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   118634篇
  免费   12230篇
  国内免费   6490篇
电工技术   16946篇
技术理论   16篇
综合类   7926篇
化学工业   13722篇
金属工艺   6276篇
机械仪表   5779篇
建筑科学   11933篇
矿业工程   3603篇
能源动力   17064篇
轻工业   7287篇
水利工程   2602篇
石油天然气   3974篇
武器工业   1265篇
无线电   10194篇
一般工业技术   12056篇
冶金工业   4943篇
原子能技术   1690篇
自动化技术   10078篇
  2024年   494篇
  2023年   2606篇
  2022年   3941篇
  2021年   4671篇
  2020年   4914篇
  2019年   4276篇
  2018年   3595篇
  2017年   4347篇
  2016年   4744篇
  2015年   4818篇
  2014年   8231篇
  2013年   7503篇
  2012年   8943篇
  2011年   9674篇
  2010年   7182篇
  2009年   7195篇
  2008年   6348篇
  2007年   7318篇
  2006年   6125篇
  2005年   4940篇
  2004年   4222篇
  2003年   3671篇
  2002年   3075篇
  2001年   2639篇
  2000年   2237篇
  1999年   1798篇
  1998年   1426篇
  1997年   1094篇
  1996年   983篇
  1995年   756篇
  1994年   665篇
  1993年   525篇
  1992年   442篇
  1991年   348篇
  1990年   275篇
  1989年   231篇
  1988年   201篇
  1987年   140篇
  1986年   111篇
  1985年   142篇
  1984年   112篇
  1983年   73篇
  1982年   87篇
  1981年   41篇
  1980年   51篇
  1979年   29篇
  1978年   18篇
  1977年   18篇
  1974年   12篇
  1951年   18篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
This study aimed to know the effect of adding pulp in rambutan fruit juice on the characteristics of rambutan juice during storage. Research using the CRD, the treatment were kind of pulp (mandarin and rambutan) and pulp concentration (5%, 7.5%, and 10%). The results showed that the addition of pulp significantly affect the characteristics of rambutan juice (pH, vitamin C, total acid) during storage. Pulpy juice with the most prefered was addition of rambutan pulp as much as 7.5% (w/v) and the addition of citrus pulp as much as 7.5% (w/v) with the score of 3-4 (moderate like - like).  相似文献   
102.
Hyperbaric storage (HS) was evaluated as a new food preservation methodology at room temperature (RT) for beef and pork meat, both minced and in pieces, and compared to refrigeration (RF) storage. The meat samples were stored at 50, 75 and 100 MPa and variable RT up to 60 days. HS at 75 and 100 MPa could not only inhibit microbial growth but also inactivate microorganisms. Regarding physicochemical analyses, an overall equal to better pH maintenance in HS samples was achieved, and similar colour differences between HS and RF were observed. Generally, similarities in moisture content and drip loss between HS (mostly 75 and 100 MPa) and RF were detected (tendency for lower values in the former and higher values in the latter for the higher pressure level). Protein solubility revealed a decrease of sarcoplasmic protein values during storage with a pressure level dependency in some samples.  相似文献   
103.
Using mean value theorem for integrals we show that the well-known LCOE definition is incorrect.  相似文献   
104.
Automatic load shedding is the ultimate countermeasure against imbalance in a power system and can effectively help preventing large blackouts. Taking into account a high penetration of renewable energy sources (RES) in the distribution grid, a clear distinction between load and generation at the PCC becomes increasingly more difficult. For that reason an adaptation of frequency relay parameters and their locations of installation are necessary. In Europe this is rest on a multi-step plan based on values such as the yearly peak load. In this paper a novel probabilistic method for automatic load shedding is presented that uses the average values instead of peak values for load shedding. Its applicability is verified by a dynamic power system model that was developed to compare the classical and novel probabilistic load shedding principle. The method is verified using data from a German TSO.  相似文献   
105.
Light-emitting field effect transistors (LEFETs) are a class of organic optoelectronic device capable of simultaneously delivering the electrical switching characteristics of a transistor and the light emission of a diode. We report on the temperature dependence of the charge transport and emissive properties in a model organic heterostructure LEFET system from 300 K to 135 K. We study parameters such as carrier mobility, brightness, and external quantum efficiency (EQE), and observe clear thermally activated behaviour for transport and injection. Overall, the EQE increases with decreasing temperature and conversely the brightness decreases. These contrary effects can be explained by a higher recombination efficiency occurring at lower temperatures, and this insight delivers new knowledge concerning the optimisation of both the transport and emissive properties in LEFETs.  相似文献   
106.
107.
In 2018, Mishik Airazatovich Kazaryan received the highest award of the International Association for Alternative Energy and Ecology - Order of Antoine de Saint-Exupéry “For Improving the Quality of Life on the Planet of People” (IAAEE) on nominating the Award Committee of the Editorial Board of the International Scientific Journal for Alternative Energy and Ecology (ISJAEE). The award was given for his outstanding contribution to development of alternative energetics and ecology. M.A. Kazaryan's prominent contribution to the development of alternative energetics and ecology is based on his pioneering works in the field of development of methods for producing hydrogen as environmentally friendly safe fuel, as well as works in the field of processing organic compounds by various physical methods. As a part of joint research with colleagues from Lebedev Physical Institute of RAS (LPI), M.A. Kazaryan participated in creation of new methods for producing hydrogen from various chemical compounds. The method of conversion of liquid-phase compounds in plasma discharges under the influence of intensive ultrasonic cavitation occupies a special place. In the course of these works, it is shown that low-temperature plasma initiated in liquid-phase media in discharge between electrodes is able to effectively decompose hydrogen-containing molecules of organic compounds and form gaseous products where the part of hydrogen is more than 90%. Estimations of energy efficiency calculated taking into account hydrogen combustion heat and initial substances, as well as electricity costs, showed an efficiency level of about 60–70% in depending on the composition of the starting mixture. Another notable contribution of M.A. Kazaryan to the development of alternative energetics was the work on the optimization and justification of technological and structural parameters of energy discharge devices based on high-voltage pulse-periodic discharge for creating a reactor for plasmachemical processing of polymer wastes into hydrogen and other valuable compounds.  相似文献   
108.
340管线矫直机是太原重工成熟产品,在国内占有较大市场,并出口印度、印尼、缅甸、埃及等国际市场。出口印度矫直机在质保期内出现主缸裂纹问题,为探明问题原因并杜绝类似情况发生,快开机构设计静强度分析、疲劳强度分析及生产加工过程等方面探查裂纹原因并提出几点预防措施。  相似文献   
109.
To improve the electrochemical properties of rare-earth–Mg–Ni-based hydrogen storage alloys, the effects of stoichiometry and Cu-substitution on the phase structure and thermodynamic properties of the ...  相似文献   
110.
《Ceramics International》2020,46(8):12080-12087
(1-x) Ba(Zr0.2Ti0.8)O3-x Na0.5Bi0.5TiO3 (x = 0, 10, 20 30, 40, 50 mol%) (BZTN) ceramics are prepared by the traditional solid phase method. All BZTN ceramics exhibit a pseudo-cubic BZT based perovskite structure. Both the average grain size and the relaxor ferroelectricity of BZTN ceramics gradually increase with increasing NBT content. The Wrec of 3.22 J/cm3 and η of 91.2% is obtained for the BZTN40 ceramic at 241 kV/cm. BZTN40 ceramic also exhibits good temperature stability from room temperature to 150 °C and frequency stability from 1 Hz to 100 Hz. A PD of 0.621 J/cm3 and a t0.9 of 82 ns is obtained for the BZTN40 ceramic at 120 kV/cm. BZTN ceramics show application potential in energy storage and pulse power capacitors.  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