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   1495篇
  免费   539篇
  国内免费   130篇
电工技术   46篇
技术理论   1篇
综合类   113篇
化学工业   238篇
金属工艺   41篇
机械仪表   74篇
建筑科学   460篇
矿业工程   80篇
能源动力   85篇
轻工业   36篇
水利工程   109篇
石油天然气   219篇
武器工业   89篇
无线电   145篇
一般工业技术   145篇
冶金工业   69篇
原子能技术   21篇
自动化技术   193篇
  2023年   18篇
  2022年   67篇
  2021年   155篇
  2020年   109篇
  2019年   125篇
  2018年   79篇
  2017年   97篇
  2016年   69篇
  2015年   62篇
  2014年   117篇
  2013年   172篇
  2012年   201篇
  2011年   185篇
  2010年   137篇
  2009年   130篇
  2008年   73篇
  2007年   110篇
  2006年   77篇
  2005年   46篇
  2004年   12篇
  2003年   13篇
  2002年   11篇
  2001年   13篇
  2000年   5篇
  1999年   5篇
  1998年   11篇
  1997年   2篇
  1996年   9篇
  1995年   5篇
  1994年   3篇
  1993年   3篇
  1992年   2篇
  1991年   1篇
  1990年   2篇
  1988年   10篇
  1987年   8篇
  1986年   15篇
  1985年   3篇
  1979年   1篇
  1951年   1篇
排序方式: 共有2164条查询结果,搜索用时 78 毫秒
1.
Clip-art image segmentation is widely used as an essential step to solve many vision problems such as colorization and vectorization. Many of these applications not only demand accurate segmentation results, but also have little tolerance for time cost, which leads to the main challenge of this kind of segmentation. However, most existing segmentation techniques are found not sufficient for this purpose due to either their high computation cost or low accuracy. To address such issues, we propose a novel segmentation approach, ECISER, which is well-suited in this context. The basic idea of ECISER is to take advantage of the particular nature of cartoon images and connect image segmentation with aliased rasterization. Based on such relationship, a clip-art image can be quickly segmented into regions by re-rasterization of the original image and several other computationally efficient techniques developed in this paper. Experimental results show that our method achieves dramatic computational speedups over the current state-of-the-art approaches, while preserving almost the same quality of results.  相似文献   
2.
Integrated watershed management is required to ensure the reasonable use of resources and reconcile interactions among natural and human systems. In the present study, an interval fuzzy multiobjective programming (IFMOP) method was used to solve an integrated watershed management problem. Based on system analysis, an IFMOP model suitable for a lake watershed system {IFMOPLWS} was developed and applied to the Lake Qionghai watershed in China. Scenario analysis and an interactive approach were used in the solution process. In this manner, various system components were incorporated into one framework for holistic consideration and optimization. Integrality and uncertainty, as well as the multiobjective and dynamic characteristics of the watershed system, were well addressed. Using two scenarios, two planning schemes were generated. Agriculture, tourism, macroeconomics, cropland use, water supply, forest coverage, soil erosion, and water pollution were fully interpreted and compared to identify a preferable planning alternative for local agencies. This study showed that the IFMOPLWS is a powerful tool for integrated watershed management planning and can provide a solid base for sustainable watershed management.  相似文献   
3.
Harmful algal blooms, which are considered a serious environmental problem nowadays, occur in coastal waters in many parts of the world. They cause acute ecological damage and ensuing economic losses, due to fish kills and shellfish poisoning as well as public health threats posed by toxic blooms. Recently, data-driven models including machine-learning (ML) techniques have been employed to mimic dynamics of algal blooms. One of the most important steps in the application of a ML technique is the selection of significant model input variables. In the present paper, we use two extensively used ML techniques, artificial neural networks (ANN) and genetic programming (GP) for selecting the significant input variables. The efficacy of these techniques is first demonstrated on a test problem with known dependence and then they are applied to a real-world case study of water quality data from Tolo Harbour, Hong Kong. These ML techniques overcome some of the limitations of the currently used techniques for input variable selection, a review of which is also presented. The interpretation of the weights of the trained ANN and the GP evolved equations demonstrate their ability to identify the ecologically significant variables precisely. The significant variables suggested by the ML techniques also indicate chlorophyll-a (Chl-a) itself to be the most significant input in predicting the algal blooms, suggesting an auto-regressive nature or persistence in the algal bloom dynamics, which may be related to the long flushing time in the semi-enclosed coastal waters. The study also confirms the previous understanding that the algal blooms in coastal waters of Hong Kong often occur with a life cycle of the order of 1–2 weeks.  相似文献   
4.
电流除了用罗果夫斯基线圈进行测量外,还可通过环探头测量电流产生的磁场来计算得到。直线电机除了位置固定的母线导体外,还有沿母线运动的电枢;母线回路注入脉冲电流后,电枢会被加速而运动。简化母线和电枢为线电流模型,在长线模型基础上,通过环探头测量得到的磁场计算出近似电流波形。因为探头所测磁场主要由其附近电流所贡献,所以合理配置电枢起始位置与探头位置后,电枢运动对电流测量的影响很小。在瞬态电流上升沿、平台区和下降沿的不同阶段,利用实验折算的系数,可得到时域瞬态电流波形,其测量结果与用罗果夫斯基线圈测量波形一致。  相似文献   
5.
Liu  Chuanfa  Zhou  Zhiwei  Qin  Juan  Xia  Guangbo  Liu  Yangyang  He  Binbin  Li  Fanqing  Sun  Peiyong  Wu  Wenliang 《Journal of Porous Materials》2021,28(4):1215-1225
Journal of Porous Materials - New Sn-Ti microspheres were first successfully synthesized by a PVP-assisted sol-gel method in this paper, and their performance in the B–V oxidation of...  相似文献   
6.
交叉证认是实现多波段数据融合的关键技术,目前还缺乏对其分布式算法的研究。快速增长的数据规模使该问题必须要依赖分布式并行计算技术解决。提出了一种基于MapReduce分布式模型的新方法,根据Map-Reduce的要点,尽量减少了任务间的通信量,并通过合理设置划分粒度保证了效率与存储间的平衡。实验结果表明,该方法对海量数据交叉证认的效率提升明显,在大规模集群上达到了接近线性的加速比。该方法为交叉证认提供了一种快速有效的解决途径。  相似文献   
7.
董延涛  邢万里  王京 《矿产勘查》2023,14(10):1849-1855
文章剖析了中国矿产资源勘查开发面临的战略机遇和风险挑战,从行业运行规律、宏观管理政策、资本市场发展等方面分析了资本支持矿产资源勘查存在的突出问题,在此基础上,提出了新形势下资本市场支持中国矿产资源勘查、助力国家资源安全的思路框架和路径举措:(1)统筹谋划,为社会资本支持矿产资源勘查开发提供战略指引。(2)改革创新,持续打造更加良好的矿业发展营商环境。(3)试点先行,建立完善以中国特色风险勘查资本市场为核心的多层次矿业资本市场。(4)银企联动,创新完善矿产资源勘查开发间接融资支持体系。(5)精心培育,弘扬企业家精神,加快建设风险勘查经营主体。(6)扩大开放,建立更高水平开放型勘查开采新体制。(7)综合保障,加快完善矿产资源勘查开发综合服务体系。  相似文献   
8.
随着水电开发强度增大,公众环保意识增强,水电建设项目环境管理要求不断提高,水电工程建设和运营中生态保护措施也得到不断加强,在此过程中,环境影响技术评估工作发挥了积极的推动作用。以安谷水电站为例,阐述了两次技术评估时安谷水电站所采取的主要生态保护措施及环保投资内容,通过对措施及水电站建设投资的对比,说明了水电建设项目环境影响技术评估严格把关的作用。  相似文献   
9.
《工程(英文)》2018,4(3):392-397
Failures are very common during the online real-time monitoring of large quantities of complex liquids in industrial processes, and can result in excessive resource consumption and pollution. In this study, we introduce a monitoring method capable of non-contact original-state online real-time monitoring for strongly coated, high-salinity, and multi-component liquids. The principle of the method is to establish the relationship among the concentration of the target substance in the liquid (C), the color space coordinates of the target substance at different concentrations (L1, a1, b1), and the maximum absorption wavelength (λmax); subsequently, the optimum wavelength λT of the liquid is determined by a high-precision scanning-type monitoring system that is used to detect the instantaneous concentration of the target substance in the flowing liquid. Unlike traditional monitoring methods and existing online monitoring methods, the proposed method does not require any pretreatment of the samples (i.e., filtration, dilution, oxidation/reduction, addition of chromogenic agent, constant volume, etc.), and it is capable of original-state online real-time monitoring. This method is employed at a large electrolytic manganese plant to monitor the Fe3+ concentration in the colloidal process of the plant’s aging liquid (where the concentrations of Fe3+, Mn2+, and (NH4)2SO4 are 0.5–18 mg·L−1, 35–39 g·L−1, and 90–110 g·L−1, respectively). The relative error of this monitoring method compared with an off-line laboratory monitoring is less than 2%.  相似文献   
10.
汪新文  刘云霞 《工矿自动化》2011,37(10):121-124
以羊场湾煤矿120204综采工作面为例,介绍了一种工作面压力实时监测系统的设计。该系统根据压力监测单元采集的各支架前柱、后柱、前梁压力参数,由地面主机中的分析软件给出量化分析结果,即支架前后柱及前梁压力变化、支架立柱的工作特性、支架立柱循环阻力的频率分布、顶板压力分布;并可根据支架立柱的工作特性分析结果分析支架压力变化与顶煤破碎效果之间的关系,从而为提高放顶煤效率提供依据。实际应用表明,该系统功能完善,能有效地反映工作面压力变化的全过程。  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