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991.
X. T. Tao T. Watanabe D. C. Zou S. Shimoda H. Usui H. Sato S. Miyata 《Journal of Polymer Science.Polymer Physics》1995,33(16):2205-2210
The electric field-induced dynamic phase-matching of second harmonic generation (SHG) waveguide was demonstrated by using a main chain polyarylamine. The linear and nonlinear optical properties of this polymer are presented. The optimum phase-matching thickness was controlled by applying an electric field to the polymer waveguide. The effective phase-matching thickness variation induced by poling is about 0.025 μm that is six times larger than full width at the half-maximum (FWHM) of phase-matching thickness in conventional slab waveguide. The efficient phase-matched SHG was observed from a taperless slab wave-guide. The optical loss of poled polymer on glass substrate at 632.8 nm was 2.7 dB/cm. © 1995 John Wiley & Sons, Inc. 相似文献
992.
碘-四氯化碳萃取光度法间接测定食品中的痕量过氧化氢 总被引:5,自引:0,他引:5
在 p H1.0— 3.0稀硫酸介质中 ,一定的反应条件下 ,过氧化氢与碘化钾反应 ,释放出一定量的碘 ,建立了碘 -四氯化碳萃取光度法间接测定痕量过氧化氢。共存离子基本上不干扰测定 ,过氧化氢的检测限为0 .0 5 μg·m L-1;回收率在 94 %— 98%之间 ,结果令人满意 相似文献
993.
SiHx (x = 1, 2, 3) ions impact on Si(0 0 1)(1 × 1):H and Si(0 0 1)(2 × 1):H surfaces has been studied by classical molecular dynamic simulations, considering an energetic range for the impinging species from 5 to 15 eV. Despite the initial full H coverage a high sticking coefficient has been obtained for all the species under investigation. A considerable fraction of adsorption events causes H removal from the surface while for other simulations a soft landing mechanism of the ions has been observed. Few representative minima for SiH2/Si(0 0 1)(2 × 1):H were re-converged by ab initio calculations in order to check the reliability of our results. 相似文献
994.
In this paper, we study different strategies to stabilize and accelerate the column generation method, when it is applied specifically to the variable sized bin-packing problem, or to its cutting stock counterpart, the multiple length cutting stock problem. Many of the algorithms for these problems discussed in the literature rely on column generation, processes that are known to converge slowly due to primal degeneracy and the excessive oscillations of the dual variables. In the sequel, we introduce new dual-optimal inequalities, and explore the principle of model aggregation as an alternative way of controlling the progress of the dual variables. Two algorithms based on aggregation are proposed. The first one relies on a row aggregated LP, while the second one solves iteratively sequences of doubly aggregated models. Working with these approximations, in the various stages of an iterative solution process, has proven to be an effective way of achieving faster convergence. 相似文献
995.
We present a model of a new paramagnetic defect center which results from the interaction of atomic hydrogen with the MgO(1 0 0) surface. DFT calculations have been performed using periodic supercells and embedded cluster models where long-range polarization effects are included explicitly. The H atom promotes the creation of an oxygen vacancy (F center) by formation of the FS+(OH−) defect where an hydroxyl group is adsorbed near an electron trapped in an oxygen vacancy. This new center has some characteristics similar to those of the classical FS+ centers but a smaller formation energy; furthermore, being globally neutral, it can be treated also with supercell methods. 相似文献
996.
Review of proton conductors for hydrogen separation 总被引:1,自引:0,他引:1
There is a global push to develop a range of hydrogen technologies for timely adoption of the hydrogen economy. This is critical in view of the depleting oil reserves and looming transport fuel shortage, global warming, and increasing pollution. Molecular hydrogen (H2) can be generated by a number of renewable and fossil-fuel-based resources. However, given the high cost of H2 generation by renewable energy at this stage, fossil or carbon fuels are likely to meet the short- to medium-term demand for hydrogen. In view of this, effective technologies are required for the separation of H2 from a gas feed (by-products of coal or bio-mass gasification plants, or gases from fossil fuel partial oxidation or reforming) consisting mainly of H2 and CO2 with small quantities of other gases such as CH4, CO, H2O, and traces of sulphur compounds. Several technologies are under development for hydrogen separation. One such technology is based on ion transport membranes, which conduct protons or both protons and electrons. Although these materials have been considered for other applications, such as gas sensors, fuel cells and water electrolysis, the interest in their use as gas separation membranes has developed only recently. In this paper, various classes of proton-conducting materials have been reviewed with specific emphasis on their potential use as H2 separation membranes in the industrial processes of coal gasification, natural gas reforming, methanol reforming and the water–gas shift (WGS) reaction. Key material requirements for their use in these applications have been discussed. 相似文献
997.
The passive behavior of ZrNi alloys near the rest potential is studied through in situ voltammetry, ellipsometry, and microscopic observation. A significant oxide layer growth is observed in aqueous 1 M KOH during the application of different potential programs currently used in the activation processes of the alloy. Oxide barrier effects and occlusion of hydrogen species within the film take place. The kinetics of the oxide layer formation under potential cycling plays a significant role in the activation process of metal alloys used in metal hydride batteries.Dedicated to Professor Gyorgy Horanyi on the occasion of his 70th birthday. 相似文献
998.
Grzegorz Bejcar Piotr Przybylski Joanna Fusiara Bogumil Brzezinski Franz Bartl 《Journal of Molecular Structure》2005,754(1-3):31-36
A new hydrazone of gossypol with 3,6-dioxaheptylhydrazine (GHDO) has been synthesised and its structure has been studied by FT-IR, 1H NMR, 13C NMR as well as PM5 semiempirical methods. All the studies have provided clear evidence of the existence of GHDO in the solution in the N-imine–N-imine tautomeric form. The structure and the spectroscopic behaviour of this tautomer are discussed in details. It is shown the structure of GHDO is strongly stabilised by different types of intramolecular hydrogen bonds. In two of them the oxygen atoms of the oxaalkyl chains are also engaged. The strongest intramolecular hydrogen bond is formed between the O7H proton and N16 atom from the hydrazone group. 相似文献
999.
1000.
甘氨酸与水分子间相互作用的理论研究 总被引:1,自引:1,他引:0
在密度泛函(DFT)B3LYP/6_311++G(3d,3p)水平,对中性甘氨酸的最小点结构Ip和H2O分子间可能存在的氢键复合物进行全自由度能量梯度优化,发现了三个氢键极小结构A、C和E,其中结构A为最稳定结构,它是H2O与甘氨酸的羧基(-COOH)形成两个氢键的结构,具有C1对称性.分别采用密度泛函理论(DFT)和MP2方法,在6-311++G(3d,3p)水平,对结构A的结构和结合能进行了比较计算,得到结合能ΔEDFT为-41.88 kJ/mol,ΔEMP2为-40.34 kJ/mol. 相似文献