全文获取类型
收费全文 | 9257篇 |
免费 | 510篇 |
国内免费 | 516篇 |
专业分类
电工技术 | 582篇 |
技术理论 | 2篇 |
综合类 | 1285篇 |
化学工业 | 357篇 |
金属工艺 | 303篇 |
机械仪表 | 733篇 |
建筑科学 | 1109篇 |
矿业工程 | 359篇 |
能源动力 | 172篇 |
轻工业 | 175篇 |
水利工程 | 202篇 |
石油天然气 | 459篇 |
武器工业 | 99篇 |
无线电 | 763篇 |
一般工业技术 | 287篇 |
冶金工业 | 531篇 |
原子能技术 | 169篇 |
自动化技术 | 2696篇 |
出版年
2023年 | 38篇 |
2022年 | 76篇 |
2021年 | 109篇 |
2020年 | 92篇 |
2019年 | 89篇 |
2018年 | 70篇 |
2017年 | 128篇 |
2016年 | 145篇 |
2015年 | 173篇 |
2014年 | 525篇 |
2013年 | 386篇 |
2012年 | 635篇 |
2011年 | 698篇 |
2010年 | 653篇 |
2009年 | 540篇 |
2008年 | 549篇 |
2007年 | 665篇 |
2006年 | 609篇 |
2005年 | 581篇 |
2004年 | 462篇 |
2003年 | 454篇 |
2002年 | 369篇 |
2001年 | 346篇 |
2000年 | 315篇 |
1999年 | 241篇 |
1998年 | 167篇 |
1997年 | 190篇 |
1996年 | 140篇 |
1995年 | 142篇 |
1994年 | 91篇 |
1993年 | 96篇 |
1992年 | 69篇 |
1991年 | 57篇 |
1990年 | 33篇 |
1989年 | 48篇 |
1988年 | 30篇 |
1987年 | 30篇 |
1986年 | 24篇 |
1985年 | 24篇 |
1984年 | 17篇 |
1982年 | 10篇 |
1981年 | 11篇 |
1980年 | 9篇 |
1979年 | 15篇 |
1975年 | 9篇 |
1974年 | 8篇 |
1973年 | 11篇 |
1966年 | 9篇 |
1965年 | 9篇 |
1959年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
介绍了已运用于实践中的一种全IP电视直播节目即时回看技术,用户通过遥控器一键实现直播节目的即时回看,极大地提升了用户的观看体验。通过在临汾市智慧广电全IP融合业务网建设实践项目中的使用,技术的先进性和有效性得到实践验证。 相似文献
2.
Shuo Wan Yunlong Ma Dongdong Cai Wenyuan Lin Pengsong Wang Jinyun Wang Qingdong Zheng 《Advanced functional materials》2021,31(15):2010436
Ending group halogenation is an effective strategy for modulating the energy levels, bandgaps, and intermolecular interactions of nonfullerene acceptors. Understanding the influence of different halogen atoms on the acceptor properties is of great importance for designing high-performance nonfullerene acceptors. Here, three acceptor–donor–acceptor (A-D-A) type nonfullerene acceptors (M5, M6, and M7), which are constructed by using a ladder-type heteroheptacene core without the traditional sp3 carbon-bonded side chains as the electron-rich core, and 2-(3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile without or with halogen atoms as the ending groups. The nonfullerene acceptors with chlorinated (M6) and brominated (M7) ending groups exhibit broadened absorption spectra, down-shifted energy levels, and enhanced molecular ordering compared to the counterpart without any halogenated ending groups (M5). Among the nonfullerene acceptors, M6 has the strongest intermolecular π π interaction with its shortest π π interaction distance and the longest coherent length which are beneficial for enhancing the charge transport and therefore boosting the photovoltaic performance. An excellent power conversion efficiency of 15.45% is achieved for the best-performing polymer solar cell based on M6. These results suggest that the halogenated ending groups are essential for high-performance heteroheptacene-based nonfullerene acceptors considering their simultaneous enhancements in both the light-harvesting and the charge transport. 相似文献
3.
ABSTRACTThis paper studies stochastic optimization problems with polynomials. We propose an optimization model with sample averages and perturbations. The Lasserre-type Moment-SOS relaxations are used to solve the sample average optimization. Properties of the optimization and its relaxations are studied. Numerical experiments are presented. 相似文献
4.
5.
Transportation demand of shipping container fluctuates due to the seasonality of international trade, thus, every 3–6 months, the liner company has to alter its current liner shipping service network, redeploy ships and design cargo routes with the objective of minimizing the total cost. To solve the problem, the paper presents a mixed integer linear program model. The proposed model incorporates several relevant constraints, such as weekly frequency, the transshipment of cargo between two or more service routes, and transport time. Extensive numerical experiments based on realistic date of Asia–Europe–Oceania shipping operations show that the proposed model can solve real-case problems efficiently by CPLEX. The results demonstrate that the model can reduce ship’s capacity consumption and raise ships’ capacity utilization. 相似文献
6.
《International Journal of Hydrogen Energy》2020,45(33):16751-16772
Renewable energy sources (RES) with sharing a large percentage of future energy generation capacities play an essential role in the decarbonization of the future electricity and thermal networks as well as transportation sectors. However, the uncertainties in their outputs make some difficulties in making operational decisions. Hydrogen energy plays a considerable role in this concept. Besides, energy hubs (EHs) provide an efficient and reliable framework for gathering multi-type energy carriers.This paper optimally schedules the operating of the EH and decreases the emission cost, considering the electrical and thermal demand response (DR) program in a probabilistic environment. Besides plug-in electric vehicles (PEVs) and a complete model of hydrogen-based renewable energy sources are presented in the EH. Taking into account uncertainties of electrical/thermal energy markets real-time prices, customers' energy demand, and energy production of RESs into account, various scenarios are generated using the Monte Carlo simulation technique. Next, an efficient method is used to reduce the number of the scenario to make the optimization problem computable and fast. In order to reduce the risk of encountering high operating costs, the conditional value at risk (CVaR) technique is used to manage the associated risk. Simulation results show the efficiency of the proposed method in decreasing the operational cost and managing the risk of encountering unfavorable states. 相似文献
7.
以左云长春兴煤业公司301综放工作面扇形收尾施工工艺为背景,介绍了在工作面受地质构造或者井田边界影响,工作面两顺槽与盘区大巷斜交布置时,为了多回收煤炭资源,提高经济效益,采取大角度扇形收尾的施工工艺,为厚煤层放顶煤大角度扇形收尾提供了借鉴和理论依据。 相似文献
8.
随着三网融合的大力推进以及双向互动业务的大力开展,运营商使用原有简单的EPG不足以支撑开展更多的增值业务,不能主动为用户推荐节目,不能为运营商带来新的收入机会。作为重要的创新能力支撑系统,介绍了江苏有线智能导航平台的设计与应用,为相关广电运营商提供一定的设计参考。 相似文献
9.
在本地纪初,我国有色金属工业面临着新的国际环境和市场形势,应以市场为导向,提高经济效益,促进科技进步,加快结构调整,培育有国际竞争力的大型企业集团。 相似文献
10.
在合理安排工艺过程的基础上,如何编制结构简洁、刀路科学的数控程序很大程度上影响着工件加工效率和质量,探讨如何合理运用子程序和刀具半径补偿功能,实现数控铣削加工程序的模块化、通用化。 相似文献