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   1772篇
  免费   153篇
  国内免费   44篇
电工技术   42篇
综合类   66篇
化学工业   463篇
金属工艺   54篇
机械仪表   82篇
建筑科学   69篇
矿业工程   31篇
能源动力   48篇
轻工业   151篇
水利工程   18篇
石油天然气   48篇
武器工业   2篇
无线电   208篇
一般工业技术   229篇
冶金工业   185篇
原子能技术   2篇
自动化技术   271篇
  2024年   12篇
  2023年   25篇
  2022年   92篇
  2021年   106篇
  2020年   39篇
  2019年   46篇
  2018年   71篇
  2017年   68篇
  2016年   78篇
  2015年   64篇
  2014年   76篇
  2013年   107篇
  2012年   95篇
  2011年   123篇
  2010年   87篇
  2009年   85篇
  2008年   96篇
  2007年   81篇
  2006年   65篇
  2005年   67篇
  2004年   28篇
  2003年   48篇
  2002年   45篇
  2001年   26篇
  2000年   29篇
  1999年   33篇
  1998年   77篇
  1997年   49篇
  1996年   34篇
  1995年   18篇
  1994年   21篇
  1993年   13篇
  1992年   13篇
  1991年   1篇
  1990年   11篇
  1989年   6篇
  1988年   3篇
  1987年   1篇
  1986年   3篇
  1985年   4篇
  1984年   2篇
  1982年   2篇
  1981年   3篇
  1980年   3篇
  1979年   1篇
  1978年   2篇
  1977年   4篇
  1976年   3篇
  1975年   2篇
  1970年   1篇
排序方式: 共有1969条查询结果,搜索用时 609 毫秒
101.
卵黄高磷蛋白磷酸肽制备工艺的研究   总被引:1,自引:0,他引:1  
以卵黄高磷蛋白为原料,经碱法脱磷,胰蛋白酶水解后制备成卵黄高磷蛋白磷酸肽(PPP)。研究表明,脱磷率为42.43%的PPP其钙结合能力最强,同时确定了PPP制备过程中的最佳酶解条件为:底物浓度为1%,温度为50℃,酶浓度6%,pH为10,此时卵黄高磷蛋白的水解度为21.8%。  相似文献   
102.
近年来我国突发性天然气供应中断事件的发生率呈现增长趋势,对我国经济、社会稳定和人们的正常生活带来了严重影响。突发性事件发展过程是一个处于快速变化中的动态过程,信息具有不确定性和模糊性的特征,难以运用单一的方法和模型进行分析和决策。因此,结合Markov预测法、三角模糊数和改进型TOPSIS法,构建了应对突发性天然气供应中断的动态多目标应急决策模型(Markov-TOPSIS模型)。即采用Markov动态预测来反映天然气中断应急决策的动态特性,运用模糊理论以实现专家决策的量化分析,结合灰色关联和TOPSIS方法对应急决策中模糊的、不确定信息进行有效处理,并实现多目标综合评价。最后,以某区域天然气供应中断为例,对该模型进行了验证。结果表明:该模型能够有效处理天然气中断应急决策过程中面临的动态变化、信息模糊和多目标决策问题,可根据突发事件的不同发展阶段选择最优决策方案。  相似文献   
103.
在基于访问控制粒度和多维安全拓扑空间的基础上分析了入侵攻击的特点,并提出基于空间扩维特征的入侵检测模型--SEDIDS. 为访问控制系统中的实体建立了语义网络模型,用语义网络完备性推理来检测访问控制实体的完整性,作为入侵攻击行为判断的依据,从而取代了依赖训练数据集建立系统访问模式轮廓进行比对的入侵检测传统手段.实验结果表明:该模型相对于传统的入侵检测具有较低的漏报率和误报率,并有较高的运行效率.  相似文献   
104.
The effect of the clay content and the method of its combination with amine-terminated butadiene-acrylonitrile (ATBN) on the structure and behavior of epoxy was studied. In the case of the simultaneous addition of both components, the increasing clay content had a very small effect on the size of the reaction-induced phase separation-formed particles at 5% rubber content due to predominant elimination of two major clay effects, i.e., the nucleation due to phase separation and the kinetics. As a result, both the time window between the onset of phase separation and vitrification and the viscosity at the cloud point did not change significantly. The minor change in the particle size/clay content dependences with different curing temperatures indicates that the balance between the two clay effects shifted. The corresponding study of the mechanical behavior indicated that the best balanced mechanical properties were obtained at certain clay/ATBN ratios, and thus, there was synergy between the components. Similar mechanical parameters were obtained for the application of both components in the form of ATBN/montmorillonite intercalate. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012  相似文献   
105.
In this paper, the pressure effect on superconductivity and magnetism has been investigated in FeSe x (x=0.80,0.88). The magnetization curves display anomaly at T s1∼106 K and T s2∼78 K except for the superconducting diamagnetic transition around T c ∼8 K. The magnetic anomaly at T s1 and T s2 can be related to a ferromagnetic and an antiferromagnetic phase transition, respectively, as revealed by specific heat measurements. The application of pressure not only raises T c , but also increases both T s1 and T s2.   相似文献   
106.
通过对煤炭质量常规分析项目(水分、灰分、挥发分、全硫、碳氢、发热量)检测流程和数据处理进行分析,制定煤质检测信息全自动提取的方案。形成与LIMS系统整理对接设计;通过配置相应硬件、网络和系统平台,实现样品检测数据的采集、录入、处理、检查、判定、存储、传输、共享等各项业务管理。  相似文献   
107.
Highly efficient blue electrophosphorescent organic light‐emitting diodes incorporating a bipolar host, 2,7‐bis(diphenylphosphoryl)‐9‐[4‐(N,N‐diphenylamino)phenyl]‐9‐phenylfluorene (POAPF), doped with a conventional blue triplet emitter, iridium(III) bis[(4,6‐difluoro‐phenyl)pyridinato‐N,C]picolinate (FIrpic) are fabricated. The molecular architecture of POAPF features an electron‐donating (p‐type) triphenylamine group and an electron‐accepting (n‐type) 2,7‐bis(diphenyl‐phosphoryl)fluorene segment linked through the sp3‐hybridized C9 position of the fluorene unit. The lack of conjugation between these p‐ and n‐type groups endows POAPF with a triplet energy gap (ET) of 2.75 eV, which is sufficiently high to confine the triplet excitons on the blue‐emitting guest. In addition, the built‐in bipolar functionality facilitates both electron and hole injection. As a result, a POAPF‐based device doped with 7 wt% FIrpic exhibits a very low turn‐on voltage (2.5 V) and high electroluminescence efficiencies (20.6% and 36.7 lm W?1). Even at the practical brightnesses of 100 and 1000 cd m?2, the efficiencies remain high (20.2%/33.8 lm W?1 and 18.8%/24.3 lm W?1, respectively), making POAPF a promising material for use in low‐power‐consumption devices for next‐generation flat‐panel displays and light sources.  相似文献   
108.
109.
The objective of the present work was to determine the nutrient and polyphenolic composition of dried strawberry press cake (SPC), as well as that of its seedless fraction, termed exhausted strawberry flesh (ESF). The study materials were obtained over three consecutive years from an industrial facility manufacturing concentrated fruit juices. On average, SPC consists of 40 % seeds, 3.5 % sand, and about 55 % ESF. In the dry matter of SPC and ESF, the mean content of fat is 9.8 and 3.5 %, protein 17.3 and 20.4 %, and total polyphenols 3,449 and 5,410 mg/100 g, respectively. Both materials are rich in total dietary fiber, whose content amounts to 60 %. The predominant polyphenols in SPC and ESF are flavanols and ellagitannins, which collectively constitute over 95 % of the determined total polyphenol content. In ESF composition, of note is the high content of the strawberry ellagitannin, agrimoniin, which is approximately 1,000 mg/100 g DW (dry weight). SPC has the disadvantage of being highly contaminated with sand (3.4 %), which accumulates in ESF (5.6 %). However, as compared to SPC, ESF contains approximately 20 % more proteins and almost three times less fat. Based on our results, it appears that SPC may be considered a potential raw material for seed recovery. Moreover, dried strawberry press cake, and especially its seedless fraction (ESF), despite substantial contamination with sand, may be used as rich and widely available raw material for the extraction of proanthocyanidins and/or ellagitannins, and especially dimeric agrimoniin.  相似文献   
110.
The climate change influence over the oceans has been the subject of numerous articles informs and strategies from different scientific perspectives, focused mainly in the ecological impact. The majority of the related studies have been focused in measuring or predicting the physical, chemical, geographical, sociological and economical consequences of this reality, which seems to be unstoppable, and only a few of them are devoted to detect the effects of the climate change over the quality of seafood products, wild or cultivated.The stress produced in marine organisms by the consequences of climate change is reflected at the cell molecular level, being affected the metabolite concentration, the expression of proteins and their modifications. The study of the climate change may take advantage of these molecular changes, which may be used as a source of possible biomarkers of its evolution.After the genomic age, proteomics appears as a young but robust discipline for a global study of the protein content in cells, including their identification, possible modifications, quantification of differential expression and tissue localization, being the most adequate set of methodologies to evidence protein changes in marine organisms affected by climate variations. In the last decade proteomic technologies have experienced an exponential development, but the research has been mainly applied to biomedical and human health research, being scarcely focused to the study of the marine environment. The application of the proteomics methods to study the effects of climate change over seafood, mainly from the safety point of view, is reviewed.  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