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   118566篇
  免费   10213篇
  国内免费   4982篇
电工技术   7096篇
技术理论   7篇
综合类   7626篇
化学工业   20489篇
金属工艺   6504篇
机械仪表   7352篇
建筑科学   9701篇
矿业工程   3470篇
能源动力   3522篇
轻工业   7771篇
水利工程   2105篇
石油天然气   7345篇
武器工业   879篇
无线电   13468篇
一般工业技术   14328篇
冶金工业   5553篇
原子能技术   1307篇
自动化技术   15238篇
  2024年   554篇
  2023年   2042篇
  2022年   3554篇
  2021年   4902篇
  2020年   3759篇
  2019年   3168篇
  2018年   3403篇
  2017年   3938篇
  2016年   3322篇
  2015年   4712篇
  2014年   5736篇
  2013年   6816篇
  2012年   7456篇
  2011年   8000篇
  2010年   6994篇
  2009年   6673篇
  2008年   6458篇
  2007年   6116篇
  2006年   6384篇
  2005年   5540篇
  2004年   3776篇
  2003年   3314篇
  2002年   3095篇
  2001年   2829篇
  2000年   2963篇
  1999年   3175篇
  1998年   2684篇
  1997年   2284篇
  1996年   2116篇
  1995年   1839篇
  1994年   1482篇
  1993年   1059篇
  1992年   863篇
  1991年   680篇
  1990年   496篇
  1989年   438篇
  1988年   354篇
  1987年   246篇
  1986年   168篇
  1985年   98篇
  1984年   65篇
  1983年   51篇
  1982年   63篇
  1981年   39篇
  1980年   35篇
  1979年   10篇
  1978年   3篇
  1965年   3篇
  1959年   5篇
  1951年   1篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
In this paper, based on adaptive dynamic programming (ADP) with concurrent learning, the problem of optimal guaranteed cost tracking is studied for a class  相似文献   
72.
本文旨在改善某选厂硫精矿浓密机溢流跑浑问题,对生产现场进行勘察和分析,分析浓密机溢流跑浑的原因,并开展原矿配比和沉降试验研究。对采场原矿矿样和硫精矿矿浆进行系统的试验研究,分别采用不同沉降方案进行条件试验,考察絮凝剂种类、絮凝剂用量、pH调整剂用量、不同药剂之间的配比等条件对沉降的影响,确定合适的原矿配比及合理药剂制度,有效地控制金属在溢流中的损失,充分获取现有产品的蕴含价值。  相似文献   
73.
74.
Simulating the psychological experience of human vision,a road extraction model based on the format tower is proposed to extract the road in the high resolution remote sensing image from the perspective of morphology.Firstly,based on the spectral and texture information,the suspected road targets are extracted by using segmentation technology.Then these targets are classified according to their reliability and extract the road targets for each category.Finally,three types of identified road information are verified and merged,and the continuous smooth road extraction results are obtained.Experiments on real high resolution images show that the results are consistent with the visual perception of the human eye,and the overall classification accuracy is higher,indicating that the algorithm is effective and feasible and has good use value.  相似文献   
75.
Structural and Multidisciplinary Optimization - The overall layout optimization design of an orbital propellant depot involves the optimization of shape, size, and positions of propellant tanks in...  相似文献   
76.
Risk allocation decisions are of critical importance in project management. The present study proposes an explanation for how risk allocation in a contract motivates a contractor to cooperate with a project owner. Theories of risk allocation and trust were used to motivate the research. Using a survey methodology, we collected data concerning 124 construction projects in China. We found that risk allocation influenced the contractor’s role behavior through the contractor’s feeling of being trusted but not the contractor’s trust in the owner. Feeling of being trusted partially mediated the effect of risk allocation on the contractor’s in-role (i.e., contractual) behavior and fully mediated the effect on extra-role behavior. The study introduces a social and psychological view of the impacts of risk allocation to the project and engineering management literature. We contribute to theory by arguing and demonstrating the mediating effect of trust on the relationship between risk allocation and contractor behavior. From a practical standpoint, we conclude that contractual risk allocation has a significant impact on building a trusting relationship between owners and contractors and that contractors who feel trusted perform both contractually mandated actions and actions external to the contract more diligently, resulting in the likelihood of improved outcomes for both parties.  相似文献   
77.
This paper presents two well-instrumented large-scale field tests of PVD-improved soft soil with vacuum and surcharge preloading, respectively. The two large-scale field tests were conducted adjacent to each other with the same preload. A comparative analysis was performed to investigate the performance of subsoil (i.e., the ground settlement, the layered settlement, the lateral displacement of subsoil and pore water pressure) under vacuum preloading and equivalent surcharge preloading. Some design methods were verified based on the field data. Cone Penetration Tests (CPT) and Vane Shear Tests (VST) were conducted to assess the improvement effects on subsoil after preloading. The results showed that as compared with surcharge preloading, vacuum preloading mitigated the differential settlement of the ground. The vacuum pressure transmitted into the soil with a minor loss through the PVD length. From a practical point of view, the improvement effects by vacuum preloading and surcharge preloading were similar in terms of influence depth and soil strength based on the in-situ tests.  相似文献   
78.
为了提高注入剖面测井的准确性,研制了一种新型注入剖面组合测井仪。该仪器由流量处理单元、伽马处理单元、井温处理单元、磁性定位处理单元、调制式传输、电源电路六部分组成。一次下井可同时测取流量、伽马、井温、磁性定位四组参数。具有测取资料精度高、单芯电缆传输、流量可单点测量也可连续测量以厦现场监测和维修方便等特点。  相似文献   
79.
催化裂解多产丙烯新技术   总被引:6,自引:0,他引:6  
介绍了国内外利用蜡油或常压渣油等重质原料的增产丙烯技术CPP,ARGG FDFCC和TSRMP;还介绍了利用富含烯烃的混合碳四和催化裂化汽油等轻质原料的增产丙烯技术OCP,Propylur,Superflex,OCT,Meta-4和BASF公司的丁烯歧化工艺技术.  相似文献   
80.
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