全文获取类型
收费全文 | 31548篇 |
免费 | 4915篇 |
国内免费 | 2557篇 |
专业分类
化学 | 11049篇 |
晶体学 | 100篇 |
力学 | 3596篇 |
综合类 | 677篇 |
数学 | 10342篇 |
物理学 | 13256篇 |
出版年
2024年 | 66篇 |
2023年 | 361篇 |
2022年 | 887篇 |
2021年 | 974篇 |
2020年 | 944篇 |
2019年 | 848篇 |
2018年 | 787篇 |
2017年 | 1202篇 |
2016年 | 1336篇 |
2015年 | 1206篇 |
2014年 | 1841篇 |
2013年 | 2194篇 |
2012年 | 1886篇 |
2011年 | 1980篇 |
2010年 | 1750篇 |
2009年 | 1984篇 |
2008年 | 2094篇 |
2007年 | 2176篇 |
2006年 | 1814篇 |
2005年 | 1704篇 |
2004年 | 1591篇 |
2003年 | 1247篇 |
2002年 | 1148篇 |
2001年 | 909篇 |
2000年 | 795篇 |
1999年 | 763篇 |
1998年 | 648篇 |
1997年 | 567篇 |
1996年 | 505篇 |
1995年 | 505篇 |
1994年 | 321篇 |
1993年 | 308篇 |
1992年 | 232篇 |
1991年 | 237篇 |
1990年 | 190篇 |
1989年 | 137篇 |
1988年 | 168篇 |
1987年 | 119篇 |
1986年 | 96篇 |
1985年 | 100篇 |
1984年 | 70篇 |
1983年 | 48篇 |
1982年 | 65篇 |
1981年 | 55篇 |
1980年 | 34篇 |
1979年 | 43篇 |
1978年 | 21篇 |
1977年 | 12篇 |
1976年 | 9篇 |
1973年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
92.
Zhaohui Wang 《Thermochimica Acta》2004,414(1):31-33
Microcalorimetric measurements of excess molar enthalpies, at 298.15 K, are reported for the four binary systems formed by mixing 1-hexene with the cycloalkanes: cyclohexane and methylcyclohexane, and with the aromatic hydrocarcons: benzene and toluene. Smooth Redlich-Kister representations of the results are presented. It was found that the Liebermann-Fried model also provided good representations of the results. 相似文献
93.
Let H and K be indefinite inner product spaces. This paper shows that a bijective map φ:B(H)→B(K) satisfies φ(AB B A) =φ(A)φ(5) φ(B) φ(A) for every pair A,B ∈B(H) if and only if either φ(A) = cU AU for all A or φ(A) = cUA U for all A; φsatisfies φ(AB A) = φ(A)φ(B) φ(A) for every pair A,B ∈B(H) if and only if either φ(A) = UAV for all A or φ(A) = UA V for all A, where A denotes the indefinite conjugate of A, U and V are bounded invertible linear or conjugate linear operators with U U = c-1I and V V = cI for some nonzero real number c. 相似文献
94.
V. Z. Kasimov O. V. Ushakova Yu. P. Khomenko 《Journal of Applied Mechanics and Technical Physics》2003,44(5):612-619
An improved procedure for modeling the operation of a light-gas gun is proposed. The motion of working bodies in both the firing chamber and the light-gas chamber is studied within the framework of the mechanics of heterogeneous media. The problem of barrel heating taking into account its melting and removal of thermal ablation products into the medium inside the bore is solved in a coupled formulation. Heat and mass transfer and friction on the barrel surface are calculated using empirical dependences. The deformable piston is considered compressible and elastoviscoplastic. Allowance is made for the presence of a clearance between the lateral surface of the piston and the barrel bore walls and the associated gas flow between the firing and the light-gas chamber. Calculation results are given. 相似文献
95.
96.
研究非Chetaev型变质量非完整系统的Lie对称性与Noether对称性以及其间的 关系,给出Lie对称性导致Noether对称性以及Noether对称性导致Lie对称性的条件. 相似文献
97.
本文从非线性自然观的视野。引用与分析了社会经济系统功能模型与效应模型。构建了系统和谐状态模型与和谐状态可信度模型,形象地说明了企业系统的和谐既是一个随机不确定状态。又是企业和谐力量与不和谐力量相互抗争干涉的过程。依据协同学原理提出了企业系统和谐演进的机制,表明企业系统的和谐发展是子系统和谐协同的过程。即子系统竞争合作的过程。文中所构建的模型,从理论上清晰地说明了企业系统和谐有序运行的机理,为如何构建和谐企业。提供了建设性的思考。 相似文献
98.
Jocelyn Sabatier Serge Poullain Patrick Latteux Jean Luc Thomas Alain Oustaloup 《Nonlinear dynamics》2004,38(1-2):383-400
Robust speed control of a low damped electromechanical system with backlash is studied, controlled load angular speed being not measured. The proposed control strategy combines a Luenberger observer (load angular speed and load torque disturbance estimations) and a robust CRONE controller. The observer provides estimation of the load angular speed and of the disturbance torque applied on the load. Through the computation of only three independent parameters (as many as a PID controller), the CRONE controller permits to ensure the robust speed control of the load in spite of plant parametric variations and speed observation errors. The proposed control strategy is applied to a four mass experimental test bench. 相似文献
99.
Jenn‐Long Liu 《国际流体数值方法杂志》2004,44(12):1299-1315
This paper presents a relaxation algorithm, which is based on the overset grid technology, an unsteady three‐dimensional Navier–Stokes flow solver, and an inner‐ and outer‐relaxation method, for simulation of the unsteady flows of moving high‐speed trains. The flow solutions on the overlapped grids can be accurately updated by introducing a grid tracking technique and the inner‐ and outer‐relaxation method. To evaluate the capability and solution accuracy of the present algorithm, the computational static pressure distribution of a single stationary TGV high‐speed train inside a long tunnel is investigated numerically, and is compared with the experimental data from low‐speed wind tunnel test. Further, the unsteady flows of two TGV high‐speed trains passing by each other inside a long tunnel and at the tunnel entrance are simulated. A series of time histories of pressure distributions and aerodynamic loads acting on the train and tunnel surfaces are depicted for detailed discussions. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
100.