全文获取类型
收费全文 | 433篇 |
免费 | 12篇 |
国内免费 | 1篇 |
专业分类
化学 | 284篇 |
晶体学 | 2篇 |
力学 | 11篇 |
数学 | 67篇 |
物理学 | 24篇 |
无线电 | 58篇 |
出版年
2022年 | 5篇 |
2021年 | 15篇 |
2020年 | 4篇 |
2019年 | 10篇 |
2018年 | 12篇 |
2017年 | 5篇 |
2016年 | 15篇 |
2015年 | 9篇 |
2014年 | 18篇 |
2013年 | 36篇 |
2012年 | 22篇 |
2011年 | 20篇 |
2010年 | 16篇 |
2009年 | 24篇 |
2008年 | 20篇 |
2007年 | 26篇 |
2006年 | 23篇 |
2005年 | 16篇 |
2004年 | 9篇 |
2003年 | 11篇 |
2002年 | 17篇 |
2001年 | 3篇 |
2000年 | 4篇 |
1999年 | 6篇 |
1998年 | 5篇 |
1997年 | 7篇 |
1996年 | 3篇 |
1995年 | 3篇 |
1994年 | 6篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1990年 | 3篇 |
1989年 | 6篇 |
1988年 | 2篇 |
1987年 | 6篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1983年 | 7篇 |
1982年 | 4篇 |
1981年 | 7篇 |
1980年 | 5篇 |
1979年 | 8篇 |
1978年 | 1篇 |
1976年 | 5篇 |
1975年 | 3篇 |
1973年 | 1篇 |
1971年 | 1篇 |
1969年 | 1篇 |
1928年 | 1篇 |
排序方式: 共有446条查询结果,搜索用时 14 毫秒
81.
In this paper we introduce the notion of module character amenable Banach algebras and show that they possess module character virtual (approximate) diagonals. As a basic example, we show that for an inverse semigroup S with the set of idempotents E, the semigroup algebra ? 1(S) is module character amenable as an ? 1(E)-module if only if S is amenable. 相似文献
82.
The glycomic profiling of purified glycoproteins and biological specimen is routinely achieved through different analytical methods, but mainly through MS and LC-MS. The enhanced ionization efficiency and improved tandem MS interpretation of permethylated glycans have prompted the popularity of this approach. This study focuses on comparing the glycomic profiling of permethylated N-glycans derived from model glycoproteins and human blood serum using MALDI-MS as well as RP-LC-MALDI-MS and RP-LC-ESI-MS. In the case of model glycoproteins, the glycomic profiles acquired using the three methods were very comparable. However, this was not completely true in the case of glycans derived from blood serum. RP-LC-ESI-MS analysis of reduced and permethylated N-glycans derived from 250 nl of blood serum allowed the confident detection of 73 glycans (the structures of which were confirmed by mass accuracy and tandem MS), while 53 and 43 structures were identified in the case of RP-LC-MALDI-MS and MALDI-MS analyses of the same sample, respectively. RP-LC-ESI-MS analysis facilitates automated and sensitive tandem MS acquisitions. The glycan structures that were detected only in the RP-LC-ESI-MS analysis were glycans existing at low abundances. This is suggesting the higher detection sensitivity of RP-LC-ESI-MS analysis, originating from both reduced competitive ionization and saturation of detectors, facilitated by the chromatographic separation. The latter also permitted the separation of several structural isomers; however, isomeric separations pertaining to linkages were not detected. 相似文献
83.
Nasser Nikfarjam Matineh Ghomi Tarun Agarwal Mahnaz Hassanpour Esmaeel Sharifi Danial Khorsandi Moonis Ali Khan Filippo Rossi Arianna Rossetti Ehsan Nazarzadeh Zare Navid Rabiee Davoud Afshar Massoud Vosough Tapas Kumar Maiti Virgilio Mattoli Eric Lichtfouse Franklin R. Tay Pooyan Makvandi 《Advanced functional materials》2021,31(42):2104148
Excessive and unwarranted administration of antibiotics has invigorated the evolution of multidrug-resistant microbes. There is, therefore, an urgent need for advanced active compounds. Ionic liquids with short-lived ion-pair structures are highly tunable and have diverse applications. Apart from their unique physicochemical features, the newly discovered biological activities of ionic liquids have fascinated biochemists, microbiologists, and medical scientists. In particular, their antimicrobial properties have opened new vistas in overcoming the current challenges associated with combating antibiotic-resistant pathogens. Discussions regarding ionic liquid derivatives in monomeric and polymeric forms with antimicrobial activities are presented here. The antimicrobial mechanism of ionic liquids and parameters that affect their antimicrobial activities, such as chain length, cation/anion type, cation density, and polymerization, are considered. The potential applications of ionic liquids in the biomedical arena, including regenerative medicine, biosensing, and drug/biomolecule delivery, are presented to stimulate the scientific community to further improve the antimicrobial efficacy of ionic liquids. 相似文献
84.
85.
Power Optimization in VLSI Layout: A Survey 总被引:1,自引:0,他引:1
This paper presents a survey of layout techniques for designing low power digital CMOS circuits. It describes the many issues facing designers at the physical level of design abstraction and reviews some of the techniques and tools that have been proposed to overcome these difficulties. 相似文献
86.
Walter Kaminsky Massoud Miri 《Journal of polymer science. Part A, Polymer chemistry》1985,23(8):2151-2164
EPDM terpolymers with ethylidene norbornene as diene monomer could be prepared by means of a soluble Ziegler catalyst formed from biscyclopentadienyl zirconium dimethyl and methylaluminoxane. The overall activities lie between 100 and 1000 kg EPDM/(molZr h bar), obtainable at zirconium concentrations as low as 5 × 10?7 mol/L. After an induction period (0.5–5 h) the polymerization rates increased and then leveled to a value which was constant for several days. From copolymerization kinetics reactivity ratios r12 = 31.5, r21 = 5 × 10?3, and r13 = 3.1 could be derived, and by 13C-NMR spectroscopy r12 · r21 = 0.3 was found (1: ethylene, 2: propylene and 3: ethylidene norbornene). The regiospecifity of the catalyst toward propylene leads exclusively to the formation of head-to-tail enchainments. The diene polymerizes via vinyl polymerization of the cyclic double bond, and the tendency to branching is low. Molecular weights were estimated between 40,000 and 160,000. The average molecular weight distribution of 1.7 is remarkably narrow. Glass transition temperatures of ?60 to ?50°C could be observed. The cure behavior and the physical properties of cured samples were also tested. 相似文献
87.
Abdullah S. Babaqi Mohamed T. Mohamed Salah S. Massoud Mohamed F. Amira 《Transition Metal Chemistry》1988,13(3):201-204
Summary The aquation of chloropentamminecobalt(III) ion has been studied in ethylene glycol-water mixtures up to 80% by weight at five temperatures from 35 to 55°C. Specific solvent effects on the reaction rate and mechanism have been investigated and discussed. The validity of our previously proposed equations, correlating the specific reaction rate with the dielectric constant of the medium has been examined. The thermodynamic parameters of activation have been calculated and presented as evidence for the solvation effects and in support of the proposed reaction mechanism. 相似文献
88.
S. Jha Sherif Yehia C. Mitros Amer Lahamer Glenn M. Julian R. A. Dunlap 《Hyperfine Interactions》1989,51(1-4):987-991
The time differential perturbed angular correlation method has been used to measure, as a function of temperature, the hyperfine
magnetic field at Cd sites in the Heusler alloys Co2MnZ (Z=Si, Ga, Ge, Sn). The hyperfine fields, normalized to the total magnetic moment per formula unit, show an approximately
linear trend toward more positive values with increasing lattice parameter. 相似文献
89.
The Markov-Bernoulli geometric distribution is obtained when a generalization, as a Markov process, of the independent Bernoulli sequence of random variables is introduced. In this paper, some characterizations of this distribution are obtained. The achieved results generalize the corresponding characterizations concerning the usual geometric distribution and its mixture. 相似文献
90.
Nosrat Mohammadizadeh Sayed Zia Mohammadi Massoud Kaykhaii 《Journal of Analytical Chemistry》2018,73(7):685-694
A novel carbon paste electrode modified with ZrO2 nanoparticles and an ionic liquid (n-hexyl-3- methylimidazolium hexafluorophosphate) was fabricated. The electrochemical study of the modified electrode, as well as its efficiency for simultaneous voltammetric oxidation of dopamine and uric acid is described. The electrode was also employed to study the electrochemical oxidation of dopamine and uric acid, using cyclic voltammetry, chronoamperometry and square wave voltammetry as diagnostic techniques. Square wave voltammetry exhibits linear dynamic range from 1.0 × 10?6 to 9.0 × 10?4 M for dopamine. Also, square wave voltammetry exhibits linear dynamic range from 9.0 × 10?6–1.0 × 10?3 M for uric acid. The modified electrode displayed strong function for resolving the overlapping voltammetric responses of dopamine and uric acid into two well-defined voltammetric peaks. In the mixture containing dopamine and uric acid, the two compounds can be well separated from each other with potential difference of 155 mV, which is large enough to determine dopamine and uric acid individually and simultaneously. Finally, the modified electrode was used for determination of dopamine and uric acid in real samples. 相似文献