首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   27513篇
  免费   3474篇
  国内免费   2538篇
电工技术   2330篇
综合类   2725篇
化学工业   2237篇
金属工艺   3029篇
机械仪表   2256篇
建筑科学   4543篇
矿业工程   1537篇
能源动力   636篇
轻工业   971篇
水利工程   1166篇
石油天然气   1095篇
武器工业   391篇
无线电   1795篇
一般工业技术   5464篇
冶金工业   1336篇
原子能技术   282篇
自动化技术   1732篇
  2024年   141篇
  2023年   424篇
  2022年   812篇
  2021年   1037篇
  2020年   1058篇
  2019年   1002篇
  2018年   852篇
  2017年   1152篇
  2016年   1197篇
  2015年   1215篇
  2014年   1698篇
  2013年   1852篇
  2012年   2011篇
  2011年   2186篇
  2010年   1618篇
  2009年   1717篇
  2008年   1551篇
  2007年   1696篇
  2006年   1629篇
  2005年   1320篇
  2004年   1130篇
  2003年   998篇
  2002年   838篇
  2001年   692篇
  2000年   598篇
  1999年   516篇
  1998年   428篇
  1997年   382篇
  1996年   293篇
  1995年   279篇
  1994年   206篇
  1993年   177篇
  1992年   172篇
  1991年   117篇
  1990年   100篇
  1989年   96篇
  1988年   67篇
  1987年   39篇
  1986年   27篇
  1985年   37篇
  1984年   23篇
  1983年   24篇
  1982年   13篇
  1981年   11篇
  1980年   17篇
  1979年   19篇
  1961年   5篇
  1960年   6篇
  1959年   7篇
  1955年   8篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
81.
化工离心泵的可靠性分析   总被引:1,自引:1,他引:0  
对石油化工设备安全性和维修技术的研究,需要设备运行故障率等可靠性数据。探讨了如何应用传统可靠性理论知识,并结合国内外相关标准规范和运行数据的统计分析来确定离心泵的可靠性数据的方法。  相似文献   
82.
Continuous renal replacement therapy (CRRT) is becoming the treatment of choice for critically ill patients with acute renal failure around the world. In particular, CRRT is used for patients with combined liver and acute renal failure, because they are often hemodynamically unstable. The question arises as to whether the use of CRRT should be extended to those patients with acute and chronic liver failure who do not have dialysis-dependent renal failure. CRRT could potentially allow some detoxification by removing water-soluble toxins and also allow regulation of intravascular volume and correction of sodium and other electrolyte and acid–base imbalances. By providing homeostatic control, CCRT could potentially help support patients by bridging to liver transplantation and managing those who eventually recover with hepatic regeneration.  相似文献   
83.
Using the synthesis of the kinetic concept on solid strength and the Coulomb - Mohr strength theory as the base, the failure conditions taking into account the time and temperature factors are obtained.  相似文献   
84.
Fuel system assemblies used on recreational watercraft failed after a short time in service in a seawater environment. Examination of the assemblies revealed significant degradation of the polyacetal connectors of the wire subassemblies. Optical and microscopic evaluations indicated the complete loss of connector material implying decomposition of the resin, along with mud-cracking and a rough surface morphology signifying chemical attack. An elemental analysis performed on both an intact connector and degraded connector suggested a potential chemical agent in the form of zinc chloride. At elevated temperatures, concentrated zinc chloride solutions are known to decompose polyacetal resins. The source of the zinc chloride was established as corrosion products that resulted during the dezincification of the internal brass connector through exposure to saltwater in the application.  相似文献   
85.
介绍沙角发电C厂2号发电机转子接地检测装置的基本原理和在装置发出报警信号后的分析和判断过程。对该装置出现故障后ALSTOM公司提出的临时检测方案作了分析,指出了该方案的不足之处,提出并实施改进后的临时检测方案。  相似文献   
86.
The relation between the initial unbalance and the output signal of bridge circuits when acted upon simultaneously by the physical factor being measured and the temperature of the surroundings when the bridge is supplied from a voltage or current source is investigated. Analytic relations are obtained which explain the temperature dependence of the useful output voltage under external physical action. __________ Translated from Izmeritel’naya Tekhnika, No. 1, pp. 48–49, 2007.  相似文献   
87.
17-4 PH stainless steel is used as internal drive shaft material in liquid engine pumps. One of the drive shafts failed during operation. The shaft pieces were in contact for short duration after failure, which has resulted in abrasion of fractured surfaces. Samples from the location of failure were taken, and investigation of the failure was carried out using optical and scanning electron microscopy. The microstructural analysis of the material and fractographic analysis of the fractured surface show that the failure was caused by excessive torsion.  相似文献   
88.
曹红梅 《山西建筑》2003,29(18):34-35
介绍了阳泉市煤矿采空区对公路建设所造成的危害,对其上覆岩层变形破坏的地质因素及其破坏机理作了分析,指出应该采取各种措施减少对公路的破坏。  相似文献   
89.
混凝土输送泵的常见故障及排除   总被引:1,自引:0,他引:1  
王永平 《山西建筑》2003,29(12):120-121
介绍了混凝土输送泵的常见故障,阐述了混凝土输送泵墙管的排除方法,指出只有认真分析造成故障的各种原因,才能按照先外后内、先易后难的原则进行故障处理。  相似文献   
90.
This study examined organizational family-responsive policies, perceptions of the organization as family supportive, and supervisor support as issues that may be salient to the experience of conflict between paid employment (work) and family roles. Data were collected from 355 managerial personnel in New Zealand. Although work-family conflict and psychological strain were strongly linked, the availability of organizational policies had no significant association with levels of conflict or strain, whereas policy usage was related only to work-to-family interference and not to family-to-work interference. On the other hand, perceptions of the organization as family supportive and supervisor support for work-family balance displayed significant relationships with key variables, highlighting the importance of these variables for interventions designed to ameliorate the negative impact of work-family conflict on managerial well-being. Implications for the effective implementation of family-responsive interventions are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号