全文获取类型
收费全文 | 164篇 |
免费 | 6篇 |
国内免费 | 2篇 |
专业分类
化学 | 93篇 |
晶体学 | 2篇 |
力学 | 7篇 |
数学 | 14篇 |
物理学 | 56篇 |
出版年
2022年 | 3篇 |
2021年 | 1篇 |
2020年 | 2篇 |
2019年 | 4篇 |
2018年 | 1篇 |
2016年 | 2篇 |
2015年 | 2篇 |
2014年 | 3篇 |
2013年 | 4篇 |
2012年 | 8篇 |
2011年 | 4篇 |
2010年 | 6篇 |
2009年 | 6篇 |
2008年 | 10篇 |
2007年 | 8篇 |
2006年 | 6篇 |
2005年 | 4篇 |
2004年 | 2篇 |
2003年 | 2篇 |
2002年 | 2篇 |
2001年 | 3篇 |
2000年 | 11篇 |
1999年 | 2篇 |
1996年 | 5篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1993年 | 6篇 |
1992年 | 6篇 |
1991年 | 4篇 |
1990年 | 5篇 |
1989年 | 7篇 |
1988年 | 3篇 |
1987年 | 5篇 |
1986年 | 5篇 |
1985年 | 5篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1965年 | 1篇 |
1960年 | 1篇 |
排序方式: 共有172条查询结果,搜索用时 15 毫秒
31.
This paper presents a novel membrane design for capacitive micromachined ultrasonic transducers (cMUTs). The proposed design is composed of a thick membrane with reinforcing beams supported by a circumferential thin membrane to improve transducer sensitivity without degrading the membrane resonance frequency. Analytical formulation of sensitivity for the proposed design was newly derived and its validity was verified by finite element analysis (FEA). From the analysis, we confirmed that this thick membrane structure achieved three times higher sensitivity compared to the conventional design by decreasing 70 % of the mass of the thick membrane part with keeping the resonance frequency same. 相似文献
32.
Kumai R Horiuchi S Fujioka J Tokura Y 《Journal of the American Chemical Society》2012,134(2):1036-1046
Supramolecular ferroelectric cocrystals of phenazine (Phz) with chloranilic acid (H(2)ca), bromanilic acid (H(2)ba), and fluoranilic acid (H(2)fa) have been characterized by the interplay between their structural transformations and solid-state acid-base (proton transfer) reactions. At ambient pressure, the Phz-H(2)ca, Phz-H(2)ba, and their deuterated crystals exhibit incomplete proton displacement, which transforms the neutral molecules into semi-ionic at low temperatures below the Curie point (T(c)(IC) < T < T(c)(I)). For the cocrystal of the less acidic H(2)fa, the ferroelectric phase is induced only by applying hydrostatic pressure above ~0.6 GPa. According to the combined studies of temperature-dependent dielectric permittivity and synchrotron X-ray diffraction, it was proved that the ferroelectric (FE-I) phase is always accompanied at lower temperatures by successive phase transitions to the lattice modulated phases with incommensurate periodicities (IC phase, T(c)(II) < T < T(c)(IC)) and with commensurate (2- or 3-fold) periodicities (FE-II or FE-III phase, T < T(c)(II)). Whereas the ground-state structures at ambient pressure are different from one another among the Phz-H(2)ca (FE-II form), Phz-H(2)ba (FE-III form), and Phz-H(2)fa (paraelectric form), their systematic changes under pressure depict a universal pressure-temperature phase diagram. The possible origins of structural changes are assigned to the valence instability and the frustrated Coulomb interactions that induce the charge disproportionation (coexisting neutral ionic) states with the staging spatial orders. 相似文献
33.
Ryoichi Chiba Masaaki Izumi Yoshihiro Sugano 《Archive of Applied Mechanics (Ingenieur Archiv)》2008,78(1):61-74
Forced convection heat transfer in a non-Newtonian fluid flow inside a pipe whose external surface is subjected to non-axisymmetric
heat loads is investigated analytically. Fully developed laminar velocity distributions obtained by a power-law fluid rheology
model are used, and viscous dissipation is taken into account. The effect of axial heat conduction is considered negligible.
The physical properties are assumed to be constant. We consider that the smooth change in the velocity distribution inside
the pipe is piecewise constant. The theoretical analysis of the heat transfer is performed by using an integral transform
technique – Vodicka’s method. An important feature of this approach is that it permits an arbitrary distribution of the surrounding
medium temperature and an arbitrary velocity distribution of the fluid. This technique is verified by a comparison with the
existing results. The effects of the Brinkman number and rheological properties on the distribution of the local Nusselt number
are shown. 相似文献
34.
Tensile and Tensile-Mode Fatigue Testing of Microscale Specimens in Constant Humidity Environment 总被引:1,自引:0,他引:1
A tensile and tensile-mode-fatigue tester has been developed for testing microscale specimens in high humidity environments
in order to investigate the fracture mechanisms of microelectromechanical materials. A humidity control system was installed
on a tensile-mode fatigue tester equipped with an electrostatic force grip. A specimen and a griping device were inserted
into a small chamber and the humidity was controlled by air flow from a temperature and humidity chamber. The humidity stability
was within ±2%RH for humidities in the range 25–90%RH for eight hours of testing. Fatigue tests were performed on single-crystal
silicon (SCS) specimens in constant humidity environments and laboratory air for up to 106 cycles. The gauge length, width, and thickness of the SCS specimens were 100 or 500 μm, 13.0 μm, and 3.3 μm, respectively.
The average tensile strength was 3.68 GPa in laboratory air; this value decreased in high humidity environments. Fatigue failure
was observed during cyclic loading at stresses lower than the average strength. A reduction in the fatigue strength was observed
at high relative humidities. Different fracture origins and fracture behaviors were observed in tensile tests and fatigue
tests, which indicates that the water vapor in air affects the fatigue properties of SCS specimens. 相似文献
35.
Reiji Tanaka Yu Kurishiba Hideo Miyake Toshiyuki Shibata 《Molecules (Basel, Switzerland)》2022,27(11)
In this study, we aimed to isolate bacteria capable of degrading the polysaccharide ulvan from the green algae Ulva sp. (Chlorophyta, Ulvales, Ulvaceae) in marine environments. We isolated 13 ulvan-degrading bacteria and observed high diversity at the genus level. Further, the genera Paraglaciecola, Vibrio, Echinicola, and Algibacter, which can degrade ulvan, were successfully isolated for the first time from marine environments. Among the 13 isolates, only one isolate (Echinicola sp.) showed the ability not only to produce externally expressed ulvan lyase, but also to be periplasmic or on the cell surface. From the results of the full-genome analysis, lyase was presumed to be a member of the PL25 (BNR4) family of ulvan lyases, and the bacterium also contained the sequence for glycoside hydrolase (GH43, GH78 and GH88), which is characteristic of other ulvan-degrading bacteria. Notably, this bacterium has a unique ulvan lyase gene not previously reported. 相似文献
36.
In previous papers it was shown that in phase space a generator of gauge transformations for a singular Lagrangian \(L(q,\dot q)\) is given byG[εα]=ε k α φ α k (q,p,t) where φ α k are first class constraints andG is subjected to a stationarity condition. A non-trivial extension from velocity (or momentum) independent gauge transformations to velocity dependent ones is realized, by replacing gauge functions εα(t) with momentum dependent functions εα(q,p,t), as long asG satisfies the stationarity condition. Inversely, it is proved in a classical framework that, within velocity dependent gauge transformations, all generators of gauge transformations can be expressed in terms of the linear combinations of φ α k . 相似文献
37.
Abachi S Derrick M Kooijman P Musgrave B Price L Repond J Sugano K Blockus D Brabson BB Brom J Jung C Ogren H Rust DR Snyder A Cork B Akerlof C Chapman J Errede D Ken MT Kesten P Meyer DI Neal H Nitz D Thun R Tschirhart R Baringer P Bylsma BG Debonte R Low EH McIlwain RL Miller DH Ng CR Rangan K Shibata E 《Physical review D: Particles and fields》1990,41(7):2045-2056
38.
39.
In this paper, it is shown that a necessary and sufficient condition for the existence of aP
3-factorization ofK
m
n
is (i)mn 0(mod 3) and (ii) (m – 1)n 0(mod 4). 相似文献
40.
Jung C Abachi S Akerlof C Baringer P Beltrami I Blockus D Bonvicini G Brabson B Brom JM Bylsma BG Chapman J Cork B DeBonte R Derrick M Errede D Gan KK Gray SW Guillaud J Harnew N Kesten P Koltick D Kooijman P Loeffler FJ Loos JS Low EH McIlwain RL Meyer DI Miller DH Musgrave B Neal H Ng CR Nitz D Ogren H Price LE Rangan LK Repond J Rust DR Schlereth J Shibata EI Sugano K Thun R Trinko T Valdata-Nappi M Weiss JM Willutzky M Wood DE 《Physical review letters》1986,56(17):1775-1778