全文获取类型
收费全文 | 21412篇 |
免费 | 1379篇 |
国内免费 | 1876篇 |
专业分类
化学 | 20530篇 |
晶体学 | 410篇 |
力学 | 721篇 |
综合类 | 77篇 |
数学 | 156篇 |
物理学 | 2773篇 |
出版年
2024年 | 6篇 |
2023年 | 203篇 |
2022年 | 326篇 |
2021年 | 387篇 |
2020年 | 625篇 |
2019年 | 668篇 |
2018年 | 699篇 |
2017年 | 961篇 |
2016年 | 1102篇 |
2015年 | 845篇 |
2014年 | 862篇 |
2013年 | 2183篇 |
2012年 | 1382篇 |
2011年 | 1161篇 |
2010年 | 1068篇 |
2009年 | 1303篇 |
2008年 | 1116篇 |
2007年 | 1192篇 |
2006年 | 1021篇 |
2005年 | 875篇 |
2004年 | 770篇 |
2003年 | 657篇 |
2002年 | 551篇 |
2001年 | 493篇 |
2000年 | 507篇 |
1999年 | 443篇 |
1998年 | 406篇 |
1997年 | 358篇 |
1996年 | 286篇 |
1995年 | 352篇 |
1994年 | 276篇 |
1993年 | 221篇 |
1992年 | 178篇 |
1991年 | 152篇 |
1990年 | 147篇 |
1989年 | 130篇 |
1988年 | 157篇 |
1987年 | 167篇 |
1986年 | 99篇 |
1985年 | 77篇 |
1984年 | 90篇 |
1983年 | 21篇 |
1982年 | 56篇 |
1981年 | 25篇 |
1980年 | 19篇 |
1979年 | 17篇 |
1978年 | 6篇 |
1977年 | 4篇 |
1973年 | 6篇 |
1959年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 515 毫秒
121.
Danch A. Lohner K. Ungerank M. Stelzer F. 《Journal of Thermal Analysis and Calorimetry》1998,54(1):161-170
Bis [(ω-(4′-cyanobiphenyl)-4-yl)oxy-n-alkyl]norborn-5-ene-2,3-dicarboxylate was polymerised via ring opening metathesis polymerisation
(ROMP). Two disubstituted polynorbornene derivatives both of cis configuration with different length of the side-chain were
studied. Differential scanning calorimetry (DSC) was used to study the effect of thermal history on the assignment of the
glass transition event associated with the biaxial orientation of a smectic phase. Glass transition temperatures, the change
of isobaric specific heats at Tg and the enthalpies of isotropisation were calculated. The DSC traces only show the classic step-wise change in Tg in some cases, giving the evidence that the amorphous domains are constrained and highly restricted in movement due to the
morphology developed as a result of the biaxial stretching. Based on the literature data of mono- and disubstituted polynorbornene
derivatives and our calorimetric experiments, the shape of Tg dependence on number of (CH2) units is interpreted. The origin of this shape is discussed.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
122.
本文研究了用电位滴定法测定模拟高放废液中游离酸的方法。用草酸钾做络合剂以消除Fe^3+、Al^3+、Nd^3+等多种水解离子的影响,用标准碱直接进行电位滴定,即可快速准确地测定模拟高放废液中游离酸的含量。方法的相对标准偏差为1.8%,标准加入回收率为100-101%,能为放射性废物固化试验提供可靠的分析数据。 相似文献
123.
Simultaneous separation and identification of hashish constituents by coupled liquid chromatography-mass spectrometry (HPLC-MS) 总被引:1,自引:0,他引:1
C. Rustichelli V. Ferioli F. Vezzalini M. C. Rossi G. Gamberini 《Chromatographia》1996,43(3-4):129-134
Summary This paper reports the use of liquid chromatography for the separation and determination of the major cannabinoids extracted from hashish samples. The direct coupling to the mass spectrometer enables the selective identification both of neutral and acidic cannabinoids. The developed method does not require any preliminary derivatization and should, therefore, be of interest in forensic analysis for simple and unequivocal determination of hashish constituents.Part of this work was presented at the 2nd Italian-Spanish Joint Meeting of Medicinal Chemistry, 30 August–3 September 1995, Ferrara, Italy. 相似文献
124.
高效液相色谱法测定花生中黄曲霉毒素 总被引:3,自引:0,他引:3
本文报导了用高效液相色谱-荧光检测法测定了花生中黄曲霉毒素的方法,并做了回收验证。实验证明本法具有灵敏度高,分离能力强,测试结果准确可靠,色谱条件,RP18柱,甲醇四氢呋喃水溶液作流动相,流速1mL/min。 相似文献
125.
Polyazido high-nitrogen compounds: hydrazo- and azo-1,3,5-triazine 总被引:13,自引:0,他引:13
Huynh MH Hiskey MA Hartline EL Montoya DP Gilardi R 《Angewandte Chemie (International ed. in English)》2004,43(37):4924-4928
126.
127.
Ionic liquids are a new kind of room-temperature molten organic salts. It can be used as solvents in the organic/polymeric syntheses, and some of them are called "green" solvents because of its recyclability1. Ionic liquids possess the superior properties, such as thermal stability up to 200(C, involatility and re-designability(for both cation and anion). The ionic liquid employed in this work is [bmim] [PF6]- ( butylmethylimidazolium hexafluorophosphate ) which is immiscible with water and h… 相似文献
128.
Summary Chiral recognition of many enantiomeric solutes by a chiral amide stationary phase is based mainly on hydrogen bonding. A
chiral-recognition-factor CHI is proposed, given by the difference of the enthalpy change in the enantiomer discrimination,
standardized with respect to the specific interaction of the solutes with the diamide core of the stationary phase. The r?le
of the entropy part is also discussed. By extrapolation of the retention behaviour to elevated temperature, peak inversion
of enantiomers is predicted.
Presented at the 15th International Symposium on Chromatography, Nürnberg, October 1984 相似文献
129.
Summary A new and highly sensitive HPLC method for the simultaneous determination of pirarubicine (THP-doxorubicin) and its metabolites, adriamycin and adriamycinol, in human plasma, is described. Samples were treated by liquid-liquid extraction, the organic phase removed and the residue dissolved in methanol. Separation was on a Lichrocart Supersher RP 8 column, (250×4 mm) 4 m, with a mobile phase of acetonitrile/methanol/formate-buffer. 相似文献
130.
Epoxy resins toughened with carboxyl-terminated butadieneacrylonitrile copolymers (CTBN) are two-phase thermosets. The network of the in situ formed rubber particles depends upon the curing mechanism of the resin. When a primary polyamine such as triethylene tetramine was used as curing agent, the network of the rubber phase was quite incomplete, whereas a perfect rubber network was formed with 2-ethyl-4-methyl imidazole as the curing agent. 相似文献