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   528篇
  免费   2篇
  国内免费   1篇
电工技术   3篇
综合类   3篇
化学工业   154篇
金属工艺   12篇
机械仪表   6篇
建筑科学   26篇
能源动力   26篇
轻工业   40篇
水利工程   1篇
石油天然气   3篇
无线电   48篇
一般工业技术   99篇
冶金工业   35篇
原子能技术   11篇
自动化技术   64篇
  2022年   7篇
  2021年   9篇
  2020年   4篇
  2019年   6篇
  2018年   6篇
  2017年   6篇
  2016年   5篇
  2015年   7篇
  2014年   9篇
  2013年   22篇
  2012年   21篇
  2011年   31篇
  2010年   29篇
  2009年   26篇
  2008年   35篇
  2007年   32篇
  2006年   25篇
  2005年   23篇
  2004年   18篇
  2003年   26篇
  2002年   17篇
  2001年   10篇
  2000年   6篇
  1999年   11篇
  1998年   8篇
  1997年   12篇
  1996年   12篇
  1995年   5篇
  1994年   5篇
  1993年   7篇
  1992年   4篇
  1991年   7篇
  1990年   6篇
  1989年   6篇
  1988年   5篇
  1987年   5篇
  1986年   4篇
  1985年   5篇
  1984年   2篇
  1983年   4篇
  1982年   7篇
  1981年   8篇
  1980年   4篇
  1979年   5篇
  1978年   4篇
  1976年   3篇
  1975年   2篇
  1973年   5篇
  1972年   1篇
  1970年   1篇
排序方式: 共有531条查询结果,搜索用时 15 毫秒
1.
2.
In this paper, we consider a large-scale evacuation problem after a major disaster. The evacuation is assumed to occur by means of a fleet of buses, thus leading to scheduling the evacuation operations by buses [(bus evacuation problem (BEP)]. We propose time-indexed formulations as well as heuristic algorithms such as greedy algorithms and a matheuristic. This matheuristic uses the former formulation to improve the best solution obtained by the greedy heuristics. In computational experiments, we analyze and evaluate the efficiency of the proposed solution algorithms.  相似文献   
3.
We consider a -calculus system in second-orderclassical logic, in which execution of -terms is weak head reduction (call-by-name). By means of some simple examples, we show how it can modelize some aspects of imperative programming languages, such as assignment and escape instructions. A crucial tool is the notion ofstorage operator, for which a simple type is given.  相似文献   
4.
New ordered Laves phases RENi4Mg (RE = Sc, Sm, Tb–Lu) were synthesized from the elements in sealed tantalum ampoules in an induction furnace. Six of the structures were refined on the basis of X-ray single crystal data. The diffraction experiments gave hint for small homogeneity ranges RE1+xNi4Mg1?x. Magnetic susceptibility measurements show Curie–Weiss behavior for RE = Gd, Dy, Ho, Tm, Yb and the resulting effective magnetic moments suggest both stable trivalent states for all RE and a non-magnetic state for Ni. Gd1+xNi4Mg1?x (x ≈ 0.12) orders antiferromagnetically at a Néel temperature of TN = 4.6(5) K. Resistivity measurements reflect the metallic nature of these compounds.  相似文献   
5.
We study the transient gratings photogenerated in the picosecond regime in three families of structures, namely : - structures of thickness in the order of one micron, including quantum wells (GaAs/GaAlAs, CdTe/ CdZnTe). A transmission modulation due to the electric field has been observed. We show that, in accordance with our calculations, this modulation is screened faster than 10 ps at a fluence of a few µJ/cm2. - A structure including GalnAs/GalnAsP MQWS in a cavity. This structure shows a top diffraction efficiency of 2.5 × 10-2 at 1.55 µm for an energy of excitation in the order of 100 µJ/cm2. The diffraction efficiency exhibits several oscillations due to Fabry-Pårot effects. By introducing cavity effects in our model, we show that the diffraction efficiency is amplified by more than a factor 2 with respect to the no-cavity case. Calculations show that the diffraction efficiency may reach 6 × 10-2 around 1.625 µm, for a front mirror reflectivity of 90 %. - Structures including bulk GaAs microcavities. The risetime is lower or in the order of 1 ps while the diffraction efficiency attains 1 %, with an average power of 4 mW (i.e. an energy of 2 µJ/cm2/pulse), compatible with a commutation of packets at 80 MHz.  相似文献   
6.
7.
A detailed knowledge of the light distribution characteristics through advanced window systems is required to improve the visual comfort of the building's occupants while controlling the propagation of daylight in rooms and the solar gains. An innovative bidirectional goniophotometer has recently been set up for this purpose, using digital image capture and the projection of the emerging light on a diffusing screen. It therefore provides a continuous investigation of the bidirectional transmission figures in a time-efficient way. This instrument was converted into a double-purpose device, allowing both transmission and reflection measurements, which induced several strong constraints due to the conflict of incident and emerging light flux in reflection mode: on one hand the incident beam had to be restricted to the sample area only; on the other hand, as the screen obstructed the incoming light flux in some positions, a special opening in the latter was required. The practical answer to these constraints, detailed in this paper, proved to be reliable, appropriate and efficient.  相似文献   
8.
In this paper, a model-based approach to medical image analysis is presented. It is aimed at understanding the influence of the physiological (related to tissue) and physical (related to image modality) processes underlying the image content. This methodology is exemplified by modeling first, the liver and its vascular network, and second, the standard computed tomography (CT) scan acquisition. After a brief survey on vascular modeling literature, a new method, aimed at the generation of growing three-dimensional vascular structures perfusing the tissue, is described. A solution is proposed in order to avoid intersections among vessels belonging to arterial and/or venous trees, which are physiologically connected. Then it is shown how the propagation of contrast material leads to simulate time-dependent sequences of enhanced liver CT slices.  相似文献   
9.
The aim of this work was to reliably identify odour-active compounds in dry-cured ham using powerful analysis methods for the volatile fraction. For this purpose, dynamic headspace gas chromatography combined with eight-way olfactometry using a panel of eight sniffers was used. One- and two-dimensional gas chromatography coupled with mass spectrometry and (or) olfactometry were also used. More than 600 compounds from the volatile fraction of dry-cured ham were identified and their biochemical origins are discussed. They covered a wide diversity of structures and chemical functions. Only 29 of them proved odour-active. Comparison of the results of GC–O analysis with those obtained by orthonasal sniffing of the dry-cured ham helped to gain a better understanding of how these substances contributed to the overall aroma of the product. Thus, “Fruity–Floral”, “Green–Vegetable” or “Plastic–Chemical” odours intensively perceived by GC–O have been poorly perceived by orthonasal sniffing. By contrast, “Animal–Meat products” or “Butter–Lactic–Cheesy” odours have been much better perceived by orthonasal sniffing. These results indicate that to understand the interactions between odour-active compounds, experimental doping with carefully selected odour-active compounds will be necessary.  相似文献   
10.
对微滤技术在乳品工业中的应用作以综述,经过低热膜技术处理生产的液态乳的风味与原料乳接近,货架期是一般制品的3~5倍。微生物的截留结果表明用该乳生产干酪的卫生指标与巴氏杀菌乳相当或者是更佳。微滤技术在乳品工业中的应用还包括:乳清的脱脂、干酪盐水的纯化等等,此外,最具前景的应用是分离酪蛋白生产干酪和脂肪的分离等。  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