全文获取类型
收费全文 | 15029篇 |
免费 | 1415篇 |
国内免费 | 1461篇 |
专业分类
化学 | 3839篇 |
晶体学 | 226篇 |
力学 | 1914篇 |
综合类 | 240篇 |
数学 | 9228篇 |
物理学 | 2458篇 |
出版年
2024年 | 34篇 |
2023年 | 148篇 |
2022年 | 182篇 |
2021年 | 250篇 |
2020年 | 387篇 |
2019年 | 346篇 |
2018年 | 320篇 |
2017年 | 388篇 |
2016年 | 433篇 |
2015年 | 318篇 |
2014年 | 607篇 |
2013年 | 1059篇 |
2012年 | 766篇 |
2011年 | 905篇 |
2010年 | 880篇 |
2009年 | 962篇 |
2008年 | 1020篇 |
2007年 | 1091篇 |
2006年 | 898篇 |
2005年 | 820篇 |
2004年 | 749篇 |
2003年 | 776篇 |
2002年 | 644篇 |
2001年 | 509篇 |
2000年 | 489篇 |
1999年 | 426篇 |
1998年 | 380篇 |
1997年 | 316篇 |
1996年 | 271篇 |
1995年 | 241篇 |
1994年 | 202篇 |
1993年 | 143篇 |
1992年 | 139篇 |
1991年 | 109篇 |
1990年 | 97篇 |
1989年 | 70篇 |
1988年 | 71篇 |
1987年 | 55篇 |
1986年 | 60篇 |
1985年 | 59篇 |
1984年 | 48篇 |
1983年 | 25篇 |
1982年 | 55篇 |
1981年 | 43篇 |
1980年 | 29篇 |
1979年 | 23篇 |
1978年 | 15篇 |
1977年 | 9篇 |
1976年 | 11篇 |
1972年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Koumei Tanaka 《Mathematical Methods in the Applied Sciences》2006,29(12):1451-1466
We consider a compressible viscous fluid with the velocity at infinity equal to a strictly non‐zero constant vector in ?3. Under the assumptions on the smallness of the external force and velocity at infinity, Novotny–Padula (Math. Ann. 1997; 308 :439– 489) proved the existence and uniqueness of steady flow in the class of functions possessing some pointwise decay. In this paper, we study stability of the steady flow with respect to the initial disturbance. We proved that if H3‐norm of the initial disturbance is small enough, then the solution to the non‐stationary problem exists uniquely and globally in time, which satisfies a uniform estimate on prescribed velocity at infinity and converges to the steady flow in Lq‐norm for any number q? 2. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
22.
High temperature oxidation of metals leads to residual stresses both in the metal and in the growing oxide. In this work, the evolution of this residual stresses is theoretically predicted in the growing oxide layers. The origin of these stresses is based on a microstructural model. Using experimental results providing from the oxidation kinetics, and an analysis proposed to describe the growth strain occurring in the thin layers, a set of equations is established allowing determining the stresses evolution with oxidation time. Then, the model is compared with experimental results obtained on both α-Fe and phosphated α-Fe, oxidised at different temperatures. Numerical data are extracted from experiments either with an asymptotic formulation or with an inverse method. These two methods give good agreement with experiments and allow extracting the model parameters. 相似文献
23.
ON THE UNIQUENESS OF THE WEAK SOLUTIONS OF A QUASILINEAR HYPERBOLIC SYSTEM WITH A SINGULAR SOURCE TERM
下载免费PDF全文
![点击此处可从《数学年刊B辑(英文版)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
This paper is a continuation of the authors'previous paper[1].In this paper the authorsprove,assuming additional conditions on the initial data,some results about the existence anduniqueness of the entropy weak solutions of the Cauchy problem for the singular hyperbolicsystem a_t+(au)_x_2au/x=0,u_t+1/2(a~2+u~2)_x=0,x>0,t≥0. 相似文献
24.
非线性奇异边值问题的正解 总被引:1,自引:0,他引:1
路慧芹 《应用泛函分析学报》2002,4(3):217-221
利用锥映射的不动点指数定量,研究了一类非线性奇异边值问题多个正解的存在性问题。在构造的解的存在条件之下,证明了奇异边值问题至少有两个正解的存在性定理。 相似文献
25.
Mingxin Wang 《Journal of Mathematical Analysis and Applications》2002,274(1):424-436
This paper deals with positive solutions of degenerate and quasilinear parabolic systems not in divergence form: ut=up(Δu+av), vt=vq(Δv+bu), with null Dirichlet boundary conditions and positive initial conditions, where p, q, a and b are all positive constants. The local existence and uniqueness of classical solution are proved. Moreover, it will be proved that all solutions exist globally if and only if ab?λ12, where λ1 is the first eigenvalue of −Δ in Ω with homogeneous Dirichlet boundary condition. 相似文献
26.
27.
During the course of our investigation of the electron transfer properties of some redox species through highly hydrophobic
long chain alkanethiol molecules on gold in aqueous and non-aqueous solvents, we obtained some intriguing results such as
unusually low interfacial capacitance, very high values of impedance and film resistance, all of which pointed to the possible
existence of a nanometer size interfacial gap between the hydrophobic monolayer and aqueous electrolyte. We explain this phenomenon
by a model for the alkanethiol monolayer—aqueous electrolyte interface, in which the extremely hydrophobic alkanethiol film
repels water molecules adjacent to it and in the process creates a shield between the monolayer film and water. This effectively
increases the overall thickness of the dielectric layer that is manifested as an abnormally low value of interfacial capacitance.
This behaviour is very much akin to the ‘drying transition’ proposed by Lum, Chandler and Weeks in their theory of length
scale dependent hydrophobicity. For small hydrophobic units consisting of apolar solutes, the water molecules can reorganize
around them without sacrificing their hydrogen bonds. Since for an extended hydrophobic unit, the existence of hydrogen bonded
water structure close to it is geometrically unfavourable, there is a net depletion of water molecules in the vicinity leading
to the possible creation of a hydrophobic interfacial gap. 相似文献
28.
李治明 《新疆大学学报(理工版)》2004,21(2):135-141,146
研究了具有开发的单种群非自治周期系统.利用非自治微分方程理论.以及变分法理论和泛函极值的Euler方程方法,得到了该开发系统的持续生存性.周期解存在性,全局渐近稳定性.研究了在开发情况下的最大收获量问题,以及取得最大经济效益下的收获问题等. 相似文献
29.
30.
Vincenzo Santagada Ferdinando FiorinoElisa Perissutti Beatrice SeverinoSara Terracciano Giuseppe CirinoGiuseppe Caliendo 《Tetrahedron letters》2003,44(6):1145-1148
A novel and convenient microwave-assisted dimerization of an active peptide compound using the DKPs as scaffold is described. The key reaction giving rise to the diketopiperazine scaffold is the intermolecular coupling. No epimerization was detected in the reactions used. Conventional and microwave heating of the reactions are compared. Synthesis by microwave irradiation gave the desired compounds in higher yields and in shorter reaction times than those obtained by conventional heating. 相似文献