全文获取类型
收费全文 | 1008篇 |
免费 | 78篇 |
国内免费 | 30篇 |
专业分类
化学 | 320篇 |
晶体学 | 2篇 |
力学 | 80篇 |
综合类 | 75篇 |
数学 | 205篇 |
物理学 | 434篇 |
出版年
2024年 | 1篇 |
2023年 | 5篇 |
2022年 | 38篇 |
2021年 | 32篇 |
2020年 | 26篇 |
2019年 | 27篇 |
2018年 | 28篇 |
2017年 | 66篇 |
2016年 | 62篇 |
2015年 | 57篇 |
2014年 | 61篇 |
2013年 | 82篇 |
2012年 | 46篇 |
2011年 | 48篇 |
2010年 | 42篇 |
2009年 | 43篇 |
2008年 | 39篇 |
2007年 | 54篇 |
2006年 | 31篇 |
2005年 | 39篇 |
2004年 | 48篇 |
2003年 | 35篇 |
2002年 | 27篇 |
2001年 | 23篇 |
2000年 | 19篇 |
1999年 | 23篇 |
1998年 | 15篇 |
1997年 | 16篇 |
1996年 | 16篇 |
1995年 | 11篇 |
1994年 | 13篇 |
1993年 | 12篇 |
1992年 | 6篇 |
1991年 | 4篇 |
1990年 | 1篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1986年 | 7篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1980年 | 2篇 |
1978年 | 2篇 |
1969年 | 1篇 |
排序方式: 共有1116条查询结果,搜索用时 31 毫秒
991.
介绍一个实用的舰船尾部振动水弹性分析软件系统,该系统基于流固耦合理论,针对舰船尾部结构特征,可以准确方便地预报出舰船尾部振动特性。系统还配有较强的后处理图形生成模块,可以形象逼真地绘制出振型图。 相似文献
992.
气—固流化床反应器内双流体力学模型及其验证:Ⅳ.单组分两维射流床内气泡特性 总被引:1,自引:0,他引:1
模拟了不同操作条件下,单组分两维射流床内射流崩塌后所形成气泡的形状、运动机理、初始尺寸和上升速度。集合前文(Ⅰ、Ⅱ和Ⅲ)研究结果表明,在湍流两相流理论基础上建立的“气-固流化床反应器内双流体力学模型”可以很好地分析气固射流床内流体动力学特性,诸如:基本流场变量(气、固相速度场、压力场和空隙率)瞬态变化情况、射流特性(射流发展、射流穿透深度确定方法、射流区气体速度分布和操作条件对射流穿透深度、射流频率的影响等)、时均空隙率分布、时均轴向气体速度分布和气泡特性。由此可见,该方法和思路可以为灰熔聚流化床粉煤气化工艺和其他与流态化技术相关的设计提供必要的信息和有益的建议 相似文献
993.
计算多层膜组分和厚度的软件FPMULTI及其应用 总被引:2,自引:0,他引:2
本文简述了可用于多层镀层和多层薄膜成分和厚度同时分析的计算机软件FPMULTI的主要特点。这个基于基本参数法的计算机软件可以分析多至10层,最多含25个元素的各类试样。所需的校正标样可以是纯元素或多元素的薄膜标样,亦可以是纯元素或多元素的块样。本文的研究表明,用FPMULTI的分析结果明显优于检量线法,体现了基本参数法的优点。 相似文献
994.
静态应变数据采集器的新软件 总被引:2,自引:0,他引:2
本文介绍了静态应变数据采集器应用软件的编制情况,通过改进软件界面和采样模式及数据图表处理等方面的功能,使应用软件更符合各类工程测试的实际需求。 相似文献
995.
徐仁佐 《武汉大学学报(理学版)》2000,46(1):61-62
在软件测试阶段,常使用的排错方法包括排错测试和操作概图测试,但它们采取的都是随机测试的策略.在对它们进行研究的基础上提出一种新的测试方法基于软件系统中使用的知识以及对相关知识的使用方式的软件测试方法.基于软件知识的测试方法可以应用于软件的可靠性稳定增长测试与软件安全性测试,也可以应用于对面向对象软件的测试,以及应用于采用组件重用策略的软件可重用技术的软件系统测试。 相似文献
996.
K. A. Abd El-Gawwad D. A. Crolla A. M. A. Soliman F. M. El-Sayed 《Journal of Terramechanics》1999,36(1):25
The problem of off-road vehicle tyre-terrain interaction is that it is difficult to model accurately. For an off-road vehicle over medium to firm terrain, the tyre load may be entirely supported by the tips of the lugs, or with a minimum carcass contact with the terrain. In this case, the effect of the lugs should be taken into consideration. The forces at the interface between lugged tyre and the soil, including normal and shear stresses, are discussed in this paper. The multi-spoke tyre model was developed to study the effect of tyre lugs on the forces between tyre and terrain and it has been extended to predict the tyre forces and moments in the case of combined lateral and longitudinal slip for a cambered tyre. The influence of slip angle, camber angle and soil hardness on off-road tyre performance has been investigated. A computer program was developed using MATLAB software. The results were derived as tyre forces and moments in the three directions along the tyre contact length. A comparison between the results of the multi-spoke tyre model of a smooth off-road tyre and an off-road tyre with straight lugs, in the cambered case, has been made. The results indicated that slip angle, camber angle and soil characteristics have a strong effect on off-road tyre performance. The modified mathematical model results help the off-road tyre engineering designers to predict accurate values of tyre forces and moments in this complex case. 相似文献
997.
把数字图像技术引入近代物理实验 总被引:2,自引:1,他引:1
数字图像技术实验近代物理实验课程应用技术部分的选题之一,使用数码相机获取图像,使用Photoshop软件处理图像,使用打印机输出照片,知识新颖,教学形活跃,有助于学生能力和素质的培养。 相似文献
998.
Ilana Arnon Pearla Nesher Renata Nirenburg 《International Journal of Computers for Mathematical Learning》2001,6(2):167-214
The concept of equivalence class plays a significant role in the structure of Rational Numbers. Piaget taught that in order
to help elementary school children develop mathematical concepts, concrete objects and concrete reflection-enhancing-activities
are needed. The “Shemesh” software was specially designed for learning equivalence-classes of fractions. The software offers
concrete representations of such classes, as well as activities which cannot be constructed without a computer. In a discrete
Cartesian system students construct points on the grid and learn to identify each such point as a fraction-numeral (a denominator-numerator
pair). The children then learn to construct sets of such points, all of which are located on a line through the origin point.
They learn to identify the line with the set of its constituent equivalent fractions. Subsequently, they investigate other
phenomena and constructions in such systems, developing these constructions into additional fraction concepts. These concrete
constructions can be used in solving traditional fraction problems as well as in broadening the scope of fraction meaning.
Fifth-graders who used “Shemesh” in their learning activities were clinically interviewed several months after the learning
sessions ended. These interviews revealed evidence indicating initial actual development of the desired mathematical concepts.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
999.
1000.
When there is a need to accurately characterize optical waveforms and, it is not surprising that some of the best, albeit only recently established, techniques to do this rely on all‐optical phenomena. Some basic reasons why all‐optical sampling holds great promise as a very useful tool well into the foreseeable future are that there are no ringing phenomena with associated waveform distortion as in electronic sampling due to impedance mismatch, and that the time resolution can be made extremely high (⩽ 1 ps) while yet also offering high sensitivity for e.g. eye diagram (a superposition of all ‘1’ and ‘0’ in a data sequence that is widely used in telecommunications testing) and statistical analysis. In this paper, we review recent developments in optical fiber‐based sampling of optical waveforms. In particular, we describe the state‐of‐the‐art in terms of the various performance measures as well as their trade‐offs. 相似文献