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   1427篇
  免费   70篇
  国内免费   7篇
电工技术   13篇
综合类   2篇
化学工业   410篇
金属工艺   57篇
机械仪表   38篇
建筑科学   43篇
矿业工程   1篇
能源动力   35篇
轻工业   162篇
水利工程   4篇
石油天然气   2篇
无线电   150篇
一般工业技术   276篇
冶金工业   56篇
原子能技术   10篇
自动化技术   245篇
  2024年   1篇
  2023年   17篇
  2022年   29篇
  2021年   57篇
  2020年   31篇
  2019年   33篇
  2018年   28篇
  2017年   34篇
  2016年   57篇
  2015年   41篇
  2014年   65篇
  2013年   104篇
  2012年   124篇
  2011年   94篇
  2010年   91篇
  2009年   92篇
  2008年   85篇
  2007年   61篇
  2006年   69篇
  2005年   54篇
  2004年   40篇
  2003年   38篇
  2002年   40篇
  2001年   14篇
  2000年   22篇
  1999年   15篇
  1998年   24篇
  1997年   19篇
  1996年   23篇
  1995年   16篇
  1994年   17篇
  1993年   10篇
  1992年   5篇
  1991年   9篇
  1990年   10篇
  1989年   5篇
  1988年   3篇
  1987年   2篇
  1986年   3篇
  1985年   4篇
  1984年   1篇
  1983年   1篇
  1982年   4篇
  1980年   1篇
  1979年   2篇
  1977年   2篇
  1976年   4篇
  1975年   1篇
  1973年   1篇
  1968年   1篇
排序方式: 共有1504条查询结果,搜索用时 8 毫秒
171.
Real Time Fitting of Hand-Sketched Pressure Brushstrokes   总被引:1,自引:0,他引:1  
A method is described for fitting the outline of hand-sketched pressure brushstrokes with Bézier curves. It combines the brush-trajectory model, in which a stroke is generated by dragging a brush along a given trajectory, with a fast curve fitting algorithm. The method has been implemented for a vector-based drawing program in which the user draws with a cordless pressure-sensitive stylus on a digitizing tablet. From the trajectory followed by the stylus, its associated pressure data, and a specified brush, a stroke of variable width is computed and displayed in real time. First, the digitized trajectory is fitted, thus removing noise. Then, from polygonal approximations of the fitted trajectory and the brush outline, a polygonal approximation of the stroke outline is computed. Working with polygonal approximations reduces computations to simple geometric operations and greatly simplifies the treatment of dynamic, pressure-controlled brushes. Last, the polygonal approximation of the stroke outline is fitted. The result is a closed piecewise Bézier curve approximating the brushstroke outline to within an arbitrary error tolerance. Several examples of hand-sketched drawings realized with this method are presented.  相似文献   
172.
A semi-conducting phosphovanadate glass was tested as a possible material for positive electrode in solid state batteries.O.c. voltage with alkali metal (3.6 V/Li and 3.4 V/Na) is higher than for crystallized vanadium oxides and chemical intercalation of sodium or lithium is obtained using halogenated salts dissolved in organic solvents.  相似文献   
173.
A histological and ultrastructural study was conducted to characterize changes in beef muscle structure after heating. Pieces of rectus abdominis muscle were heated at 100 °C over varying time frames from 15 min to 60 min and at 270 °C for 1 min; samples were then prepared for optical and transmission electron microscopy. After 15 min of heating, at 100 °C, a lateral shrinkage in fibre of 48% and an increase in gaps between the myofibrillar masses of 27% was noted. No more significant evolution was observed as heating duration escalated. The ultrastructure showed strong myofibril to sarcolemma detachments in which granular aggregates, coming in part from myofibrillar proteins, are stored. Neighbouring muscle fibres showed strong heterogeneity in morphological behaviour after thermal treatment, suggesting that differences in composition and structure of the cytoskeleton proteins in the different fibres can cause denaturation/shrinkage of the proteins at different times along the timescale of microstructural changes during heating. Short heating at high temperatures expanded the gaps between myofibrillar mass, but the overall changes in the ultrastructure were similar to those obtained when heating at 100 °C.  相似文献   
174.
Although cultivation of Arabica coffee trees at high elevation is known to favourably affect the final quality of the beverage, quantitative data describing the influence of climatic conditions on the chemical composition of the seed are still lacking. Similarly, post-harvest treatments of the beans are known to affect the generation of flavour, but the chemical transformations that occur during wet processing are poorly understood. To better characterise the effects of the environment, wet processing and their possible interactions, we quantified the changes in the main chemical components of the coffee seed (lipids, chlorogenic acids, sugars and caffeine) caused by wet processing, and analysed how these changes were affected by the variations induced by the environment before harvest. Using 16 experimental plots in Reunion Island displaying broad climatic variations, we showed that chlorogenic acids and fatty acids in the seed were controlled by the mean air temperature during seed development. By contrast, total lipid, total soluble sugar, total polysaccharide and total chlorogenic acid contents were not influenced by climate. Glucose content was positively affected by altitude, while sorbitol content after wet processing depended directly on the glucose content in fresh seeds.  相似文献   
175.
New and improved : The incorporation of a 6‐chlorotryptophan (6‐Cl‐Trp) into a β‐peptide (M)‐314 helix leads to a high‐affinity hDM2 inhibitor, as demonstrated by fluorescence fluctuation analysis at single molecule resolution. When conjugated to penetratin, the newly derived hDM2 binder specifically inhibits tumour cell growth in vitro.

  相似文献   

176.
We report on the gelation capability of polystyrene/poly(2-vinyl pyridine) amphiphilic heteroarm polyelectrolyte stars in acidic salt-free aqueous media. The star polymers associate through hydrophobic interactions, by retraction of the stretched arms under no interdigitation conditions, in the dilute regime forming colloidal soft nanoparticles comprising about 6 stars, At concentrations significantly higher than the hydrodynamic overlap concentration (c > 40c), the crowding of the colloidal nanoparticles drives a jamming transition, leading to a colloidal gel. The intermediate overlap regime (c < c < 40c) is characterized by a significant compaction of the polyelectrolyte entities prior interdigitation and jamming.  相似文献   
177.
Subtype‐selective ligands are of great interest to the scientific community, as they provide a tool for investigating the function of one receptor or transporter subtype when functioning in its native environment. Several 4‐substituted (S)‐glutamate (Glu) analogues were synthesized, and altogether this approach has provided important insight into the structure–activity relationships (SAR) for ionotropic and metabotropic glutamate receptors (iGluRs and mGluRs), as well as the excitatory amino acid transporters (EAATs). In this work, three 4,4‐disubstituted Glu analogues 1 – 3 , which are hybrid structures of important 4‐substituted Glu analogues 4 – 8 , were investigated at iGluRs and EAATs. Collectively, their pharmacological profiles add new and valuable information to the SAR for the iGluRs and EAAT1–3.  相似文献   
178.
Emir Hammami  Thierry Villemur 《电信纪事》2006,61(11-12):1369-1402
Application deployment in sessions composed of several users is now a hot topic. These users communicate together with heterogeneous terminals. Deployed applications on these nodes must fit to the execution environment and must be interoperable with applications already installed on the others nodes of the session. In this paper, we propose an architecture, which provides a user with missing applications according to the session requirements while respecting compatibility and interoperability constraints. This decentralized and distributed architecture is based on a context-aware deployment algorithm running on each node. After discovering applications scattered on a peer-to-peer network, the algorithm generates deployment configurations needed for any deployment node. Then, the algorithm performs the necessary downloads and instantiations. We present our context-aware deployment platform composed of generic modules. These modules includeApis to build deployment services according to this architecture.  相似文献   
179.
The long-term behavior of high-level nuclear glass subjected to alpha/beta radiation by long-life radionuclides must be investigated with respect to geological disposal. This study focuses on the effects of alpha and beta radiations on the chemical reactivity of R7T7 glass with pure water, mainly on the residual alteration rate regime. Glass specimens doped with 0.85 wt% 239PuO2 (α emitter) and 0.24 wt% 99TcO2 (β emitter) that simulate alpha and beta dose rate corresponding to long-term disposal conditions are leached under static conditions in argon atmosphere at 90°C, in initially pure water and at a high surface-area-to-volume ratio (S/V = 20/cm). The alteration rate is monitored by the release of glass alteration tracer elements (B, Na, and Li). Radiation effects on the leached glass and its gel network are characterized by SEM and TEM analyses. Plutonium and technetium releases are also measured by radiometry, and their chemical oxidation state is assessed by measuring the pH and reduction–oxidation potential of the leachates. The results do not highlight any significant effect of alpha/beta radiation on the residual alteration of these doped glasses. These observations are consistent with solid characterizations, which show that a protective layer can be formed under such irradiation fields. Under our experimental conditions (Eh~380 mV/SHE, pH90°C = 8–8.6), very low concentrations of soluble plutonium are measured in the leachate, indicating strong plutonium retention, whereas technetium performs as a soluble element and is not retained in the altered layer.  相似文献   
180.
Silicon nanowires (SiNWs) were grown on Si(1 0 0) and Si(1 1 1) substrates by chemical vapour deposition (CVD) via the vapour–liquid–solid (VLS) mechanism with small gold particles used as seeds. In order to control the diameter of nanowires, their density on the substrate and their orientation we controlled the size and the distribution of Au seed particles. This was accomplished using nanosphere lithography (NSL) by which regular arrays of Au nanoparticles can be generated. This allowed us to grow single-crystalline SiNWs perpendicular to the surface of Si(1 1 1) substrates. The SiNWs and their Au caps were studied with respect to their morphology and composition using TEM, HREM and EFTEM methods. Clusters of Au are observed along the surface of SiNWs and the existence of a thin Si film on gold particles capping the SiNWs is demonstrated.  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