全文获取类型
收费全文 | 18601篇 |
免费 | 1733篇 |
国内免费 | 757篇 |
专业分类
化学 | 3421篇 |
晶体学 | 86篇 |
力学 | 6838篇 |
综合类 | 166篇 |
数学 | 2766篇 |
物理学 | 4567篇 |
无线电 | 3247篇 |
出版年
2024年 | 38篇 |
2023年 | 218篇 |
2022年 | 329篇 |
2021年 | 409篇 |
2020年 | 510篇 |
2019年 | 391篇 |
2018年 | 445篇 |
2017年 | 510篇 |
2016年 | 585篇 |
2015年 | 615篇 |
2014年 | 884篇 |
2013年 | 1323篇 |
2012年 | 986篇 |
2011年 | 1202篇 |
2010年 | 837篇 |
2009年 | 1037篇 |
2008年 | 1034篇 |
2007年 | 1058篇 |
2006年 | 973篇 |
2005年 | 838篇 |
2004年 | 820篇 |
2003年 | 715篇 |
2002年 | 674篇 |
2001年 | 538篇 |
2000年 | 468篇 |
1999年 | 401篇 |
1998年 | 408篇 |
1997年 | 373篇 |
1996年 | 350篇 |
1995年 | 295篇 |
1994年 | 275篇 |
1993年 | 252篇 |
1992年 | 237篇 |
1991年 | 176篇 |
1990年 | 158篇 |
1989年 | 122篇 |
1988年 | 111篇 |
1987年 | 70篇 |
1986年 | 75篇 |
1985年 | 81篇 |
1984年 | 72篇 |
1983年 | 39篇 |
1982年 | 77篇 |
1981年 | 24篇 |
1980年 | 13篇 |
1979年 | 9篇 |
1978年 | 7篇 |
1976年 | 5篇 |
1971年 | 6篇 |
1957年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 18 毫秒
1.
2.
Cavitation erosion is caused in solids exposed to strong pressure waves developing in an adjacent fluid field. The knowledge of the transient distribution of stresses in the solid is important to understand the cause of damaging by comparisons with breaking points of the material. The modeling of this problem requires the coupling of the models for the fluid and the solid. For this purpose, we use a strategy based on the solution of coupled Riemann problems that has been originally developed for the coupling of 2 fluids. This concept is exemplified for the coupling of a linear elastic structure with an ideal gas. The coupling procedure relies on the solution of a nonlinear equation. Existence and uniqueness of the solution is proven. The coupling conditions are validated by means of quasi‐1D problems for which an explicit solution can be determined. For a more realistic scenario, a 2D application is considered where in a compressible single fluid, a hot gas bubble at low pressure collapses in a cold gas at high pressure near an adjacent structure. 相似文献
3.
An approach of dynamic mesh adaptation for simulating 3‐dimensional unsteady moving‐immersed‐boundary flows 下载免费PDF全文
In this paper, we present an approach of dynamic mesh adaptation for simulating complex 3‐dimensional incompressible moving‐boundary flows by immersed boundary methods. Tetrahedral meshes are adapted by a hierarchical refining/coarsening algorithm. Regular refinement is accomplished by dividing 1 tetrahedron into 8 subcells, and irregular refinement is only for eliminating the hanging points. Merging the 8 subcells obtained by regular refinement, the mesh is coarsened. With hierarchical refining/coarsening, mesh adaptivity can be achieved by adjusting the mesh only 1 time for each adaptation period. The level difference between 2 neighboring cells never exceeds 1, and the geometrical quality of mesh does not degrade as the level of adaptive mesh increases. A predictor‐corrector scheme is introduced to eliminate the phase lag between adapted mesh and unsteady solution. The error caused by each solution transferring from the old mesh to the new adapted one is small because most of the nodes on the 2 meshes are coincident. An immersed boundary method named local domain‐free discretization is employed to solve the flow equations. Several numerical experiments have been conducted for 3‐dimensional incompressible moving‐boundary flows. By using the present approach, the number of mesh nodes is reduced greatly while the accuracy of solution can be preserved. 相似文献
4.
随着互联网的高速发展,引发了网络流量、电信骨干网流量急速增长,使得网络容量的提升迫在眉睫。目前,100G 系统已经商用,超100G系统能够更有效地解决流量和网络带宽持续增长带来的压力,本文主要介绍新型单模光纤的特性以及探讨基于新型单模光纤的传输技术。 相似文献
5.
In the present work, the use of cylindrical turbulators in a double pipe heat exchanger has been investigated. Cylindrical fin type of turbulators has been placed circumferentially separated by 90° on the outer side of an inner pipe at a regular pitch. Experimental studies were undertaken for different air flow rates in a turbulent regime whose Reynolds number range between 2500 and 10000. Heat transfer characteristics like Nu and friction factor have been experimentally determined. Parametric studies were conducted by changing the pitch and also the orientation of the turbulators. Nu and friction factor were found to increase as the pitch is reduced. A model with alternatively changed orientation outperformed others by exhibiting highest Nu and reduced friction factor. 相似文献
6.
7.
软件集成测试技术研究 总被引:1,自引:0,他引:1
首先分析了集成测试的原理和特点,并指出了集成测试的重要性。然后结合传统软件与面向对象软件开发的方法和技术,详细介绍了传统软件的集成测试方法和策略,并深入分析了面向对象软件集成测试的原理和方法。 相似文献
8.
随着各高校校园网络规模的不断扩大和各种应用的急剧增加,各种新的网络问题也在不断出现。Sniffer是网络管理员进行网络管理的有效工具,可以有效地对网络进行实时监控,及时发现网络中存在的各种问题。本文首先介绍了Sniffer的工作原理,其次给出了实现Sniffer功能的编程流程图,并用C语言给出了编程所需的关键代码。 相似文献
9.
《Electroanalysis》2006,18(6):595-604
The following two numerical models have been applied to zinc cations electroreduction in 1 M NaClO4 water solution: a classical EE model describing the concentration of involved species in solution (semi infinitive diffusion region), an extended EE model describing both: the concentration of involved species in solution and the concentration of metallic zinc inside mercury drop (in limited area of diffusion). In the latter model the inner part of mercury drop and surrounding solution were treated as dynamic interrelated system. Both models were applied to experimental cyclic voltammetric CV data in 1 M NaClO4, the results compared and discussed. The concentration profiles of all species including metallic zinc inside mercury drop were performed. The presented integrated model is essential for theoretical and analytical aspects of the electrochemistry of mercury soluble metal cations and amalgams. 相似文献
10.