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   539篇
  免费   14篇
  国内免费   3篇
电工技术   7篇
化学工业   85篇
金属工艺   19篇
机械仪表   12篇
建筑科学   21篇
能源动力   35篇
轻工业   49篇
水利工程   5篇
石油天然气   4篇
无线电   51篇
一般工业技术   138篇
冶金工业   37篇
原子能技术   25篇
自动化技术   68篇
  2024年   1篇
  2023年   5篇
  2022年   16篇
  2021年   19篇
  2020年   17篇
  2019年   21篇
  2018年   17篇
  2017年   14篇
  2016年   22篇
  2015年   10篇
  2014年   19篇
  2013年   33篇
  2012年   31篇
  2011年   38篇
  2010年   21篇
  2009年   29篇
  2008年   27篇
  2007年   25篇
  2006年   19篇
  2005年   11篇
  2004年   12篇
  2003年   9篇
  2002年   14篇
  2001年   11篇
  2000年   8篇
  1999年   3篇
  1998年   9篇
  1997年   5篇
  1996年   5篇
  1995年   4篇
  1994年   10篇
  1993年   9篇
  1992年   8篇
  1991年   4篇
  1990年   5篇
  1989年   1篇
  1988年   8篇
  1987年   3篇
  1986年   1篇
  1985年   5篇
  1984年   7篇
  1983年   7篇
  1982年   2篇
  1981年   4篇
  1980年   2篇
  1979年   3篇
  1977年   1篇
  1973年   1篇
排序方式: 共有556条查询结果,搜索用时 0 毫秒
31.
32.
Quantitative microscopy, texture and grain growth kinetic studies were made on swaged and recrystallized Ti-7.4 at. pct Al and Ti-15.2 at. pct Mo alloys. The quantitative microscopy studies indicated that the grain size distribution in both alloys is a constant for a given grain size, independent of annealing time and temperature and follows a log normal distribution. Moreover, there exists a range of grain sizes in space; the relative quantities of each size in the range varies with average grain size. Also, the grain shape factor decreases with increase in annealing time (grain size) at a constant temperature and with decrease in temperature for a constant grain size. The values of the shape factor for a given grain size and temperature were approximately the same for the two alloys. The quantitative microscopy features were essentially the same as those observed by Okazaki and Conrad for unalloyed titanium. The texture of the as-swaged Ti-7.4 at. pct Al wire specimens and the changes in this texture during grain growth were in accord with those previously reported for deformed and recrystallized titanium. The Ti-15.2 at. pct Mo alloy retained the deformation texture even after recrystallization. At 1/3 time law was found to hold for the grain growth over most of the grain sizevs time curve. The values of the activation energy for grain boundary migration were 25.2 Kcal/mole for the Ti-7.4 at. pct Al alloy and 29 Kcal/mole for the Ti-15.2 at. pct Mo alloy. These are similar to those for diffusion of Al and Mo in titanium, indicating that the diffusion of these substitutional elements controls the rate of boundary migration in these alloys. This paper is based on a presentation made at a symposium on “Recovery, Recrystallization and Grain Growth in Materials” held at the Chicago meeting of The Metallurgical Society of AIME, October 1977, under the sponsorship of the Physical Metallurgy Committee.  相似文献   
33.
In this paper an attempt is made to use a shell theory that includes transverse normal stresses to study the contact–impact behaviour involving thick shells. The problem is solved using the finite element method. The contact criterion is imposed by means of displacement and force constraints. The Lagrangian multipliers technique is used to impose these constraints. The case of a spherical shell impacting a rigid wall with a constant velocity is considered for the analysis. It is shown that the method produces accurate results with less amount of computation than the usual three-dimensional analyses. The effects of the thickness of shell, velocity of impact and modulus of the material are studied.  相似文献   
34.
Czapiewski  P. Ganesan  R. Volkert  D. Weber  B. 《Computer》1999,32(4):99-102
The process for producing bank checks is well established, and semi automated systems for doing so have been in place for several years. However, these legacy systems are now having difficulty meeting new customer demands. To support greater product variability and responsiveness to new customer requirements, our company (Deluxe Corp.) decided to reexamine its current process with an eye to increased automation. The resulting Post Press System replaced highly labor-intensive, inflexible check order processing and fulfillment with an approach that integrates flexible manufacturing with real time, object database concepts. Several months after initial deployment, the benefits of this integration are significant. Our company can process new orders more quickly, with higher accuracy, and at lower cost. The system also allows rapid order cancellation. Further, the new plastic wrap provides a tamper-evident package, a security feature of paramount importance to our clients. In addition, the PPS's modularity facilitates its rapid deployment in a new factory setting. Deluxe's investment in the PPS's design and deployment has been repaid in cost and time savings. The new architecture has laid the foundation for further manufacturing process automation-beyond order fulfillment and packaging. It provides an interface to new manufacturing technologies and helps Deluxe and its clients implement innovative marketing techniques  相似文献   
35.
The double-diffusive, free convective flow past a moving semi-infinite vertical cylinder has been studied numerically. The mass, momentum, energy, and species concentration equations have been solved by a finite-difference method using an implicit scheme of Crank-Nicolson type. The finite-difference scheme is unconditionally stable and accurate. Graphical results for the velocity, temperature, concentration, local and average skin friction, and Nusselt and Sherwood numbers are illustrated and discussed for various physical parametric values. The role of temperature stratification in the ambient medium has been analyzed. Published in Inzhenerno-Fizicheskii Zhurnal, Vol. 79, No. 1, pp. 72–76, January–February, 2006.  相似文献   
36.
In this work, a new rotational and scale invariant feature set for textural image classification, combined invariant feature (CIF) set has been introduced. It is an integration of the crude wavelets like Gaussian, Mexican Hat and orthogonal wavelets like Daubechies to achieve a high quality rotational and scale invariant feature set. Also it is added with features obtained using the newly proposed weighted smoothening Gaussian filter masks to improve the classification results. To reduce the effect of overlapping features, the variations among the feature set are analyzed and the eigenfeatures are extracted to produce good classification result.The rotational invariance is achieved by using these two wavelets with their directional properties and the scale invariance is achieved by a method, which is an extension to fractal dimension (FD) features. The first- and second-order statistical parameter and entropy characterize the quality of the features extracted. Furthermore, a comparison that shows the higher recognition rate achieved with the newly proposed method for the set of 6720 samples collected from 105 different textures of Brodatz, Vistek, Indezine databases and some additional images collected from other resources of indexed and true color images is shown.  相似文献   
37.
We present the preliminary results of temperature and frequency dependent dielectric measurements on Ba(Co1/3Nb2/3)O3 (BCN) thin films. These films were prepared on indium tin oxide (ITO) coated glass substrates by the pulse laser deposition (PLD) technique. It exhibits single-phase hexagonal symmetry. These films were irradiated with Ag15+ (200 MeV) and O7+ (100 MeV) beams at the fluence 1 × 1011, 1 × 1012, and 1 × 1013 ions/cm2. On irradiating these films, its dielectric constant (?′) and dielectric loss (tan δ) parameters improve compared to un-irradiated film. Compared to O7+ irradiation induced point/cluster defects Ag15+ induced columnar defects are more effective in reducing/pinning trapped charges within grains. The present paper highlights the role of swift heavy ion irradiation in engineering the dielectric properties of conductive samples to enable them to be useful for microwave device applications.  相似文献   
38.
39.
Primary liver cancer is a heterogeneous disease. Liver cancer metabolism includes both the reprogramming of intracellular metabolism to enable cancer cells to proliferate inappropriately and adapt to the tumor microenvironment and fluctuations in regular tissue metabolism. Currently, metabolomics and metabolite profiling in liver cirrhosis, liver cancer, and hepatocellular carcinoma (HCC) have been in the spotlight in terms of cancer diagnosis, monitoring, and therapy. Metabolomics is the global analysis of small molecules, chemicals, and metabolites. Metabolomics technologies can provide critical information about the liver cancer state. Here, we review how liver cirrhosis, liver cancer, and HCC therapies interact with metabolism at the cellular and systemic levels. An overview of liver metabolomics is provided, with a focus on currently available technologies and how they have been used in clinical and translational research. We also list scalable methods, including chemometrics, followed by pathway processing in liver cancer. We conclude that important drivers of metabolomics science and scientific technologies are novel therapeutic tools and liver cancer biomarker analysis.  相似文献   
40.
Potential drug toxicities and drug interactions of redundant compounds of plant complexes may cause unexpected clinical responses or even severe adverse events. On the other hand, super-additivity of drug interactions between natural products and synthetic drugs may be utilized to gain better performance in disease management. Although without enough datasets for prediction model training, based on the SwissSimilarity and PubChem platforms, for the first time, a feasible workflow of prediction of both toxicity and drug interaction of plant complexes was built in this study. The optimal similarity score threshold for toxicity prediction of this system is 0.6171, based on an analysis of 20 different herbal medicines. From the PubChem database, 31 different sections of toxicity information such as “Acute Effects”, “NIOSH Toxicity Data”, “Interactions”, “Hepatotoxicity”, “Carcinogenicity”, “Symptoms”, and “Human Toxicity Values” sections have been retrieved, with dozens of active compounds predicted to exert potential toxicities. In Spatholobus suberectus Dunn (SSD), there are 9 out of 24 active compounds predicted to play synergistic effects on cancer management with various drugs or factors. The synergism between SSD, luteolin and docetaxel in the management of triple-negative breast cancer was proved by the combination index assay, synergy score detection assay, and xenograft model.  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