全文获取类型
收费全文 | 67143篇 |
免费 | 15364篇 |
国内免费 | 5801篇 |
专业分类
化学 | 61954篇 |
晶体学 | 724篇 |
力学 | 2661篇 |
综合类 | 404篇 |
数学 | 6086篇 |
物理学 | 16479篇 |
出版年
2024年 | 29篇 |
2023年 | 785篇 |
2022年 | 843篇 |
2021年 | 1291篇 |
2020年 | 2650篇 |
2019年 | 3868篇 |
2018年 | 2155篇 |
2017年 | 1833篇 |
2016年 | 4912篇 |
2015年 | 4989篇 |
2014年 | 5279篇 |
2013年 | 6572篇 |
2012年 | 6146篇 |
2011年 | 5529篇 |
2010年 | 5083篇 |
2009年 | 5015篇 |
2008年 | 4679篇 |
2007年 | 3973篇 |
2006年 | 3421篇 |
2005年 | 3236篇 |
2004年 | 2765篇 |
2003年 | 2165篇 |
2002年 | 1723篇 |
2001年 | 1540篇 |
2000年 | 1239篇 |
1999年 | 867篇 |
1998年 | 716篇 |
1997年 | 606篇 |
1996年 | 607篇 |
1995年 | 551篇 |
1994年 | 529篇 |
1993年 | 451篇 |
1992年 | 400篇 |
1991年 | 332篇 |
1990年 | 326篇 |
1989年 | 240篇 |
1988年 | 176篇 |
1987年 | 129篇 |
1986年 | 144篇 |
1985年 | 123篇 |
1984年 | 73篇 |
1983年 | 65篇 |
1982年 | 52篇 |
1981年 | 39篇 |
1980年 | 22篇 |
1979年 | 22篇 |
1977年 | 15篇 |
1976年 | 18篇 |
1975年 | 11篇 |
1957年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
Marija argonja Darko Mekterovi Paula
urga Jagoda Ravli‐Gulan Iva Bogdanovi Radovi Gordana
auhar 《X射线光谱测定》2021,50(1):68-79
During metal welding and cutting, large amounts of particulate matter (PM) are produced that might represent a significant health risk for the exposed workers. In the present pilot study, we performed an elemental analysis of fine PM collected in a metal workshop. Also, elemental analysis of the hair and nail samples collected from workers exposed to the workshop dust and control group was done. Concentrations of 15 elements in PM were measured with X‐Ray Fluorescence (XRF) and Particle Induced X‐ray Emission (PIXE), whereas inductively coupled plasma mass spectrometry (ICP‐MS) was used to determine 12 elements in hair and nail samples. Mean 8‐hr concentrations of PM2.5, Fe, and Mn in the vicinity of welders were up to 1803, 860, and 30 μg/m3, respectively, whereas in the nearby city, daily PM2.5 concentrations are on average 11 μg/m3. We found that several elements, especially Fe and Mn, had substantially higher concentrations in hair and nail samples of exposed workers than in the control group, which indicates the accumulation of metals in workers' tissues, although limit values were not exceeded. 相似文献
2.
3.
Acta Mathematicae Applicatae Sinica, English Series - So far there have been few results presented on the exponential stability for time-changed stochastic differential equations. The main aim of... 相似文献
4.
In this article a coupled version of the improved divergence‐free‐condition compensated method will be proposed to simulate time‐varying geometries by direct forcing immersed boundary method. The proposed method can be seen as a quasi‐multi‐moment framework due to the fact that the momentum equations are discretized by both cell‐centered and cell‐face velocity. For simulating time‐varying geometries, a semi‐implicit iterative method is proposed for calculating the direct forcing terms. Treatments for suppressing spurious force oscillations, calculating drag/lift forces, and evaluating velocity and pressure for freshly cells will also be addressed. In order to show the applicability and accuracy, analytical as well as benchmark problems will be investigated by the present framework and compared with other numerical and experimental results. 相似文献
5.
Liu Zhu Sun Wen-Yang Fan Xiao-Gang Wang Dong Ye Liu 《International Journal of Theoretical Physics》2021,60(7):2412-2422
International Journal of Theoretical Physics - In this paper, we investigate Einstein-Podolsky-Rosen steering, Bell non-locality, first-order coherence and concurrence in the spin- $\frac {1}{2}$... 相似文献
6.
Potential Analysis - The purpose of this paper is to provide necessary and sufficient conditions of the boundedness for singular integrals on the local Hardy space and its dual. Particularly the... 相似文献
7.
Nonlinear Dynamics - The modal truncation is usually used in the dynamic response analysis of flexible multibody systems, in which, appropriate selection of modal shapes is very critical to achieve... 相似文献
8.
This study is to numerically test the interfacial instability of ferrofluid flow under the presence of a vacuum magnetic field. The ferrofluid parabolized stability equations(PSEs) are derived from the ferrofluid stability equations and the Rosensweig equations, and the characteristic values of the ferrofluid PSEs are given to describe the ellipticity of ferrofluid flow. Three numerical models representing specific cases considering with/without a vacuum magnetic field or viscosity are created to mathematically examine the interfacial instability by the computation of characteristic values. Numerical investigation shows strong dependence of the basic characteristic of ferrofluid Rayleigh-Taylor instability(RTI) on viscosity of ferrofluid and independence of the vacuum magnetic field.For the shock wave striking helium bubble, the magnetic field is not able to trigger the symmetry breaking of bubble but change the speed of the bubble movement. In the process of droplet formation from a submerged orifice, the collision between the droplet and the liquid surface causes symmetry breaking. Both the viscosity and the magnetic field exacerbate symmetry breaking. The computational results agree with the published experimental results. 相似文献
9.
Song Zi-Long Zhu Yun Liu Jing-Rui Guo Shu-Ke Gu Yu-Cheng Han Xinya Dong Hong-Qiang Sun Qi Zhang Wei-Hua Zhang Ming-Zhi 《Molecular diversity》2021,25(1):205-221
Molecular Diversity - Based on the strategy of diversity-oriented synthesis and the structures of natural product pimprinine and streptochlorin, two series of novel pimprinine derivatives... 相似文献
10.
Nonlinear Dynamics - The paper studies the stability and control of radial deployment of an electric solar wind sail with the consideration of high-order modes of elastic tethers. The electric... 相似文献