全文获取类型
收费全文 | 11731篇 |
免费 | 440篇 |
国内免费 | 214篇 |
专业分类
电工技术 | 387篇 |
综合类 | 735篇 |
化学工业 | 651篇 |
金属工艺 | 2875篇 |
机械仪表 | 2053篇 |
建筑科学 | 750篇 |
矿业工程 | 700篇 |
能源动力 | 798篇 |
轻工业 | 237篇 |
水利工程 | 604篇 |
石油天然气 | 376篇 |
武器工业 | 147篇 |
无线电 | 167篇 |
一般工业技术 | 623篇 |
冶金工业 | 849篇 |
原子能技术 | 71篇 |
自动化技术 | 362篇 |
出版年
2024年 | 23篇 |
2023年 | 149篇 |
2022年 | 206篇 |
2021年 | 234篇 |
2020年 | 322篇 |
2019年 | 231篇 |
2018年 | 219篇 |
2017年 | 339篇 |
2016年 | 403篇 |
2015年 | 452篇 |
2014年 | 642篇 |
2013年 | 499篇 |
2012年 | 673篇 |
2011年 | 849篇 |
2010年 | 609篇 |
2009年 | 615篇 |
2008年 | 468篇 |
2007年 | 725篇 |
2006年 | 704篇 |
2005年 | 616篇 |
2004年 | 553篇 |
2003年 | 455篇 |
2002年 | 394篇 |
2001年 | 327篇 |
2000年 | 303篇 |
1999年 | 273篇 |
1998年 | 247篇 |
1997年 | 165篇 |
1996年 | 180篇 |
1995年 | 134篇 |
1994年 | 98篇 |
1993年 | 98篇 |
1992年 | 44篇 |
1991年 | 23篇 |
1990年 | 29篇 |
1989年 | 27篇 |
1988年 | 22篇 |
1987年 | 9篇 |
1986年 | 11篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1982年 | 1篇 |
1981年 | 5篇 |
1979年 | 2篇 |
1959年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
2.
筒形阀是一种新型的水轮机进水阀,它与球阀或蝴蝶阀相比较有防止机组飞逸事故扩大效果明显、减轻导叶全关时导水机构的快速破坏并减少漏水量,以及动水开启方便、所需时间短等优点,但对运行条件也有一定的要求。光照水电站是贵州省第1个拟采用筒形阀的电站,为此对装设筒形阀的可行性和必要性进行了认真的分析。 相似文献
3.
文章简单介绍了气动阀的结构、工作原理及特点,并时堆修保养注意事项以及可能发生的故障和排除故障的方法做了详细讲解。最后,将气动阀在柴油罐上的应用情况与普通闸阀相比较,分析其使用性能和优点,进一步推广气动闽在锦西石化分公司的应用。 相似文献
4.
S. David Graber 《Canadian Metallurgical Quarterly》2004,130(1):67-80
Numerous types of pipes and channels with spatially increasing flows in environmental engineering applications are identified by type and function and referred to as collection conduits. An overview of methods for designing and analyzing collection conduits is provided. Full conduits with nonuniform and uniform inflow are first considered. Dimensional analysis is then employed to demonstrate the relationship between variables for open channels; that leads to the identification of possibilities for generalized numerical solutions. Prior collection conduit applications are discussed within the framework of the dimensional analysis (which also pertains to some constant-flow applications). A previously unpublished generalized numerical solution for rectangular collection conduits is presented. Subsurface drains are addressed with particular emphasis, including the use of numerical methods to develop a new generalized chart and relation to other design methods. Among the important conclusions for subsurface drains is that the somewhat common practice of using Manning’s equation alone for such problems is not generally adequate. Examples and practical design suggestions are included, and the use of computer-based numerical methods is discussed more generally. 相似文献
5.
The accurate prediction of the propagation of a wetting front in an unsaturated soil subjected to surficial infiltration is of practical importance to many geotechnical and geoenvironmental problems. The finite element method is the most common solution technique as the hydraulic soil properties are highly nonlinear. Two important issues are often found to create difficulties in such analyses. First, numerical oscillations are usually observed in the calculated pore pressures at the wetting front. Second, when a reasonable mesh size and time step are used, the elevation of the wetting front may be seriously overpredicted. This paper is focused on the second issue. The under-relaxation (UR) technique used in the iterative process within each time step is found to have a serious impact on rate of convergence with refinement in mesh size and time step. Two different techniques are typically used; the first evaluates the hydraulic conductivity using an average of heads calculated from the preceding time node and the most recent iteration of the current time node (UR1), and the second evaluates the hydraulic conductivity using the average of heads calculated from the two most recent iterations of the current time nodes (UR2). The study shows that UR1, which is adopted in programs such as SEEP/W, ensures that the solution converges rapidly to a stable solution within a time step, but may converge to the wrong wetting front at a given elapsed time unless a sufficiently refined mesh is used. UR2 converges much more slowly within a time step, but the error in the wetting front is smaller than that generated by UR1. 相似文献
6.
7.
Li Yu-cheng He Ming Dept.of Civil Engineering Dalian Univ.of Technology Dalian P.R.China 《水动力学研究与进展(B辑)》1993,(4)
Based on model test,the statistical distribution of extreme values of wave-current in-line forces acting on vertical circular cylinder is analyzed in this paper.It is shownthat the results calculated by the simplified method,proposed by authors,agree well with the testdata;Weibull distribution is also adoptable in the region of high KC number, and the shapeparameter a and scale parameter β are related well with KC number respectively. 相似文献
8.
通过本钢5#高炉液压泥炮的技术改造实践,阐述了斜底座式液压泥炮在大型高炉上的应用情况,并且进一步对SGXP—400液压泥炮的某些性能特点及其液压系统进行了分析。 相似文献
9.
董祥国 《机械制造与自动化》2002,(6):17-19
根据三角旋转活塞发动机运动几何原理 ,详细分析了缸体型线。缸体的实际型线是双弧外摆线的等距曲线 ,并由此导出其数学表达式。本文进一步说明了两种几何运动实现方式 ,分析了参数的几何意义 ,并给出其表达式。 相似文献
10.
液压系统广义可靠性设计 总被引:3,自引:0,他引:3
介绍了广义可靠性和有效度的基本概念,简要论述了对液压系统进行广义可靠性设计的重要性,并从可靠性设计和维修性设计两方面提出了提高液压系统有效度的具体措施。/ 相似文献