全文获取类型
收费全文 | 850篇 |
免费 | 30篇 |
国内免费 | 7篇 |
专业分类
化学 | 589篇 |
晶体学 | 3篇 |
力学 | 18篇 |
数学 | 81篇 |
物理学 | 196篇 |
出版年
2022年 | 15篇 |
2021年 | 7篇 |
2020年 | 15篇 |
2019年 | 8篇 |
2018年 | 12篇 |
2017年 | 7篇 |
2016年 | 17篇 |
2015年 | 9篇 |
2014年 | 22篇 |
2013年 | 36篇 |
2012年 | 37篇 |
2011年 | 54篇 |
2010年 | 21篇 |
2009年 | 12篇 |
2008年 | 35篇 |
2007年 | 55篇 |
2006年 | 57篇 |
2005年 | 36篇 |
2004年 | 43篇 |
2003年 | 39篇 |
2002年 | 13篇 |
2001年 | 15篇 |
2000年 | 9篇 |
1999年 | 7篇 |
1998年 | 7篇 |
1997年 | 11篇 |
1996年 | 14篇 |
1993年 | 7篇 |
1992年 | 8篇 |
1991年 | 10篇 |
1990年 | 12篇 |
1989年 | 6篇 |
1988年 | 11篇 |
1986年 | 8篇 |
1985年 | 8篇 |
1984年 | 8篇 |
1983年 | 11篇 |
1982年 | 13篇 |
1981年 | 6篇 |
1980年 | 9篇 |
1979年 | 10篇 |
1978年 | 9篇 |
1977年 | 16篇 |
1976年 | 19篇 |
1975年 | 20篇 |
1974年 | 9篇 |
1973年 | 8篇 |
1971年 | 7篇 |
1969年 | 5篇 |
1932年 | 7篇 |
排序方式: 共有887条查询结果,搜索用时 0 毫秒
881.
882.
Zhang H Tumarkin E Peerani R Nie Z Sullan RM Walker GC Kumacheva E 《Journal of the American Chemical Society》2006,128(37):12205-12210
We report a microfluidic approach to generating capsules of biopolymer hydrogels. Droplets of an aqueous solution of a biopolymer were emulsified in an organic phase comprising a cross-linking agent. Polymer gelation was achieved in situ (on a microfluidic chip) by diffusion-controlled ionic cross-linking of the biopolymer, following the transfer of the cross-linking agent from the continuous phase to the droplets. Gelation was quenched by collecting particles in a large pool of cross-linking agent-free liquid. The structure of microgels (from capsules to gradient microgels to particles with a uniform structure) was controlled by varying the time of residence of droplets on the microfluidic chip and the concentration of the cross-linking agent in the continuous phase. We demonstrated the encapsulation of a controlled number of polystyrene beads in the microgel capsules. The described approach was applied to the preparation of capsules of several polysaccharides such as alginate, kappa-carrageenan, and carboxymethylcellulose. 相似文献
883.
The syntheses of three new diamide-linked γ-cyclodextrin dimers joined by substitution at either a glucopyranose C6A or C3A carbon are reported. The syntheses involve the reaction of either C6A or C3A amino-substituted γ-cyclodextrin with bis(4-nitrophenyl)succinate to form succinamide linked γ-cyclodextrin dimers or reaction of C6A azide-substituted γ-cyclodextrin with carbon dioxide to form a urea linked γ-cyclodextrin dimer. 相似文献
884.
Chen P Zhou X Shen H Andoy NM Choudhary E Han KS Liu G Meng W 《Chemical Society reviews》2010,39(12):4560-4570
This tutorial review covers recent developments in using single-molecule fluorescence microscopy to study nanoscale catalysis. The single-molecule approach enables following catalytic and electrocatalytic reactions on nanocatalysts, including metal nanoparticles and carbon nanotubes, at single-reaction temporal resolution and nanometer spatial precision. Real-time, in situ, multiplexed measurements are readily achievable under ambient solution conditions. These studies provide unprecedented insights into catalytic mechanism, reactivity, selectivity, and dynamics in spite of the inhomogeneity and temporal variations of catalyst structures. Prospects, generality, and limitations of the single-molecule fluorescence approach for studying nanocatalysis are also discussed. 相似文献
885.
The stability (formation) constants of the binary Cu(I)-CN− complexes have been measured in five aqueous mixtures containing from 10% to 70% v/v acetonitrile (MeCN) by glass electrode potentiometry at 25 °C and an ionic strength of l M (NaClO4). The constants show monotonic increases with MeCN concentration, the changes being greatest for the higher order complexes, consistent with the unfavourable solvation of CN − in these mixtures. The sparing solubility of CuCN(s) prevented determination of the stability constant for CuCN 0 (soln.) at low MeCN concentrations. 相似文献
886.
Dr. Nicolas P. Martin Enric Petrus Dr. Mireia Segado Ana Arteaga Dr. Lev N. Zakharov Dr. Carles Bo Dr. May Nyman 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(45):10580-10584
Group V Nb-polyoxometalate (Nb-POM) chemistry generally lacks the elegant pH-controlled speciation exhibited by group VI (Mo, W) POM chemistry. Here three Nb-POM clusters were isolated and structurally characterized; [Nb14O40(O2)2H3]14−, [((UO2)(H2O))3Nb46(UO2)2O136H8(H2O)4]24−, and [(Nb7O22H2)4(UO2)7(H2O)6]22−, that effectively capture the aqueous Nb-POM species from pH 7 to pH 10. These Nb-POMs illustrate a reaction pathway for control over speciation that is driven by counter-cations (Li+) rather than pH. The two reported heterometallic POMs (with UO22+ moieties) are stabilized by replacing labile H2O/HO−Nb=O with very stable O=U=O. The third isolated Nb-POM features cis-yl-oxos, prior observed only in group VI POM chemistry. Moreover, with these actinide-heterometal contributions to the burgeoning Nb-POM family, it now transects all major metal groups of the periodic table. 相似文献
887.
In this study, six samples of commercial poly(vinylidene fluoride) are investigated. Dynamic and steady-state shear flow experiments are carried out in the melt state in order to relate their rheological behaviour to their molecular weight distributions. This rheological investigation is performed through the use of some simple parameters related to the viscosity, elasticity and relaxation times. Plots of flow curves in reduced coordinates are used to confirm the above results. 相似文献