全文获取类型
收费全文 | 31740篇 |
免费 | 4570篇 |
国内免费 | 16604篇 |
专业分类
化学 | 35834篇 |
晶体学 | 1098篇 |
力学 | 1151篇 |
综合类 | 859篇 |
数学 | 3925篇 |
物理学 | 10047篇 |
出版年
2024年 | 292篇 |
2023年 | 1144篇 |
2022年 | 1360篇 |
2021年 | 1485篇 |
2020年 | 1292篇 |
2019年 | 1426篇 |
2018年 | 929篇 |
2017年 | 1342篇 |
2016年 | 1490篇 |
2015年 | 1667篇 |
2014年 | 2396篇 |
2013年 | 2709篇 |
2012年 | 2686篇 |
2011年 | 2597篇 |
2010年 | 2409篇 |
2009年 | 2599篇 |
2008年 | 3000篇 |
2007年 | 2826篇 |
2006年 | 3058篇 |
2005年 | 2722篇 |
2004年 | 2824篇 |
2003年 | 1998篇 |
2002年 | 1215篇 |
2001年 | 1087篇 |
2000年 | 888篇 |
1999年 | 969篇 |
1998年 | 666篇 |
1997年 | 530篇 |
1996年 | 381篇 |
1995年 | 353篇 |
1994年 | 338篇 |
1993年 | 374篇 |
1992年 | 429篇 |
1991年 | 439篇 |
1990年 | 317篇 |
1989年 | 314篇 |
1988年 | 205篇 |
1987年 | 79篇 |
1986年 | 33篇 |
1985年 | 23篇 |
1984年 | 9篇 |
1983年 | 8篇 |
1982年 | 2篇 |
1959年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
22.
5,6-Dihydro-OSW-1 (1) was synthesized following our previous procedure for the total synthesis of OSW-1. This compound demonstrated slightly stronger potency than that of OSW-1 against the growth of cancer cells. 相似文献
23.
Ming Zhao WANG Guan Liang CAI Ling XIA Jun Jian YAO Hong Yan CHEN Zhao Xing MENG Bo Li LIUDepartment of Chemistry Beijing Normal University Beijing Chemical Defense Institute PLA Beijing 《中国化学快报》2004,15(4):495-497
The crystal structures of two potential tumor imaging agents and therapeutic agents -copper(Ⅱ) complexes with salicylidene-tyrosinato Schiff base and nitrogen-donor chelating Lewis base, [Cu(sal-tyr)(bipy)] 1 and [Cu(sal-tyr)(phen)]2CH3OH 2 are presented. Our work is helpful to get deep understanding of novel 64Cu tumor imaging agents and therapeutic agents. 相似文献
24.
报道了一种用国产激光二极管泵浦的1064nm单频NdYVO4红外激光器的设计.利用布氏片和石英晶体组合构成的双折射滤光片技术,在泵浦功率为800mW时,实现了功率为360mW的1064nm红外单频输出.测量结果表明,偏振比超过了10001,功率稳定性优于0.5%,振幅噪声小于0.1%. 相似文献
25.
Spin-Polarized Tunnelling Magnetoresistance Effects in La0.833K0.167MnO3/SrTiO3 Polycrystalline Perovskite Manganites 下载免费PDF全文
A sample of La0.833K0.167MnO3-SrTiO3 (LKMO/STO) is fabricated by the sol-gel method. The microstructure,magnetic and transportation properties have been studied. X-ray diffraction patterns indicate that the structure of LKMO/STO is a homogeneous solid solution phase. The resistivity of LKMO/STO shows the insulator behaviour, which is different from La0.833K0.167MnO3 (LKMO) whose resistivity shows metal-insulator transition with decreasing temperature. The low-field (moH = 0.02 T) magnetoresistance decreases from 11% to 0.2% with the increasing temperature from 4 K‘to 220K for the LKMO/STO sample. The magnitude of magnetoresistance in a strong field (μoH = 5.5 T) almost increases linearly with decreasing temperature and reaches the maximum of 65% at the low temperature of 4.2K, which is much higher than that oE LKMO (40%). The enhanced low-field magnetoresistance effects are quantitatively explained by the spin-polarized tunnelling at grain boundaries. 相似文献
26.
We investigate magnetic and crystalline microstructures of melt-spun (Fe0.675Pt0.325)100-xBx (x=12, 14, 16, 18,20) nanocomposite ribbons after optimal thermal treatment using a magnetic force microscope. The magnetic microstructures are characterized by darker spots adjacent to brighter ones in a sub-micro scale and in random distribution. It is found that the strength of the exchange coupling interaction between the crystals in the 10-100 nm scale, implied by the maximum value (δM)max of the Henkel plot, could be roughly described by the ratio of the average width of the magnetic spots w^- to the average crystal size D^- for the ribbons. Moreover, we find that the intrinsic coercivity jHc of the ribbons is sensitive to their crystal sizes, and the smaller D^-, the higher jHc. Finally, by using roughness analysis, the curve of the root mean square values (δФ)rms of the phase shift of the magnetic force images versus the boron content x is obtained, which is qualitatively consistent with that of the magnetization σ12 kOe of the ribbons versus x. 相似文献
27.
在γ跃迁能量中扣除了ΔI=4分岔的影响后,根据ab公式,系统讨论了A~190区偶偶核超形变带,给出了绝大多数超形变带的自旋值. 部分超形变带的自旋指定值,不同于其它方法得到的结果. 相似文献
28.
29.
HUYUDA MENGZHIQING 《高校应用数学学报(英文版)》1998,13(4):473-477
In this paper, the existence theorem of the cone-weak subdiflerential of set-valued mapping in locally convex topological vector space is proved. 相似文献
30.
本文研究了单取代硬脂酸二茂铁酯、双取代亚麻酸二茂铁酯、单二茂铁酸十八酯和双二茂铁酸十八酯四种二茂铁衍生物L-B膜修饰铂电极的循环伏安行为,用理论模型模拟了归一化峰面积,峰电位差随扫描速度变化的规律,以及分子相互作用能与半高宽的关系,将实验结果与理论模型的模拟结果进行比较,求得了L-B膜的层间电荷转移速度常数,L-B膜与电极之间的电荷转移速度常数,分子作用能及半峰电位等参数,并比较了四种二茂铁衍生物 相似文献