全文获取类型
收费全文 | 1815篇 |
免费 | 55篇 |
国内免费 | 6篇 |
专业分类
化学 | 1343篇 |
晶体学 | 24篇 |
力学 | 15篇 |
数学 | 108篇 |
物理学 | 386篇 |
出版年
2022年 | 10篇 |
2021年 | 14篇 |
2020年 | 18篇 |
2019年 | 14篇 |
2018年 | 15篇 |
2017年 | 10篇 |
2016年 | 36篇 |
2015年 | 41篇 |
2014年 | 39篇 |
2013年 | 60篇 |
2012年 | 78篇 |
2011年 | 97篇 |
2010年 | 60篇 |
2009年 | 48篇 |
2008年 | 93篇 |
2007年 | 111篇 |
2006年 | 88篇 |
2005年 | 96篇 |
2004年 | 104篇 |
2003年 | 87篇 |
2002年 | 84篇 |
2001年 | 48篇 |
2000年 | 42篇 |
1999年 | 17篇 |
1998年 | 26篇 |
1997年 | 12篇 |
1996年 | 28篇 |
1995年 | 24篇 |
1994年 | 24篇 |
1993年 | 19篇 |
1992年 | 19篇 |
1991年 | 27篇 |
1990年 | 26篇 |
1989年 | 20篇 |
1988年 | 18篇 |
1987年 | 11篇 |
1986年 | 25篇 |
1985年 | 22篇 |
1984年 | 26篇 |
1983年 | 17篇 |
1982年 | 20篇 |
1981年 | 20篇 |
1980年 | 23篇 |
1979年 | 14篇 |
1978年 | 16篇 |
1977年 | 24篇 |
1976年 | 10篇 |
1975年 | 14篇 |
1974年 | 12篇 |
1973年 | 15篇 |
排序方式: 共有1876条查询结果,搜索用时 15 毫秒
851.
Takashi Hirota Hiroko Fujita Kenji Sasaki Tetsuto Namba 《Journal of heterocyclic chemistry》1986,23(6):1715-1716
A novel synthesis of 2-benzofurancarbaldehydes by the Vilsmeier reaction of phenoxyacetaldehyde diethyl acetals is described. 相似文献
852.
853.
Akira Fujii Hideaki Matsuo Jun-Chul Choi Tadahiro Fujitani Ken-ichi Fujita 《Tetrahedron》2018,74(24):2914-2920
By employing tetrabutylammonium fluoride (TBAF) as a catalyst, the various carboxylative cyclizations of the propargylic amines having internal alkynes with CO2 proceeded to afford the corresponding 2-oxazolidinones. In this case, it was also found that the generated 2-oxazolidinones were tautomerized into the corresponding 2-oxazolones due to the basicity of TBAF. In addition, we performed the synthesis of quinazoline-2,4(1H,3H)-dione from 2-aminobenzonitrile and CO2 by using TBAF as a catalyst. 相似文献
854.
855.
Levitation of metallic melt by using the simultaneous imposition of the alternating and the static magnetic fields 总被引:3,自引:0,他引:3
Hideyuki Yasuda Itsuo Ohnaka Yuki Ninomiya Rintaro Ishii Satoru Fujita Kohji Kishio 《Journal of Crystal Growth》2004,260(3-4):475-485
This study developed a new levitation method, which used the simultaneous imposition of static and alternating magnetic fields. Dynamic behavior was measured for pure Cu and pure Ni melts levitated by the proposed method. The oscillation due to surface tension and convection in levitated Cu melts were hardly observed at static magnetic fields exceeding 1 T. Only the rotation of this axis parallel to the static magnetic field was observed under high static magnetic fields. The proposed method demonstrated that metallic melt could be statically levitated like a solid sphere. It was also found that stable levitation of paramagnetic Ni melt was rather difficult at static magnetic fields exceeding 5 T, because of the magnetization force. 相似文献
856.
Y. Liu N. Yamamoto Y. Nishimoto N. Kamikubo S. Shimomura K. Gamo K. Murase N. Sano A. Adachi K. Fujita T. Watanabe S. Hiyamizu 《Journal of Crystal Growth》1995,150(1-4):299-305
InxGa1−xAs/GaAs (x = 0.12-0.23) quantum well (QW) structures were grown by molecular beam epitaxy (MBE) on [001] ridges with various widths (1.1-12 μm) of patterned GaAs (100) substrate. The smallest lateral width of the InGaAs/GaAs quantum wire (QWR) structures was estimated to be about 0.1 μm by high-resolution scanning electron microscope (SEM). The In contents of the grown InGaAs/GaAs QWs on the ridges were studied as a function of ridge top width (ridge width of the MBE grown layer) by cathodoluminescence (CL) measurements at 78 K. Compared to the InGaAs QW grown on a flat substrate, the In content of the InGaAs/GaAs QW on the ridge increases from 0.22 to 0.23 when the ridge top width decreases to about 2.9 μm, but it decreases steeply from 0.23 down to 0.12 with a further decrease of the ridge width from 2.9 to 0.05 μm. A simulation of MBE growth of InGaAs on the [001] ridges shows that this reduced In content for narrow ridges is due to a large migration of Ga atoms to the (100) ridge top region from {110} side facets. 相似文献
857.
We have grown In0.2Ga0.8As strained quantum wells (SQWs) on GaAs (111)A just and off-angled substrates by molecular beam epitaxy (MBE). The photoluminescence (PL) peak energy of SQWs grown on (111)A related substrates shows a large redshift as compared with the calculated values. The red-shift observed in SQWs grown on a (111)A 5° off toward [001] substrate can be explained by the presence of a built-in electric field E = 154 kV/cm due to piezoelectric effect. The larger red-shift observed in samples grown on the other substrates is partially due to strain relaxation. A strain relaxation mechanism that consists of coherently grown islands when InGaAs growth begins and the generation of misfit dislocations when these islands coalesce, gives a qualitative explanation of the observed results. 相似文献
858.
859.
860.