全文获取类型
收费全文 | 15764篇 |
免费 | 2622篇 |
国内免费 | 961篇 |
专业分类
化学 | 1406篇 |
晶体学 | 47篇 |
力学 | 2596篇 |
综合类 | 122篇 |
数学 | 2338篇 |
物理学 | 6919篇 |
综合类 | 5919篇 |
出版年
2024年 | 55篇 |
2023年 | 156篇 |
2022年 | 244篇 |
2021年 | 313篇 |
2020年 | 384篇 |
2019年 | 347篇 |
2018年 | 350篇 |
2017年 | 416篇 |
2016年 | 463篇 |
2015年 | 412篇 |
2014年 | 750篇 |
2013年 | 845篇 |
2012年 | 872篇 |
2011年 | 1029篇 |
2010年 | 823篇 |
2009年 | 841篇 |
2008年 | 929篇 |
2007年 | 1072篇 |
2006年 | 975篇 |
2005年 | 987篇 |
2004年 | 865篇 |
2003年 | 806篇 |
2002年 | 652篇 |
2001年 | 659篇 |
2000年 | 588篇 |
1999年 | 472篇 |
1998年 | 427篇 |
1997年 | 362篇 |
1996年 | 318篇 |
1995年 | 267篇 |
1994年 | 246篇 |
1993年 | 252篇 |
1992年 | 203篇 |
1991年 | 200篇 |
1990年 | 162篇 |
1989年 | 149篇 |
1988年 | 128篇 |
1987年 | 96篇 |
1986年 | 48篇 |
1985年 | 34篇 |
1984年 | 32篇 |
1983年 | 15篇 |
1982年 | 26篇 |
1981年 | 18篇 |
1980年 | 12篇 |
1979年 | 13篇 |
1977年 | 5篇 |
1973年 | 7篇 |
1971年 | 5篇 |
1955年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
关于非线性Pochhammer-Chree方程的解 总被引:7,自引:0,他引:7
本文研究了弹性杆纵向形变方程:u_(tt)—u_(ttxx)—u_(xx)—(1/3)(u~3)xx=0的椭圆余弦波解,并用Adomian分解法,求出了其初边值问题解. 相似文献
82.
李文斌 《湖南科技大学学报(自然科学版)》1996,(2)
本文通过对单涂层吸波材料内电磁波传输损耗机理的细致研究,提出了单涂层吸波材料优化设计的两项原则。结合具体实例详细说明这两项原则的具体应用,最后讨论涂层电磁参量在偏离匹配条件的情况下,对涂层吸波性能影响的具体结果分析。图3.表1,参3。 相似文献
83.
Laser gas-assisted material processing finds wide application in industry. The modelling of heating, elastic response of the substrate material, and the wave analysis gives insight into the laser workpiece interaction. In the present study, laser gas-assisted heating of steel is considered. The normal component of the thermal stress is taken as the source of load for the flexural wave generation in the material. The flexural wave generated is simulated and the wave characteristics are analyzed at four locations at the workpiece surface. The numerical scheme employing a control volume approach is introduced when solving the governing equations of flow and heat transfer while finite element and spectran element methods are used when solving the stress and wave equations. It is found that the normal component of the stress is tensile. The dispersion effect of the workpiece material, interference of the reflected beam, and partial overlapping of second mode of the travelling wave enable to identify a unique pattern in the travelling wave in the substrate. 相似文献
84.
SHIMIZU Jun EDA Hiroshi 《厦门大学学报(自然科学版)》2002,(Z1)
This study aims to reduce the work-affected layer of the machined surface by carrying out the grinding at the speed over static pr o pagation speed of plastic wave of ductile materials and also aims to clarify suc h super high-speed machining mechanism.This paper reports on the result obtain ed through the molecular dynamics simulations and experiments on the super-spee d grinding below and beyond static propagation speed of aluminum.From the simul ation results,it is verified that the plastic deformation ... 相似文献
85.
86.
本文针对高压陡脉冲测量过程中由于对地电容引起的波形畸变,介绍了一种电感补偿方法,这种补偿回路简便、可靠,可使测量系统的方波响应得到明显的改善。 相似文献
87.
Jian-Bo Jin Zheng-Biao Ouyang Chun-Rong Qiu Xiao-Ping Liang Hui-Bo Zhang Li Hu Shi-Chang Zhang 《International Journal of Infrared and Millimeter Waves》2003,24(1):35-41
A coaxial-cavity cyclotron resonance maser (CRM) oscillator with tapered guide magnetic field is proposed. It is shown that the transmission quality can be improved by tapering the guide magnetic field. Simulation indicates that the efficiency of a millimeter-wave gyrotron oscillator may be reached up to 38.7% by optimizing the tapered magnetic field. 相似文献
88.
A finite volume solver for the 2D depth‐integrated harmonic hyperbolic formulation of the mild‐slope equation for wave propagation is presented and discussed. The solver is implemented on unstructured triangular meshes and the solution methodology is based upon a Godunov‐type second‐order finite volume scheme, whereby the numerical fluxes are computed using Roe's flux function. The eigensystem of the mild‐slope equations is derived and used for the construction of Roe's matrix. A formulation that updates the unknown variables in time implicitly is presented, which produces a more accurate and reliable scheme than hitherto available. Boundary conditions for different types of boundaries are also derived. The agreement of the computed results with analytical results for a range of wave propagation/transformation problems is very good, and the model is found to be virtually paraxiality‐free. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
89.
90.
This paper seeks to solve the difficult nonlinear problem in financial markets on the complex system theory and the nonlinear
dynamics principle, with the data-model-concept-practice issue-oriented reconstruction of the phase space by the high frequency
trade data. In theory, we have achieved the differentiable manifold geometry configuration, discovered the Yang-Mills functional
in financial markets, obtained a meaningful conserved quantity through corresponding space-time non-Abel localization gauge
symmetry transformation, and derived the financial solitons, which shows that there is a strict symmetry between manifold
fiber bundle and guage field in financial markets. In practical applications of financial markets, we have repeatedly carried
out experimental tests in a fluctuant evolvement, directly simulating and validating the existence of solitons by researching
the price fluctuations (society phenomena) using the same methods and criterion as in natural science and in actual trade
to test the stock Guangzhou Proprietary and the futures Fuel Oil in China. The results demonstrate that the financial solitons
discovered indicates that there is a kind of new substance and form of energy existing in financial trade markets, which likely
indicates a new science paradigm in the economy and society domains beyond physics.
相似文献