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81.
Tooru Kitagawa Yukihiro Abe Kohei Kiriyama 《Journal of Macromolecular Science: Physics》2016,55(8):774-792
The possibility to make a composite poly-p-phenylenebenzobisoxazole (PBO) fiber including a second component without distorting its original structures and mechanical properties was examined. Copper phthalocyanine was found to fulfill the above-mentioned condition and can be dispersed in the fiber molecularly. It was shown that part of the embedded copper phthalocyanine can be aligned one-dimensionally with periodicity along the fiber axis in the fiber. The color of the resultant fiber was dark blue, which is different from the original fiber having its yellowish golden color. According to X-ray diffraction analysis the preferential orientation of the a-axis of the PBO crystal was slightly more oriented by the addition of copper pthalocyanine than that of the pure PBO fiber, but the crystal size of PBO wasn't also affected. We thus show the possibility of adding a second material that can add additional properties to the fiber, but keeping the original high mechanical properties and oriented structures. 相似文献
82.
Abe I Morita H Oguro S Noma H Wanibuchi K Kawahara N Goda Y Noguchi H Kohno T 《Journal of the American Chemical Society》2007,129(18):5976-5980
Pentaketide chromone synthase (PCS) from Aloe arborescens is a novel plant-specific type III polyketide synthase (PKS) that produces 5,7-dihydroxy-2-methylchromone from five molecules of malonyl-CoA. On the basis of the crystal structures of wild-type and M207G mutant PCS, the F80A/Y82A/M207G triple mutant was constructed and shown to produce an unnatural novel nonaketide naphthopyrone by sequential condensations of nine molecules of malonyl-CoA. This is the first demonstration of the formation of a nonaketide by the structurally simple type III PKS. A homology model predicted that the active-site cavity volume of the triple mutant is increased to 4 times that of the wild-type PCS. 相似文献
83.
The Raman spectra of aqueous LnCl(3) x 20H(2)O x CH3(C)OOLi (LnCl(3), rare earth chloride) solutions have been measured in the liquid state. The change of the Raman symmetric Ln(3+)-OH(2) stretching band (v(w)) showed that the decrease in the ionic radius of rare earth (Ln(3+)) ions induces a change in coordination number of the Ln(3+) ion. The two peaks at 946 and 958 cm(-1) of the C-C stretching band (v(CC)) of the acetate ion are assigned to the bidentate ligand and the polymeric chain structure, respectively. The coordination structure of the acetate ion to Ln(3+) ion prefers the bidentate ligand to the polymeric chain structure throughout the rare earth series. The fraction of the bidentate ligand increases with decreasing ionic radius of the Ln(3+) ion. On the basis of the analyses of the v(w) and v(CC) bands, the change in the coordination number of the Ln(3+) ion is mainly due to the structural change (from the polymeric chain structure to the bidentate ligand) of the Ln(3+)-acetate complex rather than a elimination of one water molecule. Our results show that the Ln(3+) ions tend to form the bidentate ligand rather than the divalent (M(2+)) ions. 相似文献
84.
Twelve "health foods" products containing chondroitin sulfate (CS) were purchased from the Japanese market and the origin of the CS was investigated by conducting disaccharide compositional analysis after enzymatic depolymerization and by 1H-NMR spectroscopy. Nine of the 12 products had labels indicating that the origin of the CS was shark cartilage. However, two of them were found to contain mammalian CS. Next, we compared the ratio of the sulfate group to the galactosamine residue after the acid hydrolysis of CS. The results suggest that all of the CS from sharks had a ratio of more than 1.0, while the CS from mammals had a ratio of less than 1.0. Since this comparative analysis does not require expensive purified enzyme, it would be an economical way to identify the origin of CS in "health foods." Being able to determine the origin of the ingredients in natural products is very important for ensuring their quality, safety, and efficacy. Therefore, we think that regulatory requirements for accurately indicating the origin of "health foods" and effective enforcement of these requirements are needed. 相似文献
85.
A triruthenium cluster, (mu3,eta2,eta3,eta5-acenaphthylene)Ru3(CO)7 (1) catalyzes the reaction of secondary amides with hydrosilanes, yielding a mixture of secondary amines, tertiary amines, and silyl enamines. Production of secondary amines with complete selectivity is achieved by the use of higher concentration of the catalyst (3 mol %) and the use of bifunctional hydrosilanes such as 1,1,3,3-tetramethyldisiloxane. Acidic workup of the reaction mixture affords the corresponding ammonium salts, which can be treated with a base, providing a facile method for isolation of secondary amines with high purity. In contrast, tertiary amines are formed with high selectivity by using lower concentration of the catalyst (1 mol %) and polymeric hydrosiloxanes (PMHS) as reducing agent. Reduction with PMHS encapsulates the ruthenium catalyst and organic byproducts to the insoluble silicone resin. The two reaction manifolds are applicable to various secondary amides and are practical in that the procedures provide the desired secondary or tertiary amine as a single product. The product contaminated with only minimal amounts of ruthenium and silicon residues. On the basis of the products and observed side products as well as NMR studies a mechanistic scenario for the reaction is also described. 相似文献
86.
A process of water sorption into a biocompatible polymer, poly(2-methoxyethyl acrylate) (PMEA), was investigated by time-resolved, in situ, attenuated total reflection infrared spectroscopy. Evidence for three different types of hydrated water in PMEA, that is, nonfreezing water, freezing bound water, and freezing water, were found. Each hydration structure was elucidated at the functional group level. Nonfreezing water, which never crystallizes, even at -100 degrees C, has a C=O...H-O type of hydrogen bonding interaction with the carbonyl group of PMEA. Freezing bound water, which crystallizes in a heating process below 0 degrees C, interacts with the methoxy moiety in the PMEA side chain terminal. Freezing water, which crystallizes approximately 0 degrees C, has bulk-water-like structure with an O-H...O-H hydrogen bonds network. It has been concluded from the present study that the methoxy moiety in the PMEA side chain terminal plays an important role for the excellent biocompatibility of PMEA. 相似文献
87.
Harumi Sato Rumi Murakami Jianming Zhang Katsuhito Mori Isao Takahashi Hikaru Terauchi Isao Noda Yukihiro Ozaki 《Macromolecular Symposia》2005,230(1):158-166
Infrared (IR) spectra and wide-angle X-ray diffraction (WAXD) patterns of poly(3-hydroxybutyrate) (PHB) and its copolyester, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), P(HB-co-HHx) (HHx = 12 mol%) were measured over a temperature range of 20 °C to higher temperatures (PHB, 185 °C, HHx = 12 mol%, 140 °C) to explore their structure change and thermal behavior and molecular interaction. The WAXD measurements revealed that the a lattice parameter increases significantly with temperature, while the b lattice parameter varies a little in the crystalline PHB and P(HB-co-HHx). It seems that the intermolecular interaction between the CO group of one helical structure and the CH3 group of the other helical structure decreases along the a axis of crystalline PHB and P(HB-co-HHx) with temperature. The temperature-dependent IR spectral variations were analyzed for the CH stretching, CO stretching, CH3 deformation, and C O C stretching variation regions, and bands characteristic of crystalline and amorphous parts were identified in each region. It was found from the anomalous frequencies of the CH3 asymmetric stretching and CO stretching bands of PHB and P(HB-co-HHx) and the X-ray crystallographic structure of PHB that there is an intermolecular interaction (C H…OC hydrogen bond) between the CO group and the CH3 group combining two helical structures in PHB and P(HB-co-HHx). In this review paper we discuss the role of the C H…OC hydrogen bonding and the crystal and lamella structure of PHB and P(HB-co-HHx) (HHx = 12 mol %) in comparison with the structure of Nylon. 相似文献
88.
Jian Dong Yukihiro Ozaki Kenichi Nakashima 《Journal of Polymer Science.Polymer Physics》1997,35(3):507-515
Fourier transform infrared (FTIR) spectroscopic measurements have been undertaken to estimate the conformational energies of poly(acrylic acid) (PAA) cast films in the temperature range of 40–130°C. The temperature dependence of the IR spectra in the C=O stretching region has been analyzed to yield the side-chain and backbone conformational energies. The estimated energies are close to those previously obtained by polarized Raman spectroscopic measurements for PAA solutions. Combining the FTIR value of conformational energy with the simplified rotational isomeric state (RIS) model proposed in the Raman analysis provides a persistence length in accordance with earlier SAXS experiments. The data also agree with the Gibbs-DiMarzio predictions, further substantiating the validity of the analysis. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys, 35: 507–515, 1997 相似文献
89.
Objective: Anterior cruciate ligament (ACL) injury is one of the most frequent sportsinjuries, and previous studies have shown that fatigue is a risk factor for sports injuries.This study aimed to inform prevention of ACL injury by investigating how exercise and desk tasks affect trunk and lower limb alignment and ground reaction force (GRF) during one-legged landing movements. Methods: The study subjects were 12 men who performed a one-legged landing movement from a 30-cm platform before and after fatigue tasks, including lower-limb muscle fatigue, cardiopulmonary fatigue, and brain fatigue tasks. For the measurement of joint angles and moments and GRF, a three-dimensional motion analysis device and a floor reaction-force meter were used. Statistics were performed using Wilcoxon''s signed rank sum test as a multiple comparison test with Bonferroni adjustment to compare the difference in effects. Results: The maximum trunk flexion angle during landing on one leg was significantly lower in the brain fatigue group than in the control group. The time to peak vertical GRF (pGRF) was significantly shorter in the leg-muscle fatigue group than in the control group. Conclusion: Brain fatigue may have altered the postural strategy before and after landing, resulting in a decrease in trunk flexion angle. Time to pVGRF was shortened in the leg muscle fatigue group, suggesting that there may be an increased risk of ACL injury. Time to pVGRF during lower extremity muscle fatigue and trunk flexion angle during brain fatigue may be more pronounced during actual sports activities. 相似文献
90.