全文获取类型
收费全文 | 484篇 |
免费 | 20篇 |
国内免费 | 4篇 |
专业分类
化学 | 338篇 |
晶体学 | 4篇 |
力学 | 4篇 |
数学 | 43篇 |
物理学 | 119篇 |
出版年
2023年 | 1篇 |
2022年 | 4篇 |
2021年 | 6篇 |
2020年 | 7篇 |
2019年 | 8篇 |
2018年 | 5篇 |
2017年 | 5篇 |
2016年 | 17篇 |
2015年 | 14篇 |
2014年 | 20篇 |
2013年 | 21篇 |
2012年 | 33篇 |
2011年 | 34篇 |
2010年 | 24篇 |
2009年 | 16篇 |
2008年 | 35篇 |
2007年 | 25篇 |
2006年 | 26篇 |
2005年 | 18篇 |
2004年 | 27篇 |
2003年 | 12篇 |
2002年 | 10篇 |
2001年 | 7篇 |
2000年 | 6篇 |
1999年 | 2篇 |
1998年 | 6篇 |
1997年 | 6篇 |
1996年 | 15篇 |
1995年 | 15篇 |
1994年 | 14篇 |
1993年 | 15篇 |
1992年 | 12篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1988年 | 5篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1982年 | 1篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 4篇 |
1973年 | 3篇 |
1967年 | 1篇 |
1903年 | 1篇 |
排序方式: 共有508条查询结果,搜索用时 15 毫秒
1.
Astrid Baumann 《Mathematische Semesterberichte》1998,45(2):167-188
Zusammenfassung. Mit Hilfe der projektiven Geometrie werden neuartige Summationsformeln hergeleitet, die die Tschebyscheff-Polynome und modifizierte Polynome enthalten; z. B. gilt für alle :
Daraus ergeben sich wiederum interessante Summationsformeln für die Hyperbelfunktionen; es gilt z. B. für positive reelle
Zahlen t:
Eingegangen am 28.02.96, revidierte Fassung am 25.08.97 / Angenommen am 09.10.97 相似文献
2.
Simulation of coupled chemical reactions and fluid flow in porous sedimentary basins over long time periods is a numerical
challenge. Most models representing such a physical problem are solved as PDEs where efficient timestepping with controlled
error is difficult. We use the differential algebraic equation system approach where robust adaptive timestepping algorithms
are available in the solvers, e.g., RADAU5 and DASSL. Mathematical and numerical models for coupled chemical reactions and
fluid flow are derived. The models have several interesting properties, e.g., strong nonlinearities and stiffness, which are
discussed. We test the performance of our code.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
3.
O. Yilmaz F. Y. Lambrecht N. Gokmen S. Erbayraktar K. Durkan 《Journal of Radioanalytical and Nuclear Chemistry》2007,273(2):311-313
The aim of the present study was to demonstrate the possible transplacental transmission of 131I labeled recombinant human erythropoietin (131I-rh-EPO) in pregnant rats and its distribution through maternal and fetal organs. Six Wistar Albino Rats in their pregnancy
of 18 days were used 131I labeled recombinant human erythropoietin (specific activity = 2.4 μCi/IU) was injected into the tail vein of rats. After
30 minutes labeled erythropoietin infusion maternal stomach, kidney, lung, liver, brain and heart as well as fetus were removed.
Then, the same organs were removed from each fetus. Measuring weight of maternal and fetal organs as well as placenta were
followed by radioactivity count via Cd(Te) detector. 131I labeled recombinant human erythropoietin was found to be able to pass rat placenta and its distribution order in fetal organs
was similar to those of maternal organs. Besides, as measurements were performed closer to cornu uteri, uptakes were decreasing
in every fetus and its corresponding placenta. 相似文献
4.
Lukin O Müller WM Müller U Kaufmann A Schmidt C Leszczynski J Vögtle F 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(15):3507-3517
The readily available in gram quantities tris(allyloxy)knot of the amide-type 5 (knotane) can be completely and partially deprotected with nBu(3)SnH in the presence of a palladium catalyst resulting in hydroxyknotanes 7-9. These, in turn, react with diethylchlorophosphate giving rise to knotanes equipped with between one and three phosphoryl groups. Sulfonylation of bis(allyloxy)monohydroxyknotane 8 with p-toluenesulfonyl chloride and, following removal of one or two allyl groups from the intermediate monosulfonate 13, give rise to sulfonyloxy-allyloxy-hydroxy- and sulfonyloxy-dihydroxy-knotanes 15 and 14, respectively. This provides a convenient method for the preparation of knotanes with any substitution pattern. All new knotanes have been isolated in preparative amounts and as highly pure substances with an exception of allyloxy-dihydroxyknotane 9. This compound could only be obtained as a mixture with the corresponding monohydroxy-derivative 8. The structures of all synthesized compounds were established by means of FAB and MALDI TOF mass spectrometry, (1)H and (31)P NMR spectroscopy. The triphosphorylated knotane 10 exhibits high solubility in alcohols, allowing its complete enantiomeric resolution with a commercially available chiral HPLC column. (1)H,(1)H DQF-COSY correlation spectroscopy along with H/D exchange experiments and ab initio calculations provided the first detailed (1)H NMR signal assignments of knotanes in [D(6)]DMSO solution. The combination of variable temperature (1)H and (31)P NMR spectroscopy and molecular modeling has been applied to study the conformational behavior of the new knotanes in different solvents. It has been shown that in DMSO solution at room temperature knotanes exist in a relatively rigid nonsymmetrical conformation similar to that found in the solid state while faster conformational exchange leading to the average D(3) symmetrical structure was detected in a number of other solvents. 相似文献
5.
Campa C Oust A Skjåk-Braek G Paulsen BS Paoletti S Christensen BE Ballance S 《Journal of chromatography. A》2004,1026(1-2):271-281
The average degree of polymerisation (DP) and distribution of oligosaccharides in partially acid hydrolysed mannuronans were quantitatively evaluated by 1H NMR, electrospray ionisation mass spectrometry (ESI-MS), micellar electrokinetic capillary chromatography with UV detection (MEKC-UV), and high-pressure anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD). Our investigation shows that 1H NMR, MEKC-UV and, in particular, HPAEC-PAD can be used as quantitative tools to aid the investigation of polysaccharide structure, function and synthesis. For the latter two techniques, especially, this represents a significant new development as it enables calculation of the quantity of individual oligomers of nominal DP by direct analysis of a defined oligomer mixture. Appropriate statistical averages of number and weight distributions were also calculated and found to fit very well to predicted Kuhn distributions that assume random depolymerisation. 相似文献
6.
Martina Dotzler Astrid Schmidt Jochen Ellermann Falk A. Knoch Matthias Moll Walter Bauer 《Polyhedron》1996,15(24):4425-4433
BiBr3 or SbI3 react at 20°C with LiN(PPh2)2 (1) to give elementary Bi or Sb and the P---P coupled phosphazene ligand Ph2P---N=PPh2---PPh2=N---PPh2 (2). The reaction of AsI3 with 1 at room temperature formed yellow needles of the eight-membered heterocycle
(3), whereas AsI3 interacted at 80°C with 1 in the molar ratio of 1:3 to give elementary arsenic and 2. Treatment of AsI3 and 1 at 20°C in a 1:2 stoichiometry yielded the seven-membered, cyclic arsenium(I) salt I·4THF (5·4THF), which was characterized by elemental analysis, conductivity, mass, IR and NMR spectroscopy and single-crystal X-ray structural analysis. 相似文献
7.
Astrid Döppenschmidt 《Czechoslovak Journal of Physics》1995,45(7-8):657-661
0-production in the system12C+12C was studied with the two-arm photon spectrometer TAPS at projectile energies of 800 and 1000 MeV/u. The experiments focus on the determination of the cross sections and the correspondingp
t
-distributions. The results will extend the existing systematics of
0-production in heavy-ion collisions to a system with small mass.Presented at the International School-Workshop Relativistic Heavy-Ion Physics, Prague (Czech Republic), 19–23 September 1994. 相似文献
8.
Battle M Ernst J Kwon Y Roberts S Thorndike EH Wang CH Dominick J Lambrecht M Sanghera S Shelkov V Skwarnicki T Stroynowski R Volobouev I Wei G Zadorozhny P Artuso M Goldberg M He D Horwitz N Kennett R Mountain R Moneti GC Muheim F Mukhin Y Playfer S Rozen Y Stone S Thulasidas M Vasseur G Zhu G Bartelt J Csorna SE Egyed Z Jain V Kinoshita K Edwards KW Ogg M Britton DI Hyatt ER MacFarlane DB Patel PM Akerib DS Barish B Chadha M Chan S Cowen DF Eigen G Miller JS O'Grady C Urheim J Weinstein AJ 《Physical review letters》1994,73(8):1079-1083
9.
Kubota Y Lattery M Nelson JK Patton S Perticone D Poling R Savinov V Schrenk S Wang R Alam MS Kim IJ Nemati B O'Neill JJ Severini H Sun CR Zoeller MM Crawford G Daubenmier CM Fulton R Fujino D Gan KK Honscheid K Kagan H Kass R Lee J Malchow R Morrow F Skovpen Y Sung M White C Butler F Fu X Kalbfleisch G Ross WR Skubic P Snow J Wang PL Wood M Brown DN Fast J McIlwain RL Miao T Miller DH Modesitt M Payne D Shibata EI Shipsey IP Wang PN Battle M Ernst J Kwon Y Roberts S Thorndike EH Wang CH 《Physical review letters》1994,72(13):1972-1976
10.
Alam MS Kim IJ Nemati B O'Neill JJ Severini H Sun CR Zoeller MM Crawford G Daubenmier CM Fulton R Fujino D Gan KK Honscheid K Kagan H Kass R Lee J Malchow R Morrow F Skovpen Y Sung M White C Butler F Fu X Kalbfleisch G Ross WR Skubic P Snow J Wang PL Wood M Brown DN Fast J McIlwain RL Miao T Miller DH Modesitt M Payne D Shibata EI Shipsey IP Wang PN Battle M Ernst J Kwon Y Roberts S Thorndike EH Wang CH Dominick J Lambrecht M Sanghera S Shelkov V Skwarnicki T Stroynowski R Volobouev I Wei G 《Physical review D: Particles and fields》1994,50(1):43-68