全文获取类型
收费全文 | 6319篇 |
免费 | 165篇 |
国内免费 | 44篇 |
专业分类
化学 | 4649篇 |
晶体学 | 66篇 |
力学 | 143篇 |
数学 | 722篇 |
物理学 | 948篇 |
出版年
2023年 | 26篇 |
2022年 | 48篇 |
2021年 | 50篇 |
2020年 | 78篇 |
2019年 | 96篇 |
2018年 | 68篇 |
2017年 | 48篇 |
2016年 | 129篇 |
2015年 | 108篇 |
2014年 | 120篇 |
2013年 | 310篇 |
2012年 | 373篇 |
2011年 | 462篇 |
2010年 | 220篇 |
2009年 | 194篇 |
2008年 | 401篇 |
2007年 | 451篇 |
2006年 | 445篇 |
2005年 | 435篇 |
2004年 | 398篇 |
2003年 | 316篇 |
2002年 | 280篇 |
2001年 | 98篇 |
2000年 | 73篇 |
1999年 | 73篇 |
1998年 | 79篇 |
1997年 | 56篇 |
1996年 | 84篇 |
1995年 | 63篇 |
1994年 | 59篇 |
1993年 | 44篇 |
1992年 | 44篇 |
1991年 | 48篇 |
1990年 | 44篇 |
1989年 | 36篇 |
1988年 | 39篇 |
1987年 | 35篇 |
1986年 | 32篇 |
1985年 | 53篇 |
1984年 | 54篇 |
1983年 | 49篇 |
1982年 | 47篇 |
1981年 | 49篇 |
1980年 | 44篇 |
1979年 | 44篇 |
1978年 | 49篇 |
1977年 | 40篇 |
1976年 | 38篇 |
1975年 | 24篇 |
1974年 | 25篇 |
排序方式: 共有6528条查询结果,搜索用时 15 毫秒
931.
Duan Z. Zhang Qisu Zou W. Brian VanderHeyden Xia Ma 《Journal of computational physics》2008,227(6):3159-3173
The particle-in-cell method (PIC), especially the latest version of it, the material point method (MPM), has shown significant advantage over the pure Lagrangian method or the pure Eulerian method in numerical simulations of problems involving large deformations. It avoids the mesh distortion and tangling issues associated with Lagrangian methods and the advection errors associated with Eulerian methods. Its application to multiphase flows or multi-material deformations, however, encounters a numerical difficulty of satisfying continuity requirement due to the inconsistence of the interpolation schemes used for different phases. It is shown in Section 3 that current methods of enforcing this requirement either leads to erroneous results or can cause significant accumulation of errors. In the present paper, a different numerical method is introduced to ensure that the continuity requirement is satisfied with an error consistent with the discretization error and will not grow beyond that during the time advancement in the calculation. This method is independent of physical models. Its numerical implementation is quite similar to the common method used in Eulerian calculations of multiphase flows. Examples calculated using this method are presented. 相似文献
932.
Rosner JL Alexander JP Cassel DG Duboscq JE Ehrlich R Fields L Gibbons L Gray R Gray SW Hartill DL Heltsley BK Hertz D Jones CD Kandaswamy J Kreinick DL Kuznetsov VE Mahlke-Krüger H Mohapatra D Onyisi PU Patterson JR Peterson D Riley D Ryd A Sadoff AJ Shi X Stroiney S Sun WM Wilksen T Athar SB Patel R Yelton J Rubin P Eisenstein BI Karliner I Mehrabyan S Lowrey N Selen M White EJ Wiss J Mitchell RE Shepherd MR Besson D Pedlar TK Cronin-Hennessy D Gao KY Hietala J Kubota Y Klein T Lang BW 《Physical review letters》2008,100(22):221801
We exploit the quantum coherence between pair-produced D0 and D[over]0 in psi(3770) decays to study charm mixing, which is characterized by the parameters x and y, and to make a first determination of the relative strong phase delta between D0-->K+pi- and D[over]0-->K+pi-. Using 281 pb(-1) of e+e- collision data collected with the CLEO-c detector at Ecm=3.77 GeV, as well as branching fraction input and time-integrated measurements of RM identical with (x2 + y2)/2 and RWS identical with Gamma(D0-->K+pi-)/Gamma(D[over]0-->K+pi-) from other experiments, we find cosdelta=1.03(-0.17)(+0.31)+/-0.06, where the uncertainties are statistical and systematic, respectively. By further including other mixing parameter measurements, we obtain an alternate measurement of cosdelta=1.10+/-0.35+/-0.07, as well as x sindelta=(4.4(-1.8)(+2.7)+/-2.9)x10(-3) and delta=(22(-12-11)(+11+9)) degrees . 相似文献
933.
Using recent precision measurements of cosmological parameters, we re-examine whether these observations alone, independent of type Ia supernova surveys, are sufficient to imply the existence of dark energy. We find that best measurements of the age of the Universe t0, the Hubble parameter H0 and the matter fraction Ωm strongly favor an equation of state defined by (w<−1/3). This result is consistent with the existence of a repulsive, acceleration-causing component of energy if the Universe is nearly flat. 相似文献
934.
935.
Nicole L. Wagner Francis J. Timmers Daniel J. Arriola Guenter Jueptner Brian G. Landes 《Macromolecular rapid communications》2008,29(17):1438-1443
Polycarbonate/polyethylene random block copolymers (RBCs) have been produced using olefin metathesis catalysis in a process termed segment interchange metathesis. An olefin metathesis catalyst tolerant of polar functionality was added to reagent polycarbonate and polyethylene polymers which contained internal unsaturated carbon–carbon bonds. Subsequent metathesis occurred, segmenting the reagent polymers, resulting in RBCs. The block copolymers self-assembled into microphase structures which persisted into the melt state as determined by small angle X-ray scattering (SAXS).
936.
937.
Brian J. Riley S.K. Sundaram Bradley R. Johnson Laxmikant V. Saraf 《Journal of Non》2008,354(10-11):813-816
Chemical etching rates for two different chalcogenide glass compositions, As40S60 and As24S38Se38, were studied using sodium hydroxide based etchant solutions. Etching was performed using a variation of standard photolithographic masking and wet-etching techniques. Variations in etch rate with NaOH concentration and glass composition were observed. The depth of etch was characterized using an optical profilometer. Etch rate differences as large as three orders of magnitude between these two glasses were observed at low NaOH concentration (0.053 M). We present a single variable etch rate curve of etch depth per time (nm/s) versus NaOH overall solution concentration (in M) for these two different chalcogenide glasses. This technology shows promise for fabricating photonic structures and has potential applications in fabricating novel photonic bandgap structures that will function in the long-wave infrared (LWIR) regime. 相似文献
938.
939.
940.