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   61312篇
  免费   4998篇
  国内免费   2701篇
电工技术   3764篇
技术理论   3篇
综合类   4128篇
化学工业   10319篇
金属工艺   3498篇
机械仪表   3984篇
建筑科学   4755篇
矿业工程   1887篇
能源动力   1755篇
轻工业   4206篇
水利工程   1096篇
石油天然气   4107篇
武器工业   544篇
无线电   6596篇
一般工业技术   7317篇
冶金工业   2758篇
原子能技术   603篇
自动化技术   7691篇
  2024年   279篇
  2023年   1105篇
  2022年   1934篇
  2021年   2669篇
  2020年   2095篇
  2019年   1688篇
  2018年   1880篇
  2017年   2077篇
  2016年   1792篇
  2015年   2445篇
  2014年   3182篇
  2013年   3514篇
  2012年   3836篇
  2011年   4296篇
  2010年   3737篇
  2009年   3475篇
  2008年   3405篇
  2007年   3140篇
  2006年   3215篇
  2005年   2672篇
  2004年   1919篇
  2003年   1688篇
  2002年   1645篇
  2001年   1434篇
  2000年   1328篇
  1999年   1550篇
  1998年   1301篇
  1997年   1138篇
  1996年   1015篇
  1995年   841篇
  1994年   675篇
  1993年   486篇
  1992年   426篇
  1991年   266篇
  1990年   213篇
  1989年   166篇
  1988年   123篇
  1987年   83篇
  1986年   69篇
  1985年   45篇
  1984年   36篇
  1983年   33篇
  1982年   32篇
  1981年   19篇
  1980年   18篇
  1979年   7篇
  1959年   2篇
  1940年   3篇
  1929年   1篇
  1928年   1篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Climate change raises many concerns for urban water management because of the effects on all aspects of the hydrological cycle. Urban water infrastructure has traditionally been designed using historical observations and assuming stationary climatic conditions. The capability of this infrastructure, whether for storm-water drainage, or water supply, may be over- or under-designed for future climatic conditions. In particular, changes in the frequency and intensity of extreme rainfall events will have the most acute effect on storm-water drainage systems. Therefore, it is necessary to take future climatic conditions into consideration in engineering designs in order to enhance water infrastructure investment planning practices in a long time horizon. This paper provides the initial results of a study that is examining ways to enhance urban infrastructure investment planning practices against changes in hydrologic regimes for a changing climate. Design storms and intensity-duration-frequency curves that are used in the engineering design of storm-water drainage systems are developed under future climatic conditions by empirically adjusting the general circulation model output, and using the Gumbel distribution and the Chicago method. Simulations are then performed on an existing storm-water drainage system from NE Calgary to investigate the resiliency of the system under climate change.  相似文献   
2.
A novel cholesterol‐imprinted polymer (CMIP‐H) was prepared by a hybrid method of covalent imprinting and non‐covalent imprinting. This approach involves the copolymerization of a template‐containing monomer, cholesteryl 2‐hydroxyethyl methacrylate carbonate, and a cross‐linker, followed by hydrolysis to afford a flexible guest‐binding site accompanied with the easy and efficient removal of a ‘sacrificial spacer’. The effect of solvent on the binding capacity of CMIP‐H towards cholesterol was studied, indicating that a good binding capacity towards cholesterol could be achieved in a less‐polar solvent. The binding experiments of CMIP‐H towards a series of structural analogues of cholesterol, including cholesterol acetate, progesterone and stigmasterol, were carried out in hexane. The results showed that CMIP‐H almost did not bind cholesterol acetate at all because the hydrogen‐bonding site is blocked. It exhibited a similar binding towards both cholesterol and stigmasterol, but much higher binding towards progesterone. Copyright © 2005 Society of Chemical Industry  相似文献   
3.
4.
There is great interest today in massively parallel analytical strategies as a way to accelerate the rate of discovery in biological research; among them being 'biochips' and 'laboratories-on-a-chip'. The concept in the 'chip' approach is that minaturization will allow large numbers of operations to be performed in parallel in a small space, as in electronics. Proceeding with the semiconductor analogy, this paper demonstrates that in situ micromachining can be used to simultaneously fabricate millions of micrometer size, particle like structures in multiple liquid chromatography columns on a single wafer. Reduction of this widely used bioanalytical tool to the nanoliter volume, parallel processing, chip format is a significant step toward laboratories-on-a-chip.  相似文献   
5.
6.
7.
In this paper, we present efficient VLSI architectures for full-search block-matching motion estimation (BMME) algorithm. Given a search range, we partition it into sub-search arrays called tiles. By fully exploiting data dependency within a tile, efficient VLSI architectures can be obtained. Using the proposed VLSI architectures, all the block-matchings in a tile can be processed in parallel. All the tiles within a search range can be processed serially or concurrently depending on various requirements. With the consideration of processing speed, hardware cost, and I/O bandwidth, the optimal tile size for a specific video application is analyzed. By partitioning a search range into tiles with appropriate size, flexible VLSI designs with different throughput can be obtained. In this way, cost effective VLSI designs for a wide range of video applications, from H.261 to HDTV, can be achieved.  相似文献   
8.
9.
Intensity distribution functions on the image plane are derived under the assumption that a multimode optic fiber is illuminated by a light source which can be approximated by infinite uniangular beams carrying equal power. The application of the theory to a Lambertian source is discussed. Experimental results, based on the observation of the light intensity distribution imaged on an opaque screen and collected by a digital camera, are presented. The theoretical and experimental data are compared to verify that the intensity function is an accurate model for describing the realistic approach to sensor design. The limitations of the uniangular and uniform intensity distribution models are discussed on the basis of theoretical and experimental results  相似文献   
10.
The microscopic structures of PLZT(7.9/70/30 and x/65/35, x = 7 or 8) ceramics were studied by means of transmission electron microscopy. The presence of micro-regions in PLZTs was first verfied.  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