全文获取类型
收费全文 | 4077篇 |
免费 | 123篇 |
国内免费 | 22篇 |
专业分类
化学 | 2333篇 |
晶体学 | 25篇 |
力学 | 251篇 |
数学 | 863篇 |
物理学 | 750篇 |
出版年
2023年 | 26篇 |
2022年 | 27篇 |
2021年 | 75篇 |
2020年 | 65篇 |
2019年 | 75篇 |
2018年 | 48篇 |
2017年 | 60篇 |
2016年 | 138篇 |
2015年 | 124篇 |
2014年 | 122篇 |
2013年 | 251篇 |
2012年 | 270篇 |
2011年 | 255篇 |
2010年 | 176篇 |
2009年 | 149篇 |
2008年 | 238篇 |
2007年 | 239篇 |
2006年 | 195篇 |
2005年 | 180篇 |
2004年 | 202篇 |
2003年 | 155篇 |
2002年 | 152篇 |
2001年 | 60篇 |
2000年 | 37篇 |
1999年 | 43篇 |
1998年 | 44篇 |
1997年 | 48篇 |
1996年 | 57篇 |
1995年 | 47篇 |
1994年 | 57篇 |
1993年 | 32篇 |
1992年 | 33篇 |
1991年 | 30篇 |
1990年 | 28篇 |
1989年 | 21篇 |
1988年 | 35篇 |
1987年 | 30篇 |
1986年 | 21篇 |
1985年 | 42篇 |
1984年 | 35篇 |
1983年 | 29篇 |
1982年 | 34篇 |
1981年 | 33篇 |
1980年 | 23篇 |
1979年 | 31篇 |
1978年 | 22篇 |
1977年 | 19篇 |
1976年 | 18篇 |
1975年 | 16篇 |
1974年 | 17篇 |
排序方式: 共有4222条查询结果,搜索用时 109 毫秒
21.
22.
M.C. Ubaldi V. Stasi U. Colombo D. Piccinin M. Martinelli 《Photonics and Nanostructures》2007,5(2-3):145-148
Roughness reduction of a submicron waveguide profile in chemically amplified negative resist is here performed by proper selection of an alkali-based developer, taking into account that its smaller molecules lead to smoother resist surface by altering the developing mechanism of aggregate extraction performed with standard quaternary ammonium hydroxide. Roughness is then analyzed by means of classical Atomic Force Microscope inspection; furthermore, a non-invasive line edge roughness analysis approach based on top-down scanning electron microscope acquisition gives comparable results, in terms of standard deviation and molecular aggregate periodicity. 相似文献
23.
Modern trends in designing mechatronic systems call for a synergic design of the separated subsystems (mechanic, electronic parts, control modules, etc.) concurring to the overall performance. Following this point of view, this paper presents a control oriented model and a nonlinear control design for a Common Rail injection system. First a model is developed, which is tuned in a virtual simulation environment, representing the injection system in details in a reliable replication of reality. Then a sliding mode control is developed. Both the model of the injection process and of the control law are validated by a virtual detailed simulation environment. The prediction capability of the model and the control efficiency are clearly shown. 相似文献
24.
Francesco Catoni Roberto Cannata Paolo Zampetti 《Advances in Applied Clifford Algebras》2006,16(2):85-101
It is known that complex numbers can be associated with plane Euclidean geometry and their functions are successfully used
for studying extensions of Euclidean geometry, i.e., non-Euclidean geometries and surfaces differential geometry.
In this paper we begin to study the constant curvature spaces associated with the geometry generated by commutative elliptic-quaternions
and we show how the “mathematics” they generate allows us to introduce these spaces and obtain the geodesic equations without
developing a complete mathematical apparatus as the one developed for Riemannian geometry. 相似文献
25.
Daniele Andreucci Paolo Bisegna Emmanuele DiBenedetto 《Comptes Rendus Mathematique》2002,335(4):329-332
We compute the homogenized-concentrated limit for a pair of non-linearly coupled diffusion equations in a perforated cylindric domain with coaxial cylindric holes periodically distributed along its axis. This problem arises from visual transduction. To cite this article: D. Andreucci et al., C. R. Acad. Sci. Paris, Ser. I 335 (2002) 329–332. 相似文献
26.
We derive the Kramers equation, namely, the Fokker-Planck equation for an oscillator, from a completely deterministic picture. The oscillator is coupled to a “booster”, i.e., a deterministic system in a fully chaotic state, wherein diffusion is derived from the sensitive dependence of chaos on initial conditions and friction is a consequence of the linear response of the booster to the action exerted on it by the oscillator. To deal with the Hamiltonian nature of the system of interest and of its coupling to the booster, we extend the earlier theoretical derivation of macroscopic transport coefficients from deterministic dynamics. We show that the frequency of the oscillator can be tuned to the microscopic frequencies of the booster without affecting the canonical nature of the “macroscopic” statistics. The theoretical predictions are supported by numerical simulations. 相似文献
27.
Miloslav Duchoň Anatolij Dvurečenskij Paolo de Lucia 《International Journal of Theoretical Physics》1997,36(9):1941-1958
We present a solution to the moment problem for effect algebras, concerning mean values of all powers of an observable concentrated
on the interval [0, 1] for states from a convex set. We give a solution for particular examples, e.g., for the set of all
effect operators. We examine how this problem is related to a socalled E-property. Finally, we give a solution for observables
studied in the operational approach to physical theories. 相似文献
28.
This paper develops a mathematical model of the ring-spinning process that takes into account its non-stationary nature. A complex system of differential equations is obtained, which from a mathematical point of view constitutes a ‘free-boundary’ problem. Its solution involves definition of suitable boundary conditions related to the mechanical characteristics of the process and of the spinning machine itself. The boundary conditions which determine the solution are pointed out. A numerical solution of the system of differential equations can be obtained by the Finite-Segments method, as shown in an example. 相似文献
29.
30.