首页 | 官方网站   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   311111篇
  免费   37187篇
  国内免费   26350篇
工业技术   374648篇
  2024年   2129篇
  2023年   5672篇
  2022年   12615篇
  2021年   16152篇
  2020年   11591篇
  2019年   8285篇
  2018年   8566篇
  2017年   9937篇
  2016年   9071篇
  2015年   13928篇
  2014年   17454篇
  2013年   20547篇
  2012年   25524篇
  2011年   26574篇
  2010年   25090篇
  2009年   24311篇
  2008年   24664篇
  2007年   24113篇
  2006年   20986篇
  2005年   17139篇
  2004年   12720篇
  2003年   8775篇
  2002年   8210篇
  2001年   7451篇
  2000年   5754篇
  1999年   2359篇
  1998年   850篇
  1997年   694篇
  1996年   501篇
  1995年   442篇
  1994年   341篇
  1993年   336篇
  1992年   282篇
  1991年   221篇
  1990年   182篇
  1989年   184篇
  1988年   139篇
  1987年   110篇
  1986年   105篇
  1985年   69篇
  1984年   55篇
  1983年   59篇
  1982年   47篇
  1981年   53篇
  1980年   112篇
  1979年   58篇
  1965年   15篇
  1964年   10篇
  1959年   53篇
  1951年   57篇
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
61.
High-cycle fatigue behaviour of titanium 5Al-2.5Sn alloy at room temperature has been studied. S-N curve characterization is performed at different stress ratios ranging from 0 to 0.9 on a subsized fatigue specimen. Both two-stress and three-stress level tests are conducted at different stress ratios to study the cumulative fatigue damage. Life prediction techniques of linear damage rule, double linear damage rule and damage curve approaches are applied, and results are compared with the experimental data. The agreement between prediction and experiment is found to be excellent.  相似文献   
62.
综述评述最近发展起来的陶瓷材料的烧结后冷加工热处理法“控制破碎成形加工法”,着重介绍该方法的由业,阐明其理论与实验基础,同时,介绍其应用并讨论其发展前景。  相似文献   
63.
This paper presents a methodology for specifying the winter and summer peak-load limits for substation transformers that carry a temperature-sensitive load, taking into account the random nature of load and ambient temperature as well as their correlation. With this methodology, we can easily and accurately specify the peak-load limits for each substation transformer once the historical ambient temperature and load data are available. Also, we can collectively specify the peak-load limits for the transformer of each cooling type (OA, OA/FA, or OA/FA/FA) in a geographic region based on the mean and standard deviation of ambient temperatures in that region. Such peak-load limits are useful for power system planning.  相似文献   
64.
用质子激发X荧光分析法测定48只家兔在挠骨骨折愈合过程中骨骼中多种微量元素含量的变化。结果表明,Fe和Sr分别呈鼓凸形和下凹形规律性变化,故Fe和Sr含量的变化可作为骨折愈合过程的指示剂。在骨折愈合过程中发现骨骼和血液中元素钙的相对含量保持不变,故无法为西医用补充钙来治疗骨折的疗法提供依据,但我们的研究结果却表明中医补充微量元素治疗骨折的疗法是有道理的。  相似文献   
65.
The cardioprotective effects of EGb 761 on the release of nitric oxide (NO), the concentration of serum thiobarbituric acid reaction substance (TBARS), the activity of creatine kinase (CK) and the incidence of ventricular arrhythmias were investigated in myocardial ischemia-reperfusion injury in vivo. Using sodium nitrite (NaNO2) as standard source of nitric oxide (NO), we compared the correlation coefficients of the three measuring methods used currently in the determination of NOFe2+(DETC)2 complex with that of the measuring method suggested in this study. The result showed that measuring the whole height of three splitting signals is the best linear correlation to the concentration of NO comparing with other methods in this system. Using this method, we observed the effects of EGb 761 on NOFe2+(DETC)2 complex in myocardial ischemia-reperfusion injury in vivo. The hearts of the Wistar rats were subjected to 30 min of ischemia and 10 min of reperfusion in vivo. Different doses of EGb 761 (25, 50, 100, 200 mg/kg i.p.), superoxide dismutase (SOD, 10(4) U/kg), l-arginine (50 mg/kg i.p.) and nitric oxide synthase (NOS) inhibitor NG-nitro-l-arginine (NNA, 50 mg/kg i.p.) were administered to the ischemia-reperfusion rats. EGb 761 under the dose of 100 mg/kg increased the signal intensity of NOFe2+(DETC)2 complex, while EGb 761 at 200 mg/kg showed an effect of decreasing the signal intensity of NOFe2+(DETC)2 complex. EGb 761 inhibited the formation of TBARS, the release of CK, and mitigated the incidence of ventricular arrhythmias in a dose dependent way. Both l-arginine and SOD increased the signal intensity of NOFe2+(DETC)2 complex and inhibited the formation of TBARS, the leakage of CK and the incidence of ventricular arrhythmia. NNA not only had no protective effects on myocardial injury, but also increased the incidence of reperfusion-induced arrhythmia. In conclusion, EGb 761 has cardiovascular protective effects by means of adjusting the level of NO and inhibiting oxygen free radicals induced lipid peroxidation in myocardial ischemia-reperfusion injury in vivo.  相似文献   
66.
基于物联网技术的监狱人员定位可视化管理系统   总被引:1,自引:0,他引:1  
提出了一种监狱人员定位可视化管理系统的设计和实现方法。该系统基于WLAN的RTLS定位技术,实现对服刑人员、干警、访客等人群的可视化定位管理。文章结合监狱的应用需求,首先给出了系统的总体设计原则;同时在总体原则约束下,对系统功能、总体实现方案、实现框图、应用流程、网络安全等部分进行阐述,给出了标签软硬件设计、定位管理系统的平台选型和软件架构;最后对设计的系统进行了测试。测试结果显示,该可视化定位管理系统的定位精度达到了预期效果。在进一步优化和完善后,即可大规模推广使用。  相似文献   
67.
In group assessment, the focus is on finding high‐authority experts to improve the reliability of assessment results. In this study, we propose an authority updating algorithm while considering the power and judgement reliability of an expert on the basis of social networks and post‐evaluations. A network power index is established and used to reflect the power of an expert while considering social networks. The measurement of the judgement reliability of an expert considers the post‐evaluation of the objects selected by experts, thereby more scientifically reflecting the reliability of experts. The analysis shows the following: although the social‐network structure influences the authority of experts, the influence weakens when the assessment group is a highly or even fully connected group; the network effect may increase the authority of some experts and reduce that of others, and it will weaken as the network connectivity increases; moreover, the judgement reliability and authority of an expert while considering post‐evaluation can encourage him/her to make fair assessments and strive to reduce his/her motivation and cognitive biases.  相似文献   
68.
针对各校对大学生创业实训进行讲授内容的不同,我们在结合本专业的基础上,开展了网络创业实训课程,在创业方向方面不再仅限于网店,而是可以进行多种模式的选择,同时在提高实践性方向,最终的成果也以创业企划书来全面衡量。  相似文献   
69.
基于J2EE平台的供应链管理系统研究   总被引:2,自引:0,他引:2  
介绍了供应链管理的基本原理和实现技术,从平台基础、移植性、扩展性等多个角度对J2EE平台进行了相应的分析,提出了一个基于J2EE平台的供应链管理系统框架,并从系统结构、系统功能模块等方面进行了说明。  相似文献   
70.
IC封装模流道平衡CAE应用   总被引:5,自引:0,他引:5  
分析了热固性塑料的流动行为特点和IC封装充填过程中料流对金丝的冲击状态。用CAE软件Moldflow公司的MPA对流道的平衡进行分析模拟 ,优化浇注系统 ,为提高IC封装产品合格率寻找一种简便有效的途径。  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-23

京公网安备 11010802026262号