全文获取类型
收费全文 | 568篇 |
免费 | 27篇 |
国内免费 | 3篇 |
专业分类
化学 | 455篇 |
晶体学 | 11篇 |
力学 | 19篇 |
数学 | 35篇 |
物理学 | 78篇 |
出版年
2023年 | 3篇 |
2022年 | 4篇 |
2021年 | 3篇 |
2020年 | 2篇 |
2019年 | 11篇 |
2018年 | 4篇 |
2017年 | 8篇 |
2016年 | 10篇 |
2015年 | 16篇 |
2014年 | 21篇 |
2013年 | 21篇 |
2012年 | 15篇 |
2011年 | 38篇 |
2010年 | 19篇 |
2009年 | 20篇 |
2008年 | 31篇 |
2007年 | 36篇 |
2006年 | 29篇 |
2005年 | 39篇 |
2004年 | 50篇 |
2003年 | 22篇 |
2002年 | 35篇 |
2001年 | 8篇 |
2000年 | 6篇 |
1999年 | 9篇 |
1998年 | 5篇 |
1997年 | 4篇 |
1996年 | 11篇 |
1995年 | 3篇 |
1994年 | 6篇 |
1993年 | 5篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1989年 | 4篇 |
1988年 | 5篇 |
1987年 | 6篇 |
1986年 | 2篇 |
1985年 | 6篇 |
1984年 | 13篇 |
1983年 | 10篇 |
1982年 | 11篇 |
1981年 | 9篇 |
1980年 | 10篇 |
1979年 | 3篇 |
1978年 | 5篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1975年 | 4篇 |
1972年 | 1篇 |
1966年 | 2篇 |
排序方式: 共有598条查询结果,搜索用时 0 毫秒
91.
Sumio Kato Takuya Yoshizawa Nobuhiro Kakuta Shinya Akiyama Masataka Ogasawara Takashi Wakabayashi Yuunosuke Nakahara Shinichi Nakata 《Research on Chemical Intermediates》2008,34(8-9):703-708
Apatite-type silicate supported precious metal catalysts were prepared and investigated for their catalytic activity in selective catalytic NO reduction. Single-phase La9.33Si6O26 and La8.33ASi6O25.5 (A=Ca, Sr, Ba) were obtained by a sol-gel method. Pd/La9.33Si6O26 catalyst exhibited high activity for oxidation of C3H6, comparable to Pd/Al2O3 catalyst, although the specific surface area of La9.33Si6O26 was lower than that of Al2O3. In addition, Pt/La9.33Si6O26 catalyst exhibited higher activity for selective catalytic reduction of NO than Pt/Al2O3 catalyst. Substitution of Ba2+ for La3+ of La9.33Si6O26 led to increased catalytic activity at low temperature. 相似文献
92.
Nakamura S Nakashima H Sugimoto H Sano H Hattori M Shibata N Toru T 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(7):2145-2152
Enantioselective C--C bond formation to 2-pyridinesulfonylimines afforded products with good enantioselectivity. Dynamic induction of chirality on the sulfur by coordination of a chiral Lewis acid to the pyridine nitrogen and one of the prochiral sulfonyl oxygens induces enantioselectivity. Since the 2-pyridinesulfonyl group can easily be removed after the reaction, it acts not only as an activating group but also as an efficient stereocontroller. 相似文献
93.
Size‐Dependence of the Activity of Gold Nanoparticle‐Loaded Titanium(IV) Oxide Plasmonic Photocatalyst for Water Oxidation 下载免费PDF全文
Miwako Teranishi Masataka Wada Dr. Shin‐ichi Naya Prof. Hiroaki Tada 《Chemphyschem》2016,17(18):2813-2817
Mesoporous TiO2 nanocrystalline film was formed on fluorine‐doped tin oxide electrode (TiO2/FTO) and gold nanoparticles (NPs) of different sizes were loaded onto the surface with the loading amount kept constant (Au/TiO2/FTO). Visible‐light irradiation (λ>430 nm) of the Au/TiO2/FTO photoanode in a photoelectrochemical cell with the structure of photoanode|0.1 m NaClO4 aqueous solution|Ag/AgCl (reference electrode)|glassy carbon (cathode) leads to the oxidation of water to oxygen (O2). We show that the visible‐light activity of the Au/TiO2/FTO anode increases with a decrease in Au particle size (d) at 2.9≤d≤11.9 nm due to the enhancement of the charge separation and increasing photoelectrocatalytic activity. 相似文献
94.
The photoinduced electron-transfer reduction of cup-stacked carbon nanotubes (CSCNTs) with 1-benzyl-1,4-dihydronicotinamide dimer [(BNA)2] results in the electrostatic destacking of CSCNTs to afford CSCNTs with uniform size. 相似文献
95.
Determination of vanillin and related flavor compounds in cocoa drink by capillary electrophoresis 总被引:1,自引:0,他引:1
In the first part of this study, the stability of five terpenes (alpha-pinene, limonene, camphor, citronellol, and carvacrol) under subcritical water conditions was investigated. The stability studies were carried out at four different temperatures (100, 150, 200, and 250 degrees C) with two different heating times (30 and 300 min). When water temperature was increased, the degradation of terpenes became more serious. Prolonged exposure time to each heating temperature also caused decreased terpene stability. The terpene recoveries were determined by conducting subcritical water extraction of sand spiked with terpenes. The recoveries are typically around 70 to 80% for extractions at 100 degrees C. Terpene recoveries were decreased with increasing water temperature due to poorer stability of terpenes. After the degradation and recovery studies, basil and oregano leaves were extracted using water at both 100 and 150 degrees C. The concentrations of each individual terpene in the water extract generally ranged from trace quantity to 65 microg terpene/g herb. However, the concentration of carvacrol in the oregano-water extract at 150 degrees C was found to be as high as 4270 microg carvacrol/g oregano. 相似文献
96.
Suzuki Y Okonogi M Yamauchi K Kurosu H Tansho M Shimizu T Saitô H Asakura T 《The journal of physical chemistry. B》2007,111(30):9172-9178
beta-Strand peptides are known to assemble into either antiparallel (AP) or parallel (P) beta-sheet forms which are very important motifs for protein folding and fibril formations occurring in silk fibroin or amyloid proteins. Well-resolved 1H NMR signals including NH protons were observed for alanine tripeptides (Ala)3 with the AP and P structures as well as (Ala)n (n = 4-6) by high-field/fast magic-angle spinning NMR. Amide NH and amino NH3+ 1H signals of (Ala)3 with the P structure were well resonated at 7.5 and 8.9 ppm, respectively, whereas they were not resolved for the AP structure. Notably, NH 1H signals of (Ala)3 and (Ala)4 taking the P structure are resonated at higher field than those of the AP structure by 1.0 and 1.1 ppm, respectively. Further, NH 15N signals of (Ala)3 with the AP structure were resonated at lower field by 2 to 5 ppm than those of (Ala)3 with the P structure. These relative 1H and 15N hydrogen bond shifts of the P structure with respect to those of the AP structure are consistent with the relative hydrogen bond lengths of the interstrand N-H...O=C bonds. Distinction between the two crystallographically independent chains present in the AP and P structures was feasible by 15N chemical shifts but not by 1H chemical shifts because of insufficient spectral resolution in the latter. Calculated 1H and 15N shielding constants by density functional theory are generally consistent with the experimental data, although some discrepancies remain depending upon the models used. 相似文献
97.
Various N-alkylsaccharins were easily prepared in moderate to good yields by the reaction of N-alkyl(o-methyl)arenesulfonamides with (diacetoxyiodo)benzene in the presence of iodine under irradiation with a tungsten lamp (W-hν). On the other hand, irradiation of N-alkyl(o- methyl)arenesulfonamide derivatives bearing various subslituents on the aromatic ring with a high- pressure mercury lamp (Hg-hν), in the presence of (diacetoxyiodo)benzene and iodine gave the corresponding N-alkyl-1,2-benzisothiazoline-3-one-1-oxide derivatives in moderate yields, together with N-alkyl-1,2-benzisothiazoline-3-one-1,1-dioxide (saccharin) derivatives. 相似文献
98.
Seiichi Yamamoto Shuji Koyama Chiyo Yamauchi-Kawaura Masataka Komori 《Optical Review》2017,24(3):428-435
It is commonly thought that UV or visible-light luminescence imaging of biological subjects during X-ray irradiation at the energy below 120 keV is impossible because the secondary electrons produced in this energy range do not emit Cerenkov light. Contrary to this consensus, we found UV or visible-light luminescence imaging of the subjects were possible with X-ray irradiations of this energy range. We placed one of the biological subjects in a black box; visible-light luminescence images were measured with a high-sensitivity, cooled charge coupled device (CCD) camera during X-ray irradiation at energy below 120 keV. We also conducted the imaging of air without subjects during irradiation of the same X-ray. The biological subjects emitted visible-light luminescence, and the imaging was possible with the irradiation of the X-ray below 120 keV. The luminescence images were observed in only the X-ray irradiated areas. Also air luminescence images could be obtained and the intensity of the luminescence measured from the images was proportionally increased with the exposure dose. UV or visible-light luminescence imaging of biological subjects was possible during X-ray irradiations lower energy than the Cerenkov-light threshold. The phenomenon was different from general X-ray fluorescence because wavelength of the luminescence is UV or visible-light. The luminescence imaging method is promising for estimating the irradiated area with X-ray, which could be used for interventional radiology (IVR). Also air luminescence imaging would be applied to the exposure dose distribution measurements for X-ray of diagnostic X-ray systems. 相似文献
99.
We have investigated the influence of the magnetic field strength, shear rate, and rotational Brownian motion on transport coefficients such as viscosity and diffusion coefficient, and also on the orientational distributions of rodlike particles of a dilute colloidal dispersion. The rodlike particle is modeled as a magnetic spheroidal particle which has a magnetic moment normal to the particle axis; such a particle may typically be a hematite particle. In the present study, an external magnetic field is applied in the direction normal to the shear plane of a simple shear flow. The basic equation of the orientational distribution function has been derived from the balance of torques and solved numerically. The results obtained here are summarized as follows. Although the orientational distribution function shows a sharp peak in the shear flow direction for a very strong magnetic field, such a peak is not restricted to the field direction alone, but continues in every direction of the shear plane. This is due to the characteristic particle motion that the particle can rotate around the axis of the magnetic moment in the shear plane, although the magnetic moment nearly points to the magnetic field direction. This particle motion in the shear plane causes negative values of the viscosity due to the magnetic field. The viscosity decreases, attains a minimum value, and then converges to zero as the field strength increases. Additionally, the diffusion coefficient is significantly influenced by such characteristic particle motion in the shear plane for a strong magnetic field. 相似文献
100.
Yamamoto R Yamada T Taguchi M Miyakubo K Kato HS Munakata T 《Physical chemistry chemical physics : PCCP》2012,14(27):9601-9605
Dispersions of image potential states on a graphite surface (denoted IPS1) and on 1 monolayer (ML) film (denoted IPS2) of lead phthalocyanine (PbPc) are investigated by the micro-spot angle-resolved two-photon photoemission (micro-AR-2PPE) spectroscopy. On the graphite surface, whole dispersions of the two members of IPS1 (n = 1 and 2) are observed. The n = 1 IPS1 peak is weakly visible at energy higher than the vacuum level. The effective mass of an electron in the n = 1 IPS1 becomes slightly light at the high momentum region, suggesting the interaction between the IPS1 and the unoccupied σ-band of graphite. On the PbPc film, the IPS2 band forms a band gap and back-folds at the boundary of the Brillouin zone. A 1-dimensional Kronig-Penny model is used to reproduce the effective mass and the shift of binding energy. 相似文献