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   10592篇
  免费   442篇
  国内免费   20篇
电工技术   221篇
综合类   40篇
化学工业   2886篇
金属工艺   212篇
机械仪表   205篇
建筑科学   741篇
矿业工程   32篇
能源动力   217篇
轻工业   1164篇
水利工程   69篇
石油天然气   15篇
无线电   602篇
一般工业技术   1982篇
冶金工业   1125篇
原子能技术   98篇
自动化技术   1445篇
  2022年   78篇
  2021年   154篇
  2020年   129篇
  2019年   125篇
  2018年   146篇
  2017年   179篇
  2016年   252篇
  2015年   238篇
  2014年   309篇
  2013年   495篇
  2012年   438篇
  2011年   562篇
  2010年   448篇
  2009年   476篇
  2008年   459篇
  2007年   481篇
  2006年   436篇
  2005年   404篇
  2004年   357篇
  2003年   263篇
  2002年   248篇
  2001年   198篇
  2000年   194篇
  1999年   178篇
  1998年   209篇
  1997年   177篇
  1996年   172篇
  1995年   143篇
  1994年   129篇
  1993年   154篇
  1992年   154篇
  1991年   108篇
  1990年   118篇
  1989年   117篇
  1988年   99篇
  1987年   120篇
  1986年   101篇
  1985年   118篇
  1984年   119篇
  1983年   97篇
  1982年   110篇
  1981年   113篇
  1980年   95篇
  1979年   90篇
  1978年   83篇
  1977年   83篇
  1976年   91篇
  1975年   93篇
  1974年   89篇
  1973年   76篇
排序方式: 共有10000条查询结果,搜索用时 664 毫秒
41.
阿维斯塔波莱瑞特厂正在进行一个现代化改造项目,以提高炉卷轧机的生产能力,达到年产100万吨。但是,由于在阿维斯塔波莱瑞特厂炉卷轧机上的现有技术已达到极限,只有通过对轧机及自动化系统进行现代化的改造才有可能提高和增强轧机的利用率和易维护性。  相似文献   
42.
To clarify whether motion information per se has a separable influence on action control, the authors investigated whether irrelevant direction of motion of stimuli whose overall position was constant over time would affect manual left-right responses (i.e., reveal a motion-based Simon effect). In Experiments 1 and 2, significant Simon effects were obtained for sine-wave gratings moving in a stationary Gaussian window. In Experiment 3, a direction-based Simon effect with random-dot patterns was replicated, except that the perceived direction of motion was based on the displacement of single elements. Experiments 4 and 5 studied motion-based Simon effects to point-light figures that walked in place--displays requiring high-level analysis of global shape and local motion. Motion-based Simon effects occurred when the displays could be interpreted as an upright human walker, showing that a high-level representation of motion direction mediated the effects. Thus, the present study establishes links between high-level motion perception and action. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
43.
During the BOF process for the production of crude steel, the specific amount of dust emitted is of the order of 2 % of the steel weight at turn down. The process gas conveys the dust through the boiler system into the primary and secondary dust catchers. The transportation of dust particles is influenced by blowing parameters; physical properties of process gas and of dust phases; and, type and layout of the converter and the filter system. In this work, a numerical simulation model is developed that simulates the pneumatic conveyance and sedimentation of primarily coarse dust particles in the BOF gas cleaning system. Comparison is then made of predicted coarse dust characteristics with values for dust sampled from an existing plant in order to verify the plausibility of the developed model.  相似文献   
44.
Part 1 of this contribution reported on the effects of system properties on heat transfer between heating or cooling surfaces and bubbling fluidized beds. This investigation produced four correlations which define the respective maximum heat transfer. Part 2 of this study suggests that the heat transfer between exchanger surfaces and bubbling fluidized beds depends on superficial gas velocity, expressed as dimensionless excess gas velocity. The present paper shows that heat transfer coefficients in circulating fluidized beds can be predicted by evaluation of a state diagram, which combines three dimensionless groups: Nusselt number, Archimedes number and a dimensionless pressure gradient. A comparison of coal combustion experiments with own cold model measurements indicates that the radiative component of heat transfer coefficients is only evident at very low dimensionless pressure gradients.  相似文献   
45.
46.
OBJECTIVE: To study the effects of thevetoside (TS), a cardiac glycoside, and an inhibitor of Na+, K(+)-ATPase, on tumor cells cultured in vitro. METHODS: The cytotoxic effects of TS on tumor cells were determined by trypan blue dye exclusion, neutral red vital staining and clonogenic assay. The time-effect relationship and growth inhibition of tumor cells by TS were assayed with trypan blue exclusion method. RESULTS: TS at low doses (0.005-0.1 mg.L-1), with dose dependence, was able to kill SMMC-7721, SGC-7901 and HeLa cells. IC50 values for SMMC-7721, SGC-7901 and HeLa cells were 0.007, 0.011 and 0.018 mg.L-1 by trypan blue dye exclusion test and 0.016, 0.055 and 0.078 mg.L-1 by neutral red vital staining test. TS inhibited the clonal forming rate of SMMC-7721 and SGC-7901 significantly with IC50 values of 0.021 and 0.036 mg.L-1, respectively. Only when the cells were continuously treated with TS for more than 8 hours, the drug-induced cell lethality could be displayed and strengthened quickly. The growth of tumor cells was notably inhibited after they were exposed to 0.1 microgram/ml of TS for 12 hours. All the experimental results of antitumor activity in vitro showed that SMMC-7721 was most sensitive to TS among the three kinds of tumor cells. CONCLUSIONS: TS has cytotoxic action on tumor cells cultured in vitro and this lethal effect must have an action process, in which tumor cells are not dead but suffer from deadly injury and lost the capability of unlimited proliferation.  相似文献   
47.
Self-assembled monolayers (SAMs) of alkanethiols and disulfides on gold form organic interfaces with properties largely controlled by the end groups of the molecules composing the film. SAMs provide a unique link between the science of organic surfaces and technologies that seek to exploit their adaptable character. Many techniques are useful for probing the structure of SAMs although only scanning tunneling microscopy (STM) at picoamperes reveals the details of the packing of their end groups at the sub-angstrom level. This review demonstrates that STM effectively tests new types of control over the microscopic structure–property relationships characteristic of SAMs on gold that should prove useful to their application.  相似文献   
48.
49.
50.
Hans R. Kricheldorf  Volker D  ring 《Polymer》1992,33(24):5321-5327
The homopolyester of 4-(4′-hydroxyphenoxy)benzoic acid (poly(4-HPBA)), was prepared under two different reaction conditions and compared with a sample provided by another research group. Depending on the synthetic route, different melting points, d.s.c. traces and crystal lattices were found. However, after repeated heating and cooling, one thermodynamically stable modification with a melting point of 370–375°C can be obtained. Copolyesters of 4-hydroxybenzoic acid and 4-(4′-hydroxyphenoxy)benzoic acid were prepared with various molar ratios either in the melt (condensation in bulk) or in solution. These copolyesters were characterized by elemental analyses, 1H n.m.r. spectroscopy, d.s.c. measurements, wide-angle X-ray scattering measurements at various temperatures, and optical microscopy. Whereas copolyesters prepared in solution do not melt below 500°C, those prepared by polycondensation in bulk show melting points down to approximately 260°C and form a nematic melt.  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