全文获取类型
收费全文 | 38579篇 |
免费 | 2885篇 |
国内免费 | 1461篇 |
专业分类
化学 | 26294篇 |
晶体学 | 426篇 |
力学 | 1537篇 |
综合类 | 68篇 |
数学 | 4051篇 |
物理学 | 10549篇 |
出版年
2024年 | 68篇 |
2023年 | 464篇 |
2022年 | 958篇 |
2021年 | 1126篇 |
2020年 | 1092篇 |
2019年 | 1012篇 |
2018年 | 879篇 |
2017年 | 794篇 |
2016年 | 1359篇 |
2015年 | 1305篇 |
2014年 | 1551篇 |
2013年 | 2506篇 |
2012年 | 2934篇 |
2011年 | 3175篇 |
2010年 | 2047篇 |
2009年 | 1870篇 |
2008年 | 2563篇 |
2007年 | 2224篇 |
2006年 | 2174篇 |
2005年 | 1917篇 |
2004年 | 1589篇 |
2003年 | 1307篇 |
2002年 | 1260篇 |
2001年 | 850篇 |
2000年 | 777篇 |
1999年 | 630篇 |
1998年 | 412篇 |
1997年 | 356篇 |
1996年 | 474篇 |
1995年 | 358篇 |
1994年 | 340篇 |
1993年 | 332篇 |
1992年 | 256篇 |
1991年 | 223篇 |
1990年 | 226篇 |
1989年 | 176篇 |
1988年 | 139篇 |
1987年 | 124篇 |
1986年 | 94篇 |
1985年 | 122篇 |
1984年 | 92篇 |
1983年 | 65篇 |
1982年 | 84篇 |
1981年 | 88篇 |
1980年 | 45篇 |
1979年 | 62篇 |
1978年 | 52篇 |
1977年 | 48篇 |
1976年 | 55篇 |
1975年 | 47篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
102.
103.
Ivanisevic A McCumber KV Mirkin CA 《Journal of the American Chemical Society》2002,124(40):11997-12001
We describe a new combinatorial method for studying the exchange between solution adsorbates and nanoscale features within libraries generated via dip-pen nanolithography. Four different compounds, 1-octadecanethiol, 16-mercaptohexadecanoic acid, ferrocene (11-mercaptoundecyl), and ferrocene (11-mercapto-1-oxoundecyl), are studied on amorphous and single-crystal gold substrates. This series of adsorbates allows us to compare the exchange properties of patterns of nanoscale features as a function of composition, feature size, and type of underlying substrate. Moreover, these properties can be compared and contrasted with bulk SAM properties. The novel strategy provides not only a method for initiating site-specific exchange processes but also a way of extracting kinetic information about the rate of such processes in situ. 相似文献
104.
Reaction of trienes with α,β-unsaturated aldehydes produces bicyclic products via a tandem Diels-Alder/ene reaction. The adduct from tiglic aldehyde was converted into isoligularone by conversion to a furan followed by benzylic oxidation. 相似文献
105.
G. J. De Jong U. A. Th. Brinkman W. Th. Kok 《Journal of Radioanalytical and Nuclear Chemistry》1977,35(2):245-252
An investigation has been made on the system liquid anion-exchanger-Cd(II)-NCS−. The influence of the acidity and thiocyanate concentration of the aqueous phase on the extraction has been studied. Using
various methods of analysis, it has been shown that the complex anion present in the organic extracts is Cd(NCS)
4
2−
. Details are given concerning the removal of traces of Zn(II) from Cd(II)-containing solutions, and the quantitative separation
of Cd(II) from Cr(III). 相似文献
106.
Kang MS Kim JH Kim YJ Won J Park NG Kang YS 《Chemical communications (Cambridge, England)》2005,(7):889-891
The ionic conductivity of polymer electrolytes and their interfacial contact with dye-attached TiO2 particles were enhanced markedly by the addition of amorphous oligomer into polymer electrolytes, resulting in very high overall energy conversion efficiency. 相似文献
107.
Molecular dynamics simulation and analysis based upon the many-body potential energy landscape (PEL) are employed to characterize single molecule reorientation and structural relaxation, and their interrelation, in deeply supercooled liquid CS(2). The rotational mechanism changes from small-step Debye diffusion to sudden large angle reorientation (SLAR) as the temperature falls below the mode-coupling temperature T(c). The onset of SLAR is explained in terms of the PEL; it is an essential feature of low-T rotational dynamics, along with the related phenomena of dynamic heterogeneity and the bifurcation of slow and fast relaxation processes. A long trajectory in which the system is initially trapped in a low energy local minimum, and eventually escapes, is followed in detail, both on the PEL and in real space. During the trapped period, "return" dynamics occurs, always leading back to the trap. Structural relaxation is identified with irreversible escape to a new trap. These processes lead to weak and strong SLAR, respectively; strong SLAR is a clear signal of structural relaxation. Return dynamics involves small groups of two to four molecules, while a string-like structure composed of all the active groups participates in the escape. It is proposed that, rather than simple, nearly instantaneous, one-dimensional barrier crossings, relaxation involves activation of the system to the complex, multidimensional region on the borders of the basins of attraction of the minima for an extended period. 相似文献
108.
3,3′:4′,3″-Ter-1,2,5-thiadiazole, an useful oligoheterocyclic compound, has been accomplished in seven steps from 1-(5-methyl-3-isoxazolyl)ethanone or diethyl acetylenedicarboxylate using a synthetic utility of tetrasulfur tetranitride antimony pentachloride (S4N4·SbCl5) complex to make a 1,2,5-thiadiazole ring. 相似文献
109.
Stasko DJ Perzynski KJ Wasil MA Brodbeck JK Kirschbaum K Kim YW Lind C 《Inorganic chemistry》2004,43(13):3786-3788
The acid H(2)B(12)(OH)(12) can be isolated as a crystalline solid by protonation of the hydroxylated borane anion, B(12)(OH)(12)(2)(-). This acidic compound has low solubility in water, conducts protons in the solid state, and has thermal stability to a temperature of 400 degrees C. The conductivity mechanism is a Grotthuss mechanism with a low activation enthalpy (9-13 kcal/mol). This new acid represents an addition to the class of oxoacids, of which sulfuric and phosphoric acid are the most prominent examples. 相似文献
110.
Chi YS Jung YH Choi IS Kim YG 《Langmuir : the ACS journal of surfaces and colloids》2005,21(10):4669-4673
In this paper, we report surface-initiated d(A-T) polymerization by Taq DNA polymerase as a method for constructing DNA-tethered surfaces using an enzyme. The enzymatic polymerization was conducted successfully via two steps: tethering of oligo d(A-T)s onto the surface presenting carboxylic acids by amide coupling and surface-initiated polymerization using Taq DNA polymerase. In this enzymatic polymerization process, the design and construction of carboxylic acid-presenting surfaces were found to be an important factor: DNA growth did not occur on the gold surface coated only with the self-assembled monolayer (SAM) of 16-mercaptohexadecanoic acid (MHDA), but effectively proceeded on the surfaces presenting mixed SAMs of MHDA and 1-pentadecanethiol. The coupling of oligo d(A-T)s and the subsequent DNA polymerization reaction were characterized by polarized infrared external reflectance spectroscopy, ellipsometry, X-ray photoelectron spectroscopy, and atomic force microscopy. 相似文献