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   736篇
  免费   40篇
  国内免费   1篇
电工技术   13篇
化学工业   169篇
金属工艺   8篇
机械仪表   12篇
建筑科学   23篇
矿业工程   2篇
能源动力   26篇
轻工业   89篇
水利工程   5篇
石油天然气   3篇
无线电   79篇
一般工业技术   162篇
冶金工业   73篇
原子能技术   1篇
自动化技术   112篇
  2024年   2篇
  2023年   15篇
  2022年   12篇
  2021年   21篇
  2020年   19篇
  2019年   18篇
  2018年   24篇
  2017年   23篇
  2016年   23篇
  2015年   25篇
  2014年   29篇
  2013年   56篇
  2012年   54篇
  2011年   67篇
  2010年   50篇
  2009年   36篇
  2008年   36篇
  2007年   26篇
  2006年   41篇
  2005年   24篇
  2004年   23篇
  2003年   15篇
  2002年   8篇
  2001年   11篇
  2000年   4篇
  1999年   15篇
  1998年   26篇
  1997年   17篇
  1996年   12篇
  1995年   12篇
  1994年   8篇
  1993年   6篇
  1992年   3篇
  1991年   1篇
  1990年   1篇
  1989年   3篇
  1988年   2篇
  1987年   1篇
  1986年   2篇
  1984年   1篇
  1981年   2篇
  1976年   1篇
  1973年   1篇
  1968年   1篇
排序方式: 共有777条查询结果,搜索用时 46 毫秒
1.
Pinhão seed is an unconventional source of starch and the pines grow up in native forests of southern Latin America. In this study, pinhão starch was adjusted at 15, 20 and 25% moisture content and heated to 100, 110 and 120 °C for 1 h. A decrease in λ max (starch/iodine complex) was observed as a result of increase in temperature and moisture content of HMT. The ratio of crystalline to amorphous phase in pinhão starch was determined via Fourier transform infra red by taking 1045/1022 band ratio. A decrease in crystallinity occurred as a result of HMT. Polarised light microscopy indicated a loss of birefringence of starch granules under 120 °C at 25% moisture content. Granule size distribution was further confirmed via scanning electron microscopy which showed the HMT effects. These results increased the understanding on molecular and structural properties of HMT pinhão starch and broadened its food and nonfood industrial applications.  相似文献   
2.
Bile acids have been reported as important cofactors promoting human and murine norovirus (NoV) infections in cell culture. The underlying mechanisms are not resolved. Through the use of chemical shift perturbation (CSP) NMR experiments, we identified a low-affinity bile acid binding site of a human GII.4 NoV strain. Long-timescale MD simulations reveal the formation of a ligand-accessible binding pocket of flexible shape, allowing the formation of stable viral coat protein–bile acid complexes in agreement with experimental CSP data. CSP NMR experiments also show that this mode of bile acid binding has a minor influence on the binding of histo-blood group antigens and vice versa. STD NMR experiments probing the binding of bile acids to virus-like particles of seven different strains suggest that low-affinity bile acid binding is a common feature of human NoV and should therefore be important for understanding the role of bile acids as cofactors in NoV infection.  相似文献   
3.
4.
We report a wavelength-switchable fiber ring laser that includes a Bragg grating-based acoustooptic superlattice modulator. Wavelength switching of the laser emission is achieved by controlling the peak reflectivity of the different reflection bands that appear on both sides of the Bragg wavelength when a longitudinal acoustic wave propagates along the grating.  相似文献   
5.
6.
We describe a novel microfluidic perfusion system for high-resolution microscopes. Its modular design allows pre-coating of the coverslip surface with reagents, biomolecules, or cells. A poly(dimethylsiloxane) (PDMS) layer is cast in a special molding station, using masters made by photolithography and dry etching of silicon or by photoresist patterning on glass or silicon. This channel system can be reused while the coverslip is exchanged between experiments. As normal fluidic connectors are used, the link to external, computer-programmable syringe pumps is standardized and various fluidic channel networks can be used in the same setup. The system can house hydrogel microvalves and microelectrodes close to the imaging area to control the influx of reaction partners. We present a range of applications, including single-molecule analysis by fluorescence correlation spectroscopy (FCS), manipulation of single molecules for nanostructuring by hydrodynamic flow fields or the action of motor proteins, generation of concentration gradients, trapping and stretching of live cells using optical fibers precisely mounted in the PDMS layer, and the integration of microelectrodes for actuation and sensing.  相似文献   
7.
The authors investigated relationships between marijuana and inhalant use and several cultural and demographic factors in Anglo American and Hispanic American adolescents (N=1,094). Outcome measures assessed lifetime and 30-day marijuana and inhalant use. Predictors and covariates used in logistic regression analyses were region, grade, gender, knowledge, acculturation, familism, and parental monitoring. Hispanic Americans exhibited higher usage across all measures. In this group, high acculturation was associated with low marijuana, but high inhalant, use. Across all participants, positive family relations and parental monitoring were strongly associated with attenuated marijuana use hut only among those most knowledgeable about drugs. Familism and monitoring were not associated with diminished usage among the less knowledgeable. For inhalants, monitoring combined with high knowledge or high familism was associated with diminished usage. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
8.
Resource allocation involves deciding how to divide a resource of limited availability among multiple demands in a way that optimizes current objectives. In this brief paper we focus on one type of distributed resource allocation problem where via an imperfect communication network multiple processors can share the load presented by multiple task types. We introduce asynchronous “cooperative” resource allocation strategies, and show that they lead to a bounded cumulative demand.  相似文献   
9.
Compiler Verification has been identified as a vital process in the implementation of correct safety-critical systems. We extend here Hoare's refinement-algebra approach to compilation in order to include real-time languages in which processes interact asynchronously via communication queues. The existence of unique fixed-points is exploited to verify the implementation of crucial operators such as asynchronous input, delay and timeout.  相似文献   
10.
Examined the relationship between aphasia type and lesion site in 80 subcortical stroke patients. Ss were classified as affected by aphasia, dysarthria, and nonaphasia, nondysarthria. Sites of lesions were identified by means of computerized tomography (CT) scan. No correlation between site of lesions and category group was found. Lesions of the same subcortical structures yielded different neurolinguistic impairment, whereas comparable linguistic patterns were observed with lesions of different deep areas. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  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