全文获取类型
收费全文 | 25077篇 |
免费 | 2702篇 |
国内免费 | 3055篇 |
专业分类
化学 | 18435篇 |
晶体学 | 356篇 |
力学 | 1050篇 |
综合类 | 289篇 |
数学 | 3005篇 |
物理学 | 7699篇 |
出版年
2024年 | 43篇 |
2023年 | 239篇 |
2022年 | 576篇 |
2021年 | 628篇 |
2020年 | 665篇 |
2019年 | 723篇 |
2018年 | 612篇 |
2017年 | 563篇 |
2016年 | 924篇 |
2015年 | 991篇 |
2014年 | 1174篇 |
2013年 | 1794篇 |
2012年 | 1898篇 |
2011年 | 1998篇 |
2010年 | 1463篇 |
2009年 | 1398篇 |
2008年 | 1738篇 |
2007年 | 1572篇 |
2006年 | 1467篇 |
2005年 | 1234篇 |
2004年 | 1106篇 |
2003年 | 1032篇 |
2002年 | 1100篇 |
2001年 | 896篇 |
2000年 | 709篇 |
1999年 | 547篇 |
1998年 | 343篇 |
1997年 | 348篇 |
1996年 | 306篇 |
1995年 | 260篇 |
1994年 | 276篇 |
1993年 | 238篇 |
1992年 | 234篇 |
1991年 | 175篇 |
1990年 | 160篇 |
1989年 | 132篇 |
1988年 | 95篇 |
1987年 | 93篇 |
1986年 | 84篇 |
1985年 | 99篇 |
1984年 | 89篇 |
1983年 | 56篇 |
1982年 | 74篇 |
1981年 | 67篇 |
1980年 | 67篇 |
1979年 | 54篇 |
1978年 | 69篇 |
1977年 | 58篇 |
1976年 | 54篇 |
1973年 | 46篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
PECVDSiON薄膜的工艺控制,性质及其潜在应用 总被引:2,自引:1,他引:1
研究了等离子增强化学气相淀积氮氧化硅薄膜的工艺控制、性质以及薄膜波导在超大规模集成电路光互连中的潜在应用。 相似文献
102.
The reactions of IO radicals with CH3SCH3, CH3SH, C2H4, and C3H6 have been studied using the discharge flow method with direct detection of IO radicals by mass spectrometry. The absolute rate constants obtained at 298 K are the following: IO + CH3SCH3 → products (1): k1 = (1.5 ± 0.2) × 10?14; IO + CH3SH → products (2): k2 = (6.6 ± 1.3) × 10?16; IO + C2H4 →products (3): k3 < 2 × 10?16; IO + C3H6 → products (4): k4 < 2 × 10?16 (units are cm3 molecule?1 s?1). CH3S(O)CH3 and HOI were found as products of reactions (1) and (2), respectively. The present lower value of k1 compared to our previous determination is discussed. 相似文献
103.
Nguyen Hoa Hong Joe Sakai Ngo Thu Huong Virginie Brizé 《Journal of magnetism and magnetic materials》2006
Laser-ablated Co-doped In2O3 thin films were fabricated under various growth conditions on R-cut Al2O3 and MgO substrates. All Co:In2O3 films are well-crystallized, single phase, and room temperature ferromagnetic. Co atoms were well substituted for In atoms, and their distribution is greatly uniform over the whole thickness of the films. Films grown at 550 °C showed the largest magnetic moment of about 0.5 μB/Co, while films grown at higher temperatures have magnetic moments of one order smaller. The observed ferromagnetism above room temperature in Co:In2O3 thin films has confirmed that doping few percent of magnetic elements such as Co into In2O3 could result in a promising magnetic material. 相似文献
104.
105.
Wei‐Lie Xiao Jian‐Xin Pu Rui‐Rui Wang Liu‐Meng Yang Xiao‐Li Li Sheng‐Hong Li Rong‐Tao Li Sheng‐Xiong Huang Yong‐Tang Zheng Han‐Dong Sun 《Helvetica chimica acta》2007,90(8):1505-1513
Seven new highly oxygenated nortriterpenoids, rubriflorins D–J ( 1 – 7 ), were isolated from the leaves and stems of Schisandra rubriflora, and their structures were elucidated on the basis of extensive analysis of spectroscopic data. These new compounds feature the opening of ring A compared with related known nortriterpenoids isolated from the genus Schisandra and showed weak activity against HIV‐1. 相似文献
106.
关于结合方案和PBIB设计的定义及所用的有关符号见文献[1].设F_q为特征为2的有限域,q=2~r.熟知F_q上的对称矩阵合同于以下三种形式的矩阵(见[1]p.24). 相似文献
107.
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
108.
资源共享方式若干问题的研讨 总被引:3,自引:1,他引:2
社会公用服务系统和工程技术系统,存在共同的资源共享问题。本文通过典例就资源共享方式的若干问题加以探究:讨论广义的多用户系统中人工资源共享方式的分类;阐述常用的共享方式的特点、优缺点;分析系统时间性能及其改进与共享方式的关系等。文章还提出在系统工程范畴里,应对社会公用服务和工程技术两类系统的资源共享方式予以综合研究,并相互借鉴和移植。 相似文献
109.
110.
In this article we consider partitioned Runge-Kutta (PRK) methods for Hamiltonian partial differential equations (PDEs) and present some sufficient conditions for multi-symplecticity of PRK methods of Hamiltonian PDEs.