全文获取类型
收费全文 | 726篇 |
免费 | 21篇 |
国内免费 | 2篇 |
专业分类
化学 | 637篇 |
晶体学 | 4篇 |
力学 | 6篇 |
数学 | 43篇 |
物理学 | 59篇 |
出版年
2022年 | 8篇 |
2021年 | 6篇 |
2020年 | 13篇 |
2019年 | 11篇 |
2018年 | 6篇 |
2017年 | 4篇 |
2016年 | 21篇 |
2015年 | 8篇 |
2014年 | 17篇 |
2013年 | 25篇 |
2012年 | 38篇 |
2011年 | 36篇 |
2010年 | 30篇 |
2009年 | 29篇 |
2008年 | 40篇 |
2007年 | 28篇 |
2006年 | 39篇 |
2005年 | 32篇 |
2004年 | 27篇 |
2003年 | 13篇 |
2002年 | 18篇 |
2000年 | 6篇 |
1999年 | 10篇 |
1998年 | 7篇 |
1997年 | 4篇 |
1996年 | 7篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1993年 | 7篇 |
1992年 | 5篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 10篇 |
1988年 | 10篇 |
1987年 | 9篇 |
1986年 | 9篇 |
1985年 | 7篇 |
1984年 | 8篇 |
1983年 | 7篇 |
1982年 | 7篇 |
1981年 | 12篇 |
1980年 | 3篇 |
1979年 | 5篇 |
1978年 | 6篇 |
1977年 | 4篇 |
1968年 | 4篇 |
1967年 | 11篇 |
1966年 | 39篇 |
1965年 | 43篇 |
1964年 | 20篇 |
排序方式: 共有749条查询结果,搜索用时 31 毫秒
701.
702.
Marianne?P.?WilkersonEmail author Harry?J.?Dewey Pamela?L.?Gordon Brian?L.?Scott 《Journal of chemical crystallography》2004,34(11):807-811
The reaction of a stock solution of NpO22 + in 2 M HCl with two equivalents of tetrabutylammonium chloride in 6 M HCl results in the preparation of the title compound. This compound, [NBu4]2[NpO2Cl4], is isostructural with the uranium analogue, [NBu4]2[UO2Cl4]. The anion of the complex, [NpO2Cl4]2–, adopts a pseudooctahedral geometry common to six-coordinate actinyl complexes in which the neptunium metal is coordinated by two trans axial oxo groups with NpO(oxo) bond lengths of 1.733(5)Å, and four equatorial chloride ligands with Np–Cl bond lengths in the range 2.637(2)–2.676(2)Å. The neptunyl ONpO bond angle is 178.6(3)°. Charge balance of the neptunyl tetrachloride anion is maintained by two tetrabutylammonium cations. This complex crystallizes in the monoclinic space group P21/n (a = 15.416(4), b = 15.362(4), c = 18.479(5)Å, = 108.147(6)°, V = 4158.4(19)Å3, Z = 4). 相似文献
703.
In contrast to the increased hepatic albumin synthesis in subjects with proteinuria, little is known about the corresponding whole-body protein turnover rates (WPTR). The WPTR and the reutilisation rates (R) were investigated in 20 patients divided in three groups of different degrees of proteinuria (groups I-III: < 1, 1-3, > 3 g/m2/day, respectively). [15N]glycine was administered as a single oral pulse. Urine samples were taken over 2 days. After removing urinary proteins by trichloracetic acid, 15N-enrichment in the supernatant was measured by isotope ratio mass spectrometry. A three-compartment model was used to calculate WPTR and R, which showed a statistically significant difference between groups I and III (2.64 vs. 4.63 g/kg/day, and 70.4% vs. 80.8%, respectively, P < 0.01), whereas the net protein gain remained unchanged (0.13 vs. 0.22 g/kg/day). The higher the protein loss the higher the WPTR and the corresponding R. The severe protein loss provokes increased WPTR and R as well. 相似文献
704.
The enantiomeric separation of a series of basic pharmaceuticals (beta-blockers, local anesthetics, sympathomimetics) has been investigated in nonaqueous capillary electrophoresis (NACE) systems using heptakis(2,3-di-O-methyl-6-O-sulfo)-beta-cyclodextrin (HDMS-beta-CD) in combination with potassium camphorsulfonate (camphorSO3-). For this purpose, a face-centered central composite design with 11 experimental points was applied. The effect of the concentrations of HDMS-beta-CD and camphorSO3- on enantioresolution was statistically evaluated and depended largely on the considered analyte. The presence of camphorSO3- was found to be particularly useful for the enantioseparation of compounds with high affinity for the anionic CD. CamphorSO3- seems to act as a competitor, reducing the affinity for the CD, probably by ion-pair formation with these analytes. For compounds with lower affinity for HDMS-beta-CD, the combination of camphorSO3- and the CD appeared to have a favorable effect on enantioresolution only if the optimal CD concentration could be reached. On the other hand, for compounds characterized by a very low affinity for the anionic CD, the association of camphorSO3- and HDMS-beta-CD is always unfavorable. Finally, experimental conditions were selected by means of the multivariate approach in order to obtain the highest resolution (Rs) value for each studied compound. 相似文献
705.
Numerous infrared transitions between Rydberg states of neon and argon have been measured by optogalvanic spectroscopy in commercial hollow cathode lamps using a color center laser operating in the range 3600–4100 cm-1. Transitions in lithium and barium atoms sputtered from the cathodes were also detected. The generality and high sensitivity of this technique indicates potential applications for frequency calibration in the infrared, atomic and molecular spectroscopy, and plasma diagnostics. 相似文献
706.
707.
708.
709.
Gregory S. Anderson Wolfgang H. H. Günther Roger Searle James M. Bilitz Marianne Krieg Fritz Sieber 《Photochemistry and photobiology》1996,64(4):683-687
Abstract— Merocyanine dyes with an oxygen in the electron donor heterocycle were rapidly degraded by plasma, serum and serum components. Replacement of the oxygen by a sulfur or selenium atom rendered the dyes refractory to degradation. The degradation of labile merocyanine dyes was temperature dependent and oxygen independent. The plasma component that was responsible for the degradation of merocyanine dyes was sensitive to heat and detergent, suggesting an enzymatic process. The identification of the structural requirements for sensitivity/resistance to degradation provides the experimenter with a simple means to manipulate the stability of mer-ocyanines in high serum or plasma environments and may expand the clinical utility of merocyanine photosen-sitizers beyond their traditional role in the extracorporeal purging of bone marrow grafts. 相似文献
710.