全文获取类型
收费全文 | 14290篇 |
免费 | 2433篇 |
国内免费 | 2178篇 |
专业分类
化学 | 11685篇 |
晶体学 | 201篇 |
力学 | 688篇 |
综合类 | 176篇 |
数学 | 1494篇 |
物理学 | 4657篇 |
出版年
2024年 | 17篇 |
2023年 | 188篇 |
2022年 | 287篇 |
2021年 | 362篇 |
2020年 | 516篇 |
2019年 | 557篇 |
2018年 | 428篇 |
2017年 | 367篇 |
2016年 | 712篇 |
2015年 | 707篇 |
2014年 | 842篇 |
2013年 | 1029篇 |
2012年 | 1180篇 |
2011年 | 1318篇 |
2010年 | 953篇 |
2009年 | 953篇 |
2008年 | 1142篇 |
2007年 | 952篇 |
2006年 | 916篇 |
2005年 | 766篇 |
2004年 | 673篇 |
2003年 | 583篇 |
2002年 | 705篇 |
2001年 | 534篇 |
2000年 | 451篇 |
1999年 | 310篇 |
1998年 | 207篇 |
1997年 | 160篇 |
1996年 | 177篇 |
1995年 | 145篇 |
1994年 | 127篇 |
1993年 | 106篇 |
1992年 | 75篇 |
1991年 | 89篇 |
1990年 | 46篇 |
1989年 | 38篇 |
1988年 | 35篇 |
1987年 | 33篇 |
1986年 | 26篇 |
1985年 | 28篇 |
1984年 | 23篇 |
1983年 | 19篇 |
1982年 | 11篇 |
1981年 | 21篇 |
1980年 | 11篇 |
1979年 | 16篇 |
1978年 | 8篇 |
1977年 | 10篇 |
1974年 | 12篇 |
1973年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 359 毫秒
41.
Q.-Y. Shao A.-D. Li J.-B. Cheng H.-Q. Ling D. Wu Z.-G. Liu N.-B. Ming C. Wang H.-W. Zhou B.-Y. Nguyen 《Applied Physics A: Materials Science & Processing》2005,81(6):1181-1185
LaAlO3 (LAO) gate dielectric films were deposited on Si substrates by low-pressure metalorganic chemical vapor deposition. The interfacial structure and composition distribution were investigated by high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), secondary-ion mass spectroscopy (SIMS), and Auger-electron spectroscopy (AES). HRTEM confirms that there exists an interfacial layer between LAO and Si in most samples. AES, SIMS, and XPS analyses indicate that the interfacial layer is compositionally graded La–Al silicate and the Al element is severely deficient close to the Si surface. Electrical properties of LAO films were evaluated. No evident difference in electrical properties between samples with and without native SiO2 layers was observed. The electrical properties are discussed in terms of LAO growth mechanisms, in relation to the interfacial structure. PACS 73.40.Qv; 81.15.Gh; 77.55.+f; 68.35.-p 相似文献
42.
43.
44.
45.
46.
合成了两种新型噻吩基卟啉-5,15-二(2-噻吩基)-2,8,12,18-四乙基-3,7,13,17-四甲基卟啉7a(45.1%)和5,15-二(2-联噻吩基)-2,8,12,18-四乙基-3,7,13,17-四甲基卟啉7b(61.2%),并研究了它们的光谱性质,其中荧光光谱的最大发射峰蜂都在631nm处,量子产率分别为4.1%(7a)和1.4%(7b)。 相似文献
47.
Sung‐Fu Hsu Tzong‐Ming Wu Chien‐Shiun Liao 《Journal of Polymer Science.Polymer Physics》2006,44(23):3337-3347
Poly(3‐hydroxybutyrate) (PHB)/layered double hydroxides (LDHs) nanocomposites were prepared by mixing PHB and poly(ethylene glycol) phosphonates (PEOPAs)‐modified LDH (PMLDH) in chloroform solution. Both X‐ray diffraction data and TEM micrographs of PHB/PMLDH nanocomposites indicate that the PMLDHs are randomly dispersed and exfoliated into the PHB matrix. In this study, the effect of PMLDH on the isothermal crystallization behavior of PHB was investigated using a differential scanning calorimeter (DSC) and polarized optical microscopy. Isothermal crystallization results of PHB/PMLDH nanocomposites show that the addition of 2 wt % PMLDH into PHB induced more heterogeneous nucleation in the crystallization significantly increasing the crystallization rate and reducing their activation energy. By adding more PMLDH into the PHB probably causes more steric hindrance of the diffusion of PHB, reducing the transportation ability of polymer chains during crystallization, thus increasing the activation energy. The correlation among crystallization kinetics, melting behavior and crystalline structure of PHB/PMLDH nanocomposites can also be discussed. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3337–3347, 2006 相似文献
48.
The deformation surrounding Vickers indentations on InGaAsP/InP epilayers have been studied in detail. The surface topography was characterized by using atomic force microscopy (AFM). The material pile-up and sink-in regions around the indentation impression was observed for the quaternary InGaAsP/InP epilayers. The sectional analysis mode of the AFM shows the depth profile at the indented region. Microindentation studies were carried out for different atomic fraction of the quaternary InGaAsP/InP compound semiconductor alloys. The microhardness values of InGaAsP/InP epilayers were found to be in the range of 5.08 and 5.73 GPa. These results show that the hardness value of the quaternary alloy drastically increases as the composition of As was increased by 0.01 atomic fraction and when the phosphorous concentration decreases from 0.4 to 0.38. The reason may be that the increase in As concentration hardens the lattice when phosphorous concentration was less and hardness decreases when phosphorous was increased. 相似文献
49.
Yah ZHAO Xiao Qing LIU Hong You ZHU Zi Ming YANG Rong HUANG 《中国化学快报》2006,17(12):1543-1546
Bridged bis(β-cyclodextrin)s (CDs), as a very important family of CD derivatives, have been known that they can significantly alter the molecular binding ability and selectivity toward a variety of guests in comparison with parent cyclodextrin. Their two… 相似文献
50.
Yong LU Hong WANG Ye LIU Ming Yuan HE 《中国化学快报》2006,17(10):1397-1400
Recently, miniature H2 generator to power fuel cells for portable/micro electronic devices and passenger propulsion has been the focus of intense research activities1-3. One of the strategies is to find simple CO-free H2 production with novel microreactor… 相似文献