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121.
Qingfeng Zhang Yilong Lu 《International Journal of Infrared and Millimeter Waves》2008,29(11):1019-1027
This paper presents a method of designing substrate integrated waveguide-fed (SIW-fed) slot array antennas. The design theory
is based on the circuit model of slot and via as well as the reflection canceling. To prove the feasibility of this method,
a 10-element K-band SIW-fed 45-degree linearly polarized slot array antenna with uniform power distribution is designed. By
full-wave simulation, the antenna has a good impedance bandwidth of 7.5% and uniform power distribution. Besides, a maximum
gain of 15.3dBi is obtained in the broadside and the cross polarization is suppressed below -23.5dB in the boresight. This
type of SIW-fed slot array antennas can be a good candidate for microwave and millimeter-wave applications, especially for
auto-motive collision-avoidance radar systems. 相似文献
122.
The physics of the weak decay of hypernuclei is briefly reviewed from a theoretical point of view. Special regard is devoted to the recent progress concerning the determination of the non-mesonic decay widths and the asymmetry parameters. Convincing evidence has been achieved for a solution of the long-standing puzzle on the ratio Γn/Γp. Very recently, it has been shown that the exchange of a ππ pair in the weak mechanism plays a crucial role in explaining the discrepancies between theory and experiment on the decay asymmetries. 相似文献
123.
由各种形状冰晶粒子组成的卷云,对全球辐射平衡和气候变化有重要的影响,其影响程度取决于卷云本身的微物理特性和光学特性,如冰晶粒子形状、卷云光学厚度和云顶压强等.在对0.865μm波长处卷云光学特性研究的基础上,采用矢量辐射传输方程模拟分析了含卷云层的总反射率和偏振反射率,并利用卫星观测数据验证了模拟结果.分析研究了卷云微物理特征、光学特征和地表反照率对总反射率和偏振反射率的影响.分析表明,可以综合利用多角度偏振遥感信息反演各种卷云参数.这为利用多角度偏振遥感数据反演卷云各参数提供了理论基础.
关键词:
卷云微物理特征
卷云光学特性
多角度偏振辐射
矢量辐射传输方程 相似文献
124.
采用金属有机物化学气相淀积方法在铝酸锂LiAlO2衬底上外延生长m面GaN薄膜.X射线衍射测量的结果表明所得薄膜具有较理想的m面晶体取向,并对其各向异性的应变进行了计算,摇摆曲线的测量发现样品存在明显的面内结构各向异性.采用偏振光致发光研究材料的面内光学各向异性,发现随着偏振角度的改变,发光峰的峰位和强度均有明显变化,并用对称性破缺导致价带子带劈裂的理论对结果进行了解释.
关键词:
m面GaN
结构各向异性
偏振光致发光 相似文献
125.
126.
Leonardo Puppulin Yasuhito Takahashi Wenliang Zhu Giuseppe Pezzotti 《Journal of Raman spectroscopy : JRS》2011,42(3):482-487
The complex orientation dependence in space of Raman active vibrations in the orthorhombic structure of polyethylene (PE) is discussed in terms of Raman tensor elements as intrinsic physical parameters of the lattice. Building upon the symmetry assignment of these vibrational modes, we systematically studied, from both theoretical and experimental viewpoints, the changes of polarized intensity for the Ag and the B2g + B3g vibrational modes with respect to PE molecular orientation. After explicitly expanding the Raman selection rules associated with the Ag and the B2g + B3g modes, introducing them into general expressions of the orientation distribution function, and validating them by means of a least‐square fitting procedure on experimental data, we compare here two mesostructural models for a highly crystallized and self‐aligned PE fiber structure. Stereological arguments are shown concerning the arrangement of orthorhombic fibrils in such a sample that unfold the correct values of five independent Raman tensor elements for orthorhombic PE. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
127.
Dr. Masashi Hasegawa Chika Hasegawa Yuki Nagaya Prof. Dr. Kazunori Tsubaki Prof. Dr. Yasuhiro Mazaki 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(59):e202202218
Chiral macrocyclic dimers, trimers, and tetramers composed of paraphenylene and tethered binaphthyl were synthesized, and their molecular structures and chiroptical properties were investigated. X-ray analysis and theoretical calculations revealed that multiple twisted molecular structures – dimers, trimers, and tetramers – adopt figure-of-eight, Möbius triangle, and concave rectangle structures, respectively. These homologues have large ϵ values in their UV-vis absorption spectra because of the π-conjugation of the naphthalene-phenylene-naphthalene frameworks. Owing to the shape-persistent ring structure and tethering with −OCH2CH2O−, high fluorescence quantum yields and a relatively high dissymmetry factor gCPL in circularly polarized luminescence (CPL) spectra were achieved. This results in CPL brightness (BCPL) of over 100, which is greater than that of the conventional organic CPL dye. 相似文献
128.
Yusuke Tanaka Tomotaka Murayama Dr. Atsuya Muranaka Dr. Eiyu Imai Prof. Dr. Masanobu Uchiyama 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(8):1768-1771
We designed and synthesized a new type of small helical molecule exhibiting intense circularly polarized luminescence (CPL) ( 12H ) by modifying a 20π-electron hemiporphyrazine with a large transition magnetic dipole moment. The hemiporphyrazine ring was opened and one additional pyridine unit was introduced, resulting in an overlap of two pyridine rings. X-ray structure analysis confirmed that 12H and its zinc complex ( 1Zn ) adopt a helical geometry. A racemic mixture of 1Zn was resolved into two enantiomers ((P)- and (M)- 1Zn ), which exhibited CPL with a high luminescence dissymmetry factor (glum) value of ±2.1×10−2. The origin of the large glum value was rationalized by means of DFT calculations. Helical structures could be formed in a diastereoselective manner by covalently attaching chiral units to the skeleton ( 1’2H and 1’Zn ). 1Zn was found to possess chiral recognition ability for amines. 相似文献
129.
Absolute one-handed chiral quinoline tetramers andoctamers containing different oxazolylanilines at the C-terminus have been synthesized.The absolute one-handed sense and diastereomeric excess values were valued by^1H NMR.X-ray crystal diffractionand CD studies reveal that the S-oxazolylaniline always induces a P-handed helicity and the absolute helicity is driven by the stable three-center hydrogen bonding between protons in the amide and N atoms in oxazolylaniline and adjacent quinoline ring.CPL investigations demonstrated that S-CQn-a-d are CPL active and its g(lum)values are dependent on its length.Interestingly,the sizes of the substituents in the chiral centers are different,howeve r,they exert no effect on the dissymmetric factors g(abs)and g(lum)of quinoline oligoamide foldamers. 相似文献
130.
Lei Xu Chao Wang Yan-Xiang Li Xun-Hui Xu Dr. Li Zhou Dr. Na Liu Prof. Dr. Zong-Quan Wu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(38):16818-16825
Controlling the self-assembly morphology of π-conjugated block copolymer is of great interesting. Herein, amphiphilic poly(3-hexylthiophene)-block-poly(phenyl isocyanide)s (P3HT-b-PPI) copolymers composed of π-conjugated P3HT and optically active helical PPI segments were readily prepared. Taking advantage of the crystallizable nature of P3HT and the chirality of the helical PPI segment, crystallization-driven asymmetric self-assembly (CDASA) of the block copolymers lead to the formation of single-handed helical nanofibers with controlled length, narrow dispersity, and well-defined helicity. During the self-assembly process, the chirality of helical PPI was transferred to the supramolecular assemblies, giving the helical assemblies large optical activity. The single-handed helical assemblies of the block copolymers exhibited interesting white-light emission and circularly polarized luminescence (CPL). The handedness and dissymmetric factor of the induced CPL can be finely tuned through the variation on the helicity and length of the helical nanofibers. 相似文献