全文获取类型
收费全文 | 1298篇 |
免费 | 49篇 |
国内免费 | 6篇 |
专业分类
化学 | 908篇 |
晶体学 | 19篇 |
力学 | 16篇 |
数学 | 41篇 |
物理学 | 221篇 |
无线电 | 148篇 |
出版年
2022年 | 5篇 |
2021年 | 14篇 |
2020年 | 12篇 |
2019年 | 16篇 |
2018年 | 13篇 |
2017年 | 5篇 |
2016年 | 30篇 |
2015年 | 21篇 |
2014年 | 32篇 |
2013年 | 67篇 |
2012年 | 64篇 |
2011年 | 71篇 |
2010年 | 39篇 |
2009年 | 50篇 |
2008年 | 56篇 |
2007年 | 62篇 |
2006年 | 65篇 |
2005年 | 71篇 |
2004年 | 61篇 |
2003年 | 48篇 |
2002年 | 64篇 |
2001年 | 38篇 |
2000年 | 26篇 |
1999年 | 21篇 |
1998年 | 24篇 |
1997年 | 13篇 |
1996年 | 20篇 |
1995年 | 26篇 |
1994年 | 19篇 |
1993年 | 9篇 |
1992年 | 20篇 |
1991年 | 17篇 |
1990年 | 17篇 |
1989年 | 12篇 |
1988年 | 9篇 |
1987年 | 10篇 |
1986年 | 5篇 |
1985年 | 21篇 |
1984年 | 27篇 |
1983年 | 10篇 |
1982年 | 13篇 |
1981年 | 18篇 |
1980年 | 15篇 |
1979年 | 10篇 |
1978年 | 17篇 |
1977年 | 13篇 |
1976年 | 10篇 |
1975年 | 6篇 |
1973年 | 11篇 |
1968年 | 6篇 |
排序方式: 共有1353条查询结果,搜索用时 15 毫秒
1.
Naoto Takase Junpei Kuwabara Seong Jib Choi Takeshi Yasuda Liyuan Han Takaki Kanbara 《Journal of polymer science. Part A, Polymer chemistry》2015,53(4):536-542
The Pd‐catalyzed polycondensation of 4‐octylaniline with various dibromoarylenes was carried out under microwave heating. Microwave heating led to a decrease in the reaction time and an increase in the molecular weight of the polymers as compared to conventional heating. Microwave heating also allowed the catalyst loading to be reduced to 1 mol %, yielding polymerization results that were comparable to those under conventional heating and 5 mol % catalyst. Investigations regarding field‐effect transistors and organic photovoltaic cells using the obtained poly(arylamine) with azobenzene units revealed that increasing the molecular weight of the polymer led to improved device performance, including hole mobility and power conversion efficiency. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 536–542 相似文献
2.
Y. Yamamoto H. Kidooka Y. Honda S. Yasuda 《International Journal of Infrared and Millimeter Waves》1995,16(3):579-589
A novel method using small neon glow lamps with electrodes is developed for measuring intense microwave field patterns. When the lamp axis coincide with the electric field direction, the lamp discharge starts at the feeblest microwave electric field strength. Therefore, the lamp axis shows the field direction and the discharge starting indicates the field strength. The field strength for starting the microwave discharge is less than the strength for AC discharge, because of its low loss discharge mechanism. In the experiments using a microwave oven, it has been demonstrated again comparing with the simulated results that the method is able to use for measuring the intense electric field strength and direction. 相似文献
3.
4.
K. Yasuda Y. Tomita Y. Masuda T. Ishiguro Y. Kawauchi H. Morishita Y. Agata 《Journal of Electronic Materials》2002,31(7):785-790
Iodine doping of CdTe layers grown on (100) GaAs by metal-organic vapor phase epitaxy (MOVPE) was studied using diethyltelluride
(DETe) and diisopropyltelluride (DiPTe) as tellurium precursors and ethyliodine (EI) as a dopant. Electron densities of doped
layers increased gradually with decreasing the growth temperature from 425°C to 325°C. Doped layers grown with DETe had higher
electron densities than those grown with DiPTe. When the hot-wall temperature was increased from 200°C to 250°C at the growth
temperature of 325°C, doped layers grown with DETe showed an increase of the electron density from 3.7×1016 cm−3 to 2.6×1018 cm−3. On the other hand, such an increase of the electron density was not observed for layers grown with DiPTe. The mechanisms
for different doping properties for DETe and DiPTe were studied on the basis of the growth characteristics for these precursors.
Higher thermal stability of DETe than that of DiPTe was considered to cause the difference of doping properties. With increasing
the hot-wall temperature from 200°C to 250°C, the effective ratio of Cd to Te species on the growth surface became larger
for layers grown with DETe than those grown with DiPTe. This was considered to decrease the compensation of doped iodine and
to increase the electron density of layers grown with DETe. The effective ratio of Cd to Te species on the growth surface
also increased with decreasing growth temperature. This was considered to increase the electron density with decreasing growth
temperature. 相似文献
5.
Yasuhiko Iwasaki Keiko Shimakata Nobuyuki Morimoto Kimio Kurita 《Journal of polymer science. Part A, Polymer chemistry》2003,41(1):68-75
To obtain a hydrogel‐like elastic membrane, we prepared semi‐interpenetrating polymer networks (IPNs) by the radical polymerization of methacrylates such as 2‐methacryloyloxyethyl phosphorylcholine (MPC), 2‐hydroxyethylmethacrylate, and triethyleneglycol dimethacrylate diffused into segmented polyurethane (SPU) membranes swollen with a monomer mixture. The values of Young's modulus for the hydrated semi‐IPN membranes were less than that for an SPU membrane because of higher hydration, but they were much higher than that for a hydrated MPC polymer gel (non‐SPU). According to a thermal analysis, the MPC polymer influenced the segment association of SPU. The diffusion coefficient of 8‐anilino‐1‐naphthalenesulfonic acid sodium salt from the semi‐IPN membrane could be controlled with different MPC unit concentrations in the membrane, and it was about 7 × 102 times higher than that of the SPU membrane. Fibroblast cell adhesion on the semi‐IPN membrane was effectively reduced by the MPC units. We concluded that semi‐IPNs composed of the MPC polymer and SPU may be novel polymer materials possessing attractive mechanical, diffusive‐release, and nonbiofouling properties. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 68–75, 2003 相似文献
6.
Kazuhiko Matsumoto Tetsuya Tsuda Toshiyuki Nohira Rika Hagiwara Yasuhiko Ito Osamu Tamada 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(3):m186-m187
In the title complex, (C6H11N2)3[LaCl6], centrosymmetric octahedral hexachlorolanthanate anions are located at the corners and face‐centers of the monoclinic unit cell. The ring H atoms of the cations interact with the Cl atoms of the anions via hydrogen bonding, and bifurcation of the hydrogen bonding is observed. Cation–cation interactions via hydrogen bonding between the ring H atoms and π‐electrons of aromatic rings are also observed as in other imidazolium salts. 相似文献
7.
Polymer particles coated with hydroxyapatite were prepared by treating Pd0 immobilized polystyrene-co-acrylic acid particles in aqueous CaCl2 and NaH2PO2 solutions. Hydroxyapatite coating took place at neutral to alkaline pH conditions, and the homogeneous growth of the hydroxyapatite layer on the surface of polymer particles was observed at relatively low temperature (30-50 degrees C). The thickness of the hydroxyapatite layer increased with reaction time. Copyright 1999 Academic Press. 相似文献
8.
Distribution of polymer deposition in an inductively coupled rf discharge system is studied as a function of level of discharge power with acetylene and styrene as monomers. When a fixed flow rate is used, the discharge power has a relatively small effect on the pattern of distribution of polymer deposition as long as values of W/FM, where W is discharge wattage, F is flow rate, and M is molecular weight of monomer, are maintained above a critical level to maintain full glow in the reaction tube. It has been shown that plasma polymerization of two monomers which have different molecular weights can be compared in a fair manner by selecting conditions to yield similar value of W/FM. 相似文献
9.
Toshio Masuoka H. Yasuda 《Journal of polymer science. Part A, Polymer chemistry》1981,19(11):2937-2946
Plasma polylmerization occurs in plasmas surrounded by surfaces and polymer formation is one of the complicated interactions that take place between active species and molecules which constitute surfaces and gas phases. Effects of reactor wall, substrate materials, flow rate, and discharge power on polymer formation, and properties of polymer deposits were investigated by ESCA, IR (infrared) spectroscopy, and the measurement of system pressure. The effect of surface is important at the initial stage of plasma polymerization which can be easily detected by the system pressure change; however, integrated properties such as IR spectroscopy and the deposition rate show the effect in a less pronounced manner. ESCA, which reflects the properties of surface (approximately 20 A? in depth), showed the effect of surface in an even less sensitive manner. The amount and properties (including the effects of surfaces) are dependent on plasma polymerization parameter W/FM(W, wattage; F, volume flow rate; and M, molecualar weight of monomer) and the location of deposition within a reactor. IR and ESCA data clearly showed the dependence of polymer properties on W/FM; i.e., increase of W and decrease of M to be equivalent. When all these factors were kept under control, the reproducibility of plasma polymerization was found to be excellent. 相似文献
10.
Vaporization and thermal decomposition of Cr, Mn, Fe, Co, Ni and Cu salts were investigated by measuring the absorption spectra observed when aqueous solutions of these salts were heated in the carbon tube atomizer. Gaseous metal halides are vaporized in the atomizer at temperatures above 300–500° C. SO2 and NO are produced by thermal decomposition of metal sulfates and nitrates, respectively. The vaporization of metal halides is also confirmed by the spectra for solutions of metals in hydrochloric acid and for mixtures of metal nitrates and ammonium halides. 相似文献