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排序方式: 共有825条查询结果,搜索用时 15 毫秒
811.
Iruthayaraj J Chernyy S Lillethorup M Ceccato M Røn T Hinge M Kingshott P Besenbacher F Pedersen SU Daasbjerg K 《Langmuir : the ACS journal of surfaces and colloids》2011,27(3):1070-1078
This work features the controllability of surface-initiated atom transfer radical polymerization (SI-ATRP) of methyl methacrylate, initiated by a multilayered 2-bromoisobutyryl moiety formed via diazonium chemistry. The thickness as a function of polymerization time has been studied by varying different parameters such as the bromine content of the initiator layer, polarity of reaction medium, ligand type (L), and the ratio of activator (Cu(I)) to deactivator (Cu(II)) in order to ascertain the controllability of the SI-ATRP process. The variation of thickness versus surface concentration of bromine shows a gradual transition from mushroom to brush-type conformation of the surface anchored chains in both polar and nonpolar reaction medium. Interestingly, it is revealed that very thick polymer brushes, on the order of 1 μm, can be obtained at high bromine content of the initiator layer in toluene. The initial polymerization rate and the overall final thickness are higher in the case of nonpolar solvent (toluene) compared to polar medium (acetonitrile or N,N-dimethylformamide). The ligand affects the initial rate of polymerization, which correlates with the redox potentials of the pertinent Cu(II)/Cu(I) complexes (L = Me(6)TREN, PMDETA, and BIPY). It is also observed that the ability of polymer brushes to reinitiate depends on the initial thickness and the solvent used for generating it. 相似文献
812.
Konosu Y Matsumoto H Tsuboi K Minagawa M Tanioka A 《Langmuir : the ACS journal of surfaces and colloids》2011,27(24):14716-14720
This letter reports the enhancing effects of a nanofiber network structure on stimuli-responsive wettability switching. Thermoresponsive coatings composed of nanofibers were prepared by electrospinning from thermoresponsive polymer poly(N-isopropylacrylamide) (PNIPAAm). The nanofiber coatings showed a large amplitude of thermoresponsive change in the wettability from hydrophilic to hydrophobic states compared to a smooth cast film. In particular, the combination of the surface chemistry and unique topology of the electrospun nanofiber coatings enables a transition from the Wenzel state to the metastable Cassie-Baxter state with an increase in temperature and consequently an enhanced amplitude of change in the water contact angles: the apparent contact angle differences between 25 and 50 °C are Δθ*(25-50?°C?)= 108 and 10° for the nanofiber coatings with a diameter of 830 nm and a smooth cast film, respectively. The fabrication of the 3D nanofiber network structure by electrospinning from stimuli-responsive materials is a promising option for highly responsive surfaces in wettability. 相似文献
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814.
掺入Eu的钛酸钡纳米晶陶瓷材料制备与电子结构特征 总被引:1,自引:0,他引:1
以Eu2O3、TiO2和BaCO3为原材料,在高温高压的极端条件下(4.0GPa,1090℃)采用固相反应法制备了结构均匀的新陶瓷材料Ba1-xEuxTiO3(x=0.1-0.4),样品显示灰黑色。当x增加到0.5时,出现ABO3型钙钛矿相和Eu2Ti2O7焦绿石相共存。X射线衍射图样显示Eu离子对A位Ba离子的均匀替代。并随着Eu含量的增加,结构向高对称性转变。通过对X射线衍射数据计算,表明材料结晶在平均粒度为几十纳米的数量级。X射线电子能谱(XPS)分析说明:在高压的作用下,Eu^3 离子部分被还原,在晶体结构中以Eu^3 离子(4f^6)和亚稳态Eu^2 离子(4f^7终态构形)稳定共存。同时在样品表面存在大量的吸附氧。Ba1-xEuxTiO3材料的电中性由亚稳态Eu^2 离子和吸附氧(O^-)共同补偿。 相似文献
815.
Large grain niobium has the potential of simplifying the production sequence and consequently reducing the cost of the superconducting RF cavities for ILC. To investigate the feasibility of fabrication and the possibility to achieve high gradient by large grain cavities, two 1.3GHz cavities were made of China large grain niobium and a series of vertical tests were carried out following several different
surfaces treatment procedures. Two cavities have both reached the high
gradient of more than 43MV/m repeatedly and the maximum accelerating field of 47.9MV/m has been achieved by China large grain niobium. This paper introduces the features of the fabrication and surface treatments on the large grain cavities and presents the preliminary results of the research. 相似文献
816.
Matsui F Matsushita T Kato Y Hashimoto M Inaji K Guo FZ Daimon H 《Physical review letters》2008,100(20):207201
Up until now there has been no direct method for detecting the electronic and magnetic structure of each atomic layer at the surface, which is an essential analysis technique for nanotechnology. For this purpose, we have developed a new method, diffraction spectroscopy, based on the photon energy dependence of the angular distribution of Auger electron emission. We have applied this method to analyze the magnetic structure of a Ni ultrathin film on a Cu(001) surface around the spin reorientation transition. Atomic-layer resolved x-ray absorption and magnetic circular dichroism spectra were obtained. Surface and interior core-level shifts and magnetic moments are determined for each atomic layer individually. 相似文献
817.
818.
819.
820.