全文获取类型
收费全文 | 10112篇 |
免费 | 405篇 |
国内免费 | 61篇 |
专业分类
化学 | 7034篇 |
晶体学 | 97篇 |
力学 | 290篇 |
数学 | 842篇 |
物理学 | 2315篇 |
出版年
2023年 | 56篇 |
2022年 | 196篇 |
2021年 | 243篇 |
2020年 | 182篇 |
2019年 | 185篇 |
2018年 | 180篇 |
2017年 | 155篇 |
2016年 | 326篇 |
2015年 | 288篇 |
2014年 | 390篇 |
2013年 | 644篇 |
2012年 | 802篇 |
2011年 | 889篇 |
2010年 | 509篇 |
2009年 | 426篇 |
2008年 | 662篇 |
2007年 | 620篇 |
2006年 | 565篇 |
2005年 | 504篇 |
2004年 | 443篇 |
2003年 | 359篇 |
2002年 | 391篇 |
2001年 | 233篇 |
2000年 | 187篇 |
1999年 | 142篇 |
1998年 | 75篇 |
1997年 | 84篇 |
1996年 | 101篇 |
1995年 | 85篇 |
1994年 | 79篇 |
1993年 | 60篇 |
1992年 | 64篇 |
1991年 | 54篇 |
1990年 | 55篇 |
1989年 | 36篇 |
1988年 | 29篇 |
1987年 | 16篇 |
1986年 | 12篇 |
1985年 | 32篇 |
1984年 | 20篇 |
1983年 | 19篇 |
1982年 | 20篇 |
1981年 | 17篇 |
1980年 | 14篇 |
1979年 | 15篇 |
1978年 | 17篇 |
1977年 | 10篇 |
1976年 | 13篇 |
1975年 | 11篇 |
1972年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
We describe the output performance of the 1415 nm emission in Nd:YAG in a plane-concave cavity under traditional pumping into the 4F5/2 level (808 nm) and direct in-band pumping into the 4F3/2 level (885 nm). An end-pumped Nd:YAG laser yielded maximum cw output power of 6.3 W and 4.2 W at 885 nm and 808 nm laser diode (LD) pumping, respectively. To the best of our knowledge, this is the highest output power of a LD-pumped 1415 nm laser. 相似文献
82.
H. Park M. Pleimling 《The European Physical Journal B - Condensed Matter and Complex Systems》2012,85(9):1-7
We explore the electronic and transport properties out of a biased multilayer hexagonal boron nitride (h-BN) by first-principles calculations. The band gaps of multilayer h-BN decrease almost linearly with increasing perpendicular electric field, irrespective of the layer number N and stacking manner. The critical electric filed (E 0) required to close the band gap decreases with the increasing N and can be approximated by E 0 = 3.2 / (N ? 1) (eV). We provide a quantum transport simulation of a dual-gated 4-layer h-BN with graphene electrodes. The transmission gap in this device can be effectively reduced by double gates, and a high on-off ratio of 3000 is obtained with relatively low voltage. This renders biased MLh-BN a promising channel in field effect transistor fabrication. 相似文献
83.
Chun SH Chai YS Jeon BG Kim HJ Oh YS Kim I Kim H Jeon BJ Haam SY Park JY Lee SH Chung JH Park JH Kim KH 《Physical review letters》2012,108(17):177201
We find the realization of large converse magnetoelectric (ME) effects at room temperature in a magnetoelectric hexaferrite Ba0.52Sr2.48Co2Fe24O41 single crystal, in which rapid change of electric polarization in low magnetic fields (about 5 mT) is coined to a large ME susceptibility of 3200 ps/m. The modulation of magnetization then reaches up to 0.62μ(B)/f.u. in an electric field of 1.14 MV/m. We find further that four ME states induced by different ME poling exhibit unique, nonvolatile magnetization versus electric field curves, which can be approximately described by an effective free energy with a distinct set of ME coefficients. 相似文献
84.
Sangsu Park Seungjae Jung Manzar Siddik Minseok Jo Jubong Park Seonghyun Kim Wootae Lee Jungho Shin Daeseok Lee Godeuni Choi Jiyong Woo Euijun Cha Byoung Hun Lee Hyunsang Hwang 《固体物理学:研究快报》2012,6(11):454-456
We propose a selector‐less Pr0.7Ca0.3MnO3 (PCMO) based resistive‐switching RAM (RRAM) for high‐density cross‐point memory array applications. First, we investigate the inhomogeneous barrier with an effective barrier height (Φeff), i.e., self‐formed Schottky barrier. In addition, a scalable 4F2 selector‐less cross‐point 1 kb RRAM array has been successfully fabricated, demonstrating set, reset, and read operation for high cell efficiency and high‐density memory applications. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
85.
Krokovny P Abe K Abe K Abe T Adachi I Ahn BS Aihara H Akatsu M Asano Y Aso T Aulchenko V Aushev T Bakich AM Ban Y Banas E Bay A Bedny I Behera PK Bizjak I Bondar A Bozek A Bracko M Brodzicka J Browder TE Casey BC Chang P Chao Y Chen KF Cheon BG Chistov R Choi SK Choi Y Danilov M Dong LY Drutskoy A Eidelman S Eiges V Enari Y Everton CW Fang F Fukunaga C Gabyshev N Garmash A Gershon T Golob B Gordon A Guo R Haba J Hanagaki K Handa F Harada Y Hayashii H Hazumi M Heenan EM Higuchi T Hinz L Hojo T 《Physical review letters》2002,89(23):231804
We report the first observation of a B meson decay that is not accessible by a direct spectator process. The channel B(0)-->D(+)(s)K- is found in a sample of 85 x 10(6) BB; events, collected with the Belle detector at KEKB, with a branching fraction B(B(0)-->D(+)(s)K-)=(4.6(+1.2)(-1.1)+/-1.3) x 10(-5). We also obtain evidence for the B0-->D(+)(s)pi(-) decay with branching fraction B(B0-->D(+)(s)pi(-))=(2.4(+1.0)(-0.8)+/-0.7) x 10(-5). This value may be used to extract a model-dependent value of |V(ub)|. 相似文献
86.
Phan Van Cuong Joonghoe Dho Hyo Yeol Park Do-Hyung Kim 《Applied Physics A: Materials Science & Processing》2009,95(2):567-571
This paper reports on the sonochemical-assisted synthesis of La0.7Sr0.3MnO3 (LSMO) nanoparticles (NPs) which have a single-crystalline perovskite structure. The average particle size of LSMO NPs was
controlled from about 40 to 120 nm by changing the annealing temperatures from 750 to 1050°C. The particle size, electrical
resistivity, and ferromagnetic transition temperature of LSMO NPs were strongly dependent on the annealing temperature. A
substantial decrease in resistivity and an enhancement in the insulator–metal transition temperature were found on increasing
the annealing temperature. Furthermore, the enhancement in magnetization and paramagnetic–ferromagnetic (PM–FM) transition
temperatures was observed as the annealing temperature increases. 相似文献
87.
Chin H. Wu Christopher V. Grant Gabriel A. Cook Sang Ho Park Stanley J. Opella 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2009,200(1):74-80
A strip-shield inserted between a high inductance double-tuned solenoid coil and the glass tube containing the sample improves the efficiency of probes used for high-field solid-state NMR experiments on lossy aqueous samples of proteins and other biopolymers. A strip-shield is a coil liner consisting of thin copper strips layered on a PTFE (polytetrafluoroethylene) insulator. With lossy samples, the shift in tuning frequency is smaller, the reduction in Q, and RF-induced heating are all significantly reduced when the strip-shield is present. The performance of 800 MHz 1H/15N and 1H/13C double-resonance probes is demonstrated on aqueous samples of membrane proteins in phospholipid bilayers. 相似文献
88.
In Jefferies-Johnson’s theory of Feynman’s operational calculi for noncommuting operators, the two operators T µ 1,µ 2 f(Ã, \(\tilde B\)) and T µ 2,µ1 f(Ã, \(\tilde B\)) are not equal. Relationships between these two operators are given, i.e., “measure permutation formulas” in Feynman’s operational calculi are developed; they correspond to the “index permutation formula” in Maslov’s discretized version of Feynman’s operational calculus. 相似文献
89.
GeunHyung Kim Hyeon Yoon YunKyung Park 《Applied Physics A: Materials Science & Processing》2010,100(4):1197-1204
A new drug delivery system (DDS) consisting of electrospun nanofibers is proposed. Layered mats of hydrophobic polycaprolactone
(PCL) and polyethylene oxide (PEO) nanofibers were prepared successfully in a layer-by-layer manner using an electrospinning
process. The PEO mat and drug were co-electrospun as a drug reservoir. Drug release rate was controlled physically by the
thickness of the electrospun nanofibrous PCL layer, and its release behavior was examined over time. Release tests showed
that the release behavior and the amount of initial burst of the drug were critically dependent on the thickness of the nanofibrous
PCL mat. The release of drug showed a linear relationship with the thickness of the porous electrospun PCL mat. In addition,
to demonstrate the feasibility of this type of DDS, the release behavior of the antimicrobial peptide HPA3NT3 from the nanofiber
system was examined. The release of the peptide was easily controlled by the PCL nanofiber thickness and the released peptide
did not lose biological activity. 相似文献
90.