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   11069篇
  免费   1074篇
  国内免费   217篇
电工技术   133篇
综合类   427篇
化学工业   2511篇
金属工艺   288篇
机械仪表   409篇
建筑科学   373篇
矿业工程   177篇
能源动力   143篇
轻工业   5190篇
水利工程   42篇
石油天然气   338篇
武器工业   39篇
无线电   222篇
一般工业技术   1029篇
冶金工业   373篇
原子能技术   242篇
自动化技术   424篇
  2024年   91篇
  2023年   250篇
  2022年   385篇
  2021年   591篇
  2020年   550篇
  2019年   467篇
  2018年   479篇
  2017年   442篇
  2016年   460篇
  2015年   461篇
  2014年   642篇
  2013年   919篇
  2012年   782篇
  2011年   702篇
  2010年   558篇
  2009年   512篇
  2008年   452篇
  2007年   527篇
  2006年   486篇
  2005年   394篇
  2004年   335篇
  2003年   320篇
  2002年   262篇
  2001年   219篇
  2000年   169篇
  1999年   144篇
  1998年   121篇
  1997年   118篇
  1996年   70篇
  1995年   65篇
  1994年   59篇
  1993年   51篇
  1992年   53篇
  1991年   15篇
  1990年   25篇
  1989年   20篇
  1988年   15篇
  1987年   26篇
  1986年   23篇
  1985年   31篇
  1984年   22篇
  1983年   10篇
  1982年   17篇
  1981年   5篇
  1980年   10篇
  1979年   1篇
  1978年   1篇
  1976年   1篇
  1970年   1篇
  1951年   1篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
生物工程发酵饮料—醋酸饮料   总被引:2,自引:0,他引:2  
本文着重介绍醛酸饮料的形成、特点和营养保健作用。  相似文献   
42.
Frankfurters were manufactured from lean meats (100% beef and 50:50 beef-pork) to contain reduced levels of fat (about 1.3%). A curing solutibn was added to yield 160% of fresh meat weight. Three processing methods, coarse ground tumbled, fine ground tumbled and fine ground emulsified were used. All products were cooked in live steam to 71°C internal temperature. Product yields, penetrometer values, color, chemical composition, caloric content and added water were evaluated. Emulsified frankfurters from 50:50 beef-pork mixtures at 160% cure had texture similar to conventional product as well as increased (P<0.05) yields, acceptable color and 74% fewer calories.  相似文献   
43.
C.S. Li  P.K. Hopke 《Indoor air》1992,2(2):84-100
Air cleaning as a means of mitigating the risks arising from exposure to indoor radon progeny has been evaluated in a single-family house in the north eastem US. using an automated, semi-continuous activity-weighted size distribution measurement system. The measurements included radon concentration, condensation nuclei count, and activity-weighted size distribution of radon decay products. Measurements were made in the house with and without an operating air filtration system and with various particle sources common to normal indoor activities operating. Aerosols were generated by running water in a shower, candle burning, cigarette smoking, vacuuming, opening doors, and cooking. Using a room model, the changes in attachment rates, average attachment diameters, and deposition rates of the unattached fraction with and without the air cleaning system were calculated. In the presence of active aerosol sources, the air filtration unit typically reduced the concentration of particles within the hour following the end of particle generation. After candle burning, cigarette smoking, and vacuuming in the bedroom, the reductions of PAEC by air filtration are about 60% with the air filtration system operating in the bedroom. During cooking in the kitchen, the reductions of PAEC in the bedroom with the air filtration system were about 40%. However, for all cases the dose reductions were smaller than the particle and PAEC reductions. For those particles that were generated within the bedroom, there was a 20% to 50% reduction in dose. In the case of cooking where the door was open and particles infiltrated from the rest of the house, the dose reduction was only 5% on average and appears to be insignificant. Thus, the dose reductions were h e r than the reductions in activity concentration, but there were no cases where the estimated dose actually increased.  相似文献   
44.
Ben M. Benjamin  Emily C. Douglas 《Fuel》1986,65(12):1735-1739
The object of this paper is to demonstrate the usefulness of the transalkylation reaction for determining chemical structural features of products derived from coal. For example, the method is applied to derivatized coals, coals modified by thermolysis, and materials physically or chemically separated from coals. Data are presented for the pyridine soluble and insoluble parts of two coals, an O-methylated coal, a Birch reduced coal, a solvent refined coal, and a coke. Similarities and differences in chemical make-up of these materials are discussed.  相似文献   
45.
分析了中油站产生一些油品质量事故的情况和成因。指出加油站油品的质量事故主要是管理不善,要杜绝加油站油品质量事故,必须坚持执行《中国石油化工集团销售企业油品质管理办法》。  相似文献   
46.
A continuous process for the extraction of sunflower oil using supercritical CO2, featuring multiple extractors, one oil separator and three cascaded CO2 recovery vessels operating at different pressures, was devised and studied. For every single equipment of the plant making up the process a mathematical model was built. Experimental tests—consisting in measurements of oil solubility in supercritical CO2—were carried out in a laboratory-scale apparatus to characterise the behaviour of sunflower oil in the separation from the supercritical fluid. The mathematical model of the whole process was coded in the commercial gPROMS process modelling environment where both its simulation and optimisation—this latter assuming the overall oil production cost as the objective function—were carried out. The process- and economics-related results are discussed and compared with those obtained with traditional and cold-pressing extraction.  相似文献   
47.
香肠作为具有中国特色的传统肉制品,倍受广大消费者的喜爱,然而传统香肠单一口味已不能满足那些喜爱吃麻辣口味的消费者的需求,特别是在秋冬季节,吃麻辣已成为一种流行趋势,开发麻辣口味香肠,迎合消费者需求已是一种趋势;本试验采用正交设计方案。确定食盐、白糖、红辣椒粉、复合香辛料的添加量分别为:3%、2%、0.5%、0.41%。  相似文献   
48.
应用裂变产物混合物做为示踪剂研究了~(137)Cs,~(141,144)Ce,~(103,106)Ru,~(103,106)Ru,~(95)Zr,~(95)Nb,~(89,90)Sr在花岗岩、凝灰岩、页岩上的吸附行为。应用批式技术测定了吸附比。核素的γ放射性是用连有SCORPIO-3000多道计算机系统的Ce(Li)探测器测量的。β放射性~(89,90)Sr是放化分离后在G-M计数器上测量的。结果表明:凝灰岩、页岩能强烈吸附Ce,Nb,Zr;吸附Cs居中;吸附Sr,Ru较差;花岗岩的吸附性能都差。  相似文献   
49.
The influence of NaCl and CO2 on the atmospheric corrosion of magnesium alloy AZ91 is studied in the laboratory. Samples were exposed under carefully controlled air and flow conditions; the relative humidity was 95%, the temperature was 22.0°C and the concentration of CO2 was < 1 ppm or 350 ppm. Different amounts of sodium chloride (0–70 μg/cm2) were added before exposure. The corrosion products were analyzed by gravimetry, ion chromatography, X‐ray diffraction and scanning electron microscopy. Mass gain and metal loss results are reported. The combination of high humidity and NaCl is very corrosive towards AZ91. However, the NaCl‐induced corrosion is inhibited by ambient concentrations of CO2. Exposure in the absence of CO2 gives rise to heavy pitting, with brucite, Mg(OH)2, being the dominant corrosion product. In the presence of CO2 a layer of hydrated magnesium hydroxy carbonate, Mg5(CO3)4(OH)2 · 5 H2O forms. A tentative corrosion mechanism is presented that explains the behavior in the two environments.  相似文献   
50.
从数字看发展片式电容器面临的机遇与挑战   总被引:11,自引:2,他引:9  
采用海关进、出口统计和行业生产统计资料,通过计算、分析,用数字来说明国内发展片式多层陶瓷电容器、片式钽电解电容器、片式铝电解电容器、片式有机薄膜电容器所面临的机遇与挑战,并对其国内市场需求总量、额,国产品在国内市场占有率等做出评估,为有关单位了解片式电容器的发展提供参考,为国产产品更有效地进入国内市场、促进其发展提供依据。  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