全文获取类型
收费全文 | 1008篇 |
免费 | 23篇 |
国内免费 | 9篇 |
专业分类
化学 | 809篇 |
晶体学 | 9篇 |
力学 | 12篇 |
数学 | 58篇 |
物理学 | 152篇 |
出版年
2022年 | 13篇 |
2021年 | 8篇 |
2020年 | 11篇 |
2019年 | 8篇 |
2018年 | 17篇 |
2017年 | 7篇 |
2016年 | 15篇 |
2015年 | 13篇 |
2014年 | 18篇 |
2013年 | 54篇 |
2012年 | 49篇 |
2011年 | 53篇 |
2010年 | 20篇 |
2009年 | 29篇 |
2008年 | 57篇 |
2007年 | 59篇 |
2006年 | 58篇 |
2005年 | 73篇 |
2004年 | 46篇 |
2003年 | 46篇 |
2002年 | 48篇 |
2001年 | 17篇 |
2000年 | 13篇 |
1999年 | 8篇 |
1998年 | 10篇 |
1997年 | 6篇 |
1996年 | 10篇 |
1995年 | 8篇 |
1994年 | 13篇 |
1993年 | 8篇 |
1992年 | 17篇 |
1991年 | 13篇 |
1990年 | 13篇 |
1989年 | 11篇 |
1988年 | 14篇 |
1987年 | 16篇 |
1986年 | 9篇 |
1985年 | 10篇 |
1984年 | 19篇 |
1983年 | 10篇 |
1982年 | 16篇 |
1980年 | 15篇 |
1979年 | 12篇 |
1978年 | 6篇 |
1977年 | 10篇 |
1976年 | 6篇 |
1975年 | 9篇 |
1974年 | 5篇 |
1973年 | 4篇 |
1971年 | 7篇 |
排序方式: 共有1040条查询结果,搜索用时 218 毫秒
61.
Yoshio Aso Shoji Nishiguchi Tetsuya Jigami Tetsuo Otsubo Fumio Ogura 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1):417-418
Several well-defined 3,4-thienylene-ethynylene oligomers with different chain lengths have been synthesized and characterized. X-Ray crystallographic analyses proved their unique, totally helical conformations. 相似文献
62.
Type I (α-) and II cleavages are two of the best known photochemical processes of alkanone.2 Extensive and intensive investigations have been done on both types of reactions in order to clarify the influence of structural changes on the reactivity, specificity, and efficiency of photoreactions of alkanones.3 The type I cleavage of medium-ring alkanones is believed to produce a radical pair, the fate of which will be determined by the ready formation of transition states for transfer of Ha, Hb, and recyclization. We now wish to report 相似文献
63.
64.
Yanting Song Katsuya Takatsuki Muneki Isokawa Tetsushi Sekiguchi Jun Mizuno Takashi Funatsu Shuichi Shoji Makoto Tsunoda 《Analytical and bioanalytical chemistry》2013,405(25):7993-7999
In this study, a fast and quantitative determination method for branched-chain amino acids (BCAAs), namely leucine, isoleucine, and valine, was developed using a pillar array column. A pillar array column with low-dispersion turns was fabricated on a 20?×?20-mm2 microchip using multistep ultraviolet photolithography and deep reactive ion etching. The BCAAs were fluorescently labeled with 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F), followed by reversed-phase separation on the pillar array column. The NBD derivatives of the three BCAAs and an internal standard (6-aminocaproic acid) were separated in 100 s. The calibration curves for the NBD-BCAAs had good linearity in the range of 0.4–20 μM, using an internal standard. The intra- and interday precisions were found to be in the ranges of 1.42–3.80 and 2.74–6.97 %, respectively. The accuracies for the NBD-BCAA were from 90.2 to 99.1 %. The method was used for the analysis of sports drink and human plasma samples. The concentrations of BCAAs determined by the developed method showed good agreements with those determined using a conventional high-performance liquid chromatography system. As BCAAs are important biomarkers of some diseases, these results showed that the developed method could be a potential diagnostic tool in clinical research. 相似文献
65.
Atsushi Tarui Shoji Kondo Kazuyuki Sato Masaaki Omote Hideki Minami Yoshihisa Miwa Akira Ando 《Tetrahedron》2013,69(5):1559-1565
A highly diastereoselective cross-coupling reaction of an α-bromo-α-fluoro-β-lactam with a wide range of aryl Grignard reagents was catalyzed by Ni/bis(oxazoline) in yields of up to 98%. The product was obtained diastereoselectively as an anti-isomer. This is the first successful α-arylation of an α-fluoro-β-lactam to produce diverse α-aryl-α-fluoro-β-lactams. 相似文献
66.
A mechanistic study was carried out for the asymmetric Michael addition reaction of malonates to enones catalyzed by a primary amino acid lithium salt to elucidate the origin of the asymmetric induction. A primary β-amino acid salt catalyst, O-TBDPS β-homoserine lithium salt, exhibited much higher enantioselectivity than that achieved with the corresponding catalysts derived from α- and γ-amino acids for this reaction. Detailed studies of the transition states with DFT calculations revealed that the lithium cation and carboxylate group of the β-amino acid salt catalyst have important roles in achieving high enantioselectivity in the Michael addition reaction of malonates to enones. 相似文献
67.
68.
69.
Takeo Yamaguchi Shin-Ichi Nakao Shoji Kimura 《Journal of polymer science. Part A, Polymer chemistry》1996,34(7):1203-1208
Using a plasma-induced graft polymerization technique, which is well known as a surface modification method, the grafted polymer was formed in pores of the porous material. This study examined the filling mechanism. Five thin porous films were sandwiched together, and employed as the substrate. The substrate was treated by plasma, and the change in surface tension and radical formation was measured for each sheet after the sheet was separated. The only surface on which surface-tension change was detected, was that of the sheet directly exposed to the plasma. Although plasma treatment made polymer radicals primarily on the outer surface of the sheet, the treatment also formed a few radicals inside the sheets. The radicals inside the sheets reacted with methylacrylate and grafted polymer formed in the pores. The location of grafted polymer depended on the balance between monomer diffusivity and reactivity. The grafting rate depended on which monomer solvent was used for the polymerization. Thus, the grafted membrane morphology could be controlled by varying the grating solvent composition. © 1996 John Wiley & Sons, Inc. 相似文献
70.
Electron beam treatment of lignite-burning flue gas with high concentrations of sulfur dioxide and water 总被引:5,自引:0,他引:5
Hideki Namba Shoji Hashimoto Okihiro Tokunaga Ryoji Suzuki 《Radiation Physics and Chemistry》1998,53(6):673-681
Experiments were carried out to investigate the removals of SO2 and NOx from simulated lignite-burning flue gas containing SO2 (4800 ppm), NO (320 ppm) and H2O (22%) by electron beam irradiation. Removal efficiencies of SO2 and NOx were achieved to reach 97 and 88% at 70°C, and 74 and 85% at 80°C, respectively, with the dose of 10.3 kGy without NH3 leakage. The higher removal efficiencies of SO2 and NOx were observed in simulated lignite-burning flue gas than in coal-fired flue gas containing 800 ppm of SO2, 225 ppm of NO and 7.5% H2O at the same treatment condition. The higher removal efficiencies were attributed to the higher concentrations of SO2, H2O, and added NH3. Simulation calculations indicated that the higher concentrations of these components enhance the effective radical reactions to oxidize NO to form NO2 with HO2 radical, and to oxidize SO2 to form SO3 with OH radical and O2. The reactions of NOx with N and NH2 radicals to produce N2 and N2O also promote the NOx removal. By-product was determined to be the mixture of (NH4)2SO4 and NH4NO3 containing a small amount of H2SO4. 相似文献