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   16327篇
  免费   106篇
  国内免费   493篇
电工技术   241篇
综合类   77篇
化学工业   1744篇
金属工艺   593篇
机械仪表   895篇
建筑科学   968篇
矿业工程   319篇
能源动力   100篇
轻工业   3295篇
水利工程   319篇
石油天然气   301篇
武器工业   69篇
无线电   843篇
一般工业技术   5888篇
冶金工业   324篇
原子能技术   165篇
自动化技术   785篇
  2022年   28篇
  2021年   42篇
  2018年   19篇
  2016年   28篇
  2015年   44篇
  2014年   55篇
  2013年   76篇
  2012年   1752篇
  2011年   2293篇
  2010年   481篇
  2009年   234篇
  2008年   1461篇
  2007年   1384篇
  2006年   1131篇
  2005年   1005篇
  2004年   868篇
  2003年   687篇
  2002年   660篇
  2001年   523篇
  2000年   556篇
  1999年   368篇
  1998年   208篇
  1997年   182篇
  1996年   163篇
  1995年   139篇
  1994年   158篇
  1993年   125篇
  1992年   121篇
  1991年   152篇
  1990年   150篇
  1989年   153篇
  1988年   124篇
  1987年   142篇
  1986年   115篇
  1985年   153篇
  1984年   149篇
  1983年   154篇
  1982年   137篇
  1981年   105篇
  1980年   97篇
  1979年   98篇
  1978年   52篇
  1977年   24篇
  1976年   33篇
  1975年   33篇
  1974年   25篇
  1973年   18篇
  1965年   25篇
  1964年   25篇
  1958年   20篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
医学上的很多疾病都是我们无意识地进入脱水状态所致,因为身体最终会把缺水这一局面,通过某种奇特而确凿的方式显示出来。例如我们已谈过的胃灼热、胃痛等。以下疼痛也与缺水有关。  相似文献   
82.
关节脱水的后果如果关节脱水,软骨细胞就会处于强烈的摩擦状态,从而使它们迅速死亡,而死亡的细胞需要得到替换。软骨使用过度,并且处在修复状态,它就可能受到损伤,这一区域的感应器就会发出强烈的信号,表达它们急需修理的愿望。  相似文献   
83.
Multicamera people tracking with a probabilistic occupancy map   总被引:1,自引:0,他引:1  
Given two to four synchronized video streams taken at eye level and from different angles, we show that we can effectively combine a generative model with dynamic programming to accurately follow up to six individuals across thousands of frames in spite of significant occlusions and lighting changes. In addition, we also derive metrically accurate trajectories for each one of them.Our contribution is twofold. First, we demonstrate that our generative model can effectively handle occlusions in each time frame independently, even when the only data available comes from the output of a simple background subtraction algorithm and when the number of individuals is unknown a priori. Second, we show that multi-person tracking can be reliably achieved by processing individual trajectories separately over long sequences, provided that a reasonable heuristic is used to rank these individuals and avoid confusing them with one another.  相似文献   
84.
85.
Human 14-3-3 proteins have isoform-specific expression and functions in different kinds of normal or tumor cells and tissues. However, the expression profiling of 14-3-3 proteins and isoform-specific biological functions are unclear in human glioma so far. In our study, the expression levels and characterization of 14-3-3 isoforms in human glioma tissues were investigated by a sensitive, accurate stable isotope labeling with amino acids in cell culture-based quantitative proteomic strategy. As a result, except unexpressed 14-3-3σ, the other six isoforms, with different expression levels, were existed in glioma tissues and para-cancerous brain tissues (PBTs). 14-3-3β and η were upregulated, whereas 14-3-3ζ was downregulated in glioma tissues compared with that in PBTs. And the other three isoforms 14-3-3ε, θ, and γ had similar expression levels in human glioma tissues and PBTs. Western blot and immunohistochemistry analysis were both consistent with the quantitative proteomic data. The loss of expression of 14-3-3σ was further discovered due to DNA high methylation in its coding region in glioma by methylation-specific PCR analysis. These results indicated that the four isoforms, including 14-3-3β, η, ζ, and σ, may play important roles in tumorigenesis of human glioma, which is probably used as potential biomarkers for diagnosis and targets for treatment of human gliomas in future.  相似文献   
86.
Multiple sclerosis is characterized by inflammatory demyelination and axonal loss as pathophysiological correlates of relapsing activity and progressive development of clinical disability. The molecular processes involved in this pathogenesis are still unclear as they are quite complex and heterogeneous. In this article we present protein expression analysis of brain and spinal cord tissues from different models of murine experimental autoimmune encephalomyelitis (EAE), the most commonly used animal model for multiple sclerosis. We observed a number of EAE-specific protein expression and PTM differences. Proteome analysis was extended to multiple sclerosis specimens in order to validate the EAE findings. Our findings suggest the regulation of a number of proteins that shed light on the molecular mechanisms of the disease processes taking place in EAE and multiple sclerosis. We found consistent modulation of proteins including serum amyloid P component, sirtuin 2, dihydropyrimidinase-related protein family proteins, stathmin 1, creatine kinase B and chloride intracellular channel protein 1. Functional classification of the proteins by database and the literature mining reveals their association with neuronal development and myelinogenesis, suggesting possible disease processes that mediate neurodegeneration.  相似文献   
87.
88.
We have produced a multilayer transmission filter with 100 periods of Cr/C to achieve a significant phase retardation while maintaining good transmission for photon energies just below the carbon K edge. This device was installed into a polarimeter behind the SX700/3 monochromator at the Berlin synchrotron radiation laboratory, BESSY. The phase-retardation properties were observed as theoretically predicted. Agreement between experiment and calculation could be obtained by introduction of a rather small interface roughness in the simulation code (σ = 0.65 nm rms). An observed phase retardation of 5° was sufficient to permit, for the first time we believe, a complete and unambiguous polarization analysis of soft-x-ray synchrotron radiation (265-eV photon energy) with primary standards.  相似文献   
89.
Admittance diagrams are used to analyze qualitatively and quantitatively the behavior of inhomogeneous thin films with an arbitrary refractive-index function. From this study it follows that one can treat the behavior of rugate filters by using the concept of effective refractive indices, which are associated with the phase integral in a simple way. These results are applied to the study of periodic systems, and, as expected, one can consider high and low effective refractive indices to determine the important parameters of these stop bands. With these ideas it is possible that one can deal with rugate filters more closely as homogeneous periodic systems by taking advantage of the existing theory.  相似文献   
90.
This reply is to the comment by C. G. Ribbing [Appl. Opt. 33, 8055 (1994)] on our paper on IR optical constants of polycrystalline boron nitride.  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