全文获取类型
收费全文 | 373篇 |
免费 | 12篇 |
专业分类
化学 | 203篇 |
晶体学 | 1篇 |
力学 | 2篇 |
数学 | 60篇 |
物理学 | 119篇 |
出版年
2022年 | 2篇 |
2021年 | 11篇 |
2020年 | 6篇 |
2019年 | 11篇 |
2018年 | 23篇 |
2017年 | 18篇 |
2016年 | 16篇 |
2015年 | 7篇 |
2014年 | 14篇 |
2013年 | 19篇 |
2012年 | 27篇 |
2011年 | 26篇 |
2010年 | 16篇 |
2009年 | 13篇 |
2008年 | 5篇 |
2007年 | 11篇 |
2006年 | 7篇 |
2005年 | 7篇 |
2004年 | 5篇 |
2003年 | 4篇 |
2002年 | 4篇 |
2001年 | 4篇 |
2000年 | 2篇 |
1999年 | 3篇 |
1998年 | 5篇 |
1997年 | 3篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 4篇 |
1989年 | 3篇 |
1986年 | 4篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1978年 | 2篇 |
1970年 | 2篇 |
1969年 | 4篇 |
1960年 | 3篇 |
1959年 | 10篇 |
1958年 | 17篇 |
1957年 | 4篇 |
1956年 | 5篇 |
1955年 | 9篇 |
1954年 | 5篇 |
1934年 | 2篇 |
1932年 | 3篇 |
1931年 | 3篇 |
排序方式: 共有385条查询结果,搜索用时 0 毫秒
121.
Dragan M. Milenović Snežana P. Milošević Svetlana Lj. Đurić Daniela Č. Nasković Snežana S. Mitić 《Journal of Analytical Chemistry》2013,68(6):545-551
Analytical method validation, determining the recovery rate from the equipment surface, and stability of a potential contaminant are important steps of a cleaning validation process. An HPLC method for the determination of the verapamil residues on stainless steel surfaces of the equipment employed in drug manufacture is described. The cleaning validation sample impurities as well as excipients of the commercial sample did not interfere in the analysis which proved the selectivity of the method. The validation of the method demonstrated acceptable levels of the linearity, precision and accuracy. Cotton swabs, moistened with methanol were used to remove any residues of drugs from stainless steel surfaces, and give recoveries of above 78.59% for three diferent concentration levels. The precision of the results, reported as the relative standard deviation (RSD, %), were below 1.58%. Low quantities of the drug residues were determined by HPLC using a Hypersil ODS column (125 × 4.0 mm, 5 μm) at 25°C with the mobile phase metanol-water-triethylamine (70: 30: 0.2, v/v/v) at a flow rate of 0.6 mL/min, injection volume of 50 μL and detection at 278 nm. 相似文献
122.
Miroslav Dvořák Martin Michl Numan Almonasy Miloš Nepraš Nemiah Ladd Vlastimil Fidler 《Journal of fluorescence》2011,21(3):971-974
Fluorescence anisotropy measurements were performed on a set of multichromophoric compounds, which contain a different number
of aminopyrenyl moieties linked to a triazine ring, in order to reveal the nature of both the electronic excited states and
relaxation pathways of the compounds. Our experimental results complement quantum chemical calculations. We propose that the
lowest excited state from which fluorescence proceeds is localized on a single individual aminopyrene moiety. In contrast,
excitation to a higher excited state is likely followed by a migration of energy to another nearby aminopyrene chromophore
before the internal conversion to the emitting state takes place. We suggest that this migration is responsible for the experimentally
measured decrease of fluorescence anisotropy of the studied compounds. 相似文献
123.
Milica Milošević Marija Radoičić Zoran Šaponjić Tim Nunney Christopher Deeks Vesna Lazić Miodrag Mitrić Tamara Radetić Maja Radetić 《Cellulose (London, England)》2014,21(5):3781-3795
The possibility of in situ photoreduction of Ag+-ions using TiO2 nanoparticles deposited on cotton and cotton/PET fabrics in the presence of amino acid alanine and methyl alcohol has been discussed. The possible interaction between TiO2, alanine and Ag+-ions was evaluated by FTIR analysis. The fabrication of TiO2/Ag nanoparticles on both fabrics was confirmed by SEM, EDX, XRD, XPS and AAS analyses. Cotton and cotton/PET fabrics impregnated with TiO2/Ag nanoparticles provided maximum reduction of Gram-negative bacteria Escherichia coli and Gram-positive bacteria Staphylococcus aureus. Although excellent antibacterial activity was preserved after ten washing cycles, a significant amount of silver leached out from the fabrics into the washing bath. The perspiration fastness assessment revealed that smaller amounts of silver were also released from the fabrics into artificial sweat at pH 5.50 and 8.00. In addition, deposited TiO2/Ag nanoparticles imparted maximum UV protection to fabrics. 相似文献
124.
Noelia Rubio Heather Au Gabriel O. Coulter Laure Guetaz Gerard Gebel Cecilia Mattevi Milo S. P. Shaffer 《Chemical science》2021,12(44):14907
Here, the locus of functionalisation on graphene-related materials and the progress of the reaction is shown to depend strongly on the starting feedstock. Five characteristically different graphite sources were exfoliated and functionalized using a non-destructive chemical reduction method. These archetypical examples were compared via a model reaction, grafting dodecyl addends, evaluated with TGA-MS, XPS and Raman data. A general increase in grafting ratio (ranging from 1.1 wt% up to 25 wt%) and an improvement in grafting stoichiometry (C/R) were observed as flake radius decreased. Raman spectrum imaging of the functionalised natural flake graphite identified that grafting is directed towards flake edges. This behaviour was further corroborated, at atomistic resolution, by functionalising the graphene layers with bipyridine groups able to complex single platinum atoms. The distribution of these groups was then directly imaged using aberration-corrected HAADF-STEM. Platinum atoms were found to be homogeneously distributed across smaller graphenes; in contrast, a more heterogeneous distribution, with a predominance of edge grafting was observed for larger graphites. These observations show that grafting is directed towards flake edges, but not necessary at edge sites; the mechanism is attributed to the relative inaccessibility of the inner basal plane to reactive moieties, resulting in kinetically driven grafting nearer flake edges. This phenomenology may be relevant to a wide range of reactions on graphenes and other 2d materials. The flake size and morphology of the starting material strongly effect the degree and location of grafting when using reductive functionalisation. 相似文献
125.
John T. Shaw James E. Babin Lori A. Sensenig Guy F. Acciai Mark C. Fair Timothy W. Coffindaffer W. Milo Westler 《Journal of heterocyclic chemistry》1985,22(2):255-256
The synthesis of the titled compound is described using 5-(2-carboxyanilino)-2-methyl-1,3-4,6,9b-pentaaza-phenalene as starting material. 相似文献
126.
M. Damnjanović T. Vuković I. Milošević 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,25(2):131-134
The friction between the walls of multi-wall carbon nanotubes is shown to be extremely low in general, with important details
related to the specific choice of the walls. This is governed by a simple expression revealing that the phenomenon is a profound
consequence of the specific symmetry breaking: super-slippery sliding of the incommensurate walls is a Goldstone mode. Three
universal principles of tribology, offering a recipe for lubricant selection are emphasized.
Received 8 August 2001 相似文献
127.
We demonstrate explicitly that the impure one-dimensional n-vector model with bilinear and biquadratic exchange interactions can be solved exactly. Results are provided for the free energy, equal-time spin-spin correlation functions and the initial susceptibility of the corresponding bond and site model in the annealed and quenched limit. A numerical analysis of the thermodynamic response functions in the n = 3 case is performed, and therein some interesting consequences of the simultaneous influence of the biquadratic interactions and impurities are established. The presence of the biquadratic interaction is interpreted as an effect of the lattice compressibility. 相似文献
128.
129.
Vladimir A. Andreev Dragomir M. Davidović Ljubica D. Davidović Milena D. Davidović Miloš D. Davidović Sergey D. Zotov 《Journal of Russian Laser Research》2016,37(5):434-439
We consider the Husimi Q(q, p)-functions which are quantum quasiprobability distributions on the phase space. It is known that, under a scaling transform (q; p) → (?q; ?p), the Husimi function of any physical state is converted into a function which is also the Husimi function of some physical state. More precisely, it has been proved that, if Q(q, p) is the Husimi function, the function ?2 Q(?q; ?p) is also the Husimi function. We call a state with the Husimi function ?2 Q(?q; ?p) the stretched state and investigate the properties of the stretched Fock states. These states can be obtained as a result of applying the scaling transform to the Fock states of the harmonic oscillator. The harmonic-oscillator Fock states are pure states, but the stretched Fock states are mixed states. We find the density matrices of stretched Fock states in an explicit form. Their structure can be described with the help of negative binomial distributions. We present the graphs of distributions of negative binomial coefficients for different stretched Fock states and show the von Neumann entropy of the simplest stretched Fock state. 相似文献
130.