全文获取类型
收费全文 | 7854篇 |
免费 | 806篇 |
国内免费 | 524篇 |
专业分类
化学 | 5557篇 |
晶体学 | 96篇 |
力学 | 409篇 |
综合类 | 46篇 |
数学 | 691篇 |
物理学 | 2385篇 |
出版年
2024年 | 8篇 |
2023年 | 109篇 |
2022年 | 215篇 |
2021年 | 286篇 |
2020年 | 271篇 |
2019年 | 265篇 |
2018年 | 192篇 |
2017年 | 208篇 |
2016年 | 309篇 |
2015年 | 279篇 |
2014年 | 361篇 |
2013年 | 553篇 |
2012年 | 700篇 |
2011年 | 696篇 |
2010年 | 491篇 |
2009年 | 432篇 |
2008年 | 544篇 |
2007年 | 459篇 |
2006年 | 433篇 |
2005年 | 370篇 |
2004年 | 319篇 |
2003年 | 263篇 |
2002年 | 260篇 |
2001年 | 166篇 |
2000年 | 126篇 |
1999年 | 121篇 |
1998年 | 102篇 |
1997年 | 83篇 |
1996年 | 85篇 |
1995年 | 74篇 |
1994年 | 48篇 |
1993年 | 54篇 |
1992年 | 50篇 |
1991年 | 53篇 |
1990年 | 27篇 |
1989年 | 24篇 |
1988年 | 23篇 |
1987年 | 20篇 |
1986年 | 15篇 |
1985年 | 16篇 |
1984年 | 13篇 |
1983年 | 10篇 |
1982年 | 11篇 |
1981年 | 5篇 |
1980年 | 5篇 |
1979年 | 3篇 |
1977年 | 3篇 |
1973年 | 4篇 |
1971年 | 6篇 |
1970年 | 6篇 |
排序方式: 共有9184条查询结果,搜索用时 15 毫秒
991.
992.
We have undertaken a study of the microwave-assisted synthesis of (η6-arene)tricarbonylchromium complexes. Under microwave irradiation, the reactions of hexacarbonylchromium with arenes gave high yields of (η6-arene)chromium tricarbonyl complexes. 相似文献
993.
Sang Kyu Lee Byung‐Jun Jung Taek Ahn Young Kwan Jung Jeong‐Ik Lee In‐Nam Kang Jonghee Lee Jong‐Hwa Park Hong Ku Shim 《Journal of polymer science. Part A, Polymer chemistry》2007,45(15):3380-3390
A series of fluorene‐based copolymers composed of blue‐ and orange‐light‐emitting comonomers were synthesized through palladium‐catalyzed Suzuki coupling reactions. 9,9‐Dihexylfluorene and 2‐(2,6‐bis‐{2‐[1‐(9,9‐dihexyl‐9H‐fluoren‐2‐yl)‐1,2,3,4‐tetrahydroquinolin‐6‐yl]‐vinyl}‐pyran‐4‐ylidene)‐malononitrile (DCMF) were used as the blue‐ and orange‐light‐emitting chromophores, respectively. The resulting single polymers exhibited simultaneous blue (423/450 nm) and orange (580–600 nm) emissions from these two chromophores. By adjusting the fluorene and DCMF contents, white light emission could be obtained from a single polymer; a device with an ITO/PEDOT:PSS/polymer/Ca/Al configuration was found to exhibit pure white electroluminescence with Commission Internationale de L'Eclairage (CIE) coordinates of (0.33, 0.31), a maximum brightness of 1180 cd/m2, and a current efficiency of 0.60 cd/A. Furthermore, the white light emission of this device was found to be very stable with respect to variation of the driving voltage. The CIE coordinates of the device were (0.32, 0.29), (0.32, 0.29), and (0.33, 0.31) for driving voltages of 7, 8, and 10 V, respectively. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3380–3390, 2007 相似文献
994.
H.S. Kang Y.C. Kang H.D. Park Y.G. Shul 《Applied Physics A: Materials Science & Processing》2005,80(2):347-351
Green-emitting Y2SiO5:Tb phosphor particles with fine size, spherical shape, filled morphology, high crystallinity, and good brightness were synthesized by a spray pyrolysis process. The effect of silicon precursor type on the morphology, crystal structure, crystallinity, and photoluminescence efficiency of Y2SiO5:Tb phosphor particles was investigated. The particles prepared from an artificial colloidal solution obtained by dispersing fumed silica particles had a pure monoclinic X2 crystalline phase, which is more appropriate for application to displays, after post-treatment at 1300 °C. On the other hand, the particles prepared from 100% tetraethyl orthosilicate (TEOS) reagent had an X2 phase and small amounts of X1 and impurity phases such as Y2Si2O7 and Y4.67Si3O13 due to the phase-segregation characteristics of the TEOS precursor. The photoluminescence characteristics of Y2SiO5:Tb phosphor particles were strongly affected by the silicon source used. The photoluminescence intensities increased with the fumed silica/TEOS ratio. The particles prepared from 100% fumed silica showed the maximum photoluminescence intensity, which is 22% higher than that of particles prepared from 100% TEOS. PACS 81.20.Rg; 78.55.Hx; 78.40.Ha; 81.05.Hd; 81.40.Tv 相似文献
995.
On this paper, we investigate the algorithm and efficiency of simulation of optical devices using parallel computing method, implement some real wavelength division multiplexing (WDM) components such as resonators to test the method's possibility and efficiency. 相似文献
996.
用532.0 nm激光激发Na2分子到B1Πu电子态,记录了Na(3P)原子的跃迁和Na2分子的A1Σ+u-Χ1Σ+g的谱带.由Na与Na2激发态发射的光谱及其强度可以认定在Na-Na2系统中的碰撞过程,Na(3P)原子线是Na2(B1Πu)到Na(3P)的碰撞能量转移产生的,预解离过程也可产生原子线.而A1Σ+u-Χ1Σ+g谱带是由B1Πu到21Σ+g的碰撞转移后再由21Σ+g到A1Σ+u的辐射而引起的.在360℃,根据辐射衰变率和荧光强度,得到Na2(B1Πu)到Na2(21Σ+g)碰撞转移率系数为7.1×10-10 cm3s-1,而B1Πu的预解离率为2.3×106 s-1. 相似文献
997.
激光激发Cs He碰撞复合物,测量了Cs(62P)精细结构布居数分支比,由此证实了发生在光学碰撞中的非绝热跃迁.激光频率从Cs(6P3/2)红翼30cm-1调至蓝翼30cm-1,在6P3/2的近翼,分支比与矢谐量有很大的关系.同时测量了Cs(6PJ)态的精细结构转移截面,截面值σ21=9.8×10-19cm2. 相似文献
998.
S. Hofmann M. Cantoro M. Kaempgen D.-J. Kang V.B. Golovko H.W. Li Z. Yang J. Geng W.T.S. Huck B.F.G. Johnson S. Roth J. Robertson 《Applied Physics A: Materials Science & Processing》2005,81(8):1559-1567
We present three different catalyst preparation and patterning techniques for plasma-enhanced chemical vapor deposition of
carbon nanostructures from acetylene and ammonia mixtures. The different merits and potential areas of application are highlighted
for each technique as compared to the benchmark of e-beam-lithography patterning. Maskless, focused ion beam written Pt can
nucleate aligned carbon nanofibers, thereby allowing a sub-100 nm lateral resolution on non-planar substrate geometries combined
with an in-situ monitoring. Ion beam milling additionally enables the pre-shaping and marking of the substrate, which is shown
for the growth of individual nanofibers on the apex of commercial scanning probe tips. Pulsed electrochemical deposition was
used to form Ni and Fe catalyst islands of controlled size and density. This is also demonstrated on complex substrate geometries
such as carbon cloth. Nanocontact printing was employed to deposit a highly purified Co colloid in regular patterns with feature
sizes down to 100 nm onto silicon wafers for low cost patterning over large areas. We analyze the catalyst restructuring upon
exposure to elevated temperatures for each technique and relate this to the nucleated nanofiber dimensions and array densities.
The flexibility in catalyst and substrate material allows a transfer of our achievements to catalyst-assisted growth of nanostructures
in general facilitating their hierarchical device integration and future application.
PACS 81.16.Rf; 81.16.Hc; 61.46.+w 相似文献
999.
体声波滤波器由于其低插损、小尺寸、高带外抑制等特性,随着第三代移动通信以及蓝牙技术的发展而得到广泛研究,而MEMS技术和压电薄膜制备技术的进一步发展使高性能的体声波滤波器制作成为可能.我们以单晶MgO作为器件衬底,MgO/NbN多层结构作为AIN薄膜体声波器件的反射器,NBN/AIN/NbN三层结构为谐振器.在这样的多层结构的设计中由于各种材料之间的晶格失配小,可以获得从几十纳米到几百纳米厚度不等的单晶AIN薄膜.通过控制AIN薄膜和NbN薄膜的不同厚度,可以获得不同频段范围的谐振器.压电薄膜的质量,以及体声波在多层结构界面上的能量损耗,直接影响到谐振器电学性能.基于AIN材料的压电性能,设计了NBN/AIN/NBN三层结构的谐振器,并进行了数值模拟. 相似文献
1000.
Sang Chil Lee Jeong Woo Kang Hyung Soo Ahn Min Yang Nam Lyong Kang Suck Whan Kim 《Physica E: Low-dimensional Systems and Nanostructures》2005,28(4):402-411
Optical detected electrophonon resonance (ODEPR) effects in quantum wells of n-GaAs materials are investigated for square potential and parabolic potential, respectively. We also obtain the ODEPR conditions as functions of confinement frequency in parabolic potential and well-width in square potential for the various photon frequencies, respectively. In particular, anomalous behaviors of the ODEPR lineshape such as the splitting of ODEPR peaks for incident photon frequency are discussed. Furthermore, we obtain the selection rules for transition in quantum wells of two different potentials, respectively. 相似文献