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971.
The amount of ER effect is determined by the difference of dielectric constants of ER particles base liquid.The intensity of ER fluids can be characterized by the interaction of two particles. A double optical tweezers system suitable to study particle interaction is used to measure the particle aggregation time, and it is found that the particle aggregation time is proportional to the square of the electric field. This is the first time to directly measure the interaction of the electric dipoles of ER particles. A method is developed to use high speed CCD in measuring diffusing-wave spectroscopy (DWS), and, for the first time, the auto-correlation functions of nonegordic system of particle structure are measured to study the ER mechanism. Structure response time and force response time are obtained for glass beads ER fluid, and the time variation of characteristic decay times of system correlation functions under different electric fields is also measured. Diffusing coefficients under different fields imply that the interaction is proportional to the square of fields. 相似文献
972.
Chorng‐Shyan Chern Long‐Jiang Wu 《Journal of polymer science. Part A, Polymer chemistry》2001,39(19):3199-3210
Styrene microemulsion polymerizations with different short‐chain alcohols [n‐CiH2i+1OH (CiOH), where i = 4, 5, or 6] as the cosurfactant were investigated. Sodium dodecyl sulfate and sodium persulfate (SPS) were used as the surfactant and initiator, respectively. The desorption of free radicals out of latex particles played an important role in the polymerization kinetics. An Arrhenius expression for the radical desorption rate coefficient was obtained from the polymerizations at temperatures of 50–70 °C. The polymerization kinetics were not very sensitive to the alkyl chain length of alcohols compared with the temperature effect. The maximal polymerization rate in decreasing order was C6OH > C4OH > C5OH. This was related to the differences in the water solubility of CiOH and the structure of the oil–water interface. The feasibility of using a water‐insoluble dye to study the particle nucleation mechanisms was also evaluated. The parameters chosen for the study of the particle nucleation mechanisms include the cosurfactant type (CiOH), the SPS concentration, and the initiator type (oil‐soluble 2,2′‐azobisisobutyronitrile versus water‐soluble SPS). © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3199–3210, 2001 相似文献
973.
En‐Qing Gao Dai‐Zheng Liao Zong‐Hui Jiang Shi‐Ping Yan 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(7):807-809
A hydrogen‐bonded coordination supramolecule, (meso‐5,7,7,12,14,14‐hexamethyl‐1,4,8,11‐tetraazacyclotetradecane‐κ4N)nickel(II) [N,N‐o‐phenylenebis(oxamato)‐κ4O,N,N′,O′]nickelate(II) dihydrate, [Ni(C16H36N4)][Ni(C10H4N2O6)]·2H2O or [Ni(meso‐cth)][Ni(opba)]·2H2O, has been prepared and characterized by X‐ray crystallographic analysis. The two complex ions, i.e. [Ni(meso‐cth)]2+ and [Ni(opba)]2?, are hydrogen bonded to each other, resulting in two‐dimensional neutral supramolecular sheets. The sheets stack along the a direction to produce a three‐dimensional architecture with one‐dimensional channels in which hydrogen‐bonded chains of water molecules are included. 相似文献
974.
Jiang Xia Wei-Yin Sun Yan Xu Kai-Bei Yu Wen-Xia Tang 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(1):38-39
The title molecule, [Ni(C6H17N3O)2](ClO4)2, possesses a crystallographic centre of symmetry at the NiII position. The coordination geometry around the NiII atom is distorted octahedral, consisting of six N atoms from two tripodal polyamine ligands, while the ethanol O atoms of the ligands remain uncoordinated. The crystal packing shows two-dimensional layers and an infinite three-dimensional framework which is stabilized by a hydrogen-bonded network. 相似文献
975.
Lei Zhang Zhi‐Liang Liu Lin‐Hong Weng Dai‐Zheng Liao Zong‐Hui Jiang Shi‐Ping Yan Pan‐Wen Shen Martin Baumgarten 《Helvetica chimica acta》2001,84(4):834-841
The structure of a novel oxido‐aminoxyl (=`nitronyl nitroxide') biradical, 2,2′‐(1‐oxidopyridine‐2,6‐diyl)bis[4,5‐dihydro‐4,4,5,5‐tetramethyl‐3‐oxido‐1H‐imidazol‐1‐oxyl] hydrate ( 1 ⋅H2O) was established by X‐ray analysis in the solid state: monoclinic, space group P21/c, Z=4 with a=12.621(4), b=15.704(5), and c=13.001(4) Å, and β=115.202(6)°. Variable‐temperature magnetic susceptibilities show a weak antiferromagnetic interaction between the two oxido‐substituted aminoxyl moieties of 1 , indicative of a singlet ground state. AM1 Calculations located minima for the possible structure based on the X‐ray crystal structure. A hybride density‐functional‐theory calculation with the UB3LYP method from the X‐ray crystal structure establishes the same spin sign in the two aminoxyl moieties and shows that a small spin density is localized at the C‐atoms of the pyridine moiety. These theoretic results are in good agreement with the determined weak antiferromagnetic interaction of 1 . 相似文献
976.
A new class of biodegradable polyampholytes, poly[(aspartic acid)‐co‐lysine], were synthesized by thermal polycondensation of aspartic acid and lysine under reduced pressure and subsequent hydrolysis. Polymerization conditions were optimized to yield maximal water‐soluble poly(succinimide‐co‐lysine) with high molecular weight (160°C/3.5 h). The succinimide/lysine ratio in the polyampholytes could be adjusted by their feed ratio. Characterization of the poly(succinimide‐co‐lysine) by 1H NMR revealed that ω‐amine and carboxylic groups in lysine participated in the polymerization, leaving α‐amino groups as pendant cationic moieties. 相似文献
977.
Molecular dynamics (MD) simulations of a polyethersulfone (PES) chain are carried out in the amorphous state by using the Dreiding 2.21 force field at four temperatures. Two types of molecular motion, i.e. rotations of phenylene rings and torsions of large segments containing two oxygen atoms, two sulfur atoms, and five phenylene rings on the backbone, are simulated. The modeling results show that the successive phenylene rings should be in‐phase cooperative rotations, whereas the successive large segments should be out‐of‐phase cooperative torsions. By calculating the diffusion coefficient for the phenylene ring rotations, it is found that this rotation contributes to the β‐transition of PES. 相似文献
978.
利用自制的烟雾箱系统研究了臭氧与二乙胺和三乙胺的气相反应动力学. 实验过程中保证二乙胺和三乙胺浓度远远大于臭氧浓度, 使得实验在准一级条件下进行. 加入环己烷以消除实验过程中可能产生的OH自由基对反应的影响. 在(298±1) K和1.01×105 Pa条件下, 测得臭氧与二乙胺和三乙胺反应的绝对速率常数值分别为(1.33±0.15)×10-17和(8.20±1.01)×10-17 cm3·molecule-1·s-1. 与文献中已有的其它胺类的臭氧反应数据比较后发现, 臭氧与胺的反应可以用亲电反应机制来解释. 另外, 通过对比发现, 臭氧与三取代的烷基胺类的反应速率要远远大于其与二取代的烷基胺类的反应速率. 这在一定程度上可有助于解释外场观测到的气溶胶相中二烷基胺盐较多的事实. 利用测得的速率常数和大气中臭氧浓度, 还估算了二乙胺和三乙胺与臭氧反应的大气寿命. 结果显示, 与臭氧的反应是二乙胺和三乙胺在大气中的一种重要的消除途径, 尤其是在污染严重地区. 相似文献
979.
980.