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   847925篇
  免费   28656篇
  国内免费   11825篇
电工技术   25706篇
技术理论   31篇
综合类   17827篇
化学工业   138446篇
金属工艺   39887篇
机械仪表   36821篇
建筑科学   35043篇
矿业工程   13725篇
能源动力   22287篇
轻工业   62192篇
水利工程   11650篇
石油天然气   34900篇
武器工业   2273篇
无线电   90772篇
一般工业技术   149316篇
冶金工业   110015篇
原子能技术   17506篇
自动化技术   80009篇
  2023年   5256篇
  2022年   10358篇
  2021年   16544篇
  2020年   12210篇
  2019年   12227篇
  2018年   17084篇
  2017年   18369篇
  2016年   17608篇
  2015年   17023篇
  2014年   23801篇
  2013年   42284篇
  2012年   33325篇
  2011年   40278篇
  2010年   33569篇
  2009年   34546篇
  2008年   34320篇
  2007年   33665篇
  2006年   32089篇
  2005年   28737篇
  2004年   22936篇
  2003年   21475篇
  2002年   20448篇
  2001年   19250篇
  2000年   19333篇
  1999年   20382篇
  1998年   34309篇
  1997年   25736篇
  1996年   20968篇
  1995年   16418篇
  1994年   14521篇
  1993年   13172篇
  1992年   10418篇
  1991年   9651篇
  1990年   9120篇
  1989年   8653篇
  1988年   8206篇
  1987年   7226篇
  1986年   6886篇
  1985年   7619篇
  1984年   6858篇
  1983年   6537篇
  1982年   5900篇
  1981年   5978篇
  1980年   5697篇
  1979年   5757篇
  1978年   5665篇
  1977年   6178篇
  1976年   7685篇
  1975年   5108篇
  1973年   4980篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
Grachev  A. I. 《Semiconductors》2022,56(2):67-70
Semiconductors - In this work, we discuss for the first time the principle of rotation in the constant electric field of a conducting particle with participation of the Lorentz force, which ensures...  相似文献   
4.
Koroteev  A. S. 《Atomic Energy》2021,130(4):202-208
Atomic Energy - The history and direction of further development of space nuclear energetics are examined. The functional diagram and principle of operation of a promising, powerful,...  相似文献   
5.
6.
Journal of Computer and Systems Sciences International - It is shown that the Lyapunov theorem on the distribution properties of the sum of random variables with different distribution densities...  相似文献   
7.
8.
The effects of cellulose microfibres (CMFs, Average size: 100 ± 5 μm) and cellulose nanofibres (CNFs, Average size: 60 ± 3 nm) on the properties of myofibrillar protein (MP) gels from duck breast meat were studied. The results demonstrated that CMFs and CNFs were mostly connected to MP by non-covalent bonds, the diffusion and cross-linking of MP molecules was promoted, and a denser and more complete gel network was formed. With the increases of CMFs and CNFs concentration (0–10%), the hardness was increased by 13.15% and 19.78% for CMFs10% and CNFs10% gels, respectively, and the elasticity was increased by 40% and 80%, respectively. At the same concentration (0–10%), the increase in gel hardness, viscoelasticity and immobilised water content was greater in the CNFs-MP group than in the CMFs-MP group. The CNFs-MP group had a tighter gel network, and CNFs had a better potential to improve the gelation performance of MP.  相似文献   
9.
Ripe carambolas are hard to store and transport, while freeze-dried ones are easy to store. However, its long production time leads to higher costs. This study shows that high hydrostatic pressure (HHP) treatment could shorten the freeze-drying time of carambola slices. After HHP treatment (25–250 MPa), the drying time of the fresh sample can be shortened by 33.3–44.4% and the distribution of water and pigment in tissues is much uniform. With the increment of the pressure, 2,2-diphenyl-1-picrylhydrazyl (DPPH) and hydroxyl radical scavenging rate are increased. At 250 MPa, the total phenolic content (TPC) increased from 11.34 to 13.36 mg GAE g−1, and the total flavonoid content (TFC) of the control sample was increased from 10.77 to 12.73 mg RE g−1. Compared with the untreated sample, HHP treatment can enhance the flavour and shorten the freeze-drying time. This work guides the application of HHP technology for drying food processing.  相似文献   
10.
The article investigates the finite-time adaptive fuzzy control for a class of nonlinear systems with output constraint and input dead-zone. First, by skillfully combining the barrier Lyapunov function, backstepping design method, and finite-time control theory, a novel adaptive state-feedback tracking controller is constructed, and the output constraint of the nonlinear system is not violated. Second, the fuzzy logic system is used to approximate unknown function in the nonlinear system. Third, the finite-time command filter is introduced to avoid the problem of “complexity explosion” caused by repeated differentiations of the virtual control signal in conventional backstepping control schemes. Meanwhile, a new saturation function is added in the compensating signal for filter error to improve control accuracy. Finally, based on Lyapunov stability analysis, all the signals of the closed-loop are proved to be semi-globally uniformly ultimately bounded, and the tracking error converges to a small neighborhood region of the origin in a finite time. A simulation example is presented to demonstrate the effectiveness for the proposed control scheme.  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