全文获取类型
收费全文 | 14564篇 |
免费 | 1353篇 |
国内免费 | 551篇 |
专业分类
电工技术 | 1227篇 |
技术理论 | 1篇 |
综合类 | 1273篇 |
化学工业 | 1047篇 |
金属工艺 | 1208篇 |
机械仪表 | 1697篇 |
建筑科学 | 1661篇 |
矿业工程 | 322篇 |
能源动力 | 550篇 |
轻工业 | 1543篇 |
水利工程 | 189篇 |
石油天然气 | 467篇 |
武器工业 | 272篇 |
无线电 | 571篇 |
一般工业技术 | 1993篇 |
冶金工业 | 1439篇 |
原子能技术 | 103篇 |
自动化技术 | 905篇 |
出版年
2024年 | 108篇 |
2023年 | 240篇 |
2022年 | 395篇 |
2021年 | 432篇 |
2020年 | 485篇 |
2019年 | 370篇 |
2018年 | 402篇 |
2017年 | 466篇 |
2016年 | 539篇 |
2015年 | 562篇 |
2014年 | 888篇 |
2013年 | 862篇 |
2012年 | 828篇 |
2011年 | 1098篇 |
2010年 | 815篇 |
2009年 | 852篇 |
2008年 | 754篇 |
2007年 | 882篇 |
2006年 | 834篇 |
2005年 | 734篇 |
2004年 | 638篇 |
2003年 | 552篇 |
2002年 | 497篇 |
2001年 | 445篇 |
2000年 | 319篇 |
1999年 | 296篇 |
1998年 | 206篇 |
1997年 | 200篇 |
1996年 | 175篇 |
1995年 | 127篇 |
1994年 | 108篇 |
1993年 | 79篇 |
1992年 | 44篇 |
1991年 | 36篇 |
1990年 | 37篇 |
1989年 | 26篇 |
1988年 | 20篇 |
1987年 | 17篇 |
1986年 | 12篇 |
1985年 | 9篇 |
1984年 | 11篇 |
1983年 | 13篇 |
1982年 | 8篇 |
1981年 | 5篇 |
1980年 | 8篇 |
1979年 | 3篇 |
1965年 | 4篇 |
1964年 | 5篇 |
1963年 | 3篇 |
1959年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
中国石化扬子石化股份公司烯烃厂2^#丁二烯装置使用某厂生产的44台ZE型离心泵。其机械密封使用寿命短,机封的小弹簧及辅助密封环在选材上存在一些问题。通过在实践中摸索与总结。对弹簧及密封环选用合适的材料,对原机封的结构进行改进,收到良好效果。 相似文献
52.
本文通过对某液压挖掘机工作装置实验样本长度的研究,详细讨论了样本长度的确定方法,重点分析了趋势曲线拟合法,提出了样本长度精度区间分析的方法,并在处理大量实验数据的基础上,从载荷分布及寿命估算的角度做了实际的验证.编制了应用程序,使样本长度确定至寿命估算整个过程程序化. 相似文献
53.
54.
Reviews the book, Qualité de vie et drogues. Place aux jeunes (1986). In this volume, the author shares his initiatives in the plan of therapeutic and preventive intervention. This book discusses drug use and quality of life in young people. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
55.
提高连续油管使用寿命的方法 总被引:2,自引:1,他引:1
从采用软件跟踪疲劳寿命 ,截断法 ,变径连续油管 ,反转使用连续油管 ,防止连续油管损伤 ,合理配置设备 6个方面讨论了控制管串疲劳 ,提高连续油管使用寿命的方法 ,并得出结论 :控制管串疲劳的方法中 ,最有效的方法是实际作业截断法。指出要尽量减少连续油管在带内压下工作 ,也要研究开发降阻性能好的工作液 ,以延长连续油管使用寿命、降低作业风险。 相似文献
56.
Many new speciality polymers have been developed in the last few years. In this paper polymeric stabilizers (antioxidants, flame retardants and ultraviolet stabilizers) will be discussed. Polymeric antioxidants of the hindered-phenol type, copolymers of 2,6-ditertiarybutyl-4-vinyl(or isopropenyl)phenol with styrene, methyl methacrylate, or more importantly butadiene or isoprene have been prepared; hydrogenation of the latter copolymers gave copolymers of the two polymerizable phenolic antioxidants with ethylene or ethylene/propylene. The polymeric antioxidants have been blended with diene polymers and selected polyolefins and have improved the long-term oxidative stability of these polymers. Polymeric flame retardants have been prepared by copolymerizing styrene and/or acrylonitrile with acrylates and methacrylates of aliphatic bromine-containing alcohols or bromine-containing phenols. Polymers with polymer-bound flame retardants have a higher limiting oxygen index compared with the original polymer. A new class of polymerizable ultraviolet stabilizers has also been developed; these stabilizers are styryl, α-methylstyryl, acryloyl and methacryloyl derivatives of 2(2-hydroxyphenyl)2H-benzotriazoles. These monomers have been copolymerized with styrene, acrylates and methacrylates. 2(2-Hydroxyphenyl)2H-benzotriazoles substituted in the 4 position of the benzotriazole ring with hydroxyl, acetoxy or carboxyl groups suitable for incorporation into polyesters, polycarbonates, polyamides and epoxy resins have also been synthesized. All 2(2-hydroxyphenyl)2H-benzotriazole ultraviolet absorbers and the polymers into which they are incorporated have high light absorbency with γmax between 330 and 350 nm and extinction coefficients in some cases as high as 4.5 × 104 1 mol?1 cm?1. 相似文献
57.
58.
Wide variability exists with respect to how breast cancer survivors respond to common psychological and psychosocial challenges of their disease, ranging from posttraumatic stress disorder to posttraumatic growth. This cross-sectional study examined contextual, disease-related, and intraindividual predictors of posttraumatic growth in 224 randomly selected breast cancer survivors. A series of hierarchical regression analyses found that age at diagnosis, marital status, employment, education, perceived intensity of disease, and active coping accounted for 34%, 35%, and 28% of the variance in growth in relationships with others, new possibilities, and appreciation for life. These findings suggest that a more comprehensive model of growth will be helpful in understanding the various factors that play a role in breast cancer survivors' perception of psychological and psychosocial growth. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
59.
通过对真丝绸整个产品生命过程的分析,对其进行了生命周期评价,说明了丝绸与其产地环境之间的联系和影响,尝试寻求两者之间的和谐关系,提出了清洁生产工艺的规划和各种行之有效的对策和措施,尝试了对环境友好的丝绸印染工艺的生态设计。 相似文献
60.
An existing extensive database on the isothermal and thermomechanical fatigue behaviour of high-temperature titanium alloy
EVII 834 and dispersoid-strengthened aluminum alloy X8019 in SiC particle-reinforced as well as unreinv conditions was used
to evaluate both the adaptability of fracture mechanics approaches to TMF and the resulting predictive capabilities of determining
material life by crack propagation consideration. Selection of the correct microstructural concepts was emphasised and these
concepts were, then adjusted by using data from independent experiments in order to avoid any sort of fitting. It is shown
that the cyclic /-integral (δJeff concept) is suitable to predict the cyclic lifetime for conditions where the total crack propagation rate is approximately
identical to pure fatigue crack growth velocity. In the case that crack propagation is strongly affected by creep, the creep-fatigue
damage parameter δCF introduced by Riedel can be successfully applied. If environmental effects are very pronounced, the accelerating influence
of corrosion on fatigue crack propagation can no longer implicitly be taken into account in the fatigue crack growth law.
Instead, a linear combination of the crack growth rate contributions from plain fatigue (determined in vacuum) and from environmental
attack is assumed and found to yield a satisfactory prediction, if the relevant corrosion process is taken into account. 相似文献