全文获取类型
收费全文 | 299篇 |
免费 | 4篇 |
国内免费 | 4篇 |
专业分类
化学 | 131篇 |
晶体学 | 1篇 |
力学 | 19篇 |
数学 | 52篇 |
物理学 | 104篇 |
出版年
2023年 | 2篇 |
2022年 | 2篇 |
2021年 | 2篇 |
2020年 | 3篇 |
2019年 | 2篇 |
2018年 | 2篇 |
2016年 | 2篇 |
2014年 | 12篇 |
2013年 | 11篇 |
2012年 | 13篇 |
2011年 | 23篇 |
2010年 | 6篇 |
2009年 | 9篇 |
2008年 | 13篇 |
2007年 | 10篇 |
2006年 | 7篇 |
2005年 | 9篇 |
2004年 | 12篇 |
2003年 | 7篇 |
2002年 | 5篇 |
2001年 | 10篇 |
2000年 | 10篇 |
1999年 | 5篇 |
1998年 | 9篇 |
1997年 | 4篇 |
1996年 | 3篇 |
1995年 | 3篇 |
1994年 | 5篇 |
1993年 | 11篇 |
1992年 | 10篇 |
1991年 | 6篇 |
1990年 | 8篇 |
1989年 | 6篇 |
1988年 | 6篇 |
1987年 | 4篇 |
1986年 | 5篇 |
1985年 | 4篇 |
1984年 | 3篇 |
1981年 | 2篇 |
1972年 | 2篇 |
1933年 | 2篇 |
1929年 | 4篇 |
1925年 | 3篇 |
1924年 | 4篇 |
1918年 | 2篇 |
1899年 | 2篇 |
1882年 | 1篇 |
1879年 | 3篇 |
1874年 | 2篇 |
1867年 | 1篇 |
排序方式: 共有307条查询结果,搜索用时 15 毫秒
1.
Klaus Thomsen 《Transactions of the American Mathematical Society》2004,356(9):3557-3619
The structure of a sofic shift space is investigated, and Krieger's embedding theorem and Boyle's factor theorem are generalized to a large class of sofic shifts.
2.
3.
A WDM compatible Edge-to-Edge Self-Routed optical packet switched network that simplifies the optical processing is proposed. The system employs all-optical packet label generation and recognition using coded superstructured Fiber Bragg gratings. 相似文献
4.
5.
Determination of fenpyroximate in apples by supercritical fluid extraction and packed capillary liquid chromatography with UV detection 总被引:6,自引:0,他引:6
A method using off-line supercritical fluid extraction (SFE) and micro liquid chromatography (μLC) with UV detection at 260 nm, was developed for selective determination of fenpyroximate in apple samples. The packed capillary liquid chromatography method utilises 20 μl injection volumes with on-column focusing. A 350×0.32 mm capillary column packed with Kromasil 100-C18 of 5 μm particle size was used with a mobile phase of acetonitrile–10 mM ammonium acetate (85:15, v/v) at a flow of 5 μl/min. A two-step SFE procedure was used to extract fenpyroximate selectively in 2 g apple samples, with Hydromatrix (HMX) added as a water absorbent at a 1:1 (w:w) ratio. Fenpyroximate was extracted at 200 bar and 90°C for 15 min using carbon dioxide at a flow of 2 ml/min, and solvent trapping collection in 10 ml acetonitrile. The volume of the acetonitrile extract was reduced by evaporation and water was added to a final composition of acetonitrile–water (40:60, v/v). The resulting 2.0 ml solution was filtered using a 0.45 μm poly(vinylidene difluoride) syringe filter before μLC analysis. Validation of the method was accomplished with apple samples spiked with fenpyroximate, covering the range of 0.1 to 1.0 μg/kg. The within-day and between-day repeatabilities were in the range 4–18% relative standard deviation. Accuracy, measured as recovery, was found to be approximately 60%. Apple samples from a field treated with fenpyroximate were analysed. None of the samples contained fenpyroximate above the quantification level. 相似文献
6.
S Bayne C M Hoogerbrugge J Thomsen L Skriver S C van Buul-Offers J L van den Brande 《Journal of chromatography. A》1991,562(1-2):391-402
Insulin-like growth factors 1 and 2 were purified from porcine plasma. In addition to the determination of their isoelectric points, the primary structures of both proteins were determined, using low microgram quantities of protein, by the versatile combination of time-of-flight plasma desorption mass spectrometry and automated Edman degradation. Porcine insulin-like growth factor 1 was shown to be homologous to both human and bovine proteins; the type 2 growth factor showed one mutation to both human and bovine type 2 proteins. 相似文献
7.
Anders Thygesen Jette Oddershede Hans Lilholt Anne Belinda Thomsen Kenny Ståhl 《Cellulose (London, England)》2005,12(6):563-576
A comparative study of cellulose crystallinity based on the sample crystallinity and the cellulose content in plant fibres
was performed for samples of different origin. Strong acid hydrolysis was found superior to agricultural fibre analysis and
comprehensive plant fibre analysis for a consistent determination of the cellulose content. Crystallinity determinations were
based on X-ray powder diffraction methods using side-loaded samples in reflection (Bragg-Brentano) mode. Rietveld refinements
based on the recently published crystal structure of cellulose Iβ followed by integration of the crystalline and amorphous
(background) parts were performed. This was shown to be straightforward to use and in many ways advantageous to traditional
crystallinity determinations using the Segal or the Ruland–Vonk methods. The determined cellulose crystallinities were 90–100 g/100 g
cellulose in plant-based fibres and 60–70 g/100 g cellulose in wood based fibres. These findings are significant in relation
to strong fibre composites and bio-ethanol production. 相似文献
8.
Summary Optically pure (+)-beta-eudesmol is a possible starting material for the synthesis of several termite defense compounds. A
two step procedure for the isolation of gram quantities of (+)-beta-eudesmol from commercially availableAmyris balsamifera oil (syn. West Indian sandalwood oil), containing 8% beta-eudesmol, was developed. Step one consisted of an efficient vacuum
distillation of the total oil. Step two was a medium pressure LC separation with an AgNO3 impregnated silica gel stationary phase. Several other separation procedures failed due to the presence of many closely related
sesquiterpene alcohols (75% of the oil). 相似文献
9.
10.
H. J. Byrne L. Akselrod C. Thomsen A. Mittelbach S. Roth 《Applied Physics A: Materials Science & Processing》1993,57(4):299-302
The resonant Raman scattering of C60 crystallites is monitored as a function of excitation intensity at 514.5 nm. At low intensities, a strong line at 1468 cm–1 is observed. No feature at 1459 cm–1 is observable. With increasing intensities, the 1468 cm–1 line shifts continuously and reversibly to lower frequencies. The mode softening is nonlinearly dependent on the input intensity and is accompanied by a nonlinear increase in the Raman intensity. The spectral changes are discussed in terms of a nonlinear reduction in force constant and increase in bond polarisability as a result of an increased intermolecular delocalisation of the -electron cloud. The nonlinear changes are associated with the nonlinear luminescence and photoconductive response observed in fullerenes and are contrasted to the irreversible phototransformation recently discussed. 相似文献