全文获取类型
收费全文 | 3210篇 |
免费 | 229篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 51篇 |
综合类 | 10篇 |
化学工业 | 710篇 |
金属工艺 | 45篇 |
机械仪表 | 99篇 |
建筑科学 | 121篇 |
矿业工程 | 5篇 |
能源动力 | 74篇 |
轻工业 | 605篇 |
水利工程 | 19篇 |
石油天然气 | 20篇 |
无线电 | 246篇 |
一般工业技术 | 518篇 |
冶金工业 | 546篇 |
原子能技术 | 29篇 |
自动化技术 | 348篇 |
出版年
2023年 | 27篇 |
2022年 | 109篇 |
2021年 | 127篇 |
2020年 | 77篇 |
2019年 | 93篇 |
2018年 | 99篇 |
2017年 | 112篇 |
2016年 | 114篇 |
2015年 | 98篇 |
2014年 | 136篇 |
2013年 | 173篇 |
2012年 | 144篇 |
2011年 | 196篇 |
2010年 | 124篇 |
2009年 | 138篇 |
2008年 | 136篇 |
2007年 | 149篇 |
2006年 | 101篇 |
2005年 | 86篇 |
2004年 | 92篇 |
2003年 | 76篇 |
2002年 | 70篇 |
2001年 | 58篇 |
2000年 | 44篇 |
1999年 | 52篇 |
1998年 | 184篇 |
1997年 | 114篇 |
1996年 | 92篇 |
1995年 | 41篇 |
1994年 | 46篇 |
1993年 | 36篇 |
1992年 | 21篇 |
1991年 | 28篇 |
1990年 | 17篇 |
1989年 | 28篇 |
1988年 | 13篇 |
1987年 | 18篇 |
1986年 | 9篇 |
1985年 | 20篇 |
1984年 | 8篇 |
1983年 | 9篇 |
1982年 | 8篇 |
1981年 | 9篇 |
1980年 | 9篇 |
1979年 | 6篇 |
1978年 | 10篇 |
1977年 | 10篇 |
1976年 | 21篇 |
1975年 | 8篇 |
1972年 | 5篇 |
排序方式: 共有3446条查询结果,搜索用时 15 毫秒
1.
2.
Tallison O. Abreu Roterdan F. Abreu Felipe F. do Carmo Wellington V. de Sousa Helenilson de O. Barros José E.V. de Morais João P.C. do Nascimento Marcelo A.S. da Silva Sergei Trukhanov Alex Trukhanov Larissa Panina Charanjeet Singh Antonio S.B. Sombra 《Ceramics International》2021,47(11):15424-15432
This work presents the dielectric properties of YNbO4 (YNO)–TiO2 composites in the microwave range. X-ray diffraction analysis demonstrates that the addition of TiO2 to YNO results in the formation of a Y(Nb0.5Ti0.5)2O6 phase. In the microwave range, the values of permittivity and dielectric loss did not present major changes with the increment of TiO2. Moreover, the addition of TiO2 results in an improvement in the thermal stability of YNO, with YNO63 demonstrating a resonant frequency of ?8.96 ppm.°C?1. We utilised numerical simulations to evaluate the behaviour of these materials as dielectric resonator antennae and it is found that they exhibit a reflection coefficient below ?10 dB at the resonant frequency, with a realised gain of 4.94 – 5.76 dBi, a bandwidth of 665–1050 MHz and a radiation efficiency above 84%. Our results indicate that YNO–TiO2 composites are interesting candidates for microwave operating devices. 相似文献
3.
Vanessa Modelski Schatkoski Thaís Larissa do Amaral Montanheiro Beatriz Rossi Canuto de Menezes Raissa Monteiro Pereira Karla Faquine Rodrigues Renata Guimarães Ribas Diego Morais da Silva Gilmar Patrocínio Thim 《Ceramics International》2021,47(3):2999-3012
Studies related to biomaterials that stimulate the repair of living tissue have increased considerably, improving the quality of many people's lives that require surgery due to traumatic accidents, bone diseases, bone defects, and reconstructions. Among these biomaterials, bioceramics and bioactive glasses (BGs) have proved to be suitable for coating materials, cement, scaffolds, and nanoparticles, once they present good biocompatibility and degradability, able to generate osteoconduction on the surrounding tissue. However, the role of biomaterials in hard tissue engineering is not restricted to a structural replacement or for guiding tissue regeneration. Nowadays, it is expected that biomaterials develop a multifunctional role when implanted, orchestrating the process of tissue regeneration and providing to the body the capacity to heal itself. In this way, the incorporation of specific metal ions in bioceramics and BGs structure, including magnesium, silver, strontium, lithium, copper, iron, zinc, cobalt, and manganese are currently receiving enhanced interest as biomaterials for biomedical applications. When an ion is incorporated into the bioceramic structure, a new category of material is created, which has several unique properties that overcome the disadvantages of primitive material and favors its use in different biomedical applications. The doping can enhance handling properties, angiogenic and osteogenic performance, and antimicrobial activity. Therefore, this review aims to summarize the effect of selected metal ion dopants into bioceramics and silicate-based BGs in bone tissue engineering. Furthermore, new applications for doped bioceramics and BGs are highlighted, including cancer treatment and drug delivery. 相似文献
4.
5.
Quality enhancement of the abundant under‐valued crustacean,lobster krill (Munida spp.), during its chilled storage
下载免费PDF全文
![点击此处可从《International Journal of Food Science & Technology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Bibiana García‐Soto José M. Miranda Jorge Barros‐Velázquez Santiago P. Aubourg 《International Journal of Food Science & Technology》2015,50(3):708-716
Lobster krill (Munida genus) represents an under‐valued crustacean frequently caught on European fishing banks. In this work, its sensory, microbiological and biochemical qualities were evaluated during chilled storage. Additionally, the effects of a prestorage antimelanosic treatment consisting of soaking in sodium metabisulphite (SMB) solutions at two different concentrations (0.25% and 0.75%) were also studied. SMB prestorage treatment provided lobster specimens that still exhibited acceptable sensory quality after 10 days of storage, while control specimens were unacceptable at that time. SMB treatment also resulted in a significant (P < 0.05) inhibition of microbial growth, mainly of Enterobacteriaceae, psychrotrophes and proteolytic bacteria. Low lipid oxidation levels were observed for all batches; however, a significantly higher (P < 0.05) retention of polyunsaturated fatty acids was found in SMB‐treated lobster, especially in the 0.75% SMB batch. The results presented here open the way to the potential commercialisation of currently under‐utilised lobster krill as a chilled product. 相似文献
6.
7.
Cyclo 3 Fort is used in the treatment of chronic venous insufficiency. In this study, the effects of Cyclo 3 Fort, 2, 10 and 50 mg/kg, were studied in cheek pouch preparations from diabetic hamsters. The mean arteriolar diameter in animals receiving Cyclo 3 Fort, 10 and 50 mg/kg, was significantly greater than in control animals (p < 0.05), and the mean venule diameter was significantly lower in animals receiving the 50 mg/kg dose than in the control group. This suggests that Cyclo 3 Fort, 50 mg/kg/day, has a venotonic effect in diabetic animals. The venoarteriolar reflex was studied by measuring the internal diameter of arterioles during venular occlusion. The reflex was impaired in animals treated with either placebo or 2 mg/kg, but this was reversed by treatment with Cyclo 3 Fort, 10 and 50 mg/kg. 相似文献
8.
Several variations of cache-based checkpointing for rollback error recovery from transient errors in shared-memory multiprocessors have been recently developed. By modifying the cache replacement policy, these techniques use the inherent redundancy in the memory hierarchy to periodically checkpoint the computation state. Three schemes, different in the manner in which they avoid rollback propagation, are evaluated in this paper. By simulation with address traces from parallel applications running on an Encore Multimax shared-memory multiprocessor, we evaluate the performance effect of integrating the recovery schemes in the cache coherence protocol. Our results indicate that the cache-based schemes can provide checkpointing capability with low performance overhead, but with uncontrollable high variability in the checkpoint interval 相似文献
9.
10.
The acquisition of new skills over a life span is a remarkable human ability. This ability, however, is constrained by age of acquisition (AoA); that is, the age at which learning occurs significantly affects the outcome. This is most clearly reflected in domains such as language, music, and athletics. This article provides a perspective on the neural and computational mechanisms underlying AoA in language acquisition. The authors show how AoA modulates both monolingual lexical processing and bilingual language acquisition. They consider the conditions under which syntactic processing and semantic processing may be differentially sensitive to AoA effects in second-language acquisition. The authors conclude that AoA effects are pervasive and that the neural and computational mechanisms underlying learning and sensorimotor integration provide a general account of these effects. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献