全文获取类型
收费全文 | 4497篇 |
免费 | 162篇 |
国内免费 | 24篇 |
专业分类
化学 | 3067篇 |
晶体学 | 28篇 |
力学 | 170篇 |
数学 | 807篇 |
物理学 | 611篇 |
出版年
2023年 | 31篇 |
2022年 | 49篇 |
2021年 | 64篇 |
2020年 | 68篇 |
2019年 | 92篇 |
2018年 | 61篇 |
2017年 | 43篇 |
2016年 | 119篇 |
2015年 | 131篇 |
2014年 | 149篇 |
2013年 | 233篇 |
2012年 | 338篇 |
2011年 | 357篇 |
2010年 | 244篇 |
2009年 | 212篇 |
2008年 | 271篇 |
2007年 | 289篇 |
2006年 | 282篇 |
2005年 | 273篇 |
2004年 | 253篇 |
2003年 | 169篇 |
2002年 | 179篇 |
2001年 | 61篇 |
2000年 | 60篇 |
1999年 | 42篇 |
1998年 | 44篇 |
1997年 | 42篇 |
1996年 | 33篇 |
1995年 | 32篇 |
1994年 | 36篇 |
1993年 | 37篇 |
1992年 | 18篇 |
1991年 | 19篇 |
1990年 | 12篇 |
1989年 | 22篇 |
1987年 | 11篇 |
1986年 | 14篇 |
1985年 | 20篇 |
1984年 | 30篇 |
1983年 | 18篇 |
1982年 | 27篇 |
1981年 | 20篇 |
1980年 | 28篇 |
1979年 | 17篇 |
1978年 | 20篇 |
1977年 | 15篇 |
1976年 | 16篇 |
1975年 | 15篇 |
1974年 | 16篇 |
1973年 | 13篇 |
排序方式: 共有4683条查询结果,搜索用时 15 毫秒
1.
Corinne Rondeau-Mouro Mireille Cambert Laurent Blondel Yves Diascorn Léo Mbaya Nor Nadiah Binti Ahmad Nazari Sarah Helary Tiphaine Lucas 《Magnetic resonance in chemistry : MRC》2022,60(7):678-691
A temperature control unit was implemented to vary the temperature of samples studied on a commercial Mobile Universal Surface Explorer nuclear magnetic resonance (MOUSE-NMR) apparatus. The device was miniaturized to fit the maximum MOUSE sampling depth (25 mm). It was constituted by a sample holder sandwiched between two heat exchangers placed below and above the sample. Air was chosen as the fluid to control the temperature at the bottom of the sample, at the interface between the NMR probe and the sample holder, in order to gain space. The upper surface of the sample was regulated by the circulation of water inside a second heat exchanger placed above the sample holder. The feasibility of using such a device was demonstrated first on pure water and then on several samples of bread dough with different water contents. For this, T1 relaxation times were measured at various temperatures and depths and were then compared with those acquired with a conventional compact closed-magnet spectrometer. Discussion of results was based on biochemical transformations in bread dough (starch gelatinization and gluten heat denaturation). It was demonstrated that, within a certain water level range, and because of the low magnetic field strength of the MOUSE, a linear relationship could be established between T1 relaxation times and the local temperature in the dough sample. 相似文献
2.
Florence Drui Emmanuel Franck Philippe Helluy Laurent Navoret 《Comptes Rendus Mecanique》2019,347(3):259-269
The over-relaxation approach is an alternative to the Jin–Xin relaxation method in order to apply the equilibrium source term in a more precise way. This is also a key ingredient of the lattice Boltzmann method for achieving second-order accuracy. In this work, we provide an analysis of the over-relaxation kinetic scheme. We compute its equivalent equation, which is particularly useful for devising stable boundary conditions for the hidden kinetic variables. 相似文献
3.
4.
Investment projects and businesses can be entered or exited at a cost, and the theory of real option teaches us how to find optimal activity levels that should trigger entry or exit. However, in practice, different managers or owners operate under different constraints and might apply different thresholds to the same business. We are interested in the hedging of the risk related to the cost of sub-optimal entry or exit. We introduce a new class of derivative products that can hedge this risk. The pricing of these derivatives involves the joint law of a Brownian excursion and its supremum, which is calculated thanks to Bessel processes-related distribution laws. 相似文献
5.
Christelle de Bellefontaine Flore Josse Martine Domurado Dominique Domurado 《Applied biochemistry and biotechnology》1994,48(2):117-123
In order to detect low levels of enzyme activity, specifically glucose oxidase, in biological samples, an immunoenzymatic assay was developed since currently available methods could not be used because of either their lack of sensitivity or the conditions prevailing in our samples: turbidity of the medium, presence of redox systems other than glucose oxidase, and high concentration of proteins. The principle of the method is to coat a polystyrene surface with a fragment Fc-specific anti-IgG, then with an antibody directed against the looked-for enzyme, which is simultaneously the antigen and the enzyme activity required for immunoenzymatic detection. We applied this concept to biological samples after glucose oxidase administration to mice. This method achieves specificity and sensitivity (20 ng/mL or 1 ng) with samples of biological origin. No marker is needed since the antigen itself possesses an enzyme activity. This method, which requires a small sample volume (50 ΜL, 20 ΜL, if necessary), can be extended easily to the many enzymes currently used as markers. It could also be applied to the native enzymes of medical interest for which antibodies and a colorimetric reaction are available. 相似文献
6.
Julien Villard Houman Borouchaki Dominique Chapelle 《Comptes Rendus Mathematique》2002,335(6):561-566
Numerical simulation methods regarding fabric and cloth draping are generally based on mechanical models. These models are usually applied to uniform grids representing the true geometry of the fabric. Fabrics being a very flexible material, wrinkles appear on its surface when submitted to free or constrained motion. The main problem of the simulation is to represent realistically cloth surface motion. This is strongly dependent on the surface discretization. We present a new cloth animation scheme based on adaptive surface discretization. It can be seen as a multi-grid method which allows us to obtain realistic simulations. We propose also a new mechanical model well suited to our adaptive meshing strategy. A numerical example is given to show the efficiency of the method. To cite this article: J. Villard et al., C. R. Acad. Sci. Paris, Ser. I 335 (2002) 561–566. 相似文献
7.
8.
In this Note, we propose a finite element method with Lagrange multipliers in order to approximate contact problems with friction. The discretized normal and tangential constraints at the candidate contact interface are expressed by using continuous piecewise linear Lagrange multipliers in the saddle-point formulation. An optimal error estimate is established and several numerical studies corresponding to this choice of the discretized normal and tangential constraints are achieved. To cite this article: L. Baillet, T. Sassi, C. R. Acad. Sci. Paris, Ser. I 334 (2002) 917–922. 相似文献
9.
Laurent Gosse. 《Mathematics of Computation》2002,71(238):553-582
This paper investigates the behavior of numerical schemes for nonlinear conservation laws with source terms. We concentrate on two significant examples: relaxation approximations and genuinely nonhomogeneous scalar laws. The main tool in our analysis is the extensive use of weak limits and nonconservative products which allow us to describe accurately the operations achieved in practice when using Riemann-based numerical schemes. Some illustrative and relevant computational results are provided.
10.
If the Riemann–Christoffel tensor associated with a field of class of positive definite symmetric matrices of order three vanishes in a connected and simply connected open subset , then this field is the metric tensor field associated with a deformation of class of the set , uniquely determined up to isometries of . We establish here that the mapping defined in this fashion is continuous, for ad hoc metrizable topologies. To cite this article: P.G. Ciarlet, F. Laurent, C. R. Acad. Sci. Paris, Ser. I 335 (2002) 489–493. 相似文献