全文获取类型
收费全文 | 4948篇 |
免费 | 482篇 |
国内免费 | 584篇 |
专业分类
化学 | 1624篇 |
晶体学 | 41篇 |
力学 | 1342篇 |
综合类 | 91篇 |
数学 | 1224篇 |
物理学 | 1692篇 |
出版年
2024年 | 5篇 |
2023年 | 36篇 |
2022年 | 91篇 |
2021年 | 160篇 |
2020年 | 163篇 |
2019年 | 130篇 |
2018年 | 147篇 |
2017年 | 224篇 |
2016年 | 336篇 |
2015年 | 229篇 |
2014年 | 244篇 |
2013年 | 360篇 |
2012年 | 258篇 |
2011年 | 284篇 |
2010年 | 247篇 |
2009年 | 309篇 |
2008年 | 283篇 |
2007年 | 286篇 |
2006年 | 276篇 |
2005年 | 238篇 |
2004年 | 245篇 |
2003年 | 185篇 |
2002年 | 167篇 |
2001年 | 163篇 |
2000年 | 114篇 |
1999年 | 119篇 |
1998年 | 103篇 |
1997年 | 91篇 |
1996年 | 68篇 |
1995年 | 79篇 |
1994年 | 72篇 |
1993年 | 37篇 |
1992年 | 31篇 |
1991年 | 28篇 |
1990年 | 26篇 |
1989年 | 18篇 |
1988年 | 25篇 |
1987年 | 20篇 |
1986年 | 19篇 |
1985年 | 18篇 |
1984年 | 14篇 |
1982年 | 15篇 |
1981年 | 4篇 |
1980年 | 7篇 |
1979年 | 11篇 |
1978年 | 8篇 |
1977年 | 4篇 |
1974年 | 4篇 |
1971年 | 2篇 |
1957年 | 3篇 |
排序方式: 共有6014条查询结果,搜索用时 31 毫秒
71.
Most previous investigations on interference effects of tall buildings under wind actions focused on the wind induced interference effects between two buildings,and the interference effects of three or more buildings have seldom been studied so far due to the huge workload involved in experiments and data processing.In this paper,mean and dynamic force/response interference effects and peak wind pressure interference effects of two and three tall buildings,especially the three-building configuration,are investigated through a series of wind tunnel tests on typical tall building models using high frequency force balance technique and wind pressure measurements.Furthermore,the present paper focuses on the effects of parameters,including breadth ratio and height ratio of the buildings and terrain category,on the interference factors and derives relevant regression results for the interference factors. 相似文献
72.
73.
74.
研究条形平板中平行于上下边界的单一裂纹的识别问题。给出了当一声波入射这一条形平板时,裂纹参数与反射、透射系数之间的关系式,并应用遗传算法对裂纹进行了定量识别。计算结果表明本文给出的方法具有较好的识别精度。 相似文献
75.
平面八节点四边形理性元 总被引:2,自引:0,他引:2
推导平面八节点四边形理性有限元列式,采用具有直到四次多项式的平面问题的微分方程的解作为插值函数,算例结果表明平面八节点四边形理性有限元的有效性。 相似文献
76.
77.
Diffuse mode bifurcation of soil under plane-strain compression test is shown, by means of an image analysis based on group-theoretic bifurcation theory, to trigger convection-like shear and to precede shear band formation. First digital photos of Toyoura sand specimens are processed by PIV (particle image velocimetry) to gather digitized images of deformation. Next bifurcation from a uniform state is detected by expanding these images into the double Fourier series and finding a predominant harmonic diffuse bifurcation mode based on that theory. This harmonic bifurcation mode, which is the mixture of a few harmonic functions, expresses complex convection-like shear. Last bifurcation from a non-uniform state is detected by decomposing each image into a few images with different symmetries to extract non-harmonic diffuse bifurcation modes. Diffuse modes of bifurcation, which hitherto were hidden behind predominant uniform compressive deformation, have thus been made transparent by virtue of the group-theoretic image analysis proposed. A possible course of deformation suggested herein is the evolution of diffuse mode bifurcation with a convection-like bifurcation mode breaking uniformity and symmetry, followed by the formation of shear bands through localization. 相似文献
78.
基于界面端奇异性理论的单纤维拔出试验的试件设计 总被引:1,自引:0,他引:1
在单纤维拔出试验中,由于试件的界面端存在应力奇异性,这使试验所得到的界面剪切强度数据失去合理性[1]。但从文献[1]关于微珠脱粘试验研究的结论中可以发现当基体的楔形角小于某临界角度后,微珠试件界面端应力奇异性几乎消失。由此启发我们设计出一种楔形角小于该纤维/基体系统临界角的锥面的拔出试件,这样即可以防止出现传统拔出试件在界面端的强应力奇异性,又可以避免微珠脱粘试验自身的缺陷。界面端具有任意楔形角的轴对称模型被用于分析和确定纤维/基体系统的临界角,对方程进行渐近展开和分离变量处理,根据边界条件可以得到关于特征值λ的特征方程,针对确定的纤维/基体系统可以得到特征值和楔形角的关系曲线,我们把应力奇异性指数等于-0.005时所对应的楔形角定义为临界角,以及根据临界角设计锥面拔出试件的方法。 相似文献
79.
已有的“从自由试验提取约束结构模态”的动柔度法,仅适用于刚性支承情况.在工程中,弹性支承状态是常见的,为此,建立了这一情况下的提取方法.该方法具有普遍性,因为当支承刚度很大时,可得到刚性支承下的结果;当支承刚度很小时,便可获得工程中用橡皮绳悬吊结构后所测得的自由-自由试验模态.总之,当支承刚度为任何值时,用此方法都能提取到相应约束结构的满意试验模态参数.表明该算法是非常稳定的,对于工程应用至关重要. 相似文献
80.
The modified Blalock-Taussig shunt is a connection created between the systemic and pulmonary arterial circulations to improve pulmonary perfusion in children with congenital heart diseases. Survival of these patients is critically dependent on blood flow distribution between the pulmonary and systemic circulations, that in turn depends upon the fluid dynamic behaviour of the shunt. Computational fluid dynamics, structural analyses as well as in vitro experiments were carried out to derive a quantitative relationship between the shunt flow and the corresponding pressure drop. While computational fluid dynamics simulations were based on the assumption of rigid wall for the shunt and the arteries, proper distensible conduits were used in the in vitro study and the structural analysis of the anastomosis deformation. The results indicated that the internal pressure combined with wall distensibility modifies the cross-sectional area of the distal anastomosis (between the shunt and the pulmonary artery). This fact affects the pressure drop across the shunt, especially at low pressures. Based on the results from the computational analyses and the in vitro experiments, a relationship between pressure drop and flow in the shunt was obtained, which matches data from clinical measurements. 相似文献