全文获取类型
收费全文 | 35030篇 |
免费 | 1598篇 |
国内免费 | 691篇 |
专业分类
化学 | 23297篇 |
晶体学 | 345篇 |
力学 | 1344篇 |
综合类 | 47篇 |
数学 | 3272篇 |
物理学 | 9014篇 |
出版年
2023年 | 267篇 |
2022年 | 611篇 |
2021年 | 771篇 |
2020年 | 681篇 |
2019年 | 704篇 |
2018年 | 586篇 |
2017年 | 566篇 |
2016年 | 1078篇 |
2015年 | 892篇 |
2014年 | 1167篇 |
2013年 | 2022篇 |
2012年 | 2566篇 |
2011年 | 2785篇 |
2010年 | 1781篇 |
2009年 | 1595篇 |
2008年 | 2283篇 |
2007年 | 2124篇 |
2006年 | 1966篇 |
2005年 | 1789篇 |
2004年 | 1563篇 |
2003年 | 1225篇 |
2002年 | 1199篇 |
2001年 | 823篇 |
2000年 | 706篇 |
1999年 | 468篇 |
1998年 | 361篇 |
1997年 | 384篇 |
1996年 | 414篇 |
1995年 | 328篇 |
1994年 | 325篇 |
1993年 | 330篇 |
1992年 | 315篇 |
1991年 | 258篇 |
1990年 | 180篇 |
1989年 | 164篇 |
1988年 | 163篇 |
1987年 | 139篇 |
1986年 | 110篇 |
1985年 | 184篇 |
1984年 | 128篇 |
1983年 | 106篇 |
1982年 | 133篇 |
1981年 | 93篇 |
1980年 | 84篇 |
1978年 | 82篇 |
1977年 | 89篇 |
1976年 | 96篇 |
1975年 | 104篇 |
1974年 | 82篇 |
1973年 | 106篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
161.
162.
Alam MS Kim IJ Nemati B O'Neill JJ Severini H Sun CR Zoeller MM Crawford G Daubenmier CM Fulton R Fujino D Gan KK Honscheid K Kagan H Kass R Lee J Malchow R Morrow F Skovpen Y Sung M White C Butler F Fu X Kalbfleisch G Ross WR Skubic P Snow J Wang PL Wood M Brown DN Fast J McIlwain RL Miao T Miller DH Modesitt M Payne D Shibata EI Shipsey IP Wang PN Battle M Ernst J Kwon Y Roberts S Thorndike EH Wang CH Dominick J Lambrecht M Sanghera S Shelkov V Skwarnicki T Stroynowski R Volobouev I Wei G 《Physical review D: Particles and fields》1994,50(1):43-68
163.
164.
S. Czajkowski M. Bernas P. Armbruster H. Geissel C. Kozhuharov G. Münzenberg D. Vieira Ph. Dessagne Ch. Miehe E. Hanelt G. Audi J. K. P. Lee 《Zeitschrift für Physik A Hadrons and Nuclei》1994,348(4):267-272
Neutron-rich Co and Fe isotopes produced by86Kr projectile fragmentation at 500 MeV/u were separated and identified using the fragment separator (FrS) in a bunched energy mode.66Co and65Fe ions were selectively implanted in a double PIN-diode array where the-decay signals were measured. The half-lives were deduced from time correlations between implantation and-decay signals. The remeasurement of the66Co half-life confirms the isotope identification. The value of the65Fe half-life was found to be 0.45±0.15 s. 相似文献
165.
D. R. Lee T. P. J. Han B. Henderson 《Applied Physics A: Materials Science & Processing》1994,59(4):365-372
Studies of the photoluminescence spectra of Cr3+ ions in KMgF3 crystals co-doped with Cr3+ and Ni2+ ions are reported. Several crystal field sites are identified by the different R-line spectra due to the 2
E4
A
2 transition and broadband luminescences associated with the 4
T
24
A
2 transitions. Cr3+ ions substituting without local charge compensation on the octahedral Mg2+ site give rise to a low temperature R line in photoluminescence at =702.3 nm with a radiative decaytime of 3 ms at T=14 K. At T=300 K this isotropic centre gives rise to an unpolarized broadband 4
T
24
A
2 emission, which results from the thermal occupancy of an excited 4
T
2 state just above the 2
E level which, at lower temperature, gives rise to emission in the R-line. Other crystal field sites are due to some Cr3+ ions having Mg2+ or K+ vacancies in nearest-neighbour positions, these vacancies being required to maintain charge neutrality in doped fluoride perovskites. The Cr3+–K+ vacancy complex results in the centre having trigonal symmetry, and low temperature, photoluminescence via R
1 and R
2 lines at 716.8 nm and 716.0 nm, respectively. Finally, Cr3+ ions having a nearest neighbour Mg2+ vacancy have tetragonal symmetry, experiencing weak crystal fields. In consequence, the 4
T
2 level lies below 2
E and the photoluminescence spectrum at low temperature takes the form of a polarized broad 4
T
24
A
2 band with peak at 760 nm and radiative decaytime of 54 s. 相似文献
166.
We present the point of view that both the vortices and the east-west zonal winds of Jupiter are confined to the planet's shallow weather layer and that their dynamics is completely described by the weakly dissipated, weakly forced quasigeostrophic (QG) equation. The weather layer is the region just below the tropopause and contains the visible clouds. The forcing mimics the overshoot of fluid from an underlying convection zone. The late-time solutions of the weakly forced and dissipated QG equations appear to be a small subset of the unforced and undissipated equations and are robust attractors. We illustrate QG vortex dynamics and attempt to explain the important features of Jupiter's Great Red Spot and other vortices: their shapes, locations with respect to the extrema of the east-west winds, stagnation points, numbers as a function of latitude, mergers, break-ups, cloud morphologies, internal distributions of vorticity, and signs of rotation with respect to both the planet's rotation and the shear of their surrounding east-west winds. Initial-value calculations in which the weather layer starts at rest produce oscillatory east-west winds. Like the Jovian winds, the winds are east-west asymmetric and have Karman vortex streets located only at the west-going jets. From numerical calculations we present an empirically derived energy criterion that determines whether QG vortices survive in oscillatory zonal flows with nonzero potential vorticity gradients. We show that a recent proof that claims that all QG vortices decay when embedded in oscillatory zonal flows is too restrictive in its assumptions. We show that the asymmetries in the cloud morphologies and numbers of cyclones and anticyclones can be accounted for by a QG model of the Jovian atmosphere, and we compare the QG model with competing models. 相似文献
167.
Abdurashitov JN Gavrin VN Girin SV Gorbachev VV Ibragimova TV Kalikhov AV Khairnasov NG Knodel TV Kornoukhov VN Mirmov IN Shikhin AA Veretenkin EP Vermul VM Yants VE Zatsepin GT Bowles TJ Nico JS Teasdale WA Wark DL Cherry ML Karaulov VN Levitin VL Maev VI Nazarenko PI Shkol'nik VS Skorikov NV Cleveland BT Daily T Davis R Lande K Lee CK Wildenhain PW Khomyakov YS Zvonarev AV Elliott SR Wilkerson JF 《Physical review letters》1996,77(23):4708-4711
168.
Akiba Y Beavis D Beery P Britt HC Budick B Chasman C Chen Z Chi CY Chu YY Cianciolo V Cole BA Costales JB Crawford HJ Cumming JB Debbe R Engelage J Fung SY Gonin M Gushue S Hamagaki H Hansen O Hayano RS Hayashi S Homma S Kaneko H Kang J Kaufman S Kehoe WL Kurita K Ledoux RJ Levine MJ Miake Y Morrison DP Morse RJ Moskowitz B Nagamiya S Namboodiri MN Nayak TK Olness J Parsons CG Remsberg LP Roehrich D Rothschild P Sakurai H Sangster TC Seto R Soltz R Stankus P Steadman SG Stephans GS Sung T 《Physical review letters》1996,76(12):2021-2024
169.
170.