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221.
Yuriy Garbovskiy 《Liquid crystals》2017,44(6):948-955
Typically, ionic species in thermotropic liquid crystals are nearly fully ionised. Therefore, the concentration of mobile ions practically does not depend on the temperature. Interestingly, the same liquid crystals doped with nanoparticles exhibit totally different behaviour. The concentration of mobile ions become temperature dependent. This paper reports the effects of the temperature on the concentration of ions in liquid crystal nanocolloids. Liquid crystals doped with both 100% pure and contaminated nanoparticles are considered. Regardless the ionic purity of nanodopants, the concentration of mobile ions in liquid crystal nanocolloids increases towards the saturation as their temperature goes up. The magnitude of this saturation level equals the initial concentration of ions in liquid crystals doped with 100% pure nanoparticles. The temperature induced release of ions by contaminated nanoparticles in liquid crystals increases the above-mentioned saturation level. While the dispersion of 100% pure nanoparticles in liquid crystals leads to the temperature-dependent purification only, the use of contaminated nanoparticles results in the temperature-driven switching between the purification and contamination regimes enabling thermal control of ions. 相似文献
222.
223.
Rebeca D. Gonçalves Sérgio Azevedo Fernando Moraes M. Machado 《International journal of quantum chemistry》2010,110(9):1778-1783
We have investigated, using first‐principles calculations, the role of a substitutional carbon atom on the geometric stability of boron nitride monolayers, nanotubes, and nanocones. It is shown that the formation of energy depends on the number of atoms for the monolayers and on the diameter for the tubes. It is also found, for the carbon‐doped boron nitride nanotubes, that the value for the strain energy approaches the one obtained for nondoped tubes with increasing diameter. For the structural stability, we have verified that the doping, which introduces an excess of nitrogen or boron, makes each structure more favorable in its reverse atmosphere, i.e., excess of nitrogen is more stable in a boron‐rich growth environment, whereas excess of boron is preferred in a nitrogen‐rich condition. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010 相似文献
224.
Luisa Célia Melo Djenaine De Souza Pedro de Lima‐Neto Adriana Nunes Correia 《Electroanalysis》2010,22(21):2502-2510
The highly boron‐doped diamond electrode (HBDD) combined with square wave voltammetry (SWV) was used in the development of an analytical procedure for diquat determination in potato and sugar cane samples and lemon, orange, tangerine and pineapple juices. Preliminary experiments realised in a medium of 0.05 mol L?1 Na2B4O7 showed the presence of two voltammetric peaks around ?0.6 V and around ?1.0 V vs. Ag/AgCl/Cl? 3.0 mol L?1, where the first peak could be successfully used for analytical proposes due the facility in the electrode surface renovation. After the experimental and voltammetric optimisation, the calculated detection and quantification limits were 1.6×10?10 mol L?1 and 5.3×10?10 mol L?1 (0.057 µg L?1 and 0.192 µg L?1, respectively), which are lower than the maximum residue limit established for fresh food samples by the Brazilian Sanitary Vigilance Agency. The proposed methodology was used to determine diquat residues in potato and sugar cane samples and lemon, orange, tangerine and pineapple juices and the calculated recovery efficiencies indicated that the proposed procedure presents higher robustness, stability and sensitivity, good reproducibility, and is very adequate for diquat determination in complex samples. 相似文献
225.
226.
Carolina Lourencetti Pilar Fernández Celia Prado Joan O. Grimalt 《Analytica chimica acta》2010,662(1):23-30
A method for the estimation of the human intake of trihalomethanes (THMs), namely chloroform, bromodichloromethane, dibromochloromethane and bromoform, during showering and bathing is reported. The method is based on the determination of these compounds in exhaled breath that is collected by solid adsorption on Tenax using a device specifically designed for this purpose. Instrumental measurements were performed by automatic thermal desorption coupled to gas chromatography with electron capture detection. THMs in exhaled breath samples were determined during showering and swimming pool attendance. The levels of these compounds in indoor air and water were also determined as reference for interpretation of the exhaled breath results. The THM concentrations in exhaled breath of the volunteers measured before the exposure experiments showed a close correspondence with the THMs levels in indoor air where the sampler was located. Limits of detection in exhaled breath were dependent on THM analytes and experimental sites. They ranged between 170 and 710 ng m−3 in the swimming pool studies and between 97 and 460 ng m−3 in the showering studies. Application of this method to THMs determination during showering and swimming pool activities revealed statistically significant increases in THMs concentrations when comparing exhaled breath before and after exposure. 相似文献
227.
土壤砷含量高光谱估算模型研究 总被引:2,自引:0,他引:2
以实验室内测取的土壤反射光谱为研究对象,利用PLSR方法建立反射光谱与土壤As含量之间的模型,通过交叉验证、估算检验建模精度,探讨利用反射光谱估算士壤As含量的可行性.通过比较不同光谱预处理方法、不同光谱分辨率和不同OM含量条件下建模、验证和估算结果.表明,MSC方法可以有效去除散射的影响而取得较好的结果(估算R2=0... 相似文献
228.
By using first-principles density functional theory, we investigate the charge distribution of a potassium-doped layered combined system of graphene and hexagonal boron nitride. Two configurations of potassium-doped hexagonal boron nitride layers on graphenes and the reverse geometry of graphenes on hexagonal boron nitride layers are considered. We find that the charge distribution exhibits different features in these two situations. In the former case, the outmost hexagonal boron nitride layer cannot screen the external charges offered by potassium atom completely and most of the transferred charges reside on the two bounding layers. In contrary, the outmost graphene layer near the potassium atom can accept almost all of the transferred charges and only a few of them stay at interior layers in the latter case. A more amazing result is that the characteristics of charge transfer are independent of the number of hexagonal boron nitride layers and graphenes. 相似文献
229.
Nusrat Lubna Gregory AunerRahul Patwa Hans HerfurthGolam Newaz 《Applied Surface Science》2011,257(10):4749-4753
Thin film materials are widely used in the fabrication of semiconductor microelectronic devices. In thin film deposition, cleanliness of substrate surface have become critically important as over 50% of yield losses in integrated circuit fabrication are caused by microcontamination [1]. There are many wafer cleaning techniques. The most successful approach for silicon wafer cleaning technique is RCA clean [2]. But for glass substrate it is still not known which procedure of cleaning is the best. This paper provides an understanding of the right way of glass wafer cleaning method, with a focus towards identifying good bond strength. Two wafer cleaning techniques have been used for cleaning glass substrates in the context of laser micro-joining of dissimilar substrates. First cleaning procedure involves two steps, first cleaning in acetone solution and then in DI water solution. After each step dried with N2. Second cleaning procedure involves four steps, first cleaning with 1% Alconox solution, second in DI water, third in acetone solution and finally in a methanol solution and dried with N2 after each step. Deposition of Ti thin film on top of these two types of substrate using DC magnetron sputtering method also showed better adhesion of Ti film on glass for the second type of cleaning method. Scanning electron microscopy (SEM) analyses of the lap shear tested failed surfaces for these two kinds of samples revealed strong bond for samples prepared by second cleaning method compared to first cleaning method. Characterization of these two sets of samples using X-ray photoelectron spectroscopy (XPS) has shown excellent contamination removal for the second cleaning method. This modification is believed to be due to reduction of carbon contamination. 相似文献
230.
Defang Duan Xiaoli Huang Changbo Chen Fubo Tian Kuo Bao Da Li Yunxian Liu Hongyu Yu Bingbing Liu Tian Cui 《ChemInform》2014,45(49):no-no
The high pressure crystal structure of BI3 with space group P21/c consisting of B2I6 dimers is determined using an ab initio evolutionary algorithm for crystal structure prediction in conjunction with density functional theory. 相似文献