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   1487篇
  免费   29篇
  国内免费   4篇
电工技术   127篇
化学工业   390篇
金属工艺   28篇
机械仪表   36篇
建筑科学   28篇
矿业工程   1篇
能源动力   60篇
轻工业   95篇
水利工程   1篇
石油天然气   1篇
无线电   114篇
一般工业技术   355篇
冶金工业   89篇
原子能技术   43篇
自动化技术   152篇
  2022年   20篇
  2021年   25篇
  2020年   7篇
  2019年   10篇
  2018年   8篇
  2017年   18篇
  2016年   26篇
  2015年   16篇
  2014年   36篇
  2013年   69篇
  2012年   52篇
  2011年   90篇
  2010年   49篇
  2009年   53篇
  2008年   82篇
  2007年   73篇
  2006年   63篇
  2005年   58篇
  2004年   50篇
  2003年   58篇
  2002年   53篇
  2001年   37篇
  2000年   29篇
  1999年   38篇
  1998年   61篇
  1997年   39篇
  1996年   35篇
  1995年   28篇
  1994年   23篇
  1993年   31篇
  1992年   22篇
  1991年   29篇
  1990年   19篇
  1989年   20篇
  1988年   26篇
  1987年   12篇
  1986年   18篇
  1985年   17篇
  1984年   21篇
  1983年   9篇
  1982年   10篇
  1981年   9篇
  1980年   11篇
  1979年   17篇
  1978年   12篇
  1976年   7篇
  1975年   3篇
  1974年   4篇
  1973年   4篇
  1968年   3篇
排序方式: 共有1520条查询结果,搜索用时 15 毫秒
1.
In a plant consisting of parallelized microreactors (MRs), the product quality is lowered because of a lack of flow uniformity among them when blockage occurs. It is not practical to install sensors in every MR from the viewpoint of cost when detecting the blocked MRs. In the previous study, the multiple blockage detection (MBD) method using a small number of sensors was proposed, but its performance became low when the number of sensors decreased. Here, the conventional algorithm for MBD is improved by considering the process behavior on blockage occurrence, and the effectiveness of the improved algorithm is demonstrated through a numerical case study. The effects of flow distributor types and sensor types on the MBD performance are numerically investigated.  相似文献   
2.
Immunosenescence is characterized by age-associated changes in immunological functions. Although age- and autoimmune-related sialadenitis cause dry mouth (xerostomia), the roles of immunosenescence and cellular senescence in the pathogenesis of sialadenitis remain unknown. We demonstrated that acquired immune cells rather than innate immune cells infiltrated the salivary glands (SG) of aged mice. An analysis of isolated epithelial cells from SG revealed that the expression levels of the chemokine CXCL13 were elevated in aged mice. Senescence-associated T cells (SA-Ts), which secrete large amounts of atypical pro-inflammatory cytokines, are involved in the pathogenesis of metabolic disorders and autoimmune diseases. The present results showed that SA-Ts and B cells, which express the CXCL13 receptor CXCR5, accumulated in the SG of aged mice, particularly females. CD4+ T cells derived from aged mice exhibited stronger in vitro migratory activity toward CXCL13 than those from young mice. In a mouse model of Sjögren’s syndrome (SS), SA-Ts also accumulated in SG, presumably via CXCL12-CXCR4 signaling. Collectively, the present results indicate that SA-Ts accumulate in SG, contribute to the pathogenesis of age- and SS-related sialadenitis by up-regulating chemokines in epithelial cells, and have potential as therapeutic targets for the treatment of xerostomia caused by these types of sialadenitis.  相似文献   
3.
4.
On an earthspace propagation path with the low elevation angle of 10 deg, the phase between co- and crosspolar signals occasionally showed rapid and irregular fluctuations during fine weather. These fluctuations were generally significant during the daytime, and were strongly in phase with the occurrence of the copolar amplitude scintillations. This could be attributed to the combined effects of the crosspolar phase pattern of the receiving antenna and small fluctuations of the angle of arrival of the radiowaves.  相似文献   
5.
6.
A compound denoted as (Ce0.75Zr0.25)O2 (Ce, ZrO8) is formed near room temperature from cerium and zirconium nitrates using hydrazine monohydrate. It has a cubic unit cell with a = 0.5342 nm. Characterization of powders heated to various temperatures at 10°C/min demonstrates that the specific surface area does not decrease below 20 mVg until >1000°C.  相似文献   
7.
Cold-rolling texture and partially recrystallized texture of polycrystalline 3 pct Si-Fe were investigated using high-resolution electron backscattered diffraction (EBSD) method. From the measurement on a deformed grain with {211}〈011〉∼{111}〈011〉 orientations, deformation bands with {12 4 1}〈014〉 orientation were found. It turned out that the orientation rotation relationship between deformation bands and surrounding deformed grain can be explained by the activation of the slip system, which has a common slip plane with an adjacent grain. Oriented nucleation of recrystallized grains with {12 4 1}〈014〉 orientation was observed in a deformed grain with {211}〈011〉∼{111}〈011〉 orientation. Exactly the same orientation relationship that was observed between deformed grain and the deformation bands was also observed between the deformed grain and the recrystallized grain. A hypothesis that recrystallization nuclei are generated directly from the deformation bands formed by an activation of the slip system that has a common slip plane of neighboring deformed grains was proposed from the present experimental results.  相似文献   
8.
A high-speed bilevel reproduction algorithm, called modified error diffusion (MED) algorithm, has been developed to provide high-quality halftoning images for continuous tone images and has been implemented in a CMOS LSI chip. The chip has been designed with standard-cell 1.5-μm CMOS technology using an optimum layout design. The chip has achieved a maximum processing speed of 60 ns/pixel  相似文献   
9.
An average shell volume occupied in the adsorption layer on alumina by a polyacrylic acid ammonium salts molecule (PAA) defined as the average area occupied by an adsorbed PAA on alumina multiplied by the average thickness of the water layer at the limit of thickening, has been calculated from the adsorbed amount of PAA and from the flow points of alumina in the presence of PAA of different molecular weights. A steric effect of the PAA dispersant on the dispersion of alumina resulted in a flow with no yield stress. This was due to the change of the extension of PAA in the adsorption shell from a sphere to an ellipsoid with a long axis which exceeded the effective distance that the van der Waals attraction force reaches at a molecular weight for the PAA of between 10 000–20 000.  相似文献   
10.
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