全文获取类型
收费全文 | 8438篇 |
免费 | 200篇 |
国内免费 | 2篇 |
专业分类
化学 | 5060篇 |
晶体学 | 171篇 |
力学 | 158篇 |
数学 | 1187篇 |
物理学 | 2064篇 |
出版年
2022年 | 188篇 |
2021年 | 247篇 |
2020年 | 132篇 |
2019年 | 156篇 |
2018年 | 165篇 |
2017年 | 160篇 |
2016年 | 296篇 |
2015年 | 215篇 |
2014年 | 299篇 |
2013年 | 679篇 |
2012年 | 431篇 |
2011年 | 492篇 |
2010年 | 375篇 |
2009年 | 338篇 |
2008年 | 398篇 |
2007年 | 386篇 |
2006年 | 322篇 |
2005年 | 272篇 |
2004年 | 257篇 |
2003年 | 247篇 |
2002年 | 186篇 |
2001年 | 149篇 |
2000年 | 136篇 |
1999年 | 95篇 |
1998年 | 103篇 |
1997年 | 78篇 |
1996年 | 78篇 |
1995年 | 101篇 |
1994年 | 63篇 |
1993年 | 43篇 |
1992年 | 74篇 |
1991年 | 48篇 |
1990年 | 69篇 |
1989年 | 58篇 |
1988年 | 78篇 |
1987年 | 56篇 |
1986年 | 66篇 |
1985年 | 98篇 |
1984年 | 107篇 |
1983年 | 67篇 |
1982年 | 65篇 |
1981年 | 70篇 |
1980年 | 84篇 |
1979年 | 58篇 |
1978年 | 64篇 |
1977年 | 67篇 |
1976年 | 66篇 |
1975年 | 51篇 |
1974年 | 47篇 |
1973年 | 44篇 |
排序方式: 共有8640条查询结果,搜索用时 31 毫秒
811.
J. Kierzek B. Małożewska-Bućko P. Bukowski J. L. Parus A. Ciurapiński S. Zaraś B. Kunach K. Wiland 《Journal of Radioanalytical and Nuclear Chemistry》1999,240(1):39-45
Gamma-ray spectrometry (GS), energy dispersive X-ray fluorescence (EDXRF) analysis methods and wavelength dispersive X-ray
fluorescence (WDXRF) were applied for the studies of some coal components, e.g., sulphur, light and heavy metal element concentrations
and naturally occurring radioactive isotope contents. Hundred fifty coal samples originating mostly from eight different coal
mines from Upper Silesian Coal Basin and 150 samples of ash obtained from these coal samples in laboratory by total combustion
at final temperature of 820°C, were analyzed. Such comparitive analyses can be helpful in selection of most suitable kind
of coal for burning in electrical power and heat plants to minimize the environmental pollution. 相似文献
812.
The synthesis of both enantiomers of TEI-9826 has been accomplished in seven steps with an overall yield of 44% starting from diastereomeric camphor protected 3-[(dimethoxyphosphoryl)methyl]-4,5-dihydroxycyclopent-2-enones. The key steps include a fully diastereoselective hydrogenation of the endocyclic carbon–carbon double bond in the cyclopentenone ring controlled with a chiral diol moiety and the conversion of the latter into a new transposed olefinic bond. 相似文献
813.
Marcin Płosiński Tomasz Laskowski Paweł Sowiński Jan Pawlak 《Magnetic resonance in chemistry : MRC》2012,50(12):818-822
The absolute configurations of all the stereogenic centers of the antibiotic mycoheptin A2 were established upon previously elaborated general procedure, consisting of DQF‐COSY, NOESY, ROESY, HSQC and HMBC experiments as major tools. The structure of mycoheptin A2 without stereochemistry of its aglycone has been reported before. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
814.
Piotr Gwiazda Piotr Minakowski Aneta Wróblewska-Kamińska 《Central European Journal of Mathematics》2012,10(6):2019-2032
We consider a strongly nonlinear monotone elliptic problem in generalized Orlicz-Musielak spaces. We assume neither a ??2 nor ?2-condition for an inhomogeneous and anisotropic N-function but assume it to be log-H?lder continuous with respect to x. We show the existence of weak solutions to the zero Dirichlet boundary value problem. Within the proof the L ??-truncation method is coupled with a special version of the Minty-Browder trick for non-reflexive and non-separable Banach spaces. 相似文献
815.
Mieczysław Borowiecki Katarzyna Jesse-Józefczyk Elżbieta Sidorowicz 《Discrete Mathematics》2011,311(8-9):732-737
In this paper we will consider acyclic bipartition of the vertices of graphs, where acyclic means that the edges whose endpoints are in different parts of the partition induce a forest. We will require that the vertices belonging to the same partition induce graphs from particular class. We will search for acyclic bipartitions of cubic and subcubic graphs. 相似文献
816.
817.
Wojciech Kiciński Mateusz Szala Marcin Nita 《Journal of Sol-Gel Science and Technology》2011,58(1):102-113
The impact of solvent composition as well as inorganic salt content and type on carbon xerogel structure was investigated.
Carbon xerogels were derived from the sol–gel polycondensation of resorcinol with furfural in a water–methanol–inorganic salt
solution. As inorganic salts, NaCl, NH4ClO4 and FeCl3 were used. In order to conduct an accurate examination of the carbon xerogel structures and textures, inorganic salts were
removed prior to carbonization. The xerogel structures can be tailored according to the water/methanol ratio and, to a lesser
extent, according to the inorganic salt content and type in the starting solution. As a result, a significant amount of salt
can be introduced to the gel network of the desired structure. The morphology and physical properties of the organic xerogels,
carbon xerogels and their composites were characterized by means of SEM, N2 sorption and XRD. It was found that samples derived from mixtures with FeCl3 manifest well developed mesoporosity and depleated microporosity in comparison to samples prepared from mixtures with NaCl
and NH4ClO4. Iron ions chemically bond to the xerogel matrix and cause its partial graphitization during the carbonization process, resulting
in enhanced mesoporosity. 相似文献
818.
819.
Ohne Zusammenfassung 相似文献
820.
Density and viscosity were determined for the binary mixtures containing the ionic liquid 1-butyl-3-methylimidazolium thiocyanate
([BMIM][SCN]) and 1-alcohols (1-butanol, 1-pentanol and 1-hexanol) at six temperatures (298.15, 308.15, 318.15, 328.15, 338.15
and 348.15) K and ambient pressure. The density and viscosity correlation for these systems was tested by an empirical second-order
polynomial and by the Vogel-Fucher-Tammann equation in wide ranges of temperatures. Excess molar volumes were described by
the Redlich-Kister polynomial expansions. The density and viscosity variations with composition were described by polynomials.
A qualitative analysis of the trend of the properties with solvent and temperature was performed. The obtained results indicate
that ionic liquid interactions with 1-alcohols are strongly dependent on the special trend of packing of this ionic liquid
into hydroxylic solvents. As previously observed, an increase of the 1-alcohol carbon-chain length leads to lower interactions
on mixing.
Electronic Supplementary Material The online version of this article () contains supplementary material, which is available to authorized users. 相似文献