全文获取类型
收费全文 | 930篇 |
免费 | 53篇 |
国内免费 | 8篇 |
专业分类
化学 | 550篇 |
晶体学 | 8篇 |
力学 | 20篇 |
数学 | 284篇 |
物理学 | 129篇 |
出版年
2023年 | 12篇 |
2022年 | 41篇 |
2021年 | 44篇 |
2020年 | 40篇 |
2019年 | 46篇 |
2018年 | 40篇 |
2017年 | 38篇 |
2016年 | 48篇 |
2015年 | 38篇 |
2014年 | 41篇 |
2013年 | 70篇 |
2012年 | 51篇 |
2011年 | 55篇 |
2010年 | 34篇 |
2009年 | 37篇 |
2008年 | 48篇 |
2007年 | 45篇 |
2006年 | 31篇 |
2005年 | 27篇 |
2004年 | 21篇 |
2003年 | 22篇 |
2002年 | 22篇 |
2001年 | 4篇 |
2000年 | 6篇 |
1999年 | 3篇 |
1998年 | 4篇 |
1997年 | 7篇 |
1996年 | 6篇 |
1994年 | 6篇 |
1993年 | 5篇 |
1991年 | 5篇 |
1988年 | 4篇 |
1987年 | 3篇 |
1985年 | 5篇 |
1982年 | 3篇 |
1978年 | 5篇 |
1977年 | 5篇 |
1976年 | 8篇 |
1975年 | 3篇 |
1974年 | 4篇 |
1973年 | 6篇 |
1938年 | 2篇 |
1936年 | 2篇 |
1934年 | 2篇 |
1898年 | 2篇 |
1875年 | 2篇 |
1867年 | 6篇 |
1866年 | 3篇 |
1863年 | 4篇 |
1862年 | 3篇 |
排序方式: 共有991条查询结果,搜索用时 15 毫秒
101.
102.
We demonstrate the advantages of randomization in coherent quantum dynamical control. For systems which are either time-varying or require decoupling cycles involving a large number of operations, we find that simple randomized protocols offer superior convergence and stability as compared to deterministic counterparts. In addition, we show how randomization may allow us to outperform purely deterministic schemes at long times, including combinatorial and concatenated methods. General criteria for optimally interpolating between deterministic and stochastic design are proposed and illustrated in explicit decoupling scenarios relevant to quantum information storage. 相似文献
103.
A method for the simultaneous determination of 4(5)-methylimidazole (4MeI) and 2-acetyl-4(5)-(1,2,3,4-tetrahydroxybutyl)-imidazole (THI) was developed using SPE and HPLC/MS. Solid-phase extraction using SCX Disc cartridges was used for isolation of the analytes from liquid samples. The lower LOQwas 0.1 ng/mL for 4MeI and 0.2 ng/ mL for THI. The linearity of the calibration curves was satisfactory as indicated by correlation coefficients >0.999. The CV for the intra- and inter-day precision was <5% (n = 6); the accuracy was in the range 98-103%. The recovery was > or = 97 and > or = 98% for THI and 4MeI, respectively. The method was used to determine THI and 4MeI in beverages, coffee, caramel colours and other samples. 相似文献
104.
Hilde Lea Lein Øystein Skottun Andersen Per Erik Vullum Edgar Lara-Curzio Randi Holmestad Mari-Ann Einarsrud Tor Grande 《Journal of Solid State Electrochemistry》2006,10(8):635-642
Young’s modulus, strain–stress behavior, fracture strength, and fracture toughness of (0≤×≤1) materials have been investigated in the temperature range 20–1,000°C. Young’s moduli of and , measured by resonant ultrasound spectroscopy, were 130±1 and 133±3 GPa, respectively. The nonlinear stress–strain relationship
observed by four-point bending at room temperature was inferred as a signature of ferroelastic behavior of the materials.
Above the ferroelastic to paraelastic transition temperature, the materials showed elastic behavior, but due to high-temperature
creep, a nonelastic respond reappeared above ∼800°C. The room temperature fracture strength measured by four-point bending
was in the range 107–128 MPa. The corresponding fracture toughness of , measured by single edge V-notch beam method, was 1.16±0.12 MPa·m1/2. The measured fracture strength and fracture toughness were observed to increase with increasing temperature. The fracture
mode changed from intragranular at low temperature to intergranular at high temperature. Tensile stress gradient at the surface
of the materials caused by a frozen-in gradient in the oxygen content during cooling was proposed to explain the low ambient
temperature fracture strength and toughness. 相似文献
105.
The observation of isolated positive and negative charges, but not isolated magnetic north and south poles, is an old puzzle. Instead, evidence of effective magnetic monopoles has been found in the abstract momentum space. Apart from Hall-related effects, few observable consequences of these abstract monopoles are known. Here, we show that it is possible to manipulate the monopoles by external magnetic fields and probe them by universal conductance fluctuation measurements in ferromagnets with strong spin-orbit coupling. The observed fluctuations are not noise, but reproducible quasiperiodic oscillations as a function of magnetization direction, a novel Berry phase fingerprint of the magnetic monopoles. 相似文献
106.
In this paper we consider strong bilevel vector equilibrium problems and introduce the concepts of Levitin–Polyak well-posedness and Levitin–Polyak well-posedness in the generalized sense for such problems. The notions of upper/lower semicontinuity involving variable cones for vector-valued mappings and their properties are proposed and studied. Using these generalized semicontinuity notions, we investigate sufficient and/or necessary conditions of the Levitin–Polyak well-posedness for the reference problems. Some metric characterizations of these Levitin–Polyak well-posedness concepts in the behavior of approximate solution sets are also discussed. As an application, we consider the special case of traffic network problems with equilibrium constraints. 相似文献
107.
108.
Let T be a bounded multilinear operator on some product of Lq(Rn) spaces. Assume that T has a non-smooth associated kernel which satisfies certain weak regularity conditions but not regular enough to fall under the scope of the standard multilinear Calderón-Zygmund theory. The main aim of this paper is to establish a sufficient condition on the kernel of T so that the commutator of a vector BMO function and T is bounded on certain product Lp(Rn) spaces. We obtain boundedness of the commutator of and T by first proving certain pointwise estimates on the Fefferman-Stein sharp maximal operator. An important example of multilinear operators which satisfy our kernel conditions is the maximal mth order Calderón commutator. 相似文献
109.
Upper semicontinuity result for the solution mapping of a mixed parametric generalized vector quasiequilibrium problem with moving cones 总被引:1,自引:0,他引:1
In this paper, we give sufficient conditions for the upper semicontinuity property of the solution mapping of a parametric
generalized vector quasiequilibrium problem with mixed relations and moving cones. The main result is proven under the assumption
that moving cones have local openness/local closedness properties and set-valued maps are cone-semicontinuous in a sense weaker
than the usual sense of semicontinuity. The nonemptiness and the compactness of the solution set are also investigated. 相似文献
110.
This paper gives sufficient conditions for the upper and lower semicontinuities of the solution mapping of a parametric mixed generalized Ky Fan inequality problem. We use a new scalarizing approach quite different from traditional linear scalarization approaches which, in the framework of the stability analysis of solution mappings of equilibrium problems, were useful only for weak vector equilibrium problems and only under some convexity and strict monotonicity assumptions. The main tools of our approach are provided by two generalized versions of the nonlinear scalarization function of Gerstewitz. Our stability results are new and are obtained by a unified technique. An example is given to show that our results can be applied, while some corresponding earlier results cannot. 相似文献