全文获取类型
收费全文 | 398篇 |
免费 | 20篇 |
国内免费 | 3篇 |
专业分类
化学 | 151篇 |
晶体学 | 1篇 |
力学 | 21篇 |
数学 | 83篇 |
物理学 | 37篇 |
无线电 | 128篇 |
出版年
2024年 | 1篇 |
2022年 | 8篇 |
2021年 | 10篇 |
2020年 | 2篇 |
2019年 | 15篇 |
2018年 | 15篇 |
2017年 | 13篇 |
2016年 | 22篇 |
2015年 | 21篇 |
2014年 | 34篇 |
2013年 | 41篇 |
2012年 | 31篇 |
2011年 | 24篇 |
2010年 | 21篇 |
2009年 | 15篇 |
2008年 | 18篇 |
2007年 | 20篇 |
2006年 | 20篇 |
2005年 | 12篇 |
2004年 | 12篇 |
2003年 | 12篇 |
2002年 | 7篇 |
2001年 | 12篇 |
2000年 | 4篇 |
1999年 | 4篇 |
1996年 | 5篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1993年 | 5篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有421条查询结果,搜索用时 493 毫秒
11.
12.
13.
The perturbation of multiqubit systems by an external noise can induce various effects like decoherence, stochastic resonance and anti-resonance, and noise-shielding. We investigate how the appearance of these effects on disentanglement time depends on the initial preparation of the systems. We present results for 2-, 3- and 4-qubit chains in various arrangements and observe a clear dependence on the combination of initial geometry of the state space and the placement of noise. Finally, we see that temperature can play a constructive role for the control of these noise induced effects. 相似文献
14.
Bo Zhang Yufeng Wang Athanasios V. Vasilakos Jianhua Ma 《Telecommunication Systems》2013,54(1):91-110
Online social networks (OSNs) such as Facebook and MySpace, etc., greatly improve our social connectivity and collaboration. However, those applications lead to a shift from physical communities to virtual communities. The recent availability of mobile broadband connections and location technologies, their increasing affordability, and the usability of new mobile devices (e.g. smartphones) have led to the emergence of mobile social networks (MSNs), which re-connect the virtual community to the physical region, and move users between them in a way that enhances both. Currently, MSN applications are mushrooming and racing to replicate the success of social computing in the mobile domain. We argue that the potential success of MSNs lies in active collaboration among users, which naturally arises many interdisciplinary challenges. However, there exists no systematical survey about MSNs. This paper thoroughly characterizes the basic design principles, research architecture, typical techniques, and fundamental issues in MSNs from cross-discipline and application viewpoints. Our contributions lie in the following aspects: First, we summarized the basic design principles and fundamental issues that run through MSN researches and applications; then, from multidisciplinary viewpoint, the research architecture is divided into multi-dimensional structural characteristics and evolution of users’ rational behaviors. Finally, from application perspective, MSNs are categorized into two areas: Socially inspired mobile networking technologies, and enhanced real social life with mobile computing (people-centric tasks and place centric tasks). Briefly, this paper organizes the isolated topics and systems in existing work into meaningful categories, and structures the design space for identifying social-technical challenges, inspiring potentially interesting social networking applications, and suggesting important research opportunities. 相似文献
15.
16.
17.
A mathematical model is constructed and solved that could describe the dynamic behavior of the adsorption of a solute of interest in single and stratified columns packed with partially fractal porous adsorbent particles. The results show that a stratified column bed whose length is the same as that of a single column bed, provides larger breakthrough times and a higher dynamic utilization of the adsorptive capacity of the particles than those obtained from the single column bed, and the superior performance of the stratified bed becomes especially more important when the superficial velocity of the flowing fluid stream in the column is increased to accommodate increases in the system throughput. This occurs because the stratified column bed provides larger average external and intraparticle mass transfer and adsorption rates per unit length of packed column. It is also shown that increases in the total number of recursions of the fractal and the ratio of the radii between larger and smaller microspheres that make up the partially fractal particles, increase the intraparticle mass transfer and adsorption rates and lead to larger breakthrough times and dynamic utilization of the adsorptive capacity of the particles. The results of this work indicate that highly efficient adsorption separations could be realized through the use of a stratified column comprised from a practically reasonable number of sections packed with partially fractal porous adsorbent particles having reasonably large (i) total number of recursions of the fractal and (ii) ratio of the radii between larger and smaller microspheres from which the partially fractal particles are made from. It is important to mention here that the physical concepts and modeling approaches presented in this work could be, after a few modifications of the model, applied in studying the dynamic behavior of chemical catalysis and biocatalysis in reactor beds packed with partially fractal porous catalyst particles. 相似文献
18.
Theodoros Aggelopoulos Argyro Bekatorou Ashok Pandey Maria Kanellaki Athanasios A. Koutinas 《Applied biochemistry and biotechnology》2013,170(8):1885-1895
The exploitation of various agro-industrial wastes for microbial cell mass production of Kluyveromyces marxianus, kefir, and Saccharomyces cerevisiae is reported in the present investigation. Specifically, the promotional effect of whole orange pulp on cell growth in mixtures consisting of cheese whey, molasses, and potato pulp in submerged fermentation processes was examined. A 2- to 3-fold increase of cell mass was observed in the presence of orange pulp. Likewise, the promotional effect of brewer’s spent grains on cell growth in solid state fermentation of mixtures of whey, molasses, potato pulp, malt spent rootlets, and orange pulp was examined. The cell mass was increased by 3-fold for K. marxianus and 2-fold for S. cerevisiae in the presence of these substrates, proving their suitability for single-cell protein production without the need for extra nutrients. Cell growth kinetics were also studied by measurements of cell counts at various time intervals at different concentrations of added orange pulp. The protein content of the fermented substrates was increased substantially, indicating potential use of mixed agro-industrial wastes of negligible cost, as protein-enriched livestock feed, achieving at the same time creation of added value and waste minimization. 相似文献
19.
Evangelia Chronopoulou Panagiotis Madesis Athanasios Tsaftaris Nikolaos E. Labrou 《Applied biochemistry and biotechnology》2014,172(2):595-609
Glutathione transferases (GSTs, EC 2.5.1.18) are ubiquitous proteins in plants that play important roles in stress tolerance and in the detoxification of toxic chemicals and metabolites. In this study, we systematically examined the catalytic diversification of a GST isoenzyme from Phaseolus vulgaris (PvGST) which is induced under biotic stress treatment (Uromyces appendiculatus infection). The full-length cDNA of this GST isoenzyme (termed PvGSTU3-3) with complete open reading frame, was isolated using RACE-RT and showed that the deduced amino acid sequence shares high homology with the tau class plant GSTs. PvGSTU3-3 catalyzes several different reactions and exhibits wide substrate specificity. Of particular importance is the finding that the enzyme shows high antioxidant catalytic function and acts as hydroperoxidase, thioltransferase, and dehydroascorbate reductase. In addition, its K m for GSH is about five to ten times lower compared to other plant GSTs, suggesting that PvGSTU3-3 is able to perform efficient catalysis under conditions where the concentration of reduced glutathione is low (e.g., oxidative stress). Its ability to conjugate GSH with isothiocyanates may provide an additional role for this enzyme to act as a regulator of the released isothiocyanates from glucosinolates as a response of biotic stress. Molecular modeling showed that PvGSTU3-3 shares the same overall fold and structural organization with other plant cytosolic GSTs, with major differences at their hydrophobic binding sites (H-sites) and some differences at the level of C-terminal domain and the linker between the C- and N-terminal domains. PvGSTU3-3, in general, exhibits restricted ability to bind xenobiotics in a nonsubstrate manner, suggesting that the biological role of PvGSTU3-3, is restricted mainly to the catalytic function. Our findings highlight the functional and catalytic diversity of plant GSTs and demonstrate their pivotal role for addressing biotic stresses in Phaseolus vulgaris. 相似文献
20.
Theodosis Giousis Georgia Potsi Antonios Kouloumpis Konstantinos Spyrou Yiannis Georgantas Nikolaos Chalmpes Konstantinos Dimos Myrsini‐Kiriaki Antoniou Georgios Papavassiliou Athanasios B. Bourlinos Hae Jin Kim Vijay Kumar Shankarayya Wadi Saeed Alhassan Majid Ahmadi Bart J. Kooi Graeme Blake Daniel M. Balazs Maria A. Loi Dimitrios Gournis Petra Rudolf 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2021,133(1):364-369
Germanane (GeH), a germanium analogue of graphane, has recently attracted considerable interest because its remarkable combination of properties makes it an extremely suitable candidate to be used as 2D material for field effect devices, photovoltaics, and photocatalysis. Up to now, the synthesis of GeH has been conducted by substituting Ca by H in a β‐CaGe2 layered Zintl phase through topochemical deintercalation in aqueous HCl. This reaction is generally slow and takes place over 6 to 14 days. The new and facile protocol presented here allows to synthesize GeH at room temperature in a significantly shorter time (a few minutes), which renders this method highly attractive for technological applications. The GeH produced with this method is highly pure and has a band gap (Eg) close to 1.4 eV, a lower value than that reported for germanane synthesized using HCl, which is promising for incorporation of GeH in solar cells. 相似文献