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   434662篇
  免费   12488篇
  国内免费   5199篇
电工技术   11908篇
技术理论   11篇
综合类   6849篇
化学工业   65007篇
金属工艺   20233篇
机械仪表   19742篇
建筑科学   16689篇
矿业工程   4395篇
能源动力   10917篇
轻工业   36143篇
水利工程   4921篇
石油天然气   9553篇
武器工业   696篇
无线电   53664篇
一般工业技术   78995篇
冶金工业   57938篇
原子能技术   5684篇
自动化技术   49004篇
  2023年   2255篇
  2022年   3884篇
  2021年   5745篇
  2020年   4355篇
  2019年   4221篇
  2018年   14171篇
  2017年   15239篇
  2016年   10448篇
  2015年   6504篇
  2014年   8554篇
  2013年   18086篇
  2012年   15811篇
  2011年   25165篇
  2010年   21714篇
  2009年   21374篇
  2008年   21532篇
  2007年   23141篇
  2006年   14213篇
  2005年   16500篇
  2004年   12772篇
  2003年   11779篇
  2002年   9978篇
  2001年   9746篇
  2000年   9218篇
  1999年   10123篇
  1998年   19169篇
  1997年   13827篇
  1996年   10816篇
  1995年   8410篇
  1994年   7243篇
  1993年   6756篇
  1992年   4931篇
  1991年   4487篇
  1990年   4115篇
  1989年   3849篇
  1988年   3635篇
  1987年   2872篇
  1986年   2679篇
  1985年   3315篇
  1984年   2897篇
  1983年   2634篇
  1982年   2426篇
  1981年   2443篇
  1980年   2242篇
  1979年   2075篇
  1978年   1896篇
  1977年   2193篇
  1976年   2754篇
  1975年   1594篇
  1973年   1565篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Feature-based methods have been developed in the past decades for the registration of optical satellite images. However, it is still a challenging problem to handle well the registration between medium and high spatial resolution images due to the large difference of the spatial structural features and local details for the same objects. In this study, an automated co-registration technique is proposed that integrates an improved SIFT (I-SIFT) and a novel matching strategy called spatial consistency constraints (SCC) to cope with the large difference in spatial resolutions between the image pair. Three constraints on angle, distance, and ratio are introduced to re the initial matching features obtained by I-SIFT. Three groups of experiments were conducted to validate the effectiveness of the proposed method. The experiments used high resolution multispectral and panoramic SPOT 5/6 images and Landsat 5/8 orthorectification images. Experimental results show that the registration error lies in about 1 pixel of high-resolution images and demonstrate that the proposed I-SIFT-SCC approach is suitable for fine registration of optical satellite images from medium spatial resolution to high spatial resolution with resolution ratio up to 6.  相似文献   
2.
3.
4.
5.
ABSTRACT

Bacteriocin is a proteinaceous biomolecule produced by bacteria (both Gram-positive and Gram-negative) that exhibits antimicrobial activity against closely related species, and food-borne pathogens. It has recently gained importance and attracted the attention of several researchers looking to produce it from various substrates and bacterial strains. This ushers in a new era of food preservation where the use of bacteriocin in food products will be an alternative to chemical preservatives, and heat treatment which are understood to cause unwanted side effects, and reduce sensory and nutritional quality. However, this new market depends on the success of novel downstream separation schemes from various types of crude feedstocks which are both effective and economic. This review focuses on the downstream separation of bacteriocin from various sources using both conventional and novel techniques. Finally, recommendations for future interesting areas of research that need to be pursued are highlighted.  相似文献   
6.
7.
8.
A layer-by-layer analysis of the structures, the phase compositions, and the defect substructures of differentially hardened rails has been carried by optical and transmission electron microscopy. It is found that the material volume of the rail head fillet is cooled faster than the volume located along the central axis.  相似文献   
9.
10.
Wu  Li  Li  Jing  Fu  Caixia  Kühn  Bernd  Wang  Xiaolin 《Magma (New York, N.Y.)》2019,32(4):501-509
Magnetic Resonance Materials in Physics, Biology and Medicine - To investigate the value of using diffusion-weighted imaging (DWI) and intravoxel incoherent motion DWI (IVIM-DWI) to assess the...  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