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   4613篇
  免费   150篇
  国内免费   9篇
电工技术   73篇
综合类   2篇
化学工业   904篇
金属工艺   84篇
机械仪表   72篇
建筑科学   170篇
矿业工程   25篇
能源动力   112篇
轻工业   395篇
水利工程   37篇
石油天然气   4篇
无线电   478篇
一般工业技术   731篇
冶金工业   1139篇
原子能技术   72篇
自动化技术   474篇
  2023年   34篇
  2022年   38篇
  2021年   53篇
  2020年   48篇
  2019年   61篇
  2018年   68篇
  2017年   62篇
  2016年   85篇
  2015年   79篇
  2014年   82篇
  2013年   200篇
  2012年   141篇
  2011年   204篇
  2010年   136篇
  2009年   167篇
  2008年   191篇
  2007年   142篇
  2006年   126篇
  2005年   102篇
  2004年   91篇
  2003年   117篇
  2002年   106篇
  2001年   99篇
  2000年   90篇
  1999年   98篇
  1998年   281篇
  1997年   195篇
  1996年   139篇
  1995年   109篇
  1994年   106篇
  1993年   94篇
  1992年   64篇
  1991年   83篇
  1990年   54篇
  1989年   57篇
  1988年   60篇
  1987年   55篇
  1986年   42篇
  1985年   65篇
  1984年   58篇
  1983年   44篇
  1982年   38篇
  1981年   39篇
  1980年   32篇
  1979年   33篇
  1978年   37篇
  1977年   39篇
  1976年   66篇
  1975年   38篇
  1974年   42篇
排序方式: 共有4772条查询结果,搜索用时 0 毫秒
31.
Carbon based multilayer systems for highly loaded forming tools Amorphous hydrogenated carbon (metal‐free a‐C:H and metal‐containing a‐C:H:Me) films respond very sensitively to local overloads. For example during forming tool operations, hard abrasive particles and locally high stresses on the coating surface can cause crack initiation and early coating failure. Compared to the high hardness, wear resistance and excellent friction properties, in many cases the adhesion of a‐C:H films is relatively insufficient. Adhesion and overload resistance of a‐C:H and a‐C:H:Me, prepared by reactive sputtering, can be influenced in a wide range by different interlayer systems. In the present report the wear mechanism of amorphous carbon coatings and the influence of different metallic, metal nitride and metal carbide interlayers on the growth structure, the adhesion and the load resistance will be reported. Two well adapted multi‐coating systems, successfully tested for highly loaded tools and components, will be presented.  相似文献   
32.
We describe the design and operation of a new high-pressure metal ebulliometer which can operate at pressures to at least 3 MPa in the range 220–400 K. Infinite-dilution activity coefficients are presented for the system CHF2Cl + CF3-CH, at 275 K and for the system CF3-CH2F + CH2F2, at 260, 230, and 300 K. The Wilson activity coellicient model and a virial coefficient model are applied to these systems, and the phase equilibrium conditions are calculated. The results are shown to agree well with predicted and with published measured values. The excess enthalpy is calculated and compared with results from a Peng Robinson equation of state. Vapor densities on the dew curves are given.  相似文献   
33.
The safe immobilization of nuclear waste in geological repositories is one of the major scientific challenges facing humanity today. Crystalline ceramics hold the promise of locking up actinides from nuclear fuel and excess weapons plutonium in their structure thereby isolating them from the environment. This paper presents the atomistic details of radiation damage in a model ceramic, zircon.  相似文献   
34.
Mechanically shaped preforms (MSP) have been demonstrated to combine economic non-CVD (chemical vapor deposition) processing and low loss, with a published value of 0.63 dB/km and a size of 30 fkm/preform. Improved processing is proposed which results in a minimum loss of 0.27 dB/km at 1550 nm. Preforms capable of yielding 150 fkm have been produced. Reboiling during preform stretching and fiber pulling is identified as the last remaining problem of the process  相似文献   
35.
36.
A method for the determination of 5-methoxypsoralene in suntan-cosmetics is described. After liquid chromatographic clean-up, the final extract is screened by twodimensional thin layer chromatography. For positive extracts 5-methoxypsoralene is analysed quantitatively by capillary gas chromatography, using 5-alpha-cholestane as an internal standard and flame ionization detection (FID). The results were confirmed by gas chromatography-mass spectrometry (GC-MS). The recoveries for suntan-cosmetics of emulsion type were 70% and for tanning oils 90%. Detection limits of the method were 0,1 to 0,5 mg/kg, depending on the sample type. By application of this method 5-methoxypsoralene was detected in 6 of the 21 cosmetic products at levels up to 28 mg/kg.  相似文献   
37.
Semiconductor laser amplifier as optical switching gate   总被引:3,自引:0,他引:3  
The properties of a semiconductor laser amplifier as optical switching gate are investigated. Particular attention is paid to gain, contrast ratio, and switching time of the device. These properties are studied experimentally and theoretically with respect to the injection current, optical input power, and cavity resonances. The experimental arrangements and the theoretical method are described. As an example of the various applications of semiconductor laser amplifier gates, packet switching experiments with self-routing, employing cascaded switching gates, are reported. In a theoretical analysis the restrictions that the properties of semiconductor laser amplifier gates impose on a larger switching system consisting of many such gates are investigated  相似文献   
38.
The MPC105 peripheral component interconnection bridge/memory controller provides a platform-specification-compliant bridge between Power PC microprocessors and the PCI bus. With it, designers can create systems using peripherals already designed for a variety of standard PC interfaces. This bridge chip also integrates a secondary cache controller and high-performance memory controller that supports DRAM or synchronous DRAM and ROM or flash ROM  相似文献   
39.
Fibre-reinforced plastics (FRPs) are candidate materials for the insulation of superconducting magnet coils in future fusion reactors. This paper reports on a test programme performed to assess the mechanical properties of these materials and to obtain information on the damage and fracture mechanisms. Different types of FRPs (epoxies and poly- and bismaleimides as resins; two- and three-dimensional E-, S- or T-glass fabrics as reinforcements) were irradiated at room temperature by 2 MeV electrons and 60Co-gamma rays up to 1.8 × 108 Gy and by different reactor spectra up to a neutron fluence of 1 × 1023 m−2 (E > 0.1 MeV) at room temperature, 80 K or 5 K. Mechanical tests in tension as well as in the intralaminar crack opening and shear mode were carried out on the irradiated samples at 77 K. After low temperature irradiation, half of the samples were subjected to a warm-up cycle to room temperature before testing at 77 K. Results on the influence of different radiation sources and annealing cycles on the mechanical properties of these materials will be discussed.  相似文献   
40.
Paul  G Weber  J 《特殊钢》1998,19(1):24-28
德国巴登钢铁公司(BSW)炼钢厂有2座80t电炉,2座钢包炉和2台5流连铸机,由于BSW的生产和管理人员具有高的素质,精心保养设备,保持高生产率,从而降低生产成本。去年BSW炼钢厂生产140多万t质量合格钢坯。全员劳动生产率超过2000t钢/人·年。  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