全文获取类型
收费全文 | 1479篇 |
免费 | 55篇 |
国内免费 | 383篇 |
专业分类
化学 | 1017篇 |
晶体学 | 2篇 |
力学 | 79篇 |
综合类 | 5篇 |
数学 | 347篇 |
物理学 | 467篇 |
出版年
2016年 | 5篇 |
2015年 | 13篇 |
2014年 | 2篇 |
2013年 | 15篇 |
2012年 | 20篇 |
2011年 | 349篇 |
2010年 | 161篇 |
2009年 | 152篇 |
2008年 | 19篇 |
2007年 | 33篇 |
2006年 | 32篇 |
2005年 | 104篇 |
2004年 | 300篇 |
2003年 | 128篇 |
2002年 | 112篇 |
2001年 | 133篇 |
2000年 | 28篇 |
1999年 | 29篇 |
1998年 | 37篇 |
1997年 | 28篇 |
1996年 | 23篇 |
1995年 | 21篇 |
1994年 | 23篇 |
1993年 | 50篇 |
1992年 | 42篇 |
1991年 | 20篇 |
1990年 | 10篇 |
1989年 | 12篇 |
1988年 | 2篇 |
1986年 | 4篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1982年 | 2篇 |
1979年 | 1篇 |
1975年 | 1篇 |
1972年 | 1篇 |
1971年 | 2篇 |
1955年 | 1篇 |
排序方式: 共有1917条查询结果,搜索用时 15 毫秒
101.
LI Cun-man XIAO Yuan-sheng XUE Xing-ya FENG Jia-tao ZHANG Xiu-li LIANG Xin-miao . Dalian Institute of Chemical Physics Chinese Academy of Sciences Dalian P. R. China . Hebei Research Centre of Analysis Testing Hebei University of Science Technology Shijiazhuang 《高等学校化学研究》2011,(3):392-396
An efficient preparative method was successfully developed for isolation and purification of unstable components from medicinal plant extracts, using a combined method of preparative high performance liquid chro-matography(HPLC) and solid-phase extraction(SPE). The aim of this study was to obtain an effective method with high preparative efficiency and importantly to avoid the transformation of unstable compounds. The preparative HPLC system was based on an LC/MS controlled four-channel autopurification sys... 相似文献
102.
ZENG ZhenHua MA XiuFang DING WuChen & LI WeiXue State Key Laboratory of Catalysis Center for Theoretical Computational Chemistry Dalian Institute of Chemical Physics Chinese Academy of Sciences Dalian China 《中国科学:化学》2010,(2)
Combined with third generation synchrotron radiation light sources, X-ray photoelectron spectroscopy (XPS) with higher energy resolution, brilliance, enhanced surface sensitivity and photoemission cross section in real time found extensive applications in solid-gas interface chemistry. This paper reports the calculation of the core-level binding energy shifts (CLS) using the first-principles density functional theory. The interplay between the CLS calculations and XPS measurements to uncover the structures,... 相似文献
103.
SHANG Jing ZHAO FengWei ZHU Tong & LI Jia State Key Joint Laboratory of Environmental Simulation Pollution Control College of Environmental Sciences Engineering Peking University Beijing China 《中国科学B辑(英文版)》2011,(1)
Perylene tetracarboxylic diimide (PTCDI),widely used in organic photovoltaic devices,is an n-type semiconductor with strong absorption in the visible-light spectrum.There has been almost no study of the PTCDI-sensitized TiO2 composite used to photocatalytically degrade pollutants.In this study,PTCDIand copper phthalocyanine tetrasulfonic acid (CuPcTs)-sensitized TiO2 composites were prepared using a hydrothermal method.The morphologies and structures of the two composites were characterized by X-ray diffrac... 相似文献
104.
105.
采用碳酸钠-硼砂(质量比1:1)做熔剂分解钇铝石榴石,并确定了熔剂的最优化条件.以电感耦合等离子体光谱法对样品中掺杂Yb(Ⅲ)离子作了定量检测考察了样品和熔剂中单个基体和混合基体对分析结果的影响.发现单个基体Y对Yb的测定有增强效应.基体A1对Yb的测定有一定的抑制作用;基体对Yb测定的干扰可通过基体匹配进行消除元素的俭出限为2μg/L,标准加入回收率为88%~100%实际样品7次检测的RSD为2.1%。本方法可以较好地满足实际样品分析的需要。 相似文献
106.
107.
108.
毛细管气相色谱法测定热不稳定有机磷农药辛硫磷 总被引:11,自引:0,他引:11
The thermo-labile organophosphorous pesticide Phoxim was determined by capillary gas chromatographywith flame phototnetric detector. When high linear velocity H_2(>200cm/s) was used as carrier gas,the thermo-decomposition of Phoxim was considerably reduced.The most important gas chromatography conditions,injectortempereture and column head pressure,were studied.The thermo-decomposition preducts were identified by gaschromatography-mass spectrometry. 相似文献
109.
本文报导了傅里哀变换红外发射光谱法研究多相氧化物催化剂的实验装置的建立及实验条件的考察。设计加工了一个温度范围宽,可在各种气氛和真空条件下原位研究氧化物催化剂的红外发射池。以MoO_3为例,考察了样品厚度,测试温度对发射光谱的影响。当样品量小于1mm·cm~(-2)时,随样品量增加,谱峰强度线性增加,但峰形不发生变化。当样品量高于1mg.cm~(-2)时,随样品量增加,谱图严重畸变。随样品温度升高,谱峰强度近似线性增加。并用该方法研究了MoO_3在还原和再氧化过程中表面氧物种的变化。结果表明桥式MO?O?Mo物种比端基Mo=O物种较易还原,再氧化时,Mo=O物种比Mo?O?Mo物种优先形成。 相似文献
110.
Lu Shi-Jie Yang Fan Fu Hong-XiangOSSO Laboratory Lanzhou Institute of Chemical Physics Chinese Academy of Sciences Lanzhou CHINAShi Jian-QiuFujian Institute of Research on the Structure of Matter Chinese Academy of Sciences Fuzhou CHINA 《结构化学》1993,(5)
<正> Co2 ( CO ) 6 (dppp ) Cdppp = 1,3-bis ( diphenylphosphino ) propane = Ph2P(CH2)3PPh2D, Mr=698. 38, monoclinic, space group P21/c, a=14. 952(8) , b = 13.44(2), c = 16. 72(1) A. β=110.56(4)°, V=3147(9) A3, Z = 4, A=1. 47 g/cm3, λ(MoXα) = 0. 71069 A, F(000) = 1424, λ(MoKα) = 11. 93 cm-1, R = 0. 032 and Rw = 0. 044 for 4553 observed independent reflections with I>4. 0σ(I). The molecular structure of the complex shows that the dppp ligand chelates one of the two cobalt atoms of the complex molecule, and there are two bridging carbonyl groups between the two cobalt atoms. The Co-Co bond length is 2. 534(3) A . The chelating dppp ligand results in the asymmetrization of the molecule. 相似文献