全文获取类型
收费全文 | 311篇 |
免费 | 12篇 |
专业分类
化学 | 187篇 |
力学 | 9篇 |
数学 | 35篇 |
物理学 | 92篇 |
出版年
2022年 | 2篇 |
2020年 | 3篇 |
2019年 | 2篇 |
2018年 | 3篇 |
2017年 | 2篇 |
2016年 | 7篇 |
2015年 | 5篇 |
2014年 | 7篇 |
2013年 | 14篇 |
2012年 | 9篇 |
2011年 | 12篇 |
2010年 | 12篇 |
2009年 | 12篇 |
2008年 | 20篇 |
2007年 | 14篇 |
2006年 | 23篇 |
2005年 | 19篇 |
2004年 | 13篇 |
2003年 | 11篇 |
2002年 | 11篇 |
2001年 | 3篇 |
2000年 | 12篇 |
1999年 | 7篇 |
1998年 | 4篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1995年 | 5篇 |
1994年 | 3篇 |
1992年 | 7篇 |
1991年 | 3篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1985年 | 2篇 |
1984年 | 5篇 |
1983年 | 8篇 |
1981年 | 2篇 |
1980年 | 5篇 |
1979年 | 2篇 |
1978年 | 9篇 |
1974年 | 3篇 |
1970年 | 4篇 |
1969年 | 5篇 |
1967年 | 2篇 |
1966年 | 2篇 |
1963年 | 2篇 |
1943年 | 2篇 |
1939年 | 1篇 |
1938年 | 2篇 |
1925年 | 1篇 |
1924年 | 1篇 |
排序方式: 共有323条查询结果,搜索用时 732 毫秒
61.
62.
The electrochemical reduction of CO2 holds great promise for lowering the concentration of CO2 in the Earth′s atmosphere. However, several challenges have hindered the commercialization of this technology, including energy efficiency, the solubility of CO2 in the aqueous phase, and electrode stability. In this Minireview, we highlight and summarize the main advantages and limitations that metal–organic frameworks (MOFs) may offer in this field of research, either when used directly as electrocatalysts or when used as catalyst precursors. 相似文献
63.
64.
Zhang J Hoeben FJ Pouderoijen MJ Schenning AP Meijer EW De Schryver FC De Feyter S 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(35):9046-9055
We describe the synthesis, supramolecular ordering on surfaces and in solution, and photophysical characterization of OPV4UT-PERY, an oligo(p-phenylenevinylene) (OPV) with a covalently attached perylene bisimide moiety. In chloroform, the molecule forms dimers through quadruple hydrogen bonding of the ureido-s-triazine array. This is supported by scanning tunneling microscopy (STM) studies, which reveal dimer formation at the liquid (1,2,4-trichlorobenzene)/solid (graphite) interface. Moreover, contrast reversal in bias-dependent STM imaging provides information on the ordering and different electronic properties of the oligo(p-phenylenevinylene) and perylene bisimide moieties. In dodecane, the molecule self-assembles into H-type aggregates that are still soluble as a result of the hydrophobic shell formed by the dodecyloxy wedges. The donor-acceptor molecule is characterized by efficient energy transfer from the photoexcited OPV to the perylene bisimide. Mixed assemblies with analogous OPVs lacking the perylene bisimide unit have been prepared in dodecane solution and energy transfer to the incorporated perylene bisimides has been studied by fluorescence spectroscopy. 相似文献
65.
Sinkeldam RW Hoeben FJ Pouderoijen MJ De Cat I Zhang J Furukawa S De Feyter S Vekemans JA Meijer EW 《Journal of the American Chemical Society》2006,128(50):16113-16121
The ability of foldamers to adopt a secondary structure in solution has been exploited to organize peripheral functionality. Our previously reported poly(ureidophthalimide) foldamer proved to be an excellent scaffold for the chiral organization of peripherally positioned oligo(p-phenylenevinylene) (OPV) chromophores. Facile high-yielding synthesis gave access to the required OPV-decorated building blocks. A condensation polymerization provided polymers of sufficient length to allow construction of a helical architecture comprising several turns. Short and long chains were separated by chromatography. Circular dichroism studies in THF of the longer chains indicate the presence of helically arranged OPVs. However, such an effect is not observed in CHCl3. Remarkable are the measurements of the OPV foldamers in heptane. A bisignate Cotton effect is observed in heptane of a sample with a THF history. No Cotton effect is observed in heptane of a sample with a CHCl3 history. In this example of supramolecular synthesis, the solvent dictates the expression of supramolecular chirality in a secondary structure. The short-chain oligomeric fractions that are unable to create a full turn revealed on scanning tunneling microscopy analysis the presence of circular architectures at the graphite/1-phenyloctane interface. This is in full agreement with the proposed conformation of the decorated foldamers. 相似文献
66.
Thomas Brinkmann 《Nachrichten aus der Chemie》2005,53(5):552-552
67.
Johan Hygum Dam Niels Langkjr Christina Baun Birgitte Brinkmann Olsen Aaraby Yoheswaran Nielsen Helge Thisgaard 《Molecules (Basel, Switzerland)》2022,27(20)
Background: The somatostatin receptors 1–5 are overexpressed on neuroendocrine neoplasms and, as such, represent a favorable target for molecular imaging. This study investigates the potential of [18F]AlF-NOTA-[1-Nal3]-Octreotide and compares it in vivo to DOTA- and NOTA-[1-Nal3]-Octreotide radiolabeled with gallium-68. Methods: DOTA- and NOTA-NOC were radiolabeled with gallium-68 and NOTA-NOC with [18F]AlF. Biodistributions of the three radioligands were evaluated in AR42J xenografted mice at 1 h p.i and for [18F]AlF at 3 h p.i. Preclinical PET/CT was applied to confirm the general uptake pattern. Results: Gallium-68 was incorporated into DOTA- and NOTA-NOC in yields and radiochemical purities greater than 96.5%. NOTA-NOC was radiolabeled with [18F]AlF in yields of 38 ± 8% and radiochemical purity above 99% after purification. The biodistribution in tumor-bearing mice showed a high uptake in tumors of 26.4 ± 10.8 %ID/g for [68Ga]Ga-DOTA-NOC and 25.7 ± 5.8 %ID/g for [68Ga]Ga-NOTA-NOC. Additionally, [18F]AlF-NOTA-NOC exhibited a tumor uptake of 37.3 ± 10.5 %ID/g for [18F]AlF-NOTA-NOC, which further increased to 42.1 ± 5.3 %ID/g at 3 h p.i. Conclusions: The high tumor uptake of all radioligands was observed. However, [18F]AlF-NOTA-NOC surpassed the other clinically well-established radiotracers in vivo, especially at 3 h p.i. The tumor-to-blood and -liver ratios increased significantly over three hours for [18F]AlF-NOTA-NOC, making it possible to detect liver metastases. Therefore, [18F]AlF demonstrates promise as a surrogate pseudo-radiometal to gallium-68. 相似文献
68.
In this paper, two problems from the molecular sciences are addressed: the enumeration of fullerene-type isomers and the alignment
of biosequences. We report on two algorithms dealing with these problems both of which are based on the well-known and widely
used Divide&Conquer principle. In other words, our algorithms attack the original problems by associating with them an appropriate
number of much simpler problems whose solutions can be “glued together” to yield solutions of the original, rather complex
tasks. The considerable improvements achieved this way exemplify that the present day molecular sciences offer many worthwhile
opportunities for the effective use of fundamental algorithmic principles and architectures. 相似文献
69.
M. Hube R. Brinkmann H. Welling R. Beigang B. Wellegehausen 《Applied physics. B, Lasers and optics》1988,45(3):197-201
Soft x-rays from a laser-produced plasma were used to perform innershell photoionization of Cd atoms and to generate laser radiation at 442 nm. To achieve longer interaction zones between the Cd vapor and the soft x-ray flux, up to three plasma spots have been applied. In this way a maximum laser energy of 300 J with a 600 mJ Nd:YAG laser for the plasma production was achieved. Experimental investigations and corresponding rate-equation calculations indicate, that photoelectrons play an important role in the total laser kinetics. 相似文献
70.
K. -Th. Brinkmann J. Kiesewetter H. Freiesleben H. Gassel 《Zeitschrift für Physik A Hadrons and Nuclei》1992,343(1):59-65
The partition of excitation energy between fragments from reactions of 8 A · MeV116Sn with48Ti was studied. The experimental setup rendered possible the unambiguous identification of primary fragments up to total excitation energies of 50 MeV. Neutron mulitplicities of both projectile-like and target-like fragments were experimentally determined as a function of excitation energy. Comparison of these quantities with the results of numerical calculations of sequential decay including rotation of the fragments allowed the determination of excitation energy partition and the associated fluctuations.This work is part of the doctoral thesis of K.-Th. Brinkmann, Ruhr-Universität Bochum 1991 相似文献