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We report a simple Nd:YAG laser that emits radially polarized beam with helical wavefront. The laser cavity consists of a piece of laser crystal and a plane output coupler, and there is no additional polarization component inside it. The pump light is converted into annular profile through de-focal coupling into a multi-mode fiber. For the continuous-wave(CW) operation, the laser emits radially polarized vortex beam, and it is observed that the helical wavefront of the laser beam is switched from right handedness to left handedness when the output coupler is tilted slightly. For the Q-switched operation under the insertion of a Cr4t:YAG saturable absorber inside the cavity, we obtain radially polarized outputs with left-handedness helical wavefront. By tilting the laser crystal slightly, the laser output switches to azimuthal polarization at pump power larger than 4.5 W and left-handedness helical wavefront of laser beam is preserved. 相似文献
216.
A novel hydroxo-lanthanide cluster organic framework, Sm3L8(μ 3-OH)(H2O)·H2O (1), derived from the 4-pyridin-4-ylbenzoic acid (HL) has been hydrothermally made and structurally characterized by single crystal X-ray diffraction. Structure analysis shows the hexanuclear Sm6 cluster unit is composed of inorganic tetranuclear hydroxo [Sm4(OH)2]10+ (Sm4) cluster and dimeric [Sm2(COO)4]2+ (Sm2) core. The Sm6 cluster units are connected by L ligands to form a 2D Ln-based cluster organic framework. From the topological point of view, the layer architecture can be described as 4-connected sql net. Furthermore, the elemental analysis, PXRD, IR and TGA are also studied. 相似文献
217.
Qian Zhang Qingfeng Li Linxian Zhang Yitian Fang Zhiqing Wang 《Journal of Thermal Analysis and Calorimetry》2014,115(2):1929-1938
The pyrolysis, combustion, and gasification behaviors of deoiled asphalt were studied by a thermogravimetric analyzer and the kinetics were also analyzed using a multi-stage first-order integral model. All the experiments were conducted at non-isothermal conditions with heating rates range of 10–40 K min?1 under N2 (pyrolysis), air (combustion), or CO2 (gasification) atmosphere, respectively. The results showed that, for pyrolysis, the reaction mainly occurred between 498 and 798 K and could be divided into two stages: the first was caused by the volatilization of small molecules and the second probably due to the cracking reactions. For combustion, the mass loss process could be divided into three stages: the devolatilization and oxidation first, the ignition and combustion of the volatiles second, and finally the combustion of the formed char. Under CO2 atmosphere, the mass loss behavior was similar with that of the N2 atmosphere at lower temperatures, but when the temperature was higher than 1,233 K, the gasification reaction obviously happened. The results of kinetic investigation showed that the multi-stage first-order integral method agreed well with the above experiments. 相似文献
218.
Qiang Chen Zheng Fang Shaofen Wang 《Journal of Thermal Analysis and Calorimetry》2014,115(2):1799-1804
A specially designed thermo-electrochemical calorimeter was applied to measure the electrochemical Peltier heats (EPH) of Fe(CN) 6 3?/4? system at 295.15 K. The curves of the electrode potential changes and temperature changes against time for Fe(CN) 6 3?/4? couple with five groups of different concentrations were obtained under the condition of various constant-current polarizations. The EPH values for the considered electrode reaction are determined to be ?41.31, ?42.73, ?44.28, ?45.87, and ?46.65 kJ mol?1 at the respective concentrations of 0.125, 0.175, 0.225, 0.275, and 0.300 mol dm?3; and the EPH and the apparent enthalpy change corresponding to the infinite dilution to be ?37.42 and ?84.10 kJ mol?1 at 295.15 K, respectively. 相似文献
219.
Inside Back Cover: Controlled Electropolymerization of Ruthenium(II) Vinylbipyridyl Complexes in Mesoporous Nanoparticle Films of TiO (Angew. Chem. Int. Ed. 19/2014) 下载免费PDF全文
220.
Concerted Asynchronous Hula‐Twist Photoisomerization in the S65T/H148D Mutant of Green Fluorescent Protein 下载免费PDF全文
Dr. Qiangqiang Zhang Prof. Xuebo Chen Dr. Ganglong Cui Prof. Wei‐Hai Fang Prof. Dr. Walter Thiel 《Angewandte Chemie (International ed. in English)》2014,53(33):8649-8653
Fluorescence emission of wild‐type green fluorescent protein (GFP) is lost in the S65T mutant, but partly recovered in the S65T/H148D double mutant. These experimental findings are rationalized by a combined quantum mechanics/molecular mechanics (QM/MM) study at the QM(CASPT2//CASSCF)/AMBER level. A barrierless excited‐state proton transfer, which is exclusively driven by the Asp148 residue introduced in the double mutant, is responsible for the ultrafast formation of the anionic fluorescent state, which can be deactivated through a concerted asynchronous hula‐twist photoisomerization. This causes the lower fluorescence quantum yield in S65T/H148D compared to wild‐type GFP. Hydrogen out‐of‐plane motion plays an important role in the deactivation of the S65T/H148D fluorescent state. 相似文献