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   143655篇
  免费   13055篇
  国内免费   6346篇
电工技术   8694篇
技术理论   8篇
综合类   9521篇
化学工业   24634篇
金属工艺   7991篇
机械仪表   8928篇
建筑科学   11550篇
矿业工程   4093篇
能源动力   4415篇
轻工业   9886篇
水利工程   2680篇
石油天然气   8625篇
武器工业   1062篇
无线电   16430篇
一般工业技术   17431篇
冶金工业   6575篇
原子能技术   1618篇
自动化技术   18915篇
  2024年   702篇
  2023年   2534篇
  2022年   4378篇
  2021年   5933篇
  2020年   4561篇
  2019年   3906篇
  2018年   4250篇
  2017年   4777篇
  2016年   4224篇
  2015年   5740篇
  2014年   7009篇
  2013年   8264篇
  2012年   9022篇
  2011年   9799篇
  2010年   8520篇
  2009年   8121篇
  2008年   7867篇
  2007年   7470篇
  2006年   7673篇
  2005年   6696篇
  2004年   4648篇
  2003年   4237篇
  2002年   4210篇
  2001年   3812篇
  2000年   3620篇
  1999年   3765篇
  1998年   3057篇
  1997年   2648篇
  1996年   2446篇
  1995年   2114篇
  1994年   1663篇
  1993年   1210篇
  1992年   999篇
  1991年   767篇
  1990年   562篇
  1989年   491篇
  1988年   405篇
  1987年   282篇
  1986年   201篇
  1985年   112篇
  1984年   77篇
  1983年   58篇
  1982年   75篇
  1981年   47篇
  1980年   46篇
  1979年   19篇
  1978年   5篇
  1974年   6篇
  1965年   3篇
  1959年   6篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
张旭 《建筑学报》2021,(12):35-41
通过对宜兴丁蜀镇青龙山公园多功能馆项目设计和建造历程的回顾,在自然与人工、城市与建筑、可见与消隐、开放与持存的多重辩证关系中推进和展开关于地景、地方以及边界的讨论,试图进一步探讨在现有的空间规划和土地政策下,建筑基础设施化作为一种设计策略、将特殊场地再次纳入城市结构的可能性.  相似文献   
93.
94.
Rapid and sensitive point-of-care testing (POCT) is an extremely critical mission in practical applications, especially for rigorous military medicine, home health care, and in the third world. Here, we report a visual POCT method for adenosine triphosphate (ATP) detection based on Taylor rising in the corner of quadratic geometries between two rod surfaces. We discuss the principle of Taylor rising, demonstrating that it is significantly influenced by contact angle, surface tension, and density of the sample, which are controlled by ATP-dependent rolling circle amplification (RCA). In the presence of ATP, RCA reaction effectively suppresses Taylor-rising behavior, due to the increased contact angle, density, and decreased surface tension. Without addition of ATP, untriggered RCA reaction is favorable for Taylor rising, resulting in a significant height. With this proposed method, visual sensitive detection of ATP without the aid of other instruments is realized with only a 5 μL droplet, which has good selectivity and a low detection limit (17 nM). Importantly, this visual method provides a promising POCT tool for user-friendly molecular diagnostics.  相似文献   
95.
This paper discusses the compressive performance of perforated brick masonry after fire exposure. Compressive strength tests of the mortar, clay perforated brick, and perforated brick masonry specimens were performed in accordance with ISO834 fire tests of different durations. The temperature distribution of the masonry materials and specimens was simulated using the finite element software ABAQUS, with the thermal parameters of masonry materials recommended by European standard Eurocode 6 and related literature. The compressive strength reduction factors of mortar and clay perforated brick exposed to different fire durations were calculated via the layered method suggested by European standard Eurocode 1. In addition, the compressive strength reduction factors after cooldown were obtained from the experimental data of the masonry materials, and by considering further reductions in the compressive strength after cooling from high temperatures. Experimental data of the masonry specimens were compared with the numerical results obtained using the reduction factors proposed in this work. The comparison revealed an overall acceptable approximation. Thus, the method presented in this paper can be used to evaluate the residual capacity of masonry structures after fire.  相似文献   
96.
97.
98.
The chlorothiophenoxy radicals (CTPRs) are key intermediate species in the formation of polychlorinated dibenzothiophenes/thianthrenes (PCDT/TAs). In this work, the formation of CTPRs from the complete series reactions of 19 chlorothiophenol (CTP) congeners with H and OH radicals were investigated theoretically by using the density functional theory (DFT) method. The profiles of the potential energy surface were constructed at the MPWB1K/6-311+G(3df,2p)//MPWB1K/6-31+G(d,p) level. The rate constants were evaluated by the canonical variational transition-state (CVT) theory with the small curvature tunneling (SCT) contribution at 600–1200 K. The present study indicates that the structural parameters, thermal data, and rate constants as well as the formation potential of CTPRs from CTPs are strongly dominated by the chlorine substitution at the ortho-position of CTPs. Comparison with the study of formation of chlorophenoxy radicals (CPRs) from chlorophenols (CPs) clearly shows that the thiophenoxyl-hydrogen abstraction from CTPs by H is more efficient than the phenoxyl-hydrogen abstraction from CPs by H, whereas the thiophenoxyl-hydrogen abstraction from CTPs by OH is less impactful than the phenoxyl-hydrogen abstraction from CPs by OH. Reactions of CTPs with H can occur more readily than that of CTPs with OH, which is opposite to the reactivity comparison of CPs with H and OH.  相似文献   
99.
100.
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