全文获取类型
收费全文 | 73845篇 |
免费 | 7495篇 |
国内免费 | 4544篇 |
专业分类
电工技术 | 6014篇 |
技术理论 | 3篇 |
综合类 | 6109篇 |
化学工业 | 8719篇 |
金属工艺 | 4762篇 |
机械仪表 | 4630篇 |
建筑科学 | 12951篇 |
矿业工程 | 2924篇 |
能源动力 | 2569篇 |
轻工业 | 5542篇 |
水利工程 | 3523篇 |
石油天然气 | 5080篇 |
武器工业 | 1488篇 |
无线电 | 4578篇 |
一般工业技术 | 6592篇 |
冶金工业 | 3143篇 |
原子能技术 | 855篇 |
自动化技术 | 6402篇 |
出版年
2024年 | 301篇 |
2023年 | 977篇 |
2022年 | 2023篇 |
2021年 | 2348篇 |
2020年 | 2657篇 |
2019年 | 2097篇 |
2018年 | 2002篇 |
2017年 | 2636篇 |
2016年 | 2841篇 |
2015年 | 2940篇 |
2014年 | 4703篇 |
2013年 | 4419篇 |
2012年 | 5727篇 |
2011年 | 5820篇 |
2010年 | 4381篇 |
2009年 | 4415篇 |
2008年 | 3840篇 |
2007年 | 4797篇 |
2006年 | 4431篇 |
2005年 | 3775篇 |
2004年 | 3190篇 |
2003年 | 2627篇 |
2002年 | 2281篇 |
2001年 | 1966篇 |
2000年 | 1592篇 |
1999年 | 1307篇 |
1998年 | 1074篇 |
1997年 | 815篇 |
1996年 | 800篇 |
1995年 | 635篇 |
1994年 | 496篇 |
1993年 | 349篇 |
1992年 | 307篇 |
1991年 | 205篇 |
1990年 | 187篇 |
1989年 | 142篇 |
1988年 | 84篇 |
1987年 | 62篇 |
1986年 | 54篇 |
1985年 | 37篇 |
1984年 | 26篇 |
1981年 | 23篇 |
1980年 | 70篇 |
1979年 | 51篇 |
1965年 | 26篇 |
1964年 | 34篇 |
1960年 | 23篇 |
1959年 | 37篇 |
1956年 | 29篇 |
1955年 | 32篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
22.
23.
秦山300MW核电机组全范围仿真机测试验收 总被引:1,自引:1,他引:0
介绍了秦山300MW核电机组全范围仿真机的测试验收的整个过程,包括:验收测试规程的形成,工厂内部预测试和工厂用户测试。并分析了测试验收过程中存在的重大问题及解决的办法。 相似文献
24.
近年来,国际上标准参考物质的种类与数量急剧增加,一些重要的领域,象地球化学、环境科学、生物学等都有了相应的SRM。国内研制SRM的工作也十分活跃。 标准样品必须均匀,故在分析定值和样品发行前,需要先作均匀性检验。由于均匀性是一个相对的概念,它与各个元素在SRM中的分布紧密相关。取样量直接影响均匀性的好坏。因此,当给出SRM中某元素的均匀性数值时,必须注明相应的取样量。由于仪器中子活化分析法(INAA)具有灵敏度高、不破坏试样、且可同时测定多种元素等特点,因此可在较小的取样量情况下,实现对SRM中多种痕量元素的均匀性检验。 相似文献
25.
Thermal sprayed aluminum and zinc provide long-term (> 20 years to first maintenance) corrosion control coatings. However,
this application is usually more expensive than painting or galvanizing if thermal spraying (metallizing) is not integrated
into the design and fabrication phases of new construction and repair projects. Aluminum and zinc metallized coatings are
tough enough to withstand fabrication, transportation, and assembly operations. The improved capabilities and productivity
of metallizing equipment for aluminum and zinc spraying are a major factor in their current cost competitiveness. The net
result is that the cost difference between metallizing, paint, and galvanizing is getting closer every day. Even though the
initial application cost of metallizing may be higher, the life cycle cost (LCC) and average equivalent annual costs (AEAC)
are lower than paint coating systems. Metallizing LCCs, when properly engineered into the construction schedule, are equal
to or less than paint coating LCCs. This article summarizes some metallizing considerations for installing improved corrosion
control coating systems in new construction and in maintenance and repair of infrastructure.
Editor’s Note: The following constants have been used to convert between English and Metric dimensions: 1ft2-0.0929 m2; 1lb/ft2-4.89 kg/m2; 1 mil=0.025mm.
Presented at the 5th National Thermal Spray Conference (NTSC-93), Infrastructure Maintenance and Repair Session, 10 June 1993,
Anaheim, CA. 相似文献
26.
The deposition of copper by cold gas dynamic spraying has attracted much interest in recent years due to the capability to
deposit low-porosity oxide-free coatings. However, it is generally found that as-deposited copper has a signicantly greater
hardness, and potentially lower ductility, than bulk material. In this article, copper was deposited by cold spraying using
helium as the driving gas at both 298 and 523 K. Evidence is presented indicating that the material sprayed at the lower temperature
exhibits a lower dislocation density throughout the grain structure than the material sprayed at the higher temperature. The
low stacking fault energy of copper restricts recovery during annealing, and thus microstructural changes during annealing
only proceed once recrystallization begins. The material sprayed at low temperature (with the low dislocation density) exhibited
recrystallization at annealing temperatures as low as 373 K with a corresponding reduction in hardness. However, the copper
sprayed with helium at 523 K was resistant to annealing at temperatures up to 473 K where the dislocations in the structure
prevented recrystallization. However, at higher temperatures, recrystallization did proceed (with corresponding reductions
in hardness). The fracture behavior of the copper that was cold sprayed with helium at 523 K, both in the as-sprayed condition
and following annealing, was measured and explained in terms of the annealing mechanisms proposed.
The original version of this paper was published in the CD ROM Thermal Spray Connects: Explore Its Surfacing Potential, International
Thermal Spray Conference, sponsored by DVS, ASM International, and HW International Institute of Welding, Basel, Switzerland,
May 2–4, 2005, DVS-Verlag GmbH, Düsseldorf, Germany. 相似文献
27.
The characterization of La
x
Sr1−x
MnO3 powders produced by spray pyrolysis using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observation,
specific surface area (Brunauer-Emett-Teller), and particle size distribution measurements shows that the resultant large
particles are loose agglomerates consisting of many small particles. However, the sintered tiny particles can form hard agglomerates,
and the particle size increases remarkably. The structures of the powders before and after sintering were identified by x-ray
diffraction (XRD). The study of the electrical property of the powder shows that the powder is a metallic conductor. In a
reducing atmosphere, the powder can be decomposed. When the powder is cofired with yttria-stabilized zirconia 5% (YSZ) powder
at 1200 °C for 5 h, no new phase is produced, and the powder remains a single provskite hexagonal-rhombohedral structure. 相似文献
28.
The constrained blister test is investigated through finite element analysis to determine the applicabilities and the limitations of the new technique. Numerical results confirm that the strain energy release rate asymptotically approaches a constant value. These results also show that the test technique and the approximate solution for strain energy release rate are applicable for some practical cases. 相似文献
29.
J.Dougherty S.Ziebold 《硫酸工业》2005,(3):8-13
开发了一种用于布朗扩散型纤维除雾器的便携式现场测试装置,用这套装置可在现场测定纤维床阻力,从而对元件制造水平进行评价和比较,或在维修期间预测清洗后元件的操作性能。介绍便携式现场测试装置的设备布局、安装和运行,并对整体充填、平行缠绕、斜交叉缠绕纤维床及同心组合纤维床进行比较。此外,论述了硫酸装置工艺气体压降的价值。 相似文献
30.
以己二异氰酸酯(HDI)改性聚酯树脂与氨基树脂配制成家电用卷材涂料。阐述了氨酯键对涂膜性能的贡献。探讨了HDI用量对涂膜性能的影响。 相似文献