全文获取类型
收费全文 | 43382篇 |
免费 | 3507篇 |
国内免费 | 2070篇 |
专业分类
电工技术 | 2252篇 |
技术理论 | 5篇 |
综合类 | 5309篇 |
化学工业 | 4854篇 |
金属工艺 | 1471篇 |
机械仪表 | 1498篇 |
建筑科学 | 6666篇 |
矿业工程 | 2267篇 |
能源动力 | 1511篇 |
轻工业 | 3018篇 |
水利工程 | 5682篇 |
石油天然气 | 2156篇 |
武器工业 | 176篇 |
无线电 | 2165篇 |
一般工业技术 | 3329篇 |
冶金工业 | 2503篇 |
原子能技术 | 354篇 |
自动化技术 | 3743篇 |
出版年
2024年 | 137篇 |
2023年 | 557篇 |
2022年 | 952篇 |
2021年 | 1207篇 |
2020年 | 1042篇 |
2019年 | 1024篇 |
2018年 | 923篇 |
2017年 | 1079篇 |
2016年 | 1228篇 |
2015年 | 1328篇 |
2014年 | 2296篇 |
2013年 | 2142篇 |
2012年 | 2835篇 |
2011年 | 2995篇 |
2010年 | 2280篇 |
2009年 | 2512篇 |
2008年 | 2290篇 |
2007年 | 2992篇 |
2006年 | 2741篇 |
2005年 | 2502篇 |
2004年 | 2158篇 |
2003年 | 1959篇 |
2002年 | 1693篇 |
2001年 | 1449篇 |
2000年 | 1207篇 |
1999年 | 993篇 |
1998年 | 703篇 |
1997年 | 617篇 |
1996年 | 519篇 |
1995年 | 480篇 |
1994年 | 375篇 |
1993年 | 321篇 |
1992年 | 244篇 |
1991年 | 158篇 |
1990年 | 172篇 |
1989年 | 153篇 |
1988年 | 124篇 |
1987年 | 101篇 |
1986年 | 63篇 |
1985年 | 59篇 |
1984年 | 51篇 |
1983年 | 24篇 |
1982年 | 23篇 |
1981年 | 32篇 |
1980年 | 28篇 |
1979年 | 31篇 |
1977年 | 17篇 |
1976年 | 18篇 |
1975年 | 20篇 |
1974年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 203 毫秒
131.
Fisher最优分割法在星星哨水库汛期分期划分中的应用 总被引:1,自引:0,他引:1
Fisher最优分割法是对有序样本进行最优化分段的一种数学方法。本文利用该方法对星星哨水库汛期进行相应的划分,结果表明该方法是可行的。因此,可利用该结果对分期实施不同的汛限水位,使水库的防洪和兴利效益达到最大。 相似文献
132.
复杂结构井的过套管测井技术应用 总被引:1,自引:1,他引:0
王贺林 《石油地球物理勘探》2006,41(3):357-361
过套管测井是在已下套管井中完成的用以解决油气层识别、储层物性参数计算为目的的测井系列,在复杂井中用来代替常规的裸眼测井,以便减少在大斜度井中的测井事故,缩短测井周期。本文介绍了几种常用的过套管测井技术,并将其应用于大港油田的庄海401井。结果表明,过套管测井不仅解决了油气层判别的问题,也提供了较准确的物性参数,同时降低了施工作业的难度,缩短了占井周期,这一点对海上钻井尤为重要。 相似文献
133.
To find the exact probability distribution of the global maximum or minimum of a random field within a bounded domain is a pending problem even for Gaussian fields. Except for very special examples of fields, recourse must be taken to approximate reasoning or asymptotic considerations to be judged with respect to accuracy by simulations. In this paper, the problem is addressed through a functional equation that leads to the definition of a class of distribution functions that depend solely on process or field characteristics and domain quantities that can be calculated explicitly. This distribution function class is studied for Gaussian processes in earlier works by the author and it has been obtained explicitly for Gaussian fields on rectangular domains in the plane. Simulation studies show that rather good predictions are obtained for sufficiently smooth wide band Gaussian processes and fields. In this paper, the distribution function is obtained in general for Gaussian fields over arbitrary bounded domains with piecewise continuous and differentiable boundaries, and as in earlier works the distribution function is tested against empirical distribution functions obtained by simulation of sample functions of a smooth approximately Gaussian field, herein called a broken line Hino field. For completeness this particular field type is defined in appendix a and appendix b. The paper concludes with a statistical application on data for plain concrete tensile strength. 相似文献
134.
135.
136.
研究了产品开发及快速实现过程中任务获取、任务分配、进度的协调、信息传输等相关问题,并以某半导体产品为例,进行了产品的设计和快速实现,为缩短产品开发和上市周期、提高产品的市场竞争力积累经验。 相似文献
137.
谈影响钻孔灌注桩承载力的因素 总被引:1,自引:1,他引:0
根据目前我国钻孔灌注桩的特点,从施工工艺方面,对控制沉渣、孔壁泥层过厚的问题进行了探讨,提出了合理、有效的措施,以确保桩基础承载力的正常发挥。 相似文献
138.
139.
The low melting point metallic tin powder or alloy of tin and lead was blended with polypropy-lene. A kind of in situ composite has been prepared. The variations of torque were studied when the composites were mixed in Haake torque rheogeniometer. By way of capillary extrusion, effects upon rheology of the in situ com-posites of the low melting point metals (LMPM) and coupling agent for their different variety and content, were investigated. From flow curves, the results indicate that in situ composites mixed with the LMPM are a kind of pseudoplastic fluid. If the LMPM were melted, the higher the content of the LMPM , the lower apparent viscosity of composites. Meanwhile, when the coupling agent is added into composites, the viscosity of composite will go up first and drop then. This shows that the LMPM have a promoter flow action on the polypropylene. 相似文献
140.
Coupling GIS with Hydrologic and Hydraulic Flood Modelling 总被引:6,自引:1,他引:5
Nunes Correia Francisco Castro Rego Filipe Da Grača Saraiva Maria Ramos Isabel 《Water Resources Management》1998,12(3):229-249
Geographic Information Systems (GIS) have been recognised as a powerful means to integrate and analyse data from various sources in the context of comprehensive floodplain management. As part of this comprehensive approach to floodplain management, it is very important to be able to predict the consequences of different scenarios in terms of flooded areas and associated risk. Hydrologic and hydraulic modelling plays a crucial role and there is much to gain in incorporating these modelling capabilities in GIS. This is still a rather complex task and research is being done on the full integration of these models. Interfacing between these models and GIS may be a very efficient way of overcoming the difficulties and getting very good results in terms of engineering practice. This paper presents results based on the use of Intergraph GIS coupled with Idrisi GIS. Using these two systems substantially increased the flexibility of using GIS as a tool for flood studies. A lumped (XSRAIN) and a distributed (OMEGA) hydrologic models were used to simulate flood hydrographs. The well known HEC-2 Hydraulic model was used to compute flooded areas. These models were applied in the Livramento catchment with very good results. The computation of flooded areas for different flood scenarios, and its representation in GIS, can be used in the assessment of affected property and associated damages. This is a very useful GIS-based approach to floodplain management. 相似文献