全文获取类型
收费全文 | 4629篇 |
免费 | 139篇 |
国内免费 | 11篇 |
专业分类
化学 | 2504篇 |
晶体学 | 50篇 |
力学 | 137篇 |
数学 | 480篇 |
物理学 | 1608篇 |
出版年
2022年 | 64篇 |
2021年 | 65篇 |
2020年 | 81篇 |
2019年 | 79篇 |
2018年 | 90篇 |
2017年 | 62篇 |
2016年 | 112篇 |
2015年 | 82篇 |
2014年 | 108篇 |
2013年 | 274篇 |
2012年 | 239篇 |
2011年 | 279篇 |
2010年 | 167篇 |
2009年 | 159篇 |
2008年 | 224篇 |
2007年 | 228篇 |
2006年 | 239篇 |
2005年 | 211篇 |
2004年 | 139篇 |
2003年 | 134篇 |
2002年 | 117篇 |
2001年 | 94篇 |
2000年 | 89篇 |
1999年 | 64篇 |
1998年 | 49篇 |
1997年 | 50篇 |
1996年 | 57篇 |
1995年 | 54篇 |
1994年 | 55篇 |
1993年 | 60篇 |
1992年 | 58篇 |
1991年 | 35篇 |
1990年 | 57篇 |
1989年 | 42篇 |
1988年 | 46篇 |
1987年 | 46篇 |
1986年 | 33篇 |
1985年 | 58篇 |
1984年 | 45篇 |
1983年 | 45篇 |
1982年 | 40篇 |
1981年 | 38篇 |
1980年 | 42篇 |
1979年 | 36篇 |
1978年 | 43篇 |
1977年 | 40篇 |
1976年 | 39篇 |
1975年 | 31篇 |
1974年 | 41篇 |
1973年 | 40篇 |
排序方式: 共有4779条查询结果,搜索用时 125 毫秒
101.
102.
103.
104.
105.
Rita Das Nigamananda Das Anadi C. Dash Ansuman Roy Shyamal K. Sarkar 《Transition Metal Chemistry》1996,21(1):90-94
Summary The reaction of ()-(tetren)CoOH2+ with S2O
3
2-
in the 7.25–8.28 pH range at 20–40 °C yielded S- (yellow) and O- (purple) bonded thiosulfato(tetren)cobalt(III) complexes, the former in larger quantities. The rate determining step is preceded by diffusion-controlled ion-pair [(tetren)CoOH2+,S2O
3
2-
] formation. Replacement of coordinated OH- by S2O
3
2-
is interpreted in terms of an internal conjugate base mechanism: (tetren)CoOH2+ (tetren-H)CoOH
2
2+
, the reactive amido conjugate base being generated by intramolecular proton transfer from the coordinated NH site.In acid medium the S-bonded (tetren)Co(S2O3)+ is highly stable to redox decomposition, in contrast to its pentaammine analogue. The complex however, undergoes base hydrolysis yielding the corresponding hydroxo complex. The rate and activation parameters for the base hydrolysis have been reported. Photolysis of O- and S-bonded isomers of [(tetren)CoS2O3]+ in acidic medium at 254 and 313 nm, respectively, yielded aquation products accompanied by some decomposition of S2O
3
2-
. 相似文献
106.
W. Krakow N. M. Rivera R. A. Roy R. S. Ruoff J. J. Cuomo 《Applied Physics A: Materials Science & Processing》1993,56(3):185-192
Thin films (25-2500 Å) of C60 molecules have been deposited on both (001) NaCl and mica substrates at varying temperatures by resistive evaporation. Both electron diffraction and high resolution microscopy have been used to assess the degree of crystallinity, the orientational ordering and the nature of the defects present in these face-centered-cubic films. For NaCl, optimum conditions yielded polycrystalline films with a tendency towards a 110 orientation, while for mica, extended single crystal films have been fabricated which exhibit a 111 direction normal to the film surface. 相似文献
107.
Atiya MS Chiang IH Frank JS Haggerty JS Ito MM Kycia TF Li KK Littenberg LS Sambamurti A Stevens A Strand RC Louis WC Akerib DS Marlow DR Meyers PD Selen MA Shoemaker FC Smith AJ Blackmore EW Bryman DA Felawka L Kitching P Konaka A Kuno Y Macdonald JA Numao T Padley P Poutissou JM Poutissou R Roy J Soluk R Turcot AS 《Physical review letters》1993,70(17):2521-2524
108.
109.
110.
Syntheses of 5-isopropyl-1,3-cyclohexadiene and syn-5-isopropyl-2,3-dioxabicyclo[2.2.2]octane, by routes that would allow completely diastereoselective introduction of deuterium labels, are described. The reaction of the isopropyl cyclohexadiene with singlet oxygen is shown to give an endoperoxide that is derived by preferential attack on the more sterically hindered face of the diene. A possible mechanistic explanation of this result is that the attack from the less hindered face leads to "ene" reaction rather than endoperoxide formation. However, this mechanism would require that the "ene" reaction and cycloaddition proceed via a common intermediate-presumably a perepoxide. 相似文献