全文获取类型
收费全文 | 878篇 |
免费 | 32篇 |
国内免费 | 3篇 |
专业分类
化学 | 561篇 |
晶体学 | 22篇 |
力学 | 6篇 |
数学 | 29篇 |
物理学 | 295篇 |
出版年
2022年 | 13篇 |
2021年 | 18篇 |
2020年 | 20篇 |
2019年 | 13篇 |
2018年 | 19篇 |
2017年 | 14篇 |
2016年 | 34篇 |
2015年 | 22篇 |
2014年 | 21篇 |
2013年 | 87篇 |
2012年 | 69篇 |
2011年 | 53篇 |
2010年 | 41篇 |
2009年 | 39篇 |
2008年 | 43篇 |
2007年 | 46篇 |
2006年 | 36篇 |
2005年 | 26篇 |
2004年 | 23篇 |
2003年 | 16篇 |
2002年 | 25篇 |
2001年 | 8篇 |
2000年 | 11篇 |
1999年 | 8篇 |
1998年 | 6篇 |
1997年 | 6篇 |
1996年 | 7篇 |
1995年 | 14篇 |
1994年 | 11篇 |
1993年 | 9篇 |
1992年 | 8篇 |
1991年 | 6篇 |
1990年 | 7篇 |
1989年 | 8篇 |
1988年 | 4篇 |
1987年 | 6篇 |
1985年 | 4篇 |
1984年 | 7篇 |
1983年 | 11篇 |
1982年 | 5篇 |
1981年 | 8篇 |
1980年 | 12篇 |
1979年 | 4篇 |
1977年 | 4篇 |
1976年 | 5篇 |
1975年 | 6篇 |
1973年 | 7篇 |
1970年 | 9篇 |
1963年 | 3篇 |
1957年 | 3篇 |
排序方式: 共有913条查询结果,搜索用时 15 毫秒
81.
82.
Chung P Ajitanand NN Alexander JM Anderson M Best D Brady FP Case T Caskey W Cebra D Chance JL Cole B Crowe K Das A Draper JE Gilkes ML Gushue S Heffner M Hirsch AS Hjort EL Huo L Justice M Kaplan M Keane D Kintner JC Klay J Krofcheck D Lacey RA Lauret J Lisa MA Liu H Liu YM McGrath R Milosevich Z Odyniec G Olson DL Panitkin SY Pinkenburg C Porile NT Rai G Ritter HG Romero JL Scharenberg R Schroeder L Srivastava B Stone NT Symons TJ Wienold T Witt R Whitfield J Wood L Zhang WN;E Collaboration 《Physical review letters》2001,86(12):2533-2536
Directed flow measurements for Lambda hyperons are presented and compared to those for protons produced in the same Au+Au collisions (2A, 4A, and 6A GeV; b<5-6 fm). The measurements indicate that Lambda hyperons flow consistently in the same direction but with smaller magnitudes. A strong positive flow [for Lambdas] has been predicted in calculations which include the influence of the Lambda-nucleon potential. The experimental flow ratio Lambda/p is in qualitative agreement with expectations (approximately 2/3) from the quark counting rule at 2A GeV but is found to decrease with increasing beam energy. 相似文献
83.
The possibilities of graphic STM image simulation of a clean Si(1 1 1) 7 × 7 surface at atomic level are indicated. The presented procedure takes into account various types of deformation on the surface near the Fermi level in order to classify them and explain their origin. It also gives a clear hint to insert relevant physical phenomena in a suggested analysis. This goal is achieved exploiting the results of DAS (dimmer adatom stacing fault) model by means of standard mathematical programmes. A clean Si(1 1 1) 7 × 7 surface is considered as the representative example, but similar evaluation is possible for another non-metal and metal surfaces. 相似文献
84.
Proton induced X-ray emission has been used to measureL-subshell and total ionization cross-sections of Au, Pb and Bi in the energy range of 200–350 keV. The ionization cross-sections have been extracted using the X-ray spectra and other quantities like fluorescence yields, transition probabilities, relative widths and Coster-Krönig fraction etc. involved in the process. The results have been compared with the cross-sections measured before and discussed in the light of known theories regarding the ion-atom collisions. 相似文献
85.
Why chaos is rarely observed in natural populations 总被引:2,自引:0,他引:2
An attempt has been made to understand why chaotic dynamics have received poor evidential support from field studies. Our study opens up the possibility that the cause of failure might not be poor quality of data, as pointed out by earlier authors, but an ecological reality. We have designed two model food chains to examine whether there is a biological basis for the crisis. This investigation is effected with the help of a new method which we introduce at an appropriate place in the text. The fact that chaos exists in a narrow range of parametric values in both the model systems suggests that the crisis indeed has a biological origin. 相似文献
86.
87.
The solubility of NdPO4(c) was studied at 23±2 °C from both the over and undersaturation directions, with pH ranging from 0 to 9, P concentrations ranging from 0.0003 to 1.00M, and equilibration periods ranging from 6 to 57 days. Equilibrium was reached in <6 days. From the H+, Nd, and P concentrations in equilibrated solutions, the logarithm of the thermodynamic equilibrium constant for the reaction (NdPO4(c) Nd3++PO4
3-) was calculated to be -24.65±0.23 and the value of the Pitzer ion-interaction parameter (2)for Nd3+-H2PO4
- was determined to be -92.9. Predictions based on these thermodynamic quantities were in excellent agreement with the experimental data. 相似文献
88.
89.
90.
A new chelating resin was synthesised by the modification of styrene-divinylbenzene (2%) copolymer and incorporation of dithiocarbamate groups. The polydithiocarbamate resin was characterised by elemental analysis, thermal studies and IR studies. The analytical characteristics of the sorbent were established and optimum sorption conditions for Cu, Ni, Pb, Fe, As and Mn determined. The total sorption capacity of the resin was 37 mg g−1 for Ni(II), 35 mg g−1 for Cu(II), 29 mg g−1 for Fe(III) and 23 mg g−1 for Pb(II). The optimum pH for the removal of metal ions was 3-5 for Ni(II), 5 for Cu(II), 4 for Fe(III) and 4-5 for Pb(II). High sorption capacity was observed when compared with other conventional chelating polymers. The sorption kinetics was fairly rapid, as apparent from the loading half time t1/2 values, indicating a better accessibility of the chelating sites. 相似文献