全文获取类型
收费全文 | 48537篇 |
免费 | 9947篇 |
国内免费 | 17946篇 |
专业分类
化学 | 34670篇 |
晶体学 | 2296篇 |
力学 | 3958篇 |
综合类 | 2028篇 |
数学 | 8023篇 |
物理学 | 25455篇 |
出版年
2024年 | 135篇 |
2023年 | 507篇 |
2022年 | 1860篇 |
2021年 | 1788篇 |
2020年 | 1696篇 |
2019年 | 1664篇 |
2018年 | 1534篇 |
2017年 | 2426篇 |
2016年 | 1632篇 |
2015年 | 2528篇 |
2014年 | 3067篇 |
2013年 | 4076篇 |
2012年 | 3919篇 |
2011年 | 4145篇 |
2010年 | 4318篇 |
2009年 | 4446篇 |
2008年 | 5064篇 |
2007年 | 4442篇 |
2006年 | 4417篇 |
2005年 | 3859篇 |
2004年 | 2945篇 |
2003年 | 2112篇 |
2002年 | 2088篇 |
2001年 | 2145篇 |
2000年 | 2241篇 |
1999年 | 1270篇 |
1998年 | 674篇 |
1997年 | 546篇 |
1996年 | 502篇 |
1995年 | 450篇 |
1994年 | 524篇 |
1993年 | 482篇 |
1992年 | 416篇 |
1991年 | 294篇 |
1990年 | 294篇 |
1989年 | 326篇 |
1988年 | 263篇 |
1987年 | 211篇 |
1986年 | 165篇 |
1985年 | 132篇 |
1984年 | 130篇 |
1983年 | 137篇 |
1982年 | 120篇 |
1981年 | 106篇 |
1980年 | 91篇 |
1979年 | 69篇 |
1978年 | 28篇 |
1977年 | 24篇 |
1976年 | 20篇 |
1974年 | 20篇 |
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
11.
12.
Electroluminescence of a Multi-Layered Organic Light-Emitting Diode Utilizing Trans-4-[p-[N-methyl-N-(hydroxymethyl)amino]styryl]-N-Methylphridinium Tetraphenylborate as the Active Layer 下载免费PDF全文
Employing an organic dye salt of trans-4-[p-[N-methyl-N-(hydroxymethyl)amino]styryl]-N-methylphridinium tetra\-phenylborate (ASPT) as the active layer, 8-hydrocyquinoline aluminium (Alq3) as the electron transporting layer and N,N’-diphenyl-N,N’-bis(3-methylphenyl)-[1,1’-biphenyl]-4,4’-diamine (TPD) as the hole transporting layer, respectively, we fabricate a multi-layered organic light-emitting diode and observe the colour tunable electroluminescence (EL). The dependence of the EL spectra on the applied voltage is investigated in detail, and the recombination mechanism is discussed by considering the variation of the hole-electron recombination region. 相似文献
13.
采用MTT比色法对体外培养的肿瘤细胞进行细胞毒作用实验,验证槲寄生蛋白注射液体外抗肿瘤效果.并且鉴定这种检测方法的有效性。实验结果表明槲寄生蛋白注射液有一定的体外抗肿瘤效果;MTT比色法是一种可用的体外细胞毒作用检测法,为新药品的开发提供了实验依据。 相似文献
14.
宁波城市设计的若干思考与建议 总被引:1,自引:0,他引:1
张柳燕 《宁波大学学报(理工版)》2004,17(2):166-169
通过探讨城市设计概念的形成过程和历史积淀,阐明其在城市建设中的意义,并运用城市设计的理论与分析方法,针对目前宁波城市大规模的规划、设计、改造现象,提出若干思考与建议. 相似文献
15.
The electronic structure and magnetism of SmCo7-xZrx alloy are investigated using the spin-polarized MS-X. method. The results show that a few of electrons are transferred to the Sm(5d0) orbital due to orbital hybridization between Sm and Co atoms. The exchange interactions between 3d and 5d electrons are more important than the polarization effects of the conductive electrons, thus it is the main reason resulting in the long-range ferromagnetic order in SmCo7-xZrx. The Curie temperature of SmCo7-xZrx is generally lower than that of corresponding pure Co, which may be explained by the weaker average coupling strength between Co lattices due to some negative couplings mainly occurring of 2e site. The calculated results for the Sm5Co32Zr2 cluster may lead to a better understanding of why SmCo7-xZrx is stable phase. Since the spin-up DOS peak of d electrons at EF arises and the bonding of electrons at EF strengthens with increasing Zr concentration, which results in the internal energy of the system decrease, the stable ferromagnetic order forms in SmCo7-xZrx. 相似文献
16.
Kan‐Yi Pu Yi Chen Xiao‐Ying Qi Chun‐Yang Qin Qing‐Quan Chen Hong‐Yu Wang Yun Deng Qu‐Li Fan Yan‐Qin Huang Shu‐Juan Liu Wei Wei Bo Peng Wei Huang 《Journal of polymer science. Part A, Polymer chemistry》2007,45(16):3776-3787
In this contribution, we demonstrate a new effective methodology for constructing highly efficient and durable poly(p‐phenyleneethynylene) (PPE) containing emissive material with nonaggregating and hole‐facilitating properties through the introduction of hole‐transporting blocks into the PPE system as the grafting coils as well as building the energy donor–acceptor architecture between the grafting coils and the PPE backbone. Poly(2‐(carbazol‐9‐yl)ethyl methacrylate) (PCzEMA), herein, is chosen as the hole‐transporting blocks, and incorporated into the PPE system as the grafting coils via atom transfer radical polymerization. The chemical structure of the resultant copolymer, PPE‐g‐PCzEMA, was characterized by NMR and gel permeation chromatography, showing that the desirable copolymer was obtained with the narrow polydispersity. The increased thermal stability of PPE‐g‐PCzEMA was confirmed by thermogravimetric analysis and differential scanning calorimetry along with its macroinitiator. The optoelectronic properties of this copolymer were studied in detail by ultraviolet‐visible absorption, photoluminescence emission and excitation spectra, and cyclic voltammogram (CV). The results indicate that PPE‐g‐PCzEMA exhibits the solid‐state luminescent property dominated by individual lumophores, and also the energy transfer process from the PCzEMA blocks to the PPE backbone with a relatively higher energy transfer efficiency in the solid‐state compared to that of the solution state. Additionally, the hole‐injection property is greatly facilitated due to the presence of PCzEMA, as confirmed by CV profiles. All these data indicate that PPE‐g‐PCzEMA is a good candidate for use in optoelectronic devices. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3776–3787, 2007 相似文献
17.
18.
19.
20.
荧光猝灭法测定人发中微量锰 总被引:3,自引:0,他引:3
张根成 《理化检验(化学分册)》2004,40(12):708-709
异丙肾上腺素在pH9.91的伯瑞坦 罗比森缓冲溶液中被MnO-4氧化,导致其荧光强度显著减弱。最大激发及发射波长为278nm和616nm,MnO-4浓度在0.01~0.64mg·L-1范围内,荧光强度与浓度呈良好线性关系。将其用于人发中微量锰的测定,得到满意的结果。 相似文献