首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   401篇
  免费   22篇
电工技术   13篇
综合类   1篇
化学工业   92篇
金属工艺   17篇
机械仪表   6篇
建筑科学   5篇
能源动力   16篇
轻工业   42篇
水利工程   2篇
石油天然气   4篇
无线电   45篇
一般工业技术   108篇
冶金工业   22篇
自动化技术   50篇
  2024年   2篇
  2023年   5篇
  2022年   16篇
  2021年   23篇
  2020年   14篇
  2019年   16篇
  2018年   23篇
  2017年   24篇
  2016年   22篇
  2015年   11篇
  2014年   16篇
  2013年   31篇
  2012年   17篇
  2011年   27篇
  2010年   21篇
  2009年   18篇
  2008年   15篇
  2007年   15篇
  2006年   8篇
  2005年   10篇
  2004年   10篇
  2003年   6篇
  2002年   4篇
  2001年   3篇
  2000年   3篇
  1999年   3篇
  1998年   6篇
  1997年   6篇
  1996年   3篇
  1995年   5篇
  1994年   4篇
  1993年   3篇
  1992年   1篇
  1991年   8篇
  1990年   1篇
  1988年   6篇
  1987年   3篇
  1986年   1篇
  1985年   1篇
  1983年   2篇
  1982年   3篇
  1981年   1篇
  1980年   1篇
  1978年   2篇
  1976年   1篇
  1975年   1篇
  1973年   1篇
排序方式: 共有423条查询结果,搜索用时 15 毫秒
1.
Wireless Personal Communications - In the fusion experiment, sensitive radio frequency signal diagnostic instruments need to be protected against high power stray radiation coming from the Electron...  相似文献   
2.
3.
Context and objective: The aim of this study was to develop, characterize and evaluate a mucoadhesive caplet resulting from a polymeric blend (polymeric caplet) for intravaginal anti-HIV-1 delivery.

Materials and methods: Poly(lactic-co-glycolic) acid, ethylcellulose, poly(vinylalcohol), polyacrylic acid and modified polyamide 6, 10 polymers were blended and compressed to a caplet-shaped device, with and without two model drugs 3′-azido-3′-deoxythymidine (AZT) and polystyrene sulfonate (PSS). Thermal analysis, infrared spectroscopy and microscopic analysis were carried out on the caplets employing temperature-modulated DSC (TMDSC), Fourier transform infra-red (FTIR) spectrometer and scanning electron microscope, respectively. In vitro and in vivo drug release analyses as well as the histopathological toxicity studies were carried out on the drug-loaded caplets. Furthermore, molecular mechanics (MM) simulations were carried out on the drug-loaded caplets to corroborate the experimental findings.

Results and discussion: There was a big deviation between the Tg of the polymeric caplet from the Tg's of the constituent polymers indicating a strong interaction between constituent polymers. FTIR spectroscopy confirmed the presence of specific ionic and non-ionic interactions within the caplet. A controlled near zero-order drug release was obtained for AZT (20 d) and PSS (28 d). In vivo results, i.e. the drug concentration in plasma ranged between 0.012–0.332?mg/mL and 0.009–0.256?mg/mL for AZT and PSS over 1–28 d.

Conclusion: The obtained results, which were corroborated by MM simulations, attested that the developed system has the potential for effective delivery of anti-HIV-agents.  相似文献   
4.
5.
The high expectations and demand for users to access the Internet from anywhere at anytime has made user mobility an important part of the design and development of the next generation mobile communications and computing. Traditionally user mobility has been divided into two areas: Terminal Mobility and Personal Mobility. In recent years terminal mobility has focused on the movement of the terminal and developed extensions to IP protocols such as Mobile IP. In contrast, personal mobility has only received limited attention, and is somewhat lagging behind. This research has either focussed on personal mobility in communications or personalisation of operating environments. As a result, to date no framework for providing true personal mobility has emerged. In this paper, we introduce a new personal mobility framework called IPMoA (Integrated Personal Mobility Architecture), which integrates both aspects of personal mobility to provide a complete personal mobility solution, and illustrate the viability of this approach through a proof-of-concept implementation.  相似文献   
6.
The clinical fertility tests, available in the market, fail to define the exact cause of male infertility in almost half of the cases and point toward a crucial need of developing better ways of infertility investigations. The protein biomarkers may help us toward better understanding of unknown cases of male infertility that, in turn, can guide us to find better therapeutic solutions. Many clinical attempts have been made to identify biomarkers of male infertility in sperm proteome but only few studies have targeted seminal plasma. Human seminal plasma is a rich source of proteins that are essentially required for development of sperm and successful fertilization. This viewpoint article highlights the importance of human seminal plasma proteome in reproductive physiology and suggests that differential proteomics integrated with functional analysis may help us in searching potential biomarkers of male infertility.  相似文献   
7.
Intermetallic phases in Al-Mn alloys   总被引:3,自引:0,他引:3  
The intermetallic phases present in high-purity and commercial purity Al-Mn alloys (up to 2% Mn) in as-cast and heat-treated conditions were extracted electrolytically in 10% HCl in methanol solution and identified by X-ray diffraction. As iron is known to increase the coarse cast-intermetallic particles and to cause refinement of the grain size after recrystallization, different amounts of iron (up to 0.5%) were added and the resulting intermetallic phases were extracted and identified with and without heat treatment. The unidentified phase -Al (Mn, Fe)Si, reported by Sperry and others, was recognized as corresponding for ASTM card number 6-0669 and the conditions favourable for its formation were determined. This phase may be responsible for refining the grain size after recrystallization in commercial purity alloys as compared to high-purity Al-Mn alloys and may therefore be tried as an inoculant (by adding powdered compound to liquid alloys) for grain refining.  相似文献   
8.
Evolutionarily elderly proteins commonly feature greater catalytic promiscuity. Cytochrome c is among the first set of proteins in evolution to have known prospects in electron transport and peroxidative properties. Here, we report that cyt c is also a proficient proton-transfer catalyst and enhances the Kemp elimination (KE; model reaction to show proton transfer catalytic property) by ∼750-fold on self-organized systems like micelles and vesicles. The self-organized systems mimic the mitochondrial environment in vitro for cyt c. Using an array of biophysical and biochemical mutational assays, both acid–base and redox mechanistic pathways have been explored. The histidine moiety close to hemin group (His18) is mainly responsible for proton abstraction to promote the concerted E2 pathway for KE catalysis when cyt c is in its oxidized form; this has also been confirmed by a H18A mutant of cyt c. However, the redox pathway is predominant under reducing conditions in the presence of dithiothreitol over the pH range 6–7.4. Interestingly, we found almost 750-fold enhanced KE catalysis by cyt c compared to aqueous buffer. Overall, in addition to providing mechanistic insights, the data reveal an unprecedented catalytic property of cyt c that could be of high importance in an evolutionary perspective considering its role in delineating the phylogenic tree and also towards generating programmable designer biocatalysts.  相似文献   
9.
高吸水聚合物材料在防沙治沙中的应用   总被引:2,自引:0,他引:2  
介绍了高吸水聚合物的发展状况、吸水机理和性能特征,总结了合成高吸水聚合物及半合成高吸水聚合物的技术条件及若干种制备方法,并提出利用低成本植物纤维素(取自植物落叶、农作物茎杆等)、淀粉等天然原材料来制备高吸水性聚合物;探讨了以高技术、低成本、大面积可实施及效果显著为技术优势,利用高吸水聚合物进行荒漠和沙漠治理的方法和发展方向。  相似文献   
10.
In Fifth Generation (5G) Heterogeneous Mobile Networks (HetNets), deploying dense small cell networks makes user association more challenging. The process of collecting cell load information from the User Equipments (UEs) and broadcasting the feedback message involves significant overhead and time complexity. Moreover, the UEs may not know the optimum cell to reselect, satisfying its data rate requirements. In order to overcome these drawbacks, in this paper, we propose to design an Hierarchical and Hybrid Cell Load Balancing (HHCLB) technique using Selective Handoff. In this technique, the UEs of each cell are grouped into clusters depending on their proximity distance. Each cluster contains a cluster controller (CC) which is in charge of determining the intra-cell load and redirecting the cell-reselection request of a UE. If the data rate of any UE in a cluster becomes less than its required rate, then the cell reselection process is performed. By simulation results, it is shown that load balancing can be done proactively (implicitly) by the CCs when the load is unbalanced or can be done on demand (explicitly) when a UE send a request for cell reselection. In the case of Macro cells, HHCLB attains 71% higher throughput for low load scenario and 59% higher throughput for high load scenario. Similarly, in the case of Femto cells, HHCLB attains 19% higher throughput for low load scenario and 27% higher throughput for high load scenario.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号