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   390738篇
  免费   35966篇
  国内免费   20209篇
电工技术   82172篇
技术理论   26篇
综合类   37169篇
化学工业   31480篇
金属工艺   15676篇
机械仪表   29077篇
建筑科学   23269篇
矿业工程   12225篇
能源动力   18073篇
轻工业   11907篇
水利工程   9231篇
石油天然气   11603篇
武器工业   5153篇
无线电   45231篇
一般工业技术   24326篇
冶金工业   10670篇
原子能技术   5216篇
自动化技术   74409篇
  2024年   333篇
  2023年   4064篇
  2022年   7056篇
  2021年   9427篇
  2020年   11379篇
  2019年   14312篇
  2018年   7059篇
  2017年   10064篇
  2016年   11048篇
  2015年   12825篇
  2014年   23147篇
  2013年   20840篇
  2012年   27948篇
  2011年   30629篇
  2010年   23481篇
  2009年   24117篇
  2008年   24181篇
  2007年   29395篇
  2006年   26760篇
  2005年   23100篇
  2004年   19198篇
  2003年   17116篇
  2002年   13248篇
  2001年   11065篇
  2000年   9059篇
  1999年   7187篇
  1998年   5174篇
  1997年   4176篇
  1996年   3865篇
  1995年   3437篇
  1994年   2897篇
  1993年   2094篇
  1992年   1738篇
  1991年   1179篇
  1990年   882篇
  1989年   797篇
  1988年   543篇
  1987年   346篇
  1986年   246篇
  1985年   227篇
  1984年   217篇
  1983年   178篇
  1982年   162篇
  1981年   139篇
  1980年   86篇
  1979年   77篇
  1978年   66篇
  1977年   54篇
  1976年   50篇
  1959年   35篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
风电和光伏发电具有间歇性和随机性,为了降低在多源联合发电系统中的弃风弃光率,采用含氢储能系统和火电机组配合来平滑风电和光电机组出力。文中以系统运行成本最小和弃电惩罚成本最小为目标,以系统功率平衡、火电机组出力和爬坡、热备用、风电和光电出力及储能系统储氢罐容量、电解槽和燃料电池功率等为约束条件构建了多源联合发电系统日前调度模型。通过YALMIP工具箱对模型进行编程,并调用CPLEX对编写的程序进行求解。对含有风电、光电、火电机组以及储能系统的多源联合发电系统进行算例分析,通过对比有无储能系统的弃风弃光量和系统总运行成本,证明了含氢储能系统可以有效降低系统的弃风弃光率,并提高系统的经济性。  相似文献   
2.
光伏发电功率存在波动性,且光伏出力易受各种气象特征影响,传统TCN网络容易过度强化空间特性而弱化个体特性。针对上述问题,文中提出一种基于VMD和改进TCN的短期光伏发电功率预测模型。通过VMD将原始光伏发电功率时间序列分解为若干不同频率的模态分量,将各个模态分量以及相对应的气象数据输入至改进TCN网络进行建模学习。利用中心频率法确定VMD的最优分解模态分解个数。在传统TCN预测模型的基础上,使用DropBlock正则化取代Dropout正则化以达到抑制卷积层中信息协同的效果,并引入注意力机制自主挖掘并突出关键气象输入特征的影响,量化各气象因素对光伏发电的影响,从而提高预测精度。以江苏省某光伏电站真实数据为例进行仿真实验,结果表明所提预测方法的RMSE为0.62 MW,MAPE为2.03%。  相似文献   
3.
China has suffered overcapacity in coal power since 2016. With growing electricity demand and an economic crisis due to the Covid-19 pandemic, China faces a dilemma between easing restrictive policies for short-term growth in coal-fired power production and keeping restrictions in place for long-term sustainability. In this paper, we measure the risks faced by China's coal power units to become stranded in the next decade and estimate the associated economic costs for different shareholders. By implementing restrictive policies on coal power expansion, China can avoid 90% of stranded coal assets by 2025.  相似文献   
4.
分析了含有安全约束和备用的智能调度系统构架以及具体模块的相应功能。针对智能调度关键技术,分析了多级安全校核、基于大数据的实时数据分析与采集、调控一体化实时预警和新能源市场交易校核等内容的流程和方法。结合备用和安全约束提出了含有相关约束条件的调度模型。利用仿真模型验证了含有安全备用约束的模型正确性,通过对比分析说明了模型的有效性。  相似文献   
5.
A novel hierarchical structure of bimetal sulfide FeS2@SnS2 with the 1D/2D heterostructure was developed for high-performance sodium-ion batteries (SIBs). The FeS2@SnS2 was synthesized through a hydrothermal reaction and a sulphuration process. The exquisite 1D/2D heterostructure is featured with 2D SnS2 nanoflakes anchoring on the 1D FeS2 nanorod. This well-designed FeS2@SnS2 provides shortened ion diffusion pathway and adequate surface area, which facilitates the Na+ transport and capacitive Na+ storage. Besides, the FeS2@SnS2 integrates the 1D/2D synthetic structural advantages and synthetic hybrid active material. Consequently, the FeS2@SnS2 anode exhibits high initial specific capacity of 765.5 mAh·g−1 at 1 A·g−1 and outstanding reversibility (506.0 mAh·g−1 at 1 A·g−1 after 200 cycles, 262.5 mAh·g−1 at 5 A·g−1 after 1400 cycles). Moreover, the kinetic analysis reveals that the FeS2@SnS2 anode displays significant capacitive behavior which boosts the rate capacity.  相似文献   
6.
In recent years, superhydrophobic coatings have received extensive attention due to their functions of waterproof, antifouling, self-cleaning, etc. However, wide applications of superhydrophobic coatings are still affected by their disadvantages of complex preparation, low mechanical properties, and poor ultraviolet (UV) resistance. In this study, cellulose nanocrystal containing a small amount of lignin (L-CNC)/SiO2 composite particles were used as the main material, polydimethylsiloxane (PDMS) as the adhesive and perfluorooctyltrichlorosilane (FOTS) as the modifier to prepare superhydrophobic coatings by a one-step spray method. The resulted coating showed excellent superhydrophobicity (water contact angle (WCA) of 161° and slide angle (SA) of 7°) and high abrasion resistance (capable of withstanding 50 abrasion cycles under the load of 50 g). Moreover, it still maintained good superhydrophobicity after 5 h of exposure to the UV light (1000 W), displaying its good UV resistance. This study provides theoretical and technical reference for the simple preparation of organic‒inorganic composite superhydrophobic coatings with high abrasion resistance and good UV resistance, which is beneficial to improving the practicability and broadening the application scope of superhydrophobic coatings.  相似文献   
7.
The tool state exerts a strong influence on surface quality and profile accuracy during precision/ultraprecision machining. However, current on-machine measurement methods cannot precisely obtain the tool nose radius and wear. This study therefore investigated the onmachine measurement of tool nose radius on the order of hundreds of microns and wear on the order of a few microns to tens of microns during precision/ultra-precision machining using the edge reversal method. To provide the necessary replication, pure aluminum and pure copper soft metal substrates were evaluated, with pure copper exhibiting superior performance. The feasibility of the measurement method was then demonstrated by evaluating the replication accuracy using a 3D surface topography instrument; the measurement error was only 0.1%. The wear of the cutting tool was measured using the proposed method to obtain the maximum values for tool arc wear, flank wear, and wear depth of 3.4 lm, 73.5 lm and 3.7 lm, respectively.The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-022-00397-y  相似文献   
8.
The term environmental innovation system refers to an innovation network composed of enterprises, universities, and research institutions involved in the development and diffusion of environmental technology, with the participation of a government. An environmental innovation system not only exerts important impact on the achievement of carbon neutrality but also affects social and economic activities. Investigations on environmental innovation system performance constantly assume a single-stage independent system while ignoring its internal structure. However, such systems are composed of environmental innovation research and development (R&D) and environmental innovation conversion subsystems. A two-stage data envelopment analysis (DEA) model is developed in this study to analyze the efficiency of Chinese regional environmental innovation system by opening the “black box” and considering shared resources. Empirical results indicated that China presents high overall environmental innovation efficiency although some regions need to improve. Regions with low efficiencies in both environmental innovation R&D (EIR) and environmental innovation conversion (EIC) subsystems should expand their investment in and strengthen the management of environmental innovation resources. Regions with low EIR efficiency should improve the absorption and transformation of environmental innovation achievements. Regions with low EIC efficiency should increase investment in the commercialization of environmental innovation achievements and encourage green economy industries, such as new energy, art, tourism, and environmental protection.  相似文献   
9.
Industry 4.0 aims to transform chemical and biochemical processes into intelligent systems via the integration of digital components with the actual physical units involved. This process can be thought of as addition of a central nervous system with a sensing and control monitoring of components and regulating the performance of the individual physical assets (processes, units, etc.) involved. Established technologies central to the digital integrating components are smart sensing, mobile communication, Internet of Things, modelling and simulation, advanced data processing, storage and analysis, advanced process control, artificial intelligence and machine learning, cloud computing, and virtual and augmented reality. An essential element to this transformation is the exploitation of large amounts of historical process data and large volumes of data generated in real-time by smart sensors widely used in industry. Exploitation of the information contained in these data requires the use of advanced machine learning and artificial intelligence technologies integrated with more traditional modelling techniques. The purpose of this paper is twofold: a) to present the state-of-the-art of the aforementioned technologies, and b) to present a strategic plan for their integration toward the goal of an autonomous smart plant capable of self-adaption and self-regulation for short- and long-term production management.  相似文献   
10.
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