全文获取类型
收费全文 | 698篇 |
免费 | 59篇 |
国内免费 | 1篇 |
专业分类
化学 | 637篇 |
晶体学 | 3篇 |
力学 | 4篇 |
数学 | 50篇 |
物理学 | 64篇 |
出版年
2023年 | 12篇 |
2022年 | 12篇 |
2021年 | 14篇 |
2020年 | 24篇 |
2019年 | 22篇 |
2018年 | 8篇 |
2017年 | 12篇 |
2016年 | 26篇 |
2015年 | 34篇 |
2014年 | 36篇 |
2013年 | 38篇 |
2012年 | 51篇 |
2011年 | 72篇 |
2010年 | 46篇 |
2009年 | 34篇 |
2008年 | 62篇 |
2007年 | 56篇 |
2006年 | 36篇 |
2005年 | 23篇 |
2004年 | 34篇 |
2003年 | 22篇 |
2002年 | 31篇 |
2001年 | 8篇 |
2000年 | 11篇 |
1999年 | 4篇 |
1998年 | 7篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1995年 | 3篇 |
1993年 | 2篇 |
1988年 | 1篇 |
1985年 | 2篇 |
1982年 | 2篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1925年 | 1篇 |
排序方式: 共有758条查询结果,搜索用时 31 毫秒
691.
Joye CD Griffin RG Hornstein MK Hu KN Kreischer KE Rosay M Shapiro MA Sirigiri JR Temkin RJ Woskov PP 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》2006,34(3):518-523
The operating characteristics of a 140-GHz 14-W long pulse gyrotron are presented. The device is being used in dynamic nuclear polarization enhanced nuclear magnetic resonance (DNP/NMR) spectroscopy experiments. The gyrotron yields 14 W peak power at 139.65 GHz from the TE(0,3) operating mode using a 12.3-kV 25-mA electron beam. Additionally, up to 12 W peak has been observed in the TE(2,3) mode at 136.90 GHz. A series of mode converters transform the TE(0,3) operating mode to the TE(1,1) mode. Experimental results are compared with nonlinear simulations and show reasonable agreement. The millimeter-wave output beam was imaged in a single shot using a pyroelectric camera. The mode patterns matched reasonably well to theory for both the TE(0,1) mode and the TE(1,1) mode. Repeatable mode patterns were obtained at intervals ranging from 0.8 s apart to 11 min apart at the output of the final mode converter. 相似文献
692.
693.
694.
695.
Ménard L Polak M Denny M Burton E Lane H Matthies ML Marrone N Perkell JS Tiede M Vick J 《The Journal of the Acoustical Society of America》2007,121(6):3790-3801
This study investigates the effects of speaking condition and auditory feedback on vowel production by postlingually deafened adults. Thirteen cochlear implant users produced repetitions of nine American English vowels prior to implantation, and at one month and one year after implantation. There were three speaking conditions (clear, normal, and fast), and two feedback conditions after implantation (implant processor turned on and off). Ten normal-hearing controls were also recorded once. Vowel contrasts in the formant space (expressed in mels) were larger in the clear than in the fast condition, both for controls and for implant users at all three time samples. Implant users also produced differences in duration between clear and fast conditions that were in the range of those obtained from the controls. In agreement with prior work, the implant users had contrast values lower than did the controls. The implant users' contrasts were larger with hearing on than off and improved from one month to one year postimplant. Because the controls and implant users responded similarly to a change in speaking condition, it is inferred that auditory feedback, although demonstrably important for maintaining normative values of vowel contrasts, is not needed to maintain the distinctiveness of those contrasts in different speaking conditions. 相似文献
696.
Pojman JA Viner V Binici B Lavergne S Winsper M Golovaty D Gross L 《Chaos (Woodbury, N.Y.)》2007,17(3):033125
We demonstrate that Snell's law of refraction can be applied to thermal fronts propagating through a boundary between regions that support distinct frontal velocities. We use the free-radical frontal polymerization of a triacrylate with clay filler that allows for two domains containing two different concentrations of a peroxide initiator to be molded together. Because the polymerization reaction rates depend on the initiator concentration, the propagation speed is different in each domain. We study fronts propagating in two parallel strips in which the incident angle is 90 degrees. Our data fit Snell's law v(r)/v(i)=sin theta(r)/sin theta(i), where v(r) is the refracted velocity, v(i) is the incident velocity, theta(r) is the angle of refraction, and theta(i) is the incident angle. Further, we study circular fronts propagating radially from an initiation point in a high-velocity region into a low-velocity region (and vice versa). We demonstrate the close resemblance between the numerically simulated and experimentally observed thermal reaction fronts. By measuring the normal velocity and the angle of refraction of both simulated and experimental fronts, we establish that Snell's law holds for thermal frontal polymerization in our experimental system. Finally we discuss the regimes in which Snell's law may not be valid. 相似文献
697.
WNKs (with-no-lysine [K]) are a family of serine-threonine protein kinases with an atypical placement of the catalytic lysine relative to all other protein kinases. The roles of WNK kinases in regulating ion transport were first revealed by the findings that mutations of two members cause a genetic hypertension and hyperkalemia syndrome. More recent studies suggest that WNKs are pleiotropic protein kinases with important roles in many cell processes in addition to ion transport. Here, we review roles of WNK kinases in the regulation of ion balance, cell signaling, survival, and proliferation, and embryonic organ development. 相似文献
698.
Hao G Yang L Mazsaroff I Lin M 《Journal of the American Society for Mass Spectrometry》2007,18(9):1579-1581
We developed a novel in vitro lipase assay based on the quantitation of fatty acids by liquid chromatography-mass spectrometry. Oleic acids enzymatically released from triolein substrates were isolated from the reaction mixture by reverse-phase chromatography, ionized in negative mode electrospray mass spectrometry and quantitated with the aid of [(13)C]-oleic acid internal standard. The enzymatic activity was measured by monitoring oleic acid productions at multiple time points. This method overcomes the substrate and pH limitations of conventional techniques and thus serves as a generic lipase activity assay. 相似文献
699.
700.
Foster SR Pearce A Blake AJ Welham MJ Dowden J 《Chemical communications (Cambridge, England)》2007,(24):2512-2514
A novel octavalent, resorcin[4]arene derived, cross-linker designed to overcome some of the limitations of commercially available reagents is significantly more efficient for covalent stabilisation of protein-protein interactions. 相似文献