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   6904篇
  免费   175篇
  国内免费   27篇
电工技术   74篇
综合类   8篇
化学工业   976篇
金属工艺   157篇
机械仪表   119篇
建筑科学   51篇
矿业工程   16篇
能源动力   307篇
轻工业   243篇
水利工程   36篇
石油天然气   20篇
无线电   654篇
一般工业技术   1165篇
冶金工业   2607篇
原子能技术   35篇
自动化技术   638篇
  2023年   72篇
  2022年   100篇
  2021年   172篇
  2020年   146篇
  2019年   124篇
  2018年   169篇
  2017年   157篇
  2016年   185篇
  2015年   108篇
  2014年   185篇
  2013年   418篇
  2012年   218篇
  2011年   235篇
  2010年   198篇
  2009年   268篇
  2008年   180篇
  2007年   132篇
  2006年   134篇
  2005年   115篇
  2004年   103篇
  2003年   108篇
  2002年   90篇
  2001年   70篇
  2000年   66篇
  1999年   119篇
  1998年   722篇
  1997年   408篇
  1996年   353篇
  1995年   229篇
  1994年   187篇
  1993年   181篇
  1992年   78篇
  1991年   108篇
  1990年   101篇
  1989年   65篇
  1988年   72篇
  1987年   76篇
  1986年   69篇
  1985年   81篇
  1984年   31篇
  1983年   25篇
  1982年   30篇
  1981年   42篇
  1980年   30篇
  1979年   30篇
  1978年   34篇
  1977年   53篇
  1976年   135篇
  1975年   21篇
  1973年   13篇
排序方式: 共有7106条查询结果,搜索用时 15 毫秒
101.
Nine isolates of bacteria biochemically resembling Shigella dysenteriae but not belonging to the 10 recognized serotypes were isolated from patients with diarrhea in Bangladesh. Further studies suggested that two, one, and six isolates belonged to the recently recognized S. dysenteriae serotypes 11, 12, and 13, respectively.  相似文献   
102.
103.
104.
Long-period fibre gratings in specially designed birefringent few-mode fibres are used to demonstrate spectrally flat polarisers with bandwidths of 10 nm and polarisation extinction levels of 20 dB. This is enabled by the special dispersive properties of few-mode fibres, yielding fibre polarisers with performance approaching that of bulk-optic devices.  相似文献   
105.
106.
The classical stochastic analog of the deterministic linear system in engineering is the linear system driven by white noise. As the promise of artificial neural networks in modeling nonlinear systems continues to grow, the need for a stochastic analog with quantitative foundations for analysis and synthesis will increase. This paper presents recent work in this direction, examining recurrent neural nets (RNN driven by white noise. We examine the effect of noise on the typical continuous-time RNN model. First, we perform qualitative analysis establishing uniform boundedness of moments of the neuron states over time. To enable practical application, however, it is necessary to relate these properties to useful measures that can be estimated. We thus subsequently derive bias and variance measures for the noisy RNN with respect to the corresponding deterministic RNN. This has significant practical implications, since net design is nonminimal in the sense that several nets can solve the same problem. The results allow the user to evaluate given RNN for noise performance. The designer can use these results to constrain the design space so that the design satisfies performance specifications whenever possible. An example is provided using the measures derived in this paper to predetermine the best among several RNN designs for a given problem.  相似文献   
107.
Bovine rotavirus strain B223 is the North American prototype for group A P8[11] serotype/genotype rotaviruses. Rotaviruses with this serotype/genotype are a prevalent cause of neonatal calf diarrhea and have also been isolated from asymptomatic human infants. On the basis of deduced amino acid sequence of the outer capsid viral protein 4 (VP4), strain B223 lacks a cysteine at position 318 that is conserved among all other rotavirus strains. It has been speculated that this may result in the loss of disulfide bond and a change in the structure of the VP4 that may affect the infectivity and antigenicity of the virus. This paper describes partial sequences of the VP4 gene (nucleotides 613 to 1016 coding for amino acid positions 202 to 335) of 16 bovine rotavirus field isolates with P8[11] that were obtained from calves in Nebraska and Indiana. All the isolates lack a cystein at position 203 and had a conserved valine residue at position 318, thus indicating that the prototype strain B223 is representative of group A rotaviruses with P8[11] serotype/genotype.  相似文献   
108.
109.
110.
AIM: Assessment of the antihypertensive effect of doxazosin, alpha-1 blocker, as well as its action on lipid and carbohydrate metabolism, microcirculation and platelet function in patients with non-insulin-dependent diabetes mellitus (NIDDM). MATERIALS AND METHODS: Doxazosin (tonocardin) treatment was given for 11 weeks to 33 NIDDM patients with concomitant hypertension. The clinical examination comprised evaluation of central hemodynamics, vessels of the fundus of eye, lipid and carbohydrate metabolism, renal function, platelet aggregation. RESULTS: Tonocardin produced a fall in the systolic blood pressure (BP) by 14%, in the diastolic BP--by 17%. The 24-h profile of BP, lipid and purine metabolism, microcirculation of the vessels of the fundus of eye also improved. Total peripheral vascular resistance, left ventricular myocardial mass and platelet aggregation. Carbohydrate metabolism remained unchanged. CONCLUSION: Monotherapy with tonocardin (2-8 mg/day) is effective and safe in the treatment of arterial hypertension in NIDDM patients.  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