全文获取类型
收费全文 | 744篇 |
免费 | 16篇 |
国内免费 | 1篇 |
专业分类
化学 | 542篇 |
晶体学 | 7篇 |
力学 | 23篇 |
数学 | 92篇 |
物理学 | 97篇 |
出版年
2023年 | 5篇 |
2022年 | 8篇 |
2021年 | 16篇 |
2020年 | 8篇 |
2019年 | 7篇 |
2018年 | 15篇 |
2017年 | 11篇 |
2016年 | 18篇 |
2015年 | 12篇 |
2014年 | 21篇 |
2013年 | 27篇 |
2012年 | 32篇 |
2011年 | 51篇 |
2010年 | 32篇 |
2009年 | 29篇 |
2008年 | 21篇 |
2007年 | 34篇 |
2006年 | 38篇 |
2005年 | 36篇 |
2004年 | 44篇 |
2003年 | 33篇 |
2002年 | 28篇 |
2001年 | 14篇 |
2000年 | 13篇 |
1999年 | 8篇 |
1998年 | 6篇 |
1997年 | 10篇 |
1996年 | 9篇 |
1995年 | 10篇 |
1994年 | 10篇 |
1993年 | 6篇 |
1992年 | 5篇 |
1991年 | 9篇 |
1990年 | 8篇 |
1989年 | 9篇 |
1988年 | 9篇 |
1987年 | 8篇 |
1985年 | 4篇 |
1984年 | 10篇 |
1983年 | 7篇 |
1982年 | 8篇 |
1981年 | 8篇 |
1980年 | 7篇 |
1979年 | 9篇 |
1978年 | 5篇 |
1976年 | 5篇 |
1974年 | 3篇 |
1972年 | 4篇 |
1971年 | 3篇 |
1969年 | 4篇 |
排序方式: 共有761条查询结果,搜索用时 203 毫秒
61.
62.
63.
64.
A new carbon‐based mercury thin‐film electrode consisting of screen‐printed carbon on a low temperature co‐fired ceramic substrate was made. Ex‐situ mercury deposition in a potassium thiocyanate solution was used. This approach an electrode with high long‐term stability (>500 measurement cycles) and reproducibility (≤2 %) for sensitive determination of ultra trace heavy metals, using differential pulse anodic stripping voltammetry. The detection limits were 0.25, 0.08 and 5.5 ng mL?1 for Cd(II), Pb(II), and Zn(II), respectively. The method was applied to the determination of the analytes in water, wastewater, lake water, and certified reference material samples with satisfactory results. 相似文献
65.
66.
Diels-Alder Reactions with 3-Cyclopropylideneprop-1-enyl Ethyl Ether as 1,3-Diene The title compound undergoes readily Diels-Alder reactions with various dienophiles, especially with quinones. The resulting adducts constitute key intermediates in the synthesis of labdane diterpenoids. 相似文献
67.
Accelerated Projected Gradient Method for Linear Inverse Problems with Sparsity Constraints 总被引:2,自引:0,他引:2
Ingrid Daubechies Massimo Fornasier Ignace Loris 《Journal of Fourier Analysis and Applications》2008,14(5-6):764-792
Regularization of ill-posed linear inverse problems via ? 1 penalization has been proposed for cases where the solution is known to be (almost) sparse. One way to obtain the minimizer of such an ? 1 penalized functional is via an iterative soft-thresholding algorithm. We propose an alternative implementation to ? 1-constraints, using a gradient method, with projection on ? 1-balls. The corresponding algorithm uses again iterative soft-thresholding, now with a variable thresholding parameter. We also propose accelerated versions of this iterative method, using ingredients of the (linear) steepest descent method. We prove convergence in norm for one of these projected gradient methods, without and with acceleration. 相似文献
68.
69.
70.
Validation of Sun Exposure Reported Annually Against Interim Self‐report and Daily Sun Diaries 下载免费PDF全文
Laura King Fan Xiang Ashwin Swaminathan Keith Dear Simone L. Harrison Ingrid van der Mei Michael G. Kimlin Catherine D'Este Robyn M. Lucas 《Photochemistry and photobiology》2017,93(5):1294-1302
Data on personal sun exposure over a period exceeding the immediate past days or weeks are typically self‐reported in brief questionnaire items. The validity of such self‐reporting of longer term personal sun exposure, for example over a year, including detail on variation across seasons, has not previously been investigated. In a volunteer sample (n = 331) of Australian adults aged 18 years and over, we assessed the 12‐month reliability of sun exposure reported separately for each season, and its accuracy compared to a daily sun diary in the same season. Seasonal time outdoors displayed fair‐to‐good reliability between baseline and end of study (12 months), with responses showing higher agreement at lower levels of time outdoors. There was good agreement for ranking of individuals' time outdoors with the daily sun diary data, although the actual diary time outdoors was typically considerably lower than the self‐reported questionnaire data. Place of residence, education, being a smoker, day of the week (i.e. working day vs nonworking day) and working mainly outdoors were significant predictors of agreement. While participants overestimated their actual time outdoors, the self‐report questionnaire provided a valid ranking of long‐term sun exposure against others in the study that was reliable over time. 相似文献