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   83701篇
  免费   4966篇
  国内免费   7849篇
电工技术   5653篇
技术理论   3篇
综合类   8458篇
化学工业   10343篇
金属工艺   8730篇
机械仪表   5833篇
建筑科学   5771篇
矿业工程   2095篇
能源动力   2243篇
轻工业   4801篇
水利工程   1769篇
石油天然气   6955篇
武器工业   689篇
无线电   9094篇
一般工业技术   8038篇
冶金工业   3190篇
原子能技术   2142篇
自动化技术   10709篇
  2024年   79篇
  2023年   656篇
  2022年   1043篇
  2021年   1618篇
  2020年   1288篇
  2019年   1115篇
  2018年   1231篇
  2017年   1475篇
  2016年   1294篇
  2015年   1640篇
  2014年   2514篇
  2013年   2872篇
  2012年   3319篇
  2011年   7373篇
  2010年   4679篇
  2009年   3574篇
  2008年   3675篇
  2007年   3236篇
  2006年   3661篇
  2005年   3434篇
  2004年   6827篇
  2003年   4751篇
  2002年   4987篇
  2001年   3640篇
  2000年   2503篇
  1999年   3543篇
  1998年   2554篇
  1997年   2364篇
  1996年   1657篇
  1995年   1368篇
  1994年   1157篇
  1993年   2783篇
  1992年   2173篇
  1991年   1523篇
  1990年   1391篇
  1989年   1114篇
  1988年   738篇
  1987年   419篇
  1986年   282篇
  1985年   171篇
  1984年   117篇
  1983年   73篇
  1982年   72篇
  1981年   52篇
  1980年   98篇
  1979年   72篇
  1965年   64篇
  1959年   28篇
  1958年   27篇
  1957年   33篇
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
1.
2.
Wu  Zheng  Meng  Xuan  Shi  Li  Liu  Naiwang 《Journal of Porous Materials》2022,29(2):493-500
Journal of Porous Materials - In this work, a trifluoromethanesulfonic acid (TFOH) modified clay (TFOH-Clay) was developed for the removal of trace olefins in heavy naphtha. 5%TFOH-Clay can...  相似文献   
3.
Lu  Huaiqian  Shi  Hui  Xie  Qilong  Li  Li  Xiao  Yong  Jia  Litao  Li  Debao 《Catalysis Letters》2022,152(11):3347-3353
Catalysis Letters - This study proposed a new facile route to rational creating oxygen-vacancy (Vo)-rich surface of Co3O4 nanosheets by acetic acid leaching. The acid leached Co3O4 nanosheets was...  相似文献   
4.
5.
6.
Corrosion and wear failures are bottlenecks for restricting applications and developments of Al-based functional materials. As a new lubrication technology, superhydrophobic preparation provides an effective way to settle Al alloy corrosion. The preparation methods of superhydrophobic Al alloys are mainly multistep strategies. In this study, superhydrophobic Al alloy, has been prepared by an efficient one-step electrochemical etching process. Meanwhile, its micromorphology has been observed by a scanning electron microscope. The wettability has been measured by video optical contact angle meter. The corrosion behavior has been tested by electrochemical workstation, and wear performance has been characterized by friction tester. The results show that the micro-nanoterraced concave–convex structure has been fabricated and an as-prepared surface exhibits excellent superhydrophobic behavior. Further electrochemical and tribological tests show that corrosion resistance and wear resistance have also been significantly improved. This study provides a new method to prepare wear-resistant and corrosion-resistant Al alloy for widening applications of multifunctional Al-based engineering materials.  相似文献   
7.
Phosphors-converted LEDs (pc-LEDs) are excellent artificial light sources for indoor plant cultivation, in which the far-red-emitting component (700−780 nm) plays an important role in regulating the photomorphogenesis of plants. Accordingly, highly efficient and thermally stable far-red-emitting phosphors are indispensable for developing high-performance plant cultivation pc-LEDs. Herein, far-red-emitting YAl3(BO3)4:Cr3+ (YAB:Cr3+) phosphors were synthesized by solid-state reaction, and their photoluminescence characteristics, thermal quenching, quantum yield (QY), and application in pc-LEDs were systematically investigated. The YAB:Cr3+ phosphor has an intense broadband absorption to the blue light, simultaneously exhibiting the sharp-line 2E emission and the broadband T2 emission of Cr3+ with a QY of ~86.7%. The far-red broadband emissions of YAB:Cr3+ centered at ~735 nm show a high resemblance to the active-state (PFR) absorption of plant phytochrome. Moreover, the YAB:Cr3+ phosphor shows the thermally enhanced luminescence at temperatures of 303−393 K and the near-zero thermal quenching up to 423 K. The anomalous thermal enhancement is attributed to the temperature-dependent repopulation between 2E and T2 states. Finally, a pc-LED device was fabricated with the YAB:Cr3+ phosphor and blue chip, exhibiting the light out power of ~50.6 mW and energy conversion efficiency of ~17.4% at 100 mA drive current, respectively. The exceptional PL features including suitable excitation/emission wavelengths, suppressed thermal quenching and high QY make YAB:Cr3+ phosphors very promising for applications in plant growth pc-LEDs.  相似文献   
8.
Radicals are closely related to human life and health and have been widely used in biology, chemistry, functional materials, etc. However, the high reactivity, disorder, and short half-lives limit their wide applications. Therefore, it remains a great challenge to prepare stable and ordered radicals. Herein, radicals are prepared with protective umbrellas (diethylmethyleneamine, DEMA) that are integrated on the surface of 2D layered materials to isolate water and oxygen and enhance the stability of radicals. Taking 2D black phosphorus (BP) as an example: triethylamine reacts with dichloromethane to form quaternary ammonium salts with further Hoffmann elimination to produce DEMA radicals that could react with one electron of a lone pair electrons in P on the surface of BP to produce P radicals, which shows a prolonged half-life of 21 days at room temperature. First-principle calculations and electron paramagnetic resonance fitting confirm that the steric hindrance constructed by dense DEMA passivation layer acts as a protective umbrella and the 2D coupling of P radicals and other P atoms in 2D BP plane to enhance the stability and strong superexchange interaction of P radicals. Furthermore, it is a general strategy to produce stable radicals integrated on the 2D plane.  相似文献   
9.
10.
Flexible scintillating fiber plays an important role in X-ray radiation monitoring and high-resolution medical imaging, while construction of scintillating fiber derived from the commercial material system meet with limited success. Here, we report the design and successful fabrication of the Ce-activated lutetium aluminum silicate glass, nanostructured glass, and fiber, and explore their scintillating properties. The scintillating glass with optimized composition and optical properties is determined. The crystallization behavior of lutetium aluminum silicate glass is studied and the nanostructured glass embedded with orthorhombic Lu2Si2O7 phase is successfully constructed for the first time. Importantly, the crystalline layer thickness of the nanostructured glass can be finely tuned and ~172.89% enhancement in the scintillating performance can be achieved. Furthermore, the fiber with large sized core is fabricated and its radiation response properties are tested. The results show that it exhibits high sensitivity and its scintillating emission is lineally dependent on the X-ray power, indicating the potential application for radiation detection.  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