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   4882838篇
  免费   321045篇
  国内免费   186389篇
电工技术   264062篇
技术理论   127篇
综合类   271137篇
化学工业   711881篇
金属工艺   233816篇
机械仪表   263005篇
建筑科学   279094篇
矿业工程   117353篇
能源动力   137026篇
轻工业   401713篇
水利工程   103114篇
石油天然气   143509篇
武器工业   35921篇
无线电   520483篇
一般工业技术   590394篇
冶金工业   568464篇
原子能技术   64606篇
自动化技术   684567篇
  2023年   43004篇
  2022年   102656篇
  2021年   146582篇
  2020年   106071篇
  2019年   86419篇
  2018年   103519篇
  2017年   113721篇
  2016年   106149篇
  2015年   131059篇
  2014年   179354篇
  2013年   277774篇
  2012年   285265篇
  2011年   325183篇
  2010年   291926篇
  2009年   292183篇
  2008年   298497篇
  2007年   289874篇
  2006年   262521篇
  2005年   219173篇
  2004年   157844篇
  2003年   121551篇
  2002年   113675篇
  2001年   104217篇
  2000年   100253篇
  1999年   82028篇
  1998年   142888篇
  1997年   100812篇
  1996年   85451篇
  1995年   66937篇
  1994年   58169篇
  1993年   49968篇
  1992年   33298篇
  1991年   30036篇
  1990年   29875篇
  1989年   28939篇
  1988年   26810篇
  1987年   24396篇
  1986年   23709篇
  1985年   25501篇
  1984年   22109篇
  1983年   20309篇
  1982年   19187篇
  1981年   19547篇
  1980年   18771篇
  1979年   16821篇
  1978年   16239篇
  1977年   22927篇
  1976年   33670篇
  1975年   14036篇
  1974年   13030篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
61.
62.
Journal of Computer and Systems Sciences International - It is shown that the Lyapunov theorem on the distribution properties of the sum of random variables with different distribution densities...  相似文献   
63.
Virtual Reality - It is generally accepted that natural environments reduce stress and improve mood. Since access to natural environments is sometimes limited, virtual natural environments,...  相似文献   
64.
Multimedia Tools and Applications - Mammograms are the images used by radiologists to diagnose breast cancer. Breast cancer is one of the most common cancers in women. The early detection of breast...  相似文献   
65.
66.
67.
68.
The β-Carotene (BC), an important precursor of vitamin A (VA), possesses antioxidant activity but is fat-soluble and has low bioavailability. In previous in-vitro assays evaluating antioxidant and 2,2′-azobis(2-amidinopropane) dihydrochloride (AAPH) free radical scavenging, both BC and VA showed a strong ability to scavenge radicals and protected cells from oxidative stress. Here, we used artificially simulated gastrointestinal digestion and Caco-2 cell absorption models to evaluate the bioavailability of the BC during gastrointestinal digestion and absorption using high-performance liquid chromatography (HPLC) analysis. We observed high absorptive and transfer rates of BC and detected retinol metabolites (Vitamin A). Therefore, BC can be detected in the acidic gastrointestinal environment using HPLC. Optimised method provided better separation of BC and VA in the column, improving the accuracy of the test results.  相似文献   
69.
The effect of microwave roasting parameters (300, 450 and 600 W; 5, 10 and 15 min) on acrylamide content in sorghum grain was determined using High Pressure Liquid Chromatography (HPLC)-photo diode array (PDA) detector coupled with C-18 column. Samples roasted at 300 and 450 W did not possess acrylamide, whereas 600 W (15 min) favoured formation of 2740.19 µg/kg of acrylamide, levels far exceeding the defined European Union (EU) limits. The chronic daily intake (CDI) for acrylamide through consumption of such grain flour was 3.25–9.5-fold higher to Joint FAO/WHO Expert Committee on Food Additives (JECFA) defined high exposure limits. The margin of exposure (MOE) values ranged from 4.3 to 12.76 and from 11.07 to 32.27 for neoplastic and neurological effects, respectively, demonstrating high exposure and serious health concerns associated with dietary intake of this toxicant. This study assesses the risk for the Indian population and highlights the importance of optimising process parameters for food product to minimise such exposure risks.  相似文献   
70.
The effects of cellulose microfibres (CMFs, Average size: 100 ± 5 μm) and cellulose nanofibres (CNFs, Average size: 60 ± 3 nm) on the properties of myofibrillar protein (MP) gels from duck breast meat were studied. The results demonstrated that CMFs and CNFs were mostly connected to MP by non-covalent bonds, the diffusion and cross-linking of MP molecules was promoted, and a denser and more complete gel network was formed. With the increases of CMFs and CNFs concentration (0–10%), the hardness was increased by 13.15% and 19.78% for CMFs10% and CNFs10% gels, respectively, and the elasticity was increased by 40% and 80%, respectively. At the same concentration (0–10%), the increase in gel hardness, viscoelasticity and immobilised water content was greater in the CNFs-MP group than in the CMFs-MP group. The CNFs-MP group had a tighter gel network, and CNFs had a better potential to improve the gelation performance of MP.  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