全文获取类型
收费全文 | 1271篇 |
免费 | 21篇 |
国内免费 | 8篇 |
专业分类
化学 | 846篇 |
晶体学 | 19篇 |
力学 | 26篇 |
数学 | 85篇 |
物理学 | 324篇 |
出版年
2021年 | 9篇 |
2020年 | 8篇 |
2019年 | 26篇 |
2018年 | 11篇 |
2017年 | 9篇 |
2016年 | 22篇 |
2015年 | 14篇 |
2014年 | 12篇 |
2013年 | 60篇 |
2012年 | 55篇 |
2011年 | 65篇 |
2010年 | 31篇 |
2009年 | 23篇 |
2008年 | 73篇 |
2007年 | 68篇 |
2006年 | 94篇 |
2005年 | 61篇 |
2004年 | 45篇 |
2003年 | 33篇 |
2002年 | 50篇 |
2001年 | 40篇 |
2000年 | 29篇 |
1999年 | 18篇 |
1997年 | 15篇 |
1996年 | 19篇 |
1995年 | 19篇 |
1994年 | 14篇 |
1993年 | 18篇 |
1992年 | 25篇 |
1991年 | 18篇 |
1990年 | 12篇 |
1989年 | 9篇 |
1988年 | 15篇 |
1987年 | 13篇 |
1986年 | 10篇 |
1985年 | 22篇 |
1984年 | 17篇 |
1983年 | 12篇 |
1982年 | 17篇 |
1981年 | 11篇 |
1980年 | 12篇 |
1979年 | 9篇 |
1978年 | 16篇 |
1976年 | 13篇 |
1975年 | 13篇 |
1974年 | 17篇 |
1973年 | 20篇 |
1972年 | 6篇 |
1971年 | 7篇 |
1935年 | 6篇 |
排序方式: 共有1300条查询结果,搜索用时 265 毫秒
111.
M. P. Dancy J. Billowes I. S. Grant D. E. Evans J. A. R. Griffith S. A. Wells D. A. Eastham J. Groves J. R. H. Smith D. W. L. Tolfree P. M. Walker 《Hyperfine Interactions》1990,59(1-4):193-196
East particle-photon coincidence techniques, developed at Daresbury with strontium isotopes, allow ultrasensitive laser fluorescence
spectroscopy of beams of radio-active isotopes which can only be produced in very low yields. The technique has now been applied
to neutron-deficient barium isotopes down to120Ba. From measured hyperfine splittings and isotope shifts, nuclear moments and changes in mean square radii have been determined.
The work has revealed an abrupt increase in the mean square radius for121Ba large enough to disrupt the systematic staggering of nuclear size seen for the series. In a recent experiment an isomeric
state of127Ba with a half-life of about 2 seconds has been produced in a very low yield; nevertheless we have succeeded in obtaining
a fluorescence spectrum. 相似文献
112.
B. K. Mukhopadhyay K. K. Ahlquist V. Gruenman A. Lutz I. I. Kovalevski B. Schulze E. Rieger A. Noll W. Nagel J. Grant A. Abrams P. W. Codwise W. Staedel und J. D. Piper 《Fresenius' Journal of Analytical Chemistry》1936,105(5-6):212-222
Ohne Zusammenfassung 相似文献
113.
R. Mark Nicoll Sally A. Hindle Grant MacKenzie Ian H. Hillier Neil A. Burton 《Theoretical chemistry accounts》2001,106(1-2):105-112
114.
115.
116.
T. L. Shaw V. R. Green C. J. Ashworth J. Rikovska N. J. Stone P. M. Walker I. S. Grant 《Hyperfine Interactions》1987,35(1-4):821-824
The hyperfine field of CsFe has been measured to be (+)40.8(0.7)T, using the technique of on-line low temperature nuclear orientation. The time dependent
relaxation of121Csm
Fe has also been investigated using a new technique, giving a Korringa constant Ck of 0.059 (15) sK. From this, an effective relaxation time of 3.0 (0.8)s can be deduced for the short lived118Csm(T1/2=17s). This value has then been used to extract the magnetic moment of118Csm to be |μ|=5.4 (1.1) nm. 相似文献
117.
Magnetic field-controlled microfluidic transport. 总被引:1,自引:0,他引:1
Kyle M Grant Jared W Hemmert Henry S White 《Journal of the American Chemical Society》2002,124(3):462-467
Several new forms of magnetohydrodynamic (MHD) flow occurring in the solution gap between two 250-microm-diameter Pt microdisk electrodes, oriented in a face-to-face geometry and immersed in a uniform magnetic field (1 T), are described. The MHD flow results from the Lorentz force generated by diffusion of electrochemically generated molecular ions through the magnetic field. Individual microscopic flow tubes ( approximately 50-microm radius) spanning the gap between the face-to-face electrodes are observed during the 1-e(-) reduction of nitrobenzene in acetonitrile solutions. The flow tubes extend up to approximately 2 cm in length and are stable for indefinite periods. Directional transport of the electrogenerated nitrobenzene radical anion over macroscopic distances within the flow tubes, with minimal diffusional broadening, is demonstrated using an ultramicroelectrode probe to map the convective flux of redox species. Pulsed MHD transport of small packets of molecules and the formation of large area (approximately 3 cm(2)), microscopically thin (25 microm) rotating sheets of solution are also demonstrated. The results suggest that electrochemical methods, in combination with magnetohydrodynamic principles, may be useful for external field-controlled microfluidic systems. 相似文献
118.
Schoolyard Shade and Sun Exposure: Assessment of Personal Monitoring During Children's Physical Activity 下载免费PDF全文
Jennifer K. Vanos Grant R. McKercher Kylie Naughton Marc Lochbaum 《Photochemistry and photobiology》2017,93(4):1123-1132
Childhood exposure to ultraviolet radiation (UVR) is a major risk factor for the development of melanoma later in life. However, it is challenging to accurately determine personal outdoor exposure to UVR, specifically erythemally weighted UVR (UVEry), due to technological constraints, variable time–activity patterns, and the influence of outdoor environmental design. To address this challenge, this study utilized mobile and stationary techniques to examine the UVEry exposures of 14 children in a schoolyard in Lubbock, TX, in spring 2016. The aims of the study were to examine the influence of artificial shade on personal UVEry exposures and to assess full sun exposure ratios (ERs) within the same playground microenvironment. On average, personal wrist dosimeters worn during play in the sun measured 18% of the total onsite UVEry measured by a stationary UV pyranometer. Shade was found to significantly reduce the personal UVEry exposures by 55%, UVB280–315 nm exposures by 91%, and the overall solar radiation by 84%. Substantial benefits can be garnered through focused design of children's recreational space to utilize shade—both natural and artificial—to reduce UVR exposures during play, and to extend safe outdoor stays. Finally, although the wrist is a practical location for a dosimeter, it often underestimates full exposures, particularly during physical activity. 相似文献
119.
This report describes the use of Pd(II)/bis-sulfoxide 1 catalyzed intra- and intermolecular allylic C-H amination reactions to rapidly diversify structures containing a sensitive β-lactam core similar to that found in the monobactam antibiotic Aztreonam. Pharmacologically interesting oxazolidinone, oxazinanone, and linear amine motifs are rapidly installed with predictable and high selectivities under conditions that use limiting amounts of substrate. Additionally, we demonstrate for the first time that intramolecular C-H amination processes may be accelerated using catalytic amounts of a Lewis acid co-catalyst [Cr(III)(salen)Cl 2]. 相似文献
120.
The complex [Pt(9S3)(SbPh3)(Ph)](PF6) forms directly from [Pt(9S3)(SbPh3)2](PF6)2 during the room temperature crystallization of the latter in nitromethane. The crystal structure shows a five-coordinate Pt(II) center containing the tridentate thiacrown ligand, a Sb donor from the triphenylstibine ligand, and a σ-coordinating phenyl group. The phenyl group forms via Sb-C bond cleavage from one of the SbPh3 ligands in the bis complex. 相似文献