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   1761篇
  免费   128篇
  国内免费   46篇
电工技术   36篇
综合类   163篇
化学工业   47篇
金属工艺   17篇
机械仪表   104篇
建筑科学   559篇
矿业工程   60篇
能源动力   50篇
轻工业   42篇
水利工程   22篇
石油天然气   59篇
武器工业   6篇
无线电   147篇
一般工业技术   103篇
冶金工业   31篇
原子能技术   9篇
自动化技术   480篇
  2024年   1篇
  2023年   16篇
  2022年   28篇
  2021年   38篇
  2020年   37篇
  2019年   20篇
  2018年   29篇
  2017年   23篇
  2016年   56篇
  2015年   58篇
  2014年   110篇
  2013年   108篇
  2012年   142篇
  2011年   176篇
  2010年   113篇
  2009年   109篇
  2008年   104篇
  2007年   133篇
  2006年   112篇
  2005年   95篇
  2004年   66篇
  2003年   75篇
  2002年   63篇
  2001年   54篇
  2000年   30篇
  1999年   35篇
  1998年   22篇
  1997年   20篇
  1996年   11篇
  1995年   13篇
  1994年   11篇
  1993年   4篇
  1992年   4篇
  1991年   4篇
  1990年   2篇
  1989年   1篇
  1988年   4篇
  1986年   2篇
  1985年   2篇
  1984年   1篇
  1983年   1篇
  1982年   1篇
  1975年   1篇
排序方式: 共有1935条查询结果,搜索用时 15 毫秒
51.
陈良  钱春风 《上海金属》2005,27(4):23-26
在线磨辊(ORG)作为一种有效的轧辊轮廓和辊面质量的控制手段,可改善板带质量,提高同宽轧制km数和延长换辊周期,实现自由轧制。一钢公司1780热轧具有集中批量轧制、铁素体不锈钢与碳钢混合轧制等特点,因此ORG技术的应用显得极为重要。介绍该技术在一钢的应用情况,并提出了符合一钢生产特点的控制策略。  相似文献   
52.
Iron (Fe) and phosphorus (P) are two essential elements for plant growth. Both elements are abundant in soils but with poor availability for plants, which favor their acquisition by developing morphological and physiological responses in their roots. Although the regulation of the genes related to these responses is not totally known, ethylene (ET) and nitric oxide (NO) have been involved in the activation of both Fe-related and P-related genes. The common involvement of ET and NO suggests that they must act in conjunction with other specific signals, more closely related to each deficiency. Among the specific signals involved in the regulation of Fe- or P-related genes have been proposed Fe-peptides (or Fe ion itself) and microRNAs, like miR399 (P), moving through the phloem. These Fe- or P-related phloem signals could interact with ET/NO and confer specificity to the responses to each deficiency, avoiding the induction of the specific responses when ET/NO increase due to other nutrient deficiencies or stresses. Besides the specificity conferred by these signals, ET itself could confer specificity to the responses to Fe- or P-deficiency by acting through different signaling pathways in each case. Given the above considerations, there are preliminary results suggesting that ET could regulate different nutrient responses by acting both in conjunction with other signals and through different signaling pathways. Because of the close relationship among these two elements, a better knowledge of the physiological and molecular basis of their interaction is necessary to improve their nutrition and to avoid the problems associated with their misuse. As examples of this interaction, it is known that Fe chlorosis can be induced, under certain circumstances, by a P over- fertilization. On the other hand, Fe oxides can have a role in the immobilization of P in soils. Qualitative and quantitative assessment of the dynamic of known Fe- and P-related genes expression, selected ad hoc and involved in each of these deficiencies, would allow us to get a profound knowledge of the processes that regulate the responses to both deficiencies. The better knowledge of the regulation by ET of the responses to these deficiencies is necessary to properly understand the interactions between Fe and P. This will allow the obtention of more efficient varieties in the absorption of P and Fe, and the use of more rational management techniques for P and Fe fertilization. This will contribute to minimize the environmental impacts caused by the use of P and Fe fertilizers (Fe chelates) in agriculture and to adjust the costs for farmers, due to the high prices and/or scarcity of Fe and P fertilizers. This review aims to summarize the latest advances in the knowledge about Fe and P deficiency responses, analyzing the similarities and differences among them and considering the interactions among their main regulators, including some hormones (ethylene) and signaling substances (NO and GSNO) as well as other P- and Fe-related signals.  相似文献   
53.
In order for environmental strategies to come into effect in industry practice, they need to be implemented and applied in daily business routines. Based on a dedicated comprehensive international survey in product developing and manufacturing companies, this paper identifies major current drivers for implementing product life cycle oriented environmental strategies but also barriers and obstacles that need to be addressed. On this basis it provides a number of recommendations for manufacturing companies as well as policy makers to consider for a successful implementation of strategic environmental goals in manufacturing industry.  相似文献   
54.
中国中阶煤和高阶煤的储层特性及提高单井产量主要对策   总被引:2,自引:0,他引:2  
中国山西河东地区中阶煤储层的含气量比较低、含气饱和度低,而储层渗透性好,储层能量比较大;山西沁水盆地南部高阶煤储层的含气饱和度比较低,渗透率小,储层能量低。文章针对这些特点,进行了精细的地质对比研究,提出了提高气产量的对策。认为最大限度地降低储层的废弃压力可提高采收率;应通过改善钻井液、采用欠平衡钻井和羽状水平井钻井技术,最大限度地降低钻井工程对煤层气储层造成的伤害;同时还要利用合理的固井程序和水泥浆、套管射孔完井技术和压裂技术;通过排水降压提高有效压差及注入CO2来达到加快煤层气解吸和提高解吸量的目的。实践表明,该技术对提高单井气产量意义重大。  相似文献   
55.
混合动力汽车模糊逻辑控制策略仿真   总被引:11,自引:0,他引:11  
本文分析了混合动力汽车的能量管理方法,并应用模糊逻辑建立了控制策略模型然后利用ADVISOR提供的仿真环境模拟模糊逻辑控制策略的仿真效果。  相似文献   
56.
姜子昂  冯勐  张宏  李隽 《天然气工业》2015,35(3):120-124
为了面对能源供需格局新变化、国际能源发展新趋势,保障能源安全,国家积极推动能源革命,能源改革政策频出。为了适应国家推动能源革命的迫切要求,建立现代天然气能源产业体系,应对天然气产业发展所遇到的挑战已势在必行。在分析天然气能源革命提出的背景基础上,明晰天然气能源革命内涵,构建其基础结构模式。分析认为,中国的天然气能源革命是一项复杂的巨系统工程,是长期战略任务。进而提出建议:①实施"非常规资源保供"战略工程,建立多元网络供应保障体系;②实施"天然气能源替代"战略工程,打造清洁高效能源消费主角;③实施"天然气技术突破"战略工程,建立国际领先核心技术体系;④实施"天然气市场变革"战略工程,推动能源市场资源优化配置;⑤实施"天然气开放合作"战略工程,持续提升国际话语权影响力。该研究成果对丰富我国能源革命的内涵,助推能源革命发展具有重要的意义。  相似文献   
57.
塔里木克拉通盆地油气勘探对策   总被引:6,自引:0,他引:6  
塔里木克拉通盆地包括整个盆地“三隆四坳”^[1]中的塔北隆起、北部坳陷、塔中隆起、巴楚隆起等主要构造单元(见图1)。经多年勘探,目前已探明和发现了众多油气田(藏):塔北隆起上的轮南、塔河、东河塘等油田,塔中隆起上的塔中4、塔中16油田,巴楚隆起上的和田河气田、巴什托甫油田,北部坳陷中的哈得逊油田等。这些海相成因的油气主要富集在奥陶系碳酸盐岩与石炭系、三叠系、侏罗系砂岩储集层中,来源于寒武系和中上奥陶统两套烃源岩。  相似文献   
58.
随着我国天然气产业的发展,天然气长输管道建设明显加快。油气管道的安全生产关系到人的生命和财产安全,关系到中国石油企业的发展和企业战略目标和经济责任的实现,关系到国民经济的可持续发展和经济秩序稳定,因此应得到政府、企业界和全社会的重视,也希望全国燃气行业共同关注。文章介绍了中国石油在天然气生产和管道输送方面的业务发展,从公共安全、管道自身安全及正常的市场供应等方面,对我国油气管道安全问题现状进行了阐述,提出如下建议:①国家完善油气管道保护法规框架和执法体系;②公安部门和地方政府深入开展安全生产专项整治;③管道运营公司强化内部安全保卫工作;④加强油气管道设计、建设、运营的全过程安全管理;⑤保障资源供应和市场供应安全。  相似文献   
59.
崔成  牛建国 《中国能源》2011,(7):10-14,39
2011年3月28日,日本经济产业省正式颁布了《节能技术战略20ll》,旨在通过工业、居民与商业、运输以及综合四个部门的节能技术创新与普及,有效控制温室气体排放,进一步提高产业竞争力,实现维护能源安全、保护环境以及通过市场化手段提高经济效率的三E战略目标,并为尽快摆脱东日本大地震造成的电力短缺影响,促进日本经济复苏提供必要的动力。本文对我国“十二五”及未来节能技术发展战略的制定及实施具有参考价值。  相似文献   
60.
A roadmap towards intelligent net zero- and positive-energy buildings   总被引:1,自引:0,他引:1  
Buildings nowadays are increasingly expected to meet higher and more complex performance requirements: they should be sustainable; use zero-net energy; foster a healthy and comfortable environment for the occupants; be grid-friendly, yet economical to build and maintain. The essential ingredients for the successful development and operation of net zero- and positive-energy buildings (NZEB/PEB) are: thermal simulation models, that are accurate representations of the building and its subsystems; sensors, actuators, and user interfaces to facilitate communication between the physical and simulation layers; and finally, integrated control and optimization tools of sufficient generality that using the sensor inputs and the thermal models can take intelligent decisions, in almost real-time, regarding the operation of the building and its subsystems. To this end the aim of the present paper is to present a review on the technological developments in each of the essential ingredients that may support the future integration of successful NZEB/PEB, i.e. accurate simulation models, sensors and actuators and last but not least the building optimization and control. The integration of the user is an integral part in the dynamic behavior of the system, and this role has to be taken into account. Future prospects and research trends are discussed.  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