全文获取类型
收费全文 | 23268篇 |
免费 | 4584篇 |
国内免费 | 7065篇 |
专业分类
化学 | 17392篇 |
晶体学 | 700篇 |
力学 | 1707篇 |
综合类 | 907篇 |
数学 | 3610篇 |
物理学 | 10601篇 |
出版年
2024年 | 35篇 |
2023年 | 322篇 |
2022年 | 752篇 |
2021年 | 778篇 |
2020年 | 900篇 |
2019年 | 907篇 |
2018年 | 788篇 |
2017年 | 1008篇 |
2016年 | 967篇 |
2015年 | 1259篇 |
2014年 | 1378篇 |
2013年 | 1862篇 |
2012年 | 1745篇 |
2011年 | 1967篇 |
2010年 | 1878篇 |
2009年 | 1912篇 |
2008年 | 2091篇 |
2007年 | 1839篇 |
2006年 | 1788篇 |
2005年 | 1689篇 |
2004年 | 1266篇 |
2003年 | 947篇 |
2002年 | 989篇 |
2001年 | 910篇 |
2000年 | 1010篇 |
1999年 | 672篇 |
1998年 | 399篇 |
1997年 | 307篇 |
1996年 | 304篇 |
1995年 | 275篇 |
1994年 | 265篇 |
1993年 | 241篇 |
1992年 | 215篇 |
1991年 | 192篇 |
1990年 | 174篇 |
1989年 | 127篇 |
1988年 | 131篇 |
1987年 | 118篇 |
1986年 | 93篇 |
1985年 | 76篇 |
1984年 | 74篇 |
1983年 | 75篇 |
1982年 | 44篇 |
1981年 | 39篇 |
1980年 | 45篇 |
1979年 | 22篇 |
1978年 | 6篇 |
1977年 | 8篇 |
1959年 | 6篇 |
1936年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
Xiao Qi ZHENG Yong Hui WANG Qing Xiang GUO* Li YANG You Cheng LIU Department of Chemistry University of Science Technology of China Hefei National Laboratory of Applied Organic Chemistry Lanzhou University Lanzhou 《中国化学快报》2003,(8)
As artificial enzymes, the binding constants of cyclodextrins (CDs) and their substrates are expected to be high1. For this purpose, many kinds of bridged cyclodextrin dimers2 whose two cyclodextrins are linked by various spacers have been constructed. It was of interest to make the dimers, whose binding constants would exceed 108dm3/mol3. Up to date, the bridged cyclodextrin dimers have been extensively studied as enzyme models and as molecular receptors4-6. Recently, we synthesized a brid… 相似文献
53.
54.
HE Xiao-Rong ZHOU Li-Juan Wei-Xing 《理论物理通讯》2005,44(4):670-674
Based on Dyson Schwinger Equations (DSEs) in the “rainbow” approximation, the dependence of quark effective mass on gluon propagator is investigated by use of three different phenomenological gluon propagators with two parameters, the strength parameter x and range parameter △. Our theoretical calculations for the quark effective mass Mf(p^2), defined by the self-energy functions Af(p^2) and Bi(p%2) of the DSEs, show that the dynamically running quark effective mass is strongly dependent on gluon propagator. Therefore, because gluon propagator is completely unknown, the quark effective mass cannot be exactly determined theoretically. 相似文献
55.
Qi Wang Huaxiang Yang Zhiqiang Fan Hong Xu 《Journal of polymer science. Part A, Polymer chemistry》2004,42(5):1093-1099
Ethylisobutylaluminoxane (EBAO) and its analogues were synthesized by a reaction between an triethylaluminum (Et3Al)/triisobutylaluminum (i‐Bu3Al) mixture and 4‐fluorobenzeneboronic acid, phenylboronic acid, or n‐butaneboronic acid and subsequent hydrolysis with water. They were used as cocatalysts in ethylene polymerization catalyzed by an iron complex {[(ArN?C(Me))2C5H3N]FeCl2, where Ar is 2,6‐diisopropylphenyl}. Polyethylene with a high molecular weight and a narrow molecular weight distribution was prepared with modified EBAOs, and the performance of the iron complex at high polymerization temperatures was greatly improved. The activators for the iron complex also affected the polymerization activity and the molecular weight of the resultant polyethylene. It was suggested that the stereo and electronic effects of the substitute groups of aluminoxane contributed to the improved performance of the new activators. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1093–1099, 2004 相似文献
56.
Raymond Mackay Jie Zhang Qi Wu Yuzhuo Li 《Colloids and surfaces. A, Physicochemical and engineering aspects》2004,250(1-3):343-348
The longitudinal relaxation times (T1) of water in concentrated silica and alumina slurries were measured as a function of solids content. It was shown that the results could be fit very well with a two-phase fast-exchange model between free and surface-bound water. As expected, values of T1 for bound water were in the order of 20–2000 times lower than that for free water, indicating a higher effective viscosity of the surface-bound water. The strength of the interaction depended on the particular surface, and all of the aluminas examined interacted more strongly with water than the two silicas studied, which themselves differed considerably. The chemical mechanical polishing (CMP) removal rate of tantalum by silica slurries was shown to be directly correlated with the interaction parameters, derived from the NMR relation times rather than with total surface hydroxyl group concentration. 相似文献
57.
58.
在等离子体增强化学气相淀积系统中,采用aSi:H层淀积和原位等离子体氧化相结合的逐层生长技术制备了aSi:H/SiO_2多层膜.在激光诱导限制结晶原理基础上,使用KrF准分子脉冲激光为辐照源,对aSi:H/SiO_2多层膜进行辐照,使纳米级厚度的aSi:H子层晶化.Raman散射谱和电子衍射谱的结果表明,经过激光辐照后纳米Si颗粒在原始的aSi:H子层内形成,晶粒尺寸可以根据aSi:H层的厚度精确控制.还研究了样品的光致发光(PL)特性以及激光辐照能量密度对PL性质的影响.
关键词:
脉冲激光
多层膜
限制结晶 相似文献
59.
稀土固体是重要的激光和光电子材料。目前 ,由于以宽带信号和太赫兹比特数据传输率为特征的信息技术的发展 ,稀土固体材料的相干瞬态动力学过程成为宽带与高速信息光子学的基本物理问题之一。研究了室温下稀土粉末样品Eu3+ ∶Y2 O3自由感应衰减的相干瞬态光谱 ,这有助于理解有效的光吸收动力学、激发态弛豫、相干能量传递和超短光脉冲在稀土固体中的传播。用一对紫外飞秒相干光脉冲作用于稀土粉末样品Eu3+ ∶Y2 O3,然后监测物质激发态的布居数随两个激发脉冲之间的延时的变化 ,测量到其自由感应衰减量子拍 (FID) ,从拍频周期分析确定了其能级精细结构 ,能级的退相时间长达皮秒量级。理论分析和实验结果符合得很好。对稀土离子的量子干涉的研究 ,表明其在受激受控光放大方面具有潜在的应用前景 相似文献
60.