全文获取类型
收费全文 | 3460篇 |
免费 | 84篇 |
国内免费 | 393篇 |
专业分类
化学 | 3059篇 |
晶体学 | 48篇 |
力学 | 21篇 |
综合类 | 1篇 |
数学 | 6篇 |
物理学 | 802篇 |
出版年
2024年 | 17篇 |
2023年 | 406篇 |
2022年 | 106篇 |
2021年 | 128篇 |
2020年 | 130篇 |
2019年 | 119篇 |
2018年 | 87篇 |
2017年 | 94篇 |
2016年 | 135篇 |
2015年 | 108篇 |
2014年 | 187篇 |
2013年 | 177篇 |
2012年 | 179篇 |
2011年 | 183篇 |
2010年 | 175篇 |
2009年 | 197篇 |
2008年 | 156篇 |
2007年 | 209篇 |
2006年 | 163篇 |
2005年 | 149篇 |
2004年 | 136篇 |
2003年 | 70篇 |
2002年 | 72篇 |
2001年 | 75篇 |
2000年 | 49篇 |
1999年 | 54篇 |
1998年 | 46篇 |
1997年 | 47篇 |
1996年 | 32篇 |
1995年 | 30篇 |
1994年 | 26篇 |
1993年 | 28篇 |
1992年 | 19篇 |
1991年 | 21篇 |
1990年 | 22篇 |
1989年 | 13篇 |
1988年 | 31篇 |
1987年 | 9篇 |
1986年 | 8篇 |
1985年 | 3篇 |
1984年 | 7篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 7篇 |
1980年 | 4篇 |
1979年 | 6篇 |
1978年 | 5篇 |
1977年 | 2篇 |
1976年 | 3篇 |
1974年 | 2篇 |
排序方式: 共有3937条查询结果,搜索用时 78 毫秒
901.
The possibility of the use of Klason lignin extracted from sunflower husks as a cathode-active material for primary lithium battery has been demonstrated for the first time. The chemical composition, morphological and physical features were characterized by X-ray energy dispersive spectroscopy, impedance spectroscopy, scanning electron microscopy, and infrared spectroscopy. Electrochemical behavior of Klason lignin vs. Li/Li+ was studied by galvanostatic discharge and cyclic voltammetry. The reaction mechanism in electrochemical system was discussed. The maximum specific capacity of Klason lignin amounted to 380 mAh g–1 at a current density of 25 mA g–1. 相似文献
902.
《中国化学会会志》2017,64(3):246-249
Calcareous crystallites with chiral morphology are difficult to obtain in vitro . Using the d ‐form of aspartic acid as crystal modifier, calcium carbonate with chiral morphology has been obtained in agarose gel. We show that the formation of the chiral morphology of crystallites does not necessarily involve complicated cellular processes. 相似文献
903.
904.
Organic light-emitting diode performance enhancement via indium tin oxide glass surface modification 总被引:1,自引:0,他引:1
A self-assembly monolayer (SAM), with phenyl-triethoxysilane (PTES), was used to modify the indium tin oxide anode for an organic light-emitting diode (OLED) in order to improve the OLED performance. The enhancement of OLED performance is attributed to the blockage of excessive hole injection by PTES, balancing the hole and electron injection numbers. The result indicates that the SAM process reaction time duration greatly affects the OLED performance outcomes. If the reaction time is too long, it will impact on the optical efficiency due to molecular aggregates accumulated on the SAM layers, thus reducing the performance of the OLEDs. The electrical and optical characteristics of the OLEDs are modeled by using the modified Shockley equation. Modified Shockley parameters are extracted to interpret the experimental data with excellent accuracy. Those parameters, both electrical and optical, can be used as the DC level modeling parameters for OLED product design simulations. 相似文献
905.
906.
E. de la Rosa-Cruz C. W. Dirk O. RodrÍguez V. M. CastaÑo 《Fiber and Integrated Optics》2013,32(5):457-464
The impact of a post-OTDM-demultiplexing optical filter on the performance of dense on-off keying (OOK) optical time division multiplexing (OTDM)—wavelength division multiplexing (WDM) systems was studied. For return-to-zero (RZ) modulation, it was found that the additional filter working in a double-tier filter configuration did not offer any significant improvements to performance when the signal pulse width is optimized. Improvements generally increase only when the signal pulse width deviates from its optimal value and only for low spectral densities. For ideal non-return-to-zero (NRZ) modulation, however, significant improvements of around 1 dB are obtained using the double-tier configuration over a large range of spectral densities. 相似文献
907.
Lipases were found to catalyze Cannizzaro-type reaction of substituted benzaldehydes in aqueous medium at 30 °C without the addition of any external redox reagent. The ratio of alcohol product to acid product varied with nature of the substituted benzaldehyde, enzyme, and the presence of organic co-solvent. 相似文献
908.
ABSTRACT The role of di-cumyl peroxide (DCP) as compatibilizer in low density Polyethylene/Polypropylene (LDPE/PP) blends has been explored. Mixtures with varying LDPE/PP ratio were prepared in a Brabender plasticorder and tested for their mechanical properties and calorimetric response. Then peroxide was added at concentrations up to 0.5%, and the mechanical properties of the these new blends were measured. Also, the mixing torque, melt flow index and gel content of the above products were recorded as a function of peroxide concentration. It was found that the incorporation of DCP restricts the thermoplastic characteristics of the melt, which was primarily attributed to branching which occurs in LDPE. This results in an enhancement in the adhesive bonding between the two polymers mainly due to chain entanglements. This was further supported by the fact that mechanical properties of the treated blend were significantly improved. 相似文献
909.
A.T. Myller 《Applied Surface Science》2010,257(5):1616-1622
Titanium dioxide (TiO2) powder was chemically modified with 2-aminoethyl dihydrogen phosphate (AEPH2) and with 2-aminoethyl hydrogen ammonium phosphate (AEPHNH4) in order to achieve an aminofunctionalized high-surface-area TiO2 carrier suitable for more complex functionalizing. AEPH2 was found to form the monoammonium salt AEPHNH4 with ammonium ion rather than the diammonium salt AEP(NH4)2. The AEPHNH4 was thoroughly characterized by various techniques and compared with AEPH2. Bonding of AEPH2 and AEPHNH4 with TiO2 powder was studied. According to the 31P NMR and elemental analysis results, AEPH2 and AEPHNH4 form covalent chelate bidentate bonds between the phosphate group and the TiO2, while the amino groups remain accessible, creating uniform aminofunctionalized TiO2 surface fully occupied by AEP groups. Amount of AEP groups on TiO2 was limited to 1.5 wt-%. 相似文献
910.
以钼酸钠、L-半胱氨酸和氧化石墨烯为原料,采用一锅溶剂热还原法制备了二硫化钼量子点/还原氧化石墨烯(MoS2 QDs/rGO)复合材料,分别以罗丹明B、亚甲基蓝、四环素和Cr(VI)为目标污染物,研究了复合材料的可见光响应光催化降解性能。结果显示,MoS2 QDs/rGO对两种染料和Cr(VI)的光催化降解率均可达97%以上,对四环素的光催化降解率为69%;循环使用10次,对目标染料的降解率均保持在90%以上。说明MoS2 QDs/rGO具有良好的催化活性和稳定性。在降解体系中分别加入异丙醇、对苯醌和乙二胺四乙酸二钠捕获剂,结果显示,超氧自由基(?O2-)是MoS2 QDs/rGO光催化反应的主要活性物种。 相似文献