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   894篇
  免费   22篇
  国内免费   2篇
电工技术   12篇
化学工业   119篇
金属工艺   14篇
机械仪表   15篇
建筑科学   56篇
矿业工程   2篇
能源动力   19篇
轻工业   58篇
水利工程   13篇
无线电   82篇
一般工业技术   91篇
冶金工业   325篇
原子能技术   6篇
自动化技术   106篇
  2021年   8篇
  2020年   4篇
  2019年   7篇
  2018年   11篇
  2017年   10篇
  2016年   4篇
  2015年   12篇
  2014年   20篇
  2013年   30篇
  2012年   19篇
  2011年   36篇
  2010年   25篇
  2009年   28篇
  2008年   26篇
  2007年   29篇
  2006年   21篇
  2005年   23篇
  2004年   17篇
  2003年   22篇
  2002年   24篇
  2001年   17篇
  2000年   17篇
  1999年   22篇
  1998年   84篇
  1997年   54篇
  1996年   34篇
  1995年   25篇
  1994年   20篇
  1993年   30篇
  1992年   13篇
  1991年   13篇
  1990年   16篇
  1989年   13篇
  1988年   19篇
  1987年   12篇
  1986年   4篇
  1985年   12篇
  1984年   12篇
  1983年   6篇
  1982年   4篇
  1981年   9篇
  1980年   12篇
  1979年   13篇
  1978年   7篇
  1977年   11篇
  1976年   15篇
  1974年   10篇
  1972年   4篇
  1967年   4篇
  1966年   3篇
排序方式: 共有918条查询结果,搜索用时 15 毫秒
51.
Acute kidney injury (AKI) is a common complication of critical illness, and evidence is emerging that suggests AKI disrupts the function of other organs. It is a recognized phenomenon that patients with chronic kidney disease (CKD) have reduced hepatic metabolism of drugs, via the cytochrome P450 (CYP) enzyme group, and drug dosing guidelines in AKI are often extrapolated from data obtained from patients with CKD. This approach, however, is flawed because several confounding factors exist in AKI. The data from animal studies investigating the effects of AKI on CYP activity are conflicting, although the results of the majority do suggest that AKI impairs hepatic CYP activity. More recently, human study data have also demonstrated decreased CYP activity associated with AKI, in particular the CYP3A subtypes. Furthermore, preliminary data suggest that patients expressing the functional allele variant CYP3A5*1 may be protected from the deleterious effects of AKI when compared with patients homozygous for the variant CYP3A5*3, which codes for a non-functional protein. In conclusion, there is a need to individualize drug prescribing, particularly for the more sick and vulnerable patients, but this needs to be explored in greater depth.  相似文献   
52.
<正>简单的纯白瓷块加上素描感十足的黑色包边,营造出立体插画般的视觉错觉。英国陶艺家Katharine Morling用坚硬的陶瓷创作出其他瓶瓶罐罐绝对没有的3D梦幻感。一台堪称古董级别的收银机内似乎装了太多的硬币,抽屉怎么也关不上,一旁放着订书机、记事本、笔筒等小杂物。如果不是有一圈黑色包边清晰地勾勒出轮廓,它们就像是微融的白巧克力。再仔细一看,似乎又像用柔软的纸张剪出的纸艺美物。然而轻轻敲几下,清脆  相似文献   
53.
Though peanuts are classified as a high‐fat food, they possess good proportions of fatty acids deemed as heart healthy. The fatty acid compositions of Runner peanuts were determined for commercially grown cultivars over two recent crop years. GC‐FID analyses revealed that the fatty acid levels for Runner peanuts were significantly (p <0.05) different among the normal, mid‐, and high‐oleic peanuts investigated. Oleic acid‐to‐linoleic acid (O/L) ratios were found to be 1.93 ± 0.30, 5.25 ± 1.12, and 16.9 ± 5.20 for normal, mid‐, and high‐oleic peanut lipids, respectively. Tamrun OL01 possessed a fatty acid profile characteristic of a mid‐oleic cultivar. From the sample set (n = 151), mean % weights for oleic acid and linoleic acid were 52.09 ± 2.84 and 27.38 ± 2.60 in normal, 69.33 ± 3.18 and 13.66 ± 2.35 in mid‐oleic, and 78.45 ± 2.05 and 5.11 ± 1.67 in high‐oleic peanuts, respectively. Cluster analysis segregated cultivars based on fatty acids into normal, mid‐, and high‐oleic groups. Factorial analysis revealed that cultivar effects were significant (p <0.01) for all fatty acids, except for lignoceric acid. Cultivar effects were also highly significant (p <0.001) for O/L, IV, unsaturated/saturated fatty acid (U/S) ratio, and % saturation. Significant crop year effects were shown for palmitic, oleic, arachidic, gondoic, and lignoceric acids, as well as U/S ratio and % saturation. Healthy unsaturated fats accounted for ?80% in all crop years and cultivars.  相似文献   
54.
In the present work, we succeeded in supporting predominantly cuboctahedral Pt nanoparticles onto high surface area carbons while maintaining their shape. These novel catalysts were applied in a realistic fuel cell set-up for the first time and showed remarkable fuel cell performance. A 95% fraction of cuboctahedral Pt nanoparticles was synthesized using tetradecyltrimethylammonium bromide (TTAB) as a stabilizer. Transmission electron micrographs of the synthesized samples demonstrated the presence of monodispersed cuboctahedral particles of 12 nm in size. Cyclic voltammetry (CV) studies of the unsupported cuboctahedral nanoparticles revealed the presence of Pt (110) and (100) facets. The shape-selected Pt nanoparticles were let to absorb onto Vulcan carbon by a simple dispersing procedure to obtain supported shape-selected Pt nanoparticles. Only by this gentle adsorption step of the surfactant-stabilized nanoparticles on the carbonaceous support material, the nanoparticles retained their shape. Finally an MEA was fabricated using the supported shape-selected nanoparticles and tested in a realistic H2-PEM fuel cell environment. In terms of Pt utilization, shape-selected Pt particles were found to be more effective by a factor of four in weight compared to the commercial catalyst.  相似文献   
55.
Home appliances, like washers, dryers, refrigerators, etc., can cause voltage fluctuations and light flicker. A standardized flicker test has been established in Europe (IEC 1000-3-3). However, the European test is designed for 230-V 50-Hz power and needs to be modified for a 115-V 60-Hz supply. In this paper, the reference impedance and the limits of flicker tests for 115 V/60 Hz systems are proposed. A high-performance power analysis system, the Xitron 2803AH power analyzer, was used to study the voltage fluctuations and flicker caused by some washing machines. The analysis and test results provided in this paper can serve as a proposal for establishing a US light flicker testing standard for 115 V/60 Hz  相似文献   
56.
Data from the Victoria Longitudinal Study were used to examine the hypothesis that maintaining intellectual engagement through participation in everyday activities buffers individuals against cognitive decline in later life. The sample consisted of 250 middle-aged and older adults tested 3 times over 6 years. Structural equation modeling techniques were used to examine the relationships among changes in lifestyle variables and an array of cognitive variables. There was a relationship between changes in intellectually related activities and changes in cognitive functioning. These results are consistent with the hypothesis that intellectually engaging activities serve to buffer individuals against decline. However, an alternative model suggested the findings were also consistent with the hypothesis that high-ability individuals lead intellectually active lives until cognitive decline in old age limits their activities. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
57.
Computer modeling of molecular systems is becoming important in the chemical industry. Much of this work has been directed towards empirical studies of biochemical systems using molecular graphics techniques. It has now become possible, with the development of both new software and new hardware, to use more rigorous theoretical methods to study molecules of interest to the chemical industry. The interest at du Pont is in theoretical studies of organic systems, especially those of interest in the field of polymers, such as fluorocarbons. The electronic and molecular structure of models for perfluoropolyacetylene (perfluoro-1, 3-butadiene) and Teflon® (perfluoro-n-butane) will be discussed. A brief discussion of the application of theoretical techniques to energetic calculations will be presented with the focus being on molecular ion affinities. Such results are also useful in modeling plasmas and interstellar reactions.  相似文献   
58.
59.
The Banff Annual Seminar in Cognitive Science (BASICS) was founded in 1982 and has met each spring since then in Banff, Alberta. BASICS was originated to provide an informal atmosphere for the in-depth discussion of a wide variety of research topics within the broadly defined domain of cognitive psychology. Topics covered in this year's seminar included visual spatial attention and target detection, attention and eye movements during reading, the integration of information across eye movements, language production and its dependency on structure, and parallel distributed processing models. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
60.
A survey of Los Angeles County adults was undertaken to determine whether exposure to the overrepresentation of Blacks as criminals on local news programs, attention to crime news, and news trust predicted perceptions of Blacks and crime. After controlling for a number of factors including the diversity of respondents' neighborhood and neighborhood crime rate, attention to crime news was positively related to concern about crime. In addition, attention to crime news was positively associated with harsher culpability ratings of a hypothetical race-unidentified suspect and a Black suspect but not a White suspect. Finally, heavier consumption of Blacks' overrepresentation as criminals on local television news was positively related to the perception of Blacks as violent. The theoretical implications of these findings are discussed in light of chronic activation and accessibility of stereotypical constructs.  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