全文获取类型
收费全文 | 710篇 |
免费 | 15篇 |
国内免费 | 1篇 |
专业分类
化学 | 542篇 |
晶体学 | 11篇 |
力学 | 16篇 |
数学 | 33篇 |
物理学 | 124篇 |
出版年
2021年 | 8篇 |
2020年 | 3篇 |
2019年 | 9篇 |
2018年 | 4篇 |
2017年 | 10篇 |
2016年 | 11篇 |
2015年 | 13篇 |
2014年 | 19篇 |
2013年 | 33篇 |
2012年 | 31篇 |
2011年 | 28篇 |
2010年 | 18篇 |
2009年 | 20篇 |
2008年 | 38篇 |
2007年 | 43篇 |
2006年 | 40篇 |
2005年 | 58篇 |
2004年 | 40篇 |
2003年 | 43篇 |
2002年 | 41篇 |
2001年 | 5篇 |
2000年 | 13篇 |
1999年 | 9篇 |
1998年 | 10篇 |
1997年 | 11篇 |
1996年 | 7篇 |
1995年 | 6篇 |
1994年 | 4篇 |
1993年 | 11篇 |
1992年 | 6篇 |
1990年 | 3篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 8篇 |
1984年 | 11篇 |
1983年 | 7篇 |
1982年 | 10篇 |
1981年 | 19篇 |
1980年 | 13篇 |
1979年 | 7篇 |
1978年 | 9篇 |
1977年 | 6篇 |
1976年 | 6篇 |
1975年 | 2篇 |
1973年 | 6篇 |
1972年 | 2篇 |
1969年 | 3篇 |
1966年 | 3篇 |
1962年 | 2篇 |
排序方式: 共有726条查询结果,搜索用时 0 毫秒
81.
Novel unsymmetrical vanadyl and zinc dodecakis(2,2,2‐trifluoroethoxy)phthalocyaninates with an iodo group were synthesized by a statistical condensation route. The palladium‐catalyzed coupling reaction between such monoiodinated metallophthalocyanines and terminal acetylenic derivatives gave various new unsymmetrically dodecakis(2,2,2‐trifluoroethoxy)‐substituted metallophthalocyanines with extended exocyclic π‐conjugation. Unsymmetrical zinc dodecakis(2,2,2‐trifluoroethoxy)phthalocyaninate with a nitro group was also prepared for comparison. All the target phthalocyanines were separated by common col umn chromatography and characterized by elemental analysis, ir and 1H‐nmr, uv‐visible and fast‐atombombardment mass spectroscopy. 相似文献
82.
Hiroyo Ogawa Tatsuo Itoh 《International Journal of Infrared and Millimeter Waves》1986,7(10):1417-1427
The directional coupler and the traveling-wave directional filter made of coupled slow-wave microstrip lines are proposed and their characteristics discussed. These structures exhibit interesting characteristics not readily available in conventional transmission lines.This work is supported by U.S. Army Research Office contract DAAG29-84-K-0076. 相似文献
83.
Masaharu Murata Chifumi Gouda Kentaro Yano Shinichiro Kuroki Tatsuo Suzutani Yoshiki Katayama 《Analytical sciences》2003,19(10):1355-1357
In vitro screening assays are useful techniques for the determination of receptor-mediated activities in environmental samples. In order to define whether environmental chemicals act as an agonist or antagonist to the human estrogen receptor (hER), we have constructed a biosensor based on ligand-inducible interactions between hER and relative proteins on a quartz crystal microbalance (QCM). The his-tagged proteins, which were expressed in E. coli by recombinant DNA technology, were immobilized on an Au-electrode with Ni(II)-mediated chemisorption using the histidine tag and thiol-modified iminodiacetic acid. The resonance-frequency change of the protein-modified electrode was caused by association or dissociation with the hER relative proteins on the surface in the presence of estrogen. These results suggest that this sensor is applicable as a large-scale screening tool for estrogenic compounds. 相似文献
84.
In this Letter, we treat nonlinear sigma models such as the C P1-model, Q P1-model, etc. in 1+2 dimensions. For submodels of such models, we definitely construct an infinite number of nontrivial conserved currents. Our result is a generalization of Alvarez, Ferreira and Guillen. 相似文献
85.
A gold thin film was machined by laser ablation using a femtosecond laser with mask patterns in the shape of lines and numbers. The patterns were successfully transferred with proper focusing and laser fluence. The optimal femtosecond laser fluence to keep the line width was about 5.2 mJ/cm2 on the mask, and 99 mJ/cm2 on the film. The processing resolution was 13 μm, and the narrowest line width was about 4 μm. 相似文献
86.
Tatsuo Narikiyo Junichiro Sahashi Kazutomo Misao 《Nonlinear Analysis: Hybrid Systems》2008,2(2):231-241
In this paper a new control methodology for underactuated mechanical systems is proposed. The basic idea of this method is to combine passive velocity field control with decoupling vector field. In order that the underactuated mechanical systems can be stabilized at the desired position after settling on the desired velocity vector field, novel control strategies are proposed. Proposed control strategies are applied to the underactuated planar three-link manipulator and underactuated planar body. Simulations demonstrate the usefulness and effectiveness of the proposed control methodology. 相似文献
87.
Gabriela Furlan Giordano Luis Carlos Silveira Vieira Angelo Luiz Gobbi Renato Sousa Lima Lauro Tatsuo Kubota 《Analytica chimica acta》2015
An integrated platform was developed for point-of-use determination of ethanol in sugar cane fermentation broths. Such analysis is important because ethanol reduces its fuel production efficiency by altering the alcoholic fermentation step when in excess. The custom-designed platform integrates gas diffusion separation with voltammetric detection in a single analysis module. The detector relied on a Ni(OH)2-modified electrode. It was stabilized by uniformly depositing cobalt and cadmium hydroxides as shown by XPS measurements. Such tests were in accordance with the hypothesis related to stabilization of the Ni(OH)2 structure by insertion of Co2+ and Cd2+ ions in this structure. The separation step, in turn, was based on a hydrophobic PTFE membrane, which separates the sample from receptor solution (electrolyte) where the electrodes were placed. Parameters of limit of detection and analytical sensitivity were estimated to be 0.2% v/v and 2.90 μA % (v/v)−1, respectively. Samples of fermentation broth were analyzed by both standard addition method and direct interpolation in saline medium based-analytical curve. In this case, the saline solution exhibited ionic strength similar to those of the samples intended to surpass the tonometry colligative effect of the samples over analyte concentration data by attributing the reduction in quantity of diffused ethanol vapor majorly to the electrolyte. The approach of analytical curve provided rapid, simple and accurate analysis, thus contributing for deployment of point-of-use technologies. All of the results were accurate with respect to those obtained by FTIR method at 95% confidence level. 相似文献
88.
Urea compounds are useful anion sensors due to their hydrogen-bonding capabilities. We investigated the emissive properties of complexes consisting of urea-anthracene (nPUA, n = 1, 2) host compounds and acetate anions held as guests through intermolecular hydrogen bonding. The kinetics of a new emission band formed by conformational changes in the excited singlet state were revealed. The new band is thought to arise from a charge-transfer interaction between the anthracene and urea moieties after intermolecular hydrogen-bond reconfiguration in the excited state, with rate constants of 2.4 × 10(9) and 4.0 × 10(7) s(-1) for 1PUA and 2PUA, respectively. 相似文献
89.
Kitaura R Iwahori F Matsuda R Kitagawa S Kubota Y Takata M Kobayashi TC 《Inorganic chemistry》2004,43(21):6522-6524
A new three-dimensional (3-D) jungle-gym-like open metal-organic framework has been synthesized from a two-dimensional (2-D) layer compound using a heterogeneous pillar insertion reaction. Both the starting 2-D layer and the resulting 3-D open compounds have been characterized using X-ray crystallography. 相似文献
90.
trans- and cis-1-(4-Dimethylaminophenyl)-6-(4-nitrophenyl)hex-3-ene-1,5-diynes (trans- and cis-DANE) were synthesized and their photochemical properties were studied. The absorption spectra of trans-DANE red-shifted compared with the parent compound bisphenylethynylethene (BEE) due to intramolecular charge transfer. The fluorescence spectra, Stokes shift, fluorescence lifetime, fluorescence quantum yield, and quantum yield of trans-to-cis photoisomerization of trans-DANE showed strong dependence upon the solvent polarity in the less-polar region. No fluorescence emission from trans-DANE was observed in medium-polar and polar solvents. The quantum yield of cis-to-trans isomerization was almost solvent independent. The donor-acceptor substituents shifted the equilibrium between the trans perpendicular triplet state and the trans planar triplet state to the trans triplet state, and resulted in an increase in the triplet lifetime. Comparison of the photochemical properties of trans-DANE with trans-4-dimethylamino-4'-nitrostilbene (DANS) suggests that trans-DANE is a possible fluorescent probe in the non-polar region. 相似文献