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   227篇
  免费   3篇
  国内免费   1篇
电工技术   1篇
化学工业   22篇
金属工艺   5篇
机械仪表   3篇
建筑科学   10篇
能源动力   12篇
轻工业   80篇
无线电   11篇
一般工业技术   46篇
冶金工业   21篇
原子能技术   1篇
自动化技术   19篇
  2021年   2篇
  2018年   5篇
  2016年   3篇
  2015年   5篇
  2014年   3篇
  2013年   22篇
  2012年   5篇
  2011年   11篇
  2010年   9篇
  2009年   11篇
  2008年   5篇
  2007年   2篇
  2006年   3篇
  2004年   6篇
  2003年   5篇
  2001年   2篇
  1999年   2篇
  1998年   10篇
  1997年   7篇
  1996年   13篇
  1995年   5篇
  1994年   10篇
  1993年   6篇
  1992年   3篇
  1991年   4篇
  1990年   4篇
  1989年   2篇
  1988年   4篇
  1987年   4篇
  1986年   3篇
  1985年   4篇
  1984年   6篇
  1983年   3篇
  1981年   5篇
  1980年   2篇
  1979年   2篇
  1978年   8篇
  1977年   3篇
  1972年   1篇
  1971年   1篇
  1969年   2篇
  1968年   2篇
  1967年   1篇
  1966年   1篇
  1963年   1篇
  1961年   1篇
  1960年   1篇
  1947年   1篇
  1946年   2篇
  1943年   1篇
排序方式: 共有231条查询结果,搜索用时 15 毫秒
1.
Ice recrystallization rates in simple aqueous solutions comprising fructose and a hydrocolloid stabilizer were measured. The stabilizers were an enzyme-modified guar and a non-gelling high methoxy pectin. The stabilizer concentration dependence of the recrystallization rates for both materials was similar in that increasing the concentration resulted in decreasing rates until a point is reached where further addition had no additional effect. That recrystallization rates were reduced by both gelling and non-gelling stabilizers was strongly suggestive that gelation was not a requirement for recrystallization inhibition and another more specific mechanism applies, for example a weak interfacial effect such as adsorption or blocking. This behavior was also seen with locust bean gum and guar and provided further empirical evidence to support the hypothesis that stabilizers adsorb to ice crystal surfaces.  相似文献   
2.
Image segmentation towards new image representation methods   总被引:1,自引:0,他引:1  
Very low bit-rate video coding has recently become one of the most important areas of image communication and a large variety of applications have already been identified. Since conventional approaches are reaching a saturation point, in terms of coding efficiency, a new generation of video coding techniques, aiming at a deeper “understanding” of the image, is being studied. In this context, image analysis, particularly the identification of objects or regions in images (segmentation), is a very important step. This paper describes a segmentation algorithm based on split and merge. Images are first simplified using mathematical morphology operators, which eliminate perceptually less relevant details. The simplified image is then split according to a quad tree structure and the resulting regions are finally merged in three steps: merge, elimination of small regions and control of the number of regions.  相似文献   
3.
The Voronoi diagram (VD) is a popular tool for partitioning the support of an image. An algorithm is presented for constructing VD when the seed set, which determines the Voronoi regions, can be modified by adding and removing seeds. The number of pixels and seeds revisited for updating the diagram and the neighbor relationships among seeds is minimized. A result on cocircular seeds is presented. The adjacency, or dual, graph of the VD is readily obtained. The use of the algorithm for constructing skeletons by influence zones (SKIZ) is demonstrated  相似文献   
4.
测定了庚烯-(3)的蒸气压。用Gillespie型平衡器测定了甲苯—庚烯-(3)、正庚烷—庚烯-(3)二元系及甲苯—正庚烷—庚烯-(3)三元系统的平衡数据,并分别用Spinner及White方法验证了这些数据,计算结果与实验结果是符合的。三元系统气液平衡的数据不论在工程中或是实验工作上都很重要,过去对三元系统气液平衡的研究虽然有一些,但对甲苯—正庚烷—庚烯-(3)三元系统气液平衡至今在文献上尚未有记载。 由于庚烯-(3)的蒸气压数据不见于文献,我们测定了它的蒸气压数据。正庚烷—甲苯二元系统前人已有许多结果发表,我们进行了一些校核,结果与文献记载符合。甲苯—庚烯-(3)二元系统文献上没有,我们倣效了并用Spinner方法及White方法整理。至于正庚烷—庚烯-(3)二元系统,因为此两组分的性质(如沸点、n_D~(20)等)极其接近,分析误差较大,我们将其当作理想溶液处理,误差当在允许误差以内。 三元系统的分析较为繁难,误差也较大,故希望从理论和实验材料找出其规律性,以校核实验数据和推算未知三元系统。本工作利用三个二元系统的数据,用Spinner以及White的方法推算三元系统的气液平衡,与实验数据相比较,是相互符合的。  相似文献   
5.
1 INTRODUCTIONIn recent years, the application of the roomtemperature type ( < 100 ℃) polymer electrolytemembrane fuel cells(PEMFCs) as a primary powersource in electric vehicles and portable equipmentsetc has received increasing attention[1 4]. Usuallyin a PEMFC system, platinum is chosen as the e lectrode electrocatalyst, however, it results in ahigh cost PEMFC system for commercialization be cause Pt is a high cost, source limit metal. So,looking fo…  相似文献   
6.
    
Rietveld analysis of powder neutron diffraction pattern recorded on Sr-based 1201-phase superconductor (T c =53 K), (Hg0.7Cr0.3)Sr2CuO4+ shows that the oxygen atoms at O(3) site are disordered atx=y=0.3712. This fourfold split site has a total combined occupancy of 80% and is the only occupied site in the (Hg, Cr)O plane.  相似文献   
7.
The dialysis patient is prone to elevations in the calcium phosphorus product and hyperparathyroidism, which contributes to valvular and vascular calcification. We present the case of a young lady on chronic dialysis that developed mitral calcification complicated by severe mitral stenosis, caseous calcification and retinal embolization. She subsequently required mitral valve replacement.  相似文献   
8.
This paper presents a number of ongoing projects that will be valuable to the development of technologies for digital theatre and performance. This paper describes an EU ACTS project called RESOLV which develops an integrated system to capture real 3D environments using laser and video. Current research on motion tracking, statistical behaviour modelling and simulation is presented, and possible applications, both for visual augmentation and audio generation, are discussed. The projects presented were not originally designed in the domain of theatre and performance, however their results and output seem to be well suited to be applied in this area.  相似文献   
9.
ABSTRACT

The object of the present paper is to explore the possibility of using simulated annealing procedures to determine multi-speed three phase windings. It is limited to the very simple case of p/2p polarities. The program has yielded the very well known solutions; thus, research may proceed towards more difficult problems.  相似文献   
10.
Exposure to sunlight is the major cause of skin cancer. Ultraviolet radiation (UV) from the sun causes damage to DNA by direct absorption and can cause skin cell death. UV also causes production of reactive oxygen species that may interact with DNA to indirectly cause oxidative DNA damage. UV increases accumulation of p53 in skin cells, which upregulates repair genes but promotes death of irreparably damaged cells. A benefit of sunlight is vitamin D, which is formed following exposure of 7-dehydrocholesterol in skin cells to UV. The relatively inert vitamin D is metabolized to various biologically active compounds, including 1,25-dihydroxyvitamin D3. Therapeutic use of vitamin D compounds has proven beneficial in several cancer types, but more recently these compounds have been shown to prevent UV-induced cell death and DNA damage in human skin cells. Here, we discuss the effects of vitamin D compounds in skin cells that have been exposed to UV. Specifically, we examine the various signaling pathways involved in the vitamin D-induced protection of skin cells from UV.  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