全文获取类型
收费全文 | 3222篇 |
免费 | 948篇 |
国内免费 | 362篇 |
专业分类
化学 | 2230篇 |
晶体学 | 237篇 |
力学 | 96篇 |
综合类 | 41篇 |
数学 | 8篇 |
物理学 | 1920篇 |
出版年
2024年 | 10篇 |
2023年 | 22篇 |
2022年 | 71篇 |
2021年 | 89篇 |
2020年 | 94篇 |
2019年 | 92篇 |
2018年 | 70篇 |
2017年 | 126篇 |
2016年 | 196篇 |
2015年 | 191篇 |
2014年 | 228篇 |
2013年 | 376篇 |
2012年 | 261篇 |
2011年 | 261篇 |
2010年 | 210篇 |
2009年 | 192篇 |
2008年 | 186篇 |
2007年 | 216篇 |
2006年 | 200篇 |
2005年 | 180篇 |
2004年 | 166篇 |
2003年 | 161篇 |
2002年 | 172篇 |
2001年 | 76篇 |
2000年 | 83篇 |
1999年 | 69篇 |
1998年 | 99篇 |
1997年 | 93篇 |
1996年 | 69篇 |
1995年 | 75篇 |
1994年 | 42篇 |
1993年 | 33篇 |
1992年 | 18篇 |
1991年 | 14篇 |
1990年 | 20篇 |
1989年 | 11篇 |
1988年 | 14篇 |
1987年 | 5篇 |
1986年 | 5篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1983年 | 5篇 |
1982年 | 8篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1975年 | 2篇 |
1974年 | 3篇 |
1973年 | 3篇 |
1972年 | 2篇 |
排序方式: 共有4532条查询结果,搜索用时 15 毫秒
71.
Manoj K. Kolel‐Veetil Kenan P. Fears Syed B. Qadri Christopher A. Klug Teddy M. Keller 《Journal of polymer science. Part A, Polymer chemistry》2012,50(15):3158-3170
A semicrystalline inorganic–organic hybrid crosslinked network containing polyhedral oligomeric silsesquioxane (POSS) cores was constructed by the unusual hydrosilylation of the terminal vinyl groups of an internal acetylene‐containing silane linker by a POSS monomer. Products from the thermal treatments of this network in either argon or air at 250, 550, and 1000 °C, respectively, were characterized by Fourier transform infrared, Solid‐state 13C and 29Si magic angle spinning NMR, X‐ray diffraction and XPS analyses. The highly symmetrically functionalized POSS silica clusters, in the fluorite silica phase, in the network were found to remain unchanged on thermal treatment possibly due to the shielding of the silica core by the functionalities and a cancellation of thermal stresses on the silica core. Stabilization of the metastable α‐cristobalite phase, which is typically formed on cooling by a β‐ to α‐transition of the β‐cristobalite phase formed above 1400 °C, was observed in the amorphous regions in the network sample treated only to 1000 °C in air. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
72.
This paper studies the fabrication and characterization of 80 nm zinc oxide anti-reflective coating (ARC) on flexible 1.3 μm thin film microcrystalline silicon (μc-Si) solar cell. High resolution X-ray diffraction (HR-XRD) shows a c-axis oriented ZnO (0 0 2) peak (hexagonal crystal structure) at 34.3° with full width at half maximum (FWHM) of 0.3936°. Atomic force microscope (AFM) measures high surface roughness root-mean-square (RMS) of the layer (50.76 nm) which suggests scattering of the incident light at the front surface of the solar cell. UV–vis spectrophotometer illustrates that ZnO ARC has optical transmittance of more than 80% in the visible and infra-red (IR) regions and corresponds to band gap (Eg) of 3.3 eV as derived from Tauc equation. Inclusion of ZnO ARC successfully suppresses surface reflectance from the cell to 2% (at 600 nm) due to refractive index grading between the Si and the ZnO besides quarter-wavelength (λ/4) destructive interference effect. The reduced reflectance and effective scattering effect of the incident light at the front side of the cell are believed to be the reasons why short-circuit current (Isc) and efficiency (η) of the cell improve. 相似文献
73.
Aleksandr I. Chumakov Ilya Sergeev Jean‐Philippe Celse Rudolf Rüffer Marc Lesourd Lin Zhang Manuel Sánchez del Río 《Journal of synchrotron radiation》2014,21(2):315-324
The performance of a cryogenically cooled double‐crystal silicon monochromator was studied under high‐heat‐load conditions with total absorbed powers and power densities ranging from 8 to 780 W and from 8 to 240 W mm?2, respectively. When the temperature of the first crystal is maintained close to the temperature of zero thermal expansion of silicon, the monochromator shows nearly ideal performance with a thermal slope error of 0.6 µrad. By tuning the size of the first slit, the regime of the ideal performance can be maintained over a wide range of heat loads, i.e. from power densities of 110 W mm?2 (at total absorbed power of 510 W) to 240 W mm?2 (at total absorbed power of 240 W). 相似文献
74.
75.
Valerie Lefevre Jean-Louis Ripoll 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1):371-372
The retro-ene reaction of allylthio- and propargylthiosilanes led, under flash vacuum thermolysis (FVT) conditions, to unhindered silanethiones, characterized by their derivatives, and also directly by coupling of the FVT with gas-phase spectrometries. Monomeric silicon oxysulfide has been generated similarly. The unsubstituted silanethione was not obtained, but dehydrogenated into silicon monosulfide during FVT. 相似文献
76.
Studies on the Silylation Reaction of α,β-Epoxy Esters Synthesized by Darzen's Condensation Reaction
《Phosphorus, sulfur, and silicon and the related elements》2013,188(12):2545-2550
Me3SiCl/Mg in HMPA was used for silylation of α,β-epoxy esters resulting in the corresponding β-silylated esters in a one pot reaction with reasonable yields. 相似文献
77.
Abstract A model for calculation of the range distribution of energetic ions with taking into account the channeling effect is proposed. The measurement of the depth distributions of boron ions in silicon crystals implanted at 13.6 and 91 MeV revealed significant difference between the measured and the calculated range profiles when the channeling effects have not been included in the calculation. In spite of deminishing the critical angles of channeling with growing ion energy the probability of the capture of ions into the channeling regime is significant in case of high energy implantation even when the incident angles are 7–10° off the main crystallographic directions. 相似文献
78.
《Current Applied Physics》2014,14(9):1240-1244
A cylindrical Si3N4 nanopattern whose heights was 200 nm was fabricated on a glass substrate, and an aluminum-doped zinc oxide (AZO) layer was grown on the nanopatterned glass substrate. The nanopattern was applied to an amorphous silicon solar cell in order to increase the light-scattering effect, thus enhancing the efficiency of the solar cell. The reflectance of the solar cell on the Si3N4 nanopattern decreased and its absorption increased. Compared to a flat substrate, the short-circuit current density (Jsc) and conversion efficiency of a solar cell on the Si3N4 nanopatterned substrate were improved by 17.9% and 24.2%, respectively, as determined from solar simulator measurements. 相似文献
79.
A. F. Isakovic A. Stein J. B. Warren S. Narayanan M. Sprung A. R. Sandy K. Evans‐Lutterodt 《Journal of synchrotron radiation》2009,16(1):8-13
Motivated by the anticipated advantageous performance of diamond kinoform refractive lenses for synchrotron X‐ray radiation studies, this report focuses on progress in designing, nanofabricating and testing of their focusing performance. The method involves using lift‐off and plasma etching to reproduce a planar definition of numerically determined kinoform refractive optics. Tests of the focusing action of a diamond kinoform refractive lens at the APS 8‐ID‐I beamline demonstrate angular control of the focal spot. 相似文献
80.
Michael Mehring Christian LÖW Ioannis Vrasidas Markus SchÜRmann Klaus Jurkschat 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1):311-318
Recent results are reported on the application of the novel O,C,O-coordinating pincer ligand {2,6-[P(O)(OEt)2]2-4-tert-Bu-C6H2} (A) for the synthesis of hypercoordinate organotin(IV) compounds ASnR3 (R = Ph, Cl), heteroleptic stannylenes ASnR (R = Cl, CH2SiMe3) and intramolecularly coordinated 1,2,5-oxaphosphastannolanes. 相似文献