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   1493篇
  免费   100篇
  国内免费   105篇
电工技术   9篇
综合类   41篇
化学工业   73篇
金属工艺   23篇
机械仪表   16篇
建筑科学   167篇
矿业工程   19篇
能源动力   60篇
轻工业   167篇
水利工程   118篇
石油天然气   627篇
武器工业   5篇
无线电   62篇
一般工业技术   64篇
冶金工业   31篇
原子能技术   27篇
自动化技术   189篇
  2023年   15篇
  2022年   37篇
  2021年   39篇
  2020年   46篇
  2019年   51篇
  2018年   51篇
  2017年   46篇
  2016年   57篇
  2015年   60篇
  2014年   65篇
  2013年   108篇
  2012年   96篇
  2011年   141篇
  2010年   115篇
  2009年   87篇
  2008年   58篇
  2007年   99篇
  2006年   77篇
  2005年   74篇
  2004年   62篇
  2003年   61篇
  2002年   31篇
  2001年   37篇
  2000年   31篇
  1999年   23篇
  1998年   33篇
  1997年   18篇
  1996年   11篇
  1995年   5篇
  1994年   10篇
  1993年   7篇
  1992年   9篇
  1991年   4篇
  1989年   9篇
  1988年   1篇
  1987年   2篇
  1986年   6篇
  1985年   2篇
  1984年   2篇
  1983年   2篇
  1982年   2篇
  1981年   6篇
  1980年   1篇
  1975年   1篇
排序方式: 共有1698条查询结果,搜索用时 15 毫秒
71.
Previous studies reported coastal trapped waves (CTWs) in the Caspian Sea (CS). This study deals with the generation mechanisms, the temporal and spatial variability of CTWs in this area, and their transformations during propagation from the origin to the destination using recent measurements and high-resolution numerical simulations. CTWs are observed at all stations with periods of 2–6 days after northerly storms. The Absheron Peninsula, old Sefidrud delta, and Nur coasts were identified as the CTWs prone regions. The generation of CTWs in these locations was confirmed using numerical experiments. The propagation away from the generating location of CTWs was analyzed using a representative real wind storm. In the west part of the CS, the generation mechanism of CTWs is mainly similar to the barotropic Kelvin waves; in contrast, it is similar to the continental shelf waves in the southern shelves. The results can be used to study the contribution of generated CTWs to the transport of sediment and biological materials in all large lakes.  相似文献   
72.
The interaction between the low-frequency atmospheric oscillation(Madden-Julian Oscillation,MJO) and the diabatic heating over the Qinghai-Xizang Plateau(QXP) from March to June is analyzed.The results show that there are respectively two and one wave trains around the QXP during the onset of the South China Sea monsoon in strong and weak monsoon years.The locations and strength of the wave train propagation differ between the strong and weak monsoon years.Because diabatic heating of the QXP prevents the lo...  相似文献   
73.
An operational model for tracking surface objects in the ocean is presented. Contrary to most of traditional Lagrangian Particle Tracking Algorithms, the presented approach computes the probability density function from the final position of a set of neutrally buoyant particles deployed in the flow providing the area of accumulated probability. The model departs from daily predictions of ocean surface currents, winds and waves provided by an Operational Forecasting System, and integrates the Eulerian velocities to obtain the trajectory of each particle forward in time. A random walk term is added to simulate numerical diffusivity. Several tests are performed in order to determine the optimal numerical scheme as well as the computational time step. To show the performance of the model we simulate the trajectories of a set of SVP-drifters deployed in the Balearic Sea. For these experiments, the final position of the drifters laid within the modeled contour of 50% of accumulated probability for the first 24 h forecast.  相似文献   
74.
In this paper, a complex nonlinear autoregressive conditional heteroscedasticity (CNARCH) model is proposed to model sea clutter. For heteroscedastic model, since the likelihood function is not obtained from explicit probability density function (PDF) expression, it is typically referred to as a quasi-likelihood function. The corresponding quasi-maximum likelihood estimation (QMLE) of the model parameters is derived. Furthermore, the corresponding detection algorithm is derived based on this model. We also conduct the simulations of both synthetic and practical data, demonstrate that the proposed model offers higher accuracy in detection, than the linear ARCH model, when used in the sea clutter.  相似文献   
75.
内陆核电厂冷却塔的环境影响预测计算   总被引:2,自引:0,他引:2  
内陆核电厂通常采用自然通风冷却塔作为散热系统,电厂余热主要通过冷却水释放到大气环境中,由此带来的环境影响包括雾羽、荫屏、盐沉积、噪声等。本文基于美国核管会(NRC)推荐的SACTI计算程序,给出了评价冷却塔造成上述环境影响的计算模式和方法;采用此程序,对我国湖南、湖北和安徽三个拟选内陆核电厂厂址的冷却塔环境影响进行了预测计算,并与美国GGNS电厂的相关计算结果进行了类比分析。  相似文献   
76.
Despite a distinguished heritage of learning in the Middle East, the expansion of provision for higher education is currently at an unprecedented scale. The Gulf States, in particular, are seeking to keep up with accelerated population growth and a demographic ‘youth bulge’. Guest-Editor Kevin Mitchell describes the architectural approaches employed in the design of institutions in the region from the first universities in Saudi Arabia to Foster + Partners's ground-breaking sustainable design for the Masdar Institute in Abu Dhabi and future projects.  相似文献   
77.
The paper reports an assessment of the soil and water in the coastal strip between Marsa Alam and Shalateen at the southern part of the Red Sea coast of Egypt. There is limited potential for agricultural development. There is a need for water re-use and some potential for tourism.  相似文献   
78.
A project to link the Dead Sea to the Red Sea via a canal is undergoing extensive study. This project will transform the physical and chemical characteristics of the Sea and therefore has significant environmental impacts. The predicted behaviour of the Dead Sea with a canal project was examined in this study, and the environmental impacts were then identified and classified into positive and negative. The main positive impact of the canal is the restoration of the Dead Sea into its 1930s level, and the improvement in life quality in the area. Negative impacts include the risk of groundwater contamination, the re-establishment of stratification condition, seasonal precipitation of chemicals, and the growth of micro-organisms in the Sea.  相似文献   
79.
海洋浪花飞溅区混凝土硫酸盐侵蚀试验研究   总被引:1,自引:0,他引:1  
对混凝土试件进行海边暴露试验,研究海边浪花飞溅区域混凝土硫酸盐侵蚀试验,利用分光光度计法测定硫酸根离子的含量。试验结果表明,混凝土中总硫酸根离子浓度随着腐蚀龄期的增加而升高,但后期增加幅度逐渐降低;混凝土中总硫酸根离子浓度因水胶比、水泥用量不同而不同;掺加矿物掺合料可以明显改善混凝土的抗硫酸盐侵蚀能力。  相似文献   
80.
徐久婷 《福建建筑》2013,(2):7-9,55
经济开发区建设对国民经济发展有着不可忽视的作用,搞好经济开发区建设首先必须做好规划,这对内陆山区尤其重要。本文以福建省内陆山区邵武市经济开发区为例,分析探讨内陆山区经济开发区规划应注重城乡协调,提升功能定位;注重区域整合,创新规划理念;注重空间布局,强化发展时序,力求探索内陆山区经济开发区的规划理念与途径。  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