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   1977篇
  免费   61篇
  国内免费   6篇
电工技术   58篇
综合类   9篇
化学工业   527篇
金属工艺   37篇
机械仪表   64篇
建筑科学   52篇
矿业工程   7篇
能源动力   50篇
轻工业   227篇
水利工程   19篇
石油天然气   4篇
无线电   133篇
一般工业技术   300篇
冶金工业   213篇
原子能技术   23篇
自动化技术   321篇
  2022年   13篇
  2021年   38篇
  2020年   22篇
  2019年   24篇
  2018年   24篇
  2017年   37篇
  2016年   61篇
  2015年   39篇
  2014年   54篇
  2013年   98篇
  2012年   87篇
  2011年   98篇
  2010年   75篇
  2009年   96篇
  2008年   84篇
  2007年   80篇
  2006年   61篇
  2005年   61篇
  2004年   55篇
  2003年   50篇
  2002年   57篇
  2001年   41篇
  2000年   34篇
  1999年   31篇
  1998年   43篇
  1997年   35篇
  1996年   29篇
  1995年   28篇
  1994年   28篇
  1993年   31篇
  1992年   27篇
  1991年   18篇
  1990年   17篇
  1989年   20篇
  1988年   13篇
  1987年   18篇
  1986年   13篇
  1985年   22篇
  1984年   20篇
  1983年   26篇
  1982年   13篇
  1981年   18篇
  1980年   19篇
  1979年   29篇
  1978年   21篇
  1977年   22篇
  1975年   16篇
  1974年   24篇
  1973年   12篇
  1971年   11篇
排序方式: 共有2044条查询结果,搜索用时 0 毫秒
91.
Towards cognitive evaluation of computer-drawn sketches   总被引:1,自引:0,他引:1  
This paper seeks to raise visual comparisons beyond subjective opinions into evidence-based visual reasoning. It provides an informal deductive analysis of the marks in sketches derived with two competing line-filtering algorithms. This prompted the novel speculation that the visual system might be placing some types of anomalies in the foreground of mental 3D space, where they can be ignored. A brief survey is provided to encourage informed debate. Although the proposed cognitive computation was not automated, it justified the rejection of the Douglas–Peucker algorithm in favour of Visvalingam's algorithm in subsequent research within the Cartographic Information Systems Research Group (CISRG).  相似文献   
92.

Sciencenews10-Jahr-Feier

Institut für Maschinelles Sehen und Darstellen  相似文献   
93.
The method of Fourier optics is applied to the problem of time-gated imaging through scattering media. Tb adapt the problem to this treatment, appropriate alterations are made: The continuous medium is replaced by a cascade of thin scatterers, and a spatial filtering process is substituted for the conventional gating processes. Closed-form solutions are derived.  相似文献   
94.
We have performed high-dose Fe ion implantation into Si and characterized ion-beam-induced microstructures as well as annealing-induced ones using transmission electron microscopy (TEM) and grazing-incidence X-ray diffraction (GIXRD). Single crystals of Si(1 0 0) substrate were irradiated at 623 K with 120 keV Fe+ ions to a fluence of 4 × 1017 cm−2. The irradiated samples were then annealed in a vacuum furnace at temperatures ranging from 773 K to 1073 K. Cross-sectional TEM observations and GIXRD measurements revealed that a layered structure is formed in the as-implanted specimen with ε-FeSi, β-FeSi2 and damaged Si, as component layers. A continuous β-FeSi2 layer was formed on the topmost layer of the Si substrate after thermal annealing.  相似文献   
95.
Kurt Beyer 《AI & Society》2002,16(3):278-287
This narrative describes the making of a German electrical engineer, Kurt Beyer, into a micro-entrepreneur. He set for himself the goal of sailing around the world in his own vessel – without being able to afford to buy such a ship. Many people in Germany have in recent years started to build their own sea-going vessels in order to escape from the creativity-stifling and restrictive patterns of their lives and work. Only a few of them have ever finished building their vessels. Firstly, this report describes the experiences of one of those few who have made it. Secondly, it tells the story of how this engineer himself turned into a micro-entrepreneur during the period of yacht-building and how later he started his own charter enterprise, centred around his yacht. Following the model of entrepreneurship described by Dassen-Housen in this issue of AI & Society, the narrative illustrates what it means to run such an enterprise in view of the international competition. Here follows the narrative of the engineer and ship-builder himself (translated by D. Brandt).  相似文献   
96.
The objective of this study is to investigate experimentally and theoretically whether sodium carbonate (Na2CO3) salt is suitable for establishing a salinity gradient in a salt-gradient solar-pond (SGSP). For this purpose, a small-scale prismatic solar-pond was constructed. Experiments were conducted in the laboratory under the incident radiation from two halogen-lamps acting as a solar simulator. Furthermore, a one-dimensional transient mathematical model that describes the heat and mass transfer behaviour of the SGSP was developed. The differential equations obtained were solved numerically using a finite-difference method. It was found from the experiments that the density gradient, achieved using sodium carbonate salt, can suppress convection from the bottom to the surface of the pond.  相似文献   
97.
Assessed 100 undergraduates' developmental theories about their affective relationships with their parents, using a retrospective method. Ss used drawings and questionnaire ratings to portray their relationships with parents at 5 points between infancy and the present. From infancy to their current age, Ss portrayed their relationships in 2 major ways: They perceived themselves as gaining in responsibility, dominance, independence, and similarity from infancy to the present, whereas they portrayed their parents as experiencing a decline on these dimensions. For variables indicating closeness and love, however, there was a striking discontinuity in these linear trends: Although Ss perceived linear trends from infancy to adolescence, they depicted their current relationships as involving a great deal more love and closeness. They also portrayed their relationships with mothers and fathers somewhat differently. More responsibility was felt toward the mothers and they were portrayed as especially friendly, but Ss felt more similar to their fathers, whom they perceived as dominant. Results suggest that late adolescents construct theories of the affective components of their relationships with their parents to serve the needs of separation while maintaining a close affective tie to the parents. (24 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
98.
Zusammeufassung Zur Überprüfung des Auftretens von Nitrosaminen [2] im Rahmen der Maillard-Reaktion wurden die flüchtigen Produkte verschiedener Glucose-Aminosäure-Modell-gemische durch Kombination von Gaschromatographie and Massenspektrometrie, Polarographie und Dünnschicht-Chromatographie untersucht. Das Auftreten von Nitrosaminen kann durch die Ergebnisse eindeutig ausgeschlossen werden.
The problem of formation of nitrosamines by reacting monosaccharides with aminoacids (maillard-reaction)
Summary For proving the formation of nitrosamines applying maillardconditions [2] we tested the volatile reaction products of various glucose-aminoacid mixtures by coupling gas chromatography and mass spectrometry, polarography and thin-layer chromatography. The appearence of nitrosamines could undoubtedly be excluded according to the results.
  相似文献   
99.
100.
We wanted to test the psychometric reliability and validity of self-reported information on psychological and functional status gathered by computer in a sample of primary care outpatients. Persons aged 65 years and older visiting a primary care medical practice in Baltimore (n=240) were approached. Complete baseline data were obtained for 54 patients and 34 patients completed 1-week retest follow-up. Standard instruments were administered by computer and also given as paper and pencil tests. Test-retest reliability estimates were calculated and comparisons across mode of administration were made. Separately, an interviewer administered a questionnaire to gauge patient attitudes and feelings after using the computer. Most participants (72%) reported no previous computer use. Nevertheless, inter-method reliability of the GDS15 at baseline (0.719, n=47), intra-method reliability of the computer in time (0.797, n=31), inter-method reliability of the CESDR20 at baseline (0.740, n=53), and the correlation between the CESDR20 computer version at baseline and follow-up (0.849, n=34) were all excellent. The inter-method reliability of the CESDR20 at follow-up (0.615, n=37) was lower but still acceptable. Although 28% were anxious prior to using the computer testing system, that percent decreased to 19% while using the system. The efficiency and reliability in comparison to the paper instruments were good or better. Even though most participants had not ever used a computer prior to participating in the study, they had generally favorable attitudes toward the use of computers, and also reported having favorable experience with the computer testing system.  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