全文获取类型
收费全文 | 1796篇 |
免费 | 68篇 |
国内免费 | 13篇 |
专业分类
化学 | 1408篇 |
晶体学 | 31篇 |
力学 | 16篇 |
数学 | 89篇 |
物理学 | 333篇 |
出版年
2023年 | 8篇 |
2022年 | 10篇 |
2021年 | 21篇 |
2020年 | 31篇 |
2019年 | 31篇 |
2018年 | 24篇 |
2017年 | 15篇 |
2016年 | 45篇 |
2015年 | 42篇 |
2014年 | 39篇 |
2013年 | 76篇 |
2012年 | 91篇 |
2011年 | 124篇 |
2010年 | 59篇 |
2009年 | 61篇 |
2008年 | 106篇 |
2007年 | 109篇 |
2006年 | 103篇 |
2005年 | 84篇 |
2004年 | 105篇 |
2003年 | 77篇 |
2002年 | 57篇 |
2001年 | 49篇 |
2000年 | 37篇 |
1999年 | 36篇 |
1998年 | 27篇 |
1997年 | 15篇 |
1996年 | 22篇 |
1995年 | 18篇 |
1994年 | 21篇 |
1993年 | 16篇 |
1992年 | 21篇 |
1991年 | 16篇 |
1990年 | 18篇 |
1989年 | 12篇 |
1988年 | 14篇 |
1987年 | 20篇 |
1986年 | 17篇 |
1985年 | 27篇 |
1984年 | 16篇 |
1983年 | 17篇 |
1982年 | 12篇 |
1981年 | 14篇 |
1980年 | 11篇 |
1979年 | 15篇 |
1977年 | 8篇 |
1976年 | 10篇 |
1975年 | 10篇 |
1973年 | 8篇 |
1972年 | 8篇 |
排序方式: 共有1877条查询结果,搜索用时 15 毫秒
51.
52.
Cellulose/antimony(III) oxide composites, Cel/Sb(2)O(3), with oxide loadings of 1.7, 5.4, and 9.2 wt% were prepared by reacting the precursor SbCl(3) reagent with cellulose in dry ethanol solution. The reaction of the Lewis acid and the cellulose fibers occurred at the~amorphous domains of the biopolymer, increasing the crystallinity degree of the composite compared with that of the untreated cellulose. The scanning electron microscopy images and metal mapping for all samples showed that the oxide film layer uniformly covered the fiber surfaces with no detectable agglomerates of the oxide particles. The synchrotron X-ray diffraction patterns indicated that the antimony oxide film was obtained as a crystalline phase with orthorombic structure. The atomic ratios of O/Sb, determined by X-ray photoelectron spectroscopy, indicated that, for Cel/Sb(2)O(3) samples with 9.3 wt% loading, the fiber surface is nearly saturated by the oxide layer. The thermal stability of Cel/Sb(2)O(3) compared to that of untreated cellulose is practically unaffected. Copyright 2000 Academic Press. 相似文献
53.
Alfaya RV Fujiwara ST Gushikem Y Kholin YV 《Journal of colloid and interface science》2004,269(1):32-36
3-n-propylpyridiniumsilsesquioxane chloride polymer, abbreviated as SiPy+Cl-, was used to coat a porous silica gel, SiO2, surface to form the chemically modified solid SiO2/SiPy+Cl-. The resulting polymer film was well adhered to the surface and presented an ion exchange capacity of 0.74 mmol g(-1). Metal halides, MClz [M=Fe(III), Cu(II), and Zn(II)], were adsorbed by the modified solid from ethanol solutions as neutral species by forming the surface anionic complexes described by the equation: mSiO2/SiPy+Cl-+ MClz <=> (SiO2/SiPy+)m[MCl(z+m)]m-, where the [MCl(z+m)]m- species adsorbed on the surface are FeCl4-, ZnCl4(2-), and CuCl4(2-). Accurate estimates of the specific sorption capacities and the heterogeneous stability constants of the immobilized metal complexes were determined with the aid of computational procedures. 相似文献
54.
N-Acyl-α-amino acids are synthesized by the amidocarbonylation of allylic alcohols catalyzed by homogeneous binary systems which consist of cobalt carbonyl and rhodium (or iron or palladium) complexes. 相似文献
55.
56.
57.
A spectrophotometric flow-injection method for determining copper(II) has been developed. It is based on the catalytic effect of copper(II) on the oxidative coupling of N-phenyl-p-phenylenediamine with m-phenylenediamine in the presence of hydrogen peroxide. Pyridine and ammonia as activators increased the absorbance for the copper(II)-catalyzed coloration, and the dye formed was stabilized by adding a non-ionic surfactant. The working range of the method was 0.1-2.0 ng ml(-1) of cooper(II) with a relative standard deviation 2.4% at a sampling rate of 30 h(-1). Interference from iron(III) was effectively suppressed by citric acid. Copper in natural water samples can be determined easily. 相似文献
58.
Leesajakul W Nakano M Taniguchi A Handa T 《Colloids and surfaces. B, Biointerfaces》2004,34(4):253-258
Cubosomes are novel dispersed nanoparticles with bicontinuous cubic phases of monoolein in their interior. We investigated their disintegration process in plasma by in vitro and in vivo studies. Cubosomes were incubated with whole plasma or plasma components such as HDL, LDL, and albumin. The lypolysis study indicated lipolytic activity of whole plasma towards cubosomes. Gel filtration chromatography revealed that HDL, LDL and albumin interacted with cubosomes. HDL affected cubosomes’ integrity and gave rise to smaller particles which contained the components of both cubosomes and HDL. Upon incubation with LDL, cubosomes fused with LDL. Albumin was shown to take up monoolein out of the particles. Cubosomes were disintegrated by whole plasma as a result of the interaction with plasma components. It was concluded that in vivo observation of a long circulation time of a hydrophobic substance in cubosomes was due to the sustained behavior of cubosome remnant particles. 相似文献
59.
Hitoshi Kubota Yukitaka Murata Yoshitaka Ogiwara 《Journal of polymer science. Part A, Polymer chemistry》1973,11(2):485-492
The effects of swelling of the sample and polymerization solvents were studied for photo-induced graft copolymerization of vinyl monomers on cellulose. The graft copolymerization of methyl methacrylate (MMA) was activated by swelling of the sample or organic solvent-water solutions within a certain range of their concentrations. Though each organic solvent gave a maximum in per cent grafting and the number of grafts at about 25 vol-% concentration, the initiation reaction scarcely took place at 100% concentration; thus, the solvent itself is considered to have a negative effect. The solvents used in the experiments were all hydrophilic, such as methanol, acetone, and dioxane. The average molecular weight of the grafted PMMA differed in each solvent, indicating a different characteristic effect of solvent on the growing grafted polymer radicals. The presence of ferric ion as a sensitizer stimulated further the contributions of the sample swelling and the organic solvents to the copolymerization reaction. A similar effect was observed for styrene as for MMA, but not for acrylic acid and methacrylic acid. 相似文献
60.
Tojino M Uenoyama Y Fukuyama T Ryu I 《Chemical communications (Cambridge, England)》2004,(21):2482-2483
Free-radical carbonylation of omega-alkynylamines with tributyltin hydride gives a mixture of alpha-methylene lactams and alpha-stannylmethylene lactams. Nucleophilic addition of an internal amino group to the carbonyl group of alpha-ketenyl radicals is proposed as the cyclization step. The subsequent unusual 1,4-H shift from the resulting 1-hydroxyallyl radical, followed by elimination of the beta-tributyltin radical leads to the formation of alpha-methylene lactams. 相似文献