全文获取类型
收费全文 | 203篇 |
免费 | 2篇 |
专业分类
化学 | 99篇 |
晶体学 | 5篇 |
力学 | 5篇 |
数学 | 41篇 |
物理学 | 55篇 |
出版年
2021年 | 3篇 |
2018年 | 3篇 |
2017年 | 2篇 |
2016年 | 5篇 |
2015年 | 5篇 |
2014年 | 7篇 |
2013年 | 24篇 |
2012年 | 6篇 |
2011年 | 11篇 |
2010年 | 6篇 |
2008年 | 8篇 |
2007年 | 11篇 |
2006年 | 7篇 |
2005年 | 7篇 |
2004年 | 6篇 |
2003年 | 5篇 |
2002年 | 1篇 |
2001年 | 9篇 |
2000年 | 5篇 |
1999年 | 1篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1995年 | 4篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 4篇 |
1988年 | 6篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1983年 | 2篇 |
1981年 | 1篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1977年 | 2篇 |
1975年 | 3篇 |
1974年 | 4篇 |
1973年 | 2篇 |
1972年 | 4篇 |
1970年 | 1篇 |
1966年 | 1篇 |
1960年 | 1篇 |
1928年 | 1篇 |
1902年 | 1篇 |
1882年 | 1篇 |
排序方式: 共有205条查询结果,搜索用时 15 毫秒
61.
The morphology of the produced Ag nanoparticle is controlled successfully by UV irradiating the reaction solution of AgAc/ethyl alcohol/1-octadeconal/1-dodecanethiol. With use of a novel solution such as soft template, Ag nanorods with different sizes and different ratios of length to diameter can be obtained by adjusting the concentrations of the solution compositions. 相似文献
62.
Aubrey D. Calhoun Kaki R. Lung Terence A. Nile Leon L. Stokes Scott C. Smith 《Transition Metal Chemistry》1983,8(6):365-368
Summary The catalytic activity of rhodium complexes for the hydrosilylation of substrates such as alkenes, 1,3-dienes, 1-alkynes, or ketones, is enhanced by the addition of organic oxidizing agents, such ast-butyl hydroperoxide, hydrogen peroxide, orm-chloroperbenzoic acid. Similar enhancement is found for the Group VIA hexacarbonyls in the hydrosilylation of 1,3-dienes. 相似文献
63.
Accurate quantitation has been demonstrated on many different types of mass spectrometer. However, quantitative applications of Fourier transform ion cyclotron resonance mass spectrometry (FTICRMS) have been limited. In this study, the quantitative potential of FTICRMS has been investigated using an exact matching isotope dilution method for the determination of creatinine in serum. Creatinine is an important clinical biomarker and its measurement is used as an assessment of renal function. The quantitation of creatinine was selected because a high-accuracy high-performance liquid chromatography/mass spectrometry (HPLC/MS) determination using a triple quadrupole mass spectrometer has already been successfully developed in-house. Therefore, a direct comparison of the quantitative capability of FTICRMS could be made against an established method. The accuracy of the quantitation of creatinine was found to be equivalent to that obtained using LC/MS. However, the expanded measurement uncertainty (k = 2) was larger, at 6%, when using FTICRMS compared with 1% when using HPLC/MS with the triple quadrupole mass spectrometer. 相似文献
64.
This work demonstrates the detection of E. coli using a 2-dimensional photosensor array biochip which is efficiently equipped with a microfluidics sample/reagent delivery system for on-chip monitoring of bioassays. The biochip features a 4 x 4 array of independently operating photodiodes that are integrated along with amplifiers, discriminators and logic circuitry on a single platform. The microfluidics system includes a single 0.4 mL reaction chamber which houses a sampling platform that selectively captures detection probes from a sample through the use of immobilized bioreceptors. The independently operating photodiodes allow simultaneous monitoring of multiple samples. In this study the sampling platform is a cellulosic membrane that is exposed to E. coli organisms and subsequently analyzed using a sandwich immunoassay involving a Cy5-labeled antibody probe. The combined effectiveness of the integrated circuit (IC) biochip and the immunoassay is evaluated for assays performed both by conventional laboratory means followed by detection with the IC biochip, and through the use of the microfluidics system for on-chip detection. Highlights of the studies show that the biochip has a linear dynamic range of three orders of magnitude observed for conventional assays, and can detect 20 E. coli organisms. Selective detection of E. coli in a complex medium, milk diluent, is also reported for both off-chip and on-chip assays. 相似文献
65.
There is currently significant interest in all-ceramic dental restorations due to the demand to replace metals as the primary load-bearing tooth restorative material. A promising non-metallic material for such restorations is fluorcanasite, a chain-silicate glass-ceramic that is castable using conventional dental metal-casting techniques and which exhibits enhanced fracture toughness and flexural strength compared with currently available resin-bonded ceramics. Unfortunately, because of its relatively low silica content, it exhibits poor chemical durability. The aim of this study was to assess the influence of compositional changes on the formation and chemical solubility of the fluorcanasite forming glass, crystalline phase and residual glass. To this end, mixed-alkali compositions have been investigated and it has been shown that the solubility of the glass is a function of the alkali species present in the glass. By changing the alkali ratio of the fluorcanasite forming glass from 0.33 ([K]/[K + Na]) of the base composition derived from stoichiometry to 0.47, it was possible to reduce the chemical solubility of the fluorcanasite material significantly. The addition of extra CaF2 to refine the grain structure resulted in a decrease in the durability of the material, making it currently unacceptable for dental applications. The glass-ceramic exhibits a minimum chemical solubility at the composition K7/Na8. The residual glass may have a slightly elevated K content compared to the original glass. The addition of extra CaF2 to refine the grain structure resulted in an unacceptable decrease in the durability of the material. 相似文献
66.
G. M. Chechin O. A. Lavrova V. P. Sakhnenko H. T. Stokes D. M. Hatch 《Physics of the Solid State》2002,44(3):581-584
A new type of nonlinear (anharmonic) excitations—bushes of vibrational modes—in physical systems with point or space symmetry is discussed. All infrared-active and Raman-active bushes for C60 fullerene are found by means of special group-theoretical methods. 相似文献
67.
Abbasi RU Abu-Zayyad T Amann JF Archbold G Bellido JA Belov K Belz JW Bergman DR Cao Z Clay RW Cooper MD Dai H Dawson BR Everett AA Fedorova YA Girard JH Gray RC Hanlon WF Hoffman CM Holzscheiter MH Hüntemeyer P Jones BF Jui CC Kieda DB Kim K Kirn MA Loh EC Manago N Marek LJ Martens K Martin G Matthews JA Matthews JN Meyer JR Moore SA Morrison P Moosman AN Mumford JR Munro MW Painter CA Perera L Reil K Riehle R Roberts M Sarracino JS Sasaki M Schnetzer SR Shen P Simpson KM Sinnis G Smith JD 《Physical review letters》2004,92(15):151101
We have measured the cosmic ray spectrum above 10(17.2) eV using the two air-fluorescence detectors of the High Resolution Fly's Eye observatory operating in monocular mode. We describe the detector, phototube, and atmospheric calibrations, as well as the analysis techniques for the two detectors. We fit the spectrum to a model consisting of galactic and extragalactic sources. 相似文献
68.
Trinkle DR Hennig RG Srinivasan SG Hatch DM Jones MD Stokes HT Albers RC Wilkins JW 《Physical review letters》2003,91(2):025701
We propose a new direct mechanism for the pressure driven alpha-->omega martensitic transformation in pure titanium. A systematic algorithm enumerates all possible pathways whose energy barriers are evaluated. A new, homogeneous pathway emerges with a barrier at least 4 times lower than other pathways. The pathway is shown to be favorable in any nucleation model. 相似文献
69.
Apparent molar volumes of urea are measured over a temperature range in water, methanol, ethanol, formamide, DMF and DMSO. The limiting apparent molar volumes show a large variation in different solvents. In marked contrast to the situation in water, the temperature dependence of the limiting apparent molar volumes in the nonaqueous solvents is slight. The concentration dependence is discussed qualitatively in terms of solute association.Now Diane Beaumont. 相似文献
70.
Vijay K. Stokes 《Journal of sound and vibration》1974,35(1):77-99
An analytical and experimental programme was conducted to investigate the dynamic radial expansion of helical springs due to longitudinal impact.The basic equations of motion were normalized in such a way that terms of the same order could be retained in a systematic manner. A minimum complexity model was then developed by making suitable approximations in the resulting simplified equations of motion. Finally, an expression for the dynamic radial expansion was obtained, and it was shown to be the result of a two-wave interaction.Impact tests were made on a specially designed spring and the resulting motions recorded by using a high speed motion picture camera. The experimental results support the predictions of the theory. 相似文献