全文获取类型
收费全文 | 5214篇 |
免费 | 252篇 |
国内免费 | 138篇 |
专业分类
化学 | 3438篇 |
晶体学 | 28篇 |
力学 | 258篇 |
综合类 | 11篇 |
数学 | 880篇 |
物理学 | 989篇 |
出版年
2023年 | 45篇 |
2022年 | 127篇 |
2021年 | 176篇 |
2020年 | 139篇 |
2019年 | 126篇 |
2018年 | 107篇 |
2017年 | 120篇 |
2016年 | 214篇 |
2015年 | 185篇 |
2014年 | 174篇 |
2013年 | 287篇 |
2012年 | 302篇 |
2011年 | 333篇 |
2010年 | 221篇 |
2009年 | 200篇 |
2008年 | 333篇 |
2007年 | 316篇 |
2006年 | 262篇 |
2005年 | 269篇 |
2004年 | 197篇 |
2003年 | 197篇 |
2002年 | 149篇 |
2001年 | 68篇 |
2000年 | 74篇 |
1999年 | 54篇 |
1998年 | 46篇 |
1997年 | 38篇 |
1996年 | 63篇 |
1995年 | 53篇 |
1994年 | 43篇 |
1993年 | 38篇 |
1992年 | 28篇 |
1991年 | 29篇 |
1990年 | 32篇 |
1989年 | 32篇 |
1988年 | 32篇 |
1987年 | 42篇 |
1986年 | 24篇 |
1985年 | 43篇 |
1984年 | 39篇 |
1983年 | 19篇 |
1982年 | 25篇 |
1981年 | 26篇 |
1980年 | 29篇 |
1979年 | 20篇 |
1978年 | 16篇 |
1977年 | 28篇 |
1975年 | 14篇 |
1974年 | 13篇 |
1858年 | 11篇 |
排序方式: 共有5604条查询结果,搜索用时 421 毫秒
81.
3 D-QSAR Analysis of Agonists of nAChRs: Epibatidine Analogues 总被引:1,自引:0,他引:1
HuaBeiZHANG ChunPingLIU 《中国化学快报》2004,15(11):1380-1382
A 3 D-QSAR about nAChRs agonists epibatidine analogues was performed using theCoMFA and CoMSIA. The correlation coefficients were R2cv = 0.546, R2cv = 0.907 in CoMFA andR2cv = 0.655, R2,~ = 0.962 in CoMSIA of the final model. The prediction using the final models tothe test set was r2 = 0.675 in CoMFA and r2 = 0.462 in CoMSIA. This model will be useful in thedesign of novel compounds with high affinity. 相似文献
82.
用TRP技术研究了以全硅MCM-41(Si-MCM-41)和HNO3交换的全硅MCM-41(H-MCM-41)为载体制备的Ni-Mo、Co-Mo和Ni-W加氢脱硫(HDS)催化剂的还原性能,并以0.8(wt)%二苯并噻吩(DBT)的十氢萘溶液为模型化合物,在高压固定床反应器上考察了上述催化剂的加氢脱硫(HDS)反应性能。结果表明,Si-MCM-41经稀HNO3交换后,所担载的Ni-Mo和Ni-W催化剂还原性能、HDS活性和加氢活性有显著变化,但对Co-Mo催化剂影响不大。这说明在Ni-Mo/H-MCM-41和Ni-W/H-MCM-41中可能存在氢溢流现象,DBT的HDS活性与载体表面酸性和氢溢流有关。 相似文献
83.
A convenient route to new 3-quinolinonyl-pyrazoles and isoxazoles is described through cyclization of 3-[(E)-3-(dimethylamino)-2-propenoyl]-4-hydroxy-1-methyl-2(1H)-quinolinone. The phototoxicity as well as the cytotoxic activities of the title compounds are evaluated against leukemia- and adenocarcinoma-derived cell lines in comparison to the normal human keratinocytes. 相似文献
84.
Carlo Bruno Eleonora Ussano Gianni Barucca Davide Vanossi Giovanni Valenti Edward A. Jackson Andrea Goldoni Lucio Litti Simona Fermani Luca Pasquali Moreno Meneghetti Claudio Fontanesi Lawrence T. Scott Francesco Paolucci Massimo Marcaccio 《Chemical science》2021,12(23):8048
The presence of non-hexagonal rings in the honeycomb carbon arrangement of graphene produces rippled graphene layers with valuable chemical and physical properties. In principle, a bottom-up approach to introducing distortion from planarity of a graphene sheet can be achieved by careful insertion of curved polyaromatic hydrocarbons during the growth of the lattice. Corannulene, the archetype of such non-planar polyaromatic hydrocarbons, can act as an ideal wrinkling motif in 2D carbon nanostructures. Herein we report an electrochemical bottom-up method to obtain egg-box shaped nanographene structures through a polycondensation of corannulene that produces a new conducting layered material. Characterization of this new polymeric material by electrochemistry, spectroscopy, electron microscopy (SEM and TEM), scanning probe microscopy, and laser desorption-ionization time of flight mass spectrometry provides strong evidence that the anodic polymerization of corannulene, combined with electrochemically induced oxidative cyclodehydrogenations (Scholl reactions), leads to polycorannulene with a wavy graphene-like structure.A bottom-up synthesis of wavy graphene structures obtained through an anodic polymerization process, combined with an electrochemically triggered oxidative cyclodehydrogenation, of the bowl-shaped polyaromatic hydrocarbon corannulene. 相似文献
85.
Giovannelli Tommaso Liuzzi Giampaolo Lucidi Stefano Rinaldi Francesco 《Computational Optimization and Applications》2022,82(2):293-327
Computational Optimization and Applications - In this paper, mixed-integer nonsmooth constrained optimization problems are considered, where objective/constraint functions are available only as the... 相似文献
86.
Francesco Cubadda 《Russian Chemical Bulletin》1995,44(2):388-390
Information Congresses, Conferences, Symposia, Workshops, and Seminars in the Field of Chemical Sciences held with Participation of the Russian Academy of Sciences
The XXXV International IUPAC Symposium on macromolecular chemistry (MACROACRON-94) 相似文献87.
Summary We consider a (possibly) vector-valued function u: RN, Rn, minimizing the integral
, 2-2/(n*1)<p<2, whereD
i
u=u/x
i
or some more general functional retaining the same behaviour, we prove higher integrability for Du: D1 u,..., Dn–1 u Lp/(p-1) and Dnu L2; this result allows us to get existence of second weak derivatives: D(D1 u),...,D(Dn–1u)L2 and D(Dn u) L
p.This work has been supported by MURST and GNAFA-CNR. 相似文献
88.
89.
90.