全文获取类型
收费全文 | 365篇 |
免费 | 3篇 |
国内免费 | 1篇 |
专业分类
化学 | 129篇 |
力学 | 5篇 |
数学 | 68篇 |
物理学 | 167篇 |
出版年
2020年 | 5篇 |
2019年 | 5篇 |
2018年 | 3篇 |
2016年 | 3篇 |
2014年 | 6篇 |
2013年 | 5篇 |
2012年 | 8篇 |
2011年 | 7篇 |
2010年 | 9篇 |
2008年 | 7篇 |
2007年 | 10篇 |
2006年 | 9篇 |
2005年 | 8篇 |
2004年 | 10篇 |
2003年 | 8篇 |
2002年 | 8篇 |
2001年 | 3篇 |
2000年 | 27篇 |
1999年 | 7篇 |
1998年 | 5篇 |
1997年 | 6篇 |
1996年 | 4篇 |
1995年 | 17篇 |
1994年 | 15篇 |
1993年 | 9篇 |
1992年 | 13篇 |
1991年 | 6篇 |
1990年 | 4篇 |
1989年 | 2篇 |
1988年 | 5篇 |
1987年 | 2篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1982年 | 8篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 12篇 |
1978年 | 8篇 |
1977年 | 16篇 |
1976年 | 5篇 |
1975年 | 11篇 |
1974年 | 12篇 |
1973年 | 6篇 |
1972年 | 3篇 |
1971年 | 2篇 |
1970年 | 7篇 |
1936年 | 2篇 |
1932年 | 2篇 |
排序方式: 共有369条查询结果,搜索用时 109 毫秒
1.
The rotational distribution of OH(X
2,v=0) radicals was investigated by resonant laser-induced fluorescence (LIF) after photolysis of H2O2 at 193 nm. A microcomputer equipped LIF arrangement allowed special shot-by-shot normalization of the fluorescence signal for noise reduction. Using a least-squares procedure we were able to account for all measured line intensities including overlapping lines (blends) and obtain a complete rotational state distribution of the OH(X
2,v=0) state. The rotational excitation shows a Gaussian-like distribution with a maximum atK=12 and with 16% of the total available energy (17,400 cm–1) appearing in rotation. Only 1% of the available energy is converted into vibration, leaving over 83% for translational excitation. The measured rotational distribution appears to fit a semiclassical theory. 相似文献
2.
3.
A multipurpose sampler (Gerstel MPS), designed for liquid large volume, gaseous and headspace samples was used for the GC-MS analysis of organic volatiles in human urine. Headspace sampling with a volume-, temperature- and speed-controlled gas-tight syringe was combined with a temperature-controlled cold injection system (CIS) for cold trapping, enrichment and focusing of analytes. Regular 2-ml GC vials filled with 1 ml acidified urine were used as headspace sampling vials. A 100-vial autosampler tray was equipped with an additional temperature and heating time controlled "preheating station" for five vials. Profiles of organic volatiles in human urine were determined and 34 components identified. Trimethylamine (TMA) and 4-heptanone as two metabolites of medical interest were quantified. Calibration curves and intra assay imprecision for 4-heptanone concentrations in the range of 40 to 800 ng/ml showed a correlation coefficient of r = 0.9980 and a relative standard deviation (RSD) between 3.0 and 3.4%. Calibration curves and intra-assay imprecision for TMA concentrations in the range of medical interest from 0.5 to 20 micrograms/ml showed a correlation coefficient of r = 0.9968 and a RSD between 4.1 and 6.8%. The high practicability of the multipurpose sampler for both gaseous and liquid samples together with the here shown good reproducibility and sensitivity make this single CIS-GC-MS system very attractive for routine clinical use in metabolic profiling of organic volatiles (headspace) and non-volatiles (liquid). 相似文献
4.
Morelos A Albuquerque IF Bondar NF Carrigan RA Chen D Cooper PS Lisheng D Denisov AS Dobrovolsky AV Dubbs T Endler AM Escobar CO Foucher M Golovtsov VL Gottschalk H Gouffon P Grachev VT Khanzadeev AV Kubantsev MA Kuropatkin NP Lach J Lang Pengfei Li Chengze Li Yunshan Luksys M Mahon JR McCliment E Newsom C Pommot Maia MC Samsonov VM Schegelsky VA Shi Huanzhang Smith VJ Tang Fukun Terentyev NK Timm S Tkatch II Uvarov LN Vorobyov AA Yan Jie Zhao Wenheng Shuchen Z Zhong Yuanyuan 《Physical review letters》1993,71(21):3417-3420
5.
Morelos A Albuquerque IF Bondar NF Carrigan RA Chen D Cooper PS Dai Lisheng Denisov AS Dobrovolsky AV Dubbs T Endler AM Escobar CO Foucher M Golovtsov VL Gottschalk H Gouffon P Grachev VT Khanzadeev AV Kubantsev MA Kuropatkin NP Lach J Lang Pengfei Li Chengze Li Yunshan Luksys M Mahon JR McCliment E Newsom C Pommot Maia MC Samsonov VM Schegelsky VA Shi Huanzhang Smith VJ Tang Fukun Terentyev NK Timm S Tkatch II Uvarov LN Vorobyov AA Yan Jie Zhao Wenheng Zheng Shuchen Zhong Yuanyuan 《Physical review letters》1993,71(14):2172-2175
6.
7.
Ernst Bayer Gerd Wahl und Heinz Günther Witsch 《Fresenius' Journal of Analytical Chemistry》1961,181(1):384-390
Zusammenfassung Es werden zwei neue, sehr selektive Trennflüssigkeiten, Äthylenglykol-bis(propionitril)-äther und Glycerin-tri(propionitril)-äther, angegeben. Die Trennflüssigkeiten sind so selektiv wie ,-Bis(propionitril)-äther, erlauben aber höhere Arbeitstemperaturen von 140° bzw. 170°C. An Säulen kleinen Querschnittes wird die präparative Trennung größerer Mengen unter Ausnutzung der Selektivität dieser Trennflüssigkeiten aufgezeigt.Die Trennwirksamkeit und die Belastbarkeit von Säulen verschiedenen Durchmessers zwischen 1–10 cm wird angegeben. Die Trennwirksamkeit liegt in der gleichen Größenordnung wie die der analytischen Säulen. Die Belastbarkeit steigt proportional dem Querschnitt an.I. Mitteilung: E. Bayer u. H. G. Witsch, diese Z. 170, 278 (1959). 相似文献
8.
D. Koch M. Wahl A. Wucher 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1994,32(1):137-144
Neutral silver atoms and small clusters Ag n (n=1...4) were generated by sputtering, i.e. by bombarding a polycrystalline silver surface with Ar+ ions of 5 keV. The sputtered particles were ionized by a crossed electron beam and subsequently detected by a quadrupole mass spectrometer. In alternative to the electron impact ionization, the same neutral species were also ionized by single photon absorption from a pulsed VUV laser (photon energy 7.9 eV), and the photoionization cross sections were evaluated from the laser intensity dependence of the measured signals. By in situ combining both ionization mechanisms, absolute values of the ratio σ e (Ag n )/σ e (Ag) between the electron impact ionization cross sections of silver clusters and atoms could be determined for a fixed electron energy of 46 eV. These values can then be used to calibrate previously measured relative ionization functions. By calibrating the results using literature data measured for silver atoms, we present absolute cross sections for electron impact ionization of neutral Ag2, Ag3 and Ag4 as a function of the electron energy between threshold and 125 eV. 相似文献
9.
G. Zech F. Dydak F.L. Navarria O.E. Overseth P. Steffen H. Wahl E.G.H. Williams C. Geweniger K. Kleinknecht H. Taureg 《Nuclear Physics B》1977,124(4):413-425
The mean lifetimes of the Λ and Ξ0 hyperons have been measured in a short neutral beam at the CERN Proton Synchrotron. Λ and Ξ0 decays have been identified by measuring their decay products in a magnetic spectrometer and in a lead glass hodoscope. The experimental results, based on 53 000 Λ decays and 6300 Ξ0 decays are From the result for τΞ0 together with existing data on τΞ? we obtain a violation of the rule in non-leptonic Ξ decays. 相似文献
10.
The mechanism of dediazoniation of arenediazonium tetrafluoroborates in 2,2,2-trifluoroethanol (TFE) is strongly dependent on the concentration of added pyridine. The added base complexes with the diazonium ion and diverts it to a homolytic pathway. Complex formation is indicated by the disappearance of the \documentclass{article}\pagestyle{empty}\begin{document}$\raise1pt\hbox{---} \mathop {\rm N}\limits^ \oplus \equiv {\rm N}\raise1pt\hbox{---}$\end{document} stretching vibration and appearance of a new band at about 1640–1690 cm?1 ascribed to the \documentclass{article}\pagestyle{empty}\begin{document}$\raise1pt\hbox{---} {\rm N}\raise1pt\hbox{=\kern-3.45pt=} {\rm N}\raise1pt\hbox{---} \mathop {\rm N}\limits^ \oplus {\rm C}_5 {\rm H}_5$\end{document} system. UV. and NMR. results support this conclusion. Chemically induced dynamic nuclear polarization (CIDNP) experiments clearly implicate a radical-pair as an important intermediate in the decomposition of these complexes. 相似文献