全文获取类型
收费全文 | 419251篇 |
免费 | 7208篇 |
国内免费 | 4949篇 |
专业分类
化学 | 191171篇 |
晶体学 | 5999篇 |
力学 | 26209篇 |
综合类 | 325篇 |
数学 | 69533篇 |
物理学 | 138171篇 |
出版年
2021年 | 4610篇 |
2020年 | 5142篇 |
2019年 | 5924篇 |
2018年 | 13232篇 |
2017年 | 13475篇 |
2016年 | 12626篇 |
2015年 | 5795篇 |
2014年 | 9332篇 |
2013年 | 15529篇 |
2012年 | 16644篇 |
2011年 | 23680篇 |
2010年 | 17175篇 |
2009年 | 17487篇 |
2008年 | 21334篇 |
2007年 | 23343篇 |
2006年 | 12693篇 |
2005年 | 14242篇 |
2004年 | 11985篇 |
2003年 | 11670篇 |
2002年 | 10809篇 |
2001年 | 9321篇 |
2000年 | 7581篇 |
1999年 | 5639篇 |
1998年 | 5309篇 |
1997年 | 4979篇 |
1996年 | 4741篇 |
1995年 | 4112篇 |
1994年 | 4193篇 |
1993年 | 4162篇 |
1992年 | 4072篇 |
1991年 | 4480篇 |
1990年 | 4465篇 |
1989年 | 4401篇 |
1988年 | 4126篇 |
1987年 | 4173篇 |
1986年 | 3832篇 |
1985年 | 4405篇 |
1984年 | 4627篇 |
1983年 | 3992篇 |
1982年 | 4154篇 |
1981年 | 3797篇 |
1980年 | 3550篇 |
1979年 | 4109篇 |
1978年 | 4196篇 |
1977年 | 4237篇 |
1976年 | 4433篇 |
1975年 | 4113篇 |
1974年 | 4014篇 |
1973年 | 4177篇 |
1972年 | 3584篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
992.
研究了多壁碳纳米管(MWNTs)薄膜的湿敏特性,实验所用的多壁碳纳米管是用热灯丝化学气相沉积法(CVD)合成的.分别对未修饰和修饰的多壁碳纳米管膜温度和湿度特性进行研究后发现,修饰的多壁碳纳米管对温度和湿度非常敏感,且对湿度的响应时间和恢复时间短,重复性好.而未修饰的多壁碳纳米管对温度和湿度不太敏感.对修饰多壁碳纳米管的湿敏特性进行了理论分析,给出了其理论表示式.
关键词:
多壁碳纳米管
化学修饰
湿敏特性
物理吸附 相似文献
993.
以PCl3为脱水剂,将邻氨基硫酚与水杨酸脱水环化合成出2-(2-羟基苯基)苯并噻唑,并进一步将所得产物与乙酸锌反应合成出2-(2-羟基苯基)苯并噻唑螯合锌(Zn(BTZ)2)材料。以该配合物作为发光层制备出结构为ITO/PVK:TPD/Zn(BTZ)2/Al近白色电致发光器件,其色坐标位于白场之内(x=0.242,y=0.359),在驱动电压为16V时,亮度达3200cdm2,对应的量子效率为0.32%。进一步在Zn(BTZ)2中掺入橙红色染料Rubrene,制成ITO/PVK:TPD/Zn(BTZ)2:Rubrene/Al结构器件,实现了纯白色发光(色坐标值:x=0.324,y=0.343),非常接近于白色等能点,且量子效率达0.47%。最后对上述器件的发光和电学性能进行了深入的研究和探讨。 相似文献
994.
EQCM and voltammetric data show that thallium(I) ions, which are adsorbed in the region of the positive surface charge, most probably, in the form of the ionic pairs, are not reduced. In this potential region, thallium(I) ions are reduced directly from the solution. At more negative potentials, the previously adsorbed stable ionic pairs slowly undergo transition into the less stable form. From this form, thallium(I) ions can be reduced or desorbed into the solution. The process is best described by a model of one electron, i.e., full charge transfer. 相似文献
995.
Andreev V. N. Kolyadko E. A. Podlovchenko B. I. 《Russian Journal of Electrochemistry》2004,40(5):580-583
Radioactive tracer studies confirm the earlier electrochemical results that carbon monoxide can virtually completely displace iodine adatoms. For the first time, it is found that iodine adatoms are not displaced by carbon monoxide when iodide anions are adsorbed in the presence of an upd silver monolayer. The possible reasons for the effect observed are discussed. 相似文献
996.
Two-Layered Poly-o-phenylenediamine/Polyaniline Composite: Electrosynthesis and Spectroelectrochemical Properties 总被引:1,自引:0,他引:1
E. Yu. Pisarevskaya E. V. Ovsyannikova N. M. Alpatova 《Russian Journal of Electrochemistry》2004,40(9):969-976
Spectroelectrochemical properties of poly-o-phenylenediamine (PPD) and the synthesized composite of PPD and polyaniline—two chemically related polymers containing an amino-substituted benzene ring but having different conduction nature—are studied. The polyaniline synthesis on PPD-modified electrodes involves stages of the reaction initiation, the copolymer formation, and the formation of a polyaniline layer at the copolymer/solution interface. 相似文献
997.
Data on the adsorption of kryptates of alkali metals on a mercury electrode are obtained for the first time by a method of the measurement of the differential capacitance as a function of potential and are compared to one another. Shown is that there takes place a deep mutual relationship between the structure of a complex and the regularities of its adsorption. An assumption is put forth about the possibility of adsorption of a free ligand in solutions of lithium kryptate, which possesses relatively low strength. The co-adsorption of sodium kryptate with 1-adamantanol, which forms a two-dimensional condensed layer, is investigated. Established is that the C vs. E curves, obtained in 1 M Na2SO4 at a constant activity of 1-adamantanol and a varying concentration of KryptofixR 222, exhibit two distinctly pronounced portions, each of which corresponds to predominant adsorption of one of the surface-active components. The region of predominant adsorption of KryptofixR 222 expands with its concentration. 相似文献
998.
The dynamic and equilibrium surface tensions of aqueous dodecylamidoethyldimethylbenzylammonium chloride solutions of various concentrations at 16, 20, 25, 30, and 35°C are studied for the first time. The effects of the concentration and temperature on the surface tension relaxation are discussed. The possibility of two-dimensional phase transition and its effect on the dynamic behavior of surface tension are considered. 相似文献
999.
M. A. Proskurnin N. V. Orlova A. V. Pikhtar' N. V. Osipova 《Journal of Analytical Chemistry》2004,59(5):433-437
Conditions are determined for the determination of salicylhydroxamic and acetylhydroxamic acids by thermal-lens spectrometry using iron(III) in an aqueous medium. The detection limits are 6 × 10–8 and 3 × 10–8 M, respectively. The sensitivity can be enhanced 3–6 times with the use of aqueous–organic media. 相似文献
1000.
D. V. Batov 《Colloid Journal》2004,66(1):109-112
The solution enthalpies of water–n-octane–1-pentanol (PenOH)–sodium dodecyl sulfate (SDS) microemulsions and their components in 2-propanol at 298.15 K were determined by the thermochemical method at fixed mass fractions of PenOH (0.1450) and SDS (0.0775). The formation enthalpies of microemulsions were calculated using the thermochemical cycle, and it was shown that their values are positive. The results obtained indicate that the intercomponent interactions in the investigated systems are rather weak. The formation of thermodynamically stable microemulsions is determined by entropy changes associated with the disintegration of water and 1-pentanol homoassociates. 相似文献