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881.
882.
应用多种荧光光谱追踪了高铁酸钾对荧蒽的降解过程, 包括发射, 同步, 三维(EEM), 时间扫描及光度定量所提供丰富的关于整个降解反应的信息, 探讨了高铁酸钾对荧蒽分子的降解特性及其随时间变化规律; 分别对该降解过程中的不同时段(20, 40, 70 s)的时间扫描荧光曲线进行拟合,并由此推测了高铁酸钾降解荧蒽的动力学特征。结果显示, 相同的反应时段, 各荧光光谱反映的高铁酸钾对荧蒽分子的降解率非常接近: t=10 s约55%; t=25 s约81%; t=40 s约91%。各时段的降解过程中均未出现新的荧光特性; t≤20 s, 为该降解反应的决定性阶段, 此阶段的降解过程最为接近线性关系; t>20 s, 降解过程偏离线性关系越来越远。整个降解过程可以近似地用一级反应动力学规律描述。 相似文献
883.
Xiao‐Ding Xu Chang‐Sheng Chen Bo Lu Zong‐Chun Wang Si‐Xue Cheng Xian‐Zheng Zhang Ren‐Xi Zhuo 《Macromolecular rapid communications》2009,30(3):157-164
Two kinds of representative polymers, poly(N‐isopropylacrylamide) (PNIPAAm) and β‐cyclodextrin (β‐CD) were selected and modified with azide and alkyne fucntional groups, respectively. When the solutions of these two modified polymers were mixed together, a cross‐linking reaction, a type of Huisgen's 1,3‐dipolar azide‐alkyne cycloaddition, occurred in the presence of Cu(I) catalyst. The strategy described here provides several advantages for the hydrogel formation including mild reaction conditions and controllable gelation rate. The resulted hydrogels were studied in terms of scanning electric microscopy (SEM), equilibrium swelling ratio and swelling/shrinking kinetics. The data obtained demonstrated the hydrogels had a porous structure as well as favorable thermosensitivity.
884.
Pr(Fe0.4Co0.6)1.93 ribbons were prepared by a melt-spinning method. Their structure and magnetic properties are investigated as functions of wheel speed and annealing temperature. The as-spun ribbon consists of a Pr(Fe, Co)2 cubic Laves phase and an amorphous phase at a wheel speed of v≥35 m/s, while the non-cubic phases of PuNi3-type and rare earth appear when the speed lower than 30 m/s. A single Pr(Fe, Co)2 phase with MgCu2-type structure has been synthesized by the process for the wheel speed of v≥35 m/s and subsequent annealing at 500 °C for 30 min. The epoxy/Pr(Fe0.4Co0.6)1.93 composite has been produced by a cold isostatic pressing technique, and the magnetic properties have been investigated. The composite rod sample possesses good magnetostrictive properties, i.e., a large magnetostriction (λa=λ∥−λ⊥) of 710 ppm at 800 kA/m and a dynamic coefficient d33 of 0.67 nm/A at 100 kA/m, and is of practical value. 相似文献
885.
Ag colloids were prepared by the microwave heating method. The UV‐visible spectrum and the transmission electron microscopy (TEM) were employed to characterize the Ag colloids. The surface‐enhanced Raman scattering (SERS) spectra of chloramphenicol (CAP) in Ag colloids were successfully recorded. The Raman spectra of CAP were recorded with good concordance comparing to the theoretical results calculated by the Gaussian'98 program. CAP molecules on the Ag surface are oriented tilted to the particle surface via C20‐O23, N‐O13, and N‐O23, which played an important role in the SERS effect. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
886.
X.K. Hu M.H. Xu P.Z. Si Q. Wu S.Y. Zhang 《Physica C: Superconductivity and its Applications》2009,469(2-3):102-105
We have prepared a series of bulk polycrystalline samples with the nominal compositions (YBa2Cu3O7)1?x(Nd0.7Sr0.3MnO3)x (x = 0–1) by a conventional solid-state reaction method using the larger difference in sintering temperature of the two constituent oxides and a well conceived sintering sequence. XRD patterns show that the samples are composites consisting of YBa2Cu3O7 and Nd0.7Sr0.3MnO3 particles with average grain size of ~65 nm. For x ? 0.55, with increasing x, the zero-resistance superconducting transition temperature, TC0, measured at zero magnetic field decreases and the normal state resistivity increases rapidly. The TC0 for the sample with x ~ 0.48 is estimated to be 0 K. The M–H hysteresis loops indicate the coexistence of ferromagnetism and superconductivity in the samples. The depression of TC0 can be attributed to the proximity effect between ferromagnetism and superconductivity. 相似文献
887.
Antiferromagnetic heavy fermion metals close to their quantum critical points display a richness in their physical properties unanticipated by the traditional approach to quantum criticality, which describes the critical properties solely in terms of fluctuations of the order parameter. This has led to the question as to how the Kondo effect gets destroyed as the system undergoes a phase change. In one approach to the problem, Kondo lattice systems are studied through a self-consistent Bose-Fermi Kondo model within the extended dynamical mean field theory. The quantum phase transition of the Kondo lattice is thus mapped onto that of a sub-Ohmic Bose-Fermi Kondo model. In the present article we address some aspects of the failure of the standard order-parameter functional for the Kondo-destroying quantum critical point of the Bose-Fermi Kondo model. 相似文献
888.
结合红外显微镜和步进扫描FTIR光谱仪 ,发展了固 /液界面电化学原位显微镜红外反射光谱和步进扫描快速时间分辨FTIR反射光谱 ,并应用于纳米材料特殊性能和电化学反应动力学的研究。研制纳米结构Pt微电极 ,获得CO吸附的红外特征随纳米结构和纳米尺度变化的原位显微镜红外谱图。利用纳米结构Pt微电极的异常红外效应 ,显著提高电化学原位红外反射光谱的灵敏度 ,获得分辨率达 5 0 μs的步进扫描时间分辨光谱。不仅发展了固 /液界面显微镜原位红外反射光谱新方法 ,并且拓展了电化学原位红外反射光谱在纳米材料科学研究中的应用。 相似文献
889.
Nicole Jara Nataly S. Miln Ashiqur Rahman Lynda Mouheb Daria C. Boffito Clayton Jeffryes Si Amar Dahoumane 《Molecules (Basel, Switzerland)》2021,26(15)
Nanomaterials have supported important technological advances due to their unique properties and their applicability in various fields, such as biomedicine, catalysis, environment, energy, and electronics. This has triggered a tremendous increase in their demand. In turn, materials scientists have sought facile methods to produce nanomaterials of desired features, i.e., morphology, composition, colloidal stability, and surface chemistry, as these determine the targeted application. The advent of photoprocesses has enabled the easy, fast, scalable, and cost- and energy-effective production of metallic nanoparticles of controlled properties without the use of harmful reagents or sophisticated equipment. Herein, we overview the synthesis of gold and silver nanoparticles via photochemical routes. We extensively discuss the effect of varying the experimental parameters, such as the pH, exposure time, and source of irradiation, the use or not of reductants and surfactants, reagents’ nature and concentration, on the outcomes of these noble nanoparticles, namely, their size, shape, and colloidal stability. The hypothetical mechanisms that govern these green processes are discussed whenever available. Finally, we mention their applications and insights for future developments. 相似文献
890.
Sen Li HongZhe Wang WeiWei Xu HongLei Si XiaoJun Tao Shiyun Lou Zuliang Du Lin Song Li 《Journal of colloid and interface science》2009,330(2):483-487
High-quality monodisperse Cu2S nanocrystals (sizes from 2 nm to 20 nm) have been successfully synthesized by the reaction of copper stearate (CuSt2) and dodecanethiol (DDT) in 1-octadecene (ODE). The nanocrystals were characterized using X-ray diffraction (XRD), X-ray photoelectron spectrum (XPS), and transmission electron microscopy (TEM). These as-prepared Cu2S nanocrystals with certain sizes have been found with good self-assembly behaviors, and they were easily to assemble into two-dimensional and three-dimensional superlattice structures. DDT served as both sulfur source and capping ligand, and was found a key factor to affect the growth and the self-assembly behaviors of the Cu2S nanocrystals. 相似文献