全文获取类型
收费全文 | 378篇 |
免费 | 8篇 |
国内免费 | 4篇 |
专业分类
化学 | 171篇 |
晶体学 | 3篇 |
力学 | 8篇 |
数学 | 60篇 |
物理学 | 148篇 |
出版年
2023年 | 3篇 |
2020年 | 4篇 |
2019年 | 6篇 |
2017年 | 3篇 |
2016年 | 9篇 |
2015年 | 12篇 |
2014年 | 7篇 |
2013年 | 13篇 |
2012年 | 10篇 |
2011年 | 18篇 |
2010年 | 10篇 |
2009年 | 8篇 |
2008年 | 15篇 |
2007年 | 7篇 |
2006年 | 13篇 |
2005年 | 12篇 |
2004年 | 7篇 |
2003年 | 15篇 |
2002年 | 15篇 |
2001年 | 6篇 |
2000年 | 10篇 |
1999年 | 4篇 |
1998年 | 12篇 |
1997年 | 9篇 |
1996年 | 12篇 |
1995年 | 14篇 |
1994年 | 12篇 |
1993年 | 9篇 |
1992年 | 12篇 |
1991年 | 10篇 |
1989年 | 6篇 |
1988年 | 3篇 |
1987年 | 5篇 |
1986年 | 5篇 |
1985年 | 3篇 |
1984年 | 5篇 |
1982年 | 3篇 |
1979年 | 3篇 |
1978年 | 5篇 |
1976年 | 2篇 |
1974年 | 2篇 |
1973年 | 3篇 |
1972年 | 3篇 |
1968年 | 4篇 |
1944年 | 2篇 |
1943年 | 6篇 |
1932年 | 2篇 |
1931年 | 3篇 |
1922年 | 2篇 |
1880年 | 2篇 |
排序方式: 共有390条查询结果,搜索用时 15 毫秒
91.
Schwab DE Tard C Brecht E Peters JW Pickett CJ Szilagyi RK 《Chemical communications (Cambridge, England)》2006,(35):3696-3698
X-ray absorption spectroscopic measurements and density functional calculations suggest that the hydrogenase H-cluster is best described as an electronically inseparable 6Fe-cluster due to extensive delocalization of frontier molecular orbitals of the iron centres, sulfide and the non-innocent dithiolate ligands. 相似文献
92.
93.
K. H. Chow R. F. Kiefl J. W. Schneider T. L. Estle B. Hitti R. L. Lichti C. Schwab S. R. Kreitzman R. C. DuVarney M. Senba J. Sonier T. M. S. Johnston W. A. MacFarlane 《Hyperfine Interactions》1994,86(1):693-698
We report longitudinal fieldSR 1/T
1 measurements in Si from room temperature to 850 K. The data in pure Si and SiB (p-type) can be explained in a two-state model where muonium cycles between its positive and neutral charge states. Within this model, the average muon-electron hyperfine parameter in the neutral state is consistent with muonium at the tetrahedral interstitial site, indicating that at the highest temperatures measured, neutral muonium spends a significant amount of time away from the bond centered site, the calculated potential minimum. Although this is also true for SiP (n-type) at high temperatures, the data in the region between 300–450 K indicates that at least one other state is involved in the dynamics.This work is partially supported by the Natural Sciences and Engineering Research Council of Canada, the Welch Foundation (C-1048 [TLE], D-1053 [RLL] and the U.S. National Science Foundation (DMR-8917639 [TLE,BH]). 相似文献
94.
A modification of the Gould-Jacobs reaction, particularly useful for the preparation of N-alkyl-4-quinolone-3-carboxylic acids, is described. Decarboxylation of these acids leads to N-alkyl-4-quinolones or, in the case of N-ethyl-benzo[h]-4-quinolone-3-carboxylic acid, to 4-ethoxy-benzo[h]quinoline. Evidence for the structure of the products is presented and the synthesis of relevant compounds is described. 相似文献
95.
M. Herderich E. Richling R. Roscher C. Schneider W. Schwab H. -U. Humpf P. Schreier 《Chromatographia》1997,45(1):127-132
Summary The development of techniques utilizing atmospheric pressure ionization, namely atmospheric pressure chemical ionization (APCI)
and electrospray ionization (ESI), has pioneered the coupling of liquid chromatography (HPLC) with mass spectrometry in recent
years. Both ESI and APCI generate ions from polar and labile biomaterials with remarkable ease and efficiency. In particular,
the use of HPLC with tandem mass spectrometry (MS-MS) opens further dimensions in the field of bioorganic analysis. Thus,
HPLC-MS-MS provides the tools for direct elucidation of the structure and variety of polar natural compounds in complex matrices.
In order to develop efficient and straightforward strategies for the analysis of polar natural products, the potential and
the limitations of these hyphenated analytical techniques are discussed using heterocyclic aromatic amines, fumonisins, acylated
glycoconjugates and regioisomeric fatty acid hydroperoxides as examples.
Presented at the 21st ISC held in Stuttgart, Germany, 15th–20th September, 1996 相似文献
96.
Schwab P Wolf J Mahr N Steinert P Herber U Werner H 《Chemistry (Weinheim an der Bergstrasse, Germany)》2000,6(24):4471-4478
Novel dinuclear rhodium complexes of the general composition [Rh2Cl2(mu-CRR')2(mu-SbiPr3)] (4-6) were prepared by thermolysis of the mononuclear precursors trans-[RhCl(=CRR')(SbiPr3)2] in excellent yield. The X-ray crystal structure analysis of 4 (R = R' = Ph) confirms the symmetrical bridging position of the stibane ligand. Related compounds [Rh2Cl2(mu-CPh2)(mu-CRR')(mu-SbiPr3)] (7, 8) with two different carbene units were obtained either from trans-[RhCl(=CPh2)(SbiPr3)2] (1) and RR'CN2 or by a conproportionation of 4 and 5 (R = R' = p-Tol) or 4 and 6 (R= Ph, R' = p-Tol), respectively. While CO reacts with 4 to give the polymeric product [[RhCl(CPh2)(CO)]n] (9), tert-butyl isocyanide replaces the bridging stibane and yields [Rh2Cl2(mu-CPh2)2(mu-CNtBu)] (10). The reaction of 4 with tertiary phosphanes PR3 leads to complete bridge cleavage and affords the mononuclear compounds trans-[RhCl(=CPh2)(PR3)2] (11-15). In contrast, treatment of 4 with SbMe3 and SbEt3 yields the related triply bridged complexes [Rh2Cl2(mu-CPh2)2(mu-SbR3)] (16, 17) by substitution of SbiPr3 for the smaller stibanes. The displacement of the chloro ligands in 4-6 and 10 by n5-cyclopentadienyl gives the dinuclear complexes [(n5-C5H5)2Rh2(mu-CRR')2] (18-20) and [(n5-C5H5)2Rh2(mu-CPh2)2(mu-CNtBu)] (21), of which 18 (R = R' = Ph) was characterized crystallographically. 相似文献
97.
98.
F. Hess und J. Schwab 《Fresenius' Journal of Analytical Chemistry》1878,17(1):226-231
Ohne Zusammenfassung 相似文献
99.
M. Hesse M. Bernas P. Armbruster T. Aumann S. Czajkowski Ph. Dessagne C. Donzaud H. Geissel E. Hanelt A. Heinz C. Kozhuharov Ch. Miehé G. Münzenberg M. Pfützner C. Röhl K. -H. Schmidt W. Schwab C. Stéphan K. Sümmerer L. Tassan-Got 《Zeitschrift für Physik A Hadrons and Nuclei》1996,355(1):69-75
Charge-loss and fission cross-sections of238U at 750 A·MeV were measured on Al, Cu and Pb targets. The charge-loss rate was obtained by the attenuation method. Fission was selected by detecting the pair of highly ionizing fragments. Since the neutron-loss cross sections were measured in a parallel experiment for the same projectiles, all cross sections contributing to238U collisions on nuclei are available now as function of the target mass number and can be compared with current models. 相似文献
100.
Summary. An elliptic boundary value problem in the interior or exterior of a polygon is transformed into an equivalent first kind boundary
integral equation. Its Galerkin discretization with degrees of freedom on the boundary with spline wavelets as basis functions is analyzed. A truncation strategy is presented
which allows to reduce the number of nonzero elements in the stiffness matrix from to entries. The condition numbers are bounded independently of the meshwidth. It is proved that the compressed scheme thus obtained
yields in operations approximate solutions with the same asymptotic convergence rates as the full Galerkin scheme in the boundary energy
norm as well as in interior points. Numerical examples show the asymptotic error analysis to be valid already for moderate
values of .
Received March 12, 1994 / Revised version received January 9, 1995 相似文献