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991.
992.
993.
Ging Ho Hsiue Ying Ling Liu Hsin Hao Liao 《Journal of polymer science. Part A, Polymer chemistry》2001,39(7):986-996
Phosphorus‐containing epoxy‐based epoxy–silica hybrid materials with a nanostructure were obtained from bis(3‐glycidyloxy)phenylphosphine oxide, diaminodiphenylmethane, and tetraethoxysilane in the presence of the catalyst p‐toluenesulfonic acid via an in situ sol–gel process. The silica formed on a nanometer scale in the epoxy resin was characterized with Fourier transform infrared, NMR, and scanning electron microscopy. The glass‐transition temperatures of the hybrid epoxy resins increased with the silica content. The nanometer‐scale silica showed an enhancement effect of improving the flame‐retardant properties of the epoxy resins. The phosphorus–silica synergistic effect on the limited oxygen index (LOI) enhancement was also observed with a high LOI value of 44.5. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 986–996, 2001 相似文献
994.
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
995.
Vitamin B12(macrocyclic cobalamin) has been recently reported to be capable of electrochemically catalyzing water oxidation in a neutral phosphate buffer solution. In this work, density functional calculations were employed to elucidate the water oxidation mechanism catalyzed by vitamin B12. The calculations showed that the catalytic cycle starts from the L·-CoⅡ-OH2 complex 1. A proton-coupled electron transfer process then leads to the formation of a ... 相似文献
996.
997.
Fangfang Liao Shapour Heidarkhani Ghasem A. Afrouzi Amjad Salari 《Journal of Applied Analysis & Computation》2019,9(1):314-331
We investigate the existence of multiple solutions for parametric quasi-linear systems of the gradient-type on the Sierpi\''{n}ski gasket. We give some new criteria to guarantee that the systems have at least three weak solutions by using a variational method and some critical points theorems due to Ricceri. We extend and improve some recent results. Finally, we give two examples to illustrate the main results. 相似文献
998.
T. C. Chang C. L. Liao K. H. Wu G. P. Wang Y. S. Chiu 《Journal of polymer science. Part A, Polymer chemistry》1998,36(14):2521-2530
Poly(methylphenylsiloxane)–poly(methyl methacrylate) graft copolymers (PSXE-g-PMMA) were prepared by condensation reaction of poly(methylphenylsiloxane)-containing epoxy resin (PSXE) with carboxyl-terminated poly(methyl methacrylate) (PMMA), and they were characterized by gel permeation chromatography (GPC), infrared (IR), and 29Si and 13C nuclear magnetic resonance (NMR). The microstructure of the PSXE-g-PMMA graft copolymer was investigated by proton spin–spin relaxation T2 measurements. The thermal stability and apparent activation energy for thermal degradation of these copolymers were studied by thermogravimetry and compared with unmodified PMMA. The incorporation of poly(methylphenylsiloxane) segments in graft copolymers improved thermal stability of PMMA and enhanced the activation energy for thermal degradation of PMMA. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2521–2530, 1998 相似文献
999.
Bonding, structure, and stability of solid A2MH2 with A = Li, Na; M = Pd, Pt were investigated with a relativistically corrected density-functional approach, which reliably describes the trends among these four compounds. In order to examine the influence of the ligands (A) and of the crystalline environment, calculations were also made for free A2MH2 molecules and MH22– ions. The free MH22– complex is held together by strong bonds between formally closed shell atomic units because of strong M-d,s hybridization. The M–H bonds are further stabilized by the alkali metal ion ligands and by the crystal surrounding. The crystal field expands the H–A distance and enhances the H–A polarity. Relativistic effects contribute to M–H bonding in the solid state. The experimentally determined bond lengths and their trends are in accordance with theory. Due to relativistic and lanthanide effects, the Pt–H bond length becomes nearly as short as the Pd–H one. The small Li ion causes a distortion of the Li2PtH2 crystal resulting in an even shorter Pt–H bond length. In the gas-phase, A2PtH2 is more stable against dissociation than A2PdH2. The stability of the solid compounds is strongly influenced by the cohesive energy of the metal M, and also by the nature of the alkali metal. The evaluated enthalpies of formation favor increasing stability of solid A2MH2 against disproportionation into M and AH from Pt to Pd and from Li to Na. This is in agreement with experimental findings. The assignment of the experimental vibrational excitations should be reconsidered. 相似文献
1000.
基于自洽电荷密度泛函紧束缚(SCC-DFTB)方法研究了富氮含能材料5, 5’-双四唑肼(C2H4N10, HBT)晶体在高温下的热分解反应过程.结果表明,结构优化参数与实验误差在5%以内.在2000 K, 2500 K,和3000 K不同温度下,HBT晶体热分解路径和产物表现出相似性.通过过渡态理论和分子动力学两种方法,研究了分解反应C2H4N10→C2H3N7+HN3,发现HBT晶体分解产物中存在叠氮酸(HN3)分子,化学反应势垒高度为222.85 kJ·mol-1.研究结果为进一步理解高温下HBT晶体热分解特征提供理论参考. 相似文献