全文获取类型
收费全文 | 667篇 |
免费 | 22篇 |
国内免费 | 2篇 |
专业分类
化学 | 358篇 |
晶体学 | 9篇 |
力学 | 36篇 |
数学 | 115篇 |
物理学 | 173篇 |
出版年
2023年 | 7篇 |
2022年 | 10篇 |
2021年 | 16篇 |
2020年 | 14篇 |
2019年 | 15篇 |
2018年 | 10篇 |
2017年 | 14篇 |
2016年 | 19篇 |
2015年 | 20篇 |
2014年 | 12篇 |
2013年 | 41篇 |
2012年 | 39篇 |
2011年 | 47篇 |
2010年 | 36篇 |
2009年 | 23篇 |
2008年 | 29篇 |
2007年 | 34篇 |
2006年 | 32篇 |
2005年 | 32篇 |
2004年 | 19篇 |
2003年 | 24篇 |
2002年 | 23篇 |
2001年 | 8篇 |
2000年 | 3篇 |
1999年 | 7篇 |
1998年 | 7篇 |
1997年 | 6篇 |
1996年 | 10篇 |
1995年 | 6篇 |
1994年 | 8篇 |
1993年 | 11篇 |
1992年 | 15篇 |
1991年 | 4篇 |
1990年 | 12篇 |
1989年 | 6篇 |
1988年 | 10篇 |
1987年 | 5篇 |
1986年 | 7篇 |
1985年 | 4篇 |
1984年 | 4篇 |
1983年 | 5篇 |
1982年 | 7篇 |
1981年 | 6篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1976年 | 2篇 |
1975年 | 3篇 |
1974年 | 4篇 |
1922年 | 1篇 |
排序方式: 共有691条查询结果,搜索用时 171 毫秒
51.
Low-power laser irradiation improves histomorphometrical parameters and bone matrix organization during tibia wound healing in rats 总被引:7,自引:0,他引:7
Garavello-Freitas I Baranauskas V Joazeiro PP Padovani CR Dal Pai-Silva M da Cruz-Höfling MA 《Journal of photochemistry and photobiology. B, Biology》2003,70(2):81-89
The influence of daily energy doses of 0.03, 0.3 and 0.9 J of He-Ne laser irradiation on the repair of surgically produced tibia damage was investigated in Wistar rats. Laser treatment was initiated 24 h after the trauma and continued daily for 7 or 14 days in two groups of nine rats (n=3 per laser dose and period). Two control groups (n=9 each) with injured tibiae were used. The course of healing was monitored using morphometrical analysis of the trabecular area. The organization of collagen fibers in the bone matrix and the histology of the tissue were evaluated using Picrosirius-polarization method and Masson's trichrome. After 7 days, there was a significant increase in the area of neoformed trabeculae in tibiae irradiated with 0.3 and 0.9 J compared to the controls. At a daily dose of 0.9 J (15 min of irradiation per day) the 7-day group showed a significant increase in trabecular bone growth compared to the 14-day group. However, the laser irradiation at the daily dose of 0.3 J produced no significant decrease in the trabecular area of the 14-day group compared to the 7-day group, but there was significant increase in the trabecular area of the 15-day controls compared to the 8-day controls. Irradiation increased the number of hypertrophic osteoclasts compared to non-irradiated injured tibiae (controls) on days 8 and 15. The Picrosirius-polarization method revealed bands of parallel collagen fibers (parallel-fibered bone) at the repair site of 14-day-irradiated tibiae, regardless of the dose. This organization improved when compared to 7-day-irradiated tibiae and control tibiae. These results show that low-level laser therapy stimulated the growth of the trabecular area and the concomitant invasion of osteoclasts during the first week, and hastened the organization of matrix collagen (parallel alignment of the fibers) in a second phase not seen in control, non-irradiated tibiae at the same period. The active osteoclasts that invaded the regenerating site were probably responsible for the decrease in trabecular area by the fourteenth day of irradiation. 相似文献
52.
We report the first example of a molecular switch of multifunctional dipolar ruthenium(III/II) pentaammine-N-methyl-(4,4'-bipyridinium) complexes, exclusively driven by light. This is achieved by using a two-phase (water/benzene) system in which RuIII/II complexes are soluble only in the water phase. The reversible redox switching is triggered by the selective irradiation of the water and the benzene compartments with 254 and 528 nm light, respectively. 相似文献
53.
P. Moskal H.-H. Adam A. Budzanowski R. Czyzykiewicz D. Grzonka M. Janusz L. Jarczyk B. Kamys A. Khoukaz K. Kilian P. Kowina T. Lister W. Oelert T. Rozek R. Santo G. Schepers T. Sefzick M. Siemaszko J. Smyrski S. Steltenkamp A. Strzalkowski P. Winter M. Wolke P. Wüstner W. Zipper 《The European Physical Journal A - Hadrons and Nuclei》2003,18(2-3):335-338
The production of
- and
-mesons in elementary nucleon-nucleon collisions has been investigated at the synchrotrons CELSIUS, COSY and SATURNE. The high-quality proton beam with low emittance and small momentum spread permits to study the creation of these mesons very close to the kinematical threshold, where --due to the rapid growth of the phase space volume-- the total cross-section increases by orders of magnitude over a few MeV range of the excess energy. The magnitude and energy dependence of the total cross-section as well as the occupation distribution of the phase space serve as observables for investigating the mechanisms underlying the production processes and the interaction of mesons with nucleons. The precise data on the
and
creation via the
reactions allowed to settle the general features of the
- and
-meson production and revealed the sensitivity of the mentioned observables to the nucleon-nucleon-meson final-state interaction. The particular production properties, like for example, the determination of the dominating exchange processes which lead to the excitation of the S
11 nucleon isobar in the case of
creation, must be established by confrontation with other observables. The present status of this investigation with an emphasis on the results of the COSY-11 Collaboration is briefly presented. The available data are interpreted in view of the production mechanism and the meson-nucleon interaction.Received: 30 September 2002, Published online: 22 October 2003PACS:
13.60.Le Meson production - 13.75.-n Hadron-induced low- and intermediate-energy reactions and scattering (energy
GeV) - 13.85.Lg Total cross sections - 25.40.-h Nucleon-induced reactions 相似文献
54.
We compute the -limit of a sequence obstacle functionals in the case of periodic obstacles. 相似文献
55.
Kevin Dal Pont Jean‐François Gérard Eliane Espuche 《Journal of Polymer Science.Polymer Physics》2013,51(13):1051-1059
In this work, a novel nanocomposite series based on styrene‐butadiene rubber (SBR latex) and alpha‐zirconium phosphate(α‐ZrP) lamellar nanofillers is successfully prepared. The α‐ZrP lamellar filler is modified at the cation exchange capacity by γ‐aminopropyltrimethoxysilane and the filler surface modification is first discussed. A significant improvement of the mechanical properties is obtained by using the surface modified nanofillers. However, no modification of the gas barrier properties is observed. The impact of addition of bis(triethoxysilylpropyl)tetrasulfide (TESPT) as coupling agent in the system is discussed on the nanofiller dispersion state and on the filler–matrix interfacial bonding. Simultaneous use of modified nanofillers and TESPT coupling agent is found out with extraordinary reinforcing effects on both mechanical and gas barrier properties and the key factors at the origin of the improvement of these properties are identified. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013 , 51, 1051–1059 相似文献
56.
Christophe Dal Zotto Araceli Zarate-Ruiz David Virieux Vincent Terrasson Anne Gaucher 《Journal of organometallic chemistry》2011,696(1):296-304
A direct intermolecular addition of nitrogen and 1,3-dicarbonyl nucleophiles to stabilized double bonds (styrenes, 1,3-dienes, enol-ethers, sugars.) in the presence of green and inexpensive FeCl3 catalyst is described. 相似文献
57.
Giuseppe Bruno Archimede Rotondo Giuseppe Tresoldi Francesco Nicol Santo Lanza 《Acta Crystallographica. Section C, Structural Chemistry》2005,61(4):m169-m172
The crystal structure of the title compound, [Ru(C10H8N2S)2(C11H11N3S)](PF6)2·C2H3N, is composed of a bivalent octahedral RuII complex, two PF6− anions and an acetonitrile solvent molecule. Two PF6− units are found on a crystallographic binary axis, therefore contributing just one half each to the asymmetric unit cell. The structure displays a peculiar stereochemistry of the cation. Three bidentate ligands around the Ru centre, together with the coordination of the non‐symmetric S atom, mean that these two atoms are chiral. This would lead to four stereoisomers, but only an enantiomeric pair was found in the analyzed sample. 相似文献
58.
M.R. Viotti A. Albertazzi A.V. Fantin A. Dal Pont 《Optics and Lasers in Engineering》2008,46(5):396-403
Shape measurements of engineering surfaces are an interesting and important application for white-light interferometry (WLI). Due to some factors such as: (a) the high-processing speed, (b) the ability to measure a huge quantity of points of the evaluated surface, and (c) the non-contacting nature; WLI has become a valuable tool for practical applications. This paper shows the achieved comparison between a modified white-light interferometer and an established measurement system, namely a formtester with a tactile spherical stylus sensor, which is the most commonly used instrument in the industry. Furthermore, this paper shows that the combination between the modified white-light interferometer and an adequate measurement and processing strategy has enabled to obtain a good agreement between optical and tactile measurements of long inner cylindrical surfaces. A cloud of points (COP) measured with the modified white-light interferometer has presented a standard deviation of about 0.3 μm when it was compared with formtester measurement of the same parts. 相似文献
59.
60.
Gradient bounds for minimizers of free discontinuity problems related to cohesive zone models in fracture mechanics 总被引:2,自引:0,他引:2
Gianni Dal Maso Adriana Garroni 《Calculus of Variations and Partial Differential Equations》2008,31(2):137-145
In this note we consider a free discontinuity problem for a scalar function, whose energy depends also on the size of the
jump. We prove that the gradient of every smooth local minimizer never exceeds a constant, determined only by the data of
the problem. 相似文献