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   2400篇
  免费   130篇
  国内免费   5篇
电工技术   25篇
综合类   5篇
化学工业   469篇
金属工艺   50篇
机械仪表   52篇
建筑科学   126篇
矿业工程   4篇
能源动力   94篇
轻工业   223篇
水利工程   13篇
石油天然气   3篇
无线电   225篇
一般工业技术   480篇
冶金工业   314篇
原子能技术   18篇
自动化技术   434篇
  2023年   21篇
  2022年   34篇
  2021年   59篇
  2020年   37篇
  2019年   53篇
  2018年   56篇
  2017年   54篇
  2016年   49篇
  2015年   71篇
  2014年   103篇
  2013年   131篇
  2012年   110篇
  2011年   166篇
  2010年   145篇
  2009年   121篇
  2008年   135篇
  2007年   137篇
  2006年   119篇
  2005年   91篇
  2004年   72篇
  2003年   85篇
  2002年   78篇
  2001年   37篇
  2000年   42篇
  1999年   47篇
  1998年   68篇
  1997年   56篇
  1996年   47篇
  1995年   34篇
  1994年   38篇
  1993年   48篇
  1992年   17篇
  1991年   21篇
  1990年   13篇
  1989年   13篇
  1988年   11篇
  1987年   8篇
  1986年   17篇
  1985年   13篇
  1984年   5篇
  1983年   3篇
  1982年   8篇
  1980年   6篇
  1979年   3篇
  1978年   8篇
  1977年   5篇
  1976年   17篇
  1975年   5篇
  1973年   3篇
  1965年   2篇
排序方式: 共有2535条查询结果,搜索用时 15 毫秒
1.
Several studies have reported that nicotine, the main bioactive component of tobacco, exerts a marked negative energy balance. Apart from its anorectic action, nicotine also modulates energy expenditure, by regulating brown adipose tissue (BAT) thermogenesis and white adipose tissue (WAT) browning. These effects are mainly controlled at the central level by modulation of hypothalamic neuropeptide systems and energy sensors, such as AMP-activated protein kinase (AMPK). In this study, we aimed to investigate the kappa opioid receptor (κOR)/dynorphin signaling in the modulation of nicotine’s effects on energy balance. We found that body weight loss after nicotine treatment is associated with a down-regulation of the κOR endogenous ligand dynorphin precursor and with a marked reduction in κOR signaling and the p70 S6 kinase/ribosomal protein S6 (S6K/rpS6) pathway in the lateral hypothalamic area (LHA). The inhibition of these pathways by nicotine was completely blunted in κOR deficient mice, after central pharmacological blockade of κOR, and in rodents where κOR was genetically knocked down specifically in the LHA. Moreover, κOR-mediated nicotine effects on body weight do not depend on orexin. These data unravel a new central regulatory pathway modulating nicotine’s effects on energy balance.  相似文献   
2.
There are many potential causes of corrosion in animal buildings. Animals exhale large quantities of moisture into the air creating high relative humidity in the building if the moisture is not properly vented. High humidity increases the potential for condensation. In addition, ammonia may be found in large quantities in animal buildings. Ammonia is released from manure and urine. In addition, ammonium chloride is used as a nitrogen source in fertilisers. In this study, the atmospheric corrosion of hot-dip-galvanised steel and zinc alloy-coated steel such as zinc–aluminium and zinc–aluminium–magnesium has been studied in atmospheres containing different levels of ammonia. Investigations have also been conducted at different levels of ammonium chloride. The results are discussed in view of the mechanisms of corrosion of zinc and zinc alloy-coated steel in ammonia and ammonium chloride-containing environments.  相似文献   
3.
The demands for welding of thick-walled pressure vessels are very stringent. The cost of repairing a weld defect deep down in a weld joint could be very high. As submerged arc welding is considered to be a reliable process for both the welding of pressure vessels and other demanding applications, ESAB chose this process when developing their narrow gap welding technique. This two-pass narrow gap process is described together with the welding and control equipment. The welding results using two types of agglomerated fluxes are presented.  相似文献   
4.
Summary Dynamic light scattering was used to investigate the dynamics of sodium poly(styrene sulfonate) and fully neutralized poly(acrylic acid) gels as a function of the degree of swelling and weight ratio of cross-linking agent. It was shown that the collective diffusion coefficient increases with increasing degree of swelling and that the diffusion coefficient shows stronger concentration dependence than predicted by scaling arguments. For gel samples measured at the swelling equilibrium, the diffusion coefficient increases with increasing gel concentration for both gel systems.  相似文献   
5.
A Discfilter with 10 and 18 microm filter openings, respectively, was placed in parallel to a flotation plant for separation of biological flocs from a post-denitrifying Kaldnes Moving Bed Process, the last treatment step at the municipal wastewater treatment plant at Sj?unda, Malm?, Sweden. The effluent concentrations from the 10 and 18 microm filter were 2-5 and 2-8 mg SS L(-1), respectively, which is comparable to, or better than, the flotation plant. Comparison with experiences from activated sludge plants shows that the Discfilter works especially well after the Kaldnes process. Particle size distribution (PSD) studies show that particles larger than the filter openings of 10 and 18 microm are separated with approximately 90% efficiency, whereas most of the smaller particles pass the filter. This fact indicates that the major particle separation mechanism is physical blocking. These findings point to the possibility of improving the prediction of the separation efficiency by combining measurements of turbidity and suspended solids with particle size analysis.  相似文献   
6.
7.
8.
In many applications electronic sensors are used toimprove performance and reliability of measurement systems. Suchsensors should provide a correct transfer from the physical signalto be measured to the electrical output signal. One importantstep to achieve this, is to calibrate each sensor by applyingdifferent reference input signals and adjusting the sensor transferaccordingly. Besides expensive reference equipment the calibrationprocess takes much time and attention per individual sensor,which means a considerable increase in sensor production costs.By including at the sensor or sensor interface chip a programmablecalibration facility the calibration of such smart sensors caneasily be automated and can be executed for a batch of sensorsat a time, thus minimizing the calibration time and costs. Thispaper presents a calibration method and options for integrationin the smart sensor concept, in hardware as well as in software.An advantage of the proposed method is that it does not needa large matrix of calibration data, which needs to be storedin a look-up table or converted into a correction formula, butinstead it uses a step-by-step approach to correct the sensortransfer at each calibration measurement until the error is sufficientlysmall.  相似文献   
9.
10.
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