全文获取类型
收费全文 | 1284篇 |
免费 | 127篇 |
国内免费 | 3篇 |
专业分类
化学 | 1182篇 |
晶体学 | 16篇 |
力学 | 9篇 |
数学 | 28篇 |
物理学 | 179篇 |
出版年
2023年 | 15篇 |
2022年 | 27篇 |
2021年 | 41篇 |
2020年 | 38篇 |
2019年 | 62篇 |
2018年 | 50篇 |
2017年 | 29篇 |
2016年 | 51篇 |
2015年 | 57篇 |
2014年 | 62篇 |
2013年 | 110篇 |
2012年 | 135篇 |
2011年 | 137篇 |
2010年 | 57篇 |
2009年 | 38篇 |
2008年 | 91篇 |
2007年 | 71篇 |
2006年 | 48篇 |
2005年 | 50篇 |
2004年 | 43篇 |
2003年 | 29篇 |
2002年 | 28篇 |
2001年 | 7篇 |
2000年 | 8篇 |
1999年 | 10篇 |
1998年 | 6篇 |
1997年 | 5篇 |
1995年 | 7篇 |
1994年 | 5篇 |
1993年 | 4篇 |
1992年 | 5篇 |
1990年 | 7篇 |
1989年 | 3篇 |
1988年 | 8篇 |
1987年 | 3篇 |
1986年 | 4篇 |
1985年 | 5篇 |
1984年 | 3篇 |
1980年 | 2篇 |
1979年 | 7篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1975年 | 7篇 |
1974年 | 4篇 |
1971年 | 2篇 |
1970年 | 2篇 |
1969年 | 3篇 |
1968年 | 2篇 |
1967年 | 5篇 |
1966年 | 2篇 |
排序方式: 共有1414条查询结果,搜索用时 31 毫秒
951.
Masayuki Kirihara Katsumi Yoshida Takuya Noguchi Sayuri Naito Nobuchika Matsumoto Yukinori Ema Motoya Torii Yuki Ishizuka Ikuo Souta 《Tetrahedron letters》2010,51(28):3619-3622
The aerobic oxidation of ditertiary glycols catalyzed by oxytrichlorovanadium resulted in carbon-carbon bonds cleavage producing the ketones efficiently. 相似文献
952.
PZT films with different microstructure and Zr:Ti ratios were fabricated on ITO/glass and platinized silicon wafer substrates
by dip-coating. A dense film of 2% porosity and a porous film of 19% porosity were obtained by repetition of thin and thick
coatings, respectively. Development of pores during heating the film was examined and heating process factors were investigated.
In the film fabricated on ITO/glass substrates, an existence of non-perovskite and low permittivity layer was confirmed by
measurement of film thickness dependence of the dielectric constant. Among the films studied, the film with molar composition
of Ti:Zr = 5:5 exhibited the largest dielectric constant and apparent piezoelectric coefficient, d
33, though the values were small. Apparent piezoelectric coefficients of d
33 and g
33 of the porous films were larger than those of the dense films. 相似文献
953.
We introduce the status of the 300 MeV electron linear accelerator used for radioanalytical studies at Tohoku University.
In the accelerator facility, several scientific programs for producing radioactivity have been performed in several fields,
such as photon-activation analysis, nuclear chemistry, hot-atom chemistry, and radioactive tracers for material science. First,
we introduce an outline of the facility and the irradiation system for producing radioactivity. Then, several topics in these
fields are explored in detail. 相似文献
954.
Osamu Kido Hitoshi Suzuki Yuki Kimura Takeshi Sato Yoshio Saito Chihiro Kaito 《Physica E: Low-dimensional Systems and Nanostructures》2005,25(4):619-624
Al–Mn quasicrystal ultrafine particles can be produced by the advanced gas evaporation method (AGEM), which is a method of preparing ultrafine alloy particles by coalescence growth among the particles near the evaporation sources. We investigated the phase transition temperature from a quasicrystal to a stable crystal, by examining successive electron diffraction patterns of an ultrafine particle in an in situ experiment using a transmission electron microscope. In spite of the report that the Al86Mn14 quasicrystal transforms into the crystal phase at around 400–670 °C on thin film specimens, the quasicrystal ultrafine particle transformed at 800 °C, i.e., the quasicrystal ultrafine particle is more stable. Since the cross-sectional view of the surface oxide layer of the quasicrystal ultrafine particles can be easily observed, the surface oxides of η-Al2O3 and MnO were characterized as a result of the oxidation of residual atoms on the surface of the produced alloy particles including the quasicrystals. The conditions required for Al–Mn quasicrystal ultrafine particle formation by the AGEM can be estimated under the cooling rate of 105 K/s. 相似文献
955.
A eff,R and gR of the optical fibers for discrete Raman amplifiers are theoretically and experimentally investigated.It is demonstrated that Gaussian approximation is adaptable for Aeff,R of these fibers, and gR does not depend on only core materials. 相似文献
956.
Masumi Takemoto Yasutaka Iwakiri Yuki Suzuki Kiyoshi Tanaka 《Tetrahedron letters》2004,45(43):8061-8064
We have developed a novel procedure for the oxidative cleavage of indole carbon double bonds in the presence of H2O2 using plant cell cultures as a catalytic system. The oxidative procedure has some advantages, such as mild reactions, good yields, easy work-up and safety. 相似文献
957.
Secondary flow in a compound meandering channel with straight floodplain banks for overbank was investigated by a visualization method and velocity measurement using three-component laser Doppler anemometor (LDA). The secondary flow in a cross section was visualized by the neutral buoyant tracer method with a submergible video camera. Secondary flow vectors in a cross section were obtained by using PIV software with captured frames from video source through PC and also by LDA measurements. From the comparison of the PIV and LDA results, it is found that PIV data show good agreement in quality with LDA measurements when the secondary flow is strong and stable as shown in this paper. 相似文献
958.
Kensuke Naka Shinsuke Inagi Yuki Murachi Yoshiki Chujo 《Journal of polymer science. Part A, Polymer chemistry》2006,44(6):2027-2033
Novel vinylogous tetrathiafulvalene (TTF) containing polymers ( 13 and 14 ) were prepared by the oxidative dimerization polymerization of bisdithiafulvenes. The obtained polymers were soluble in common organic solvents such as CHCl3. The structures of the polymers were confirmed by 1H NMR and cyclic voltammetry analysis. The number‐average molecular weights of 13 and 14 were estimated from gel permeation chromatography to be 3600 and 3800, respectively. Through the introduction of phenylene or phenylene–vinylene spacers, distortion between dialkoxybenzene and vinylogous TTF units was effectively prevented according to ultraviolet–visible analysis. The polymers exhibited a strong electron‐donating property investigated by cyclic voltammetry analysis. Chemical doping by CF3SO3H gave doped polymers having a cationic radical and a dication of a vinylogous TTF unit. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2027–2033, 2006 相似文献
959.
Hoang The Ban Yasuo Tsunogae Takeshi Shiono 《Journal of polymer science. Part A, Polymer chemistry》2004,42(11):2698-2704
This article reports a practical method for preparing cis‐polybutadiene‐block‐syn‐polystyrene (cis‐PB‐b‐syn‐PS) copolymers with long crystallizable syndiotactic polystyrene (syn‐PS) segments chemically bonded with high cis‐1,4‐polybutadiene segments through the addition of styrene (ST) to a cis‐specific 1,3‐butadiene (BD) living catalyst composed of cyclopentadienyl titanium trichloride (CpTiCl3) and modified methylaluminoxane (MMAO). The incorporation of ST into the living polybutadiene (PB) precursor remarkably depended on the polymerization temperature. A low temperature (?20 °C) suppressed the rate of ST incorporation, but a high temperature (50 °C) tended to decompose the livingness of the active species and enhance the rate of the aspecific ST polymerization initiated by MMAO. Consequently, temperatures of 0–25 °C seemed to be best for this copolymerization system. Because of the absence of ST livingness, the final products contained not only the block copolymer but also the homopolymers. Attempts to isolate the block copolymer were carried out with common solvent fractionation techniques, but the results were not sufficient. Cross‐fractionation chromatography was, therefore, used for the isolation of the cis‐PB‐b‐syn‐PS copolymer. The presence of long syn‐PS segments was confirmed by the observation of a strong endothermic peak at 260 °C in the differential scanning calorimetry curve. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2698–2704, 2004 相似文献
960.
Yuki Kudo Takako Nakahara Tatsuro Nakagama Nobuko Seino Masaki Shinoda Katsumi Uchiyama 《Analytical sciences》2007,23(1):91-95
A surface-reaction system in a nanoliter water pool using an ink-jet microchip was developed. The reaction system in the nanodroplets formed on a poly(dimethylsiloxane) (PDMS) coated glass slide increased the diffusion-controlled reaction without using a nano-pump, specialized connector or highly sensitive detector. When nanoliter droplets were placed on the PDMS surface with a distance of 100 microm between them by the ink-jet microchip, the repeatabilities of the fluorescence intensity were 2.9% RSD (n = 7). The used ink-jet microchip had 4 different injection ports, and the distance between the ports was 0.995 mm. It was necessary to correct the distance in order to mix or dilute samples in a small droplet. The correction was successfully performed by moving the X-Y stage using inhouse-made software. A linear relationship was obtained between the Resorufin concentrations and the fluorescence intensity. We applied this system to an enzyme-linked immunosorbent assay (ELISA) for immunoglobulin A (IgA), and observed a difference in the fluorescence intensity derived from the amount of IgA (blank, 6.25 ng/mL, 12.5 ng/mL). These results show the usefulness of the open-type micro-analytical systems proposed by us. 相似文献