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   60431篇
  免费   6182篇
  国内免费   3102篇
电工技术   3938篇
技术理论   7篇
综合类   4669篇
化学工业   9821篇
金属工艺   3399篇
机械仪表   3951篇
建筑科学   4990篇
矿业工程   1825篇
能源动力   1936篇
轻工业   4539篇
水利工程   1243篇
石油天然气   3009篇
武器工业   632篇
无线电   7100篇
一般工业技术   7012篇
冶金工业   2506篇
原子能技术   718篇
自动化技术   8420篇
  2024年   138篇
  2023年   1139篇
  2022年   1918篇
  2021年   2788篇
  2020年   2101篇
  2019年   1758篇
  2018年   1951篇
  2017年   2159篇
  2016年   1846篇
  2015年   2643篇
  2014年   3257篇
  2013年   3808篇
  2012年   4326篇
  2011年   4322篇
  2010年   4153篇
  2009年   3900篇
  2008年   3728篇
  2007年   3341篇
  2006年   3350篇
  2005年   2652篇
  2004年   1894篇
  2003年   1583篇
  2002年   1685篇
  2001年   1460篇
  2000年   1259篇
  1999年   1288篇
  1998年   971篇
  1997年   822篇
  1996年   758篇
  1995年   589篇
  1994年   539篇
  1993年   355篇
  1992年   320篇
  1991年   230篇
  1990年   168篇
  1989年   142篇
  1988年   97篇
  1987年   62篇
  1986年   56篇
  1985年   32篇
  1984年   23篇
  1983年   22篇
  1982年   21篇
  1981年   14篇
  1980年   21篇
  1979年   7篇
  1974年   2篇
  1970年   2篇
  1959年   3篇
  1951年   7篇
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
1.
Niu  Hao  Yang  Dan-Lei  Pu  Yuan  Wang  Dan  Wang  Jie-Xin 《Journal of Materials Science》2022,57(10):5788-5804
Journal of Materials Science - Nanocomposites have been used in various industries due to their excellent properties. For some of them, high filler content (over 50 wt%) is beneficial to improving...  相似文献   
2.
3.
Zhang  Qi  Wang  Yujing  Zhang  Xueling  Song  Jun  Li  Yinlei  Wu  Xuehong  Yuan  Kunjie 《Journal of Materials Science》2022,57(14):7208-7224
Journal of Materials Science - Form-stable composite phase change materials (C-PCMs) prepared by microencapsulation method and porous matrix adsorption method need for compression molding after...  相似文献   
4.
The aim of this study was to determine the effects of tumbling at different post-mortem times on the proteolytic features and quality attributes of beef loins (M. longissimus lumborum). Loins (n = 12) were cut into 4 sections and assigned to tumbling at 1, 6 or 11 days post-mortem or non-tumbled control. Upon tumbling, additional ageing was applied to a common post-mortem time of 16 days. In general, tumbling had no considerable impacts on water-holding ability of samples. Tumbling resulted in an immediate decrease in shear force values (WBSF) of beef samples. Tumbling at 1 day post-mortem with no ageing had similar WBSF compared to the non-tumbled controls at 16 days (P > 0.05). With ageing, tumbling increased amounts of protein degradation, myofibrillar fragmentation and calpain-1 autolysis of samples. These results suggest that early post-mortem tumbling coupled with ageing can synergistically impact the tenderness development of beef loins and shorten the necessary ageing period.  相似文献   
5.
6.
The present study aimed to evaluate the effect of fermentation and gastrointestinal digestion of three kinds of fermented kiwifruit pulps with different Lactobacillus (Lactobacillus plantarum, Lactobacillus acidophilus and Lactobacillus casei). The changes in bioactive substances (total phenolic acid, total flavonoid, vitamin C and the viable count), antioxidant capacity (DPPH, ABTS, hydroxyl radical and superoxide anion radical scavenging activity) and phenolic profiles (protocatechuic acid, protocatechualdehyde, chlorogenic acid, caffeic acid and p-coumaric acid) were detected. The result showed, compared to non-fermented kiwifruit pulp, fermentation with LP and LA had higher content of TPA, TF and VC, as well as antioxidant capacity. Fermentation with LP and the content of protocatechualdehyde, p-coumaric acid and chlorogenic acid were increased. However, after digestion, LP showed more effect in maintaining the content of antioxidants, antioxidant capacity and the viable count rather than LA. During digestion, the content of protocatechualdehyde and p-coumaric acid was increased in fermented samples compared with non-fermented samples. Overall, compared with LA and LC, LP is more suitable for the fermentation of kiwifruit pulp.  相似文献   
7.
Solar steam generation has attracted considerable interest due to its easy accessibility and sustainability. However, dye molecules were gradually concentrated on bulk water or the surface of solar absorbers during the disposal of dye wastewater. Herein, LaB6/g-C3N4 composites were immobilized on porous cotton cloth, served as a solar absorber resistant to dye clogging. The optimal solar absorber possessed solar harvesting of 92.3% and showed great application potential in the field of the treatment of dye wastewater. This study presented a new approach for the treatment of dye wastewater.  相似文献   
8.
本文通过对国内外石油及石化产品分析检测相关标准技术的调研与收集,以及相关检测仪器特点的分析,对目前包括润滑油、汽油、柴油、煤油、石蜡、石化聚合物、原油等样品类型,共计80个样品在现有仪器上进行测试,使用标准方法对样品中碳、氢、氮、硫元素进行检测,获取样品的检测时间、含量结果、仪器条件等参数,为相关仪器检测提供数据基础.  相似文献   
9.
10.
LiFePO4 modified by N-doped graphene (NG) with a three-dimensional conductive network structure was synthesized via a one-step in situ hydrothermal method. The effects of N amount of NG on the phase structure, morphology, and electrochemical properties of LiFePO4 are investigated in this study. X-ray diffraction (XRD) results show that doping suitable N amounts in NG do not alter the crystal structure of LiFePO4, and scanning electron microscopy (SEM) images show that NG can slightly reduce the particle size of LiFePO4. The high-resolution transmission electron microscopy (HRTEM) results show that the LiFePO4 particles are well covered and connected by NG. The electrochemical performance confirms that LiFePO4 modified by 20% N-doped graphene (named LFP/NG-4) displays a perfect specific capacity of 166.6 mAh·g?1 at a rate of 0.2C and can reach 125 mAh·g?1 at a rate of 5 C. Electrochemical impedance spectroscopy (EIS) results illustrate that the charge transfer resistance value of the LFP/NG-4 composite is only 58.6 Ω, which is very low compared with LiFePO4. Cyclic voltammetry (CV) tests indicate that the addition of 20% N-doped graphene can effectively reduce electrode polarization and improve reversibility. The LFP/NG-4 composite with a three-dimensional conductive network structure can be regarded as a promising cathode material for Li-ion batteries.  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