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   1931篇
  免费   30篇
  国内免费   4篇
电工技术   40篇
化学工业   403篇
金属工艺   22篇
机械仪表   32篇
建筑科学   51篇
矿业工程   5篇
能源动力   47篇
轻工业   206篇
水利工程   22篇
石油天然气   5篇
无线电   165篇
一般工业技术   294篇
冶金工业   489篇
原子能技术   36篇
自动化技术   148篇
  2023年   8篇
  2021年   11篇
  2020年   12篇
  2019年   16篇
  2018年   25篇
  2017年   12篇
  2016年   22篇
  2015年   17篇
  2014年   32篇
  2013年   79篇
  2012年   51篇
  2011年   69篇
  2010年   58篇
  2009年   48篇
  2008年   66篇
  2007年   79篇
  2006年   57篇
  2005年   51篇
  2004年   48篇
  2003年   43篇
  2002年   43篇
  2001年   36篇
  2000年   35篇
  1999年   46篇
  1998年   150篇
  1997年   76篇
  1996年   71篇
  1995年   47篇
  1994年   40篇
  1993年   50篇
  1992年   43篇
  1991年   48篇
  1990年   22篇
  1989年   41篇
  1988年   38篇
  1987年   34篇
  1986年   31篇
  1985年   30篇
  1984年   29篇
  1983年   32篇
  1982年   26篇
  1981年   29篇
  1980年   18篇
  1979年   11篇
  1978年   14篇
  1977年   11篇
  1976年   35篇
  1974年   13篇
  1971年   8篇
  1966年   7篇
排序方式: 共有1965条查询结果,搜索用时 31 毫秒
71.
Beef longissimus dorsi muscle samples matured over a 21 day period were analysed using three different analytical techniques; 1H NMR, GC–MS and HPLC. The data from the three experimental techniques were correlated with each other to determine if the results were statistically similar to each other. From our analysis we determined that the metabolites measured using 1H NMR were statistically similar to the compounds quantified using the chromatography techniques (p < 0.001). In addition, using PCA, we were able to show that different metabolites, measured using the various analytical techniques produced very similar scores and loadings plots for all the analysis and extraction techniques undertaken across the 21 day time domain. Using a combination of these three different techniques provides a unique and holistic insight into the biochemistry behind the conversion of muscle to meat which would not be possible using any single technique alone.  相似文献   
72.
This study offers new insights into two-lift deposition of mature fine tailings under atmospheric drying. The interaction of newly added lift and former lift(s) was evaluated using column experiments in terms of volumetric water content, electrical conductivity (EC), hydraulic conductivity, geochemistry and microstructure. Water content and EC followed the same trend and decreasing of water content appears to be responsible for significant reduction in EC. Evaporation on top of the column reduced the water content to almost zero. The obtained results support the coupling between the hydraulic and chemical processes that should be considered by active operators.  相似文献   
73.
74.
75.
Macrophage apoptosis, a key process in atherogenesis, is regulated by oxidation products, including hydroxyoctadecadienoic acids (HODEs). These stable oxidation products of linoleic acid (LA) are abundant in atherosclerotic plaque and activate PPARγ and GPR132. We investigated the mechanisms through which HODEs regulate apoptosis. The effect of HODEs on THP‐1 monocytes and adherent THP‐1 cells were compared with other C18 fatty acids, LA and α‐linolenic acid (ALA). The number of cells was reduced within 24 hours following treatment with 9‐HODE (p < 0.01, 30 μM) and 13 HODE (p < 0.01, 30 μM), and the equivalent cell viability was also decreased (p < 0.001). Both 9‐HODE and 13‐HODE (but not LA or ALA) markedly increased caspase‐3/7 activity (p < 0.001) in both monocytes and adherent THP‐1 cells, with 9‐HODE the more potent. In addition, 9‐HODE and 13‐HODE both increased Annexin‐V labelling of cells (p < 0.001). There was no effect of LA, ALA, or the PPARγ agonist rosiglitazone (1μM), but the effect of HODEs was replicated with apoptosis‐inducer camptothecin (10μM). Only 9‐HODE increased DNA fragmentation. The pro‐apoptotic effect of HODEs was blocked by the caspase inhibitor DEVD‐CHO. The PPARγ antagonist T0070907 further increased apoptosis, suggestive of the PPARγ‐regulated apoptotic effects induced by 9‐HODE. The use of siRNA for GPR132 showed no evidence that the effect of HODEs was mediated through this receptor. 9‐HODE and 13‐HODE are potent—and specific—regulators of apoptosis in THP‐1 cells. Their action is PPARγ‐dependent and independent of GPR132. Further studies to identify the signalling pathways through which HODEs increase apoptosis in macrophages may reveal novel therapeutic targets for atherosclerosis.  相似文献   
76.
Metallic fuel alloys consisting of uranium, plutonium, and zirconium with minor additions of americium and neptunium are under evaluation for potential use to transmute long-lived transuranic actinide isotopes in fast reactors. The current irradiation test series design, designated AFC2, includes minor additions of rare earth elements to simulate expected fission product carry-over from the electrochemical molten salt reprocessing technique. The metal fuel alloys have been fabricated by an arc casting technique. The as-cast fuel alloys have been investigated for phase and thermal properties, specifically, enthalpies of transition, transition temperatures, and room temperature phase characteristics. Results and observations related to these characteristics for the “fresh” fuel alloys are provided. The alloy compositions are based on a U-20Pu-3Am-2Np-15Zr alloy, along with additions of 1 and 1.5 wt% RE (at the expense of U) where RE denotes rare earth alloy of cerium, lanthanum, praseodymium and neodymium. Phase behavior and associated transitions have been compared to available U-Pu-Zr ternary diagrams with acceptable agreement. Enthalpies of transition were deconvoluted from heating and cooling thermal traces for relatively reliable values. The rare earth additions to the base alloy have a minimal influence on the room temperature phases present, but the room temperature phases present slightly impacted the enthalpies of transition and transition temperatures.  相似文献   
77.
This longitudinal study used multilevel modeling to examine the relationships between witnessing intimate partner violence (IPV), community and school violence exposure (CSVE), family social support, gender, and depression over 2 years within a sample of 100 school-aged children. We found significant between-child differences in both the initial levels of depression and the trajectories of depression; depression over time was positively associated with change in witnessing IPV and CSVE and negatively associated with change in support. Two significant 3-way interactions were found: Gender and initial support, as well as gender and initial witnessing IPV, both significantly moderated the effect of change in witnessing IPV on the children’s depression over time. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
78.
79.
The methanogenesis of black liquor from pulp and paper mill was achieved using immobilized cell technology in a laboratory‐scale two‐stage reactor system run continuously for 340 days. The optimum organic loading rate for the anaerobic treatment of black liquor was 8.0 kgm?3d?1 at which the % COD removal, biogas production and methane content were 55%, 11 dm3d?1 and 71%, respectively. Organic loading rates above 8.0 kgm?3d?1 were observed to be toxic to the methanogenic bacteria and resulted in decreased methane content, biogas and COD removal. The applicability of the system to the large‐scale processing and treatment of paper mill liquid waste is discussed. © 2001 Society of Chemical Industry  相似文献   
80.
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