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   56160篇
  免费   2316篇
  国内免费   370篇
电工技术   824篇
综合类   572篇
化学工业   10480篇
金属工艺   1234篇
机械仪表   1461篇
建筑科学   2803篇
矿业工程   292篇
能源动力   1607篇
轻工业   4898篇
水利工程   667篇
石油天然气   293篇
武器工业   32篇
无线电   4821篇
一般工业技术   8845篇
冶金工业   10238篇
原子能技术   436篇
自动化技术   9343篇
  2023年   291篇
  2022年   399篇
  2021年   1127篇
  2020年   716篇
  2019年   937篇
  2018年   1144篇
  2017年   1040篇
  2016年   1217篇
  2015年   1093篇
  2014年   1558篇
  2013年   3365篇
  2012年   2450篇
  2011年   3041篇
  2010年   2374篇
  2009年   2341篇
  2008年   2582篇
  2007年   2576篇
  2006年   2287篇
  2005年   2034篇
  2004年   1847篇
  2003年   2015篇
  2002年   2231篇
  2001年   1713篇
  2000年   1132篇
  1999年   1122篇
  1998年   1907篇
  1997年   1429篇
  1996年   1181篇
  1995年   998篇
  1994年   835篇
  1993年   856篇
  1992年   690篇
  1991年   438篇
  1990年   563篇
  1989年   522篇
  1988年   449篇
  1987年   464篇
  1986年   422篇
  1985年   567篇
  1984年   500篇
  1983年   407篇
  1982年   378篇
  1981年   383篇
  1980年   365篇
  1979年   330篇
  1978年   295篇
  1977年   323篇
  1976年   396篇
  1975年   245篇
  1973年   214篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Load testing of applications is an important and costly activity for software provider companies. Classical solutions are very difficult to set up statically, and their cost is prohibitive in terms of both human and hardware resources. Virtualized cloud computing platforms provide new opportunities for stressing an application's scalability, by providing a large range of flexible and less expensive (pay‐per‐use model) computation units. On the basis of these advantages, load testing solutions could be provided on demand in the cloud. This paper describes a Benchmark‐as‐a‐Service solution that automatically scales the load injection platform and facilitates its setup according to load profiles. Our approach is based on: (i) virtualization of the benchmarking platform to create self‐scaling injectors; (ii) online calibration to characterize the injector's capacity and impact on the benched application; and (iii) a provisioning solution to appropriately scale the load injection platform ahead of time. We also report experiments on a benchmark illustrating the benefits of this system in terms of cost and resource reductions. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   
32.
Excessive energy intake may evoke complex biochemical processes characterized by inflammation, oxidative stress, and impairment of mitochondrial function that represent the main factors underlying noncommunicable diseases. Because cow milk is widely used for human nutrition and in food industry processing, the nutritional quality of milk is of special interest with respect to human health. In our study, we analyzed milk produced by dairy cows fed a diet characterized by a high forage:concentrate ratio (high forage milk, HFM). In view of the low n-6:n-3 ratio and high content of conjugated linoleic acid of HFM, we studied the effects of this milk on lipid metabolism, inflammation, mitochondrial function, and oxidative stress in a rat model. To this end, we supplemented for 4 wk the diet of male Wistar rats with HFM and with an isocaloric amount (82 kJ, 22 mL/d) of milk obtained from cows fed a diet with low forage:concentrate ratio, and analyzed the metabolic parameters of the animals. Our results indicate that HFM may positively affect lipid metabolism, leptin:adiponectin ratio, inflammation, mitochondrial function, and oxidative stress, providing the first evidence of the beneficial effects of HFM on rat metabolism.  相似文献   
33.
34.
35.
为降低老石旦洗煤厂的粗精煤灰分,在对粗煤泥性质分析的基础上,采用MC脉冲粗煤泥分选机对其进行分选。介绍了该分选机的结构、工作原理、技术特点、技术参数,并分析了其在老石旦洗煤厂的应用情况。生产实践表明:MC脉冲粗煤泥分选机不但可降低粗精煤灰分,而且可提高其产率。该分选机投入使用后粗精煤灰分下降3个百分点,总精煤产率提高0.5个百分点,达到了降灰的目的。  相似文献   
36.
37.
38.
This work investigates emulsion templating to synthesize hexadecane oil/geopolymer composites. In a system with hexadecane as the internal (dispersed) phase and an alkali activated continuous phase without added surfactant, adding aluminosilicate clay particles does not increase resistance against creaming or coalescence, while adding a surfactant (L35 or CTAB) stabilizes the solid-liquid interface. Infrared studies and rheological studies of the associated geopolymerization determined that the presence of the organic phase or surfactant has no significant effect on the geopolymerization kinetics, as determined by the change in time of the Si-O-T IR stretching frequency and the rheological moduli involved during the process. The stabilization of the organic template is reminiscent of Pickering emulsion even though we employ a much greater amount of inorganic material for geopolymer formation. Although the addition of surfactant has a significant effect on the behavior of the paste, the percolation of the network remains unmodified, highlighting the fact that the phenomenon is not dependent on viscosity. Finally, rheological measurements were used to obtain the mass fractal dimension of the as-made gel network, which is able to differentiate the interfacial effect between surfactant molecules with a slightly denser interphase when a cationic surfactant is used.  相似文献   
39.
Processing lithium-ion battery (LIB) electrode dispersions with water as the solvent during primary drying offers many advantages over N-methylpyrrolidone (NMP). An in-depth analysis of the comparative drying costs of LIB electrodes is discussed for both NMP- and water-based dispersion processing in terms of battery pack $/kWh. Electrode coating manufacturing and capital equipment cost savings are compared for water vs. conventional NMP organic solvent processing. A major finding of this work is that the total electrode manufacturing costs, whether water- or NMP-based, contribute about 8–9% of the total pack cost. However, it was found that up to a 2?×?reduction in electrode processing (drying and solvent recovery) cost can be expected along with a $3–6?M savings in associated plant capital equipment (for a plant producing 100,000 10-kWh Plug-in Hybrid Electric Vehicle (PHEV) batteries) using water as the electrode solvent. This paper shows a different perspective in that the most important benefits of aqueous electrode processing actually revolve around capital equipment savings and environmental stewardship and not processing cost savings.  相似文献   
40.
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