全文获取类型
收费全文 | 1393篇 |
免费 | 49篇 |
国内免费 | 1篇 |
专业分类
化学 | 892篇 |
晶体学 | 8篇 |
力学 | 43篇 |
数学 | 141篇 |
物理学 | 359篇 |
出版年
2022年 | 9篇 |
2021年 | 13篇 |
2020年 | 16篇 |
2019年 | 21篇 |
2017年 | 10篇 |
2016年 | 30篇 |
2015年 | 25篇 |
2014年 | 36篇 |
2013年 | 58篇 |
2012年 | 57篇 |
2011年 | 73篇 |
2010年 | 33篇 |
2009年 | 31篇 |
2008年 | 64篇 |
2007年 | 59篇 |
2006年 | 67篇 |
2005年 | 60篇 |
2004年 | 58篇 |
2003年 | 47篇 |
2002年 | 54篇 |
2001年 | 35篇 |
2000年 | 38篇 |
1999年 | 21篇 |
1997年 | 12篇 |
1996年 | 17篇 |
1995年 | 20篇 |
1994年 | 19篇 |
1993年 | 17篇 |
1992年 | 17篇 |
1990年 | 20篇 |
1989年 | 16篇 |
1988年 | 14篇 |
1987年 | 15篇 |
1986年 | 22篇 |
1985年 | 24篇 |
1984年 | 21篇 |
1983年 | 13篇 |
1982年 | 14篇 |
1981年 | 24篇 |
1980年 | 9篇 |
1979年 | 17篇 |
1978年 | 11篇 |
1977年 | 14篇 |
1976年 | 15篇 |
1975年 | 21篇 |
1974年 | 23篇 |
1973年 | 16篇 |
1972年 | 16篇 |
1967年 | 9篇 |
1966年 | 8篇 |
排序方式: 共有1443条查询结果,搜索用时 31 毫秒
61.
62.
63.
64.
65.
66.
67.
Environmental Fenton chemistry has been poorly constrained within the marine environment at a multi-component level. A simple, unique, reconfiguration of a flow-injection analytical system combined with luminol chemiluminescence allows quasi-simultaneously the measurement, using a single load-inject valve and a single photon multiplier tube, of reduced iron, Fe(II), and hydrogen peroxide. The system enables rapid, every 22 s, measurements with good accuracy at environmentally relevant concentrations, less than 5% relative standard deviations on both a 5 nM Fe(II) standard and a 60 nM hydrogen peroxide standard. Limits of detection were as low as 40 pM Fe(II) and 100 pM hydrogen peroxide. The system showed excellent capability by measuring from within an organic rich seawater the photochemically induced production of Fe(II) and hydrogen peroxide and their subsequent cycling and Fenton like interactions. 相似文献
68.
Hans Eliot Edling Matthew Vincent Herv Marand Samantha J. Talley Kevin Barr Robert B. Moore S. Richard Turner 《Journal of Polymer Science.Polymer Physics》2019,57(15):973-980
Structurally rigid copolyester thermoplastics were synthesized from 1,4‐cyclohexanedimethanol and the diesters dimethyl biphenyl‐4,4′‐dicarboxylate and dimethyl 2,6‐naphthalenedicarboxylate (DMN) via conventional melt transesterification. Conventional differential scanning calorimetry (CDSC) showed all compositions to exhibit multiple endotherms upon heating. Wide‐angle X‐ray diffraction analysis showed copolyester compositions to exhibit the crystalline structure of either the homopolyester Poly(1,4‐cyclohexylenedimethylene 2,6‐naphthalate) (PCN) or the homopolyester Poly(1,4‐cyclohexylenedimethylene 4,4′‐bibenzoate) (PCB), but not both simultaneously. Further thermal analysis using CDSC and fast DSC investigated the origin of the multiple endotherm behavior. While three endotherms are observed for low heating rates, the upper two endotherms appear to merge at heating rates about 1–5 °C s?1 and a single endotherm remains above heating rates about 10–50 °C s?1. While the behavior of the upper two endotherms is undeniably consistent with the mechanism of melting–recrystallization–remelting (MRR), we suggest that the low endotherm is likely associated with the melting of constrained secondary crystals, although MRR effects cannot be ruled out. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 973–980 相似文献
69.
Rob Turner Sean Robert Wevrett Suzanne Edmunds Marc Brown Robert Atkinson Tim Shea 《Biomedical chromatography : BMC》2019,33(8)
The aim of this investigation was to develop receiver and extraction fluids, and subsequently validate an analytical method to quantify the permeation and penetration of flurbiprofen into human pharynx tissue using a Franz diffusion cell. The solubility and stability of flurbiprofen in a suitable receiver fluid, and a suitable extraction method and fluid to recover and quantitate flurbiprofen from human pharynx tissue, were investigated using high‐performance liquid chromatography (HPLC). The potential interference of human pharynx tissue in the receiver fluid was also investigated. The HPLC analytical method was successfully validated according to current guidelines. The final receiver fluid demonstrated sufficient solubility and stability, and the extraction method and fluid resulted in >95% recovery of flurbiprofen following exposure to human pharynx tissue. The lower limit of quantitation of flurbiprofen was 0.045 μg/mL in both the receiver and extraction fluids. There was no interference of the human pharynx tissue with the HPLC method. This investigation validated an analytical method for quantitating flurbiprofen, and determined a suitable receiver fluid and extraction method and fluid, which can be used to investigate the permeation and penetration of flurbiprofen through human pharynx tissue using the Franz diffusion cell method. 相似文献
70.
Numerical Algorithms - An inverse problem to identify parameters for the single-term (and multi-term) fractional-order system of an outbreak of dengue fever is considered. Firstly, we propose a... 相似文献