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   1812篇
  免费   47篇
  国内免费   1篇
电工技术   14篇
综合类   1篇
化学工业   388篇
金属工艺   27篇
机械仪表   83篇
建筑科学   62篇
矿业工程   8篇
能源动力   59篇
轻工业   515篇
水利工程   18篇
石油天然气   9篇
无线电   71篇
一般工业技术   236篇
冶金工业   30篇
原子能技术   7篇
自动化技术   332篇
  2025年   1篇
  2024年   31篇
  2023年   25篇
  2022年   48篇
  2021年   102篇
  2020年   73篇
  2019年   87篇
  2018年   97篇
  2017年   88篇
  2016年   85篇
  2015年   82篇
  2014年   88篇
  2013年   235篇
  2012年   140篇
  2011年   156篇
  2010年   143篇
  2009年   100篇
  2008年   68篇
  2007年   39篇
  2006年   37篇
  2005年   16篇
  2004年   11篇
  2003年   12篇
  2002年   19篇
  2001年   6篇
  2000年   8篇
  1999年   8篇
  1998年   15篇
  1997年   8篇
  1996年   2篇
  1995年   8篇
  1994年   1篇
  1993年   1篇
  1992年   1篇
  1989年   1篇
  1983年   1篇
  1982年   1篇
  1981年   2篇
  1980年   1篇
  1979年   1篇
  1978年   1篇
  1975年   1篇
  1965年   2篇
  1964年   1篇
  1963年   2篇
  1953年   3篇
  1938年   2篇
排序方式: 共有1860条查询结果,搜索用时 0 毫秒
61.
    
Intracerebral hemorrhage (ICH) is a complex and heterogeneous disease, and there is no effective treatment. Spontaneous ICH represents the final manifestation of different types of cerebral small vessel disease, usually categorized as: lobar (mostly related to cerebral amyloid angiopathy) and nonlobar (hypertension-related vasculopathy) ICH. Accurate phenotyping aims to reflect these biological differences in the underlying mechanisms and has been demonstrated to be crucial to the success of genetic studies in this field. This review summarizes how current knowledge on genetics and epigenetics of this devastating stroke subtype are contributing to improve the understanding of ICH pathophysiology and their potential role in developing therapeutic strategies.  相似文献   
62.
63.
The ability of dendrimer 2G‐[Si{O(CH2)2N(Me)2+(CH2)2NMe3+(I?)2}]8 (NN16) to transfect a wide range of cell types, as well as the possible biomedical application in direct or indirect inhibition of HIV replication, was investigated. Cells implicated in HIV infection such as primary peripheral blood mononuclear cells (PBMC) and immortalized suspension cells (lymphocytes), primary macrophages and dendritic cells, and immortalized adherent cells (astrocytes and trophoblasts) were analyzed. Dendrimer toxicity was evaluated by mitochondrial activity, cell membrane rupture, release of lactate dehydrogenase, erythrocyte hemolysis, and the effect on global gene expression profiles using whole‐genome human microarrays. Cellular uptake of genetic material was determined using flow cytometry and confocal microscopy. Transfection efficiency and gene knockdown was investigated using dendrimer‐delivered antisense oligonucleotides and small interfering RNA (siRNA). Very little cytotoxicity was detected in a variety of cells relevant to HIV infection and erythrocytes after NN16 dendrimer treatment. Imaging of cellular uptake showed high transfection efficiency of genetic material in all cells tested. Interestingly, NN16 further enhanced the reduction of HIV protein 24 antigen release by antisense oligonucleotides due to improved transfection efficiency. Finally, the dendrimer complexed with siRNA exhibited therapeutic potential by specifically inhibiting cyclooxygenase‐2 gene expression in HIV‐infected nervous system cells. NN16 dendrimers demonstrated the ability to transfect genetic material into a vast array of cells relevant to HIV pathology, combining high efficacy with low toxicity. These results suggest that NN16 dendrimers have the potential to be used as a versatile non‐viral vector for gene therapy against HIV infection.  相似文献   
64.
A series of N‐(4‐cyano‐3‐trifluoromethyl‐phenyl)‐2‐ethoxy‐6‐alkyl (and alkenyl) benzamides related to the anacardic acid derivative CTPB have been prepared from 2,6‐dihydroxybenzoic acid with a Suzuki coupling and addition of the anion of 4‐cyano‐3‐trifluoromethylphenylamine to a benzodioxinone as the key steps. In U937 cells, these analogues, in particular 7 c , 7 d , 7 f and 7 j , induced cell‐cycle arrest in the G1 phase, caused apoptosis in about 20 % of the cells, and increased the acetylation levels of H3. These activities correlate with the enzymatic activation of histone lysine acetyltransferases (KATs): CBP and PCAF.  相似文献   
65.
A nickel catalyst (5.75 wt.%) supported on gamma-alumina was evaluated through autothermal reforming of methane (ATR). The reforming process was pointed to hydrogen production, following thermodynamic and stoichiometric predictions. The catalyst was characterised by several methods including atomic absorption spectroscopy (AAS), B.E.T.-N2, X-ray diffraction (XRD), scanning electron microscope (SEM) and thermal analyses (thermogravimetry, TG; derivate thermogravimetry, DTG; and differential thermal analysis, DTA). Experimental evaluations in a fixed-bed reactor (1023–1123 K, 1.00 bar, 150–400 cm3/min feed) presented methane conversions in the range of 40–65%. The effluent mixtures provided hydrogen yields in the range of 78–84%, carbon monoxide 3–14%, and carbon dioxide 5–18%. High molar H2/CO ratios, ranging from 8 to 90, were obtained. Operating autothermal conditions (excess of steam, 1023–1123 K, 1.00 bar) provided low coke formation and high hydrogen selectivity (81%) for methane reforming.  相似文献   
66.
         下载免费PDF全文
In this work,we report the mechanical properties of an alternative material based on a mixture of natural clay and ferruginous sand in pellet form for CO2 capture. These raw materials were collected from Ecuador,and they contain iron and titanium oxides from volcanic origin. To evaluate the effect of the sand content on the mechanical properties of pellets,the samples were manually prepared with 0 (control sample),15,and 25 wt.% sand contents and analyzed using free-fall drop impact and uniaxial compression tests. The uniaxial compression test was carried out under three conditions: using sieved sand,using sand without sieving,and under wet conditions. The sand contents caused the drop number to decrease in the free-fall drop impact test. From the uniaxial compression test,the compressive strength,elastic modulus,and toughness were calculated. The elastic modulus showed a better performance for samples with lower porosity. The compressive strength demonstrated higher values for samples with 15 wt.% sand contents than for samples with the other sand contents. The toughness values did not significantly change. It was evidenced that the porosity,mineral composition,and humidity exerted an influence during the mechanical tests. The mineral phases were analyzed by X-ray diffraction,and quantitative analysis based on whole-powder-pattern fitting revealed that the iron and titanium oxide contents increased as the concentration of sand in the pellets increased.  相似文献   
67.
         下载免费PDF全文
Oil-derived middle distillates (straight-run gas oil and mixture with light cycle oil and coker gas oil) for Ultra-Low Sulfur Diesel (ULSD) production by HyDroTreating (HDT) were pretreated by selective Nitrogen Organic Compounds (NOC) adsorption. Highly crystalline Metal-Organic Framework (MOF) MIL-101(Cr) prepared with propylene oxide (proton scavenger) as textural improver was used to that end. MOF was characterized by N2 physisorption,X-ray diffraction,thermal analysis,infrared,Raman and UV-vis spectroscopies,and electron microscopy (SEM and HR-TEM). NOC removal was carried out at room temperature and atmospheric pressure,the adsorbent being easily regenerable under mild conditions. Extruded MOF efficiently removed NOC from real feedstocks to concentrations ~ 80 ppm which allowed ULSD production at much milder conditions to those used during pristine feedstocks HDT. Operating temperature could be significantly diminished (from 350 to 330 °C,at 56 kg cm−2(5.77 MPa),LHSV = 1.5 h−1,H2/oil = 2500 ft3bbl−1(445 m3m−3)) which could notably prolong cycle life of NiMo/Al2O3 formulation used.  相似文献   
68.
Regulations affect every aspect of our lives. Compliance with the regulations impacts citizens and businesses similarly: they have to find their rights and obligations in the complex legal environment. The situation is more complex when languages and time versions of regulations should be considered. To propose a solution to these demands, we present a semantic enrichment approach which aims at (1) decreasing the ambiguousness of legal texts, (2) increasing the probability of finding the relevant legal materials, and (3) utilizing the application of legal reasoners. Our approach is also implemented both as a service for citizens and businesses and as a modeling environment for legal drafters. To evaluate the usefulness of the approach, a case study was carried out in a large organization and applied to corporate regulations and Hungarian laws. The results suggest this approach can support the previous aims.  相似文献   
69.
70.
The main aim of this study is to characterize the effect of some commercial detergents on whey proteins in order to select an efficient detergent to clean inorganic membranes fouled during the process of whey proteins fractionation. The influence of such variables such as time, pH, temperature, type and detergent concentration on the rate of protein hydrolysis has been established. Also, the nature and size of produced peptides have been determined. The most efficient values of cleaning parameters have been obtained by using the enzymatic detergent P3-Ultrasil 62.  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