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   2341篇
  免费   56篇
  国内免费   5篇
电工技术   163篇
综合类   2篇
化学工业   497篇
金属工艺   75篇
机械仪表   71篇
建筑科学   47篇
能源动力   102篇
轻工业   155篇
水利工程   3篇
石油天然气   2篇
无线电   298篇
一般工业技术   332篇
冶金工业   415篇
原子能技术   93篇
自动化技术   147篇
  2023年   7篇
  2022年   17篇
  2021年   25篇
  2020年   23篇
  2019年   25篇
  2018年   22篇
  2017年   36篇
  2016年   47篇
  2015年   30篇
  2014年   61篇
  2013年   128篇
  2012年   63篇
  2011年   93篇
  2010年   89篇
  2009年   80篇
  2008年   100篇
  2007年   82篇
  2006年   80篇
  2005年   68篇
  2004年   71篇
  2003年   92篇
  2002年   72篇
  2001年   60篇
  2000年   43篇
  1999年   68篇
  1998年   161篇
  1997年   96篇
  1996年   82篇
  1995年   56篇
  1994年   52篇
  1993年   47篇
  1992年   33篇
  1991年   28篇
  1990年   31篇
  1989年   25篇
  1988年   20篇
  1987年   25篇
  1986年   31篇
  1985年   29篇
  1984年   31篇
  1983年   22篇
  1982年   23篇
  1981年   21篇
  1980年   25篇
  1979年   12篇
  1978年   17篇
  1977年   10篇
  1976年   14篇
  1975年   8篇
  1972年   4篇
排序方式: 共有2402条查询结果,搜索用时 15 毫秒
1.
Over the past decades, the number of patients with dry eye disease (DED) has increased dramatically. The incidence of DED is higher in Asia than in Europe and North America, suggesting the involvement of cultural or racial factors in DED etiology. Although many definitions of DED have been used, discrepancies exist between the various definitions of dry eye disease (DED) used across the globe. This article presents a clinical consensus on the definition of DED, as formulated in four meetings with global DED experts. The proposed new definition is as follows: “Dry eye is a multifactorial disease characterized by a persistently unstable and/or deficient tear film (TF) causing discomfort and/or visual impairment, accompanied by variable degrees of ocular surface epitheliopathy, inflammation and neurosensory abnormalities.” The key criteria for the diagnosis of DED are unstable TF, inflammation, ocular discomfort and visual impairment. This definition also recommends the assessment of ocular surface epitheliopathy and neurosensory abnormalities in each patient with suspected DED. It is easily applicable in clinical practice and should help practitioners diagnose DED consistently. This consensus definition of DED should also help to guide research and clinical trials that, to date, have been hampered by the lack of an established surrogate endpoint.  相似文献   
2.
3.
Polyvinylalcohol (PVA) polymer gel is a temperature sensitive polymeric gel, with a critical transition temperature (with H2O) of 310 K. At higher than 310 K, this temperature sensitive polymer gel shrinks because of discharging water, whereas at lower temperatures, the gel swelled because of absorbing water. The reversibility of the gel's volume change was confirmed by temperature swing. The adsorption behavior of an organic compound onto the PVA polymer gel in water was tested at various temperatures. The amount of adsorbed organic compound increased remarkably at temperatures higher than about 310 K. Then, it was confirmed that the organic compound in PVA polymer gel could be reversibly adsorbed and desorbed by a temperature change between 293 and 323 K. The mechanism of adsorption of the organic compound onto the PVA polymer gel could be explained by hydration and dehydration of polymer gel.  相似文献   
4.
We derive a linear correspondence between the variables of an encoder and those of a corresponding syndrome former. Using the derived correspondence, we show that the log-likelihood ratio of an information bit conditioned on a received sequence can be equally calculated using the syndrome trellis. It is shown that the proposed method also applies to recursive systematic convolutional codes which are typical constituent codes for turbo codes. Moreover, we show that soft-in syndrome decoding considering a priori probabilities of information bits is possible in the same way as for Viterbi decoding based on the code trellis. Hence, the proposed method can be applied to iterative decoding such as turbo decoding. We also show that the proposed method is effective for high-rate codes by making use of trellis modification.  相似文献   
5.
6.
We fabricated a 1-GHz-spaced 16-channel arrayed-waveguide grating (AWG) by using a new AWG configuration where the path of each arrayed waveguide winds backward and forward across a 4-in diameter wafer without crossing any other waveguides. The ultra-narrow (< 1 GHz) and stable transmission bands of this AWG can be used to construct a wavelength reference standard covering the S, C, and L bands in the dense wavelength-division-multiplexing network systems whose frequency deviation is /spl plusmn/160 MHz.  相似文献   
7.
We describe a low-loss athermal silica-based interleave filter with a lattice-form structure. We athermalize the filter by using a silicone-filled groove formed in each delay line and we employ a low-loss design to reduce the accumulated groove excess loss in the multiple delay lines. By using these designs, we obtained a very low groove excess loss of 0.4 dB and achieved satisfactory temperature insensitivity and optical characteristics with this filter.  相似文献   
8.
A silica-based 1.5%-/spl Delta/ 100 GHz-spacing 32-channel athermal arrayed-waveguide grating (AWG) with compact size and extremely low insertion loss is described. By reducing the fibre coupling loss and the excess loss in a silicone-filled groove, an insertion loss of 1.3 dB was achieved with this athermal AWG.  相似文献   
9.
Living organisms including humans drive circadian rhythm, and this rhythm influences the social structure and daily life of human beings. The suprachiasmatic nucleus (SCN) has been established as a pacemaker for mammalian circadian rhythm. There are many kinds of neurotransmitters and neuromodulators in this nucleus. The circadian systems are involved in oscillation, input (entrainment) and output (overt rhythm). Therefore in this review, pharmacological characteristics of circadian systems in relation to the SCN are discussed by focussing especially upon the roles of various neurotransmitters and modulators.  相似文献   
10.
In this paper, we study the existence of cycles of all lengths in the recursive circulant graphs, and we show a necessary and sufficient condition for the graph being pancyclic and bipancyclic.  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