literature review of about 300 journal articles, this article examines prominent consequences of role stress. Specific focus is on researching differences in relationships between facets of role stress (i.e., role ambiguity, role conflict, and role overload) and frequently cited consequences using techniques of meta-analysis. Findings indicate that each role stress facet has a different relationship with the eight consequences studied. Role stress research can benefit from looking at each facet individually in addition to role stress generally. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
4.
5.
The tensile elastic modulus (E), yield stress (σY) and microhardness (MH) of neat and binary and ternary blends of glassy semicrystalline ethylene–vinyl alcohol copolymer (EVOH), a glassy amorphous polyamide and a semicrystalline nylon‐containing ionomer covering a broad range of properties were examined. The tests were carried out on dry and water‐equilibrated samples to produce stiffer and softer materials, respectively. From the results, more accurate linear correlations were found to describe adequately the microhardness, modulus and yield stress of these strongly self‐associated polymers through hydrogen bonding. Copyright © 2003 Society of Chemical Industry 相似文献
6.
7.
房家贵 《石油化工设备技术》2006,27(1):1-5
文章介绍了近年来在催化裂化装置上应用的新设备、新技术,如BY型旋风分离器、BSX型旋分式三级旋风分离器、上下拱型三级旋风分离器、下拱型三级旋风分离器、SHS“自蔓延”技术、SWY外取热器、BWJ型喷嘴、自流浇注料、Actehem高耐磨衬里、弓形钢丝纤维、侧拉环锚固钉、分体可拆人孔等的结构特点及实际应用情况。 相似文献
8.
Kruk Menno R.; Halász József; Meelis Wout; Haller József 《Canadian Metallurgical Quarterly》2004,118(5):1062
Aggressive behavior induces an adrenocortical stress response, and sudden stressors often precipitate violent behavior. Experiments in rats revealed a fast, mutual, positive feedback between the adrenocortical stress response and a brain mechanism controlling aggression. Stimulation of the aggressive area in the hypothalamus rapidly activated the adrenocortical response, even in the absence of an opponent and fighting. Hypothalamic aggression, in turn, was rapidly facilitated by a corticosterone injection in rats in which the natural adrenocortical stress response was prevented by adrenalectomy. The rapidity of both effects points to a fast, mutual, positive feedback of the controlling mechanisms within the time frame of a single conflict. Such a mutual facilitation may contribute to the precipitation and escalation of violent behavior under stressful conditions. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
9.
进入21世纪,随着集成电路的发展,SoC(System on Chip)片上系统应运而生。而作为SoC重要组成部分的嵌入式存储器,在SoC中所占的比重正逐步增加,并起着越来越重要的作用,那么嵌入式存储器与独立的存储器芯片在设计上存在着哪些差异?对此本文将以NOR型闪存为例在制造工艺的选取、衍生产品的设计、功耗与噪声、后端功能仿真、测试与修复等方面进行分析和研究。 相似文献
10.
动力环境网络监控精细管理 总被引:1,自引:0,他引:1
叙述动力环境运行质量分析管理,包括故障管理,性能管理和专题分析管理,以动力环境网络监控细致八微、言之有据的月度分析管理实例展现了其精细管理的效果。 相似文献