全文获取类型
收费全文 | 1971篇 |
免费 | 315篇 |
国内免费 | 246篇 |
专业分类
化学 | 1428篇 |
晶体学 | 20篇 |
力学 | 118篇 |
综合类 | 18篇 |
数学 | 192篇 |
物理学 | 756篇 |
出版年
2024年 | 2篇 |
2023年 | 54篇 |
2022年 | 47篇 |
2021年 | 80篇 |
2020年 | 111篇 |
2019年 | 97篇 |
2018年 | 67篇 |
2017年 | 61篇 |
2016年 | 90篇 |
2015年 | 93篇 |
2014年 | 92篇 |
2013年 | 119篇 |
2012年 | 139篇 |
2011年 | 170篇 |
2010年 | 128篇 |
2009年 | 127篇 |
2008年 | 140篇 |
2007年 | 119篇 |
2006年 | 117篇 |
2005年 | 101篇 |
2004年 | 62篇 |
2003年 | 55篇 |
2002年 | 46篇 |
2001年 | 55篇 |
2000年 | 49篇 |
1999年 | 45篇 |
1998年 | 32篇 |
1997年 | 29篇 |
1996年 | 41篇 |
1995年 | 29篇 |
1994年 | 35篇 |
1993年 | 21篇 |
1992年 | 14篇 |
1991年 | 16篇 |
1990年 | 9篇 |
1989年 | 13篇 |
1988年 | 11篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1979年 | 1篇 |
排序方式: 共有2532条查询结果,搜索用时 15 毫秒
1.
Liying Zhang Chuanrui Zhao Yujiao Bai Qian Wang Pan Ma Xiaojie Ma Peihua Zhu 《Electroanalysis》2022,34(2):302-309
The design and exploration of efficient, stable and environmentally compatible organic emitters for an electrochemiluminescence (ECL) sensor is a promising topic. Herein, a novel environmentally-friendly luminophore, ZnBCBTP@MWCNTs, were fabricated via self-assembly of porphyrin molecules (ZnBCBTP) onto multi-walled carbon nanotubes (MWCNTs). The resulting luminophore ZnBCBTP@MWCNTs displayed not only the highly ECL property and but also the good accelerated electron mobility. Then, a label-free ECL biosensor based ZnBCBTP@MWCNTs was constructed for the ultrasensitive detection of uric acid. Excitingly, this proposed ECL biosensor performed a good linear relationship in the range of 0–300 μM with a low detection limit of 1.4 μM, thus offering another reliable and feasible sensing platform for clinical bioanalysis with good selectivity, stability, and repeatability. 相似文献
2.
Shufeng Zuo 《Applied Surface Science》2006,253(5):2508-2514
Al-pillared clays supported rare earths (RE/Al-PILC) are prepared and used as supports of palladium catalysts for deep oxidation of low concentrations of benzene (130-160 ppm). The supports and catalysts are characterized by X-ray powder diffraction (XRD), FT-IR, BET, transmission electron microscopy (TEM) and temperature-programmed reduction (H2-TPR). The results show that Al-pillaring results in a strong increase in the basal spacing (d0 0 1) from about 1.2 to 1.8 nm, and an increase in the BET surface area from 63.6 (±3.2) to 238.8 (±11.9) m2/g. Activity tests of deep oxidation of low concentration benzene show catalysts supported on Al-PILC and RE/Al-PILC are obviously more active than that on raw clay. Pd/6% Ce/Al-PILC, in particular, can catalyze the complete oxidation of low concentration benzene at a temperature as low as about 290 °C. 相似文献
3.
Zuo LIU Zhen De WU 《数学学报(英文版)》2005,21(5):997-1000
Let κ be non-negative integer. The unoriented bordism classes, which can be represented as [RP(ξ^κ)] where ξ^κ is a k-plane bundle, form an ideal of the unoriented bordism ring MO.. A group of generators of this ideal expressed by a base of MO. and a necessary and sufficient condition for a bordism class to belong to this ideal are given. 相似文献
4.
Vincent S. Smentkowski John T. Yates Jr. Xiaojie Chen William A. Goddard III 《Surface science》1997,370(2-3):209-231
The radiation-induced decomposition of C4F9I and CF3I overlayers at 119 K on diamond (100) surfaces has been shown to be an efficient route to fluorination of the diamond surface. X-ray photoelectron spectroscopy has been used for photoactivation as well as for studying the photodecomposition of the fluoroalkyl iodide molecules, the attachment of the photofragments to the diamond surface, and the thermal decomposition of the fluoroalkyl ligands. Measured chemical shifts agree well with ab initio calculations of both C 1s and F 1s binding energies. It is found that chemisorbed CF3 groups on diamond (100) decompose by 300 K whereas C4F9 groups decompose over the range 300 to 700 K and this reactivity difference is rationalized on steric grounds. Both of these thermal decomposition processes produce surface C---F bonds on the diamond. The surface C---F species thermally decompose over a wide temperature range extending up to 1500 K. Hydrogen passivation of the diamond surface is ineffective in preventing free radical attack from the photodissociated products of the fluoroalkyl iodides; I atoms produced photolytically abstract H from surface C---H bonds to yield hydrogen iodide at 119 K allowing diamond fluorination. The attachment of chemisorbed F species to the diamond (100) surface causes band bending as the surface states are occupied as a result of chemisorption. This results in a shift to higher binding energy of the diamond-related C 1s levels present in the surface and subsurface regions which are sampled by XPS on the diamond. The use of photoactivation of fluoroalkyl iodides for the fluorination of diamond surfaces provides a convenient route compared to other methods involving the action of atomic F, molecular F2, XeF2 and F-containing plasmas. 相似文献
5.
6.
Precise measurement of magnetic moment of short-lived β-emitting nuclei12B ( I π=1+, T 1/2=20.18 ms)
Zhou Dongmei Zheng Yongnan Du Enpeng Xu Yongjun Zhu Jiazheng Yuan Daqing Wang Zhiqiang Luo Hailong Zuo Yi Ma Ruigang Duan Xiao M. Mihara M. Fukuda K. Matsuta T. Minamisono Zhu Shengyun 《中国科学G辑(英文版)》2004,47(5):531-539
The spin polarized β-emitting nuclei12B (I
π=1+,T
1/2=20.18 ms) were produced by the nuclear reaction11B(d, p)12B and by the selection technique of the incident deuteron energy and the12B recoil angle following the nuclear reaction. The nuclear magnetic moment of the short-lived nuclei12B was measured by β-NMR with the β-NMR and β-NQR setup established for the first time in China. The nuclear magnetic moment
of12B was determined to be μ=0.99993±0.00048 nm org=0.99993±0.00048 after the precise correction of the Knight shift. 相似文献
7.
Optical characterization of bromo-alkoxyl-substituted copper phthalocyanine derivative thin films 总被引:2,自引:0,他引:2
A series of thin films of copper phthalocyanine derivatives with bromine and alkoxyl substituents [CuPc(OC8H17)4Brm, m=0,1,2,4] were prepared on single-crystal silicon substrates by spin coating. The ellipsometric spectra of the films have been studied on a rotating analyzer–polarizer type of scanning ellipsometer. The optical, dielectric constants and absorption coefficients of the films in 500–800 nm wavelength region were obtained. The results show that the complex refractive index, dielectric constants and absorption coefficient of these thin films are influenced regularly by bromine substituent on conjugated macrocycle. It was found that there are approximately linear relationships between the resonance absorption wavelengths of the films and the average number of bromine atoms substituted on the phthalocyanine ring. 相似文献
8.
随着科学技术的发展和人民生活水平的不断提高,电脑在人们的日常生活、工作、学习中已经成为一种不可缺少的常用工具.对学校而言,建立先进的电化教学网络和要求教师运用电化教学手段进行授课已经成为学校教学改革的中心任务.这是时代进步的标志,使传统的教学方法找到了更为有效的辅助手段,大大地提高教学质量,为实现对 相似文献
9.
10.