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951.
提出了一种新型的基于波长双环路结构的光电振荡器方案. 在此方案中, 利用两个激光器产生两束波长不同的连续光, 分别通过两段长度不同的光纤构成双环路结构, 利用光学游标效应可以获得单一的起振模式. 通过理论分析可知, 不同波长的两束光载波在耦合时, 几乎不会产生随机拍噪声. 实验中, 获得了X波段(8-12 GHz)内频率可调谐的高质量微波信号. 通过测量, 信号的边模抑制比达到60 dB, 相位噪声为-132.6 dBc/Hz@10 kHz. 同时, 利用锁相环技术, 通过光纤拉伸器有效补偿系统的腔长漂移, 因此振荡频率的稳定性得到极大改善. 系统的频率漂移在2 h内小于±84.3 mHz. 另外, 测得的微波线宽为5.3 mHz, Q值在1012量级, 具有很高的谱纯度. 相似文献
952.
Electron‐transfer transparency of graphene: Fast reduction of metal ions on graphene‐covered donor surfaces 下载免费PDF全文
Du Won Jeong Serin Park Won Jin Choi Giyeol Bae Yun Jang Chung Cheol‐Soo Yang Young Kuk Lee Ju‐Jin Kim Noejung Park Jeong‐O. Lee 《固体物理学:研究快报》2015,9(3):180-186
The mechanism of charge transfer through nanomaterials such as graphene remains unclear, and the amount of charge that can be transferred from/to graphene without damaging its structural integrity is unknown. In this communication, we show that metallic nanoparticles can be decorated onto graphene surfaces as a result of charge transfer from the supporting substrate to an adjoining solution containing metal ions. Au or Pt nanoparticles were formed with relatively high yield on graphene‐coated substrates that can reduce these metal ions, such as Ge, Si, GaAs, Al, and Cu. However, metal ions were not reduced on graphene surfaces coated onto non‐reducing substrates such as SiO2 or ZnO. These results confirm that graphene can be doped by exploiting charge transfer from the underlying substrate; thus graphene is not only transparent with respect to visible light, but also with respect to the charge transfer. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim) 相似文献
953.
用从头计算方法研究了在Bi2Te3体系采用过渡金属掺杂从而诱导出磁性的可能性.用一个过渡金属原子置换一个Bi原子之后,可以在该体系中产生磁矩,这主要是由于过渡金属原子的3d轨道电子的自旋极化导致的.当一个Ti、V、Cr、Mn和Fe原子分别替代一个Bi原子时,体系显示的磁矩分别为0.92、1.97、2.97、4.04和4.98 μB.当引入两个过渡金属原子代替两个Bi原子的时候,交换耦合的特性取决于取代Bi原子的分布;代替的Bi原子的位置在Bi1和Bi5的位置时,这两个过渡金属原子之间的距离为11.52 ?, Bi1.84TM0.16Te3体系能量最稳定并且表现出铁磁性耦合. 相似文献
954.
We designed a cyclic borane (B6H12) molecule with a benzene‐like structure, in which the six B atoms are located in the same plane. Three methods of B3LYP, MP2, and CCSD with the 6‐311++G** basis were used to investigate its structure, electronic property, and stability. Next, we calculated the stability and electronic property of three hydroboron derivatives with fused rings of B10H18, B14H24, and B16H26. Finally, we investigated three types of novel two‐dimensional infinite hydroboron sheets with diborane as a building block. The results of the phonon spectra ensure the dynamic stability of these predicted structures. Furthermore, the three types of hydroboron sheets are shown to have different band gap energies of less than 3.0 eV. Some investigations on the optical properties have also been performed. The predicted sheets are candidates for semiconductors, whose band gap energy can be tuned by the positions of the bridge hydrogen atoms in the sheets. 相似文献
955.
Yoon Shon Sejoon Lee Tae Won Kang Youngmin Lee Seung-Woong Lee Jin Dong Song Hyung-Jun Kim Jeong Ju Lee Im Taek Yoon 《Journal of Crystal Growth》2010,312(14):2069-2072
The p-type InMnP:Be epilayers, which were prepared by thermal diffusion of Mn through in-situ deposition of Mn layer using molecular beam epitaxy (MBE) onto MBE-grown InP:Be epilayers and subsequent in-situ annealing at 300–350 °C, were investigated. InMnP:Be epilayers prepared by the above sequence clearly showed the Mn-related emission band at 1.1–1.2 eV, which indicates the effective incorporation of Mn2+ ions into the host layer InP:Be. The samples demonstrated very large ferromagnetic hysteresis loops with enhanced coercivity, and the ferromagnetic-to-paramagnetic transition of the samples was observed to occur at ∼85 K. These results suggest that InP-based ferromagnetic semiconductor layers having enhanced ferromagnetism can be effectively formed by the above-mentioned sequential in-situ processes. 相似文献
956.
The effect of heat treatment of the germano-silicate glass optical fiber incorporated with PbTe quantum dots on the absorption characteristics was investigated. Incorporation of the PbTe QDs in the fiber core was confirmed by the absorption peaks that appeared at 687 nm and 1055 nm and their shift upon heat treatment. The absorption peak was found to shift linearly toward a longer wavelength after heat treatment at 700 °C, 1000 °C, and 1100 °C for 1 h. The red shift of the excitonic absorption peak was attributed to the increase in the average size of the PbTe QDs in the fiber core. 相似文献
957.
Alfredo Ruiz-Arias Cleotilde Juárez-Ramírez Daniel de los Cobos-Vasconcelos Nora Ruiz-Ordaz Angélica Salmerón-Alcocer Deifilia Ahuatzi-Chacón Juvencio Galíndez-Mayer 《Applied biochemistry and biotechnology》2010,162(6):1689-1707
A microbial community able to aerobically degrade the azo dye Acid Orange 7 was selected from riparian or lacustrine sediments collected at sites receiving textile wastewaters. Three bacterial strains, pertaining to the genera Pseudomonas, Arthrobacter, and Rhizobium, constitute the selected community. The biodegradation of AO7 was carried out in batch-suspended cell culture and in a continuously operated multistage packed-bed BAC reactor. The rapid decolorization observed in batch culture, joined to a delay of about 24 h in COD removal and cell growth, suggests that enzymes involved in biodegradation of the aromatic amines generated after AO7 azo-bond cleavage (1-amino-2-naphthol [1-A2N] and 4-aminobenzenesulfonic acid [4-ABS]), are inducible in this microbial consortium. After this presumptive induction period, the accumulated byproducts, measured through COD, were partially metabolized and transformed in cell mass. At all azo dye loading rates used, complete removal of AO7 and 1-A2N was obtained in the multistage packed-bed BAC reactor (PBR).; however, the overall COD (η COD ) and 4-ABS (η ABS ) removal efficiencies obtained in steady state continuous culture were about 90%. Considering the toxicity of 1-A2N, its complete removal has particular relevance. In the first stages of the packed-bed BAC reactor (Fig. 4a–c), major removal was observed. In the last stage, only a slight removal of COD and 4-ABS was obtained. Comparing to several reported studies, the continuously operated multistage packed-bed BAC reactor showed similar or superior results. In addition, the operation of large-packed-bed BAC reactors could be improved by using several shallow BAC bed stages, because the pressure drop caused by bed compaction of a support material constituted by small and fragile particles can be reduced. 相似文献
958.
Ju Ho Lee Moon Sam Shin Hwayong Kim Ki-Pung Yoo 《The Journal of chemical thermodynamics》2010,42(7):891-899
Lattice fluid can describe a vapor–liquid transition but not a solid–fluid transition. In this work, we propose a simple and analytic term which yields a solid–fluid transition when coupled with a lattice based equation of state (EOS). The proposed term is derived based on the two assumptions that (1) solid can be considered as highly associated phase affected by strong attractive force and (2) this force is distinct from the conventional attractive forces yielding a vapor–liquid transition. To formulate these assumptions, we extend Veytsman statistics by modifying its density dependency. The derived term was combined with a quasi-chemical nonrandom lattice fluid theory (QLF) developed by the authors. The combined model was found to require only two parameters besides 3 QLF parameters for physical properties calculation of three phases. When tested against equilibrium properties of 8 components, the combined model was found to closely reproduce melting pressure, sublimation pressure, and vapor pressure, but underestimate solid density as well as heat of melting at the triple point temperature. It was found that the present approach can yield a solid–liquid transition at all temperatures. 相似文献
959.
设计、合成了36个新型哌嗪并[2,1-a]异喹啉类化合物,并测试了其体外抗真菌活性.结果表明所有化合物对5种临床致病真菌都有抗真菌活性.其中化合物5h,5j~5l,6g~6k和6l对除白念菌外的4种测试菌的抗真菌活性强于或相当于对照药氟康唑;特别是大多数目标化合物对于氟康唑无效的薰烟曲霉菌显示出较好抗真菌活性.对接研究显示所设计的目标化合物与靶酶活性腔中氨基酸功能残基结合.结果表明新型哌嗪并[2,1-a]异喹啉类化合物是一类全新结构类型的抗真菌化合物,为抗真菌药物研究提供了新的结构类型. 相似文献
960.
Namgee Jung Yoon-Hwan Cho Kwang-Hyun Choi Ju Wan Lim Yong-Hun Cho Minjeh Ahn Yun Sik Kang Yung-Eun Sung 《Electrochemistry communications》2010,12(6):754-757
The cathode electrode structure of the direct methanol fuel cell (DMFC) was improved by a novel catalyst ink preparation method. Regulation of the solvent polarity in the cathode catalyst ink caused increases in the electrochemical active surface (EAS) for the oxygen reduction reaction (ORR) as well as decreases in the methanol crossover effect. In a two-step preparation, agglomerates consisting of catalyst and Nafion ionomers were decreased in size, and polar groups in the ionomers formed organized networks in the cathode catalyst layer. Despite Pt catalysts in the cathode being only 0.5 mg cm? 2, the maximum power density of the improved membrane electrode assembly (MEA) was 120 mW cm? 2, at 3 M methanol, which was much larger than that of traditional MEA (67 mW cm? 2). 相似文献