全文获取类型
收费全文 | 147168篇 |
免费 | 12328篇 |
国内免费 | 10671篇 |
专业分类
化学 | 17567篇 |
晶体学 | 1095篇 |
力学 | 16323篇 |
综合类 | 1146篇 |
数学 | 29210篇 |
物理学 | 26911篇 |
综合类 | 77915篇 |
出版年
2024年 | 550篇 |
2023年 | 1495篇 |
2022年 | 2650篇 |
2021年 | 2914篇 |
2020年 | 3339篇 |
2019年 | 2940篇 |
2018年 | 2966篇 |
2017年 | 3959篇 |
2016年 | 4426篇 |
2015年 | 4436篇 |
2014年 | 7087篇 |
2013年 | 8333篇 |
2012年 | 8617篇 |
2011年 | 9366篇 |
2010年 | 7429篇 |
2009年 | 8664篇 |
2008年 | 8056篇 |
2007年 | 9768篇 |
2006年 | 8494篇 |
2005年 | 7982篇 |
2004年 | 7011篇 |
2003年 | 6377篇 |
2002年 | 5635篇 |
2001年 | 4726篇 |
2000年 | 4334篇 |
1999年 | 3965篇 |
1998年 | 3431篇 |
1997年 | 3051篇 |
1996年 | 2645篇 |
1995年 | 2320篇 |
1994年 | 2087篇 |
1993年 | 1833篇 |
1992年 | 1680篇 |
1991年 | 1454篇 |
1990年 | 1334篇 |
1989年 | 1084篇 |
1988年 | 950篇 |
1987年 | 725篇 |
1986年 | 429篇 |
1985年 | 346篇 |
1984年 | 286篇 |
1983年 | 143篇 |
1982年 | 192篇 |
1981年 | 133篇 |
1980年 | 67篇 |
1979年 | 97篇 |
1978年 | 79篇 |
1977年 | 78篇 |
1976年 | 42篇 |
1973年 | 32篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
陈宝灯 《福建师范大学学报(自然科学版)》1995,(1)
本文作者应用教学教育过程最优化的理论与方法,指导体操教学训练。经过多年的探索,实践证明要提高教学训练的效益和质量,就应发挥教学系统的整体功能,选择最佳教学方法,突出教学重点,抓住关键环节。 相似文献
12.
标枪技术课教法改革实验研究 总被引:1,自引:0,他引:1
李登光 《陕西师范大学学报(自然科学版)》1996,(3)
在标枪技术课教学过程中,从整体性出发,以助跑投枪为主,创编投掷标枪技术课的教学方法.以本校体育系94级本科33名男学生为对象进行实验研究.结果表明,采用新教法可使标枪技术课教学周期缩短一半,有助于技术动作的掌握和质量的提高.实验组整体成绩明显优于对照组,说明新教法是行之有效的 相似文献
13.
14.
P.A. Ramachandran 《Numerical Methods for Partial Differential Equations》2006,22(4):831-846
Time‐dependent differential equations can be solved using the concept of method of lines (MOL) together with the boundary element (BE) representation for the spatial linear part of the equation. The BE method alleviates the need for spatial discretization and casts the problem in an integral format. Hence errors associated with the numerical approximation of the spatial derivatives are totally eliminated. An element level local cubic approximation is used for the variable at each time step to facilitate the time marching and the nonlinear terms are represented in a semi‐implicit manner by a local linearization at each time step. The accuracy of the method has been illustrated on a number of test problems of engineering significance. © 2005 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 2006 相似文献
15.
Lorenz混沌系统的输入—输出性质分析 总被引:1,自引:0,他引:1
研究了Lorenz混沌系统的一类输入—输出性质,采用Lyapunov直接方法和数值仿真等研究方法,对Lorenz混沌系统的解的范数分别与输入信号的振幅、角频率之间的关系进行了分析,得出了诸多有意义而在线性系统中没有的结论,这对进一步研究Lorenz系统有重要的参考意义。 相似文献
16.
David K Bisset 《国际流体数值方法杂志》2002,39(10):961-977
Turbulent flow simulation methods based on finite differences are attractive for their simplicity, flexibility and efficiency, but not always for accuracy or stability. This paper demonstrates that a good compromise is possible with the advected grid explicit (AGE) method. Starting from the same initial field as a previous spectral DNS, AGE method simulations of a planar turbulent wake were carried out as DNS, and then at three levels of reduced resolution. The latter cases were in a sense large‐eddy simulations (LES), although no specific sub‐grid‐scale model was used. Results for the two DNS methods, including variances and power spectra, were very similar, but the AGE simulation required much less computational effort. Small‐scale information was lost in the reduced resolution runs, but large‐scale mean and instantaneous properties were reproduced quite well, with further large reductions in computational effort. Quality of results becomes more sensitive to the value chosen for one of the AGE method parameters as resolution is reduced, from which it is inferred that the numerical stability procedure controlled by the parameter is acting in part as a sub‐grid‐scale model. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
17.
A simple scheme is developed for treatment of vertical bed topography in shallow water flows. The effect of the vertical step on flows is modelled with the shallow water equations including local energy loss terms. The bed elevation is denoted with zb‐ for the left and zb+ for the right values at each grid point, hence exactly representing a discontinuity in the bed topography. The surface gradient method (SGM) is generalized to reconstruct water depths at cell interfaces involving a vertical step so that the fluxes at the cell interfaces can accurately be calculated with a Riemann solver. The scheme is verified by predicting a surge crossing a step, a tidal flow over a step and dam‐break flows on wet/dry beds. The results have shown good agreements compared with analytical solutions and available experimental data. The scheme is efficient, robust, and may be used for practical flow calculations. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
18.
Rakhim Aitbayev 《Numerical Methods for Partial Differential Equations》2006,22(4):847-866
Efficient multilevel preconditioners are developed and analyzed for the quadrature finite element Galerkin approximation of the biharmonic Dirichlet problem. The quadrature scheme is formulated using the Bogner–Fox–Schmit rectangular element and the product two‐point Gaussian quadrature. The proposed additive and multiplicative preconditioners are uniformly spectrally equivalent to the operator of the quadrature scheme. The preconditioners are implemented by optimal algorithms, and they are used to accelerate convergence of the preconditioned conjugate gradient method. Numerical results are presented demonstrating efficiency of the preconditioners. © 2005 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 2006 相似文献
19.
柴国庆 《湖北师范学院学报(自然科学版)》2002,22(3):5-10
用Tonelli方法研究了Banach空间中n阶非线性积分—微分方程初值问题,在非线性增长条件下,获得了初值问题解的存在性及其Tonelli迭代逼近。 相似文献
20.
用增量有限元法计算金属流动 总被引:1,自引:0,他引:1
利用增量有限元理论 ,对金属材料的变形过程进行模拟。为了模拟工程中塑性变形较大的构件的变形规律 ,在每个加载步迭代完成后自动实现坐标更新。 相似文献