全文获取类型
收费全文 | 239篇 |
免费 | 0篇 |
国内免费 | 4篇 |
专业分类
化学 | 95篇 |
力学 | 4篇 |
数学 | 78篇 |
物理学 | 66篇 |
出版年
2013年 | 8篇 |
2012年 | 9篇 |
2011年 | 6篇 |
2010年 | 8篇 |
2009年 | 6篇 |
2008年 | 8篇 |
2007年 | 19篇 |
2006年 | 9篇 |
2005年 | 10篇 |
2004年 | 8篇 |
2003年 | 8篇 |
2002年 | 6篇 |
2000年 | 3篇 |
1999年 | 6篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 4篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1993年 | 4篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1988年 | 3篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 6篇 |
1983年 | 6篇 |
1982年 | 4篇 |
1981年 | 5篇 |
1980年 | 6篇 |
1979年 | 5篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1973年 | 4篇 |
1972年 | 3篇 |
1971年 | 4篇 |
1967年 | 4篇 |
1958年 | 2篇 |
1956年 | 3篇 |
1948年 | 2篇 |
1940年 | 3篇 |
1939年 | 3篇 |
1937年 | 2篇 |
1932年 | 2篇 |
1931年 | 2篇 |
1930年 | 1篇 |
1927年 | 1篇 |
1925年 | 1篇 |
1924年 | 1篇 |
排序方式: 共有243条查询结果,搜索用时 31 毫秒
161.
Hans Petersson 《Mathematische Zeitschrift》1956,66(1):241-268
Ohne Zusammenfassung 相似文献
162.
C.A. Mayhew P. Sulzer F. Petersson S. Haidacher A. Jordan L. Märk P. Watts T.D. Märk 《International journal of mass spectrometry》2010,289(1):58-63
Using recent developments in proton transfer reaction mass spectrometry, proof-of-principle investigations are reported here to illustrate the capabilities of detecting solid explosives in real-time. Two proton transfer reaction time-of-flight mass spectrometers (Ionicon Analytik) have been used in this study. One has an enhanced mass resolution (m/Δm up to 8000) and high sensitivity (~50 cps/ppbv). The second has enhanced sensitivity (~250 cps/ppbv) whilst still retaining high resolution capabilities (m/Δm up to 2000). Both of these instruments have been successfully used to identify solid explosives (RDX, TNT, HMX, PETN and Semtex A) by analyzing the headspace above small quantities of samples at room temperature and from trace quantities not visible to the naked eye placed on surfaces. For the trace measurements a simple pre-concentration and thermal desorption technique was devised and used. Importantly, we demonstrate the unambiguous identification of threat agents in complex chemical environments, where multiple threat agents and interferents may be present, thereby eliminating false positives. This is of considerable benefit to security and for the fight against terrorism. 相似文献
163.
Yu Zhang Xiaoli Wang Partha Mukherjee Patrik Petersson 《Journal of chromatography. A》2009,1216(21):4597-4605
The performance of 2.7 μm superficially porous particles at 600 bar and sub-2 μm fully porous particles at 1000 bar were compared by the Poppe plot method. Theoretical Poppe plots were first constructed for each stationary phase to compare their kinetic performance at different analysis times. The theory was then verified by experiments under the optimized conditions identified from the Poppe plot calculation. We found that the 2.7 μm superficially porous particles at 600 bar can provide similar performance compared to the sub-2 μm fully porous particles at ultra-high pressure (1000 bar) when analysis times are very short (e.g. sub-minute). As analysis time increases, the superficially porous particles start to outperform the sub-2 μm particles and can give much higher efficiencies (e.g. > 2 times higher plate count) at very long analysis times (>3 h). The comparison was extended to gradient elution of a mixture of pharmaceutical interest by constructing gradient peak capacity Poppe plots and similar behavior was observed. 相似文献
164.
Catherine Markopoulou Tracey Tweedlie David Watson Graham Skellern Houssam Reda Patrik Petersson Hannah Bradstock Melvin Euerby 《Chromatographia》2009,70(5-6):705-715
Cyano (CN), butyl (C4), phenyl and octadecyl (C18) phases prepared from the same base silica gel were chromatographically characterized in order to assess the relative importance of lipophilic, π–π and dipole–dipole interactions in governing retention on these differing phases. Dipole interactions of analytes (possessing dipole moments and low lipophilicity) with CN phases were primarily responsible for the elution order. However, as the analytes’ lipophilicity increased, the lipophilic interaction predominated over the dipole interaction. In comparison, retention on the phenyl phase appeared to be complex, being controlled by a mixture of lipophilic, π–π and dipole–dipole interactions. Retention on the C4 and C18 phases was dictated by the analyte’s lipophilicity and its accessibility into the phase. 相似文献
165.
Mohammad A. Al-Laham G. A. Petersson Paul Haake 《Journal of computational chemistry》1991,12(1):113-118
The STO-3G optimized structures of nine different staggered conformers of ascorbic acid are presented. The largest energy difference between the nine local minima is 5.1 kcal/mol. Comparison of the relative energies of the fully optimized structures of ascorbic acid conformers with those of nonoptimized conformers shows that full optimization is essential to obtain meaningful results. However, optimization of the ring structure is almost independent of optimization of the side-chain structure. One of the STO-3G optimized gas phase conformers is very close to the X-ray structure of the crystal. 相似文献
166.
Holger P. Petersson 《Mathematische Zeitschrift》1969,109(3):217-238
Ohne Zusammenfassung 相似文献
167.
Hans Petersson 《Monatshefte für Mathematik》1963,67(3):243-258
Ohne Zusammenfassung 相似文献
168.
Holger P. Petersson 《Mathematische Zeitschrift》1967,98(2):104-118
Ohne Zusammenfassung 相似文献
169.
We numerically study the possibilities for improved large-mode-area endlessly single-mode photonic crystal fibers for use in high-power delivery applications. By carefully choosing the optimal hole diameter, we find that a triangular core formed by three missing neighboring air holes considerably improves the mode area and loss properties compared with the case with a core formed by one missing air hole. In a realized fiber we demonstrate an enhancement of the mode area by approximately 30% without a corresponding increase in the attenuation. 相似文献
170.
The SmI2-H2O-amine mixture has been shown to be effective for intramolecular couplings providing diastereoselectivities of up to 100% de in the coupling of O-cyclohexenyliodophenol derivatives into heterocycles. 相似文献