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821.
Wanfei Cai Hanying Wu Xiaolan Wang Prof. Dr. Laicai Li Anmin Tian Ningbew Huang 《中国化学》2010,28(11):2137-2143
The interacting patterns and mechanism of the catechin and guanine have been investigated with the density functional theory B3LYP method by 6‐31G* basis set. Fourteen stable structures for the catechin‐guanine complexes have been found which form two hydrogen bonds at least. The results indicate that the complexes are mainly stabilized by the hydrogen bonding interactions. At the same time, the number and strength of hydrogen bond play a co‐determinant parts in the stability of the complexes which can form two or more hydrogen bonds. Theories of atoms in molecules (AIM) and natural bond orbital (NBO) have been adopted to investigate the hydrogen bonds involved in all systems. The interaction energies of all complexes have been corrected for basis set superposition error (BSSE), ranging from ?38.86 to ?14.56 kJ/mol. The results showed that the hydrogen bonding contributes to the interaction energies dominantly. The corresponding bonds stretching motions in all complexes are red‐shifted relative to that of the monomer, which is in agreement with experimental results. 相似文献
822.
采用脉冲激光烧蚀技术(PLA)在n型Si(100)单晶衬底上制备Tb-Si纳米颗粒。原子力显微镜(AFM)观察样品的表面形貌,发现样品表面是均匀分布的纳米颗粒,颗粒尺寸在10~20 nm之间,分布密度大约为6×1010/cm2。光电子能谱(XPS)及高分辨透射电镜(HRTEM)分析表明,纳米尺度的单晶硅化物颗粒的主要成分为Tb-Si及少量Tb-Si-O结构。室温下以荧光为激发光对样品的光致发光(photoluminescence)性能进行测试,结果表明样品在可见光区具有较强的发光现象,主要有4个发光峰,分别位于485,545,585和620 nm附近,这些发光峰主要由Tb3+中电子在不同能级之间的跃迁造成。 相似文献
823.
N, B, Si-tridoped mesoporous TiO2, together with N-doped, N, B-codoped and N, Si-codoped TiO2, was prepared by a modified sol–gel method. The samples were characterized by wide-angle X-ray diffraction (WAXRD), N2 adsorption–desorption, transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, UV–visible
adsorbance spectra (UV–vis) and X-ray photoelectron spectra (XPS). The N, B, Si-tridoped mesoporous TiO2 showed small crystallite size, large specific surface area (350 m2/g), uniform pore distribution (3.2 nm) and strong absorption in the visible light region. The photocatalytic activities of
the samples were evaluated by the photodegradation of 2,4-dichlorophenol (2,4-DCP) aqueous solution. The N, B, Si-tridoping
sample exhibited much higher photocatalytic activity compared with other synthesized photocatalysts. The high activity could
be attributed to the strong absorption in the visible light region, large specific surface area, small crystallite size, large
amount of surface hydroxyl groups, and mesoporosity. 相似文献
824.
Qiong He Tian Gan Dongyun Zheng ShengShui Hu 《Journal of Solid State Electrochemistry》2010,14(6):1057-1064
Simple and sensitive electrochemical method for the determination of nitrite, based on a nano-alumina-modified glassy carbon
electrode (GCE), is described. Nitrite yields a well-defined oxidation peak whose potential is 0.74 V at the nano-alumina-coated
GCE in 0.1 mol L−1 phosphate buffer (pH 5.0). Compared with bare GCE, the nano-alumina-modified GCE has evident catalytic effect towards the
oxidation of nitrite, and its peak current can be significantly enhanced. Some of the experimental parameters were optimized
for the determination of nitrite. The oxidation peak current was proportional to nitrite concentration in the range of 5.0 × 10−8–1.1 × 10−3 mol L−1, and a detection limit of 1.0 × 10−8 mol L−1 was obtained. This method has been successfully used to the determination of nitrite in sausage sample. Furthermore, results
obtained by the method have been compared with spectrophotometric method. 相似文献
825.
TiO2/organically modified silane organic–inorganic hybrid films doped with different disperse red 1 contents are prepared by combining
a low-temperature sol–gel method and a spin-coating process. Effects of the disperse red 1 content on the third-order nonlinear
and the planar waveguide properties of the hybrid films are also studied by a z-scan technique and a prism coupling technique.
Results indicate that the nonlinear refractive index of the hybrid films is negative, whose magnitude is of the order of 10−8 esu for the measured samples. It is suggested that both the thermal effect and the photoisomerization process contribute
to the third-order nonlinear optical properties of the hybrid films jointly. It is also found that the refractive index and
the thickness of the hybrid films decrease with an increase of the temperature as the independent variable. In addition to,
optical absorption properties of the hybrid films are characterized by UV–Visible spectroscopy. These results indicate that
the as-prepared hybrid films are promising candidates for photonic applications. 相似文献
826.
Yuguang Jin Yanqing Tian Weiwen Zhang Sei-Hum Jang Alex K.-Y. Jen Deirdre R. Meldrum 《Analytical and bioanalytical chemistry》2010,398(3):1375-1384
The relationship between bacteria and host phagocytic cells is key to the induction of immunity. To visualize and monitor
bacterial infection, we developed a novel bacterial membrane permeable pH sensor for the noninvasive monitoring of bacterial
entry into murine macrophages. The pH sensor was constructed using 2-dicyanomethylene-3-cyano-4,5,5-trimethyl-2,5-dihydrofuran
(TCF) as an electron-withdrawing group and aniline as an electron-donating group. A piperazine moiety was used as the pH-sensitive
group. Because of the strong electron-donating and -withdrawing units conjugated in the sensing moiety M, the fluorophore
emitted in the red spectral window, away from the autofluorescence regions of the bacteria. Following the engulfment of sensor-labeled
bacteria by macrophages and their subsequent merger with host lysosomes, the resulting low-pH environment enhances the fluorescence
intensity of the pH sensors inside the bacteria. Time-lapse analysis of the fluorescent intensity suggested significant heterogeneity
of bacterial uptake among macrophages. In addition, qRT-PCR analysis of the bacterial 16 S rRNA gene expression within single
macrophage cells suggested that the 16 S rRNA of the bacteria was still intact 120 min after they had been engulfed by macrophages.
A toxicity assay showed that the pH sensor has no cytotoxicity towards either E. coli or murine macrophages. The sensor shows good repeatability, a long lifetime, and a fast response to pH changes, and can be
used for a variety of bacteria. 相似文献
827.
A new stationary phase based on silica modified with 1-methyl-3-propylimidazolium chloride was synthesized and characterized
in this paper. A derivative of 1-methyl-3-propylimidazolium chloride was used to chemically modify the surface of silica particles
to act as the stationary phase for HPLC. The modified particles were characterized by Fourier Transform Infrared (FT-IR), 13C NMR spectroscopy and thermogravimetric analysis (TGA). The surface modification procedure rendered particles with a surface
coverage of 0.89 μmol/m2 of alkylimidazolium chloride. Columns packed with the modified silica and blank silica particles were tested under HPLC conditions.
Preliminary evaluation of the stationary phase for HPLC was performed using aromatic compounds as model compounds. The separation
mechanism appears to involve multiple interactions including ion exchange, hydrophobic and electrostatic interactions. 相似文献
828.
Igor Krupa Tomáš Nedelčev Dušan Račko Igor Lacík 《Journal of Sol-Gel Science and Technology》2010,53(1):107-114
The mechanical properties for silica hydrogel prepared at physiological conditions are reported in this paper. The mechanical
testing was performed in the compression mode determining the mechanical characteristics as a function of aging time in TRIS
buffer up to 14 days. In addition to a typically used gradient method for Young’s modulus determination from the stress–strain
curves, a new phenomenological model was proposed to describe the experimental data. The mechanical properties were stabilized
after 2 days of aging, which was concluded from an increase in Young’s modulus between 90 and 400 kPa, an increase in stress
at break between 50 and 100 kPa and by a decrease in relative deformation at break from 0.26 to 0.16. The height of samples
was constant in the first three days of aging followed by a decrease by ~20%. Dissolving of silica hydrogel characterized
through determination of silica content in TRIS buffer employing the molybdenum method was not found to be responsible for
this phenomenon. The phenomenological model is proposed to be used for a reliable evaluation of mechanical properties of silica
as well as other hydrogels exhibiting low Young’s modulus. 相似文献
829.
Repická Zuzana Moncol Jan Puchoňová Miroslava Jorík Vladimír Mikloš Dušan Lis Tadeusz Padělková Zdenka Mazúr Milan Valigura Dušan 《Structural chemistry》2010,21(5):1093-1102
Novel copper(II) X-salicylate complexes with N,N-diethylnicotinamide (dena) of the formula [Cu(RCOO)2(dena)2(H2O)2] (RCOO = 3-methylsalicylate anion (3-Mesal, 1), 4-methylsalicylate anion (4-Mesal, 2), 5-methylsalicylate anion (5-Mesal, 3), 5-methoxysalicylate anion (5-MeOsal, 4) or 4-methoxysalicylate anion (4-MeOsal, 5)), and complex [Cu(3-MeOsal)2(dena)2(H2O)2]∙2H2O (3-MeOsal = 3-methoxysalicylate anion (6)) have been prepared in the crystalline forms and characterized by spectroscopic methods (IR, Vis–UV, EPR). All the compounds
according to their composition (1–5) seem to possess octahedral copper(II) stereochemistry. The complex 1 has been prepared in two different forms. X-ray analyses of the complexes 1, 4, and 5 were carried out and they featured a tetragonal-bipyramidal geometry around the copper atoms. The tetragonal planes are created
by X-salicylate anions bonded to the copper(II) atoms via unidentate carboxylate oxygen atoms and the pyridine ring nitrogen
atoms of the neutral ligand N,N-diethylnicotinamide, while in axial positions are water molecules. The two forms of complex 1 present conformation polymorphs and supramolecular isomers. 相似文献
830.