全文获取类型
收费全文 | 304篇 |
免费 | 16篇 |
专业分类
化学 | 232篇 |
晶体学 | 6篇 |
力学 | 12篇 |
数学 | 25篇 |
物理学 | 45篇 |
出版年
2022年 | 3篇 |
2021年 | 5篇 |
2020年 | 4篇 |
2019年 | 11篇 |
2018年 | 3篇 |
2017年 | 8篇 |
2016年 | 6篇 |
2015年 | 8篇 |
2014年 | 11篇 |
2013年 | 19篇 |
2012年 | 14篇 |
2011年 | 21篇 |
2010年 | 10篇 |
2009年 | 7篇 |
2008年 | 21篇 |
2007年 | 16篇 |
2006年 | 14篇 |
2005年 | 17篇 |
2004年 | 11篇 |
2003年 | 5篇 |
2002年 | 15篇 |
2001年 | 5篇 |
2000年 | 3篇 |
1999年 | 3篇 |
1998年 | 3篇 |
1997年 | 3篇 |
1996年 | 5篇 |
1995年 | 5篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1990年 | 4篇 |
1988年 | 5篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1980年 | 3篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1974年 | 3篇 |
1972年 | 2篇 |
1970年 | 2篇 |
1969年 | 1篇 |
1962年 | 1篇 |
1961年 | 3篇 |
1937年 | 2篇 |
1900年 | 2篇 |
排序方式: 共有320条查询结果,搜索用时 15 毫秒
1.
John P. Dirlam Richard B. James Eleanor V. Shoop 《Journal of heterocyclic chemistry》1980,17(2):409-411
The preparation of 5H,10H-diimidazo[1,2-a:1′,2′-d]pyrazine-5,10-dione ( 2a ) and its 2,3,7,8-tetrabromo- and 2,3,7,8-tetrachloro- analogs ( 2b and 2c , respectively) is reported. These dimers, when allowed to react with various anilines, afford imidazole-2-carboxamides ( 3a-c ). 相似文献
2.
H. M. Fretwell J. A. Duffy M. A. Alam R. Evans 《Journal of Radioanalytical and Nuclear Chemistry》1996,210(2):575-582
In this paper we present our recent positron annihilation study of the liquid»solid phase boundary for CO2 confined in nanometer pores of VYCOR glass. We find that CO2 remains liquid in the pores far below the bulk freezing temperature and there is pronounced hysteresis between freezing and melting compared to that seen at the gas-liquid boundary in the pores. On freezing we see evidence of open space created in the pores. This leads to complex melting behaviour possibly involving the formation of gas-liquid interfaces. We see that frezing in the pores is totally irreversible, so that any solid which forms (no matter how small) remains stable up to the higher melting temperature. In contrast melting is more reversible (possibly indicating nucleation centres which permit immediate re-freezing). Finally, the pre-frozen state in the pores is different to the post-melted state. 相似文献
3.
Bianconi PA Joray SJ Aldrich BL Sumranjit J Duffy DJ Long DP Lazorcik JL Raboin L Kearns JK Smulligan SL Babyak JM 《Journal of the American Chemical Society》2004,126(10):3191-3202
The synthesis of poly(hydridocarbyne), one of a class of carbon-based random network polymers and a structural isomer of polyacetlyene, is reported. The network backbone of this polymer is primarily composed of tetrahedrally hybridized carbon atoms, each bearing one hydride substituent and linked via three carbon-carbon single bonds into a three-dimensional random network of fused rings. This atomic-level carbon network backbone confers unusual properties on the polymer, including facile thermal decomposition to form diamond or diamond-like carbon high-quality films at atmospheric pressure, by direct deposition or by chemical vapor deposition (CVD), without the use of hydrogen or any other reagent. 相似文献
4.
Wolfgang Dietzsch Norman V. Duffy Aaron M. Lee Brian W. Skelton Allan H. White 《无机化学与普通化学杂志》2006,632(15):2419-2423
The consequences of replacement of the symmetrically chelate ligands in [M(E2CNR2)3] (E = S, Se) complexes of potential 32 symmetry by analogous mixed S,Se unsymmetrical chelates are explored for both small (M = Co) and large (M = In) metal atoms, and R = primary (Et) and secondary (iPr) alkyl substituents by way of low‐temperature single crystal X‐ray studies of [(Co(SSeCNEt2)3] ([Co(Se2CNEt2)3] also determined as datum), and [In(SSeCNR2)3], R = Et, iPr. The structure of [(iPr2N·CS·Se)2] is also recorded. 相似文献
5.
6.
J. A. Duffy H. M. Fretwell A. P. Clarke S. B. Dugdale M. A. Alam 《Journal of Radioanalytical and Nuclear Chemistry》1996,211(1):173-179
The phase behaviour of carbon dioxide confined in VYCOR glass at pressures below that of the bulk triple point (0.51 MPa) has been investigated. The temperature at which freezing occurs appears to be pressure dependent below 0.3 MPa. As experiments are performed at successively lower pressures, the confined phase transitions gradually disappear, due to either partial pore filling, or the proximity of the confined triple point. 相似文献
7.
M. A. Alam H. M. Fretwell J. A. Duffy A. P. Clarke S. B. Dugdale 《Journal of Radioanalytical and Nuclear Chemistry》1996,210(2):255-271
In this paper we present a brief review of the current state of positron annihilation research into the phase behaviour of fluids confined within restricted boundaries. We summarise, in the form of selected examples, the work done so far on: (1) fluids confined in the nanometer-size pores of VYCOR glass, with particular emphasis on the confined phase diagram and the mechanisms behind phase transitions compared to bulk. (2) The adsorption/physisorption of gases on internal surfaces of grafoil and the potential of positron technique for revealing physical properties, such as the intricate molecular arrangements during phase transitions of the layered fluid. 相似文献
8.
RU Chang Bi Zbigniew Dauter Eleanor Dodson Guy Dodson Federico Gordiano Rod Hubbard Colin Reynolds 《Journal of Chemical Sciences》1983,92(4-5):473-483
Insulin modified by the removal of its 5 B chain C terminal residues is monomeric but remains substantially potent. The crystal
structures of the beef and insulin (dpi) with two molecules in the asymmetric unit has been determined by x-ray analysis. The 3-dimensional structure ofdpi proves to be generally similar to that of native molecule in 2Zn insulin. More detailed comparison reveals that the slight
differences in the two independent molecules of beefdpi are distributed uniformly throughout the structure in contrast to insulin in 2Zn insulin, where the structural changes are
concentrated in specific regions.
The loss of symmetry in thedpi crystal appears to be the inability of the A9 serine to pack effectively in the C2 cell. The efficient packing of the sheepdpi molecule whose crystal structure has also been determined and where A9 is glycine supports this conclusion. 相似文献
9.
10.