全文获取类型
收费全文 | 13149篇 |
免费 | 361篇 |
国内免费 | 3篇 |
专业分类
化学 | 6727篇 |
晶体学 | 90篇 |
力学 | 306篇 |
数学 | 2999篇 |
物理学 | 3391篇 |
出版年
2021年 | 102篇 |
2020年 | 156篇 |
2019年 | 149篇 |
2018年 | 263篇 |
2017年 | 256篇 |
2016年 | 491篇 |
2015年 | 403篇 |
2014年 | 470篇 |
2013年 | 985篇 |
2012年 | 621篇 |
2011年 | 817篇 |
2010年 | 478篇 |
2009年 | 412篇 |
2008年 | 570篇 |
2007年 | 538篇 |
2006年 | 465篇 |
2005年 | 289篇 |
2004年 | 308篇 |
2003年 | 248篇 |
2002年 | 253篇 |
2001年 | 193篇 |
2000年 | 197篇 |
1999年 | 160篇 |
1998年 | 149篇 |
1997年 | 139篇 |
1996年 | 130篇 |
1995年 | 118篇 |
1994年 | 107篇 |
1993年 | 115篇 |
1992年 | 130篇 |
1991年 | 108篇 |
1990年 | 126篇 |
1989年 | 110篇 |
1988年 | 112篇 |
1987年 | 107篇 |
1986年 | 103篇 |
1985年 | 151篇 |
1984年 | 164篇 |
1983年 | 128篇 |
1982年 | 138篇 |
1981年 | 132篇 |
1980年 | 130篇 |
1979年 | 139篇 |
1978年 | 152篇 |
1977年 | 115篇 |
1976年 | 142篇 |
1975年 | 129篇 |
1974年 | 132篇 |
1973年 | 105篇 |
1972年 | 90篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
81.
A new algorithm/program has been elaborated for simultaneous processing of different sets of vapour–liquid equilibrium data. The program was tested with six binary hexane + isomeric pentanol systems, each of them measured at three different isobaric conditions and one isothermal system of tert-butyl-methyl-ether + 2-methyl-2-propanol measured at three different temperatures. The correlation uses the maximum likelihood method, taking into account real behaviour of vapour phase. The parameters obtained are valid within the whole temperature range of the data, and are consistent in comparison with those obtained from individual correlations of isobars or isotherms. Results are presented for the Wilson and NRTL equations. 相似文献
82.
The redox properties of the system Fe(tmphen)3(II/III) (tmphen=3,4,7,8-tetramethyl-1,10-phenanthroline) have been studied in the solvents nitromethane, acetonitrile, propanediol-1,2-carbonate, dimethylformamide, dimethylacetamide, dimethylsulfoxide and of the systems Fe(phen)3(II/III) (phen=1,10-phenanthroline) and Fe(niphen)3(II/III) (niphen=5-nitro-1,10-phenanthroline) in the solvents nitromethane, acetonitrile, propanediol-1,2-carbonate and acetone. The redox potentials of Fe(tmphen)3(II/III) are nearly independent of the solvent suggesting that the system might be used as a reference redox couple similar to the systems ferrocene/ferricinium or bisbiphenylchromium(0/I). In contrast the redox potentials of Fe(niphen)3(II/III) show a significant decrease with increasing donor number of the solvent which can be explained by nucleophilic attack of solvent molecules at the iron. It is shown that such a mechanism is consistent with the known solvent and salt effects on the kinetics of dissociation of ferroin and ferriin type complexes. 相似文献
83.
Ohne Zusammenfassung 相似文献
84.
85.
Kučinskaitė Agnė Pobłocka-Olech Loretta Krauze-Baranowska Mirosława Briedis Vitalis Savickas Aruñas Sznitowska Małgorzata 《平面色谱法杂志一现代薄层色谱法》2007,20(2):121-125
SPE and TLC have been used for qualitative and quantitative analysis of salidroside, rosavin, rosarin, and rosin in commercially available dry extracts from Rhodiola rosea roots. The best separation of all the compounds was achieved on silica gel TLC plates with ethyl acetate—methanol—water, 77 + 13 + 10 (v/v), as mobile phase. UV detection was performed at λ = 215 nm for salidroside and at λ= 245 nm for the rosavins (rosavin, rosarin, and rosin). Detection limits for salidroside and the rosavins were 90 ng and 60 ng per spot, respectively. Results from quantitative analysis confirmed the manufacturer’s declaration of the amounts of salidroside and the rosavins in the extracts.
相似文献86.
Ohne Zusammenfassung 相似文献
87.
The phase analysis of cryolite (Na3AlF6) and sodium metasilicate (Na2SiO3) was performed by thermal analysis. The eutectic system with a region of two immiscible substances at a concentration of Na2SiO3 between 42.8 and 46.3 mol‐% was identified and the eutectic temperature determined to (886±2) °C. Based on the results of mass‐loss measurements, it was assumed that the introduced Na2SiO3 reacts with Na3AlF6 due to the formation of some nonvolatile stable compounds. The stable reaction products were identified by X‐ray diffraction analysis and IR spectroscopy of the spontaneously cooled samples, which established the formation of NaF and stable amorphous aluminosilicate compounds. 相似文献
88.
Summary Kinetics of dehydration of equilibrium swollen poly(acrylic acid) hydrogel was investigated using methods of non-isothermal
thermal analysis. Methods of Kissinger, Coats-Redfern, Van Krevelen and Horowitz-Metzger were applied for determination the
kinetics parameters: activation energy (E), pre-exponent (lnA) as well as the kinetics model ƒ(69) for the process of hydrogel dehydration under different heating rates. An existence
of good agreement between determined values of kinetic parameters (Eand A), which were obtained applying different methods under the same heating rate. Functional relationship between changes of
kinetic parameters of dehydration and changes of heating rate was established. An existence of compensation effect is accepted
and explanation of compensation effect appearance during the hydrogel dehydration is suggested. 相似文献
89.
The paper deals with the problem of the outpatient administration of186Re-HEDP and153Sm-EDTMP for palliative therapy of bone metastases. The subsequent 6 hours stay of the treated patients in a department of nuclear medicine appears to be in compliance with regulations proposed in the Czech Republic as well as with ICRP recommendations. 相似文献
90.
R.R. Adžić D.N. Simić A.R. Despić D.M. Dražić 《Journal of Electroanalytical Chemistry》1975,65(2):587-601
It was demonstrated that some foreign metal monolayers formed by underpotential deposition have pronounced catalytic effects on the oxidation of formic acid on platinum. The explanation of these effects was sought within the framewor of existing data on the formic acid oxidation and the underpotential deposition. It was found that the catalytic effect of foreign metal monolayers originates in the decrease of hydrogen adsorption thus preventing the formation of the main poisoning species COH. At the same time these experiments confirm the previously postulated mechanism of formation of the poisoning species involving adsorbed hydrogen. 相似文献