全文获取类型
收费全文 | 13860篇 |
免费 | 1400篇 |
国内免费 | 1033篇 |
专业分类
化学 | 10400篇 |
晶体学 | 168篇 |
力学 | 279篇 |
综合类 | 53篇 |
数学 | 141篇 |
物理学 | 5252篇 |
出版年
2024年 | 20篇 |
2023年 | 135篇 |
2022年 | 244篇 |
2021年 | 257篇 |
2020年 | 298篇 |
2019年 | 248篇 |
2018年 | 256篇 |
2017年 | 352篇 |
2016年 | 441篇 |
2015年 | 457篇 |
2014年 | 486篇 |
2013年 | 858篇 |
2012年 | 867篇 |
2011年 | 805篇 |
2010年 | 669篇 |
2009年 | 834篇 |
2008年 | 744篇 |
2007年 | 929篇 |
2006年 | 705篇 |
2005年 | 666篇 |
2004年 | 597篇 |
2003年 | 529篇 |
2002年 | 423篇 |
2001年 | 342篇 |
2000年 | 336篇 |
1999年 | 331篇 |
1998年 | 286篇 |
1997年 | 310篇 |
1996年 | 284篇 |
1995年 | 231篇 |
1994年 | 226篇 |
1993年 | 215篇 |
1992年 | 154篇 |
1991年 | 166篇 |
1990年 | 110篇 |
1989年 | 122篇 |
1988年 | 137篇 |
1987年 | 113篇 |
1986年 | 115篇 |
1985年 | 133篇 |
1984年 | 137篇 |
1983年 | 78篇 |
1982年 | 127篇 |
1981年 | 120篇 |
1980年 | 109篇 |
1979年 | 120篇 |
1978年 | 75篇 |
1977年 | 18篇 |
1976年 | 28篇 |
1973年 | 23篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
利用多靶磁控溅射技术制备了Au/SiO2纳米颗粒分散氧化物多层复合薄膜.研究了在保持Au单层颗粒膜沉积时间一定时薄膜厚度一定、变化SiO2的沉积时间及SiO2的沉积时间一定而改变薄膜厚度时,多层薄膜在薄膜厚度方向的微观结构对吸收光谱的影响.研究结果表明:具有纳米层状结构的Au/SiO2多层薄膜在560 nm波长附近有明显的表面等离子共振吸收峰,吸收峰的强度随Au颗粒的浓度增加而增强,在Au颗粒浓度相同的情况下,复合薄膜
关键词:
2纳米复合薄膜')" href="#">Au/SiO2纳米复合薄膜
多靶磁控溅射
吸收光谱
有效介质理论 相似文献
72.
Very weak water vapor absorption lines have been investigated by intracavity laser absorption spectroscopy (ICLAS) in the 11 335-11 947 and 12 336-12 843 cm−1 spectral regions dominated by the ν1 + 3ν2 + ν3 and ν2 + 3ν3 bands, respectively. A detectivity on the order of αmin ∼ 10−9 cm−1 was achieved with an ICLAS spectrometer based on a Ti: Sapphire laser. It allowed detecting transitions with an intensity down to 5 × 10−28 cm/molecule which is about 10 times lower than the weakest line intensities previously detected in the considered region. A line list corresponding to 1281 transitions with intensity lower than 5 × 10−26 cm/molecule has been generated. A detailed comparison with the line lists provided by the HITRAN database and by recent investigations by Fourier transform spectroscopy associated with very long multi pass cell is presented. The rovibrational assignment performed on the basis of the ab initio calculations of Schwenke and Partridge, has allowed for determining 176 new energy levels belonging to a total of 16 vibrational states. 相似文献
73.
Jun Hua YU Xue Song WANG Bao Wen ZHANG* Yi CAO Technical Institute of Physics Chemistry Chinese Academy of Sciences Beijing 《中国化学快报》2002,13(10)
Porphyrin derivatives attract much more interest in photodynamic therapy (PDT). Their importance as therapeutic drugs and targeting agents has been widely recognized1, and many of the efforts have been put towards crafting new porphyrin-based molecular entities to achieve enhanced tumor localization, better tissue penetration and increased singlet oxygen quantum yield2. The states of porphyrins in tissue models such as micelles, lipid bilayers are extensively investigated focusing more or l… 相似文献
74.
Two methods for sampling and concentration of volatile organic compounds are reported. In the first method, traps coated with a very thick film (ca. 100 μm) of cross-linked silicone stationary phase are employed. Such thick films can be prepared with a modified dynamic coating procedure, which is briefly described. The low phase ratio traps can be utilized for enrichment of volatiles from gaseous as well as aqueous matrices. The second technique is based on chromatographic evaporation of a solvent in a capillary tube, where the process is sustained by a repeated sample injection and a cyclic flow reversal. In this way, large solvent volumes can be handled by a small volume system. Under optimal conditions, when using a solvent barrier, quantitative recovery is possible even for compounds of comparatively high volatility. Another important application of the technique is extraction of trace components from gases such as headspace samples, polluted air, etc. 相似文献
75.
研究了LaB6在1~10 Pa氮气和氦气中的直流和脉冲放电特性以及放电过程对电极的影响。结果表明,电极直径为5 mm的LaB6氦气放电管在脉冲工作状态下可以长期稳定放电。在脉冲电压为2.2 kV、脉冲宽度10 ms、频率13.3 Hz下,脉冲峰值放电电流超过120 A。氦气放电管在放电过程中,阴极表面有离子的清洗和活化作用,可以使电极的表面逸出功降低,提高放电管的发射能力和稳定性。LaB6作为气体放电电极具有寿命长、延迟时间短、放电电流大等优点,可用于重复强流脉冲气体放电的高压高速开关器件。 相似文献
76.
根据热力学第一定律和理想气体状态方程推导了理想气体的热容量公式,并对理想气体在p-V图上的直线过程和循环过程的温度变化及吸热和放热进行了讨论. 相似文献
77.
78.
Jaime Pfretzschner Pedro Cobo Francisco Simón María Cuesta Alejandro Fernández 《Applied Acoustics》2006,67(1):62-73
Microperforated panels (MPPs) coupled to a rigid wall have been proposed recently as an alternative to porous absorbers in situations having concerns with bacterial contamination and small particles discharge, like food, pharmaceutical and microelectronic industries. There exists also an increasing interest for MPP absorbers in the transportation industry and civil engineering. In general, an optimally designed MPP with good broadband absorption requires many submillimetric holes distributed over a panel of also submillimetric thickness. Such thin plates or foils become so fragile that they need to be protected from mechanical damage. In this paper, an alternative strategy is investigated which allows the design of MPPs with panels of millimetric thickness while maintaining their acoustic performance. These absorbers, named microperforated insertion units (MIUs), avoid the structural problems of the classical MPPs. An assessment of the sound absorption properties of these structures is presented. Comparisons between calculations and measurements are also made under two experimental conditions: plane waves at normal incidence (impedance tube) and free field (anechoic room). 相似文献
79.
80.