全文获取类型
收费全文 | 441篇 |
免费 | 2篇 |
国内免费 | 2篇 |
专业分类
化学 | 327篇 |
晶体学 | 7篇 |
力学 | 4篇 |
数学 | 10篇 |
物理学 | 97篇 |
出版年
2022年 | 3篇 |
2021年 | 3篇 |
2020年 | 3篇 |
2019年 | 3篇 |
2018年 | 4篇 |
2017年 | 4篇 |
2016年 | 7篇 |
2015年 | 3篇 |
2014年 | 8篇 |
2013年 | 19篇 |
2012年 | 18篇 |
2011年 | 18篇 |
2010年 | 13篇 |
2009年 | 11篇 |
2008年 | 21篇 |
2007年 | 18篇 |
2006年 | 22篇 |
2005年 | 25篇 |
2004年 | 17篇 |
2003年 | 18篇 |
2002年 | 28篇 |
2001年 | 18篇 |
2000年 | 8篇 |
1999年 | 6篇 |
1998年 | 5篇 |
1997年 | 5篇 |
1996年 | 9篇 |
1995年 | 7篇 |
1993年 | 9篇 |
1992年 | 8篇 |
1991年 | 4篇 |
1990年 | 5篇 |
1989年 | 4篇 |
1988年 | 6篇 |
1987年 | 5篇 |
1986年 | 4篇 |
1985年 | 8篇 |
1984年 | 6篇 |
1983年 | 3篇 |
1982年 | 11篇 |
1981年 | 7篇 |
1980年 | 7篇 |
1979年 | 6篇 |
1978年 | 6篇 |
1977年 | 8篇 |
1976年 | 3篇 |
1975年 | 3篇 |
1974年 | 4篇 |
1967年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有445条查询结果,搜索用时 15 毫秒
41.
Conductive polymer three-dimensional microstructures were photofabricated utilizing the two-photon absorption of a sensitizer
dye. The resulting three-dimensional structures were excised from the transparent polymer sheet using a micro-manipulator.
The processing precisions for the vertical direction of the conductive polymer three-dimensional microstructure obtained in
the transparent polymer sheet were evaluated in the present study. As a result, for the configurations of the obtained polypyrrole
line deposition, the line height/line width ratios were around 5: 1; this ratio is higher than that of other UV resin works
(h: w 2:4–3: 1) and the cross section distortion is not negligible for maintaining the higher reproducibility of the photofabrication. 相似文献
42.
Nishizuka T Fujita Y Sato Y Nakano A Kakino A Ohshima S Kanda T Yoshimoto R Sawamura T 《Proceedings of the Japan Academy. Series B, Physical and biological sciences》2011,87(3):104-113
Lectin-like oxidized LDL receptor-1 (LOX-1) is an endothelial receptor for oxidized LDL (oxLDL) and plays multiple roles in the development of cardiovascular diseases. We screened more than 400 foodstuff extracts for identifying materials that inhibit oxLDL binding to LOX-1. Results showed that 52 extracts inhibited LOX-1 by more than 70% in cell-free assays. Subsequent cell-based assays revealed that a variety of foodstuffs known to be rich in procyanidins such as grape seed extracts and apple polyphenols, potently inhibited oxLDL uptake in Chinese hamster ovary (CHO) cells expressing LOX-1. Indeed, purified procyanidins significantly inhibited oxLDL binding to LOX-1 while other ingredients of apple polyphenols did not. Moreover, chronic administration of oligomeric procyanidins suppressed lipid accumulation in vascular wall in hypertensive rats fed with high fat diet. These results suggest that procyanidins are LOX-1 inhibitors and LOX-1 inhibition might be a possible underlying mechanism of the well-known vascular protective effects of red wine, the French Paradox. 相似文献
43.
We present a hierarchy of semidefinite programming (SDP) relaxations for solving the concave cost transportation problem (CCTP), which is known to be NP-hard, with p suppliers and q demanders. In particular, we study cases in which the cost function is quadratic or square-root concave. The key idea of our relaxation methods is in the change of variables to CCTPs, and due to this, we can construct SDP relaxations whose matrix variables are of size O((min {p, q}) ω ) in the relaxation order ω. The sequence of optimal values of SDP relaxations converges to the global minimum of the CCTP as the relaxation order ω goes to infinity. Furthermore, the size of the matrix variables can be reduced to O((min {p, q}) ω-1 ), ω ≥ 2 by using Reznick’s theorem. Numerical experiments were conducted to assess the performance of the relaxation methods. 相似文献
44.
45.
C.H. Chen A. Saiki N. Wakiya K. Shinozaki N. Mizutani 《Applied Physics A: Materials Science & Processing》2002,74(5):693-697
The structural correlations including the lattice constants and the mosaic dispersions between CeO2 and yttria-stabilized ZrO2 (YSZ) in CeO2/YSZ/Si(001) heteroepitaxial films have been investigated by out-of-plane and in-plane X-ray-diffraction techniques. The distinct
linear correlations of the full width at half-maximum (FWHM) of the ω scan between CeO2 and YSZ have been found in both directions. CeO2 always has a 0.7° lower FWHM of the ω scan than YSZ in the out-of-plane direction, but has a 2.6° higher FWHM in the in-plane
direction. A possible relationship between the out-of-plane and in-plane FWHMs of the ω scans has been demonstrated with a
lattice-rotation model. Besides, the lattice constants of CeO2 are dependent on the FWHMs of the YSZ ω scans: as the FWHM is below 3.5°, CeO2 has a tetragonal distortion, and as the FWHM is higher than 3.5°, CeO2 exhibits a cubic structure without distortion. The results are of great interest, both for the fundamental understanding
of the film-growth mechanisms and for potential applications.
Received: 11 September 2000 / Accepted: 5 June 2001 / Published online: 30 August 2001 相似文献
46.
Recently, it has been suggested that natural working fluids, such as CO2, hydrocarbons, and their mixtures, could provide a long-term alternative to fluorocarbon refrigerants. (Vapour + liquid) equilibrium (VLE) data for these fluids are essential for the development of equations of state, and for industrial process such as separation and refinement. However, there are large inconsistencies among the available literature data for (CO2 + isobutane) binary mixtures, and therefore provision of reliable and new measurements with expanded uncertainties is required. In this study, we determined precise VLE data using a new re-circulating type apparatus, which was mainly designed by Akico Co., Japan. An equilibrium cell with an inner volume of about 380 cm3 and two optical windows was used to observe the phase behaviour. The cell had re-circulating loops and expansion loops that were immersed in a thermostatted liquid bath and air bath, respectively. After establishment of a steady state in these loops, the compositions of the samples were measured by a gas chromatograph (GL Science, GC-3200). The VLE data were measured for CO2/propane and CO2/isobutane binary mixtures within the temperature range from 300 K to 330 K and at pressures up to 7 MPa. These data were compared with the available literature data and with values predicted by thermodynamic property models. 相似文献
47.
Ogawa T Hattori H Kaneko R Ito K Iwai M Mizutani Y Arinobu T Ishii A Seno H 《Analytical and bioanalytical chemistry》2011,400(7):1959-1965
In this report, a high-throughput and sensitive method for analysis of eight central-acting muscle relaxants in human plasma
by ultra-performance liquid chromatography–tandem mass spectrometry (UPLC-MS/MS) in the positive and negative ionization modes
using tolbutamide as internal standard is presented. After pretreatment of a plasma sample by solid-phase extraction with
an Oasis HLB cartridge, muscle relaxants were analyzed by UPLC with Acquity UPLC BEH C18 column and Acquity TQD tandem quadrupole mass spectrometer equipped with an electrospray ionization interface. The calibration
curves for muscle relaxants spiked into human plasma equally showed good linearities in the nanogram per milliliter order
range. The detection limits (signal-to-noise ratio = 3) was as low as 0.1–2 ng/mL. The method gave satisfactory recovery rates,
accuracy, and precision for quality control samples spiked with muscle relaxants. To further validate the present method,
250 mg of chlorphenesin carbamate was orally administered to a healthy male volunteer, and the concentrations of chlorphenesin
carbamate in plasma were measured 0.5, 1, 2, 4, 6, and 8 h after dosing; their concentrations in human plasma were between
0.62 and 2.44 μg/mL. To our knowledge, this is the first report describing simultaneous analysis of over more than two central-acting
muscle relaxants by liquid chromatography–tandem mass spectrometry. This has been realized by the capability of our instrument
for simultaneous multiple reaction monitoring of the target compounds in both positive and negative ionization modes. Therefore,
the present method seems very useful in forensic and clinical toxicology and pharmacokinetic studies. 相似文献
48.
Fukushima M Mizutani Y Maeno S Zhu Q Kuramitz H Nagao S 《Molecules (Basel, Switzerland)》2011,17(1):48-60
The influence of halogen substituents on the catalytic oxidation of 2,4,6-trihalogenated phenols (TrXPs) by iron(III)-porphyrin/KHSO? catalytic systems was investigated. Iron(III)-5,10,15,20-tetrakis(p-hydroxyphenyl)porphyrin (FeTHP) and its supported variants were employed, where the supported catalysts were synthesized by introducing FeTHP into hydroquinone-derived humic acids via formaldehyde poly-condensation. F (TrFP), Cl (TrCP), Br (TrBP) and I (TrIP) were examined as halogen substituents for TrXPs. Although the supported catalysts significantly enhanced the degradation and dehalogenation of TrFP and TrCP, the oxidation of TrBP and TrIP was not enhanced, compared to the FeTHP catalytic system. These results indicate that the degree of oxidation of TrXPs is strongly dependent on the types of halogen substituent. The order of dehalogenation levels for halogen substituents in TrXPs was F > Cl > Br > I, consistent with their order of electronegativity. The electronegativity of a halogen substituent affects the nucleophilicity of the carbon to which it is attached. The levels of oxidation products in the reaction mixtures were analyzed by GC/MS after extraction with n-hexane. The most abundant dimer product from TrFP via 2,6-difluoroquinone is consistent with a scenario where TrXP, with a more electronegative halogen substituent, is readily oxidized, while less electronegative halogen substituents are oxidized less readily by iron(III)-porphyrin/KHSO? catalytic systems. 相似文献
49.
This paper describes the measurement of average strain, strain distribution and vibration of a cantilever beam made of Carbon
Fiber Reinforced Plastics (CFRP), using a single Fibre Bragg Grating (FBG) sensor mounted on the beam surface. Average strain
is determined from the displacement of the peak wavelength of reflected spectrum from the FBG sensor. Two unstrained reference
FBG sensors were used to compensate for temperature drift. Measured strains agree with those measured by a resistance foil
strain gauge attached to the sample. Stress distributions are measured by monitoring the variation in the full width at half
maximum (FWHM) values of the reflected spectrum, using a proposed optical analytical model, described in the paper. FWHM values
were measured for both the cantilever test beam and for a reference beam, loaded using a four-point bending rig. The trend
of the stress distribution for the test beam matches with our analytical model, however with a relatively large noise present
in the experimentally determined data. The vibration of a cantilever beam was measured by temporal analysis of the peak reflection
wavelength. This technique is very stable as measurements are not affected by variations in the signal amplitude. Finally
an application of FBG sensors for damage detection of CFRP plates, by measuring the natural frequency, is demonstrated. With
small defects of different sizes applied to the CFRP plate, the natural frequency decreased with damage size. 相似文献
50.
Yukihiro Okada Manabu Mizutani Fuyuhiko Ishii Jun Nishimura 《Tetrahedron letters》1997,38(52):5347-9016
The modification of title compounds to chiral receptors and their characterization are reported. The two synthetic methods were developed. The racemates obtained could be resolved to each stable enantiomer by a chiral HPLC column. Chiral calixarenes were designed as the receptors with planar chirality. The (−)-receptor strongly forms 1:1 complex with (R)-(+)--phenylethylammonium picrate. 相似文献