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71.
It is the first time that boron is determined in the presence of a little methanol by discoloring spectrophotometry in this paper. A russety product can be formed by the reaction between glycine (Gly) and sodium 1,2-naphthoquinone-4-sulfonate (NQS) in alkaline solution. When boron is added to the solution, the system will be discolored, and the addition of a little methanol will improve the discoloration. Beer's law is obeyed in the range of boron concentrations of 0.86-43.24 μg ml−1 at the maximal discoloring wavelength of 382 nm. The equation of linear regression is A = −0.07581-86.79186C (mol l−1), with a linearly correlation coefficient of 0.9979. The detection limit is 0.80 μg ml−1 and R.S.D. is 4.2%. The method is successfully applied to the determination of boron in pharmaceutical and biological samples. The average recoveries are in the range of 98.2-104.1%. Analytical results obtained with this novel method are satisfactory. 相似文献
72.
《Electroanalysis》2004,16(16):1285-1291
The electrochemical oxidation of the cysteine‐quinone adduct has been examined as a means of providing an electroanalytical cysteine specific detection protocol. The appliance of square‐wave voltammetry allowed 0.5 μM as a limit of detection. The effects of various biologically relevant interferences including other thiols were studied and found to present no change in the voltammetric profile. The practical applicability and efficiency of the methodology was probed through the determination of cysteine concentration in growth tissue medium. 相似文献
73.
Reginald B. Little 《Journal of Cluster Science》2003,14(2):135-185
The discovery, synthesis, characterization, and applicability of carbon nanotubes have produced tremendous excitement and interest among scientists and engineers. In particular, the use of these unique tubular nanostructures for new strong lightweight materials, nanoelectronics, fuel storage and cells, electron emitters and bio, scanning probe microscopy, and chemical sensing devices has created an intense effort to advance the synthesis so as to mass produce carbon nanotubes with control over diameter and helicity. The massive and controlled synthesis of this heralded nanostructure has been a great challenge. Although significant progress has advanced the preparation, more synthetic development is required. The syntheses have so far involved three main approaches: arc discharge vaporization, laser vaporization, and catalytic chemical vapor deposition. The synthetic trend has progressed to a point where further advancement with these techniques will require a better understanding of the mechanism of nucleation and growth. The mechanics of carbon nanotube nucleation and growth involve very complex and diverse phenomena occurring under extreme conditions and on the mesoscopic scale. As yet the detail mechanism is unknown. Difficulties with experimental probing and computational simulation have increased the mystery of this mechanism. This review presents an account of research on the synthesis of carbon nanotubes and the mechanism of formation. This overview includes all three mentioned synthetic approaches and hybrids thereof. On the basis of this broad account a comprehensive mechanism for carbon nanotube nucleation and growth naturally arises. This mechanism is qualitative and it hopes to inspire more quantitative exploration and synthetic advancement. 相似文献
74.
Classifying wine according to geographical origin via quadrupole-based ICP–mass spectrometry measurements of boron isotope ratios 总被引:1,自引:0,他引:1
The potential of quadrupole-based ICP–MS as a tool for B-isotopic analysis of wines and its usefulness in provenance determinations
were assessed. A precision of 0.1–0.25% RSD (corresponding to a relative standard deviation of the mean of three replicate
measurements of 0.06–0.12%) was sufficient to establish small differences in the B isotope ratios in wines from different
geographical origins. Each sample measurement was bracketed by measurements of a standard and mass bias drift correction made
by interpolation. Sample preparation was kept to a minimum to avoid possible fractionation. Dilution of the wine samples by
a factor of 100 with 0.65% HNO3 was found to reduce matrix-induced mass discrimination substantially. Wines from three wine-producing regions, Stellenbosch,
Robertson, and Swartland, in the Western Cape Province of South Africa, and wines from specific regions in France (Bergerac)
and Italy (Valpolicella) were analyzed by ICP–QMS for their B-isotopic compositions. It was concluded that the 11B/10B ratios can be used to characterize wines from different geographical origins. Average 11B/10B ratios in red wines from South Africa (Stellenbosch), France (Bergerac), and Italy (Valpolicella) were found to differ by
between 0.5 and 1.5%. 相似文献
75.
76.
M. Sarah Mohlala 《Journal of organometallic chemistry》2006,691(22):4768-4772
A range of substituted ferrocenes were used as catalysts for the synthesis of multi-walled carbon nanotubes (MWCNTs) and carbon fibers (CFs). These products were obtained in the temperature range 800-1000 °C, in a reducing atmosphere of 5% H2 by pyrolysis of (CpR)(CpR′)Fe (R and R′ = H, Me, Et and COMe) in toluene solution. The effect of pyrolysis temperature (800-1000 °C), catalyst concentration (5 and 10 wt.% in toluene) and solution injection rate (0.2 and 0.8 ml/min) on the type and yield of carbonaceous product synthesized was investigated. Carbonaceous products formed include graphite film (mostly at high temperature; 900-1000 °C), carbon nanotubes and carbon fibers. The carbonaceous materials were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. The ferrocene ring substituents influenced both the CNT diameter and the carbon product formed. 相似文献
77.
The semiconductor properties of the interface TiO2/electrolyte in high organized porous oxide structures were analyzed by means of impedance spectroscopy near the flat band
potential. The impedance and capacitance studies performed on the as-anodized and thermally treated samples (anatase) indicate
the presence of a duplex structure formed by (1) the oxide at the bottom of the pores and (2) the walls of pores with different
donor densities and surface state concentrations. 相似文献
78.
Shidong Fei Jinhua Chen Shouzhuo Yao Guohong Deng Lihua Nie Yafei Kuang 《Journal of Solid State Electrochemistry》2005,9(7):498-503
Electroreduction of -glucose to form sorbitol on Zn/CNTs and Zn alloy/CNTs electrodes has been investigated in this paper. Carbon nanotubes (CNTs) used in this paper are grown directly on graphite disks by chemical vapor deposition. Zn and Zn alloy are electrodeposited on the activated CNTs/graphite electrode by pulse galvanostatic method. The micrographs of Zn/CNTs and Zn alloy/CNTs electrodes are characterized by scanning electron microscopy. The results show that the current efficiency of -glucose reduction on CNTs electrodes is much better than that on flat Zn electrodes. The order of the current efficiency on different electrodes is as follows: Zn/CNT (0.58) Zn–Fe/CNT (0.57)>Zn–Ni/CNT (0.43) Zn/graphite (0.42)>Zn (0.40). It indicates that CNTs have good potential application in electrosynthesis. Additionally, effects of some operating parameters, such as pH, temperature and -glucose concentration, on the current efficiency of -glucose reduction are also discussed. 相似文献
79.
《Electroanalysis》2005,17(20):1806-1815
The first example of using a copper microelectrode array for use in electroanalysis is explored and exemplified with the electroanalytical quantification of nitrate. The analytical approach is based upon the in situ deposition of copper at a boron‐doped diamond (BDD) microelectrode array. The immobilized copper layer is electrocatalytic for nitrate reduction and exhibits an analytically useful range from 1.2 to 124 μM with a marked selectivity for nitrate ion over nitrate, with a limit of detection of 0.76 μM. The analytical applicability was examined through standard addition determinations of nitrate in drinking and river water samples. 相似文献
80.
P.W. ZhuY.N. Zhao B. WangZ. He D.M. LiG.T. Zou 《Journal of solid state chemistry》2002,167(2):420-424
We present low stress cubic boron nitride (cBN) films with a transition layer deposited on the metal alloy substrates by tuned substrate radio-frequency magnetron sputtering. The films were characterized by Fourier transform infrared spectroscopy and transmission electron microscopy (TEM). The IR peak position of cubic boron nitride at 1006.3 cm−1, which is close to the stressless state, indicates that the film has very low internal stress. The TEM image shows that pure CBN phase exists on the surface of the film. Several phases of boron nitride were found at the medium implantation dose. It is believed that the transition from the low ordered phases to cBN phase occurred during implantation. 相似文献