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   7160篇
  免费   876篇
  国内免费   692篇
电工技术   78篇
技术理论   1篇
综合类   702篇
化学工业   341篇
金属工艺   27篇
机械仪表   80篇
建筑科学   657篇
矿业工程   1158篇
能源动力   93篇
轻工业   58篇
水利工程   119篇
石油天然气   3267篇
武器工业   20篇
无线电   278篇
一般工业技术   163篇
冶金工业   411篇
原子能技术   48篇
自动化技术   1227篇
  2024年   14篇
  2023年   89篇
  2022年   205篇
  2021年   277篇
  2020年   359篇
  2019年   205篇
  2018年   204篇
  2017年   172篇
  2016年   247篇
  2015年   274篇
  2014年   515篇
  2013年   387篇
  2012年   523篇
  2011年   572篇
  2010年   448篇
  2009年   432篇
  2008年   368篇
  2007年   391篇
  2006年   460篇
  2005年   409篇
  2004年   358篇
  2003年   337篇
  2002年   240篇
  2001年   239篇
  2000年   180篇
  1999年   171篇
  1998年   127篇
  1997年   137篇
  1996年   89篇
  1995年   64篇
  1994年   57篇
  1993年   32篇
  1992年   33篇
  1991年   25篇
  1990年   34篇
  1989年   18篇
  1988年   6篇
  1987年   3篇
  1986年   2篇
  1985年   3篇
  1984年   3篇
  1983年   2篇
  1981年   8篇
  1980年   4篇
  1979年   2篇
  1976年   2篇
  1957年   1篇
排序方式: 共有8728条查询结果,搜索用时 16 毫秒
101.
甲玛矿床位于西藏冈底斯成矿带,其勘查和研究程度均较高,矿体由斑岩型矿体、矽卡岩型矿体、角岩型矿体及外围独立金矿体组成,具有多元矿体结构,其成矿元素为Cu、Mo、Pb、Zn、Au和Ag,呈现多金属成矿作用特征。矿区深部及外围的勘查找矿方向一直是地质学者们关注的热点。在斑岩成矿系统理论的指导下,近年来在甲玛矿区深部及外围取得了重大找矿突破。基于最新勘查成果,甲玛矿床共探获铜资源储量超过850×104 t,钼资源量达91×104 t,铅锌资源量超过150×104 t,伴生金储量为220 t,伴生银储量超过1×104 t,达到超大型矿床规模。为进一步指导区域及外围勘查找矿工作,以甲玛矿区最新勘查成果为基础,通过对矿区钻孔的详细编录,采用地表构造蚀变填图等方法,系统解剖了甲玛矿区不同矿段的矿体地质结构,并揭示了其矿床地质特征。结合甲玛矿区新发现的主矿段深部的厚大矽卡岩矿体和外围则古朗北矿段的巨厚斑岩型矿体,分析了矿区深部及外围找矿潜力,认为甲玛矿区深部仍存在厚大矽卡岩铜钼矿体和斑岩钼矿体,应进一步加强对外围则古朗北矿段新发现的斑岩矿体、矽卡岩矿体和角岩型矿体的勘查,建立新的资源储备。此外,归纳总结有效勘查找矿方法,以期为深入探究甲玛矿床成矿作用和创建综合勘查找矿模型提供参考依据,并通过系统梳理矿区已有勘查和研究资料,总结甲玛矿床的找矿标志,为区域类似矿床的地质勘查提供重要线索,也为青藏高原斑岩成矿系统的勘查和研究工作奠定坚实基础。  相似文献   
102.
为了研究贵州省页岩气的储量分布及开发利用的现状,根据国土资源部公布的《全国页岩气资源潜力评价》,贵州省地质调查院的《贵州省黔南地区页岩气资源调查评价》,以及贵州省能源局等部门的相关资料统计,简要分析了黔北和黔南地区的页岩气资源储量分布情况,调查资料显示:目前贵州省页岩气地质资源量为13.54万亿m~3,可采资源量约1.95万亿m~3。重点探讨了贵州省各地区页岩气资源的勘探与利用现状,主要集中在绥阳、凤冈和岑巩等页岩气富集区块进行勘探,并针对页岩气资源勘探广而不精、缺乏专业人才与设备、商业利用价值的提升等问题进行了综合评述。  相似文献   
103.
With ever increasing global demand and depleting resources for fossil fuels, oil and gas industry is now positively looking for advanced robotic solutions to increase their productivity and safety. With time easy resources of the fossil fuels are shrinking and newly searched reservoirs, to feed supply demands of global consumption, are mostly located in extreme environmental conditions such as hot deserts, deep water and arctic zone etc. Production of the fossil fuels, in such inhospitable environmental conditions, poses difficult challenges to health, safety and environment (HSE). Tragic incidents like Exxon Valdez and Deepwater Horizon oil spills are examples of such challenges. Therefore, oil and gas industry has lot to learn from successful implementation of robotics and automation for dull, dirty and dangerous (3D) tasks of manufacturing industry. Most of the robotics technologies, currently used in the oil and gas industry, are mainly focused on inspection, maintenance and repair (IMR) of plant facilities with higher frequency and accuracy. Fundamental idea, involved in the automatization of these processes, is based on the principle of teleoperation with skilled operator. Automation of 3D tasks not only improves HSE standards but also lead to much needed economic efficiency by reducing production cycle, floor space and number of staff members required for continuous inspection and manipulation of plant facilities. Considering the risks involved in this industry usage of completely autonomous robots, first without achieving very high reliability, is still a far fetch choice. Therefore, semi-autonomous robots, where actions are performed by robots but cognitive decisions are still taken by skilled operator, is an excellent choice for this industry as a near future solution. In the onshore oil and gas industry robotic solutions are used both in upstream and downstream processes, such as site survey, drilling, production and transportation, mainly focused in the form of in-pipe inspection robots (IPIRs), tank inspection robots (TIRs), unmanned aerial vehicles (UAVs) and wireless sensor networks (WSNs) etc. This paper presents the state of art robotic solutions currently used in onshore oil and gas facilities.  相似文献   
104.
The realization of complex engineered systems using models that are typically incomplete, inaccurate and not of equal fidelity requires the understanding and prediction of process behavior in design. This necessitates the need for extending designer’s abilities in making design decisions that are robust, flexible and modifiable particularly in the early stages of design. To address this requirement, we propose in this paper, an ontology for design space exploration and a template-based ontological method that supports systematic design space exploration ensuring the determination of the right combination of design information that meets the different goals and requirements set for a process chain. Using the proposed method, a designer is able to (1) systematically adjust the design space in due time to manage the risks of errors accumulating and propagating during the design of different stages of the process chain, (2) improve the ability to communicate and understand the interactions between design information in the process chain. We achieve the said through (1) procedure for design space exploration is identified to determine the sequence of activities needed for the systematic exploration of design space under uncertainty; (2) the decision-based design information flow is archived using the design space exploration process template and represented by utilizing frame-based ontology to facilitate the management of re-usable information. We demonstrate the efficacy of this template-based ontological method for design space exploration by carrying out the design of a multi-stage hot rod rolling system in steel manufacturing process chain.  相似文献   
105.
Analyzing market performance via social media has attracted a great deal of attention in the finance and machine-learning disciplines.However,the vast majority of research does not consider the enormous influence a crisis has on social media that further affects the relationship between social media and the stock market.This article aims to address these challenges by proposing a multistage dynamic analysis framework.In this framework,we use an authorship analysis technique and topic model method to identify stakeholder groups and topics related to a special firm.We analyze the activities of stakeholder groups and topics in different periods of a crisis to evaluate the crisis’s influence on various social media parameters.Then,we construct a stock regression model in each stage of crisis to analyze the relationships of changes among stakeholder groups/topics and stock behavior during a crisis.Finally,we discuss some interesting and significant results,which show that a crisis affects social media discussion topics and that different stakeholder groups/topics have distinct effects on stock market predictions during each stage of a crisis.  相似文献   
106.
In this paper, the exploration and map-building of unknown environment by a team of mobile robots is intensively investigated. A new exploration technique is proposed to increase the exploration efficiency. In particular, the new technique has two main objectives: firstly, it aims at reducing the exploration time and the traveled distance by reducing the overlap which takes place when a certain area in the environment is explored by more than one robot. To achieve this, a new procedure to assign the next target location for each individual robot is proposed. And secondly, it aims at reducing computations complexity required by target selection and path planning tasks. More importantly, the proposed technique obviates the need for environment segmentation complex procedures which is adopted in some previous important research works. The new technique is intensively tested with different environments. The results showed the effectiveness of the proposed technique.  相似文献   
107.
This paper investigates the research profiles, collaboration patterns and research topic trends which can be identified in the proposals submitted to the ECHORD (European Clearing House for Open Robotics Development) FP7 project. On a country level, clusters were identified and characterized by patterns of proposal production per inhabitant, score and international cooperation. Belgium and Sweden constitute a cluster characterized by high proposal production, with very high scores and extensive international collaboration. Belgium also excels from another cluster analysis, being as the only country where 100% of proposals involve industry–academia cooperation and obtain scores above 10. Other findings show that single partner proposals have significantly lower quality than multi-partner proposals but, on the other hand, the number of countries involved shows no influence on the quality of the proposals. Despite the high number of industrial participants present on the proposals, it is observed that they play secondary roles in the proposals, with a very low number projects leaded by companies. Also, it is observed that partnerships between research institutions (non-universities) are the most successful. Concerning topics of the proposals, the technology human–robot interface and the product vision robot for small-scale manufacturing are the most significant. Finally, the paper shows clusters of institutions extracted from the giant network of relations obtained from the ECHORD set of proposals.  相似文献   
108.
马震聪 《南方建筑》2017,(6):122-126
文章结合珠海长隆主题公园的创作回顾了我国主题公园的发展,分析了出现的问题,总结历史经验及教训,提出了:凸显地域文化、丰富主题内涵;杜绝跟风抄袭、强化主题创新;推广复合主题、扩展客源分布;深挖体验途径、强调形式多元;加强科技融合、增强主题表现的提升策略,并将此理论运动到珠海长隆国际海洋主题公园的创作实践中。  相似文献   
109.
In this article, we present an information gain-based variant of the next best view problem for occluded environment. Our proposed method utilizes a belief model of the unobserved space to estimate the expected information gain of each possible viewpoint. More precise, this belief model allows a more precise estimation of the visibility of occluded space and with that a more accurate prediction of the potential information gain of new viewing positions. We present experimental evaluation on a robotic platform for active data acquisition, however due to the generality of our approach it also applies to a wide variety of 3D reconstruction problems. With the evaluation done in simulation and on a real robotic platform, exploring and acquiring data from different environments we demonstrate the generality and usefulness of our approach for next best view estimation and autonomous data acquisition.  相似文献   
110.
世界经济温和回升背景下,受矿产品价格下跌影响,2013年全球地质勘查投入大幅下滑,投资更偏向于矿山项目。受外部经济环境影响,我国地质勘查投入出现多年来的首次下降,煤、金、铁、铜矿投入比例较高,探矿权市场相对稳定,地勘经济形势不容乐观,预期2014年地勘经济保持低迷,地勘活动有望在2015年底回暖。  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