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排序方式: 共有149条查询结果,搜索用时 15 毫秒
61.
Determination of estazolam in plasma by high-performance liquid chromatography with solid-phase extraction. 总被引:1,自引:0,他引:1
Masatomo Miura Tadashi Ohkubo Kazunobu Sugawara Naoyuki Okuyama Koichi Otani 《Analytical sciences》2002,18(5):525-528
A high-performance liquid chromatography (HPLC) assay was developed for the determination of estazolam in human plasma. Estazolam and alprazolam as an internal standard were detected by ultraviolet absorbance at 240 nm. Estazolam in plasma was extracted by a rapid and simple procedure based on cyanopropyl bonded-phase extraction. Chromatographic separation was achieved with a reversed-phase C8-5 column using a mobile phase of 0.5% potassium dihydrogenphosphate(pH 4.5)-acetonitrile (70:30, v/v). The determination of estazolam was possible in the concentration range of 1.0 - 200.0 ng/mL. The mean recovery of estazolam added to plasma was 96.1 +/- 1.5% with coefficients of variation of less than 5.5%. This method is applicable for accurately monitoring the plasma level of estazolam in healthy subjects participating in scientific research. 相似文献
62.
Lithiation of 1′,2′,3′,4′,5′-pentamethylazaferrocene (1) with sec-BuLi/(−)-sparteine (3) in Et2O at −78°C followed by quenching with electrophiles gave the ring-substituted products 2 in 74-81% ee. On the other hand, lithiation of 1′,2,2′,3′,4′,5,5′-heptamethylazaferrocene (6) with sec-BuLi in the presence of S-valine-derived bis(oxazoline) 5 in Et2O at −55°C and subsequent reaction with electrophiles afforded the laterally functionalized products 7 in excellent enantioselectivity (96-99% ee). 相似文献
63.
A new model of a sandwich-type bipolar membrane potential was constructed by assuming the potential behavior of a bipolar membrane as a combination of each layer potential between two different states, i.e. the different concentrations of the bulk solution. Hence, we introduced the coion exclusion parameter that is derived from the Donnan equilibrium as a combinatorial function, which combined all the potential equations involved in our system. We assumed that the existence of the intermediate phase due to its volume would allow the Donnan equilibrium to play an important role, i.e. the vanishing of the coion exclusion effect of the membrane layer facing the bulk solution phase in high concentration. Sandwich-type bipolar membranes, which consist of a cation- (K-501) and an anion-exchange layer (A-501) were used in this study. A series of concentration perturbations of the intermediate phase was performed to examine the membrane potential behavior of the bipolar membrane experimentally. The experimental results showed a good agreement with the theoretical results, which led to the conclusion that explained the contribution of the intermediate phase to the membrane potential behavior through its volume and electrochemical properties. 相似文献
64.
Undoped Layered Perovskite Oxynitride Li2LaTa2O6N for Photocatalytic CO2 Reduction with Visible Light
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Takayoshi Oshima Tom Ichibha Ken Sinkou Qin Kanemichi Muraoka Dr. Junie Jhon M. Vequizo Keisuke Hibino Ryo Kuriki Dr. Shunsuke Yamashita Prof. Dr. Kenta Hongo Dr. Tomoki Uchiyama Prof. Dr. Kotaro Fujii Dr. Daling Lu Prof. Dr. Ryo Maezono Prof. Dr. Akira Yamakata Prof. Dr. Hideki Kato Dr. Koji Kimoto Prof. Dr. Masatomo Yashima Prof. Dr. Yoshiharu Uchimoto Prof. Dr. Masato Kakihana Prof. Dr. Osamu Ishitani Prof. Dr. Hiroshi Kageyama Prof. Dr. Kazuhiko Maeda 《Angewandte Chemie (International ed. in English)》2018,57(27):8154-8158
Oxynitrides are promising visible‐light‐responsive photocatalysts, but their structures are almost confined with three‐dimensional (3D) structures such as perovskites. A phase‐pure Li2LaTa2O6N with a layered perovskite structure was successfully prepared by thermal ammonolysis of a lithium‐rich oxide precursor. Li2LaTa2O6N exhibited high crystallinity and visible‐light absorption up to 500 nm. As opposed to well‐known 3D oxynitride perovskites, Li2LaTa2O6N supported by a binuclear RuII complex was capable of stably and selectively converting CO2 into formate under visible light (λ>400 nm). Transient absorption spectroscopy indicated that, as compared to 3D oxynitrides, Li2LaTa2O6N possesses a lower density of mid‐gap states that work as recombination centers of photogenerated electron/hole pairs, but a higher density of reactive electrons, which is responsible for the higher photocatalytic performance of this layered oxynitride. 相似文献
65.
In this study, the effect of cationic surfactant (benzalkonium chloride) on the transport of KCl through a sulfonated styrene-divinyl benzene cation-exchange membrane was investigated. The presence of benzalkonium chloride as the cationic surfactant, which interacts with the sulfonic groups on membrane surface, has to disturb the transport of K+ ions and directly gives responses in its chronopotentiogram. The electrodialysis of the cationic surfactant solution showed an irreversible monotonous increase of the total system potential due to the fouling phenomena. However, a small amount of cationic surfactant in the membrane surface vicinity was observed to give a fluctuating chronopotentiogram at the high current density. This fluctuation is started by a steep increase and followed by the decrease of potential, which finally relaxed to reach a steady state. This potential fluctuation is proposed to be the response of a structural transformation of surfactant micelles on the membrane surface under perturbation of the externally applied electric field, which is discussed and examined qualitatively in this report. 相似文献
66.
T. Danno H. Matsumoto M. Nasir S. Shimizu M. Minagawa J. Kawaguchi H. Horibe A. Tanioka 《Journal of Polymer Science.Polymer Physics》2008,46(6):558-563
The fine structure of poly(vinylidene fluoride) (PVDF) nanofiber prepared by electrospray deposition (ESD) has been investigated by wide angle X‐ray diffraction (WAXD) and infrared spectroscopy (IR). The β‐phase crystal was dominant in the crystalline region. The degree of crystallinity of 0.54 for the nanofiber, determined by Ruland's method, was almost identical to that for a melt pressed sheet of PVDF. The disorder parameter k was 4, which is significantly smaller than the value of 6 for the melt pressed sheet of PVDF. Molecular orientation along the fiber axis was observed by the polarized infrared spectra of the uniaxially aligned nanofiber. These results suggest that the PVDF nanofiber possesses a fiber structure which is by no means inferior to that of practical fibers. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 558–563, 2008 相似文献
67.
Matsumoto H Wakamatsu Y Minagawa M Tanioka A 《Journal of colloid and interface science》2006,293(1):143-150
Ion-exchange fiber (IEF) fabrics were prepared by electrospray deposition (ESD) and post-deposition chemical modification of their surfaces. Nonwoven fibrous fabrics were obtained from the solutions of synthetic polymers-polystyrene (PS) and poly(4-vinylpyridine) (P4VP)-of various concentrations. The diameter of the fiber in the fabrics ranged from 600 nm to 1.70 microm. Cation- and anion-exchange fiber (CEF and AEF) fabrics were obtained from the sulfonation of PS fabrics and the quaternization of P4VP fabrics, respectively. These fabrics were thoroughly characterized by a series of techniques, such as scanning electron microscopy (SEM), permporometry, nitrogen adsorption measurements, and potentiometric titrations. The SEM images showed that the fabrics had a porous structure after their chemical modification. The mean pore size, porosity, and specific surface area of the flow-through pores were 1.67-3.53 microm, about 80%, and 13 m(2)/g, respectively. The ion-exchange capacity was in the range from 0.78 to 1.34 mmol/g. The AEF fabric, on the other hand, showed a high specific surface area, i.e., the Brunauer-Emmett-Teller (BET) surface area of 600 m(2)/g, due to the formation of much smaller pores on the surface of the fiber structure in the fabric. The secondary chemical modification of the nano-microfiber fabrics by ESD provides novel functional materials with a large adsorption capacity and a high catalytic activity. 相似文献
68.
M. Minagawa K. Hashimoto H. Shirai T. Morita F. Yoshii 《Colloid and polymer science》2000,278(4):352-357
The dependence of the dissolution temperature (T
sol) of isotactic polyacrylonitrile (PAN) on tacticity was studied for three dinitrile solvents. A linear relationship was obtained
in the inverse plots of the tacticity dependence of the T
sol of PAN. A phenomenological analogy between the tacticity dependence of the T
sol of isotactic PAN and the molecular-weight dependence of the glass-transition temperature of amorphous polystyrene is discussed
from a thermodynamic point of view. The linear relationships in both phenomena are explained in terms of a common mechanism:
a breakdown of thermodynamic competition, enthalpy, and entropy through the segment mobility. The significance of segment
concept and molecular mobility at elevated temperatures are discussed.
Received: 7 July 1999/Accepted in revised form: 21 October 1999 相似文献
69.
Takeshi Mori Takushi Watanabe Keiji Minagawa Masami Tanaka 《Journal of polymer science. Part A, Polymer chemistry》2005,43(8):1569-1578
Rod–coil amphiphilic diblock copolymers, consisting of oligo(p‐phenylenevinylene) (OPV) as a rod and hydrophobic block and poly(ethylene oxide) (PEO) as a coil and hydrophilic block, were synthesized by a convergent method. The aggregation behavior of the block copolymers in a selective solvent (tetrahydrofuran/H2O) was probed with the absorption and emission of the OPV block. With increasing H2O concentration, the absorption maximum was blueshifted, the emission from the molecularly dissolved OPV decreased, and that from the aggregated OPV increased. This indicated that the OPV blocks formed H‐type aggregates in which the OPV blocks aligned in a parallel orientation with one another. The transmission electron microscopy observation revealed that the block copolymers with PEO weight fractions of 41 and 62 wt % formed cylindrical aggregates with a diameter of 6–8 nm and a length of several hundreds nanometers, whereas the block copolymer with 79 wt % PEO formed distorted spherical aggregates with an average diameter of 13 nm. Furthermore, the solubilization of an OPV homooligomer with the block copolymer was studied. When the total polymer concentration was less than 0.1 wt %, the block copolymer solubilized OPV with a 50 mol % concentration. The structure of the aggregates was a cylinder with a relatively large diameter distribution. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1569–1578, 2005 相似文献
70.
The preparation and characterization of stereoregular isotactic polyacrylonitrile (PAN) by electron beam (EB) irradiation
on a urea canal complex are described. The EB method has several advantages over the ordinary γ-ray irradiation method: a
very short polymerization time is needed (within a few seconds) and EB irradiation is carried out intermittently, and so all
the polymer properties can be studied as a function of the EB irradiation dose. The structure–properties relationships of
PAN, such as intrinsic viscosity versus the number-average molecular weight and the viscosity versus the isotacticity range
were clarified. Significant information for the optimization of the tacticity of PAN was extracted.
Received: 23 August 1999 Accepted : 10 January 2000 相似文献