全文获取类型
收费全文 | 39309篇 |
免费 | 5652篇 |
国内免费 | 4893篇 |
专业分类
化学 | 29013篇 |
晶体学 | 592篇 |
力学 | 1802篇 |
综合类 | 366篇 |
数学 | 4522篇 |
物理学 | 13559篇 |
出版年
2024年 | 75篇 |
2023年 | 628篇 |
2022年 | 817篇 |
2021年 | 1183篇 |
2020年 | 1383篇 |
2019年 | 1450篇 |
2018年 | 1185篇 |
2017年 | 1264篇 |
2016年 | 1682篇 |
2015年 | 1728篇 |
2014年 | 2157篇 |
2013年 | 2808篇 |
2012年 | 3387篇 |
2011年 | 3637篇 |
2010年 | 2675篇 |
2009年 | 2574篇 |
2008年 | 2762篇 |
2007年 | 2585篇 |
2006年 | 2393篇 |
2005年 | 1968篇 |
2004年 | 1567篇 |
2003年 | 1286篇 |
2002年 | 1231篇 |
2001年 | 1031篇 |
2000年 | 884篇 |
1999年 | 728篇 |
1998年 | 545篇 |
1997年 | 471篇 |
1996年 | 465篇 |
1995年 | 399篇 |
1994年 | 395篇 |
1993年 | 297篇 |
1992年 | 273篇 |
1991年 | 235篇 |
1990年 | 233篇 |
1989年 | 175篇 |
1988年 | 161篇 |
1987年 | 116篇 |
1986年 | 136篇 |
1985年 | 143篇 |
1984年 | 86篇 |
1983年 | 88篇 |
1982年 | 66篇 |
1981年 | 53篇 |
1980年 | 54篇 |
1979年 | 43篇 |
1977年 | 39篇 |
1976年 | 38篇 |
1974年 | 49篇 |
1973年 | 46篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
Zhihui Zhao Hui Dai Xiangmei Wu Haitao Chang Xiaoming Gao Mengjun Liu Pengfei Tu 《Chemistry of Natural Compounds》2007,43(4):374-376
A pectic polysaccharide was isolated from the fruits of Ziziphus jujuba Mill. cv. jinsixiaozao Hort. and its structure was characterized by acid hydrolysis, methylation, and NMR spectroscopies.
The purified fraction Ju-B-7 had a molecular mass of over 2000 kDa. Chemical and spectroscopic analyses indicated that Ju-B-7
is composed mainly of α-1,4-linked D-galactopyranosyluronic acid and 1,2-linked L-rhamnose with a molar ratio of 8.1:1. It can significantly stimulate
spleen cell proliferation in vitro (P<0.01, 10 μmg/mL).
Published in Khimiya Prirodnykh Soedinenii, No. 4, pp. 311–312, July–August, 2007. 相似文献
122.
123.
Ju Yeon Woo Eun Hee Kim Tae Hoon Yoon Jae Chang Kim Byung Kyu Kim 《Liquid crystals》2007,34(9):1115-1120
Chiral dopants were added to the formulation of holographic polymer-dispersed liquid crystals and the effects studied in terms of grating formation dynamics, morphology, diffraction efficiency, contrast ratio and electro-optical properties of the films. A gradual increase of real-time diffraction efficiency, decrease of droplet size and increase of diffraction efficiency of the composite film were obtained with the addition and increasing content of chiral dopant, due to the increased viscosity of the liquid crystal (LC) doped with the chiral dopant leading to decreased droplet coalescence. The contrast ratio decreased with increasing content of chiral dopant due to the difficult orientation of LC molecules caused by the formation of a helical structure. Addition of a small amount of the chiral dopant increased the driving voltage slightly, whereas the decay time is decreased significantly as a result of the high twisting of the helical structure. 相似文献
124.
125.
126.
127.
Jie Xue Liang Chen Li Zhou Zhifeng Jia Yanping Wang Xinyuan Zhu Deyue Yan 《Journal of Polymer Science.Polymer Physics》2006,44(15):2050-2057
α‐Cyclodextrin (α‐CD) has been complexed with various poly(ethylene glycol) (PEG) derivatives in aqueous solution. It has been found that the end groups of PEG derivatives affect the complexation kinetics greatly, but have only a little influence on the thermodynamic behavior. By increasing the hydrophobicity of end groups, the complexation speeds up rapidly. On the other hand, the bulky end groups slow down the threading of polymeric guests into the cavity of CD. By changing the hydrophobicity and the size of end groups, the complexation rate can be adjusted in the range of several orders of magnitudes, which should be quite useful in the design of new supramolecular systems. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2050–2057, 2006 相似文献
128.
对Sn-C60薄膜进行紫外可见光吸收,X-射线衍射和扫描电镜的测定结果显示,薄膜样品紫外可见光吸收的两个短波段吸收峰比纯C60薄膜的吸收峰显著下降,说明Sn-C60薄膜的电子光吸收跃迁为间接跃迁,能带中有杂质能级的存在;样品的X射线衍射峰则对应于面心立方结构;扫描电镜结果显示薄膜为纳米级颗粒组成。 相似文献
129.
C.-S. Huang T. Li L. Wei Q.-S. Yan 《The European Physical Journal C - Particles and Fields》2002,23(1):195-199
It is shown that new sources of CP violation can be generated in models with more than one extra dimension. In the supersymmetric models on the space-time , where the radius moduli have auxiliary vacuum expectation values and the supersymmetry breaking is mediated by the Kaluza–Klein
states of the gauge supermultiplets, we analyze the gaugino masses and trilinear couplings for two scenarios and obtain the
result that there exist relative CP violating phases among the gaugino masses and trilinear couplings.
Received: 10 October 2001 / Published online: 20 December 2001 相似文献
130.
在分析红外图象和视图象差异的基础上,研究了一种适用于可视图像序列的运动小目标检测算法。受目标影响的象素点具有较弱的时间相关性,即相对普通象素点有较大的时间方差,根据此特征,用管道更新的方法产生新方差图象序列,再用管道更新的方法累积,增加信噪比,然后用基于统计均值的自适应门限方法分割出目标,最后将原图象的梯度倒数作为象素点强度的加权,有效地抑制灰度突变边界的传感器噪音,保存目标点。 相似文献