全文获取类型
收费全文 | 1961篇 |
免费 | 209篇 |
国内免费 | 268篇 |
专业分类
化学 | 549篇 |
晶体学 | 10篇 |
力学 | 80篇 |
综合类 | 14篇 |
数学 | 65篇 |
物理学 | 1720篇 |
出版年
2024年 | 2篇 |
2023年 | 23篇 |
2022年 | 99篇 |
2021年 | 73篇 |
2020年 | 69篇 |
2019年 | 61篇 |
2018年 | 60篇 |
2017年 | 61篇 |
2016年 | 92篇 |
2015年 | 67篇 |
2014年 | 60篇 |
2013年 | 150篇 |
2012年 | 103篇 |
2011年 | 173篇 |
2010年 | 137篇 |
2009年 | 167篇 |
2008年 | 135篇 |
2007年 | 118篇 |
2006年 | 105篇 |
2005年 | 99篇 |
2004年 | 72篇 |
2003年 | 82篇 |
2002年 | 75篇 |
2001年 | 69篇 |
2000年 | 48篇 |
1999年 | 38篇 |
1998年 | 36篇 |
1997年 | 16篇 |
1996年 | 22篇 |
1995年 | 16篇 |
1994年 | 10篇 |
1993年 | 8篇 |
1992年 | 12篇 |
1991年 | 15篇 |
1990年 | 9篇 |
1989年 | 7篇 |
1988年 | 4篇 |
1987年 | 6篇 |
1986年 | 10篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1982年 | 4篇 |
1981年 | 5篇 |
1980年 | 3篇 |
1979年 | 6篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1975年 | 1篇 |
排序方式: 共有2438条查询结果,搜索用时 15 毫秒
11.
12.
《Journal of separation science》2003,26(5):402-408
When nitrated polynuclear aromatic hydrocarbons (NPAH) were recognised as long‐term toxic compounds and were also identified in several anthropogenic emissions and among the by‐products of photochemical smog they became objects of investigation in ambient air in both polluted and clean environments. In Italy the first investigations focussing on atmospheric NPAH were performed in the early eighties and encompassed both the canyon streets and dwelling areas of Rome. Because NPAH were indicated as markers of vehicle emission, new investigations were performed in other cities and also in rural and (nominally) unpolluted locations. In general, the first measurements of NPAH were episodic and could not be assumed to be strictly representative of the sites investigated. In contrast, nowadays consistent data bases on NPAH have been built up and are discussed in the technical literature, so that both neat concentrations and the yearly timed variation of the most important NPAH congeners have been measured in Italian air. Although concentrations of NPAH in air are usually much lower than those of PAH, owing to their very high potency in inducing mutations and tumours NPAH are regarded as having an important health impact on populations living in Italian urban areas. In this regard the genotoxicity of atmospheric aerosols is partly associated with nitrofluoranthenes and nitropyrenes whereas nitronaphthalenes and methylnitronaphthalenes seem to contribute to that of the gaseous organic fraction. Several civic and regional administrations are introducing control of atmospheric NPAH among ways of improving air quality in cities. 相似文献
13.
14.
15.
The K+−nucleus cross sections have been calculated in relativistic non-linear models taking into account the in-medium modifications of nucleons and mesons properties. More precisely, we have taken into account both the dressing of the nucleon effective mass by the scalar nuclear field in the target and the coupling of the mesons exchanged between the K+ and the nucleons to the polarization of the medium. First, using the most recent relativistic non-linear models, the in-medium σ, ω and ρ meson masses have been obtained in the nuclear matter rest frame. The influence of the non-linear contributions on the K+−nucleus cross sections has then been studied. Finally, we have compared our results with the experimental data. 相似文献
16.
17.
18.
Summary The relative X-ray fluorescence (XRF) intensities for annular source and various annular specimen are measured with a Ge-Li
detection system and calculated by the Monte Carlo numerical techniques (MCNT).Kα X-ray intensities of annular specimens with different radii prepared from a pure-molybdenum foil are measured and it is
seen that the measured values are in good agreement with the values calculated by MCNT. The variation of the fluorescence
intensity due to the collimator radius is also studied. The differences between the MCNT and experimental results are discussed
in terms of the possible sources of errors. 相似文献
20.
U. Brosa 《Journal of statistical physics》1989,55(5-6):1303-1312
It is shown that pipe-flow turbulence consists of transients. The fractal dimensions of the dynamical process are thus all zero. Nevertheless, this is compatible with Grassberger-Procaccia analyses suggesting the existence of a high-dimensional strange attractor. The usefulness of the Grassberger-Procaccia method to detect the aging of transients is demonstrated. 相似文献