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   1528篇
  免费   12篇
电工技术   8篇
综合类   1篇
化学工业   95篇
金属工艺   11篇
机械仪表   2篇
建筑科学   27篇
能源动力   8篇
轻工业   20篇
水利工程   7篇
石油天然气   1篇
无线电   34篇
一般工业技术   66篇
冶金工业   1225篇
自动化技术   35篇
  2023年   4篇
  2022年   10篇
  2021年   4篇
  2020年   3篇
  2019年   9篇
  2018年   3篇
  2017年   10篇
  2016年   9篇
  2015年   3篇
  2014年   8篇
  2013年   15篇
  2012年   15篇
  2011年   11篇
  2010年   12篇
  2009年   9篇
  2008年   15篇
  2007年   13篇
  2006年   18篇
  2005年   15篇
  2004年   9篇
  2003年   11篇
  2002年   12篇
  2001年   6篇
  2000年   7篇
  1999年   36篇
  1998年   337篇
  1997年   190篇
  1996年   142篇
  1995年   73篇
  1994年   77篇
  1993年   77篇
  1992年   18篇
  1991年   32篇
  1990年   22篇
  1989年   23篇
  1988年   24篇
  1987年   27篇
  1986年   17篇
  1985年   26篇
  1984年   2篇
  1983年   8篇
  1982年   13篇
  1981年   15篇
  1980年   10篇
  1979年   3篇
  1978年   4篇
  1977年   30篇
  1976年   94篇
  1975年   6篇
  1930年   1篇
排序方式: 共有1540条查询结果,搜索用时 31 毫秒
91.
The treatment and favorable outcome of a bitch with uterine torsion and two retained fetuses are described. The condition was corrected surgically by ovariohysterectomy. Complications (i.e., septic shock, peritonitis, and hemostatic abnormalities) were managed with aggressive medical therapy. Torsion of the gravid uterus in dogs is a life-threatening condition which can have a successful outcome if medical complications encountered in the pre- and postoperative periods are treated quickly and effectively.  相似文献   
92.
The phase separation at 550 °C in a Ni-12.7 at. pct Al alloy was investigated by means of small angle X-ray scattering, large angle X-ray scattering, electrical resistivity, and transmission electron microscopy. It was found that an abrupt change in the electrical resistivity and small angle scattering occurred within 15 seconds at 550 °C, following quenching from 1060 °C, and transmission electron microscopy confirmed the presence of small nuclei. However, after this period of rapid change, there was an incubation period of about ten hours in which there was minimal net growth of the nuclei. After the incubation period, growth was accelerated. High angle side bands were observed after a few minutes annealing, and their development closely paralleled the growth of the nuclei and precipitate particles at this temperature. For times beyond the incubation period, small angle X-ray scattering diagrams from single crystals became markedly anisotropic, indicating a quasi-regular spatial distribution of particles. The large and rapid change, in both electrical resistivity and in X-ray small angle scattering, observed after annealing at 550 °C of samples quenched from 1060 °C was attributed to the formation of tiny regions of short range ordered Ni3Al which constitute subcritical nuclei.  相似文献   
93.
This paper presents a study of possible changes in patterns of document types in economics journals since the mid-1980s. Furthermore, the study includes an analysis of a possible relation between the profile of a journal concerning composition of document types and factors such as place of publication and JIF. The results provide little evidence that the journal editors have succeeded in manipulating the distribution of document types. Furthermore, there is little support for the hypothesis that journal editors decrease the number of publications included in the calculation of JIF or for that matter for the hypothesis that journal editors increase the number of publications not included in the calculation of JIF. The results of the analyses show that there is a clear distinction of journals based on place of publication and JIF  相似文献   
94.
95.
96.
97.
Porous acicular mullite (ACM) ceramics are known to be mechanically robust even at high porosities. This study was undertaken to better understand what aspects of acicular mullite's needle-like microstructure affect the overall mechanical properties and how the microstructure might be modified to improve mechanical performance. ACMs with a variety of porosities, pore sizes, and needle diameters were produced, and their elastic moduli, flexure strengths, and fracture toughnesses were measured. Three-dimensional image analysis was an invaluable tool in determining the needle diameters of these complex 3D network structures. It was found that porosity was the most dominant factor in determining the mechanical properties of ACM and that its behavior could be described using the Gibson–Ashby foam model.  相似文献   
98.
The production of printed electronics exhibits an enormous economical potential due to the possibility to manufacture innovative products at low cost. At the moment, one of the major challenges for the fabrication of printed electronics is the controllability of the material properties during processing and the miniaturization of the deposited structures. In this context, the application of soft lithographic techniques appears promising, because they allow a defined patterning of the materials in the range of few nanometers, which is far below the limits of other printing techniques like inkjet-printing or screen printing. This work proves the applicability of the soft lithographic technique micro-molding in capillaries (MIMIC) for the manufacture of conductive indium tin oxide (ITO) electrodes. For the creation of stable dispersions of ITO nano-sized particles, steric as well as electrostatic stabilization concepts are applied. The prepared dispersions are characterized with regard to the later processing via MIMIC. The geometry and the electrical properties of the soft lithographically deposited structures are determined to prove their functionality. Special attention is paid to the influence of the wetting behavior of the dispersions on the resulting geometry of the structures. Finally, the applicability of the optimized structures is demonstrated by the assembly of a thin film transistor (TFT), in which the deposited structures serve as source and drain electrodes.  相似文献   
99.
An electrodeposition technique has been adapted to produce copper–silicon carbide composites with honeycomb-like microstructures. The detrimental Cu–SiC reaction was avoided by using this room temperature processing technique. The wood-derived silicon carbide phase allows for tailorable microstructures due to the variety of available wood precursors. Plating efficiency for each wood type was determined using image analysis. This processing method results in the successful filling of pores with aspect ratios of up to 100.  相似文献   
100.
A simple low cost method is proposed for the quantitative analysis of residual alcohol in biodiesel through determination of the flash point, with which it is correlated. Methyl ester biodiesels from vegetable oils such as corn, soy and sunflower were prepared. The ethyl ester was obtained from soy oil and methyl biodiesel was also synthesized from bovine fat. In all cases it became very evident that there is a direct correlation between the flash point and the residual alcohol content in the prepared biodiesel. Therefore this parameter can be used to directly determine the residual alcohol content of the product.  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