首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   420篇
  免费   9篇
  国内免费   1篇
化学   231篇
晶体学   13篇
力学   23篇
数学   78篇
物理学   85篇
  2023年   2篇
  2022年   11篇
  2021年   14篇
  2020年   15篇
  2019年   7篇
  2018年   7篇
  2017年   9篇
  2016年   18篇
  2015年   15篇
  2014年   19篇
  2013年   21篇
  2012年   20篇
  2011年   27篇
  2010年   17篇
  2009年   10篇
  2008年   15篇
  2007年   15篇
  2006年   12篇
  2005年   14篇
  2004年   8篇
  2003年   10篇
  2002年   10篇
  2001年   7篇
  2000年   7篇
  1999年   4篇
  1998年   6篇
  1997年   6篇
  1996年   8篇
  1995年   8篇
  1994年   10篇
  1993年   7篇
  1992年   3篇
  1991年   7篇
  1990年   5篇
  1989年   5篇
  1988年   3篇
  1987年   8篇
  1986年   7篇
  1985年   4篇
  1984年   4篇
  1983年   2篇
  1982年   3篇
  1981年   3篇
  1979年   2篇
  1978年   5篇
  1977年   2篇
  1976年   2篇
  1973年   1篇
  1965年   1篇
  1961年   1篇
排序方式: 共有430条查询结果,搜索用时 15 毫秒
121.
We present a detailed analysis of the nonperturbativeβ function along the Wilson axis for theSU(3) pure gauge theory using the Monte Carlo renormalization group method. The scaling behavior of the string tension, the deconfinement transition temperature, and the O++ glueball mass obtained from published data is compared. The results show that there is no asymptotic scaling forK F=(6/g 2)<6.1. We also estimate the renormalized action generated by the √3 block transformation for use in future calculations.  相似文献   
122.
In this paper, a theoretical analysis is carried out to estimate the sensitivity and the signal-to-noise ratio (SNR) of a fiber optic surface plasmon resonance (SPR) sensor when fibers with different dopants and different doping concentrations are used. The dopants considered are germanium oxide (GeO2), boron oxide (B2O3), and phosphorus pentoxide (P2O5) in a pure silica fiber. The variation of the dispersion relation with different dopants and doping concentrations are taken into account for the analysis. It is shown that the doping of B2O3 increases the sensitivity of the sensor while the effect of dopant on SNR is negligible. The analysis is extended to fiber optic SPR sensor with bimetallic layers.  相似文献   
123.
MRI characterization of 9L-glioma in rat brain at 4.7 Tesla   总被引:3,自引:0,他引:3  
In vivo estimation of intracranial tumor progression is important in tumor treatment response studies in animal models. High resolution MR images at 4.7 T of 9L-gliomas stereotactically implanted in Fisher-344 rat brains were obtained. Due to elongation of T1 at higher fields, tissue contrast is diminished in T1-weighted images. However, normal anatomy and vasogenic edema are clearly discerned in T2-weighted images (echo times of greater than 50 ms and recycle times of greater than 2 sec). Tumor tissue is not always clearly delineated. Images obtained after administration of contrast agents (Gadolinium DTPA), with short TR (0.6 sec) selectively enhanced the tumorous tissue, with little effect upon normal tissue and edema. Good correlation of enhanced tumor lesions has been observed with histological examination of formalin fixed brains. Relaxation times (T1 and T2) of tumor and normal tissues were measured using stimulated-echo and multi-echo sequences, respectively. Serial images corresponding to tumor growth were recorded, from which tumor volume progression was monitored.  相似文献   
124.
Adsorption and expression of penicillin G acylase was studied on macroporous methacrylate polymer beads of differing pore volume, generated with kerosene. The absorption and expression of the penicillin G acylase was dependent on pore volume. Maximum expression of 57% of adsorbed enzyme was obtained on beads synthesized with 40 mL of kerosene, indicating minimum pore-diffusion limitations.  相似文献   
125.
Correlations to predict droplet size in ultrasonic atomisation.   总被引:2,自引:0,他引:2  
R Rajan  A B Pandit 《Ultrasonics》2001,39(4):235-255
In conventional two fluid nozzles, the high velocity air imparts its energy to the liquid and disrupts the liquid sheet into droplets. If the energy for liquid sheet fragmentation can be supplied by the use of ultrasonic energy, finer droplets with high sphericity and uniform size distribution can be achieved. The other advantage of ultrasound induced atomisation process is the lower momentum associated with ejected droplets compared to the momentum carried by the droplets formed using conventional nozzles. This has advantage in coating and granulation processes. An ultrasonic probe sonicator was designed with a facility for liquid feed arrangement and was used to atomise the liquid into droplets. An ingenious method of droplet measurement was attempted by capturing the droplets on a filter paper (size variation with regard to wicking was uniform in all cases) and these are subjected to image analysis to obtain the droplet sizes. This procedure was evaluated by high-speed photography of droplets ejected at one particular experimental condition and these were image analysed. The correlations proposed in the literature to predict droplet sizes using ultrasound do not take into account all the relevant parameters. In this work, a truly universal correlation is proposed which accounts for the effects of physico-chemical properties of the liquid (flow rate, viscosity, density and surface tension), and ultrasonic properties like amplitude, frequency and the area of vibrating surface. The significant contribution of this work is to define dimensionless numbers incorporating ultrasonic parameters, taking cue from the conventional numbers that define the significance of different forces involved in droplet formation. The universal correlations proposed are robust and can be used for designing ultrasonic atomisers for different applications. Among the correlations proposed here, those ones that are based on the dimensionless numbers and Davies approach predict droplet sizes within acceptable limits of deviation. Also, an empirical correlation from experimental data has been proposed in this work.  相似文献   
126.
Journal of Sol-Gel Science and Technology - Biocompatibility and bacterial infections are the primary concerns associated with the current bone graft substitutes. The application of...  相似文献   
127.
The growth of semicarbazone of p-hydroxy benzaldehyde (SPHB) single crystal by slow evaporation solution growth technique is reported in this article. The grown crystal was subjected to powder XRD study to identify the crystalline nature. Single crystal XRD study was done to measure unit cell parameters and to confirm the crystal structure. In the presence of various functional groups of SPHB was identified by FTIR spectrum. Its optical behavior was examined by UV?CVis?CNIR spectrum and the crystal was found to have transparency in the region between 245 and 1100?nm. Thermal properties of the crystal were investigated using thermogravimetric and differential thermal analysis (TG-DTA), which indicated that the melting of the material occurred before decomposition. The nonlinear optical (NLO) property was tested by Kurtz?CPerry powder technique for second harmonic generations.  相似文献   
128.
129.
Since presentation of the 2013 Murray Lecture focusing on developments in digital image correlation (DIC), the methods have continued to expand internationally and their use has begun to grow in fields where there was less activity in the past. First, a brief history of digital image correlation methods is presented from the perspective of the first author, followed by a discussion of recent trends associated with the use of digital image correlation methods in academics, governmental laboratories and industrial settings. In the remainder of the article, new results are provided in three areas where DIC methods have seen rapid growth; application of StereoDIC or three-dimensional DIC (3D-DIC) to the study of wall structures in civil engineering; the use of Volumetric DIC or Digital Volume Correlation (DVC) to quantify the internal response of a specially-designed composite material and in the area of model validation for another application in civil engineering; transfer length measurements in pre-stressed concrete beams.  相似文献   
130.
We have demonstrated an informatics methodology for finding correlations between the full profile Fourier transform infrared spectra of polycrystalline 3C‐silicon carbide (poly‐SiC) films and their growth conditions, thereby developing high‐throughput structure‐process relationships. Because SiC films are a structural element in photonic sensors, this paper focuses on the interpretation of their optical response, the multivariate tracking of critical processing pathways, and the identification of controlling processing mechanisms. Using principal component analysis, we have developed a data analysis tool to aid in the assessment of the relative contributions of experimental parameters in low‐pressure chemical vapor deposition processes to optical responses on the basis of the size of eigenvalues of the spectral data set. The applied methodology for identifying spectral relationships of stoichiometry, dopant chemistry, and microstructure of poly‐SiC provides more effective guidelines to manipulate optical responses by controlling multiple experimental parameters. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号