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   34173篇
  免费   2455篇
  国内免费   946篇
电工技术   1459篇
技术理论   4篇
综合类   1548篇
化学工业   5622篇
金属工艺   1522篇
机械仪表   1666篇
建筑科学   1675篇
矿业工程   744篇
能源动力   1180篇
轻工业   2184篇
水利工程   446篇
石油天然气   992篇
武器工业   146篇
无线电   5358篇
一般工业技术   5007篇
冶金工业   2708篇
原子能技术   387篇
自动化技术   4926篇
  2023年   418篇
  2022年   618篇
  2021年   1113篇
  2020年   905篇
  2019年   779篇
  2018年   884篇
  2017年   923篇
  2016年   852篇
  2015年   1061篇
  2014年   1407篇
  2013年   2113篇
  2012年   1986篇
  2011年   2308篇
  2010年   1831篇
  2009年   1876篇
  2008年   1929篇
  2007年   1738篇
  2006年   1566篇
  2005年   1254篇
  2004年   1107篇
  2003年   1185篇
  2002年   1392篇
  2001年   1151篇
  2000年   765篇
  1999年   634篇
  1998年   953篇
  1997年   668篇
  1996年   545篇
  1995年   472篇
  1994年   388篇
  1993年   331篇
  1992年   239篇
  1991年   220篇
  1990年   224篇
  1989年   198篇
  1988年   169篇
  1987年   147篇
  1986年   125篇
  1985年   124篇
  1984年   107篇
  1983年   74篇
  1982年   70篇
  1981年   59篇
  1980年   81篇
  1979年   49篇
  1978年   60篇
  1977年   58篇
  1976年   76篇
  1975年   43篇
  1973年   37篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
湖北省地下水流系统划分研究   总被引:1,自引:0,他引:1  
  相似文献   
102.
103.
Rheological properties and gel characteristics of Sparassis crispa polysaccharides (SCPs) were investigated under various concentrations, temperature, pH, salt concentrations, and sucrose concentrations. SCP solutions behaved as shear thinning pseudoplastic fluids; apparent viscosity increased with concentrations but decreased with extreme conditions and was highest for 1% SCPs at 80 ℃ under neutral conditions; 5% SCPs solutions formed a hysteresis loop and exhibited thixotropic properties. By oscillatory measurements, SCPs were viscoelastic materials. 0.5% and 1% SCPs solutions exhibited viscous behavior at low frequency and enhanced elastic property with the oscillation frequency increased. With the concentration increased to 3% and 5%, the elastic property was predominant in solutions and exhibited gel-like behavior. SCPs gel textural properties and water holding capacity increased with concentration (to 20%) and decreased with salinity, extreme sucrose, and pH. 10% SCPs gels were optimized at 10% sucrose in neutral conditions. Thus, these results implied SCPs had the potential utilization as a new hydrocolloid source in food industries.  相似文献   
104.
Li  Zhenxing  Ma  Chang  Wen  Yangyang  Wei  Zhiting  Xing  Xiaofei  Chu  Junmei  Yu  Chengcheng  Wang  Kaili  Wang  Zhao-Kui 《Nano Research》2020,13(1):196-202

With the increasingly prominent energy and environmental issues, the supercapacitors, as a highly efficient and clean energy conversion and storage devices, meet the requirements well. However, it is still a challenge to enhance the capacitance and energy density of supercapacitors. A novel and highly conductive dodecaborate/MXene composites have been designed for high performance supercapacitors. The surface charge property of MXene was modified by a simple ultrasonic treatment with ammonium ion, and the dodecaborate ion can be inserted into the inner surface of MXene by electrostatic adsorption. Due to the unique icosahedral cage conjugate structure formed by the B-B bond and the highly delocalized three-dimensional π bond structure of the electrons, the negative charge is delocalied on the whole dodecaborate ion, which reduces the ability to bind to cations. Therefore, the cations can move easily, and the dodecaborate can act as a “lubricant” for ion diffusion between the MXene layers, which significantly improves the ion transfer rate of supercapacitors. The dodecaborate/MXene composites can achieve an extremely high specific capacitance of 366 F.g-1 at a scan rate of 2 mV.s-1, which is more than eight times higher than that of MXene (43 F1-) at the same scan rate. Our finding provides a novel route on the fabrication of the high performance supercapacitors.

  相似文献   
105.
Journal of Mechanical Science and Technology - The understanding of magnetohydrodynamic phenomena associated with the flow of electrically-conducting fluid in complex ducts is important and...  相似文献   
106.
107.
Water Resources Management - The localization of the leaks is estimated using the time difference method in the past decade. Generalized and Basic Cross-correlation techniques are frequently...  相似文献   
108.
This paper reports the fabrication of vertically oriented BiFeO3 (BFO) nanorods on indium tin oxide/glass substrates through hydrothermal synthesis. Further, their piezotronic, piezophototronic, and piezophotocatalytic properties were analyzed. Various synthesis parameters were examined to modulate the morphology and alignment of BFO nanorods, including the ratios of precursors, the pH values, types of complex agents, and reaction times and temperatures. Transmission electron microscopy results demonstrated single crystallinity of the BFO nanorods. A band gap of approximately 2.3?eV was determined. The piezotronic and piezophototronic properties were observed through facile current–voltage measurement. The extended application of piezophotocatalysis under alternating external stress and visible-light irradiation, to decompose methylene blue solutions, was also ascertained. The piezophotocatalytic efficiency was improved by approximately 30% over photocatalysis in the first 30?min. Both O2?□and□·OH radicals were crucial for these activities.  相似文献   
109.
The combustion characteristics of methanol‐gasoline blends pool fires were studied in a series of full‐scale tunnel experiments conducted with different methanol and gasoline blends. The parameters were measured including the mass loss rate, the pool surface temperature, the fire plume centerline temperature, the ceiling temperature, the smoke layer temperature profile, the flame height, and the smoke layer interface height. The gasoline components were analyzed by GC‐MS. The effects of azeotropism on the combustion characteristics of the different blends were discussed. On the basis of the results of the fire plume centerline temperature, the ceiling temperature, and the flame height, it shows that the tunnel fire regime gradually switches from fuel controlled to ventilation controlled with increasing gasoline fractions in the blends. The fire plume can be divided into 3 regions by the fire plume centerline temperature for the different blends. The N‐percentage rule to determine the smoke layer interface height is found to be applicable for tunnel fires with different blends for N = 26.  相似文献   
110.
At present, the major drawback for mobile phones is the issue of power consumption. As one of the alternatives to decrease the power consumption of standard, power-hungry location-based services usually require the knowledge of how individual phone features consume power. A typical phone feature is that the applications related to multimedia streaming utilize more power while receiving, processing, and displaying the multimedia contents, thus contributing to the increased power consumption. There is a growing concern that current battery modules have limited capability in fulfilling the long-term energy need for the progress on the mobile phone because of increasing power consumption during multimedia streaming processes. Considering this, in this paper, we provide an offline meaning sleep-mode method to compute the minimum power consumption comparing with the power-on solution to save power by implementing energy rate adaptation (RA) mechanism based on mobile excess energy level purpose to save battery power use. Our simulation results show that our RA method preserves efficient power while achieving better throughput compared with the mechanism without rate adaptation (WRA).  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