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   3605篇
  免费   58篇
  国内免费   14篇
电工技术   147篇
综合类   8篇
化学工业   652篇
金属工艺   187篇
机械仪表   64篇
建筑科学   49篇
矿业工程   5篇
能源动力   109篇
轻工业   167篇
水利工程   14篇
石油天然气   1篇
无线电   456篇
一般工业技术   596篇
冶金工业   865篇
原子能技术   93篇
自动化技术   264篇
  2023年   8篇
  2022年   24篇
  2021年   47篇
  2020年   18篇
  2019年   30篇
  2018年   31篇
  2017年   27篇
  2016年   32篇
  2015年   28篇
  2014年   57篇
  2013年   141篇
  2012年   101篇
  2011年   157篇
  2010年   120篇
  2009年   139篇
  2008年   149篇
  2007年   114篇
  2006年   98篇
  2005年   103篇
  2004年   105篇
  2003年   114篇
  2002年   109篇
  2001年   82篇
  2000年   65篇
  1999年   71篇
  1998年   350篇
  1997年   196篇
  1996年   177篇
  1995年   103篇
  1994年   98篇
  1993年   99篇
  1992年   54篇
  1991年   48篇
  1990年   41篇
  1989年   49篇
  1988年   55篇
  1987年   54篇
  1986年   30篇
  1985年   37篇
  1984年   29篇
  1983年   32篇
  1982年   36篇
  1981年   33篇
  1980年   41篇
  1979年   23篇
  1978年   19篇
  1977年   23篇
  1976年   38篇
  1975年   11篇
  1974年   8篇
排序方式: 共有3677条查询结果,搜索用时 31 毫秒
41.
Understanding the topographical relationships between phosphatidylserine (PS) and protein kinase C (PKC) within neurons can provide clues about the mechanism of translocation and activation of PKC. For this purpose we applied monoclonal antibodies (Abs) of PS and PKC to sections of developing rat cerebellum. The anti-PKC Ab immunohistochemical pattern showed homogeneous staining of Purkinje cells over various postnatal ages, whereas the anti-PS Ab staining showed a heterogeneous localization over these ages. Purkinje cells did not stain well between postnatal day 14 (PND 14) and PND 21, suggesting that the PS was lost from the membrane during preparation of the sections during this period. These data imply that interactions between PS and PKC vary in Purkinje cells during postnatal development.  相似文献   
42.
A 64-Mb dynamic RAM (DRAM) has been developed with a meshed power line (MPL) and a quasi-distributed sense-amplifier driver (qDSAD) scheme. It realizes high speed, tRAS=50 ns (typical) at Vcc=3.3 V, and 16-b input/output (I/O). This MPL+qDSAD scheme can reduce sensing delay caused by the metal layer resistance. Furthermore, to suppress crosstalk noise, a VSS shield peripheral layout scheme has been introduced, which also widens power line widths. This 64-Mb DRAM was fabricated with 0.4-μm CMOS technology using KrF excimer laser lithography. A newly developed memory cell structure, the tunnel-shaped stacked-capacitor cell (TSSC), was adapted to this 64-Mb DRAM  相似文献   
43.
The effects of leukotrienes C4 and D4 on ciliary activity of human paranasal sinus mucosa were investigated in vitro. Normal mucosa was surgically obtained from human paranasal sinuses and incubated in the form of tissue culture. Ciliated cells were magnified under an inverted microscope, and ciliary activity was photoelectrically measured. LTD4 progressively inhibited ciliary activity, and showed a more potent effect on ciliary activity compared to LTC4. The concentrations of LTC4 and LTD4 in the incubation medium were determined by radioimmunoassay when the mucosa was incubated with 10(-8) M LTC4. The concentration of LTD4 gradually increased and after 90 min reached the maximum of 0.71 x 10(-8) M, while that of LTC4 was reduced to about 10% of its initial concentration within 60 min. These results suggested the possible conversion of LTC4 to LTD4 on the mucosa, and that LTC4 can inhibit ciliary activity by means of LTD4.  相似文献   
44.
45.
The electrode characteristics of perovskite-type oxides, La0.6Sr0.4CoO3 and La0.6Sr0.4MnO3, on ceria-based oxide and stabilized zirconia were analysed by the a.c. impedance method. The ionic conductivities of the electrolyte and electrode conductivities from the a.c. impedance analysis agreed with those obtained from the current interruption and d.c. four-probe methods. Two semicircles from the charge transfer and diffusion processes appeared as the electrode resistance. The relative contribution of these two processes to the overall electrode resistance strongly depended on the microstructure of the electrode. The electrode microstructure could be controlled by the dispersion medium used for the electrode slurry. The La0.6Sr0.4MnO3 electrode coated with n-butyl acetate slurry exhibited the smallest electrode resistance.  相似文献   
46.
The use of an optical filter to reduce chirping influence in LD wavelength conversion is demonstrated. A part of broadened spectrum of wavelength-converted light is eliminated by a narrow-band optical filter, and sensitivity degradation due to frequency chirping is reduced as a result. In an experiment using a fiber Fabry-Perot filter, the sensitivity was improved by about 1.5 dB in 1.55-/spl mu/m transmissions with normal dispersion fibers when an LD converter was biased at two times the threshold current.  相似文献   
47.
In order to realize full-color electroluminescent (EL) displays, which are expected as a dominant candidate for the future multimedia flat panel display, blue EL devices with SrGa2S4:Ce have been prepared by molecular beam epitaxy (MBE). This paper proposes a novel deposition method employing Sr metal and Ga2S4 compound as the source materials. A single-phase SrGa2S4 layer is obtained in a Ga2S3/Sr flux ratio of 60 and at the growth temperature of 560°C. We have obtained the well-saturated blue with CIE color coordinates of x=0.14, y=0.14 and brighter blue EL devices made by optimizing the growth conditions in MBE. The maximum luminance of 70 cd/m2 in comparison with the 3 cd/m2 of our previous EL devices, is achieved at a driving frequency of 1 kHz  相似文献   
48.
49.
Athermal silica-based arrayed-waveguide grating multiplexer   总被引:4,自引:0,他引:4  
A temperature dependent channel wavelength shift in a silica-based arrayed-waveguide grating multiplexer is successfully suppressed from 0.95 to 0.05 nm in the 0-85°C temperature range, which means that it can be used in practical WDM systems without the need for temperature control  相似文献   
50.
Electric power systems are expanding in size and complexity, and the requirement for the energy management system (EMS) is becoming more important. In this computer control system, a single control computer is used mainly as the primary computer and its software is very complicated because of its hugh number of small, quick tasks to obtain high response speed. Therefore, much effort is needed to develop and modify the programs, and the responsiveness of this centralized architecture varies greatly when many faults occur in the power system. This paper describes a new distributed architecture for the EMS. Distributed processors execute the functions cooperatively with periodic access to the common bulletin board database in which information about the power system exist. This architecture facilitates the software development and maintenance, and it also enhances the performance by the parallel processing of the distributed functions.  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