全文获取类型
收费全文 | 9805篇 |
免费 | 599篇 |
国内免费 | 431篇 |
专业分类
电工技术 | 528篇 |
综合类 | 841篇 |
化学工业 | 706篇 |
金属工艺 | 396篇 |
机械仪表 | 701篇 |
建筑科学 | 1976篇 |
矿业工程 | 396篇 |
能源动力 | 181篇 |
轻工业 | 789篇 |
水利工程 | 432篇 |
石油天然气 | 324篇 |
武器工业 | 72篇 |
无线电 | 668篇 |
一般工业技术 | 418篇 |
冶金工业 | 403篇 |
原子能技术 | 59篇 |
自动化技术 | 1945篇 |
出版年
2024年 | 10篇 |
2023年 | 58篇 |
2022年 | 115篇 |
2021年 | 190篇 |
2020年 | 192篇 |
2019年 | 118篇 |
2018年 | 155篇 |
2017年 | 177篇 |
2016年 | 212篇 |
2015年 | 256篇 |
2014年 | 521篇 |
2013年 | 479篇 |
2012年 | 639篇 |
2011年 | 803篇 |
2010年 | 611篇 |
2009年 | 597篇 |
2008年 | 542篇 |
2007年 | 812篇 |
2006年 | 764篇 |
2005年 | 499篇 |
2004年 | 458篇 |
2003年 | 446篇 |
2002年 | 406篇 |
2001年 | 317篇 |
2000年 | 267篇 |
1999年 | 248篇 |
1998年 | 135篇 |
1997年 | 140篇 |
1996年 | 146篇 |
1995年 | 102篇 |
1994年 | 85篇 |
1993年 | 72篇 |
1992年 | 63篇 |
1991年 | 41篇 |
1990年 | 37篇 |
1989年 | 26篇 |
1988年 | 19篇 |
1987年 | 21篇 |
1986年 | 8篇 |
1985年 | 10篇 |
1984年 | 9篇 |
1983年 | 4篇 |
1982年 | 7篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1976年 | 4篇 |
1965年 | 2篇 |
1964年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Claudia Paredes Francisco J. Martínez-Vázquez Hamada Elsayed Paolo Colombo Antonia Pajares Pedro Miranda 《Journal of the European Ceramic Society》2021,41(1):892-900
Bioactive ceramic scaffolds for bone regeneration consisting of a three-dimensional mesh of interpenetrating struts with square section were fabricated via Digital Light Processing (DLP). The ability of the technique to manufacture 3D porous structures from β-tricalcium phosphate (β-TCP) powders with different dimensions of struts and pores was evaluated, identifying the possibilities and limitations of the manufacturing process. Small pore sizes were found to seriously complicate the elimination of excess slurry from the scaffold’s innermost pores. The effect of the strut/pore size on the mechanical performance of the scaffolds under compressive stresses was also evaluated, but no significant influence was found. Under compressive stresses, the structures resulted weaker when tested perpendicularly to the printing plane due to interlayer shear failure. Interlayer superficial grooves are proposed as potential failure-controlling defects, which could also explain the lack of a Weibull size effect on the mechanical strength of the fabricated DLP scaffolds. 相似文献
2.
《International Journal of Hydrogen Energy》2022,47(51):21613-21633
When planning large-scale 100% renewable energy systems (RES) for the year 2050, the system capacity is usually oversized for better supply-demand matching of electrical energy since solar and wind resources are highly intermittent. This causes excessive excess energy that is typically dissipated, curtailed, or sold directly. The public literature shows a lack of studies on the feasibility of using this excess for country-scale co-generation. This study presents the first investigation of utilizing this excess to generate green hydrogen gas. The concept is demonstrated for Jordan using three solar photovoltaic (PV), wind, and hybrid PV-wind RESs, all equipped with Lithium-Ion battery energy storage systems (ESSs), for hydrogen production using a polymer electrolyte membrane (PEM) system. The results show that the PV-based system has the highest demand-supply fraction (>99%). However, the wind-based system is more favorable economically, with installed RES, ESS, and PEM capacities of only 23.88 GW, 2542 GWh, and 20.66 GW. It also shows the highest hydrogen annual production rate (172.1 × 103 tons) and the lowest hydrogen cost (1.082 USD/kg). The three systems were a better option than selling excess energy directly, where they ensure annual incomes up to 2.68 billion USD while having payback periods of as low as 1.78 years. Furthermore, the hydrogen cost does not exceed 2.03 USD/kg, which is significantly lower than the expected cost of hydrogen (3 USD/kg) produced using energy from fossil fuel-based systems in 2050. 相似文献
3.
织金电视台通过对有线电视网络进行双向改造,为Internet宽带接入、数字电视、VOD等多媒体应用提供了运行平台,介绍织金县城区HFC双向网络设计方案。 相似文献
4.
5.
6.
一种非线性Radon变换及非零偏移距VSP波场分离 总被引:7,自引:2,他引:5
本文给出了一种非线性Radon变换正反投影公式。这种变换比常规Radon变换具有更广泛的用途。本文探讨了这种变换在地震数据处理中的某些应用,并用这种非线性Radon变换进行了非零偏移距的VSP波场分离处理,效果较好。 相似文献
7.
中国未来电力需求与核能 总被引:5,自引:0,他引:5
本文介绍了我国未来电力需求和能源结构,阐述了核能是我国满足经济发达地区电力需求的合理选择,并提出了我国“九五”核电计划和中期目标,以及发展核电中面临的问题和基本对策。 相似文献
8.
Claudia Popien Axel Kuepper Bernd Meyer 《Journal of Network and Systems Management》1994,2(4):383-400
New requirements of growing computer networks and information systems have an influence on extended client/server models with increased functionality. This forms the basis for service management in distributed systems which is realized by a service trading concept. This paper studies the requirements derived from the Open Distributed Processing (ODP) Reference Model in order to consider an open service market. Furthermore, it examines management possibilities for describing the service trading scenario. Because of similar architectures and properties ODP services, service offers, types, exporters and traders are mapped onto management components and modeled as managed objects. Therefore, the Guidelines for the Definition of Managed Objects (GDMO) are used. The final concept allows a precise and unambiguous study of the service trading scenario and provides means for exporting and importing of service offers in a distributed environment. 相似文献
9.
实施油气回收的必要性和技术方案的探讨 总被引:8,自引:0,他引:8
郝保良 《石油化工管理干部学院学报》2002,(2):41-42,69
简要介绍油气回收技术;从环保和增加经济效益的角度,以福建炼化公司的实际情况为例提出了油气回收的方案,并对实行该方案的必要性和经济效益做了分析;希望增强炼化企业对油气回收问题的重视,达到安全生产、改善环境和节约能源的目的。 相似文献
10.
小浪底水库投入运用后,黄河下游水沙条件的变化,使游荡性河道整治出现了新情况,新问题。下一步治理应注意积极修建新布点工程,完成具有关键性导流作用的续建工程,确定适应新情况的设计治导线,积极开展新结构试验和观测研究。 相似文献