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   21857篇
  免费   1415篇
  国内免费   861篇
电工技术   1380篇
综合类   1396篇
化学工业   1227篇
金属工艺   2590篇
机械仪表   1760篇
建筑科学   1757篇
矿业工程   473篇
能源动力   356篇
轻工业   1343篇
水利工程   249篇
石油天然气   1851篇
武器工业   265篇
无线电   1945篇
一般工业技术   2848篇
冶金工业   665篇
原子能技术   185篇
自动化技术   3843篇
  2024年   22篇
  2023年   178篇
  2022年   272篇
  2021年   419篇
  2020年   424篇
  2019年   368篇
  2018年   374篇
  2017年   545篇
  2016年   625篇
  2015年   862篇
  2014年   1270篇
  2013年   1212篇
  2012年   1511篇
  2011年   1632篇
  2010年   1376篇
  2009年   1339篇
  2008年   1341篇
  2007年   1496篇
  2006年   1355篇
  2005年   1210篇
  2004年   1000篇
  2003年   885篇
  2002年   761篇
  2001年   668篇
  2000年   527篇
  1999年   449篇
  1998年   379篇
  1997年   268篇
  1996年   251篇
  1995年   211篇
  1994年   163篇
  1993年   121篇
  1992年   109篇
  1991年   91篇
  1990年   75篇
  1989年   48篇
  1988年   37篇
  1987年   19篇
  1986年   17篇
  1985年   29篇
  1984年   25篇
  1983年   30篇
  1982年   30篇
  1981年   7篇
  1978年   9篇
  1965年   17篇
  1962年   7篇
  1959年   5篇
  1957年   5篇
  1955年   5篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
An on-site laboratory with direct access to cleaned and conditioned steel mill gases was recently put into operation. The long-term performance and stability of Clariant's MegaMax®800 methanol synthesis catalyst utilizing steel mill gases is currently being investigated. First test results revealed that in order to investigate deactivation mechanisms arising from particular properties of the cleaned steel mill gases, the overlaying effect of thermal deactivation of the catalyst has to be minimized.  相似文献   
2.
This paper investigates the influence of suspension characteristics on microstructure and performance of suspensions plasma sprayed (SPS) thermal barrier coatings (TBCs). Five suspensions were produced using various suspension characteristics, namely, type of solvent and solid load content, and the resultant suspensions were utilized to deposit five different TBCs under identical processing conditions. The produced TBCs were evaluated for their performance i.e. thermal conductivity, thermal cyclic fatigue (TCF) and thermal shock (TS) lifetime. This experimental study revealed that the differences in the microstructure of SPS TBCs produced using varied suspensions resulted in a wide-ranging overall TBC performance. All TBCs exhibited thermal conductivity lower than 1 W/(m. K) except water-ethanol mixed suspension produced TBC. The TS lifetime was also affected to a large extent where 10 wt % solid loaded ethanol and 25 wt % solid loaded water suspensions produced TBCs exhibited the highest and the lowest lifetime, respectively. On the contrary, TCF lifetime was not as significantly affected as thermal conductivity and TS lifetime, and all ethanol suspensions showed marginally better TCF lifetime than water and ethanol-water mixed suspensions deposited TBCs.  相似文献   
3.
4.
现场可编程门阵列(FPGA)内部资源众多,其中互连资源出现故障的概率远远高于片内其他资源,而在以往许多互连测试研究中,所生成的测试配置存在无法覆盖反馈桥接故障的难题,所以较难有测试配置实现故障列表的100%覆盖。因此通过约束桥接故障只发生在单个查找表(LUT)内的信号线上,并结合单项函数,对反馈桥接故障模型进行优化改进,从根本上解决难题;然后对优化后的反馈桥接故障设置相应的约束条件,再使用布尔可满足性理论(SAT)生成满足约束条件的测试配置。采用优化后的故障模型对ISCAS"89基准电路进行了测试配置生成实验,结果表明生成的测试向量解决了反馈桥接故障的覆盖难题,并且在实现故障列表的100%覆盖下,优化后的故障模型所需要的测试配置数最少。  相似文献   
5.
Terahertz (THz) imaging is expected to become powerful tools for non-destructive inspections. To ensure the practical use of THz non-destructive monitoring, versatile THz imagers with adjustable designs that can eliminate the complexities and the bulkiness of the device are urgently required. Herein, a self-aligned filtration process for a 2D, free-standing carbon nanotube film array and its application to a THz video camera patch are reported. The presented techniques enable a) to freely design the camera size, sensor array pattern, and suspended shape according to its applications, b) to cut the camera patch into desired shapes, and c) to attach them to the objects that are intended to be measured. Real-time, non-destructive monitoring of various infrastructures is demonstrated. These results indicate that it can function regardless of restrictions, such as the shapes and locations of the measurement samples, thus providing a strong possibility for use in future non-destructive sensor networks.  相似文献   
6.
现阶段,为了探索创新性的发展途径,生态环境监测机构应始终增强风险控制意识。应加强风险管理,立足于风险控制,以求不断健康发展。  相似文献   
7.
汪广轮 《云南化工》2019,(1):165-166
我国的大多数油田都已步入了开发后期阶段,生产井含水较高,对油气田开发动态监测技术有着更高的要求。油气田开发动态监测作为油田生产工作的基础,是油田开发过程中不可或缺的一个环节,是油气田合理开发的保障。根据油气田开发动态监测技术内容,提出其发展面临的主要问题。并基于上述研究,对数值试井分析技术进行分析,预测现阶段油气田开发动态监测技术的发展方向。  相似文献   
8.
9.
Inherited cardiomyopathies are frequent causes of sudden cardiac death (SCD), especially in young patients. Despite at the autopsy they usually have distinctive microscopic and/or macroscopic diagnostic features, their phenotypes may be mild or ambiguous, possibly leading to misdiagnoses or missed diagnoses. In this review, the main differential diagnoses of hypertrophic cardiomyopathy (e.g., athlete’s heart, idiopathic left ventricular hypertrophy), arrhythmogenic cardiomyopathy (e.g., adipositas cordis, myocarditis) and dilated cardiomyopathy (e.g., acquired forms of dilated cardiomyopathy, left ventricular noncompaction) are discussed. Moreover, the diagnostic issues in SCD victims affected by phenotype-negative hypertrophic cardiomyopathy and the relationship between myocardial bridging and hypertrophic cardiomyopathy are analyzed. Finally, the applications/limits of virtopsy and post-mortem genetic testing in this field are discussed, with particular attention to the issues related to the assessment of the significance of the genetic variants.  相似文献   
10.
Blowdown testing offers a cost-effective experimental tool to replicate the aerothermal conditions in numerous high speed systems. The wind tunnel must replicate the inlet operating conditions, while the spatial and time dependent inlet flow conditions should be assessed carefully. This paper provides a design methodology and rules that ensure adequate flow conditioning in high inlet pressure wind tunnels suitable for subsonic and supersonic operation with mass-flow limits ranging from 1 kg/s to 25 kg/s, Reynolds numbers from 103 (1/m) to 4x107 (1/m), and Mach numbers from 0.01 up to 6. The quality of the proposed flow conditioning system was evaluated using stereo PIV measurements combined with hotwire, Pitot probe, and total flow temperature traverses.  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