全文获取类型
收费全文 | 215篇 |
免费 | 9篇 |
专业分类
化学 | 143篇 |
晶体学 | 4篇 |
力学 | 2篇 |
数学 | 20篇 |
物理学 | 55篇 |
出版年
2023年 | 1篇 |
2022年 | 1篇 |
2021年 | 2篇 |
2020年 | 2篇 |
2019年 | 1篇 |
2018年 | 3篇 |
2017年 | 6篇 |
2016年 | 7篇 |
2015年 | 4篇 |
2014年 | 4篇 |
2013年 | 7篇 |
2012年 | 8篇 |
2011年 | 14篇 |
2010年 | 6篇 |
2009年 | 7篇 |
2008年 | 12篇 |
2007年 | 10篇 |
2006年 | 12篇 |
2005年 | 10篇 |
2004年 | 8篇 |
2003年 | 13篇 |
2002年 | 14篇 |
2001年 | 5篇 |
2000年 | 7篇 |
1999年 | 4篇 |
1998年 | 6篇 |
1997年 | 3篇 |
1996年 | 4篇 |
1995年 | 5篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1990年 | 1篇 |
1989年 | 5篇 |
1988年 | 2篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 4篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 3篇 |
1978年 | 1篇 |
1971年 | 3篇 |
1969年 | 1篇 |
排序方式: 共有224条查询结果,搜索用时 156 毫秒
171.
Kouki Matsubara Shoji Mima Takashi Oda Hideo Nagashima 《Journal of organometallic chemistry》2002,650(1-2):96-107
Novel isonitrile derivatives of a diruthenium carbonyl complex, (μ2,η3:η5-guaiazulene)Ru2(CO)5 (2), were synthesized by substitution of a CO ligand by an isonitrile, and were subjected to studies on thermal and photochemical haptotropic interconversion. Treatment of 2 (a 45:55 mixture of two haptotropic isomers, 2-A and 2-B) with RNC at room temperature resulted in coordination of RNC and alternation of the coordination mode of the guaiazulene ligand to form (μ2,η1:η5-guaiazulene)Ru2(CO)5(CNR), 5d–5f, [5d; R=tBu, 5e; 2,4,6-Me3C6H2, or 5f; 2,6-iPr2C6H3] in moderate to good yields. Thermal dissociation of a CO ligand from 5 at 60 °C resulted in quantitative formation of a desirable isonitrile analogue of 2, (μ2,η3:η5-guaiazulene)Ru2(CO)4(CNR), 4d–4f, [4d; R=tBu, 4e; 2,4,6-Me3C6H2, or 4f; 2,6-iPr2C6H3], as a 1:1 mixture of the two haptotropic isomers. A direct synthetic route from 2 to 4d–4f was alternatively discovered; treatment of 2 with one equivalent of RNC at 60 °C gave 4d–4f in moderate yields. All of the new compounds were characterized by spectroscopy, and structures of 5d (R=tBu) and 4d-A (R=tBu) were determined by crystallography. Thermal and photochemical interconversion between the two haptotropic isomers of 4d–4f revealed that the isomer ratios in the thermal equilibrium and in the photostatic state were in the range of 48:52–54:46. 相似文献
172.
Yoshiki Katayama Kazuhide Nita Masahide Ueda Hiroshi Nakamura Makoto Takagi Keihei Ueno 《Analytica chimica acta》1985
New crown ethers carrying a pendent phenolic chromophore were synthesized. These crown ethers, on dissociation of the phenolic proton, provide lipophilic anions which can extract alkali metal cations into 1,2-dichloroethane by forming highly-colored uncharged metal complexes. Structural effects on the extraction were studied for possible use of these crown ethers as extraction—spectrophotometric reagents selective for alkali metals. The following factors are discussed in detail: (i) nature of the crown ether ring (ring size. aza-crown or standard crown ether), (ii) nature of the pendent phenolic group, and (iii) geometry between the crown ether center and pendent phenolic group. 15-Crown-5 or smaller ring-sized reagents favored the extraction of lithium ion when the basicity of the pendent phenolate was relatively high and a six-membered “chelate” ring was possible for the phenolate and the crown ether-bound metal. 15-Crown-5 type reagents were sodium-selective when an eight-membered “chelate” ring was possible between the phenolate and the crown ether-bound metal. 18-Crown-6 type reagents were generally potassium-selective. However, these selectivities were not absolute, and other structural parameters, steric and conformational, must be considered to explain in detail the selectivities of the individual reagents. 相似文献
173.
A highly enantioselective (2Z)-alk-2-enylation of aldehydes was successfully achieved by an allyl-transfer reaction from a chiral allyl donor, which was easily obtained by separation of a diastereomeric mixture of the corresponding homoallylic alcohol gamma-adducts derived from (+)-isomenthone with alk-2-enylmagnesium chloride. [reaction: see text] 相似文献
174.
Ueno K Hata K Katakabe T Kondoh M Watanabe M 《The journal of physical chemistry. B》2008,112(30):9013-9019
The dispersion of silica nanoparticles made an ionic liquid, 1-ethyl-3-methyl imidazolium bis(trifluoromethanesulfonyl)amide ([C(2)mim][NTf(2)]), gelled even by the addition of 2-3 wt %, due to the formation of interconnected particulate silica networks in [C(2)mim][NTf(2)]. The ionic transport and viscoelastic properties of these nanocomposite ion gels were investigated in relation to the microstructure. Despite their solid-like behavior, the nanocomposite ion gels exhibited a high ionic conductivity of approximately 10(-2) S cm(-1) at 30 degrees C, which is comparable to that of neat [C(2)mim][NTf(2)]. Intriguing viscoelastic responses, such as shear-thinning and shear-induced sol-gel transitions, were found in all of the nanocomposite ion gels. By adjusting the silica concentration, the elastic modulus ( G') could be precisely controlled in a range of more than 3 orders of magnitude and reached approximately 10(6) Pa without a considerable decrease in the ionic conductivity; the characteristic viscoelastic response was also maintained. For the aggregation mechanism in [C 2 mim][NTf(2)], the reaction-limited cluster aggregation (RLCA) model was proposed by rheology and light scattering measurements. 相似文献
175.
Hideaki Tsubaki Atsushi Sugawara Hiroyuki Takeda Bobak Gholamkhass Kazuhide Koike Osamu Ishitani 《Research on Chemical Intermediates》2007,33(1-2):37-48
Photocatalysis of biscarbonylrhenium complexes cis,trans-[Re(dmbpy)(CO)2(PR3) (PR′3)]+ (dmbpy=4,4′-dimethyl-2,2′-bipyridine: R, R′=Ph (1a +); p-FPh (1b +); R=Ph, R′=OEt (1c +); R, R′=O-i-Pr (1d +)) is reported for the first time. The rhenium complexes with two triarylphosphine ligands (1a +, 1b +) efficiently photocatalyzed CO2 reduction with triethanolamine as a sacrificial donor. On the other hand, the complexes with one or two trialkylphosphite ligand(s) (1c +, 1d +) had low photocatalytic abilities under the same reaction conditions. 相似文献
176.
Ma Q Xu Z Schroeder BR Sun W Wei F Hashimoto S Konishi K Leitheiser CJ Hecht SM 《Journal of the American Chemical Society》2007,129(41):12439-12452
177.
Ueno K Inaba A Kondoh M Watanabe M 《Langmuir : the ACS journal of surfaces and colloids》2008,24(10):5253-5259
The colloidal stability of bare and poly(methyl methacrylate) (PMMA)-grafted silica nanoparticles was studied in 1-alkyl-3-methylimidazolium ([C(n)mim])-based ionic liquids (ILs) with different anionic structures. The theoretical estimation of the colloidal interaction between monodispersed bare silica particles by using the Derjaguin-Landau-Verwey-Overbeek theory indicates that bare silica particles cannot be stabilized and they rapidly form aggregates in all the ILs used in this study. The instability of bare silica particles was experimentally confirmed by dynamic light scattering measurement and in situ transmission electron microscopy observations by utilizing the negligible vapor pressure of ILs. This evidence suggests that electrostatic stabilization is inefficient in ILs because of the high ionic atmosphere and the resulting surface-charge screening. The PMMA-grafted silica particles exhibited long-term colloidal stability in [C(4)mim][PF(6)] and [C(n)mim][NTf(2)], which are compatible with the grafted PMMA. On the other hand, the PMMA-grafted particles could not be stabilized in [C 4mim][BF 4] due to the poor solubility of the grafted PMMA in the IL. Effective steric stabilization is important for obtaining stable colloidal particles in ILs. 相似文献
178.
Ge L Nagai K Gu Z Shimada Y Nishimura H Miyanaga N Izawa Y Mima K Norimatsu T 《Langmuir : the ACS journal of surfaces and colloids》2008,24(18):10402-10406
Low-density tin dioxide (SnO2) is required for radiating monochromatic extreme ultraviolet (EUV) light with low debris and high conversion efficiency from a laser. In this paper, tin dioxide nanoparticle hollow microcapsules were successfully fabricated by a layer-by-layer template technique. The obtained capsules have a rougher surface (30 nm in rms) compared to the freshly prepared polyelectrolyte capsules. Based on the X-ray diffraction (XRD) results, the tin dioxide nanoparticles well maintained their size after they were assembled on the capsules' surfaces. In order to remove the polymer template, a heat treatment was introduced, and after the heat treatment the capsule sizes shrank about 71% (the average size was from 4.9 to 3.5 mum), and the obtained capsules maintained their round shape after water evaporation. The narrowest bandwidth at the 13.5 nm emission in the EUV region was observed when the capsules were irradiated by a CO2 laser with an intensity of 2.9 x 10(10) W/cm (2). 相似文献
179.
Kazuhide NAKAJO 《数学物理学报(B辑英文版)》2017,37(2):342-354
Let C be a nonempty closed convex subset of a 2-uniformly convex and uniformly smooth Banach space E and {A_n}_(n∈N) be a family of monotone and Lipschitz continuos mappings of C into E~*. In this article, we consider the improved gradient method by the hybrid method in mathematical programming [10] for solving the variational inequality problem for{A_n} and prove strong convergence theorems. And we get several results which improve the well-known results in a real 2-uniformly convex and uniformly smooth Banach space and a real Hilbert space. 相似文献
180.
Kazuhide Kusakabe Katsumi Kishino Akihiko Kikuchi Takayuki Yamada Daisuke Sugihara Shinich Nakamura 《Journal of Crystal Growth》2001,230(3-4):387-391
High quality GaN layer was obtained by insertion of high temperature grown AlN multiple intermediate layers with migration enhanced epitaxy method by the RF-plasma assisted molecular beam epitaxy on (0 0 01) sapphire substrates. The propagating behaviors of dislocations were studied, using a transmission electron microscope. The results show that the edge dislocations were filtered at the AlN/GaN interfaces. The bending propagation of threading dislocations in GaN above AlN interlayers was confirmed. Thereby, further reduction of dislocations was achieved. Dislocation density being reduced, the drastic increase of electron mobility to 668 cm2/V s was obtained at the carrier density of 9.5×1016 cm−3 in Si doped GaN layer. 相似文献