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   8416篇
  免费   189篇
  国内免费   10篇
电工技术   96篇
综合类   13篇
化学工业   1757篇
金属工艺   137篇
机械仪表   108篇
建筑科学   485篇
矿业工程   47篇
能源动力   208篇
轻工业   802篇
水利工程   109篇
石油天然气   38篇
无线电   511篇
一般工业技术   1167篇
冶金工业   2124篇
原子能技术   95篇
自动化技术   918篇
  2022年   81篇
  2021年   120篇
  2020年   98篇
  2019年   97篇
  2018年   107篇
  2017年   108篇
  2016年   123篇
  2015年   109篇
  2014年   164篇
  2013年   434篇
  2012年   281篇
  2011年   354篇
  2010年   280篇
  2009年   305篇
  2008年   363篇
  2007年   349篇
  2006年   309篇
  2005年   261篇
  2004年   232篇
  2003年   238篇
  2002年   212篇
  2001年   147篇
  2000年   142篇
  1999年   142篇
  1998年   123篇
  1997年   121篇
  1996年   115篇
  1995年   140篇
  1994年   133篇
  1993年   124篇
  1992年   133篇
  1991年   91篇
  1990年   108篇
  1989年   123篇
  1988年   116篇
  1987年   113篇
  1986年   117篇
  1985年   146篇
  1984年   135篇
  1983年   118篇
  1982年   133篇
  1981年   126篇
  1980年   93篇
  1979年   124篇
  1978年   120篇
  1977年   103篇
  1976年   87篇
  1975年   84篇
  1974年   90篇
  1973年   99篇
排序方式: 共有8615条查询结果,搜索用时 9 毫秒
41.
We present a fully automatic arm and hand tracker that detects joint positions over continuous sign language video sequences of more than an hour in length. To achieve this, we make contributions in four areas: (i) we show that the overlaid signer can be separated from the background TV broadcast using co-segmentation over all frames with a layered model; (ii) we show that joint positions (shoulders, elbows, wrists) can be predicted per-frame using a random forest regressor given only this segmentation and a colour model; (iii) we show that the random forest can be trained from an existing semi-automatic, but computationally expensive, tracker; and, (iv) introduce an evaluator to assess whether the predicted joint positions are correct for each frame. The method is applied to 20 signing footage videos with changing background, challenging imaging conditions, and for different signers. Our framework outperforms the state-of-the-art long term tracker by Buehler et al. (International Journal of Computer Vision 95:180–197, 2011), does not require the manual annotation of that work, and, after automatic initialisation, performs tracking in real-time. We also achieve superior joint localisation results to those obtained using the pose estimation method of Yang and Ramanan  (Proceedings of the IEEE conference on computer vision and pattern recognition, 2011).  相似文献   
42.
In recent years research on the electrowinning of copper has led to a number of significant advances. These developments include improved mass transfer and higher current density operation through air sparging, reduced anode overvoltage in the conventional cell as a result of cobalt(II) addition to the electrolyte or the use of alternative types of anodes, and the production of high quality cathodes in the electrowinning of copper from solvent extraction strip liquor. The fluidized-bed cathode offers the possibility of continuous electrowinning as well as the direct electrowinning of copper from dilute solutions. The problem of high power consumption may find its solution in the adoption of an alternate anode reaction or in the electrowinning of copper (I) electrolytes. Noteworthy is the development of unique electrowinning cells in conjunction with the hydrometallurgical treatment of copper concentrates. These cells utilize cuprous or ferrous anodic oxidation with the resulting cupric or ferric ions being active lixiviants of sulphide copper minerals. The numerous advances combined with the increasing tonnage of copper being produced by the electrowinning route ensure an interesting and promising future for this process.  相似文献   
43.
Pre-concentration of dilute aqueous solutions by hydrate formation can improve the effective distribution coefficient and selectivity of solvent extraction. Many solvents can serve simultaneously to promote solution concentration by hydrate formation and also to extract non-polar solutes from the resulting concentrated solution. This concept is illustrated for systems with supercritical ethylene and with near-critical liquid carbon dioxide, and its application to conventional solvents is discussed.  相似文献   
44.
Adsorbate interactions and reactions on metal surfaces have been investigated using scanning tunneling microscopy. The manners in which adsorbates perturb the surface electronic structure in their vicinity are discussed. The effects these perturbations have on other molecules are shown to be important in overlayer growth. Interactions of molecules with surface steps are addressed, and each molecule's electron affinity is shown to dictate its adsorption sites at step edges. Standing waves emanating from steps are demonstrated to effect transient molecular adsorption up to 40 A away from the step edge. Halobenzene derivatives are used to demonstrate how the surface is important in aligning reactive intermediates.  相似文献   
45.
Multi‐view reconstruction aims at computing the geometry of a scene observed by a set of cameras. Accurate 3D reconstruction of dynamic scenes is a key component for a large variety of applications, ranging from special effects to telepresence and medical imaging. In this paper we propose a method based on Moving Least Squares surfaces which robustly and efficiently reconstructs dynamic scenes captured by a calibrated set of hybrid color+depth cameras. Our reconstruction provides spatio‐temporal consistency and seamlessly fuses color and geometric information. We illustrate our approach on a variety of real sequences and demonstrate that it favorably compares to state‐of‐the‐art methods.  相似文献   
46.
The influence of silica support on the α-olefins, internal olefins and branched hydrocarbon selectivities of the gasoline range products of a precipitated iron catalyst in the Fischer-Tropsch synthesis was investigated. Three catalysts with varying silica content and constant promoter content were studied. It was found that there is a linear relationship between the silica content of the catalysts and the internal olefin and branched hydrocarbon product selectivities. The selectivities of the aromatic and alcohol products remain relatively constant, indicating that the production of these two groups of compounds is not affected by the presence of silica support in the catalysts.  相似文献   
47.
Reaction of 2,3,4,5-tetramethylcyclopent-2-enone (1) withp-LiC6H4OC-Me2OMe, followed by treatment with aqueous acid afforded 1-(p-hydroxyphenyl)-2,3,4,5-tetramethylcyclopentadiene (2). This new ligand was then used in the synthesis of the functionally substituted organomolybdenum reagent (5-C5Me4-p-C6H5OH)Mo(CO)2(NO) (3). Treatment of a preformed 1/1 styrene/maleic anhydride copolymer ( ) with 5 mol% 3 led to chemical incorporation of the organometallic species into the polymer. The final product contained 3 mol% of the organometallic moiety.  相似文献   
48.
The effect of the temperature of gas phase CO upon the kinetics of the oxygen titration reaction: COg +Oa CO2,g, has been studied. It is found that the reaction's rate is independant of CO gas temperature between 300 and 623 K. The activation energy (6.5 kcal/mole), dependence upon CO pressure (first-order), and independence upon oxygen coverage for 0.1 o 0.4 are all independant of the CO gas phase temperature. This result rules out any Eley-Rideal type mechanism whereby CO reacts directly from the gas phase with an oxygen adatom without first being accommodated to the surface temperature in an absorbed state. The result is instead interpretable in terms of a Langmuir-Hinshelwood mechanism.Camille and Henry Dreyfus Foundation Teacher-Scholar Fellowship.  相似文献   
49.
This paper mainly focuses on the principle component analysis (PCA) and its applications on vision based computing. The underlying mechanism of PCA given and several significant factors, involved with subspace training are discussed theoretically in detail including principle components energy, residuals assessment, and decomposition computation. The typical extensions, including probabilistic PCA (PPCA), kernel PCA (KPCA), multi-dimensional PCA and robust PCA (RPCA), have been presented with critical analysis on both mechanisms and computations. Combining with the studies on, such as, image compression, visual tracking, image recognition and super-resolution image reconstruction, PCA and its extensions applied to computer vision are critically reviewed and evaluated on the targeted issues in each application as well as the role they played at specific tasks to the characteristics, cost and suitable situations of each PCA based vision processing technique.  相似文献   
50.
Inspired by applications in parallel computing, we analyze the setting of work stealing in multithreaded computations. We obtain tight upper bounds on the number of steals when the computation can be modeled by rooted trees. In particular, we show that if the computation with n processors starts with one processor having a complete k-ary tree of height h (and the remaining n ? 1 processors having nothing), the maximum possible number of steals is \({\sum }_{i=1}^{n}(k-1)^{i}\binom {h}{i}\).  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