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   502402篇
  免费   8188篇
  国内免费   2006篇
电工技术   9032篇
综合类   843篇
化学工业   71488篇
金属工艺   19572篇
机械仪表   15436篇
建筑科学   11783篇
矿业工程   2505篇
能源动力   12465篇
轻工业   44440篇
水利工程   5302篇
石油天然气   9020篇
武器工业   108篇
无线电   61446篇
一般工业技术   98668篇
冶金工业   93683篇
原子能技术   11551篇
自动化技术   45254篇
  2021年   4204篇
  2020年   3438篇
  2019年   4296篇
  2018年   7333篇
  2017年   7426篇
  2016年   7837篇
  2015年   5177篇
  2014年   8414篇
  2013年   22967篇
  2012年   13618篇
  2011年   18103篇
  2010年   14165篇
  2009年   15926篇
  2008年   16932篇
  2007年   16810篇
  2006年   14640篇
  2005年   13410篇
  2004年   13113篇
  2003年   12623篇
  2002年   11714篇
  2001年   11574篇
  2000年   10769篇
  1999年   11389篇
  1998年   28546篇
  1997年   20249篇
  1996年   15435篇
  1995年   12291篇
  1994年   10803篇
  1993年   10740篇
  1992年   8136篇
  1991年   7605篇
  1990年   7360篇
  1989年   7122篇
  1988年   6704篇
  1987年   5952篇
  1986年   5914篇
  1985年   6742篇
  1984年   6253篇
  1983年   5683篇
  1982年   5413篇
  1981年   5476篇
  1980年   5359篇
  1979年   5040篇
  1978年   4953篇
  1977年   5689篇
  1976年   7292篇
  1975年   4371篇
  1974年   4284篇
  1973年   4350篇
  1972年   3564篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
1.
Non-alcoholic fatty liver disease (NAFLD) is considered the most common liver disorder, affecting around 25% of the population worldwide. It is a complex disease spectrum, closely linked with other conditions such as obesity, insulin resistance, type 2 diabetes mellitus, and metabolic syndrome, which may increase liver-related mortality. In light of this, numerous efforts have been carried out in recent years in order to clarify its pathogenesis and create new prevention strategies. Currently, the essential role of environmental pollutants in NAFLD development is recognized. Particularly, endocrine-disrupting chemicals (EDCs) have a notable influence. EDCs can be classified as natural (phytoestrogens, genistein, and coumestrol) or synthetic, and the latter ones can be further subdivided into industrial (dioxins, polychlorinated biphenyls, and alkylphenols), agricultural (pesticides, insecticides, herbicides, and fungicides), residential (phthalates, polybrominated biphenyls, and bisphenol A), and pharmaceutical (parabens). Several experimental models have proposed a mechanism involving this group of substances with the disruption of hepatic metabolism, which promotes NAFLD. These include an imbalance between lipid influx/efflux in the liver, mitochondrial dysfunction, liver inflammation, and epigenetic reprogramming. It can be concluded that exposure to EDCs might play a crucial role in NAFLD initiation and evolution. However, further investigations supporting these effects in humans are required.  相似文献   
2.
3.
Protection of Metals and Physical Chemistry of Surfaces - The present review is devoted to the sorption properties of magnetite towards hexavalent chromium ions and the possibility of its use as a...  相似文献   
4.
5.
Catalysis Letters - We converted agro-waste Custard Apple Peels (CAP) to ash via thermal treatment, on which Pd(OAc)2 was immobilized easily that produced a low-cost, highly efficient Pd/CAP-ash...  相似文献   
6.
7.
Metal organic frameworks (MOFs) containing zirconium secondary building units (SBUs) in UiO-67 and related MOFs, are highly active for neutralizing both the chemical warfare agents and simulants, such as dimethyl methylphosphonate (DMMP). However, two recent publications gave conflicting reports of DMMP reaction with UiO-67 under ultra high vacuum (UHV) conditions, with one reporting chemisorption and reaction (Wang et al., J Phys Chem C, 2017, 121, 11261–11272) and the other reporting only physisorption and reversible desorption (Ruffley et al., J Phys Chem C, 2019, 123, 19748–19758) from very similar temperature programmed desorption experiments. We show that the discrepancy between these experiments may be explained by different levels of missing linker defects in the UiO-67 samples. We present density functional theory calculations showing that SBU sites having two-adjacent missing linkers exhibit reaction barriers that are about 30 kJ/mol lower than SBU sites having a single missing linker. We also show that topology of the undercoordinated sites plays an important role in the reaction barrier under UHV conditions.  相似文献   
8.
Protection of Metals and Physical Chemistry of Surfaces - Impedance spectroscopy was used to study the adsorption of the IFKhAN-92 inhibitor, a triazole derivative, on cathodically polarized...  相似文献   
9.
Amides from indole-3-glyoxylic acid and 4-benzoyl-2-methylpiperazine, which are related to entry inhibitors developed by Bristol-Myers Squibb (BMS), have been synthesized with aliphatic chains located at the C7 position of the indole ring. These spacers contain an azido group suitable for the well-known Cu(I)-catalyzed (3+2)-cycloaddition or an activated triple bond for the nucleophilic addition of thiols under physiological conditions. Reaction with polyols (β-cyclodextrin and hyperbranched polyglycerol) decorated with complementary click partners has afforded polyol-BMS-like conjugates that are not cytotoxic (TZM.bl cells) and retain the activity against R5-HIV-1NLAD8 isolates. Thus, potential vaginal microbicides based on entry inhibitors, which can be called of 4th generation, are reported here for the first time.  相似文献   
10.
Bioactive ceramic scaffolds for bone regeneration consisting of a three-dimensional mesh of interpenetrating struts with square section were fabricated via Digital Light Processing (DLP). The ability of the technique to manufacture 3D porous structures from β-tricalcium phosphate (β-TCP) powders with different dimensions of struts and pores was evaluated, identifying the possibilities and limitations of the manufacturing process. Small pore sizes were found to seriously complicate the elimination of excess slurry from the scaffold’s innermost pores. The effect of the strut/pore size on the mechanical performance of the scaffolds under compressive stresses was also evaluated, but no significant influence was found. Under compressive stresses, the structures resulted weaker when tested perpendicularly to the printing plane due to interlayer shear failure. Interlayer superficial grooves are proposed as potential failure-controlling defects, which could also explain the lack of a Weibull size effect on the mechanical strength of the fabricated DLP scaffolds.  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