全文获取类型
收费全文 | 599篇 |
免费 | 21篇 |
国内免费 | 40篇 |
专业分类
化学 | 419篇 |
晶体学 | 7篇 |
力学 | 19篇 |
综合类 | 1篇 |
数学 | 41篇 |
物理学 | 173篇 |
出版年
2023年 | 11篇 |
2022年 | 18篇 |
2021年 | 14篇 |
2020年 | 18篇 |
2019年 | 17篇 |
2018年 | 9篇 |
2017年 | 10篇 |
2016年 | 19篇 |
2015年 | 16篇 |
2014年 | 19篇 |
2013年 | 27篇 |
2012年 | 40篇 |
2011年 | 51篇 |
2010年 | 19篇 |
2009年 | 13篇 |
2008年 | 24篇 |
2007年 | 41篇 |
2006年 | 30篇 |
2005年 | 22篇 |
2004年 | 8篇 |
2003年 | 17篇 |
2002年 | 19篇 |
2001年 | 10篇 |
2000年 | 6篇 |
1999年 | 7篇 |
1997年 | 4篇 |
1996年 | 6篇 |
1995年 | 16篇 |
1994年 | 7篇 |
1993年 | 5篇 |
1992年 | 6篇 |
1991年 | 4篇 |
1989年 | 5篇 |
1988年 | 6篇 |
1987年 | 8篇 |
1986年 | 8篇 |
1985年 | 8篇 |
1984年 | 10篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1980年 | 6篇 |
1978年 | 4篇 |
1977年 | 8篇 |
1976年 | 3篇 |
1975年 | 4篇 |
1974年 | 11篇 |
1973年 | 6篇 |
1972年 | 5篇 |
1971年 | 5篇 |
1970年 | 4篇 |
排序方式: 共有660条查询结果,搜索用时 15 毫秒
61.
P. Zaleski K. SzymańskiW. Olszewski M. BiernackaK. Perzyńska D. Satu?aA. Go J. Przewo?nikD.A. Zaj?c M. PylakL. Dobrzyński 《Physica B: Condensed Matter》2011,406(17):3196-3205
The lattice site occupation of 3d-type impurities in Cr3Si doped with Fe, Co and Ni were studied using the Extended X-ray Absorption Fine Structure (EXAFS) technique, X-rays and magnetic susceptibility measurements. The EXAFS measurements were performed particularly carefully on the K-edge of chromium and cobalt. EXAFS data strengthened by simulations of the spectra show unambiguously that the impurities are occupying mostly Cr-sites. The magnetic state of the alloys has been studied theoretically using the Wien2k code. It is observed that if calculations are not carried out on an appropriately fine mesh of points in k-space, one can get the result indicating ferromagnetism although the overall magnetic moment per formula unit is weak. 相似文献
62.
Jian Shen Shiyang Liu Rong Cao Xin Fan Junjie Du Huaiwu Zhang Zhifang Lin Siu-Tat Chui John Q. Xiao 《Applied Physics A: Materials Science & Processing》2011,105(4):789-793
We experimentally studied magnetically controllable photonic band gaps (PBGs) in two-dimensional magnetic photonic crystals
consisting of ferrite rods. Besides the conventional PBG that relates to Bragg scattering, two other types of PBG, resulting
from magnetic surface plasmon (MSP) resonance and spin-wave resonance, respectively, are observed. The PBG due to MSP resonance
is particularly interesting because of its analogy to surface plasmon in metal; furthermore, it is shown to be completely
tunable by an external static magnetic field from both an experimental and a theoretical point of view. 相似文献
63.
Atmospheric pressure wire-to-plane positive corona discharges have been explored experimentally in electrode gaps from 0.3 mm to 5 mm. Reductions in the gap distance and wire diameter resulted in a significant increase in discharge currents and lowered onset potentials, and the current–voltage characteristics followed the typical Townsend’s relationship. The experimentally observed onset potentials were higher than Peek’s prediction although they still showed the same logarithmic behavior with gap distance. Additionally, a theoretical relationship for the current–voltage discharge in a wire-to-plane configuration was derived to obtain the dependence on the geometric parameters, and it compared well with the experimental results. 相似文献
64.
Determination of catechin and epicatechin in the peel of apple varieties resistant and non-resistant to apple scab 总被引:1,自引:0,他引:1
Marek Gołębiowski Edmund Maliński Małgorzata Szankin Mariusz Marszeniuk Monika Paszkiewicz Piotr Stepnowski 《Chemical Papers》2010,64(6):729-733
Catechin and epicatechin were analysed in the peel of six apple cultivars (three resistant and three non-resistant to apple
scab). Two methods of analytical sample preparation following extraction were tested: solid phase extraction and column separation
with Sephadex LH-20 coupled to a differential refractometric detector. Prior to GC and GC-MS analyses, these compounds were
silylized. This permitted co-injection with standards and the comparison of retention values and mass spectra with those recorded
for standards. The content of catechin and epicatechin in apple peel is discussed in relation to the resistance of apple trees
to scab. 相似文献
65.
Daisuke Nagae Koichiro Asahi Hisanori Miyoshi Kenzi Shimada Akihiro Yoshimi Hideki Ueno Jiro Murata Makoto Uchida Daisuke Kameda Go Kato Shoken Emori Go Kijima Sachiko Oshima Makoto Takemura Takemasa Arai Yoshio Kobayashi Tomohito Haseyama W.D. Schmidt-Ott 《Physica E: Low-dimensional Systems and Nanostructures》2005,29(3-4):580
A device that produces a low-energy and largely spin polarized RI beam based on the atomic beam resonance method (RIABR) has been developed. We have performed measurements of stopping and drifting an incoming RI ion beam in a gas chamber, extraction of the ions into a vacuum region, and neutralization of the extracted low-energy ion beam. The drift efficiency of RI ions in a gas and the extraction efficiency at a Laval-type glass nozzle were found to be 0.72±0.04 and 0.033, respectively. The result of the experiment for the neutralization is also discussed. 相似文献
66.
Yasuhiro Shiraishi Yugo Furubayashi Go Nishimura Takayuki Hirai 《Journal of luminescence》2007,127(2):623-632
Dinuclear lanthanide (Ln=Tb3+ or Eu3+) complexes (Ln2L2) of two octadentate macrocyclic polyaminopolycarboxylic ligands connected through a benzophenone (BP) moiety (L2) have been synthesized. Sensitized luminescence properties of Ln2L2 in water have been studied in comparison to those of BP-conjugated mononuclear Ln complexes (LnL1). The luminescence intensity of Tb2L2 is lower than that of TbL1 because of lower triplet quantum yield of the BP moiety. In contrast, Eu2L2 shows higher intensity than EuL1. For both Eu complexes, energy level of triplet excited-state BP (3BP*) is only 3 kJ mol−1 higher than that of 5D2 excited-state of Eu3+. The 5D2 state formed by a triplet-energy transfer (TET) from 3BP* is therefore deactivated by a back energy transfer (BET) to the ground-state BP, resulting in low luminescence intensity of EuL1. In contrast, within Eu2L2, TET from 3BP* to 5D0 state of two Eu3+ ions is accelerated, thus leading to higher luminescence intensity. Another notable feature of Eu2L2 is the luminescence quantum yield independent of its concentration. In contrast, for EuL1 system, an intermolecular BET occurs from 5D2 state of Eu3+ to the ground-state BP conjugated to another EuL1 complex, resulting in a yield decrease with the concentration increase. 相似文献
67.
Supramolecular Polyelectrolyte Complexes of Bone Morphogenetic Protein‐2 with Sulfonated Polyrotaxanes to Induce Enhanced Osteogenic Differentiation
下载免费PDF全文
![点击此处可从《Macromolecular bioscience》网站下载免费的PDF全文](/ch/ext_images/free.gif)
68.
Lei Li Yunpeng Liu Cheng Ma Jingyao Qu Angie D. Calderon Baolin Wu Na Wei Xuan Wang Yuxi Guo Zhongying Xiao Jing Song Go Sugiarto Yanhong Li Hai Yu Xi Chen Peng George Wang 《Chemical science》2015,6(10):5652-5661
Quantification, characterization and biofunctional studies of N-glycans on proteins remain challenging tasks due to the complexity, diversity and low abundance of these glycans. The availability of structurally defined N-glycan (especially isomer) libraries is essential to help solve these tasks. We report herein an efficient chemoenzymatic strategy, namely Core Synthesis/Enzymatic Extension (CSEE), for rapid production of diverse N-glycans. Starting with 5 chemically prepared building blocks, 8 N-glycan core structures containing one or two terminal N-acetyl-d-glucosamine (GlcNAc) residue(s) were chemically synthesized via consistent use of oligosaccharyl thioethers as glycosylation donors in a convergent fragment coupling strategy. Each of these core structures was then extended to 5 to 15 N-glycan sequences by enzymatic reactions catalyzed by 4 robust glycosyltransferases. Success in synthesizing N-glycans with Neu5Gc and core-fucosylation further expanded the ability of the enzymatic extension. Meanwhile, high performance liquid chromatography with an amide column enabled rapid and efficient purification (>98% purity) of N-glycans in milligram scales. A total of 73 N-glycans (63 isomers) were successfully prepared and characterized by MS2 and NMR. In summary, the CSEE strategy provides a practical approach for “mass production” of structurally defined N-glycans, which are important standards and probes for glycoscience. 相似文献
69.
Boris M. Mandić Dejan M. Gođevac Ljubodrag V. Vujisić Snežana S. Trifunović Vele V. Tesević Vlatka V. Vajs Slobodan M. Milosavljević 《Chemical Papers》2011,65(1):90-92
In this paper, examination of the aerial parts of seven Senecio species from Serbia and Montenegro is reported. Phytochemical investigation of Senecio erucifolius led to the isolation and characterization of semiquinol butyl 2-(1-hydroxy-4-oxocyclohexa-2,5-dienyl)acetate (I), along with methyl 2-(1-hydroxy-4-oxocyclohexa-2,5-dienyl)acetate (jacaranone, II), and methyl 2-(4-hidroxyphenyl)acetate (III). The structure of I was established based on spectroscopic studies (1H- and 13C-NMR, IR, and CI-MS). Compound II was also isolated from S. carpathicus and S. subalpinus. The presence of jacaranone in the methanol extracts of S. wagneri, S. othonnae, and S. paludosus was confirmed by LC/ESI-TOF MS. 相似文献
70.
Furukawa H Go YB Ko N Park YK Uribe-Romo FJ Kim J O'Keeffe M Yaghi OM 《Inorganic chemistry》2011,50(18):9147-9152
The concept and occurrence of isoreticular (same topology) series of metal-organic frameworks (MOFs) is reviewed. We describe the preparation, characterization, and crystal structures of three new MOFs that are isoreticular expansions of known materials with the tbo (Cu(3)(4,4',4'-(benzene-1,3,5-triyl-tris(benzene-4,1-diyl))tribenzoate)(2), MOF-399) and pto topologies (Cu(3)(4,4',4'-(benzene-1,3,5-triyl-tribenzoate)(2), MOF-143; Cu(3)(4,4',4'-(triazine-2,4,6-triyl-tris(benzene-4,1-diyl))tribenzoate)(2), MOF-388). One of these materials (MOF-399) has a unit cell volume 17 times larger than that of the first reported material isoreticular to it, and has the highest porosity (94%) and lowest density (0.126 g cm(-3)) of any MOFs reported to date. 相似文献