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   510篇
  免费   35篇
  国内免费   12篇
电工技术   16篇
综合类   15篇
化学工业   89篇
金属工艺   25篇
机械仪表   18篇
建筑科学   17篇
矿业工程   4篇
能源动力   12篇
轻工业   137篇
水利工程   19篇
石油天然气   7篇
武器工业   42篇
无线电   41篇
一般工业技术   50篇
冶金工业   12篇
原子能技术   3篇
自动化技术   50篇
  2024年   1篇
  2023年   17篇
  2022年   21篇
  2021年   29篇
  2020年   22篇
  2019年   12篇
  2018年   12篇
  2017年   5篇
  2016年   17篇
  2015年   10篇
  2014年   35篇
  2013年   64篇
  2012年   100篇
  2011年   77篇
  2010年   32篇
  2009年   27篇
  2008年   14篇
  2007年   16篇
  2006年   12篇
  2005年   4篇
  2004年   3篇
  2003年   1篇
  2002年   2篇
  2000年   4篇
  1999年   2篇
  1998年   3篇
  1997年   2篇
  1996年   1篇
  1991年   1篇
  1988年   3篇
  1987年   2篇
  1986年   6篇
排序方式: 共有557条查询结果,搜索用时 46 毫秒
91.
In this study, a dynamic interval-parameter optimization model (DIP-REM) has been developed for supporting long-term energy systems planning in association with GHG mitigation in the region of Liaoning province. The model can describe Liaoning province energy planning systems as networks of a series of energy flows, transferring extracted/imported energy resources to end users through a variety of conversion and transmission technologies over a number of periods and address the problem of GHG-emission reduction within a general energy planning systems framework under uncertainty. Two scenarios (including a reference case) are considered corresponding to different GHG-emission mitigation levels for in-depth analysis of interactions existing among energy, socio-economy and environment in the Liaoning province. Useful solutions for Liaoning province energy planning systems have been generated, reflecting trade-offs among energy-related, environmental and economic considerations. The results can not only provide optimal energy resource/service allocation and capacity-expansion plans, but also help decision-makers identify desired policies for GHG mitigation with a cost-effective manner in the region of Liaoning province. Thus, it can be used by decision makers as an effective technique in examining and visualizing impacts of energy and environmental policies, regional development strategies and emission reduction measures within an integrated and dynamic framework.  相似文献   
92.
High resolution models of air pollution transport and transformation are necessary in order to test possible abatement strategies based on pollution control and to forecast high pollution episodes. Models are especially relevant for secondary pollutants like ozone and nitrogen dioxide which are formed in the atmosphere through nonlinear chemical reactions involving primary pollutant species far from their sources. Often we are trying to resolve the interactions between plumes from point sources such as power stations and regional pollution tides of ozone formed in other European countries. One method of tackling this problem of different scales is with different grid sizes, using highly resolved grids in regions where the structure is very fine. This paper describes the use of 3-D adaptive gridding models for pollution transport and reaction using both a layered and a fully adaptive 3-D tetrahedral approach.  相似文献   
93.
Magnetic susceptibility can provide rich environmental information, especially for hazardous heavy metals and saline-alkaline in the contaminated soils. Magnetic susceptibility in four vertical profiles from saline-alkaline soils in lower Hai River basin was investigated. Soil sites were extended from alluvial fan to coastal plain areas. They are aligned along a latitudinal strip. Magnetic parameters including low/high frequency susceptibility, frequency-dependent susceptibility was measured. Moreover, some standard pedological parameters such as pH value and organic matter content were also determined. The results showed that low frequency magnetic susceptibility values is very high at the surface and decreases with the profile to a low value. In all profiles from alluvial fan frequency-dependent susceptibility greater than 3% may suggest the presence of relatively more super-paramagnetic particles. Magnetic susceptibility showed obvious vertical distribution in alluvial fan higher than coastal plain. No significant correlations between organic matter, pH and low frequency magnetic susceptibility were found, while there is a negative correlation between organic matter and frequency-dependent susceptibility. A positive correlation between pH and frequency-dependent susceptibility was found in the study areas.  相似文献   
94.
The effects of concentration, pH value and ionic strength on the kinetic self-assembly of acid-soluble collagen from walleye pollock (Theragra chalcogramma) skin were investigated. A two-phase kinetic process was provided which included the formation of nucleus center and nucleus growth, the first phase being the controlled step for collagen self-assembly. Collagen showed marked assembly behavior when concentration reaching and above 0.6 mg/mL, and higher concentration could accelerate collagen self-assembly. Rate constants of the first and second assembly phase both increased with pH to a maximum around pH 7.2 and then decreased, indicating that pH 7.2 was the optimum pH value for collagen self-assembly. The kinetics of collagen self-assembly could be modulated by NaCl concentration. The concentration of NaCl from 30 to 60 mM was more suitable to self-assemble for pollock skin collagen.  相似文献   
95.
挂面包装机包卷装置的设计与研究   总被引:1,自引:0,他引:1  
郭超  付君  杜晓洋  石峰  宋谭 《食品与机械》2012,28(2):87-89,146
通过包卷装置实现挂面的卷纸和包装,采用拨轮机构和不完全齿轮机构实现个动作的时间协调,包卷过程则采用循环牵引机构带动包装带,并带动包装纸和散装挂面在包卷装置中做纯滚动,从而实现卷纸动作;同时使用凸轮振动装置将挂面振实;包装带牵引装置由不完全齿轮机构和具有急回特性的曲柄摇杆机构相配合组成。  相似文献   
96.
苹果经榨汁澄清后,分别接种七种果酒酵母,20℃恒温发酵。发酵结束后,对苹果酒进行理化分析和感官评价,评定七种酵母的酿造特征,并观察外加氮源和不同量SO2对酵母及苹果酒理化指标的影响。实验结果表明:在相同试验条件下,7号酵母起酵最慢,4号发酵最快,6号发酵最旺盛。加硫组,整体起酵慢。各种酵母酿造苹果酒的理化指标有所不同,酒的香气、口味和风格也不同。氮源和SO2对七种酵母发酵苹果酒的理化指标影响不显著。  相似文献   
97.
张燕 《酿酒科技》2012,(9):116-118
以高效液相色谱法建立对葡萄酒中邻氨基苯甲酸酯类(邻氨基苯甲酸甲酯、邻氨基苯甲酸乙酯、N-甲基代邻氨基苯甲酸甲酯)葡萄香精的检测方法。结果表明,3种邻氨基苯甲酸酯类葡萄香精在0.2~50 mg/L范围内均呈良好的线性,相对标准偏差RSD均小于1%,相关系数R2在0.9987~0.9992内,最低检出限可达0.006 mg/L,样品平均回收率在85%~90%之间。  相似文献   
98.
浅色焦香麦芽含有较多的类黑素等高分子物质,研究采用添加6%的浅色焦香麦芽酿造低度淡爽型啤酒。结果表明,添加浅色焦香麦芽可使啤酒口味更加柔和醇厚;明显增加麦芽香味;不影响啤酒的色度;可增加啤酒的泡沫性;成熟啤酒的各项指标符合GB4928要求;该麦芽适合酿造低度淡爽型啤酒或酿制高辅料比啤酒。  相似文献   
99.
目的:探讨天麻素对D-半乳糖诱导的BV2细胞衰老的保护作用及机制。方法:使用不同浓度(10、20、30和40 μg/mL)的D-半乳糖刺激BV2细胞24 h,建立细胞衰老模型,并用CCK-8法筛选出D-半乳糖的最佳造模浓度;实验分为4组:正常组、模型组、Silent mating type information regulation 2 homolog 3(SIRT3)抑制剂+天麻素组和天麻素组;用CCK-8法检测不同浓度(10、20、30、40和50 μmol/L)的天麻素对D-半乳糖刺激的BV2细胞活力的影响,并筛选出最佳的天麻素浓度;使用β-半乳糖苷酶(Senescence β-Galactosidase,SA-β-Gal)染色检测细胞衰老面积;使用生化法检测各组细胞活性氧(Reactive oxygen species,ROS)水平;使用Enzyme linked immunosorbent assay(ELISA)法检测各组细胞神经炎症因子IL-1β(Interleukin 1β,IL-1β)、IL-6(Interleukin 6,IL-6)和TNF-α(Tumor necrosis factor α,TNF-α)水平;使用免疫荧光法检测各组细胞SIRT3荧光强度;使用Western Blot法检测细胞SIRT3、P16和P21的蛋白表达水平。结果:30 μg/mL的D-半乳糖刺激BV2细胞活力极显著降低(P<0.01),引起BV2细胞中SA-β-Gal染色面积和衰老蛋白P16和P21表达极显著增加(P<0.01),细胞中ROS水平和炎症因子IL-1β、IL-6和TNF-α水平极显著增高(P<0.01),细胞内SIRT3蛋白表达极显著降低(P<0.01)。而30 μmol/L天麻素能极显著提高D-半乳糖刺激的BV2细胞活力(P<0.01),并且极显著降低细胞SA-β-Gal染色面积和衰老蛋白P16和P21表达水平(P<0.01),极显著降低ROS水平和神经炎症因子IL-1β、IL-6和TNF-α水平(P<0.01),极显著提高细胞内SIRT3蛋白荧光强度和表达水平(P<0.01)。结论:天麻素能够提高D-半乳糖刺激的BV2细胞活力,改善BV2细胞衰老染色和衰老蛋白表达,并降低ROS水平和减缓炎症反应,这可能与天麻素提高SIRT3蛋白表达有关。  相似文献   
100.
为了指导研究爆炸压实工艺参数的选择,通过改变爆轰速度与装药厚度来改变爆炸冲击能,重点研究爆炸压实工艺参数对钢管能量与变形的影响.研究表明:当其他工艺因素相同、仅爆轰速度不同时,将导致爆轰压力、钢管壁速度、爆炸冲击能、粉末压实能等显著不同,但钢管的变形与能量却几乎不变;当采用爆轰速度极高的黑索今炸药时,由于爆轰压力与爆炸冲击能过高,导致钢管头部被切掉;对硝酸脲炸药而言,随着装药厚度与炸药/钢管质量比增加,钢管的能量与变形、爆炸冲击能与粉末压实能单调增加.  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