全文获取类型
收费全文 | 10592篇 |
免费 | 442篇 |
国内免费 | 20篇 |
专业分类
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 |
出版年
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.
Emmanuel. Delamarche Bruno. Michel Hans A. Biebuyck Christoph Gerber 《Advanced materials (Deerfield Beach, Fla.)》1996,8(9):719-729
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.
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