全文获取类型
收费全文 | 285篇 |
免费 | 5篇 |
国内免费 | 20篇 |
专业分类
化学 | 54篇 |
力学 | 31篇 |
数学 | 144篇 |
物理学 | 81篇 |
出版年
2024年 | 1篇 |
2023年 | 4篇 |
2022年 | 3篇 |
2021年 | 6篇 |
2020年 | 8篇 |
2019年 | 9篇 |
2018年 | 6篇 |
2017年 | 7篇 |
2016年 | 12篇 |
2015年 | 4篇 |
2014年 | 15篇 |
2013年 | 26篇 |
2012年 | 26篇 |
2011年 | 13篇 |
2010年 | 12篇 |
2009年 | 13篇 |
2008年 | 16篇 |
2007年 | 19篇 |
2006年 | 11篇 |
2005年 | 16篇 |
2004年 | 6篇 |
2003年 | 11篇 |
2002年 | 12篇 |
2001年 | 3篇 |
2000年 | 5篇 |
1999年 | 4篇 |
1998年 | 4篇 |
1997年 | 8篇 |
1996年 | 3篇 |
1995年 | 6篇 |
1994年 | 6篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 3篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
排序方式: 共有310条查询结果,搜索用时 296 毫秒
141.
超导故障限流器的结构及特点 总被引:4,自引:0,他引:4
综述了超导故障限流器 (SCFCL)的研究现状 ,主要介绍了各种样机的结构 ,分析了它们的工作原理及各自的特点 相似文献
142.
143.
Composite patches are widely used to repair damaged metal structures, especially in aerospace industry. Perfect patch and bonding are necessary to achieve an effective repair. Various thermographic methods such as step heating thermography are commonly applied to inspect repaired structures. Since accurate determination of defect features are admirable, some techniques are used to process the thermal films. In this study, three common post processing techniques of thermography (namely, principle component analysis (PCA), pulse phase thermography (PPT) and thermal signal reconstruction (TSR)) have been utilized to inspect an aluminum plate repaired with carbon/epoxy patches. Several delaminations with various sizes and locations along with some disbond defects were artificially embedded in five samples of composite patches to experimentally investigate the performance of the three techniques for post-processing of the step heating thermography data. Furthermore, the outputs of the mentioned processing techniques were quantitatively compared to find the most effective one. Based on the comparison results, it was demonstrated that, TSR outputs leads to the more accurate defect sizing. 相似文献
144.
基于GM(1,1)与主成分回归的海南GDP预测及其影响因素分析 总被引:1,自引:0,他引:1
以海南省年度GDP为衡量经济增长指标变量,以旅游业总收入、农林牧渔业增加值、建筑业增加值、固定资产投资总额、社会消费品零售总额及对外贸易进出口总额六个指标作为影响因素,采用多个标准对1987-2014年数据进行筛选,建立GM(1,1)模型对海南GDP及其影响因素进行5年预测,来分析海南经济结构变动趋势.利用灰色关联分析定性分析了六个行业对GDP的影响程度;从定量分析角度,利用线性主成分回归模型和对数主成分回归模型分别对海南GDP进行边际、弹性分析.发挥了灰色系统科学理论和计量经济模型各自长处,为建设海南国际旅游岛相关政策的制定提供参考. 相似文献
145.
由渗流微分方程定解问题,利用格林互易定理导出了网格压力对孔隙度的敏感系数,再由Peaceman方程给出了井底压力对孔隙度的敏感系数.借助三维不均匀非稳定渗流场的压强数值解计算了井底压力对孔隙度的敏感系数,并用直接求解敏感系数的方法进行了验证. 相似文献
146.
许金泉 《高校应用数学学报(A辑)》2001,16(3):283-289
本文利用山路引理和集中紧原理研究无界域上具有Sobolev临界指数的一类拟线性椭圆型方程的非平凡解的存在性。 相似文献
147.
废水中的阴离子表面活性剂的测定 总被引:15,自引:0,他引:15
十六烷基三甲基溴化铵 ( CTMAB)、溴甲酚紫 ( BCP)和阴离子表面活性剂三者在 p H 7.0 0的条件下可形成有色离子缔合物 ,据此建立了 CTMAB- BCP分光光度法测定阴离子表面活性剂的方法。在 75μg CTMAB存在下 ,十二烷基硫酸钠 ( SDS)在 0~ 5 0 μg范围内符合比耳定律 ,其表观摩尔吸光系数是 2 .74× 1 0 4 L· mol- 1·cm- 1,并用标准加入法和主成分回归法不分离干扰可直接测定。应用此方法测定了河水、池塘水和生活污水中的阴离子表面活性剂 (以 SDS计 )并与亚甲蓝法进行比较 ,结果满意 相似文献
148.
In this paper, we mainly discuss the infinite loss of regularity and μ-loss for a σ-evolution type model with oscillating in time coefficients. On the one hand, an explicit counter-example has been constructed in the frequency space to show the precise infinite loss of regularity. On the other hand, due to the finite propagation speed property for σ∈(0,1], we construct the counter-example of a sequence of solutions in R by applying state of art techniques. 相似文献
149.
J.W.C. Dunlop F.D. Fischer P. Fratzl 《Journal of the mechanics and physics of solids》2010,58(8):1073-1087
It is known that cells proliferate and produce extracellular matrix in response to biochemical and mechanical stimuli. Constitutive models considering these phenomena are needed to quantitatively describe the process of tissue growth in the context of tissue engineering and regenerative medicine. In this paper we re-examine the theoretical framework provided by Ambrosi and Guana (2007) and Ambrosi and Guillou (2007). We show how a volumetric growth rate term can be obtained (both in a large and small strain setting), which is consistent with the laws of thermodynamics and then apply the model to a simple geometry of tissue growth within a circular pore. The model, despite its simplicity, is comparable with experimental measurements of tissue growth and highlights the contribution of the mechanical stresses produced during tissue growth on the growth rate itself. 相似文献
150.
Highly ordered pyrolytic graphite was exposed to radio-frequency methane plasma to produce a hydrogen-terminated carbon surface. The effects of treatment parameters, namely exposure time, applied power and methane pressure, upon the treated surfaces’ chemical and morphological properties were systematically investigated. Scanning tunnelling microscopy measurements showed growth features on the plasma treated surface, the coverage of which was shown to increase with plasma exposure time or applied plasma power and decrease with gas pressure. Analyses of post-treated surface structures (via static secondary ion mass spectrometry with the aid of principle component analysis) showed an increase in surface hydrogen with plasma exposure time, applied plasma power and decreasing gas pressure. The results of these analyses were further supported by elastic recoil detection analysis measurements, which showed similar trends for the experimental parameters on the resultant surface hydrogen content. 相似文献