全文获取类型
收费全文 | 1454篇 |
免费 | 100篇 |
国内免费 | 12篇 |
专业分类
化学 | 1100篇 |
晶体学 | 10篇 |
力学 | 31篇 |
数学 | 154篇 |
物理学 | 271篇 |
出版年
2024年 | 2篇 |
2023年 | 4篇 |
2022年 | 14篇 |
2021年 | 51篇 |
2020年 | 34篇 |
2019年 | 31篇 |
2018年 | 24篇 |
2017年 | 29篇 |
2016年 | 59篇 |
2015年 | 54篇 |
2014年 | 91篇 |
2013年 | 109篇 |
2012年 | 141篇 |
2011年 | 126篇 |
2010年 | 94篇 |
2009年 | 79篇 |
2008年 | 86篇 |
2007年 | 83篇 |
2006年 | 77篇 |
2005年 | 63篇 |
2004年 | 57篇 |
2003年 | 48篇 |
2002年 | 40篇 |
2001年 | 32篇 |
2000年 | 24篇 |
1999年 | 16篇 |
1998年 | 13篇 |
1997年 | 9篇 |
1996年 | 17篇 |
1995年 | 9篇 |
1994年 | 7篇 |
1993年 | 5篇 |
1992年 | 4篇 |
1991年 | 5篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1988年 | 5篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1971年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有1566条查询结果,搜索用时 15 毫秒
991.
Yong?Nam?Kim Jong?Min?Kum Hyeok?Moo?Lee Sung?Oh?ChoEmail author 《Journal of nanoparticle research》2012,14(4):774
A novel approach to pattern nanocrystalline gold (Au) octahedra is presented based on electron irradiation combined with thermal
treatment and post-cleaning process using HAuCl4-loaded poly(styrene-b-2-vinyl pyridine) (PS-b-P2VP) block copolymer (BCP) as a precursor material. The BCP tends to cross-link
under electron irradiation, and thus a patterned film can be prepared by selectively irradiating an electron beam onto a precursor
film using a shadow mask. A post-thermal treatment leads to the formation of crystalline Au nano-octahedra inside the patterned
film with a help of the BCP acting as a capping agent. Subsequently, the BCP can be removed by O2 plasma etching combined with oxidative degradation, with the Au nanoparticles remaining. As a result, a patterned film consisting
of high-purity nanocrystalline Au octahedra is fabricated. The sizes of the Au octahedral nanoparticles can be readily controlled
from 49 to 101 nm by changing the thickness of the precursor film. The patterned Au nano-octahedra films exhibit excellent
surface-enhanced Raman scattering behavior with the maximum enhancement factor of ~106. 相似文献
992.
An all-optical scheme for simultaneously realizing OR and AND logic gates based on three-input four-wave mixing (FWM) arising in a single semiconductor optical amplifier (SOA) is proposed and demonstrated. It has the ability to process not only conventional non-return-to-zero-ON-OFF-keying (NRZ-OOK) and return-to-zero-OOK (RZ-OOK) formats but also carrier-suppressed return-to-zero-OOK (CSRZ-OOK) format signals. Firstly, the performance of 40 Gb/s logic operation is numerically evaluated by a comprehensive dynamic SOA model considering three input signal induced FWM effect. Then, 10 Gb/s experimental demonstrations with clear waveforms and high extinction ratios (ERs) further verify the logic integrity of this scheme. Thus, the OR and AND logic gates simultaneously achieved within a single logic unit is compact and cost-effective for future optical signal processing applications. 相似文献
993.
Isolation of strains degrading poly(Vinyl alcohol) at high temperatures and their biodegradation ability 总被引:2,自引:0,他引:2
Thermophilic strains were isolated for the first time using activated sludge retrieved from waste water treatment plant of a poly(vinyl alcohol) (PVA) producing factory for biodegradation of PVA at relatively high temperatures. The isolated strains were identified to be Geobacillus tepidamans, Brevibacillus brevis and Brevibacillus limnophilus. The former strain degraded PVA for itself, while the latter 2 strains digested PVA symbiotically. PVA degradation activity of the isolated strains was assessed at first by the halo zone size formed around the colonies and finally by the modified Sturm test. The biodegradation rate of PVA was explored also in the presence of different dyes, because most of the waste water from PVA-consuming factories contains waste dyes. 相似文献
994.
We investigated the delamination problem at the metal‐polymer interface and the mechanical buckling of the metal layer at a localized area of the metallic shell under compression between two parallel plates. First, polystyrene (PS) beads were synthesized by dispersion polymerization and then their sulfonation process. After sequential electroless deposition, the average size of multi‐metal coated sulfonated polystyrene (SPS) bead was ca 4.95 µm. Using the electromechanical indentation, the electrical resistance of a single metal‐coated SPS bead decreased with increasing compressive strain without delamination at the metal‐polymer interface, and its electrical resistance showed 5.65 Ω. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
995.
To understand the basic properties of ionic liquids (ILs), we examined the phase behavior and ionic conductivity characteristics using various compositions of different ionic liquids (1-ethyl-3-methylimidazolium hexafluorophosphate [emim] [PF6] and 1-benzyl-3-methylimidazolium hexafluorophosphate [bzmim] [PF6]) in several different alcohols (ethanol, propanol, 1-butanol, 2-butanol, and hexanol). We conducted a systematic study of the impact of different factors on the phase behavior of imidazolium-based ionic liquids in alcohols. Using a new experimental method with a liquid electrolyte system, we observed that the ionic conductivity of the ionic liquid/alcohol was sensitive to the surrounding temperature. We employed Chang et al.’s thermodynamic model [Chang et al. (1997, 1998) [21], [22]] based on the lattice model. The obtained co-ordinated unit parameter from this model was used to describe the phase behavior and ionic conductivities of the given system. Good agreement with experimental data of various alcohol and ILs systems was obtained in the range of interest. 相似文献
996.
In this study, we demonstrate that 2-microm-sized Ag (microAg) powders can be used as a core material for constructing molecular sensing/recognition units operating via surface-enhanced Raman scattering (SERS). This is possible because microAg powders are very efficient substrates for both the infrared and Raman-spectroscopic characterization of molecular adsorbates prepared in a similar manner on silver surfaces; we can obtain an infrared spectrum of organic molecules adsorbed on microAg particles with a very high signal-to-noise ratio by diffuse reflectance infrared Fourier transform spectroscopy (DRIFT), and the Raman spectrum of organic monolayers on powdered silver is an SERS spectrum. The agglomeration of microAg particles in a highly concentrated buffer solution could be prevented by the layer-by-layer deposition of cationic and anionic polyelectrolytes such as poly(allylamine hydrochloride) (PAH) and poly(acrylic acid) (PAA). In fact, prior to depositing PAA and PAH, 4-aminobenzenethiol (4-ABT) was assembled on the surfaces of the microAg particles as SERS markers. Because of the presence of amine groups of 4-ABT, PAA could be readily deposited on the microAg particles. On the other hand, the outermost PAA layer could also be derivatized with biotin-derivatized poly(L-lysine). The nonspecific interaction of poly(L-lysine) with proteins could be suppressed by grafting poly(ethylene glycol) into the biotin-derivatized poly(L-lysine) molecules. On the basis of the nature of the SERS peaks of 4-ABT, it was confirmed that these biotinylated microAg powders were effective in selectively recognizing the streptavidin arrays. Because a number of different molecules can be used as SERS-marker molecules, such as probable 4-ABT, commercially available microAg powders must be a prospective material in molecular sensing/recognition, particularly via SERS. 相似文献
997.
998.
999.
1000.
Barwick SW Beatty JJ Besson DZ Binns WR Cai B Clem JM Connolly A Cowen DF Dowkontt PF Duvernois MA Evenson PA Goldstein D Gorham PW Hebert CL Israel MH Learned JG Liewer KM Link JT Matsuno S Miocinović P Nam J Naudet CJ Nichol R Palladino K Rosen M Saltzberg D Seckel D Silvestri A Stokes BT Varner GS Wu F 《Physical review letters》2006,96(17):171101
We report new limits on cosmic neutrino fluxes from the test flight of the Antarctic Impulsive Transient Antenna (ANITA) experiment, which completed an 18.4 day flight of a prototype long-duration balloon payload, called ANITA-lite, in early 2004. We search for impulsive events that could be associated with ultrahigh energy neutrino interactions in the ice and derive limits that constrain several models for ultrahigh energy neutrino fluxes and rule out the long-standing -burst model. 相似文献