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   2041篇
  免费   70篇
  国内免费   6篇
电工技术   52篇
综合类   9篇
化学工业   532篇
金属工艺   39篇
机械仪表   65篇
建筑科学   51篇
矿业工程   7篇
能源动力   55篇
轻工业   244篇
水利工程   19篇
石油天然气   4篇
无线电   136篇
一般工业技术   314篇
冶金工业   206篇
原子能技术   40篇
自动化技术   344篇
  2022年   16篇
  2021年   45篇
  2020年   21篇
  2019年   26篇
  2018年   28篇
  2017年   42篇
  2016年   65篇
  2015年   44篇
  2014年   58篇
  2013年   116篇
  2012年   98篇
  2011年   110篇
  2010年   81篇
  2009年   102篇
  2008年   90篇
  2007年   80篇
  2006年   59篇
  2005年   55篇
  2004年   57篇
  2003年   50篇
  2002年   57篇
  2001年   43篇
  2000年   37篇
  1999年   32篇
  1998年   38篇
  1997年   38篇
  1996年   28篇
  1995年   25篇
  1994年   25篇
  1993年   30篇
  1992年   25篇
  1991年   18篇
  1990年   17篇
  1989年   18篇
  1988年   13篇
  1987年   19篇
  1986年   13篇
  1985年   22篇
  1984年   20篇
  1983年   27篇
  1982年   12篇
  1981年   18篇
  1980年   19篇
  1979年   28篇
  1978年   21篇
  1977年   16篇
  1975年   16篇
  1974年   24篇
  1973年   12篇
  1971年   11篇
排序方式: 共有2117条查询结果,搜索用时 609 毫秒
61.
Journal of Materials Science: Materials in Electronics - Zinc oxide (ZnO) rods film was fabricated by homemade and simple spray pyrolysis technique on a p-type silicon (Si) substrate, and the film...  相似文献   
62.
63.
64.
Nisin is a natural preservative for many food products. This bacteriocin is mainly used in dairy and meat products. Nisin inhibits pathogenic food borne bacteria such as Listeria monocytogenes and many other Gram-positive food spoilage microorganisms. Nisin can be used alone or in combination with other preservatives or also with several physical treatments. This paper reviews physicochemical and biological properties of nisin, the main factors affecting its antimicrobial effectiveness, and its food applications as an additive directly incorporated into food matrices.  相似文献   
65.
ABSTRACT

Wind turbine control is an important task to make the electricity generation secure in terms of energy demand and machine safety. It also yields to control the desired power level and optimized energy because of the assignment of turbine speed. The contactless piezoelectric wind energy harvester (CPWEH) used in this study has three piezoelectric layers located around the shaft with 120 degrees apart and they are buckled by the magnetic force without any physical contact. The superiority of this device is to generate energy for low wind speeds such as 1.5 m/s. However, for high speeds, high total harmonic distortions (THDs) govern the waveforms, thus controlling the turbine speed becomes necessary for optimizing the output power. Encouraged by this, a small low inertia dc generator is coupled with the wind turbine, and the generator terminals are connected to a resistor through a power switch to generate a braking torque that opposes to wind speed direction. By controlling the switch properly, turbine speed is ensured to remain within a certain band, which accordingly prevents the turbine from rotating very fast at damaging wind speeds. Several experiments are performed on the developed CPWEH with/without the presented control scheme which prove the existence of promising performance of our proposal.  相似文献   
66.
Mass detection is a very important process for breast cancer diagnosis and computer aided systems. It can be very complex when the mass is small or invisible because of dense breast tissue. Therefore, the extraction of suspicious mass region can be very challenging. This paper proposes a novel segmentation algorithm to identify mass candidate regions in mammograms. The proposed system includes three parts: breast region and pectoral muscle segmentation, image enhancement and suspicious mass regions identification. The first two parts have been examined in previous studies. In this study, we focused on suspicious mass regions identification using a combination of Havrda & Charvat entropy method and Otsu's N thresholding method. An open access Mammographic Image Analysis Society (MIAS) database, which contains 59 masses, was used for the study. The proposed system obtained a 93% sensitivity rate for suspicious mass regions identification in 56 abnormal and 40 normal images.  相似文献   
67.
In spite of its great importance for the dry classification of fine powders, the processes in deflector wheel classifiers are to a large extent unknown. Therefore, in the present work a commercial available classifier was modified to gain an optical access to the deflector wheel. For the first time, the obtained photographs enable an observation of the gas flow and the particle motion between the blades of the deflector wheel. Especially the importance of particle‐particle‐ and particle‐blade‐collisions could be shown.  相似文献   
68.
69.
This paper proposed a method, namely resistively loaded lines (RLL), to compensate the effects of the DC bias lines after investigating its effects on several types of antennas for terahertz photomixers. The RLL is formed by placing lumped resistances periodically on the DC bias line in order to cease the leakage current virtually, which cause a significant amount of distortion on the antenna performance. The simulation results of the dipole, folded dipole, log-periodic, and spiral antennas show that RLL almost removes the effects of the bias lines and improves the antenna radiation resistance and radiation pattern notably compared with that of the commonly used bias line types, such as coplanar stripline and photonic bandgap type bias lines.  相似文献   
70.
Oil from the marine copepod, Calanus finmarchicus, which contains >86 % of fatty acids present as wax esters, is a novel source of n‐3 fatty acids for human consumption. In a randomized, two‐period crossover study, 18 healthy adults consumed 8 capsules providing 4 g of Calanus® Oil supplying a total of 260 mg EPA and 156 mg DHA primarily as wax esters, or 1 capsule of Lovaza® providing 465 mg EPA and 375 mg DHA as ethyl esters, each with an EPA‐ and DHA‐free breakfast. Plasma EPA and DHA were measured over a 72 h period (t = 1, 2, 4, 6, 8, 10, 12, 24, 48, and 72 h). The positive incremental area under the curve over the 72 h test period (iAUC0‐72 h) for both EPA and DHA was significantly different from zero (p < 0.0001) in both test conditions, with similar findings for the iAUC0–24 h and iAUC0–48 h, indicating the fatty acids were absorbed. There was no difference in the plasma iAUC0–72 h for EPA + DHA, or DHA individually, in response to Calanus Oil vs the ethyl ester condition; however, the iAUC0–48 h and iAUC0–72 h for plasma EPA in response to Calanus Oil were both significantly increased relative to the ethyl ester condition (iAUC0–48 h: 381 ± 31 vs 259 ± 39 μg*h/mL, p = 0.026; iAUC0‐72 h: 514 ± 47 vs 313 ± 49 μg*h/mL, p = 0.009). These data demonstrate a novel wax ester rich marine oil is a suitable alternative source of EPA and DHA for human consumption.  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