全文获取类型
收费全文 | 3739篇 |
免费 | 170篇 |
国内免费 | 15篇 |
专业分类
化学 | 2932篇 |
晶体学 | 36篇 |
力学 | 46篇 |
数学 | 231篇 |
物理学 | 679篇 |
出版年
2022年 | 38篇 |
2021年 | 46篇 |
2020年 | 69篇 |
2019年 | 95篇 |
2018年 | 59篇 |
2017年 | 42篇 |
2016年 | 97篇 |
2015年 | 73篇 |
2014年 | 109篇 |
2013年 | 174篇 |
2012年 | 206篇 |
2011年 | 253篇 |
2010年 | 110篇 |
2009年 | 117篇 |
2008年 | 216篇 |
2007年 | 206篇 |
2006年 | 214篇 |
2005年 | 206篇 |
2004年 | 172篇 |
2003年 | 127篇 |
2002年 | 119篇 |
2001年 | 75篇 |
2000年 | 57篇 |
1999年 | 53篇 |
1998年 | 33篇 |
1997年 | 45篇 |
1996年 | 48篇 |
1995年 | 39篇 |
1994年 | 26篇 |
1993年 | 34篇 |
1992年 | 46篇 |
1991年 | 29篇 |
1990年 | 33篇 |
1989年 | 35篇 |
1988年 | 41篇 |
1987年 | 34篇 |
1986年 | 29篇 |
1985年 | 63篇 |
1984年 | 38篇 |
1983年 | 30篇 |
1982年 | 33篇 |
1981年 | 33篇 |
1980年 | 29篇 |
1979年 | 42篇 |
1978年 | 33篇 |
1977年 | 28篇 |
1976年 | 22篇 |
1975年 | 24篇 |
1974年 | 28篇 |
1973年 | 26篇 |
排序方式: 共有3924条查询结果,搜索用时 15 毫秒
101.
Takahiro Makino Kimihiko Kato Hiroyuki Lyozumi Hiroe Honzawa Yoshiaki Tachiiri Mitsuo Hiramatsu † 《Photochemistry and photobiology》1996,64(6):953-956
Abstract— Ultraweak luminescence generated by sweet potato and nonpathogenic Fusarium oxysporum interactions associated with a defense response was detected by a photoncounting method using ultrahigh-sensitive photodetectors. The time-dependent intensity variation, the spectrum and the two-dimensional imaging of the ultraweak luminescence are indicative of the defense response of the sweet potato to F. oxysporum. The production of ipomeamarone as a phytoalexin means that F. oxysporum induced the defense response in the sweet potato. 相似文献
102.
103.
104.
105.
Qi ZM Matsuda N Santos J Yoshida T Takatsu A Kato K 《Journal of colloid and interface science》2004,271(1):249-253
Broadband, time-resolved optical waveguide (OWG) spectroscopy has been used for in situ, real-time investigation into the self-assembly of metal nanoparticle monolayers. The OWG spectroscopy makes it possible to use the transverse electric (TE) and transverse magnetic (TM) modes to measure surface plasmon absorption of immobilized metal nanoparticles in two directions, parallel and normal to the waveguide surface. Therefore, this technique can provide direction-dependent information on the metal nanoparticles at the interface. In this paper, a 50-microm-thick glass plate was used as a slab waveguide and the kinetics of Au nanoparticle adsorption on a hemoglobin-functionalized glass substrate was examined in the early stage of self-assembly. The findings show that with the TE mode the surface plasmon resonance (SPR) behavior for immobilized Au nanoparticles is different from that with the TM mode. 相似文献
106.
107.
A phytochemical investigation in plantlets of the Brazilian medicinal tree Virola surinamensis resulted in the isolation and structural determination of four new compounds: 3-hydroxy-4-methyl-2-(11'-piperonyl-n-undecyl)-butenolide; 3-hydroxy-4-methyl-2-(7'-piperonyl-n-heptyl)-butanolide; 9'-(3,4-methylenedioxy-phenyl)-nonanoic acid and 13'-(3,4-methylene-dioxyphenyl)-tridecanoic acid. Thirteen compounds previously isolated from seeds and adult plants were also reported. 相似文献
108.
Photoluminescence enhancement of PEG-modified YAG:Ce3+ nanocrystal phosphor prepared by glycothermal method 总被引:1,自引:0,他引:1
Y3Al5O12:Ce3+ (YAG:Ce3+) nanocrystals were synthesized in 1,4-butylene glycol (BG) with and without poly(ethylene glycol) (PEG) by the glycothermal method. The internal quantum efficiency of the photoluminescence (PL) corresponding to the 5d --> 4f transition of Ce3+ in the YAG:Ce3+ nanocrystal increased from 21.3 to 37.9% by addition of PEG, while no appreciable change in the primary particle size, the crystallite size, and the lattice distortion was recognized by transmission electron microscopy and X-ray diffractometry. The thermogravimetry-differential thermal analysis, Fourier transform infrared absorption spectroscopy and 1H --> 13C cross-polarization magic angle spinning nuclear magnetic resonance (CP-MAS NMR) confirmed the preferential coordination of PEG to the YAG:Ce3+ nanocrystal. 27Al single-pulse excitation MAS NMR reveals that the ratio of the 4-fold coordination site to the 6-fold coordination site increased from 0.53 to 0.72 by addition of PEG. We conclude that the surface modification of the YAG:Ce3+ nanocrystal by PEG induces the surface passivation, the prevention of the oxidation of Ce3+ to Ce4+, the promotion of the incorporation of Ce3+ into YAG and the local structural rearrangement, resulting in the PL enhancement. 相似文献
109.
A rhodium-catalyzed isomerization of alpha-arylpropargyl alcohols to indanones has been developed under mild conditions. Considering the ease of preparation of these propargyl alcohols (terminal alkynes + aromatic aldehydes), this method provides a new way of constructing indanones with high efficiency. By the mechanistic investigations using deuterium-labeled substrates, it has also been demonstrated that the reaction goes through an unexpected cascade, with a 1,4-hydrogen shift being the turnover-limiting step of the catalytic cycle. 相似文献
110.
Significant improvement in enantioselectivity and catalyst activity was achieved for the catalytic enantioselective Strecker reaction. Using a catalyst (1-2.5 mol %) prepared from Gd(OiPr)3 and d-glucose derived ligand 1, and in the presence of 2,6-dimethylphenol as an additive, high enantioselectivity was obtained from a wide range of ketoimines, including heteroaromatic and cyclic ketoimines. The new method was applied to an efficient catalytic asymmetric synthesis of sorbinil, a therapeutic agent for diabetic complications. 相似文献