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   5168篇
  免费   193篇
  国内免费   13篇
电工技术   82篇
综合类   30篇
化学工业   1504篇
金属工艺   96篇
机械仪表   94篇
建筑科学   329篇
矿业工程   23篇
能源动力   99篇
轻工业   413篇
水利工程   34篇
石油天然气   2篇
无线电   317篇
一般工业技术   1091篇
冶金工业   473篇
原子能技术   40篇
自动化技术   747篇
  2023年   38篇
  2022年   49篇
  2021年   85篇
  2020年   74篇
  2019年   68篇
  2018年   83篇
  2017年   98篇
  2016年   142篇
  2015年   102篇
  2014年   163篇
  2013年   248篇
  2012年   221篇
  2011年   322篇
  2010年   245篇
  2009年   255篇
  2008年   248篇
  2007年   236篇
  2006年   237篇
  2005年   202篇
  2004年   174篇
  2003年   137篇
  2002年   112篇
  2001年   87篇
  2000年   90篇
  1999年   101篇
  1998年   112篇
  1997年   83篇
  1996年   91篇
  1995年   69篇
  1994年   71篇
  1993年   75篇
  1992年   74篇
  1991年   57篇
  1990年   59篇
  1989年   56篇
  1988年   60篇
  1987年   55篇
  1986年   46篇
  1985年   45篇
  1984年   54篇
  1983年   38篇
  1982年   47篇
  1981年   47篇
  1980年   31篇
  1979年   29篇
  1978年   34篇
  1977年   31篇
  1976年   33篇
  1975年   37篇
  1973年   31篇
排序方式: 共有5374条查询结果,搜索用时 0 毫秒
61.
Research on semiconductor photocatalysts for the conversion of solar energy into chemical fuels has been at the forefront of renewable energy technologies. Water splitting to produce H2 and CO2 reduction to hydrocarbons are the two prominent approaches. A lesser‐known process, the conversion of solar energy into the versatile high‐energy product H2O2 via reduction of O2 has been proposed as an alternative concept. Semiconductor photoelectrodes for the direct photosynthesis of H2O2 from O2 have not been applied up to now. Photoelectrocatalytic oxygen reduction to peroxides in aqueous electrolytes by hydrogen‐bonded organic semiconductor is observed photoelectrodes. These materials have been found to be remarkably stable operating in a photoelectrochemical cell converting light into H2O2 under constant illumination for at least several days, functioning in a pH range from 1 to 12. This is the first report of a semiconductor photoelectrode for H2O2 production, with catalytic performance exceeding prior reports on photocatalysts by one to two orders of magnitude in terms of peroxide yield/catalyst amount/time. The combination of a strongly reducing conduction band energy level with stability in aqueous electrolytes opens new avenues for this widely available materials class in the field of photo(electro) catalysis.  相似文献   
62.
We demonstrated top-gate organic field effect transistors (OFETs) made with free radical photo-cured polymer gate dielectrics and poly(3-hexylthiophene). We introduced a new approach of cross linking dielectric polymers in OFETs by using acrylate monomers cured with UV irradiation directly on the semiconductor. Three different blends were formulated: one self-initiating acrylate oligomer and two epoxy acrylate monomers mixed with 4-phenylbenzophenone as photo initiator and N-methyldiethanolamine as amine synergist. Thin films of these blends were cured in air within one minute. The curing process was monitored with FT-IR spectroscopy and the effect of a wetting agent was studied by measuring the CV characteristics of metal–insulator-semiconductor (MIS) structures made with these formulations. OFETs made with the demonstrated formulations showed high on/off ratios (105–106) and low sub-threshold slopes (0.44–1.42 V/dec).  相似文献   
63.
64.
65.
The selective removal of one ligand in mixed-ligand MOFs upon thermolysis provides a powerful strategy to introduce additional mesopores without affecting the overall MOF structure. By varying the initial ligand ratio, MOFs of the MIL-125-Ti family with two distinct hierarchical pore architectures are synthesized, resembling either large cavities or branching fractures. The performance of the resulting hierarchically porous MOFs is evaluated toward the adsorptive removal of glyphosate (N-(phosphonomethyl)glycine) from water, and the adsorption kinetics and mechanism are examined. Due to their strong affinity for phosphoric groups, the numerous Ti–OH groups resulting from the selective ligand removal act as natural anchor points for effective glyphosate uptake. The relationships between contact duration, glyphosate concentration, and adsorbent dosage are investigated, and the impact of these parameters on the effectiveness of glyphosate removal from contaminated water samples is examined. The introduction of additional mesopores has increased the adsorption capacities by nearly 3 times with record values exceeding 440.9 mg g−1, which ranks these MOFs among the best-reported adsorbents.  相似文献   
66.
Using full 3D TCAD, an evaluation of process parameter space of bulk FinFET is presented from the point of view of DRAM, SRAM and I/O applications. Process and device simulations are performed with varying uniform fin doping, anti-punch implant dose and energy, fin width, fin height and gate oxide thickness. Bulk FinFET architecture with anti-punch implant is introduced beneath the channel region to reduce the punch-through and junction leakage. For 30 nm bulk FinFET, anti-punch implant with low energy of 15 to 25 keV and dose of 5.0 × 1013 to 1.0 × 1014 cm−2 is beneficial to effectively suppress the punch-through leakage with reduced GIDL and short channel effects. Our simulations show that bulk FinFETs are approximately independent of back bias effect. With identical fin geometry, bulk FinFETs with anti-punch implant show same ION-IOFF behavior and approximately equal short channel effects like SOI FinFETs.  相似文献   
67.
Diodes and diode strings in 90 nm and beyond technologies are investigated by measurement and device simulation. After a thorough calibration, the device simulator is utilised to achieve a better understanding and an enhanced device performance of diode strings under static and transient ESD conditions. Thereto, parasitic transistors and a so far neglected parasitic thyristor (SCR) in the diode string are regarded, exploited and optimised.  相似文献   
68.
The degree of charge transfer in thin films of organic charge transfer (CT)-complexes, which are deposited via thermal evaporation, is examined via infrared-spectroscopy. We demonstrate a linear relationship between the shift in the excitation energy of the CN-stretching mode of CT-complexes with the acceptor 7,7,8,8-tetracyanoquinodimethane (TCNQ) and the charge transfer. The measured correlation corresponds very well with DFT calculations. For Na-TCNQ we observe a splitting in the peak of the CN-stretching mode, which can be explained by the coupling of two modes and was confirmed by the calculations. In CT-complexes with partial charge transfer the appearance of an electronic excitation is demonstrated.  相似文献   
69.
王富裕 《电声技术》2009,33(12):20-24
6.2号筒压缩式驱动器(单元) 这是一个用酚醛树脂含浸的织物为振膜的号筒压缩式单元,音圈直径51nm,卷线高度4.6mm,气隙厚4mm。连接的号筒和相位塞被移走,后腔体积仔细地密封好以避免任何额外的声学共振。  相似文献   
70.
This paper reports fiber Bragg gratings (FBGs) inscribed in a small-core Ge-doped photonic crystal fibers with a UV laser and a Talbot interferometer. The responses of such FBGs to temper- ature, strain, bending, and transverse-loading were systematically investigated. The Bragg wavelength of the FBGs shifts toward longer wavelengths with increasing temperature, tensile strain, and transverse-loading. The bending and transverse- loading properties of the FBGs are sensitive to the fiber orientations.  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