全文获取类型
收费全文 | 64597篇 |
免费 | 6687篇 |
国内免费 | 4225篇 |
专业分类
电工技术 | 5085篇 |
技术理论 | 4篇 |
综合类 | 5568篇 |
化学工业 | 9312篇 |
金属工艺 | 3995篇 |
机械仪表 | 4182篇 |
建筑科学 | 5044篇 |
矿业工程 | 1918篇 |
能源动力 | 1718篇 |
轻工业 | 7436篇 |
水利工程 | 1623篇 |
石油天然气 | 2874篇 |
武器工业 | 780篇 |
无线电 | 7199篇 |
一般工业技术 | 6294篇 |
冶金工业 | 2459篇 |
原子能技术 | 730篇 |
自动化技术 | 9288篇 |
出版年
2024年 | 337篇 |
2023年 | 1083篇 |
2022年 | 2240篇 |
2021年 | 2843篇 |
2020年 | 2198篇 |
2019年 | 1682篇 |
2018年 | 1944篇 |
2017年 | 2202篇 |
2016年 | 2018篇 |
2015年 | 3017篇 |
2014年 | 3633篇 |
2013年 | 4306篇 |
2012年 | 5124篇 |
2011年 | 5498篇 |
2010年 | 5001篇 |
2009年 | 4728篇 |
2008年 | 4828篇 |
2007年 | 4407篇 |
2006年 | 3895篇 |
2005年 | 3111篇 |
2004年 | 2251篇 |
2003年 | 1860篇 |
2002年 | 1783篇 |
2001年 | 1513篇 |
2000年 | 1059篇 |
1999年 | 756篇 |
1998年 | 472篇 |
1997年 | 392篇 |
1996年 | 297篇 |
1995年 | 258篇 |
1994年 | 180篇 |
1993年 | 139篇 |
1992年 | 90篇 |
1991年 | 98篇 |
1990年 | 74篇 |
1989年 | 39篇 |
1988年 | 24篇 |
1987年 | 21篇 |
1986年 | 22篇 |
1985年 | 8篇 |
1984年 | 9篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1981年 | 10篇 |
1980年 | 21篇 |
1979年 | 5篇 |
1976年 | 4篇 |
1973年 | 3篇 |
1959年 | 9篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Shou-ren Wang Hao-ran Geng Lin-hai Hui Ying-zi Wang 《Journal of Materials Engineering and Performance》2007,16(1):113-118
A multiphase reticulated porous ceramic (RPC) as Si3N4–Al2O3–SiO2 was fabricated by replication techniques. Proper volumes of additives and twice sinter- twice immerse process endow the RPC
an excellent crack healing and submerging property. The compressive strength and fracture toughness improved owing to the
crack bridging behavior. The existence of pores in struts in RPC blunt the crack tip and increased the external force needed
to propagate the crack. The mechanisms play a beneficial role in enhancing the compressive strength and fracture strength.
Si3N4 RPC with additives of 5%Al and 5% Al2O3 yielded the compressive strength of 9.8 MPa and fracture toughness of 0.3 MPa m1/2. 相似文献
42.
43.
44.
45.
46.
Wei Hui 《Frontiers of Computer Science in China》2007,1(3):361-372
Almost all applications of Artificial Neural Networks (ANNs) depend mainly on their memory ability. The characteristics of
typical ANN models are fixed connections, with evolved weights, globalized representations, and globalized optimizations,
all based on a mathematical approach. This makes those models to be deficient in robustness, efficiency of learning, capacity,
anti-jamming between training sets, and correlativity of samples, etc. In this paper, we attempt to address these problems
by adopting the characteristics of biological neurons in morphology and signal processing. A hierarchical neural network was
designed and realized to implement structure learning and representations based on connected structures. The basic characteristics
of this model are localized and random connections, field limitations of neuron fan-in and fan-out, dynamic behavior of neurons,
and samples represented through different sub-circuits of neurons specialized into different response patterns. At the end
of this paper, some important aspects of error correction, capacity, learning efficiency, and soundness of structural representation
are analyzed theoretically. This paper has demonstrated the feasibility and advantages of structure learning and representation.
This model can serve as a fundamental element of cognitive systems such as perception and associative memory. 相似文献
47.
浅谈火灾调查的边缘化趋势 总被引:1,自引:0,他引:1
从火灾调查实际工作状态出发,提出火灾调查存在地位边缘化的趋势,并在分析边缘化趋势原因的基础上提出了相应的对策,供火灾调查同仁探讨。 相似文献
48.
Two-photon pumping of a random laser 总被引:1,自引:0,他引:1
Burin A.L. Hui Cao Ratner M.A. 《IEEE journal of selected topics in quantum electronics》2003,9(1):124-127
Random lasing originates from pumping disordered materials by high-intensity and high-frequency light. The performance of random lasers is restricted due to the absorption of pumping light within the interfacial layer. The lifetime of optical modes there is short due to the emission of photons to the outside, and it is hard to pump them sufficiently for lasing. The opportunity to excite the modes far from the material surface using two-photon absorption is investigated within the diffusion model. The authors show that lasing requires lower pump power for the two-photon pumping mechanism under conditions of negligible absorption of the emitted light. Experimental implications and restrictions are discussed. 相似文献
49.
本文在浅埋地下建筑风冷热泵空调系统围护结构传热动态模拟的基础上,通过对南京市太园地下旅社围护结构传热的实时测试,验证动态传热模型及计算机模拟方法的可行性和正确性,为浅埋地下建筑风冷热泵空调系统的装机容量、节能指标和设计计算提供一定的理论依据。 相似文献
50.
采用种子乳液聚合法制备了含有PBA\PMMA\PS三种组分的丙烯酸酯类抗冲型改性剂ACR,在ACR的幔层结构中引入接枝剂甲基丙烯酸烯丙酯(ALMA)来完善幔层结构,从而实现核一壳之间良好的结合,用红外光谱(FTIR)和差示扫描量热法(DSC)对ACR的组成和结构进行表征。研究结果表明:由PBA\PMMA\PS三组分构成的ACR在抗冲击性能上要略优于由简单的PBA\PMMA构成的ACR,苯乙烯单体(St)最多可以取代大约1/3壳层的甲基丙烯酸甲酯(MMA),甲基丙烯酸烯丙酯(ALMA)的引入对幔层结构的完善起了显著的作用。 相似文献