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   924篇
  免费   10篇
电工技术   26篇
化学工业   252篇
金属工艺   16篇
机械仪表   25篇
建筑科学   6篇
能源动力   39篇
轻工业   36篇
无线电   97篇
一般工业技术   163篇
冶金工业   227篇
原子能技术   20篇
自动化技术   27篇
  2022年   5篇
  2021年   14篇
  2020年   6篇
  2019年   4篇
  2018年   6篇
  2017年   6篇
  2015年   8篇
  2014年   16篇
  2013年   32篇
  2012年   19篇
  2011年   31篇
  2010年   29篇
  2009年   31篇
  2008年   16篇
  2007年   27篇
  2006年   29篇
  2005年   24篇
  2004年   29篇
  2003年   33篇
  2002年   24篇
  2001年   20篇
  2000年   20篇
  1999年   33篇
  1998年   86篇
  1997年   67篇
  1996年   52篇
  1995年   22篇
  1994年   26篇
  1993年   27篇
  1992年   14篇
  1991年   13篇
  1990年   18篇
  1989年   14篇
  1988年   5篇
  1987年   5篇
  1986年   6篇
  1985年   7篇
  1984年   9篇
  1983年   6篇
  1982年   7篇
  1981年   9篇
  1980年   5篇
  1979年   7篇
  1978年   10篇
  1977年   6篇
  1976年   10篇
  1975年   4篇
  1974年   5篇
  1973年   6篇
  1972年   12篇
排序方式: 共有934条查询结果,搜索用时 0 毫秒
71.
α-Iron-dispersed carbon was synthesized, through pressure pyrolysis of divinylbenzene-vinylferrocene above 750°C, and by reduction of magnetite-dispersed carbon. Divinylbenzenevinylferrocene copolymer was pyrolysed at 125 MPa above 750°C to yield carbons dispersed with α-iron accompanied by cementite. Magnetite in the carbon matrix was reduced to α-iron after heat treatments at 500°C in a flow of hydrogen. Carbons synthesized by the pressure pyrolysis of divinylbenzene-vinylferrocene at 800°C and 125 MPa contained iron-compound particles up to 200 nm, whereas the median diameter of α-iron particles in the carbon matrix after reduction treatments was 20 nm. α-Iron-dispersed carbon had a Curie temperature of 770°C. The saturation magnetization of iron-dispersed carbon increased with increasing the pyrolysis temperature of divinylbenzene-vinylferrocene copolymer, and reached a constant value of 183 e.m.u.g−1 at 800°C. The saturation magnetization of α-iron-dispersed carbon after the reduction treatment revealed practically the theoretical value of α-iron. Carbons finely dispersed with only α-iron particles were synthesized successfully by reduction of magnetitedispersed carbons.  相似文献   
72.
Developers used in photolithography contain toxic tetramethylammoniumhydroxide (TMAH) and this creates a problem of how to properly treat developer wastewater. We have developed a TMAH wastewater treatment technique that consists of a combination of two novel decomposition processes: pyrolyzing TMAH to TMA and decomposing TMA to N 2, H2O, and CO2 by means of a selective oxidation catalyst for nitrogenous compounds. We have tested a system using this technique in long-term treatment of the actual wastewater and have found it to be sufficiently practical. The running cost of a treatment system using our technique would be about one-ninth that of disposing of the wastewater as industrial waste but about 2.3 times that of biological treatment. Compared with biological treatment, however, our system is tolerant to many treatment conditions and operation management is much easier. Furthermore, it occupies only about one-sixth the area of a biological treatment system  相似文献   
73.
This paper proposes a fast convergence algorithm for sparse-tap adaptive finite impulse response (FIR) filters to identify an unknown number of multiple dispersive regions. Coefficient values and tap-positions of the adaptive filter are simultaneously controlled. A constrained region for new-tap positions is selected from equisize subgroups of all possible tap-positions, and it hops from one subgroup to another to cover multiple dispersive regions. The hopping order and the stay time for each subgroup are adaptively determined based on the absolute coefficient values. Simulation results with colored signals show that the proposed algorithm saves more than 80% in the convergence time over the full-tap NLMS and 50% over the STWQ. Tracking capability of the proposed algorithm exhibits its superior characteristics. These characteristics are confirmed by hardware evaluations with a telephone network simulator.  相似文献   
74.
75.
Gianotti-Crosti syndrome (GCS) is characterized by a distinctive self-limiting acral papular or papulovesicular eruption associated with an underlying viral illness. It has not been previously reported in patients post-bone marrow transplantation. We report a 6-year-old Japanese boy who underwent allogeneic bone marrow transplantation from an unrelated donor for acute lymphoblastic leukemia (ALL) in second remission. He had clinical and histopathologic findings characteristic of GCS and evidence of subclinical infection with cytomegalovirus (CMV) detected by CMV antigenemia assay. It is likely that CMV is the causative agent for the GCS in this case.  相似文献   
76.
Anatase-type TiO2 solid solutions doped with 0–10 mol% scandium were formed by hydrothermal crystallization under weak basic conditions above 180°C for 5 h from amorphous co-precipitates that were obtained from the aqueous precursor solutions of TiOSO4 and Sc(NO3)3 using aqueous ammonia. The anatase particles were spindle-like and consisted of nanosized-crystallites (23–25 nm). The lattice parameter c 0 of anatase and the length and width of the spindle-like anatase gradually increased when the scandium content was increased. The diffuse reflectance spectra of the as-prepared TiO2 doped with scandium showed that the onset of absorption slightly shifted to longer wavelengths with increasing scandium content. The band gap of anatase was slightly increased by making solid solutions with scandium oxide.  相似文献   
77.
Summary Poly(proline) and random copolypeptide composed of Pro and Ala residues were synthesized, and their solution properties and molecular conformation were investigated. Aqueous solutions of the polypeptide were irradiated with γ-rays above the transition temperature. It was shown that the transition temperature of the aqueous solution of the copolypeptide is influenced by Ala-residue content and γ-ray irradiation.  相似文献   
78.
Amorphous LiCoO2 thin films were deposited on the NASICON-type glass ceramics, Li1+x+yAlxTi2−xSiyP3−yO12 (LATSP), by radio frequency (RF) magnetron sputtering below 180 °C. The as-deposited LiCoO2 thin films were characterized by X-ray diffraction, scanning electron microscopy and atomic force microscope. All-solid-state Li/PEO18-Li (CF3SO2)2N/LATSP/LiCoO2/Au cells were fabricated using the amorphous film. The electrochemical performance of the cells was investigated by galvanostatic cycling, cyclic voltammetry, potentiostatic intermittent titration technique and electrochemical impedance spectroscopy. It was found that the amorphous LiCoO2 thin film shows a promising electrochemical performance, making it a potential application in microbatteries for microelectronic devices.  相似文献   
79.
Interventions to support children with autism often include the use of visual supports, which are cognitive tools to enable learning and the production of language. Although visual supports are effective in helping to diminish many of the challenges of autism, they are difficult and time-consuming to create, distribute, and use. In this paper, we present the results of a qualitative study focused on uncovering design guidelines for interactive visual supports that would address the many challenges inherent to current tools and practices. We present three prototype systems that address these design challenges with the use of large group displays, mobile personal devices, and personal recording technologies. We also describe the interventions associated with these prototypes along with the results from two focus group discussions around the interventions. We present further design guidance for visual supports and discuss tensions inherent to their design.  相似文献   
80.
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