全文获取类型
收费全文 | 180842篇 |
免费 | 16706篇 |
国内免费 | 10198篇 |
专业分类
电工技术 | 13864篇 |
技术理论 | 8篇 |
综合类 | 18037篇 |
化学工业 | 18666篇 |
金属工艺 | 7235篇 |
机械仪表 | 16740篇 |
建筑科学 | 20411篇 |
矿业工程 | 6751篇 |
能源动力 | 7860篇 |
轻工业 | 16809篇 |
水利工程 | 7502篇 |
石油天然气 | 8513篇 |
武器工业 | 2010篇 |
无线电 | 10117篇 |
一般工业技术 | 17251篇 |
冶金工业 | 7060篇 |
原子能技术 | 2546篇 |
自动化技术 | 26366篇 |
出版年
2024年 | 764篇 |
2023年 | 2203篇 |
2022年 | 4554篇 |
2021年 | 5348篇 |
2020年 | 5620篇 |
2019年 | 4730篇 |
2018年 | 4697篇 |
2017年 | 5715篇 |
2016年 | 6875篇 |
2015年 | 7142篇 |
2014年 | 11596篇 |
2013年 | 11984篇 |
2012年 | 13522篇 |
2011年 | 14873篇 |
2010年 | 10647篇 |
2009年 | 10874篇 |
2008年 | 10140篇 |
2007年 | 12140篇 |
2006年 | 10522篇 |
2005年 | 8779篇 |
2004年 | 7417篇 |
2003年 | 6352篇 |
2002年 | 5110篇 |
2001年 | 4197篇 |
2000年 | 3599篇 |
1999年 | 2999篇 |
1998年 | 2567篇 |
1997年 | 2163篇 |
1996年 | 1782篇 |
1995年 | 1469篇 |
1994年 | 1322篇 |
1993年 | 986篇 |
1992年 | 903篇 |
1991年 | 667篇 |
1990年 | 554篇 |
1989年 | 472篇 |
1988年 | 398篇 |
1987年 | 268篇 |
1986年 | 234篇 |
1985年 | 216篇 |
1984年 | 252篇 |
1983年 | 240篇 |
1982年 | 196篇 |
1981年 | 109篇 |
1980年 | 95篇 |
1979年 | 65篇 |
1978年 | 53篇 |
1977年 | 46篇 |
1976年 | 43篇 |
1959年 | 30篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
从控制和保证压力容器类焊接产品质量角度出发,通过分析其在制造过程中每道工序可能出现的质量问题,总结出这类产品在制造过程质量分析的要领及内容,提出了质量控制的关键,为制定焊接检验方案提供依据。 相似文献
62.
This paper deals with the decomposition analysis of energy-related CO2 emissions in Greece from 1990 to 2002. The Arithmetic Mean Divisia Index (AMDI) and the Logarithmic Mean Divisia Index (LMDI) techniques are applied and changes in CO2 emissions are decomposed into four factors: income effect, energy intensity effect, fuel share effect and population effect. The period-wise and time series analyses show that the biggest contributor to the rise in CO2 emissions in Greece is the income effect; on the contrary, the energy intensity effect is mainly responsible for the decrease in CO2 emissions. A comparison of the results of the two techniques gave an insight in the intricacies of energy decomposition. Finally, conclusions and future areas of research are presented. 相似文献
63.
Many approaches have been proposed to enhance software productivity and reliability. These approaches typically fall into three categories: the engineering approach, the formal approach and the knowledge-based approach. But the optimal gain in software productivity cannot be obtained if one relies on only one of these approaches. This paper describes the work in knowledge-based software engineering conducted by the authors for the past 10 years. The final goal of the research is to develop a paradigm for software engineering which integrates the three approaches mentioned above. A knowledge-based tool which can support the whole process of software development is provided in this paper. 相似文献
64.
65.
66.
67.
68.
SVK8 3S型氮气压缩机是由沈阳鼓风机厂制造、为义马煤气配套的低压氮气压缩机 ,共两套 ,于 2 0 0 0年 1 2月开始调试。为节约工程基建资金 ,取消原设计两台中压氮气压缩机 ,由杭氧产两台3TYS89+2TYS60型氧气透平压缩机临时压送氮气 ,向外供中压氮 ,来取代中压氮气压缩机 ,流程示意图如图 1所示。图 1 氧、氮压机工艺流程配置图1 事故情况2 0 0 0年 1 2月 2 7日中午 1 1∶3 5 ,接总调度室通知 ,要求中午 1 2∶0 0向长输管线供中压氮气。当时 ,一台氮压机试车完毕正在运行 ,一台氧压机试车完毕压氧正在运行 ,将由氧压机临时压送氮气外供… 相似文献
69.
The dynamic flexibility (DF) and improved dynamic flexibility (IDF) methods can be applied to extract constrained structural modes from free-free modal test data. The residual flexibility method is also good for boundaries of constrained structure with rigid supports. Under elastic support boundary conditions both the DF and residual flexibility methods cannot produce accurate results. This paper expands the previously published IDF method to become a more general approach for structural design engineers. A new method called the general dynamic flexibility (GDF) method has been developed in this paper to extract constrained structural modes from free test data. The GDF method can always be applied as follows: (1) when the boundary support stiffness is very stiff, the GDF method can accurately obtain results from rigid support as by Liu et al. in 2001 and Zhang and Wei in 2003; (2) when the support stiffness is soft, the present method can produce results similar to those free-free modal parameters measured by hanging structures using rubber band; (3) when the support stiffness is zero, the method can reproduce true free-free modal parameters; and (4) when the support stiffness has any finite values, the GDF method can also achieve satisfactory results for engineering use. The algorithm included in the GDF method converges rapidly and is numerically stable in the analysis. This feature is very practical for many engineering applications for using the GDF method. 相似文献
70.
腐败是与政府行政权力相伴生的痼疾,既是一个历史现象又是一个国际现象。贪污腐败和寻租腐败是委托一代理模型中最典型的腐败方式,文章在此基础上对贪污腐败和寻租腐败进行成本一收益分析和市场均衡分析,并探讨治理行政权力腐败的有效途径。 相似文献