全文获取类型
收费全文 | 19099篇 |
免费 | 3306篇 |
国内免费 | 1697篇 |
专业分类
化学 | 13197篇 |
晶体学 | 181篇 |
力学 | 1053篇 |
综合类 | 67篇 |
数学 | 2032篇 |
物理学 | 7572篇 |
出版年
2024年 | 63篇 |
2023年 | 402篇 |
2022年 | 712篇 |
2021年 | 763篇 |
2020年 | 740篇 |
2019年 | 755篇 |
2018年 | 739篇 |
2017年 | 596篇 |
2016年 | 991篇 |
2015年 | 881篇 |
2014年 | 1097篇 |
2013年 | 1422篇 |
2012年 | 1739篇 |
2011年 | 1768篇 |
2010年 | 1167篇 |
2009年 | 1086篇 |
2008年 | 1197篇 |
2007年 | 1041篇 |
2006年 | 993篇 |
2005年 | 791篇 |
2004年 | 605篇 |
2003年 | 425篇 |
2002年 | 435篇 |
2001年 | 333篇 |
2000年 | 276篇 |
1999年 | 389篇 |
1998年 | 276篇 |
1997年 | 293篇 |
1996年 | 285篇 |
1995年 | 246篇 |
1994年 | 210篇 |
1993年 | 215篇 |
1992年 | 143篇 |
1991年 | 159篇 |
1990年 | 129篇 |
1989年 | 99篇 |
1988年 | 88篇 |
1987年 | 71篇 |
1986年 | 68篇 |
1985年 | 54篇 |
1984年 | 57篇 |
1983年 | 30篇 |
1982年 | 32篇 |
1981年 | 23篇 |
1980年 | 26篇 |
1978年 | 13篇 |
1976年 | 16篇 |
1975年 | 15篇 |
1973年 | 15篇 |
1968年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
241.
纳米碳管电极上氧的电催化还原 总被引:5,自引:0,他引:5
以聚四氟乙烯为粘结剂制成了多壁纳米碳管(MWNT)电极.采用恒电位阶跃法和循环伏安法研究了MWNT电极在碱性溶液中的电化学行为,并对碱性溶液中溶解氧在该电极上的电化学还原行为进行了研究.实验结果表明: MWNT电极具有比石墨电极更高的孔隙率和电化学表面积;MWNT电极上O2还原成的反应为准可逆过程;在5~50 mV•s-1的扫描速率范围内,阴极峰电流与扫描速度成线性关系,表明MWNT电极上O2还原成的反应受吸附控制;对碱性溶液中的氧还原反应, MWNT比石墨具有更高的催化活性. 相似文献
242.
243.
The stability of poly(N-methylaniline) (PNMA) as electrode material has been studied in aqueous solutions of sulfuric acid with the use of electrochemical
and in situ Raman spectroscopic techniques. It has been shown that the electrochemical decomposition of electrodeposited PNMA
films follows a first-order reaction kinetics. The decomposition rate constants vary between 1.2 × 10−5 and 2.0 × 10−3 s−1 for electrode potential varying between 0.2 and 1.0 V vs Ag/AgCl, respectively. In situ Raman spectroscopy has been applied
in obtaining kinetic data at selected electrode potentials, and good correlation of these data with the corresponding data
obtained by cyclic voltammetry has been found. As compared to polyaniline, the decomposition of PNMA proceeds at nearly the
same rate at electrode potentials not exceeding 0.5 V. The decomposition of PNMA proceeds faster within the potential limits
of 0.5 to 0.8 V and slower at electrode potentials exceeding 0.8 V as compared to polyaniline.
This article is dedicated to Professor Algirdas Vaškelis (Institute of Chemistry, Vilnius, Lithuania) on the occasion of his
70th birthday and in honour of his contributions to electrochemistry and physical chemistry. 相似文献
244.
Shenqian Ma Weixin Zhao Jun Zhou Jiaou Wang Shengqi Chu Zigeng Liu Guolei Xiang 《Chemical science》2021,12(12):4411
Noncovalent π stacking of aromatic molecules is a universal form of noncovalent interactions normally occurring on planar structures (such as aromatic molecules and graphene) based on sp2-hybridized atoms. Here we reveal a new type of noncovalent surface–π stacking unusually occurring between aromatic groups and peroxide-modified titania (PMT) nanosheets, which can drive versatile aromatic adsorptions. We experimentally explore the underlying electronic-level origin by probing the perturbed changes of unoccupied Ti 3d states with near-edge X-ray absorption fine structures (NEXAFS), and find that aromatic groups can vertically attract π electrons in the surface peroxo-Ti states and increase their delocalization regions. Our discovery updates the concept of noncovalent π-stacking interactions by extending the substrates from carbon-based structures to a transition metal oxide, and presents an approach to exploit the surface chemistry of nanomaterials based on noncovalent interactions.A new type of noncovalent surface–π stacking interaction occurring on a transition metal oxide, titania, is reported, which is different from the traditional forms on sp2-hybridized planar structures like graphene. 相似文献
245.
Fiaty K Charcosset C Perrin B Couturier R Maïsterrena B 《Journal of computational chemistry》2005,26(3):201-213
Simulations of coupled interactions involving two opposite enzymatic reactions, solute diffusions, and electrostatic interactions between membrane charges and charged solutes were conducted under a fixed kinase-channel-phosphatase (KCP) topology oriented from the outside to the inside of a porous membrane structure. Depending on the kinase and phosphatase locations, we recently demonstrated that an active transport of a phosphorylated substrate may occur via the opposite topology, that is, a PCK topology. The present analysis demonstrates that, under a KCP membrane topology, which also behaves as a specific ATP-dependent transporter, the active transport of a neutral substrate may occur. This analogous active transport appears to be dependent on the phosphatase location and on the membrane surface potentials. A broad analysis of the role played by the main parameters taken into account in the model was conducted in order to define precisely the physico-chemical conditions and the membrane topology needed for the highest active transports within the shortest time. 相似文献
246.
247.
248.
C. M. Lerner Y. P. Ma J. S. Brooks R. Messervey P. Tedrow 《Applied Physics A: Materials Science & Processing》1991,52(6):433-437
The longitudinal and transverse magnetoresistance to fields of 19 Tesla and 4.2 K has been measured for bismuth films ranging in thickness from 0.01 to 2 m. We have observed a pronounced maximum in the longitudinal magnetoresistance which is thickness dependent. We compare these results with classical size effect theories for the longitudinal magnetoresistance in terms of magnetic-field-dependent electron scattering at grain and film boundaries. Measurements of the longitudinal magnetoresistance to 38 Tesla show a quenching of the classical size effect in the high field limit. This result strongly supports our analysis.Work supported by NSF grant #DMR 8113456Supported by the National Science Foundation 相似文献
249.
250.