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   2543篇
  免费   175篇
  国内免费   17篇
电工技术   45篇
综合类   6篇
化学工业   618篇
金属工艺   35篇
机械仪表   89篇
建筑科学   73篇
矿业工程   2篇
能源动力   210篇
轻工业   237篇
水利工程   18篇
石油天然气   41篇
无线电   271篇
一般工业技术   519篇
冶金工业   126篇
原子能技术   20篇
自动化技术   425篇
  2023年   86篇
  2022年   145篇
  2021年   179篇
  2020年   142篇
  2019年   148篇
  2018年   179篇
  2017年   132篇
  2016年   166篇
  2015年   101篇
  2014年   162篇
  2013年   226篇
  2012年   139篇
  2011年   129篇
  2010年   110篇
  2009年   97篇
  2008年   81篇
  2007年   59篇
  2006年   54篇
  2005年   37篇
  2004年   31篇
  2003年   34篇
  2002年   30篇
  2001年   22篇
  2000年   12篇
  1999年   15篇
  1998年   42篇
  1997年   12篇
  1996年   28篇
  1995年   18篇
  1994年   18篇
  1993年   19篇
  1992年   7篇
  1991年   8篇
  1990年   5篇
  1988年   6篇
  1987年   6篇
  1986年   8篇
  1985年   5篇
  1984年   8篇
  1983年   5篇
  1982年   2篇
  1981年   2篇
  1980年   2篇
  1979年   5篇
  1978年   2篇
  1977年   2篇
  1976年   2篇
  1974年   1篇
  1973年   1篇
  1959年   4篇
排序方式: 共有2735条查询结果,搜索用时 31 毫秒
1.
In this study, we prepared a novel series of diester-functionalized cationic gemini surfactants (Cm-E2O2-Cm) containing ethylene oxide as a spacer with varying alkyl chain lengths and characterized by 1H NMR, FT-IR, elemental analysis, and ESI-MS. The physicochemical properties of the geminis were explored by tensiometry, fluorescence, dye solubilization, and Krafft point. These geminis acquire superior surface activity than the conventional surfactants. Fluorescence spectroscopy analysis affirmed that the micropolarity and aggregation number of micelles diminished with increase in the alkyl chain length. These geminis represent a new group of amphiphiles of considerably high biodegradability, better cleavability, and low toxicity as assessed by BOD test, FT-IR analysis, and HC50 analysis, respectively. They also showed significant level of antimicrobial activity toward some specified bacterial strains of Gram-positive and Gram-negative by using agar well diffusion method. Furthermore, the thermogravimetric analysis provided information regarding thermal stabilities of the newly synthesized gemini surfactants.  相似文献   
2.
Herein, we report the photosensing property of CdS thin films. CdS thin films were coated onto glass substrates via a spray pyrolysis method using different spray pressures. Prepared films were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and optical and photoluminescence spectroscopy. XRD analysis demonstrated the growth of crystalline CdS films with crystallite sizes varying from 26 to 29 nm depending on the pressure. The SEM and EDAX analyses revealed nearly-stoichiometric CdS films with smooth surfaces and slight variation in grain morphology due to pressure changes. Optical measurements showed a direct bandgap varying from 2.37 eV to 2.42 eV due to pressure changes. A photodetector was also fabricated using the grown CdS films; the fabricated photodetector exhibited good performance depending on the spray pressure. A spray pressure of 1.5 GPa resulted in high photoresponsivity and external quantum efficiency.  相似文献   
3.
Ultra-high molecular weight polyethylene (UHMWPE) is extensively used in frictional applications due to its advanced wear resistance. This advanced polymer is reinforced with hard particulate fillers for further developments against wear conditions. Since elevated temperatures prevail in the service conditions, wear behavior of UHMWPE composites is an important issue for the engineering applications. In the present work, UHMWPE-based composites including silicon carbide (SiC) fillers were fabricated in a compression molding chamber. In the specimen preparation stage, molding pressure, filler amount, and filler particle size were varied to investigate the influence of these variables. Upon deciding the optimum parameters from the wear tests conducted at room temperature, the wear experiments were repeated for the optimum specimen at elevated temperatures, such as 40 and 60°C. According to the results, the wear behavior of the SiC/UHMWPE composites is heavily changed by the effect of elevated temperature. Adhesive effect is pronounced at elevated temperatures while the wear characteristics possess the abrasive effect in the sliding path. In addition, the composites exhibit an accelerated material loss as temperature increases during the frictional system.  相似文献   
4.
This research aims to study the effect of ammonium polyphosphate and expandable graphite on the intumescent coating formulations (ICF). The coating presented in this research article is based on carbon source expandable graphite (EG), blowing agent melamine, acid source ammonium polyphosphate (APP), epoxy resin as a binder with polyamide amine. The stability of the developed coating was verified at 950°C for 1-hour fire test. The results showed that the coating is stable and well bond with the steel substrate. The char was characterized by using FESEM, XRD, FTIR, DTA, TGA, XPS, Py-GCMS and Weathering Test. The morphology of the char was studied by SEM of the coating after furnace fire test. XRD and FTIR show the presence of graphite, borophosphate; boron oxide and sassolite in the residual char. TGA and DTG disclosed that EG improved the residual mass of coating. XPS analysis showed the char residue of IF5-APP-EG contains carbon and oxygen contents 47.50 and 40.70, respectively. Py-GCMS analysis described that the IF5-APP-EG released less gaseous compounds. The weathering test illustrated that's the char expansion of coatings samples was decreased due to the presence of a humid environment and UV light. The IF5-APP-EG showed the maximum char expansion, lower substrate temperature and high residual weight among the studied formulations.  相似文献   
5.
In this study, NIMROD simulations are performed to investigate the effects of massive helium gas injection level on the induced disruption on EAST tokamak. It is demonstrated in simulations that two different scenarios of plasma cooling(complete cooling and partial cooling) take place for different amounts of injected impurities. For the impurity injection above a critical level, a single MHD activity is able to induce a complete core temperature collapse. For impurity injection below the critical level, a series of multiple minor disruptions occur before the complete thermal quench.  相似文献   
6.

A solar-blind ultraviolet photodetector based on Ti-doped Ga2O3/Si p–n heterojunction is demonstrated for the first time. It is found that the heterojunction quality forming between Ga2O3 and Si becomes better after Ti incorporation in Ga2O3. The current–voltage and temporal response measurements show that the detector based on Ti-doped Ga2O3/Si p–n heterojunction has a responsivity of 0.382 A/W and a fast rise time of 73 ms as well, which are much better than those undoped Ga2O3/Si p–n heterojunction analogues.

  相似文献   
7.
8.
Water Resources Management - Climate change will modify the spatio-temporal variation of hydrological variables worldwide, potentially leading to more extreme events and hydraulic infrastructure...  相似文献   
9.
Journal of Porous Materials - The transformation of light naphtha to value-added aromatic compounds is gaining momentum in the petrochemical industry. In this work, a series of metal modified...  相似文献   
10.
Instruments and Experimental Techniques - An Erratum to this paper has been published: https://doi.org/10.1134/S0020441221050249  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