全文获取类型
收费全文 | 1398篇 |
免费 | 49篇 |
国内免费 | 5篇 |
专业分类
化学 | 912篇 |
晶体学 | 16篇 |
力学 | 36篇 |
数学 | 182篇 |
物理学 | 306篇 |
出版年
2023年 | 36篇 |
2022年 | 42篇 |
2021年 | 49篇 |
2020年 | 43篇 |
2019年 | 42篇 |
2018年 | 41篇 |
2017年 | 20篇 |
2016年 | 44篇 |
2015年 | 45篇 |
2014年 | 42篇 |
2013年 | 74篇 |
2012年 | 73篇 |
2011年 | 116篇 |
2010年 | 44篇 |
2009年 | 53篇 |
2008年 | 73篇 |
2007年 | 67篇 |
2006年 | 56篇 |
2005年 | 45篇 |
2004年 | 48篇 |
2003年 | 26篇 |
2002年 | 27篇 |
2001年 | 17篇 |
2000年 | 19篇 |
1999年 | 9篇 |
1998年 | 9篇 |
1997年 | 16篇 |
1996年 | 13篇 |
1995年 | 8篇 |
1994年 | 9篇 |
1993年 | 20篇 |
1992年 | 6篇 |
1991年 | 13篇 |
1990年 | 10篇 |
1989年 | 5篇 |
1988年 | 10篇 |
1987年 | 12篇 |
1986年 | 8篇 |
1985年 | 9篇 |
1984年 | 14篇 |
1983年 | 9篇 |
1982年 | 9篇 |
1981年 | 9篇 |
1980年 | 8篇 |
1979年 | 9篇 |
1978年 | 11篇 |
1977年 | 8篇 |
1976年 | 8篇 |
1974年 | 5篇 |
1973年 | 6篇 |
排序方式: 共有1452条查询结果,搜索用时 15 毫秒
101.
Ftima C. Teixeira Carla Lucas M. Joo M. Curto Antnio P. S. Teixeira M. Teresa Duarte Vnia Andr 《Heteroatom Chemistry》2016,27(1):3-11
Novel tetraethyl ethylene‐1,1‐bisphosphonate esters derived from 1H‐indazole, 1H‐pyrazolo[3,4‐b]pyridine, and 1H‐pyrazolo[3,4‐b]quinoline were synthesized by a Michael addition reaction of tetraethyl ethylidene‐1,1‐bisphosphonate with the corresponding heterocycle, using conventional heating and microwave‐assisted methods. The microwave‐assisted method provides shorter reaction times and better yields. The hydrolysis of bisphosphonates afforded the corresponding bisphosphonic acids or salt, using concentrated hydrochloric acid or TMSBr/collidine, respectively. All new compounds were fully characterized, and their structures were assigned using 1H, 31P, and 13C NMR and IR spectroscopies and mass spectrometry. The molecular structure of compound 6 was confirmed by X‐ray diffraction studies. 相似文献
102.
Validation of Sun Exposure Reported Annually Against Interim Self‐report and Daily Sun Diaries 下载免费PDF全文
Laura King Fan Xiang Ashwin Swaminathan Keith Dear Simone L. Harrison Ingrid van der Mei Michael G. Kimlin Catherine D'Este Robyn M. Lucas 《Photochemistry and photobiology》2017,93(5):1294-1302
Data on personal sun exposure over a period exceeding the immediate past days or weeks are typically self‐reported in brief questionnaire items. The validity of such self‐reporting of longer term personal sun exposure, for example over a year, including detail on variation across seasons, has not previously been investigated. In a volunteer sample (n = 331) of Australian adults aged 18 years and over, we assessed the 12‐month reliability of sun exposure reported separately for each season, and its accuracy compared to a daily sun diary in the same season. Seasonal time outdoors displayed fair‐to‐good reliability between baseline and end of study (12 months), with responses showing higher agreement at lower levels of time outdoors. There was good agreement for ranking of individuals' time outdoors with the daily sun diary data, although the actual diary time outdoors was typically considerably lower than the self‐reported questionnaire data. Place of residence, education, being a smoker, day of the week (i.e. working day vs nonworking day) and working mainly outdoors were significant predictors of agreement. While participants overestimated their actual time outdoors, the self‐report questionnaire provided a valid ranking of long‐term sun exposure against others in the study that was reliable over time. 相似文献
103.
We report the development of a general order relativistic coupled-cluster (CC) code. Our implementation is based on Kramers-paired molecular spinors, utilizes double group symmetry, and is applicable with the full Dirac-Coulomb and several approximate relativistic Hamiltonians. The available methods include iterative and perturbative single-reference CC approaches with arbitrary excitations as well as a state-selective multi-reference CC ansatz. To illustrate the performance of the new code, benchmark calculations have been performed for the total energies, bond lengths, and vibrational frequencies of the monoxides of Group IVa elements. The trends due to the simultaneous inclusion of relativity as well as higher-order electron correlation effects are analyzed. The newly developed code significantly widens the scope of the ab initio relativistic calculations, for both molecules and atoms alike, surpassing the accuracy and reliability of the currently available implementations in the literature. 相似文献
104.
José F. Cariñena Javier de Lucas Manuel F. Rañada 《International Journal of Theoretical Physics》2011,50(7):2114-2124
A geometric approach is used to study the Abel first-order differential equation of the first kind. The approach is based
on the recently developed theory of quasi-Lie systems which allows us to characterise some particular examples of integrable
Abel equations. Second order Abel equations will be discussed and the inverse problem of the Lagrangian dynamics is analysed:
the existence of two alternative Lagrangian formulations is proved, both Lagrangians being of a non-natural class. The study
is carried out by means of the Darboux polynomials and Jacobi multipliers. 相似文献
105.
Systems consisting of identical bosons with a large scattering length satisfy universal relations determined by 2-body physics that are similar to those for fermions with two spin states. They require the momentum distribution to have a large-momentum 1/k(4) tail and the radio-frequency transition rate to have a high-frequency 1/ω(3/2) tail, both of which are proportional to the 2-body contact. Identical bosons also satisfy additional universal relations that are determined by 3-body physics and involve the 3-body contact, which measures the probability of 3 particles being very close together. The coefficients of the 3-body contact in the 1/k(5) tail of the momentum distribution and in the 1/ω(2) tail of the radio-frequency transition rate are log-periodic functions of k and ω that depend on the Efimov parameter. 相似文献
106.
Bernard Masereel Mustapha Dinguizli Caroline Bouzin Nicolas Moniotte Olivier Feron Bernard Gallez Thierry Vander Borght Carine Michiels Stéphane Lucas 《Journal of nanoparticle research》2011,13(4):1573-1580
Nanoscale materials are used in the biomedical field for magnetic resonance imaging, protein detection and drug/gene delivery.
Gold nanoparticles (AuNPs) are particularly investigated in cancer treatment and imaging. In this study, we described a simple
and reliable liquid method to coat AuNPs (diameter: 21 nm) layer-by-layer with alternative cationic polyallylamine and anionic
polystyrenesulfonate. The C-terminal amino acid of the antibody directed against anti-bovine serum albumin was activated by
EDC/NHS, and then condensed with the amino functions of the external polyallylamine layer. An ELISA test confirmed that the
antigen recognition of the bioconjugate antibody was conserved. This AuNP coating and the covalently coupling could be used
as a generic process for binding other specific antibodies, particularly those overexpressed in cancer cells and angiogenesis. 相似文献
107.
We are concerned with a family of dissipative active scalar equation with velocity fields coupled via multiplier operators that can be of positive-order. We consider sub-critical values for the fractional diffusion and prove global well-posedness of solutions with small initial data belonging to a framework based on Fourier transform, namely Fourier–Besov–Morrey spaces. Since the smallness condition is with respect to the weak norm of this space, some initial data with large \(L^{2}\) -norm can be considered. Self-similar solutions are obtained depending on the homogeneity of the initial data and couplings. Also, we show that solutions are asymptotically self-similar at infinity. Our results can be applied in a unified way for a number of active scalar PDEs like 1D models on dislocation dynamics in crystals, Burgers’ equation, 2D vorticity equation, 2D generalized SQG, 3D magneto-geostrophic equations, among others. 相似文献
108.
C. Fitzpatrick E. Lewis A. Al-Shamma’a I. Pandithas J. Cullen J. Lucas 《Optical Review》2001,8(6):459-462
Low-pressure mercury lamps are commonly used for germicidal applications such as water and wastewater sterilisation. The germicidal
effect is due to the emission of light at 254 nm, which leads to the destruction of most waterborne bacteria. The Microwave
plasma ultraviolet lamp (MPUVL) is a new technology for generating a high intensity ultraviolet (UV) light. A Fluorescent
optical fiber based sensor is presented which is used for monitoring the output of a high power microwave UV light source
and its control. This sensor is a fiber which has had its cladding removed and been coated with a phosphor doped polymer.
This paper was originally presented at the 2001 International Conference (2nd Joint OSJ-SPIE Conference) on Optical Engineering
for Sensing and Nanotechnology, ICOSN 2001 which was held June 6–8, 2001 at the Pacifico-Yokohama Conference Center, Yokohama,
Japan. 相似文献
109.
110.
Herman S. Mansur Rodrigo L. Oréfice Zélia P. Lobato Wander L. Vasconcelos Eliane S. Mansur Lucas J. C. Machado 《Adsorption》2001,7(2):105-116
Adsorption/desorption of proteins onto a biomaterial surface plays a major role on the biocompatibility of the implanted material. By modifying the biomaterial surface with specially designed functional groups one may achieve the most specific behavior of the developed material used in a biological system. Based on that, porous gel matrixes with functionalized surfaces offer unlimited possibilities to control the protein-substrate interaction behavior. In the present work, we have functionalized the surface of porous glass with several chemical groups during the synthesis of the silica matrix. The porous glass matrixes were obtained using tetraethoxysilane (TEOS)/ethanol and functionalized with 3-mercaptopropyltrimethoxysilane (MPTMS) and 3-aminopropyltriethoxysilane (APTES). In vitro tests of the kinetics of protein adsorption and desorption from the gel matrix were monitored by UV-visible spectroscopy. The bioactivity of the incorporated protein was verified by in vivo experiments with adult male rats, where they presented an acute hypoglycemic peak. 相似文献