全文获取类型
收费全文 | 2643篇 |
免费 | 47篇 |
国内免费 | 5篇 |
专业分类
化学 | 2153篇 |
晶体学 | 33篇 |
力学 | 9篇 |
数学 | 116篇 |
物理学 | 384篇 |
出版年
2020年 | 22篇 |
2019年 | 20篇 |
2018年 | 16篇 |
2016年 | 27篇 |
2015年 | 32篇 |
2014年 | 41篇 |
2013年 | 109篇 |
2012年 | 95篇 |
2011年 | 111篇 |
2010年 | 53篇 |
2009年 | 80篇 |
2008年 | 127篇 |
2007年 | 143篇 |
2006年 | 174篇 |
2005年 | 144篇 |
2004年 | 142篇 |
2003年 | 138篇 |
2002年 | 104篇 |
2001年 | 44篇 |
2000年 | 47篇 |
1999年 | 28篇 |
1998年 | 31篇 |
1997年 | 26篇 |
1996年 | 28篇 |
1995年 | 19篇 |
1994年 | 35篇 |
1993年 | 20篇 |
1992年 | 34篇 |
1991年 | 26篇 |
1990年 | 27篇 |
1989年 | 15篇 |
1988年 | 33篇 |
1987年 | 25篇 |
1986年 | 30篇 |
1985年 | 42篇 |
1984年 | 34篇 |
1983年 | 25篇 |
1982年 | 49篇 |
1981年 | 50篇 |
1980年 | 47篇 |
1979年 | 52篇 |
1978年 | 30篇 |
1977年 | 47篇 |
1976年 | 35篇 |
1975年 | 40篇 |
1974年 | 33篇 |
1973年 | 37篇 |
1972年 | 16篇 |
1969年 | 13篇 |
1968年 | 25篇 |
排序方式: 共有2695条查询结果,搜索用时 15 毫秒
41.
The structural analysis of amylose tris(3,5-dimethylphenylcarbamate) (ADMPC) was performed by NMR spectroscopy using a sample with a lower degree of polymerization in order to understand the chiral recognition mechanism when it was used as a chiral stationary phase (CSP) in high-performance liquid chromatography (HPLC). ADMPC exhibited chiral discrimination for many enantiomers, including 1-(9-anthryl)-2,2,2-trifluoroethanol (1) and 1,1'-bi-2-naphthol (2) in both NMR and HPLC. A good agreement was observed between the HPLC and NMR results when chloroform was employed as the common solvent. The structure of ADMPC in solution was investigated by NMR using the 2D NOESY technique coupled with computer modeling, and a left-handed 4/3 helical structure was obtained as the most probable one. The binding geometry between ADMPC and the enantiomers of 1 was also investigated by (1)H NMR titration. On the basis of these results combined with molecular modeling, a rational model to explain the chiral discrimination mechanism of 1 on ADMPC was proposed. 相似文献
42.
Insulating tubular BN sheathing on semiconducting nanowires 总被引:1,自引:0,他引:1
Zhu YC Bando Y Xue DF Xu FF Golberg D 《Journal of the American Chemical Society》2003,125(47):14226-14227
An effective method was developed for generation of insulating tubular boron nitride (BN)-sheathed nanostructures. ZnS nanowires and multilayered Si-SiO2 nanowires were successfully sheathed with insulating tubular BN-forming nanocables. Both the semiconductor nanowire cores and the BN sheaths are crystalline with well-uniform morphologies. 相似文献
43.
Bo Jiang Hui Song Yunqing Kang Shengyao Wang Qi Wang Xin Zhou Kenya Kani Yanna Guo Jinhua Ye Hexing Li Yoshio Sakka Joel Henzie Yamauchi Yusuke 《Chemical science》2020,11(3):791
Generating high surface area mesoporous transition metal boride is interesting because the incorporation of boron atoms generates lattice distortions that lead to the formation of amorphous metal boride with unique properties in catalysis. Here we report the first synthesis of mesoporous cobalt boron amorphous alloy colloidal particles using a soft template-directed assembly approach. Dual reducing agents are used to precisely control the chemical reduction process of mesoporous cobalt boron nanospheres. The Earth-abundance of cobalt boride combined with the high surface area and mesoporous nanoarchitecture enables solar-energy efficient photothermal conversion of CO2 into CO compared to non-porous cobalt boron alloys and commercial cobalt catalysts.Generating high surface area mesoporous transition metal boride is challenging but interesting because incorporation of boron atoms can generate lattice distortion to form amorphous metal boride which has unique properties in catalysis. 相似文献
44.
Huzihiro Araki 《Letters in Mathematical Physics》1996,38(4):399-410
Continuing the earlier work on soliton sectors, we determine all finite energy representations of the XY model for almost all parameter values. In the interior of unique vacuum regions of parameters (i.e. the large external magnetic field region ||>1), the unique irreducible vacuum representation is the only finite energy representation.At the critical values of the parameters (||=1 as well as theXY symmetric case =0, ||1), there is an infinite number of mutually nonequivalent irreducible finite energy representations. Apart from the unique irreducible ground state representation and another associated irreducible representation, these infinite number of representations arise from an infinite number of nearly zero energy excitations of the ground state with a finite total energy and may be called infrared representations.In the remaining cases, as have been studied earlier, there are two additional irreducible finite energy representations besides two irreducible ground state representations and they are topological soliton sectors with different ground state limits in positive and negative spatial infinity. (For two exceptional values of parameters (, )=(0, ±1), they also become ground state representations.) 相似文献
45.
Yoshio Imai Mitsuru Ueda Kouetsu Otaira 《Journal of polymer science. Part A, Polymer chemistry》1977,15(6):1457-1463
A series of new polyarylamines was prepared by the vinylogous nuclephilic substitution polymerization of bis(4-chloro-3-nitrophenyl) sulfone with both aromatic and aliphatic diamines. The synthesis involves the solution polycondensation in a polar aprotic solvent at elevated temperatures, a tertiary amine being used as an acid acceptor. Of these solvents, dimethyl sulfoxide and N-methyl-2-pyrrolidone were the most effective for the preparation of high molecular weight polymers. The polyarylamines having inherent viscosities in the range of 0.1–0.5 were all amorphous and highly soluble in polar aprotic solvents. Thermogravimetric analysis under both air and nitrogen atmospheres indicated that rapid decomposition began above 300°C for the polyarylamines from aromatic diamines. 相似文献
46.
Kazuo Itoya Hidetsugu Sawada Masa-Aki Kakimoto Yoshio Imai 《Journal of polymer science. Part A, Polymer chemistry》1994,32(15):2947-2951
A facile one-step method for the synthesis of aliphatic polybenzoxazoles has been developed. Thus, a series of aliphatic polybenzoxazoles having inherent viscosities of 0.2–0.7 dL/g in concentrated sulfuric acid were successfully synthesized by the melt polycondensation of alipatic dinitriles with 4,4′-diamino-3,3′-dihydroxybiphenyl (AHB) or its hydrochloride (AHB–HCl) with the elimination of ammonia or ammonium chloride, respectively. Monomer AHB–HCl was more reactive than the parent AHB, thereby affording higher molecular weight polybenzoxazoles in a shorter reaction time. The aliphatic polybenzoxazoles having 6–10 methylene units were highly crystalline with melting temperatures in the range of 187–308°C, which were stable up to 400°C in a melt state in nitrogen. © 1994 John Wiley & Sons, Inc. 相似文献
47.
48.
49.
50.