全文获取类型
收费全文 | 150篇 |
免费 | 1篇 |
国内免费 | 3篇 |
专业分类
化学 | 59篇 |
数学 | 24篇 |
物理学 | 71篇 |
出版年
2022年 | 1篇 |
2021年 | 1篇 |
2015年 | 1篇 |
2014年 | 3篇 |
2013年 | 8篇 |
2012年 | 2篇 |
2011年 | 7篇 |
2010年 | 2篇 |
2009年 | 4篇 |
2008年 | 8篇 |
2007年 | 14篇 |
2006年 | 12篇 |
2005年 | 10篇 |
2004年 | 7篇 |
2003年 | 10篇 |
2002年 | 14篇 |
2001年 | 4篇 |
2000年 | 3篇 |
1999年 | 3篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1994年 | 3篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 5篇 |
1986年 | 1篇 |
1985年 | 6篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1980年 | 2篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1975年 | 2篇 |
1973年 | 1篇 |
1931年 | 1篇 |
排序方式: 共有154条查询结果,搜索用时 812 毫秒
71.
Centrality dependence of direct photon production in (square root)S(NN) = 200 GeV Au + Au collisions
Adler SS Afanasiev S Aidala C Ajitanand NN Akiba Y Alexander J Amirikas R Aphecetche L Aronson SH Averbeck R Awes TC Azmoun R Babintsev V Baldisseri A Barish KN Barnes PD Bassalleck B Bathe S Batsouli S Baublis V Bazilevsky A Belikov S Berdnikov Y Bhagavatula S Boissevain JG Borel H Borenstein S Brooks ML Brown DS Bruner N Bucher D Buesching H Bumazhnov V Bunce G Burward-Hoy JM Butsyk S Camard X Chai JS Chand P Chang WC Chernichenko S Chi CY Chiba J Chiu M Choi IJ Choi J Choudhury RK Chujo T 《Physical review letters》2005,94(23):232301
The first measurement of direct photons in Au + Au collisions at (square root)S(NN) = 200 GeV is presented. The direct photon signal is extracted as a function of the Au + Au collision centrality and compared to next-to-leading order perturbative quantum chromodynamics calculations. The direct photon yield is shown to scale with the number of nucleon-nucleon collisions for all centralities. 相似文献
72.
Adler SS Afanasiev S Aidala C Ajitanand NN Akiba Y Al-Jamel A Alexander J Amirikas R Aoki K Aphecetche L Armendariz R Aronson SH Averbeck R Awes TC Azmoun B Azmoun R Babintsev V Baldisseri A Barish KN Barnes PD Bassalleck B Bathe S Batsouli S Baublis V Bauer F Bazilevsky A Belikov S Bennett R Berdnikov Y Bhagavatula S Bjorndal MT Boissevain JG Borel H Borenstein S Boyle K Brooks ML Brown DS Bruner N Bucher D Buesching H Bumazhnov V Bunce G Burward-Hoy JM Butsyk S Camard X Campbell S Chai JS 《Physical review letters》2005,94(23):232302
New measurements are presented for charged hadron azimuthal correlations at midrapidity in Au+Au collisions at (square root)s(NN) = 62.4 and 200 GeV. They are compared to earlier measurements obtained at (square root)s(NN) = 130 GeV and in Pb + Pb collisions at (square root)s(NN) = 17.2 GeV. Sizeable anisotropies are observed with centrality and transverse momentum (pT) dependence characteristic of elliptic flow (upsilon2). For a broad range of centralities, the observed magnitudes and trends of the differential anisotropy, upsilon2(pT), change very little over the collision energy range (square root)s(NN) = 62-200 GeV, indicating saturation of the excitation function for upsilon2 at these energies. Such a saturation may be indicative of the dominance of a very soft equation of state for (square root)s(NN) approximately 60-200 GeV. 相似文献
73.
Adler SS Afanasiev S Aidala C Ajitanand NN Akiba Y Alexander J Amirikas R Aphecetche L Aronson SH Averbeck R Awes TC Azmoun R Babintsev V Baldisseri A Barish KN Barnes PD Bassalleck B Bathe S Batsouli S Baublis V Bazilevsky A Belikov S Berdnikov Y Bhagavatula S Boissevain JG Borel H Borenstein S Brooks ML Brown DS Bruner N Bucher D Buesching H Bumazhnov V Bunce G Burward-Hoy JM Butsyk S Camard X Chai JS Chand P Chang WC Chernichenko S Chi CY Chiba J Chiu M Choi IJ Choi J Choudhury RK Chujo T 《Physical review letters》2005,94(12):122302
The production of deuterons and antideuterons in the transverse momentum range 1.1
相似文献
74.
Amberlyst-15 has been used to catalyze regioselective additions of phenols to α,β-unsaturated ketones in yields of 20–90%. The reaction is superior to the analogous reaction employing concentrated sulfuric acid in affording greater yields and purer products with a minimum of laboratory operations. 相似文献
75.
α-Aminonitriles have been synthesized by a Strecker synthesis from aldehydes and ketones under mild catalytic, metal-free conditions. Aromatic aldehydes (1 equiv) were reacted with aromatic and 1° or 2° aliphatic amines (1 equiv) in EtOH containing 3 mol % of NH4Cl to give high yields of α-aminonitriles. An alternative to adding NH4Cl as a catalyst involved the use of excess TMSCN (1 equiv) and to promote the process. The reaction was also successful under microwave conditions using excess TMSCN with no solvent. Ketones similarly reacted with aromatic amines and excess TMSCN under conventional and microwave heating, but 30 mol % of added NH4Cl was required for optimum conversion. 相似文献
76.
Addition of hydrogen bromide gas to acrolein followed by reaction with a stabilized triphenylphosphoranylidene ylide in benzene solvent affords (E)-5-bromo-2-pentenoate esters in 60–80% yield with greater than 90% selectivity for the E double bond isomer. 相似文献
77.
The title compound was prepared in 48% overall yield using a seven-step sequence. The synthesis involves stepwise construction of a 3-formyl-3,3-diphenypropyl side chain from the double bond of 3-ethenyl-3-methylcyclohexanone followed by aldol ring closure. The approach represents a general strategy for the synthesis of a number of (±)-7,7-diary1–3,4,4a,5,6,7-hexahydro-1(2H)-naphthalenones. 相似文献
78.
Since 1996, eight elections have taken place in postcommunist Europe and Eurasia that have replaced illiberal with liberal governments. There is ample evidence that these “electoral revolutions” reflected the cross-national diffusion of a distinctive model of regime change that was developed elsewhere and that was designed to promote democratization in authoritarian political contexts featuring semi-competitive elections. This electoral model spread throughout the postcommunist region because of both shared perceptions by opposition groups of similar local conditions and the existence of transnational democracy promotion networks that included local, regional and American participants. As these revolutions spread, however, they were less successful in carrying through democratic change-in part because local conditions were less supportive and in part because authoritarian leaders and their international allies were both forewarned and forearmed. 相似文献
79.
Carol A. Venanzi Preston M. Canzius Zhifeng Zhang Jeffrey D. Bunce 《Journal of computational chemistry》1989,10(8):1038-1052
The method of molecular mechanics is used to investigate the structural and electrostatic features of molecular recognition by β-cyclodextrin and capped β-cyclodextrin models of α-chymotrypsin. Since capped β-cyclodextrin has been shown to be the more effective biomimetic catalyst, these features of molecular recognition can be interpreted in terms of the relationship between molecular structure and catalytic function. Calculations in vacuo show that the addition of an N-methylformamide “cap” substituent to each glucose unit appears to change the relative orientation of some glucose fragments from that found in the X-ray structure of the β-cyclodextrin macrocycle. These results indicate that certain structural components of molecular recognition, such as the orientation of the secondary hydroxyls and the related orientation of the caps, may be implicated in the catalysis. In addition, the electrostatic component of molecular recognition was investigated by the analysis of molecular electrostatic potential maps calculated in planes parallel to the average plane of the glycosidic oxygen atoms. The results indicate that the addition of the caps to the β-cyclodextrin macrocycle subtly alters the pattern of the maps in each plane. However, the general qualitative features of electrostatic recognition by β-cyclodextrin and capped β-cyclodextrin are similar. 相似文献
80.