全文获取类型
收费全文 | 75289篇 |
免费 | 5377篇 |
国内免费 | 1974篇 |
专业分类
电工技术 | 4441篇 |
综合类 | 6424篇 |
化学工业 | 6848篇 |
金属工艺 | 2837篇 |
机械仪表 | 3505篇 |
建筑科学 | 12522篇 |
矿业工程 | 1892篇 |
能源动力 | 1205篇 |
轻工业 | 18052篇 |
水利工程 | 3462篇 |
石油天然气 | 2496篇 |
武器工业 | 339篇 |
无线电 | 3761篇 |
一般工业技术 | 4410篇 |
冶金工业 | 3864篇 |
原子能技术 | 584篇 |
自动化技术 | 5998篇 |
出版年
2024年 | 457篇 |
2023年 | 1142篇 |
2022年 | 1879篇 |
2021年 | 2530篇 |
2020年 | 2550篇 |
2019年 | 2020篇 |
2018年 | 1912篇 |
2017年 | 2215篇 |
2016年 | 2314篇 |
2015年 | 2529篇 |
2014年 | 5267篇 |
2013年 | 4518篇 |
2012年 | 5338篇 |
2011年 | 5512篇 |
2010年 | 4324篇 |
2009年 | 4551篇 |
2008年 | 3996篇 |
2007年 | 4768篇 |
2006年 | 4327篇 |
2005年 | 3524篇 |
2004年 | 3101篇 |
2003年 | 2819篇 |
2002年 | 2444篇 |
2001年 | 1788篇 |
2000年 | 1494篇 |
1999年 | 1207篇 |
1998年 | 781篇 |
1997年 | 632篇 |
1996年 | 544篇 |
1995年 | 443篇 |
1994年 | 343篇 |
1993年 | 250篇 |
1992年 | 234篇 |
1991年 | 142篇 |
1990年 | 111篇 |
1989年 | 109篇 |
1988年 | 86篇 |
1987年 | 89篇 |
1986年 | 57篇 |
1985年 | 69篇 |
1984年 | 55篇 |
1983年 | 32篇 |
1982年 | 35篇 |
1981年 | 18篇 |
1980年 | 32篇 |
1979年 | 5篇 |
1978年 | 5篇 |
1977年 | 6篇 |
1966年 | 5篇 |
1959年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Kevin Yale Teichman 《Indoor air》1994,4(3):202-211
Deciding between the different policy approaches available for reducing human exposures to indoor pollutants is an exceptionally complex task. These options can range from waiting until more definitive information is available to enacting regulatory standards, with many variations in between. This paper presents some of the factors policy-makers must consider in establishing indoor air quality policies, and the role researchers should play in ensuring that indoor air policies are based on the best available scientific information. 相似文献
42.
从油田现场反应的情况出发,对调整井固井,尾管固井,大位移井套管固井和其他固井的质量问题进行了分析,针对各种问题产生的原因,提出了相应换解决办法。 相似文献
43.
立式平管板U形管束的压水堆核电站蒸汽发生器安装至瞬变工况期间,管板上表面的铁基金属残余物的堆积和外来物的存在,以及商业运行后管板、传热管、管子支撑板等的低流速区域里沉积物的堆积要求进行蒸汽发生器的清洁度检查。介绍了蒸汽发生器二次侧清洁度的视频检查技术。该技术适用于蒸汽发生器安装至瞬变工况和投入商业运行后可能发生污染的各阶段的清洁度检查。 相似文献
44.
The interaction of different metal oxides such as Co3O4, NiO, Al2O3, Cr2O3, Fe2O3 and SiO2 with Na2SO4 at a temperature of 1100 and 1200 K in flowing oxygen has been studied. The thermogravimetric studies for each system were
carried out as a function of Na2SO4 in the mixture. The presence of different constituents in the reaction products were identified by X-ray diffraction analysis
and the morphologies of the reaction products were characterized using metallography and scanning electron microscopy (SEM).
The formation of products was also investigated by thermodynamic computation of free energies of the reactions and the study
of relevant equilibrium phase diagrams. The soluble species in the aqueous solutions of the reaction products were determined
quantitatively using atomic absorption spectrophotometry.
The high temperature interaction products usually contain a 3-phase structure namely, Na2O·M2O
x
, M2O
x
and metal sulphide and/or metal sulphate. The formation of Na2O·M2O
x
depends upon the solid state solubility of metal oxide in the molten salt at high temperatures. Under limited solubility
conditions Na2O·M2O
x
is invariably formed, but as soon as this condition is relaxed the oxide. M2O
x
, precipitates and forms a separate phase. 相似文献
45.
Kwang Soo Lee In Soo Park & Dong Sun Lee 《International Journal of Food Science & Technology》1996,31(1):7-13
The aim of this study was to design a modified atmosphere package for a mixed vegetable salad consisting of 75 g of cut carrot, 55 g of cut cucumber, 20 g of sliced garlic and 50 g of whole green pepper. Respiration data of all the components were combined with film permeability data to predict package atmospheres and design optimal packages for experimental testing for improved shelf-life of the produce. The optimal package avoided minimum O2 and maximum CO2 tolerance limits, and chilling injury temperatures for any component. A pouch form package made of 27 mm low density polyethylene developed a modified atmosphere of 2.0–2.1% O2 and 5.5–5.7% CO2 , which was beneficial for all components and provided better quality retention than other test packages. 相似文献
46.
探讨了过滤器孔径对6063铝合金铸锭组织和性能的影响规律。在此基础上指出,在过滤工艺恰当时,不仅可以减少铸锭中的夹杂物,而且可以有效地防止裂纹、羽毛晶等连续铸锭中的常见缺陷。 相似文献
47.
通过具体工程实践,在吸收现有滑模工艺技术的基础上,对平台扭转、中心垂直度控制等关键工艺进行创新,为提高工程质量提供技术保证,达到了创省级优质工程的效果。 相似文献
48.
Vibro-fluidized beds are widely used in drying sticky powders and agglomerated materials as milk powder. Using a vibro-fluidized laboratory scale dryer, this work is aiming at analyzing preliminarily the effect of its operational variables on the drying kinetics and characteristics of whole milk powder. The full-factorial design technique with three replications at the central point has been employed to generate data and correlations to quantify the effect of inlet air temperature, air flow rate, and vibration bed amplitude on the drying curves and the milk powder properties related to its faster reconstitution in water (as tapped density, Hausner cohesion ratio, agglomerate size distribution, and internal pore concentration). Results obtained are analyzed and discussed to identify the adequate operation condition for final drying whole milk powder in vibro-fluidized beds, assuring a high product quality. 相似文献
49.
Baak K. Taeli 《Lakes & Reservoirs: Research and Management》2006,11(3):149-168
Lake Mogan, located in the steppes of central Anatolia, is a vital Turkish ecological system, in terms of its water resources, flora and fauna. The lake also is a unique recreational area for Ankara, the capital of Turkey. However, the lake is currently threatened by severe pollution, being under the risk of serious degradation because of (i) uncontrolled urbanization; (ii) point and non‐point source pollution; (iii) inefficient sewerage systems; (iv) sediment transportation and pollution via influent creeks to the lake; (v) uncontrolled soil erosion in its drainage basin; (vi) inappropriate flood control measures; and (vii) severe degradation of the natural wetlands within its drainage basin. This study evaluates the influence of its influent creeks on the water quality of Lake Mogan, mainly because the creeks are believed to be responsible for the major pollutant load reaching the lake, and because the extensive database documenting this situation has not previously been critically evaluated. Accordingly, this study reviews (i) change in the water quality of Lake Mogan between 1993 and 2002; (ii) the water quality classification of the major influent creeks feeding Lake Mogan; and (iii) the influence of the influent creeks on the water quality of the lake between 1993 and 2004. 相似文献
50.
山东改造工程旧房质量检测 总被引:5,自引:4,他引:1
结合某成品仓库改作商业用房的工程实例,对该建筑进行了详细的检测与分析,并根据结果提出了针对性的加固方案,并对加固效果进行了探讨,为工程改造提供了依据,可供类似工程借鉴。 相似文献