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   18382篇
  免费   762篇
  国内免费   22篇
电工技术   221篇
综合类   18篇
化学工业   3820篇
金属工艺   329篇
机械仪表   408篇
建筑科学   1015篇
矿业工程   50篇
能源动力   516篇
轻工业   1722篇
水利工程   123篇
石油天然气   56篇
武器工业   1篇
无线电   1616篇
一般工业技术   3099篇
冶金工业   3108篇
原子能技术   190篇
自动化技术   2874篇
  2023年   158篇
  2022年   302篇
  2021年   464篇
  2020年   344篇
  2019年   370篇
  2018年   428篇
  2017年   393篇
  2016年   492篇
  2015年   428篇
  2014年   529篇
  2013年   1083篇
  2012年   873篇
  2011年   1137篇
  2010年   776篇
  2009年   835篇
  2008年   885篇
  2007年   784篇
  2006年   723篇
  2005年   606篇
  2004年   491篇
  2003年   451篇
  2002年   427篇
  2001年   300篇
  2000年   321篇
  1999年   357篇
  1998年   747篇
  1997年   490篇
  1996年   401篇
  1995年   289篇
  1994年   272篇
  1993年   271篇
  1992年   185篇
  1991年   158篇
  1990年   138篇
  1989年   138篇
  1988年   124篇
  1987年   116篇
  1986年   115篇
  1985年   138篇
  1984年   133篇
  1983年   115篇
  1982年   89篇
  1981年   101篇
  1980年   87篇
  1979年   97篇
  1978年   88篇
  1977年   116篇
  1976年   142篇
  1975年   79篇
  1974年   72篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
3.
4.
Software and Systems Modeling - Many model transformation scenarios require flexible execution strategies as they should produce models with the highest possible quality. At the same time,...  相似文献   
5.
Protection of Metals and Physical Chemistry of Surfaces - In this work, phthalic acid is investigated for its corrosion inhibition properties (for aluminum in solutions of HCl and H2SO4) through...  相似文献   
6.
7.
Antibiotics are potentially a cause of neurotoxicity in dialysis patients, the most common are the beta‐lactams as ceftazidime and cefepime, and few cases have been reported after piperacillin/tazobactam use. This report presents a case of a hypertensive and diabetic 67‐year‐old woman in regular hemodialysis, which previously had a stroke. She was hospitalized presenting pneumonia, which was initially treated with cefepime. Two days after treatment, she presented dysarthria, left hemiparesis, ataxia, and IX and X cranial nerves paresis. Computed tomography showed no acute lesions and cefepime neurotoxicity was hypothesized, and the antibiotic was replaced by piperacillin/tazobactam. The neurologic signs disappeared; however, 4 days after with piperacillin/tazobactam treatment, the neurological manifestations returned. A new computed tomography showed no new lesions, and the second antibiotic regimen withdrawn. After two hemodialysis sessions, the patient completely recovered from neurological manifestations. The patient presented sequentially neurotoxicity caused by two beta‐lactams antibiotics. This report meant to alert clinicians that these antibiotics have dangerous neurological effects in chronic kidney disease patients.  相似文献   
8.
The objective of this research was to investigate the feasibility of visible transmission spectroscopy for the non‐destructive assessment of the freshness of an individual egg. A total of 600 intact white‐shelled eggs of the same flock (Lohmann, 40 weeks of age) were measured. To obtain a considerable variation in freshness, groups consisting of 60 eggs were stored (18 °C, 55% RH) for 0, 2, 4, 6, 8, 10, 12, 14, 16 and 18 days. The non‐destructive spectral measurements were compared with the two most widely used destructive freshness parameters, namely Haugh units and albumen pH. A partial least squares (PLS1) model was built in order to predict Haugh units and pH of the albumen based on the transmission spectra. The correlation coefficients between the predicted value and the measured value were 0.842 and 0.867 for Haugh unit and pH of the albumen, respectively. These results show that the light transmission spectrum of an egg provides quantitative information about egg freshness. Relevant information concerning egg freshness is restricted to the interval between 570 and 750 nm. Furthermore, the models obtained for both destructive parameters were strikingly similar, indicating that Haugh unit and pH have the same physico‐chemical background. Copyright © 2006 Society of Chemical Industry  相似文献   
9.
A novel compact stop band filter consisting of a 50 /spl Omega/ coplanar waveguide (CPW) with split ring resonators (SRRs) etched in the back side of the substrate is presented. By aligning SRRs with the slots, a high inductive coupling between line and rings is achieved, with the result of a sharp and narrow rejection band in the vicinity of the resonant frequency of the rings. In order to widen the stop band of the filter, several ring pairs tuned at equally spaced frequencies within the desired gap are cascaded. The frequency response measured in the fabricated prototype device exhibits pronounced slopes at either side of the stop band and near 0 dBs insertion loss outside that band. Since SRR dimensions are much smaller than signal wavelength, the proposed filters are extremely compact and can be used to reject frequency parasitics in CPW structures by simply patterning properly tuned SRRs in the back side metal. Additional advantages are easy fabrication and compatibility with MMIC or PCB technology.  相似文献   
10.
Methods are described for sample preparation of polycrystalline Ni-based superalloys in order to perform a detailed microstructural characterization. Specific techniques for the precise definition of the various phases present are outlined and these are shown to be useful for the measurement of size, volume fractions and distribution. A number of optical, scanning and transmission microscopy techniques are used to provide the necessary information.  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