全文获取类型
收费全文 | 1390篇 |
免费 | 50篇 |
国内免费 | 12篇 |
专业分类
化学 | 1092篇 |
晶体学 | 16篇 |
力学 | 12篇 |
数学 | 91篇 |
物理学 | 241篇 |
出版年
2023年 | 5篇 |
2021年 | 14篇 |
2020年 | 24篇 |
2019年 | 25篇 |
2018年 | 17篇 |
2017年 | 7篇 |
2016年 | 35篇 |
2015年 | 21篇 |
2014年 | 24篇 |
2013年 | 69篇 |
2012年 | 72篇 |
2011年 | 87篇 |
2010年 | 49篇 |
2009年 | 44篇 |
2008年 | 85篇 |
2007年 | 70篇 |
2006年 | 81篇 |
2005年 | 87篇 |
2004年 | 70篇 |
2003年 | 66篇 |
2002年 | 48篇 |
2001年 | 25篇 |
2000年 | 32篇 |
1999年 | 18篇 |
1998年 | 17篇 |
1997年 | 19篇 |
1996年 | 16篇 |
1995年 | 14篇 |
1994年 | 19篇 |
1993年 | 14篇 |
1992年 | 20篇 |
1991年 | 15篇 |
1990年 | 20篇 |
1989年 | 16篇 |
1988年 | 13篇 |
1987年 | 8篇 |
1986年 | 5篇 |
1985年 | 22篇 |
1984年 | 25篇 |
1983年 | 12篇 |
1982年 | 19篇 |
1981年 | 11篇 |
1980年 | 7篇 |
1979年 | 14篇 |
1978年 | 9篇 |
1977年 | 7篇 |
1975年 | 5篇 |
1974年 | 8篇 |
1970年 | 5篇 |
1962年 | 4篇 |
排序方式: 共有1452条查询结果,搜索用时 31 毫秒
91.
Yoshitake T Ichinose F Yoshida H Todoroki K Kehr J Inoue O Nohta H Yamaguchi M 《Biomedical chromatography : BMC》2003,17(8):509-516
A highly sensitive, selective and simple method is described for the determination of histamine by high-performance liquid chromatography (HPLC) with fluorescence detection. The method is based on an intramolecular excimer-forming fluorescence derivatization of histamine with 4-(1-pyrene)butyric acid N-hydroxysuccinimide ester (PSE), followed by reversed-phase HPLC. Histamine, having two amino moieties in a molecule, was converted to the dipyrene-labeled derivative by reaction with PSE. The derivative afforded intramolecular excimer fluorescence (450-540 nm), which can clearly be discriminated from the monomer fluorescence (370-420 nm) emitted from PSE. Typically, a 10 micro L sample solution was mixed with 100 micro L of derivatization reagent solution, which was a mixture of 0.5 mm PSE in acetonitrile and 0.5 mm potassium carbonate in water (8:2, v/v). The derivatization was carried out at 100 degrees C for 90 min. The PSE derivative of histamine could be separated by reversed-phase ODS column with isocratic elution using acetonitrile:water (82:18, v/v) containing 0.03% triethylamine. The detection limit (singnal-to-noise ratio = 3) of histamine was 0.5 fmol for a 30 micro L injection. The method was successfully applied to the determination of histamine in human urine, and had enough selectivity and sensitivity for urinary histamine quantification. 相似文献
92.
Gold nanoparticles located at the interface of anatase/rutile TiO2 particles as active plasmonic photocatalysts for aerobic oxidation 总被引:1,自引:0,他引:1
Tsukamoto D Shiraishi Y Sugano Y Ichikawa S Tanaka S Hirai T 《Journal of the American Chemical Society》2012,134(14):6309-6315
Visible-light irradiation (λ > 450 nm) of gold nanoparticles loaded on a mixture of anatase/rutile TiO(2) particles (Degussa, P25) promotes efficient aerobic oxidation at room temperature. The photocatalytic activity critically depends on the catalyst architecture: Au particles with <5 nm diameter located at the interface of anatase/rutile TiO(2) particles behave as the active sites for reaction. This photocatalysis is promoted via plasmon activation of the Au particles by visible light followed by consecutive electron transfer in the Au/rutile/anatase contact site. The activated Au particles transfer their conduction electrons to rutile and then to adjacent anatase TiO(2). This catalyzes the oxidation of substrates by the positively charged Au particles along with reduction of O(2) by the conduction band electrons on the surface of anatase TiO(2). This plasmonic photocatalysis is successfully promoted by sunlight exposure and enables efficient and selective aerobic oxidation of alcohols at ambient temperature. 相似文献
93.
Yuki Arakawa Hiroki Kuwahara Masatoshi Tokita Gen-ichi Konishi Hideto Tsuji 《Molecular Crystals and Liquid Crystals》2018,662(1):197-207
ABSTRACTWe present a new fabrication approach to achieve a high birefringence film by means of photopolymerization based on an alkylthio-containing rod-like liquid crystalline molecule exhibiting large temperature dependence of birefringence. We designed a new reactive mesogen having alkylthio linkages (BPM–S). It was found that BPM–S had a larger increment of birefringence with decreasing temperature, relative to commercially available alkoxy analog LC242. This result could be thought to be due to enhanced intermolecular attractive interaction for an alkylthio mesogen implied by the proximity of laterally neighboring molecules and cybotactic nematic tendency based on wide-angle X-ray measurement. The uniaxially-aligned photo-polymerized film for BPM–S showed higher birefringence than that for LC 242. 相似文献
94.
95.
This paper discusses the straight-through type labyrinth seal. This labyrinth seal is used for axial flow fans, which h ave
an outer ring at the blade tip to seal the clearance between the ring tip and the fan shroud, in order to prevent the reverse
flow or leakage. These fans are used for the cooling of automobile radiators . In these cases, the labyrinth seal is used
in an extremely low static pressure difference and a large clearance . A significant decrease of the leakage rate was reported
even when the labyrinth seal rotated in comparatively low speed in this unique condition according to the authors’ former
report. However, this phenomen on is differ ent from past research. Further more the cause of th is phenomenon has not been
determined. Therefore, the internal flow was depicted with Computational Fluid Dynamics (CFD) in or der to clarify the ca
use of this phenomenon. The results of CFD show that the leakage rate decreases significantly because the carry -over flow
is intercepted in the expansion groove. This is the newly discovered phenomenon which occurs under the unique condition of
an extremely low differential pressure. It has not been pointed out before as the reason why the rotation decreases the leakage
rate. 相似文献
96.
97.
Umakoshi K Yamasaki T Fukuoka A Kawano H Ichikawa M Onishi M 《Inorganic chemistry》2002,41(16):4093-4095
Treatment of pyridine-2-thiol (pytH) with H(2) (60 atm) in the presence of 5-methylpyridine-2-thiolate (5-mpyt)-bridged dinuclear Pt(III), Pt(II), or Pd(II) complexes (1 mol %) in DMF at 150 degrees C for 72 h leads to the formation of pyridine in 3-51% yield. From the (1)H NMR study of the exchange reactions and of the products under D(2) pressure, it is suggested that the catalytic reaction involves bimetallic activation of the pyt ligand followed by the liberation of pyridine and H(2)S. 相似文献
98.
Toriya S Tamura Y Takei T Fuji M Watanabe T Chikazawa M 《Journal of colloid and interface science》2002,255(1):171-176
The silica-pillared derivatives from kanemite (NaHSi(2)O(5).3H(2)O) were prepared by intercalation of dialkyldimethylammonium (DADMA) ion and pillaring with tetraethylorthosilicate. The formation of silica pillars between the silicate sheets was demonstrated by X-ray diffraction, (29)Si CP/MAS NMR, and TEM observation. The basal spacing depended on the chain length of DADMA. Nitrogen adsorption study showed that the specific surface area was enlarged over 1000 m(2) g(-1) by the pillaring and that the pore size was in the micropore region. Water and benzene adsorption isotherms revealed that the surface properties of the pillared derivatives show hydrophobic character. 相似文献
99.
The relationship among the Wigner crystal, charge ordering, and the Mott insulator is studied by the path-integral renormalization group method in two-dimensional systems with long-range Coulomb interaction. In contrast to the insensitivity of the Hartree-Fock results, the stability of the solid drastically decreases with the decrease in the lattice commensurability. The transition to liquid occurs at the electron gas parameter r(s) approximately 2 for the filling n=1/2, showing a large reduction from r(s) approximately 35 in the continuum limit. A correct account of quantum fluctuations is crucial to understanding the charge-order stability generally observed only at simple fractional fillings and the nature of quantum liquids away from them. 相似文献
100.
A system of q-Painlevé type equations with multi-time variables t
1,...,t
M
is obtained as a similarity reduction of the N-reduced q-KP hierarchy. This system has affine Weyl group symmetry of type
. Its rational solutions are constructed in terms of q-Schur functions. 相似文献