全文获取类型
收费全文 | 1458篇 |
免费 | 31篇 |
国内免费 | 12篇 |
专业分类
化学 | 937篇 |
晶体学 | 19篇 |
力学 | 10篇 |
数学 | 135篇 |
物理学 | 400篇 |
出版年
2021年 | 11篇 |
2020年 | 12篇 |
2019年 | 23篇 |
2018年 | 8篇 |
2017年 | 15篇 |
2016年 | 21篇 |
2015年 | 16篇 |
2014年 | 32篇 |
2013年 | 66篇 |
2012年 | 75篇 |
2011年 | 95篇 |
2010年 | 38篇 |
2009年 | 48篇 |
2008年 | 82篇 |
2007年 | 83篇 |
2006年 | 86篇 |
2005年 | 88篇 |
2004年 | 84篇 |
2003年 | 68篇 |
2002年 | 52篇 |
2001年 | 38篇 |
2000年 | 32篇 |
1999年 | 18篇 |
1998年 | 19篇 |
1997年 | 21篇 |
1996年 | 24篇 |
1995年 | 9篇 |
1994年 | 16篇 |
1993年 | 15篇 |
1992年 | 15篇 |
1991年 | 18篇 |
1990年 | 15篇 |
1989年 | 17篇 |
1988年 | 17篇 |
1987年 | 8篇 |
1986年 | 13篇 |
1985年 | 23篇 |
1984年 | 26篇 |
1983年 | 11篇 |
1982年 | 17篇 |
1981年 | 19篇 |
1980年 | 15篇 |
1979年 | 11篇 |
1978年 | 12篇 |
1976年 | 8篇 |
1975年 | 16篇 |
1974年 | 5篇 |
1973年 | 8篇 |
1972年 | 5篇 |
1968年 | 4篇 |
排序方式: 共有1501条查询结果,搜索用时 93 毫秒
151.
152.
HE Jian-jun S.Kubono T.Teranishi M.Notani H.Baba S.Nishimura J.Y.Moon M.Nishimura S.Michimasa H.Iwasaki Y.Yanagisawa N.Hokoiwa M.Kibe J.H.Lee S.Kato Y.Gono C.S.Lee 《原子核物理评论》2009,26(Z1)
Proton resonant states in ~(22)Mg have been investigated by the resonant elastic scattering of ~(21)Na+p.The ~(21)Na beam with a mean energy of 4.00 MeV/u was separated by the CNS radioactive ion beam separator(CRIB) and bombarded a thick(CH_2)_n target.The energy spectra of recoiled protons were measured at scattering angles of θ_(cm)~172° and 146°,respectively.A new state at 7.06 MeV has been observed clearly and another new one at 7.28 MeV is tentatively identified due to its low statistics.The proton resonant parameters were deduced from an R-matrix analysis of the differential cross section data.The astrophysical resonant reaction rate for the ~(18)Ne(α,p) ~(21)Na reaction has been estimated,and it is about five times larger than that assumed before. 相似文献
153.
Masakazu Tatsuno Hajime Amamoto Koji Ishi-i
Tetsunobu Takayama
《Fluid Dynamics Research》1991,8(5-6):253-272The stable posture of a pair of parallel circular cylinders in a uniform flow was experimentally studied when it was free to rotate about an axis at the middle of the two cylinders. The cylinder pair comes to rest facing the oncoming flow side by side, the line connecting the centers of the two cylinders being perpendicular to the flow, when s/d = 0.5, where s is the distance between the center of rotation and the central axis of each cylinder and d is the diameter of the cylinder. When s/d = 1.0 or 1.5, the cylinder pair is stable both in tandem, with one cylinder behind the other, and in side-by-side arrangements to the oncoming flow. When s/d 2.0, the cylinder pair is stable only in tandem arrangements. 相似文献
154.
Takuya Shimosaka Masakazu Izako Katsumi Uchiyama Toshiyuki Hobo 《Analytical sciences》2005,21(4):469-472
In scanning microscopy by total internal reflection with thermal lens spectroscopy, its spatial resolution depends on the distance between the sample and a converging lens, which corresponds to the objective lens in an ordinary optical microscope. It was found that the resolution was best when the signal induced by the thermal lens effect was maximum. The distance was precisely adjusted by monitoring the signal intensity, and the resolution became twice better than that previously reported. Using a shorter focal-length lens, a resolution of 1.9 microm was attained. 相似文献
155.
Interference of transverse rings in multifilamentation of powerful femtosecond laser pulses in air 总被引:3,自引:0,他引:3
S. L. Chin S. Petit W. Liu A. Iwasaki M. -C. Nadeau V. P. Kandidov O. G. Kosareva K. Yu. Andrianov 《Optics Communications》2002,210(3-6):329-341
We observe multiple filaments and interference of their ring structures in the propagation of 14 mJ, 45 fs infrared laser pulse in air. We suggest a simple physical model describing the formation and the interference of rings as the result of superposition of the background field of the whole beam and the fields that diverge from the filaments due to the defocusing in the laser-produced plasma. The size and the number of maxima in the interference pattern depend on the position of the filament formation along the direction of propagation. The simulated picture of the ring structure interference is in qualitative agreement with the one obtained from the experiment. 相似文献
156.
Akiko Takeda Katsuki Fujisawa Yusuke Fukaya Masakazu Kojima 《Journal of Global Optimization》2002,24(2):237-260
As computing resources continue to improve, global solutions for larger size quadrically constrained optimization problems become more achievable. In this paper, we focus on larger size problems and get accurate bounds for optimal values of such problems with the successive use of SDP relaxations on a parallel computing system called Ninf (Network-based Information Library for high performance computing). 相似文献
157.
This study discusses the evolutionary nature of knowledge acquisition at micro and macro levels, and in particular when the process involves an artificial agent's interpretative devices. In order to accomplish this, we propose using an individual learning model (or inner‐world reconstruction model) that in our view overcomes neoclassic epistemological holdups and may increase the predictive power of computational economics, by letting an artificial agent's knowledge evolve by itself, irrespective of globally specified goals or individual motives of behavior; using simultaneous (or parallel) genetic algorithms (GA) to evolve a single agent's learning strategy, each GA with different general specifications, in a multiagent setting. © 2006 Wiley Periodicals, Inc. Complexity 11: 12–19, 2006 相似文献
158.
Hiroaki Yamamoto Youji Kanie Masakazu Arakawa Keiji Taniguchi 《Applied Physics A: Materials Science & Processing》1990,50(6):577-581
The transmission coefficient and the resonance condition in the one-dimensional rectangular double-, triple-, quadruple-, and quintuple-barrier structures are derived theoretically under the assumption of the constant tunneling effective mass. It is found that the resonance energies are different from the eigenvalues in the quantum well due to coupling between wells in the multiple-barrier (much more than triple-barrier) structures. It is confirmed that the transmission spectrum is a Lorentzian near to energies of resonance. 相似文献
159.
Masakazu Yoshikawa Katsunori Koso Kyoichi Yonetani Satoshi Kitamura Satoshi Kimura 《Journal of polymer science. Part A, Polymer chemistry》2005,43(2):385-396
Molecularly imprinted polymeric membranes were prepared from various oligopeptide tweezers by the adoption of N‐α‐tert‐butoxycarbonyl‐D ‐tryptophan (Boc‐D ‐Trp) or N‐α‐tert‐butoxycarbonyl‐L ‐tryptophan (Boc‐L ‐Trp) as a print molecule. The chiral recognition ability of the formed molecular recognition sites was dependent on the absolute configuration of the print molecule adopted in the membrane preparation (molecular imprinting) process, whereas the candidate oligopeptide tweezers consisted of the L ‐amino acid residues. In other words, the membranes imprinted by the D ‐isomer recognized the D ‐isomer in preference to the corresponding L ‐isomer, and vice versa. The affinity constant between the target molecule and the chiral recognition site from the oligopeptide tweezers was higher than that from a single‐strand oligopeptide derivative. Those membranes selectively transported the enantiomer, which was preferentially incorporated into the membrane by dialysis. The permselectivities for these membranes exceeded their adsorption selectivities. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 385–396, 2005 相似文献
160.
Belous K Shapkin M Sokolov A Abe K Abe K Adachi I Aihara H Anipko D Arinstein K Aulchenko V Aushev T Bakich AM Barberio E Bay A Bedny I Bitenc U Bizjak I Blyth S Bondar A Bozek A Bracko M Browder TE Chang MC Chen A Chen KF Chen WT Cheon BG Chistov R Choi Y Choi YK Cole S Dalseno J Drutskoy A Eidelman S Epifanov D Fratina S Fujikawa M Gabyshev N Gershon T Gokhroo G Golob B Ha H Haba J Hasegawa Y Hayasaka K Hayashii H Hazumi M Heffernan D Hokuue T Hoshi Y Hou S Hou WS Iijima T Ikado K Imoto A 《Physical review letters》2007,99(1):011801
The mass of the tau lepton has been measured in the decay mode tau-->3pinutau using a pseudomass technique. The result obtained from 414 fb-1 of data collected with the Belle detector is Mtau=[1776.61+/-0.13(stat)+/-0.35(sys)] MeV/c2. The upper limit on the relative mass difference between positive and negative tau leptons is |Mtau+-Mtau-|/Mtau<2.8 x 10-4 at 90% confidence level. 相似文献