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971.
The propagation of light rays in a slab-waveguide whose dielectric constant varies radially with a quadratic law but has fourth and sixth order terms in it is described. Exact solutions consisting of Jacobi elliptic functions are shown. The exact ray trajectory and delay time of an optical pulse, therefore, can be obtained. The results show that the optimum fourth-order and sixth-order coefficients are near 2/3 and 17/45, respectively. 相似文献
972.
Ichiro Noda Toshiaki Kitano Mitsuru Nagasawa 《Journal of Polymer Science.Polymer Physics》1977,15(7):1129-1142
The effect of molecular weight heterogeneity on the second virial coefficient A2 in good solvents is studied for binary mixtures of monodisperse poly(α-methylstyrenes). It is concluded that A2 for polymer mixtures passes through a maximum with variation of the mixing ration. From comparison with the data, it is concluded that no available theory quantitatively explains both the molecular weight dependence of A2 of monodisperse polymer and the variation of A2 of mixtures with the mixing ratio. The interpenetration function for two polymer coils with different molecular weights is discussed on the assumption that the thermodynamic interaction between two polymer coils in good solvents can be approximated by a hard-sphere model. 相似文献
973.
An experimental study of the dynamic shear flow properties of polyethylene melts filled with glass fibers and vinylon fibers was carried out and comparison with the steady shear flow properties was made. The effects of loading level and the characteristics of the fibers on the rheological properties of the fiber-filled systems is discussed. The rigidity and complex viscosity of the fiber-filled systems is sensitive not only to the quantity of fibers but also to their length, distribution and properties. The Cox-Merz empirical law for complex viscosity and steady shear viscosity, and Roscoe's empirical relation for estimating the normal-stress coefficients are both able to be applied to pure polymer melts but not to fiber-filled systems. 相似文献
974.
Tomoyuki Sekine Kunimitsu Uchinokura Haruo Iimura Ryozo Yoshizaki Etsuyuki Matsuura 《Solid State Communications》1984,51(4):187-189
The successive phase transitions of the cubic spinel structure CuV2S4 have been studied by the electrical resistivity and the specific heat. In the resistivity and the specific heat two anomalies have been observed at T1~91 K and T3≈55 K. The specific heat indicates that the phase transition at T1 is in the vicinity of a tricritical point, where the resistivity has a small sharp peak. On the other hand, the specific heat shows a step at T3, where a hysteresis of the resistivity indicates the existence of the first-order phase transition. 相似文献
975.
A gradient-index rod lens was fabricated by the new ion-exchange technique, in which another dopant was added to the fused salt. It was found that this dopant remained only in the merginal region of the glass rod and modified the improper refractive index distribution in this region. The lens has high numerical aperture of 0.6 and gives good results in the light focusing system and the light source coupling system. 相似文献
976.
Tomoyuki Shirai 《Transactions of the American Mathematical Society》2000,352(1):115-132
Let be an infinite -regular graph and its line graph. We consider discrete Laplacians on and , and show the exact relation between the spectrum of and that of . Our method is also applicable to -semiregular graphs, subdivision graphs and para-line graphs.
977.
Sulfoxide-promoted ortho-C–H functionalization reactions of aromatic compounds have emerged as powerful tools for organic synthesis. Among them, [3,3] sigmatropic rearrangement induced by interrupted Pummerer reaction or electrophilic activation of sulfoxides has proved to be a fruitful strategy due to its versatility and high reaction efficiency. This digest paper mainly focuses on recent progress on C–H functionalization reactions of aryl sulfoxides via [3,3] sigmatropic rearrangement of sulfonium-tethered intermediates. 相似文献
978.
Dr. Masaru Fujibayashi Yu Watari Dr. Ryo Tsunashima Prof. Sadafumi Nishihara Prof. Shin-ichiro Noro Dr. Chang-Gen Lin Prof. Yu-Fei Song Dr. Kiyonori Takahashi Prof. Takayoshi Nakamura Prof. Tomoyuki Akutagawa 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(50):22632-22636
The structural phase of a metal oxide changes with temperature and pressure. During phase transitions, component ions move in multidimensional metal–oxygen networks. Such macroscopic structural events are robust to changes in particle size, even at scales of around 10 nm, and size effects limiting these transitions are particularly important in, for example, high-density memory applications of ferroelectrics. In this study, we examined structural transitions of the molecular metal oxide [Na@(SO3)2(n-BuPO3)4MoV4MoVI14O49]5− (Molecule 1 ) at approximately 2 nm by using single-crystal X-ray diffraction analysis. The Na+ encapsulated in the discrete metal-oxide anion exhibited a reversible order–disorder transition with distortion of the Mo–O molecular framework induced by temperature. Similar order–disorder transitions were also triggered by chemical pressure induced by removing crystalline solvent molecules in the single-crystal state or by substituting the countercation to change the molecular packing. 相似文献
979.
A diarylethene possessing one [4]thiaheterohelicene and one benzothiophene, the latter with a chiral methoxymethoxyethyl group on its C-3 position, was proved to work as a switch of specific optical rotation at a wavelength at which both colored and colorless forms have no absorption in solution. The difference of the specific optical rotation was 1300 degrees between the open form and the photostationary state. The specific optical rotation of one of the isolated optically active major colored forms was -4680 degrees. The conversion to the colored form was 64%, and the diastereomeric excess of photocyclization was 47%. 相似文献
980.
Tomoyuki Mochida Fumiko Shimizu Kazuya Okazawa Daisuke Kuwahara 《Journal of organometallic chemistry》2007,692(9):1834-1844
The crystal architectures of 5-ferrocenylpyrazole (1) and its metal complexes were investigated. Compound 1 can form non-solvated and chloroform-solvated crystals. In both cases, 1 forms a zigzag one-dimensional architecture via NH?N hydrogen bonds. The hydrogen bond exhibits a twofold disorder, which was shown to be static by solid-state 13C NMR. In the solvated crystal, the chloroform is released at 415 K, associated with melting of the crystal. The reaction of 1 with metal salts provided metal-centered ferrocenyl clusters [Zn(NO3)2(1)4] (4), [Co(NO3)2(1)4] (5), [CoCl2(1)4] (6), [Zn(NCS)2(1)2] (7), cis-[Pt(NH3)2(1)2](PF6)2 (8), and trans-[Pt(NH3)2(1)4](PF6)2 (9). In all of these complexes, 1 acts as a monodentate ligand. In 4, 5, and 7, the multinuclear units are joined via hydrogen bonds to form supramolecular chains. Two polymorphs were found for the crystals of 4. Both are composed of the same hydrogen-bonded chains, but their arrangements are different. 5-Ferrocenyl-1-tritylpyrazole (2) and 4-ferrocenyl-1-methylpyrazole (3) were also crystallographically characterized. 相似文献