全文获取类型
收费全文 | 62760篇 |
免费 | 6348篇 |
国内免费 | 3350篇 |
专业分类
电工技术 | 3515篇 |
技术理论 | 1篇 |
综合类 | 5840篇 |
化学工业 | 8188篇 |
金属工艺 | 2947篇 |
机械仪表 | 3876篇 |
建筑科学 | 12211篇 |
矿业工程 | 1400篇 |
能源动力 | 3595篇 |
轻工业 | 5826篇 |
水利工程 | 1481篇 |
石油天然气 | 2840篇 |
武器工业 | 776篇 |
无线电 | 3343篇 |
一般工业技术 | 7052篇 |
冶金工业 | 2813篇 |
原子能技术 | 373篇 |
自动化技术 | 6381篇 |
出版年
2024年 | 401篇 |
2023年 | 1147篇 |
2022年 | 2136篇 |
2021年 | 2509篇 |
2020年 | 2684篇 |
2019年 | 2330篇 |
2018年 | 2291篇 |
2017年 | 2584篇 |
2016年 | 2687篇 |
2015年 | 2687篇 |
2014年 | 4155篇 |
2013年 | 4110篇 |
2012年 | 4641篇 |
2011年 | 4760篇 |
2010年 | 3499篇 |
2009年 | 3560篇 |
2008年 | 3220篇 |
2007年 | 3958篇 |
2006年 | 3428篇 |
2005年 | 2845篇 |
2004年 | 2298篇 |
2003年 | 1897篇 |
2002年 | 1593篇 |
2001年 | 1347篇 |
2000年 | 1052篇 |
1999年 | 878篇 |
1998年 | 624篇 |
1997年 | 519篇 |
1996年 | 477篇 |
1995年 | 354篇 |
1994年 | 292篇 |
1993年 | 227篇 |
1992年 | 197篇 |
1991年 | 150篇 |
1990年 | 111篇 |
1989年 | 107篇 |
1988年 | 65篇 |
1987年 | 66篇 |
1986年 | 29篇 |
1985年 | 47篇 |
1984年 | 49篇 |
1983年 | 37篇 |
1982年 | 32篇 |
1980年 | 56篇 |
1979年 | 27篇 |
1965年 | 19篇 |
1964年 | 28篇 |
1963年 | 26篇 |
1961年 | 22篇 |
1955年 | 25篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Service life planning comprises a model for the determination of a reasonable expected service life for buildings and components, and it establishes a routine for the assessment of design alternatives. A design option is considered reasonable when it meets or exceeds performance requirements over time that have been drawn up specifically for the specific project. Due to this assessment reference, there is a very evident link to the concept of performance-based building. Any stakeholder involved in the value chain or in the design process of the building, as well as regulators and building users, can express performance requirements. Identified requirements, both in relevance and in quality, will vary with the stakeholder and his/her perspective of interest. As building sector manufacturers develop most products with reference to standards rather than with reference to specific requirements, there is no direct link from user requirements to the product design. Instead, the building designer has the responsibility to ensure performance requirements are met by the performance of products integrated into the design. As these design decisions also have to be made at the material and component level, a performance-based building would benefit from an established rationale that enables the communication of performance requirements across the relevant system levels in the relevant design processes. A path for the connection of the established concepts of service life planning and performance-based building is presented. The aim is to identify key elements that need to be developed for the successful linkage of performance-based building with service life planning. 相似文献
22.
透水性沥青面层材料设计新法及应用 总被引:8,自引:0,他引:8
本文提出了一种根据主骨料空隙率设计透水性面层沥青混合料级配的新方法,根据这一方法设计的透水性沥青面层具有良好的路面使用功能,应用前景广阔。 相似文献
23.
Because the oceanaut plays a significant role in safety and capability during manned deep-diving scientific tasks, preventing oceanaut performance decline is of paramount importance. However, the factors responsible for oceanaut performance are almost entirely unexplored. To address the preceding issues, a quantitative method of fuzzy integrated Bayesian network (FIBN) was modeled within the limits of oceanaut operating procedures. To quantify the probabilities of the influencing factors, the probability of each node in the FIBN was calculated using integrated expert judgement, fuzzy logic theory, and Bayesian network. By considering a total of 28 factors related to oceanaut performance in the “Jiaolong” manned submersible, this study found that difficult sampling, long sampling times, cabin equipment failure, oceanaut physical decline, and declining decision-making ability are important factors that affect oceanaut performance. The FIBN proposed in our study fused the qualitative and quantitative methods and can be developed into a versatile tool for analysis of comprehensive systems that contain both static and dynamic factors.Relevance to industryThe results provide a powerful basis for the design of manned submersible and assignment of tasks to oceanauts, while the fuzzy integrated Bayesian network (FIBN) method proposed can be effectively applied to various quantitative assessment fields which direct researchers to deal with analysis problems of complex systems. 相似文献
24.
Chemical looping combustion (CLC) is a clean and efficient flame-free combustion technology,which combust the fuels by lattice oxygen from a solid oxygen carrier with inherent CO2 capture.The develop-ment of oxygen carriers with low cost and high redox performance is crucial to the whole efficiency of CLC process.As the solid by-product from the sulfuric acid production,pyrite cinder presented excellent redox performance as an oxygen carrier in CLC process.The main components in pyrite cinder are Fe2O3,CaSO4,Al2O3 and SiO2 in which Fe2O3 is the active component to provide lattice oxygen.In order to sys-tematic investigate the functions of supports (CaSO4,Al2O3 and SiO2) in pyrite cinder,three oxygen car-riers (Fe2O3-CaSO4,Fe2O3-Al2O3 and Fe2O3-SiO2) were prepared and evaluated in this study.The results showed that Fe2O3-CaSO4 displayed high redox activity and cycling stability in the multiple redox cycles.However,both Fe2O3-Al2O3 and Fe2O3-SiO2 experienced serious deactivation during redox reactions.It indicated that the inert Fe-Si solid solution (Fe2SiO4) was formed in the spent Fe2O3-SiO2 sample,which decreased the oxygen carrying capacity of this sample.The XPS results showed that the oxygen species on the surface of Fe2O3-CaSO4 could be fully recovered after the 20 redox cycles.It can be concluded that CaSO4 is the key to the high redox activity and cycling stability of pyrite cinder. 相似文献
25.
26.
27.
28.
采用反相高效液相色谱法测定合成meso-四苯基卟啉钴的纯度;以甲醇乙腈二氯甲烷(体积比为55∶35∶10)为流动相,ShimpackCLCODS柱(150mm×6.0mmi.d,5μm)为分离柱,流速为1.5mL/min,检测波长420nm;meso四苯基卟啉钴的测定在1.0~10μg/mL时线性关系良好(相关系数r=0.9993),加标回收率为97.03%~101.42%,重复进样的相对标准偏差RSD为0.64%~2.92%(n=5)。方法的准确度高,精密度好,实际应用效果好。 相似文献
29.
沉淀铁催化剂上F-T合成反应的研究 总被引:2,自引:1,他引:2
制备了物相组成为 Quartz- Si O2 ,Hermatite- Fe2 O3 和 Fe2 O3 - Iron Oxide的沉淀铁催化剂 ,研究了该催化剂作用上固定床积分反应器中费托合成反应特性 .发现 2 .6MPa,80 0 h-1,H2 /CO=2 /3,2 60℃~ 2 90℃时 ,随着温度的升高 ,CO和 H2 的转化率增大 ,CO2 选择性减小 ;40 0 h-1,65 0 h-1,80 0 h-1低空速和 2 4 0 0 h-1,32 0 0 h-1,40 0 0 h-1,640 0 h-1高空速时 ,随着空速的升高 ,H2转化率、CO转化率选择性下降 ,CO2 的选择性升高 ;2 80℃ ,2 .6MPa,H2 /CO进料比 2 /3,1 /1 ,2 /1时 ,随着 H2 /CO进料比的增加 ,CO转化率 ,H2 /CO利用比和 CH4选择性都增加 ,H2 转化率和 CO2选择性减小 . 相似文献
30.
介绍了快速高效隔膜压滤机的主要性能参数和特点 ;分析了压滤机在煤泥水处理系统中的应用情况和运行结果 ;应用快速高效隔膜压滤机对煤泥水处理系统进行改造后获得了较好的经济及社会效益 相似文献