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排序方式: 共有1007条查询结果,搜索用时 15 毫秒
81.
Jae Chul Cheong Sung Ill Suh Beom Jun Ko Jin Young Kim Moon Kyo In Won Jo Cheong 《Journal of separation science》2010,33(12):1767-1778
A simple and rapid GC‐MS method has been developed for the screening and quantification of many illicit drugs and their metabolites in human urine by using automatic SPE and trimethylsilylation. Sixty illicit drugs, including parent drugs and their metabolites that are possibly abused in Korea, can be monitored by this method. Among them, 24 popularly abused illicit drugs were selected for quantification. Very delicate optimizations were carried out in SPE, trimethylsilylation derivatization, and GC/MS to enable such remarkable achievements. Trimethylsilylated analytes were well separated within 21 min by GC‐MS. In the validation results, the LOD of all the analytes were in the range of 2–75 ng/mL. The LOQ of the quantified analytes were in the range of 5–98 ng/mL. The linearity (r2) of the quantified analytes ranged 0.990–1.000 in each concentration range between 10 and 1000 ng/mL. The mean recoveries ranged from 62 to 126% at three different concentrations of each analyte. The inter‐day and inter‐person accuracies were within ?13.3~14.9%, and ?10.1~13.0%, respectively, and the inter‐day and inter‐person precisions were less than 12.9%. The method was reliable and efficient for the screening and quantification of abused illicit drugs in routine urine analysis. 相似文献
82.
Junoh Kim Jongwon Shim Yong‐Jin Kim Kookheon Char Kyung‐Do Suh Jin‐Woong Kim 《Macromolecular bioscience》2010,10(10):1171-1176
This study reports a facile and practical means to non‐invasively deliver biologically active ingredients through the skin using polymer‐based nanocarriers. For this, polymer nanocapsules were fabricated with different surface charges as well as glass transition temperatures and we observed their ability to deliver the encapsulated active ingredient, coenzyme Q10, through the skin layer. Direct imaging of a probe molecule, Nile Red, and a matrix polymer labeled with fluorescence moiety, Lucifer Yellow, allowed us to demonstrate that the probe molecule readily permeates into the deep skin, while the matrix polymer stays in the stratum corneum layer due to electrostatic interactions. Quantitative characterization of the penetrating amount of coenzyme Q10 using the Frantz cell method proved that, to achieve improved delivery efficiency, the nanocapsule should have a low glass transition temperature as well as positive surface charges.
83.
Duy-Thach PhanGwiy-Sang Chung 《Applied Surface Science》2011,257(9):4339-4343
Zinc oxide (ZnO) thin films were deposited on unheated silicon substrates via radio frequency (RF) magnetron sputtering, and the post-deposition annealing of the ZnO thin films was performed at 400 °C, 600 °C, 800 °C, and 1000 °C. The characteristics of the thin films were investigated by X-ray diffractometry (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM). The films were then used to fabricate surface acoustic wave (SAW) resonators. The effects of post-annealing on the SAW devices are discussed in this work. Resulting in the 600 °C is determined as optimal annealing temperature for SAW devices. At 400 °C, the microvoids exit between the grains yield large root mean square (RMS) surface roughness and higher insertion losses in SAW devices. The highest RMS surface roughness, crack and residual stress cause a reduction of surface velocity (about 40 m/s) and increase dramatically insertion loss at 1000 °C. The SAW devices response becomes very weak at this temperature, the electromechanical coupling coefficient (k2) of ZnO film decrease from 3.8% at 600 °C to 1.49% at 1000 °C. 相似文献
84.
Carlos J. G. Machado J. D. Pérez I. Jeong Y. J. Suh 《Annali di Matematica Pura ed Applicata》2014,193(2):591-608
In this paper, we give non-existence theorems for Hopf hypersurfaces in complex two-plane Grassmannians $G_2(\mathbb{C }^{m+2})$ with $\mathfrak D $ -parallel normal Jacobi operator ${\bar{R}}_N$ and $\mathfrak D $ -parallel structure Jacobi operator $R_{\xi }$ if the distribution $\mathfrak D $ or $\mathfrak D ^{\bot }$ component of the Reeb vector field is invariant by the shape operator, respectively. 相似文献
85.
Regarding the generalized Tanaka-Webster connection, we considered a new notion of \(\mathfrak{D}^ \bot\) -parallel structure Jacobi operator for a real hypersurface in a complex two-plane Grassmannian G 2(? m+2) and proved that a real hypersurface in G 2(? m+2) with generalized Tanaka-Webster \(\mathfrak{D}^ \bot\) -parallel structure Jacobi operator is locally congruent to an open part of a tube around a totally geodesic quaternionic projective space ?P n in G 2(? m+2), where m = 2n. 相似文献
86.
Lee, Kim and Suh (2012) gave a characterization for real hypersurfaces M of Type (A) in complex two plane Grassmannians G 2(? m+2) with a commuting condition between the shape operator A and the structure tensors φ and φ 1 for M in G 2(? m+2). Motivated by this geometrical notion, in this paper we consider a new commuting condition in relation to the shape operator A and a new operator φφ 1 induced by two structure tensors φ and φ 1. That is, this commuting shape operator is given by φφ 1 A = A φφ 1. Using this condition, we prove that M is locally congruent to a tube of radius r over a totally geodesic G 2(? m+1) in G 2(? m+2). 相似文献
87.
Hooyoung Song Jooyoung Suh Eun Kyu Kim Kwang Hyeon Baik Sung-Min Hwang 《Journal of Crystal Growth》2010,312(21):3122-3126
Nonpolar (1 1–2 0) a-plane GaN films have been grown using the multi-buffer layer technique on (1–1 0 2) r-plane sapphire substrates. In order to obtain epitaxial a-plane GaN films, optimized growth condition of the multi-buffer layer was investigated using atomic force microscopy, high resolution X-ray diffraction, and transmission electron microscopy measurements. The experimental results showed that the growth conditions of nucleation layer and three-dimensional growth layer significantly affect the crystal quality of subsequently grown a-plane GaN films. At the optimized growth conditions, omega full-width at half maximum values of (11–20) X-ray rocking curve along c- and m-axes were 430 and 530 arcsec, respectively. From the results of transmission electron microscopy, it was suggested that the high crystal quality of the a-plane GaN film can be obtained from dislocation bending and annihilation by controlling of the island growth mode. 相似文献
88.
Jang-Jung Kim Sook-Hyun Kim Seung-Wook Suh Dong-Uk Choe Byung-Ki Park Jae-Rock Lee Young-Seak Lee 《Journal of Crystal Growth》2010,312(22):3410-3415
Polycrystalline Bi2Te3 nanowires were prepared by a hydrothermal method that involved inducing the nucleation of Bi atoms reduced from BiCl3 on the surface of Te nanowires, which served as sacrificial templates. A Bi–Te alloy is formed by the interdiffusion of Bi and Te atoms at the boundary between the two metals. The Bi2Te3 nanowires synthesized in this study had a length of 3–5 μm, which is the same length as that of the Te nanowires, and a diameter of 300–500 nm, which is greater than that of the Te nanowires. The experimental results indicated that volume expansion of the Bi2Te3 nanowires was a result of the interdiffusion of Bi and Te atoms when Bi was alloyed on the surface of the Te nanowires. The morphologies of Bi2Te3 are strongly dependent on the reaction conditions such as the temperature and the type and concentration of the reducing agent. The morphologies, crystalline structure and physical properties of the product were analyzed by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED) and X-ray photoelectron spectroscopy (XPS). 相似文献
89.
Amphiphilic urethane acryale hydrogels containing ionic groups (dimethylolpropionic acid) were prepared by varying the molecular
weight of the soft segment (polyether type) and the type of diisocyanate, and their mechanical properties were examined. They
showed heterophasic gel structure composed of ionic hard domains induced by aggregation of the ionic groups and polyether
soft domains comprising the urethane acrylate network. This heterophasic structure could be confirmed by dynamic mechanical
analysis (DMA) and by wide-angle X-ray scattering analysis (WAXS); the crystallinity detected by WAXS and the transition peak
of the ionic hard domains detected by DMA strongly suggested that there were ionic aggregates. These ionic aggregates acted
as reinforcing fillers in the network, which eventually enhanced the tensile strength of the hydrogels. Above all, the tensile
properties of the hydrogels were of interest in that the trends of the stress-strain curves were consistent with the rubbery
ones. It is believed that the higher purity of the polyether soft domains resulted from the heterophasic gel structure imparting
further elastomeric properties on the network.
Received: 31 July 1998 Accepted in revised form: 15 October 1998 相似文献