全文获取类型
收费全文 | 65318篇 |
免费 | 4844篇 |
国内免费 | 1920篇 |
专业分类
电工技术 | 4314篇 |
综合类 | 6163篇 |
化学工业 | 4702篇 |
金属工艺 | 2644篇 |
机械仪表 | 2668篇 |
建筑科学 | 11815篇 |
矿业工程 | 1669篇 |
能源动力 | 1254篇 |
轻工业 | 13891篇 |
水利工程 | 3335篇 |
石油天然气 | 2023篇 |
武器工业 | 266篇 |
无线电 | 4113篇 |
一般工业技术 | 3837篇 |
冶金工业 | 3596篇 |
原子能技术 | 279篇 |
自动化技术 | 5513篇 |
出版年
2024年 | 362篇 |
2023年 | 998篇 |
2022年 | 1568篇 |
2021年 | 1992篇 |
2020年 | 2091篇 |
2019年 | 1667篇 |
2018年 | 1504篇 |
2017年 | 1863篇 |
2016年 | 1963篇 |
2015年 | 2153篇 |
2014年 | 4677篇 |
2013年 | 3723篇 |
2012年 | 4627篇 |
2011年 | 4911篇 |
2010年 | 3875篇 |
2009年 | 4109篇 |
2008年 | 3599篇 |
2007年 | 4289篇 |
2006年 | 3936篇 |
2005年 | 3150篇 |
2004年 | 2763篇 |
2003年 | 2466篇 |
2002年 | 2188篇 |
2001年 | 1596篇 |
2000年 | 1328篇 |
1999年 | 1041篇 |
1998年 | 710篇 |
1997年 | 549篇 |
1996年 | 465篇 |
1995年 | 392篇 |
1994年 | 311篇 |
1993年 | 228篇 |
1992年 | 200篇 |
1991年 | 144篇 |
1990年 | 121篇 |
1989年 | 113篇 |
1988年 | 73篇 |
1987年 | 66篇 |
1986年 | 41篇 |
1985年 | 43篇 |
1984年 | 35篇 |
1983年 | 22篇 |
1982年 | 27篇 |
1981年 | 15篇 |
1980年 | 24篇 |
1979年 | 5篇 |
1978年 | 6篇 |
1977年 | 8篇 |
1975年 | 13篇 |
1959年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
掺炼糠醛抽出油生产高质量沥青 总被引:3,自引:0,他引:3
掺炼糠醛抽出油,改变了丙烷脱沥青装置原料性质,通过调整部分操作参数,可提高轻脱油和重脱油的收率,改善脱油沥青质量,直接生产出合格的高标号道路沥青。 相似文献
122.
三元乙丙橡胶卷材在地下防水工程中的应用 总被引:2,自引:0,他引:2
地下防水工程既是一项系统工程,又是一项隐蔽工程,如何选择防水材料和控制工程质量显得到关重要。本文结合工程实例,介绍了三元乙丙橡胶卷材在地下防水工程中的应用,分析了三元乙丙卷材的特点,提出了地下水的技术方案,施工操作要求,质量过程控制要点和施工注意项,本文对三元乙丙卷材的工程应用具有指导和借鉴意义。 相似文献
123.
分析了中油站产生一些油品质量事故的情况和成因。指出加油站油品的质量事故主要是管理不善,要杜绝加油站油品质量事故,必须坚持执行《中国石油化工集团销售企业油品质管理办法》。 相似文献
124.
云南省水环境状况及问题分析 总被引:2,自引:0,他引:2
根据2000年云南省主要河流水质监测评价结果,全省评价河段总长9280km中,水质为Ⅰ-Ⅲ类的河长占76.3%,总体上,云南省内各大水系水质良好,但水污染总体上正在加重,从1985-2000年,Ⅰ类河长年均减少2.3%,V类河长年均增长0.6%,废污水直接排入江河是引起污染的重要原因。水环境问题已成为社会经济可持续发展的关键问题,要切实加强水资源的保护,科学地开发利用水土资源,为了有效地改善水环境的质量,污染控制应从源头开始并采取综合治理措施。 相似文献
125.
张华 《石油化工管理干部学院学报》2007,9(2):40-42
我国的工程造价管理体系正在逐步规范,并建立以市场形成价格为主的价格体制;改革现行工程定额管理方式,这些对造价工程师的执业能力和水平提出了更高的要求。造价工程师面临机遇、挑战,必须不断调整知识结构,提高整体素质,拓展个人在专业领域的空间。 相似文献
126.
Water quality assessment of a recently refilled reservoir: The case of Bütgenbach Reservoir, Belgium
Anna Lourantou Jean-Pierre Thomé Anne Goffart 《Lakes & Reservoirs: Research and Management》2007,12(4):261-274
Bütgenbach Reservoir is situated in the High Ardennes plateau in eastern Belgium (50°25′N; 6°13′E). It is used principally for flood control and for production of hydroelectric energy. It has been subjected to a previous series of studies because of its eutrophication problems and their impacts on the local economy. Bütgenbach Reservoir was emptied during spring 2004 for dam restoration, being refilled in mid‐September of the same year. Selected physicochemical and biological parameters (temperature, dissolved oxygen, pH, inorganic and organic nutrients, chlorophyll‐a) were measured fortnightly during the lake's productive season (mid‐April to mid‐October 2005) at three sampling sites throughout the water column. The water quality conditions after refilling of the lake were compared to previous studies accomplished at the same sampling sites (prior to emptying the lake). The actual trophic status was mesotrophic to eutrophic, based on the combination of total phosphorous and chlorophyll‐a concentrations, as well as water transparency. Bütgenbach Reservoir generally exhibits good water quality, based on the French water quality system SEQ‐eau. A longitudinal decrease in water quality was observed from upstream to downstream, because mainly of the differences in lake bottom morphology and water residence time, and their impacts on nutrient distribution in the lake. 相似文献
127.
《Drying Technology》2007,25(1):75-84
This article proposes a multiscale computational model able to calculate energy consumption in a batch lumber kiln. A dual-scale computational model of wood drying deals with the boards/stack interaction and serves as a basis for the present work. A new module was added here that calculates heat losses through kiln walls (convection, condensation) and the energy used by each kiln component (fans, heating elements, humidifier, vacuum pump, etc.). The corresponding mathematical formulation is presented and then theoretical results are compared to those collected in an industrial vacuum kiln. As application example, the effect of air reversal, air velocity, and kiln insulation are exhibited, which depicts the great potential and prospects of this new tool for energy savings in relation to the product quality. 相似文献
128.
Dodo J. Thampapillai 《国际能源研究杂志》1985,9(2):179-192
Three social objectives figure prominently in the extraction of finite energy resources, namely income maximization, environmental quality, and inter-generational concern. Owing to lack of complementarity, the pursuit of these objectives often results in conflicts. As a result, extraction strategies should be based on the determination of trade-offs between the objectives. The paper deals with the formulation and illustration of a systems model to determine these trade-offs. The recognition of such trade-offs results in a greater conservation of the finite energy resource, and hence could act as an incentive for the development of alternative energy sources. 相似文献
129.
The aim of this study was to evaluate the effects of paste properties on residence time during drying in a spouted bed dryer with inert bodies. The effect of paste solids content, surface tension, and viscosity on the residence time distribution and the mean residence times were studied using factorial experimental designs. The inert bodies used were glass and polyethylene beads. The mean residence times varied from 13.6 to 16.3 and 12.2 to 17.7 min for drying on glass and polyethylene beads, respectively. The analysis of variance showed that mean residence times significantly depended on solids content and surface tension for glass beads and also on viscosity for polyethylene beads. The residence time distributions for all conditions studied fitted well to the perfect mixing cell when applying the continuous stirred vessels in series model analysis. The powder density, flowability, and particle size depended on paste properties and inert type. 相似文献
130.
简易高性能纳秒脉冲发生器 总被引:2,自引:0,他引:2
为了实现电子散射飞行时间谱仪电子束的脉冲化及产生时一幅变换器的启动或停止信号。我们利用开关晶体管的雪崩特性研制了一个性能好,成本低的纳秒脉冲发生器。该发生器输出上升时间好于Ins,幅度达10V的负尖脉冲,用作时一幅变换器的启动或停止信号;也输出上升时间约3ns,幅度5-30V连续可调和宽度5-230ns可调的正脉冲,用作电子束脉冲化的调制信号,脉冲重复率为150×10^3s^-1。它可广泛用于类似 相似文献