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101.
Jingqi Guan Ying Yang Bo Liu Yuanyuan Ma Xiaofang Yu Jing Liu Qiubin Kan 《Reaction Kinetics and Catalysis Letters》2008,95(2):313-320
MoV0.3Te0.17 and MoV0.3Te0.17Nb0.12 catalysts were prepared by a hydrothermal synthesis route and tested for the oxidation of isobutane and isobutene. Characterization
results showed that the structure and property of Mo-V-Te-based catalysts are relatively different depending on the presence
of the Nb element. Catalytic tests showed that the selectivity of methacrolein can comparatively be improved by the addition
of Nb into the MoV0.3Te0.17 catalyst for the selective oxidation of isobutane. 相似文献
102.
103.
The 19F N.M.R. spectrum of 1,2,2,2-tetrachloro-l,l-difluoroethane has been studied in the nematic liquid crystal ZLI1167 (Merck) upon rotation at the magic angle. The director of the liquid crystal is oriented perpendicular to the spinning axis when the angle between the rotation axis and the magnetic field is less than the magic angle and parallel when this angle is more than the magic angle. It is shown that exactly at the magic angle the spectrum corresponds to a frequency modulated powder pattern. This powder pattern leads to an understanding of the orientational behaviour of the director when a nematic is spun at the magic angle. 相似文献
104.
105.
Fang‐Chyou Chiu Chin‐Yu Kan Jen‐Chang Yang 《Journal of Polymer Science.Polymer Physics》2009,47(15):1497-1510
The thermal properties and phase morphology of poly(L ‐lactide) (PLLA)‐based blends have been studied. Two poly(ethylene glycol)s (PEGs) with molecular weight (MW) of about 1,500 (1.5k) g/mol and 2,000,000 (2M) g/mol, respectively, were used as counterparts. The blends were annealed at a preselected temperature of 200 °C for either 2 min or 30 min before the characterizations. Both PEGs were determined to enhance the crystallizability of PLLA. After a 2‐min process of annealing, the PEG(1.5k)'s crystallization efficiency on PLLA has been noted to increase with the increase of its content. Conversely, PEG(2M)'s crystallization efficiency declined with the increase of its content. Extending the annealing time has evidently changed the PEGs' crystallization effect on PLLA. Moreover, the PEG(1.5k) has, to a greater extent, brought about the depression of PLLA's melting temperature by increasing its content, and this depression increased with the annealing time. The blends exhibited lower thermal stability than those of the parent components, particularly for the PEG(1.5k)‐included system with a higher PEG content. Regardless of the annealing time, the PEG(1.5k)‐included blends have shown homogeneous melt morphology under light microscope, whereas the PEG(2M)‐included blends have displayed phase‐separated melt morphology. In addition to the composition, PEG's MW and annealing time influence the crystalline morphology of the blends. The ringed PLLA spherulites have appeared mostly in the 2‐min annealed PEG(1.5k)‐included blends. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1497–1510, 2009 相似文献
106.
Richard H. Byrd Cornelius L. Dert Alexander H. G. Rinnooy Kan Robert B. Schnabel 《Mathematical Programming》1990,46(1-3):1-29
The global optimization problem, finding the lowest minimizer of a nonlinear function of several variables that has multiple local minimizers, appears well suited to concurrent computation. This paper presents a new parallel algorithm for the global optimization problem. The algorithm is a stochastic method related to the multi-level single-linkage methods of Rinnooy Kan and Timmer for sequential computers. Concurrency is achieved by partitioning the work of each of the three main parts of the algorithm, sampling, local minimization start point selection, and multiple local minimizations, among the processors. This parallelism is of a coarse grain type and is especially well suited to a local memory multiprocessing environment. The paper presents test results of a distributed implementation of this algorithm on a local area network of computer workstations. It also summarizes the theoretical properties of the algorithm.Research supported by AFOSR grant AFOSR-85-0251, ARO contract DAAG 29-84-K-0140, NSF grant DCR-8403483, and NSF cooperative agreement DCR-8420944. 相似文献
107.
在长距离高精度光纤时间同步系统中,为了减少后向反射光与光纤色散对传输精度的影响,本文在双波长光纤时间同步传输方法之上,提出了一种具有色散误差修正功能的双波长光纤时间同步传输方法.以自行研制的工程样机在长度约为800 km的实验室光纤链路上和1085 km的实地光纤链路上进行了实验测试,也是国内首次实现千公里级实地光纤时间同步传输.在实验室光纤链路上,测得传输链路色散补偿后的色散时延误差为10 ps,时间同步标准差为5.7 ps,稳定度为1.12 ps@105 s,不确定度为18.4 ps.在实地光纤链路上,测得传输链路色散补偿后的色散时延误差为60 ps,时间同步标准差为18 ps,稳定度为5.4 ps@4×104 s,不确定度为63.5 ps. 相似文献
108.
Eri Sano Weihua Li Hitomi Yuki Xinli Liu Tomomi Furihata Kaoru Kobayashi Kan Chiba Saburo Neya Tyuji Hoshino 《Journal of computational chemistry》2010,31(15):2746-2758
Cytochrome P450 (CYP) is deeply involved in the metabolism of chemicals including pharmaceuticals. Therefore, polymorphisms of this enzyme have been widely studied to avoid unfavorable side effects of drugs in chemotherapy. In this work, we performed computational analysis of the mechanism of the decrease in enzymatic activity for three typical polymorphisms in CYP 2C9 species: *2, *3, and *5. Based on the equilibrated structure obtained by molecular dynamics simulation, the volume of the binding pocket and the fluctuation of amino residues responsible for substrate holding were compared between the wild type and the three variants. Further docking simulation was carried out to evaluate the appropriateness of the binding pocket to accommodate substrate chemicals. Every polymorphic variant was suggested to be inferior to the wild type in enzymatic ability from the structural viewpoint. F‐G helices were obviously displaced outward in CYP2C9*2. Expansion of the binding pocket, especially the space near F′ helix, was remarkable in CYP2C9*3. Disappearance of the hydrogen bond between K helix and β4 loop was observed in CYP2C9*5. The reduction of catalytic activity of those variants can be explained from the deformation of the binding pocket and the consequent change in binding mode of substrate chemicals. The computational approach is effective for predicting the enzymatic activity of polymorphic variants of CYP. This prediction will be helpful for advanced drug design because calculations forecast unexpected change in drug efficacy for individuals. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2010 相似文献
109.
The composites comprising Fe-carbon nanotubes (CNTs) on TiO2 were prepared by a modified sol-gel method and characterized by nitrogen adsorption, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and energy dispersive X-ray analysis. The photocatalytic decomposition of rhodamine B (Rh.B) under UV irradiation and air aeration catalyzed by the composites was measured. The photocatalytic activity of TiO2 nanoparticles was significantly enhanced by the large CNT network that facilitated electron transfer between adsorbed Rh.B molecules and the catalyst substrate and the simultaneous occurrence of the photo-Fenton reaction in the presence of Fe particles. A marked acceleration of the decomposition rate was observed with aeration by flowing air aeration due to the formation of the circulatory photo-Fenton system. Chemical oxygen demand of piggery waste was measured at regular intervals to evaluate the mineralization of wastewater. 相似文献
110.
A non-closed hydrothermal synthetic processing is improved to synthesize Sm3+ doped β-NaYbF4 nano-phosphors at 98 °C without any high-temperature and high-pressure treatments as a final step. Novel green, red, and near-infrared broadband (799-873 nm) upconversion emissions of Sm3+-doped β-NaYbF4 nano-phosphors under 980 nm excitation are observed. These UC emissions can be assigned to the Sm3+ transitions of 4GJ, 4F3/2 and 6F11/2→6HJ. The half-width of 873 nm emission band is broadened nearly two-fold through the annealing treatment for nano-phosphors. The upconversion process in Yb3+-Sm3+ system is discussed based on energy transfer mechanisms. 相似文献