全文获取类型
收费全文 | 766篇 |
免费 | 21篇 |
国内免费 | 1篇 |
专业分类
化学 | 529篇 |
晶体学 | 13篇 |
力学 | 11篇 |
数学 | 30篇 |
物理学 | 205篇 |
出版年
2022年 | 3篇 |
2021年 | 7篇 |
2020年 | 9篇 |
2019年 | 9篇 |
2018年 | 7篇 |
2016年 | 5篇 |
2015年 | 12篇 |
2014年 | 20篇 |
2013年 | 32篇 |
2012年 | 31篇 |
2011年 | 35篇 |
2010年 | 25篇 |
2009年 | 25篇 |
2008年 | 41篇 |
2007年 | 41篇 |
2006年 | 41篇 |
2005年 | 50篇 |
2004年 | 36篇 |
2003年 | 30篇 |
2002年 | 27篇 |
2001年 | 8篇 |
2000年 | 11篇 |
1999年 | 17篇 |
1998年 | 8篇 |
1997年 | 4篇 |
1996年 | 10篇 |
1995年 | 7篇 |
1994年 | 10篇 |
1993年 | 12篇 |
1992年 | 17篇 |
1991年 | 16篇 |
1990年 | 12篇 |
1989年 | 7篇 |
1988年 | 9篇 |
1987年 | 17篇 |
1986年 | 11篇 |
1985年 | 25篇 |
1984年 | 9篇 |
1983年 | 12篇 |
1982年 | 11篇 |
1981年 | 9篇 |
1980年 | 11篇 |
1979年 | 8篇 |
1978年 | 8篇 |
1977年 | 3篇 |
1975年 | 3篇 |
1974年 | 3篇 |
1973年 | 9篇 |
1969年 | 2篇 |
1968年 | 3篇 |
排序方式: 共有788条查询结果,搜索用时 93 毫秒
71.
Junji Furukawa Shigenori Tsuruki Jitsuo Kiji 《Journal of polymer science. Part A, Polymer chemistry》1973,11(8):1819-1824
Alternating cooligomerization of isoprene with propylene has been investigated between ?30 and 0°C, VO(acac)2–Et3Al–Et2AlCl being used as catalyst. In the presence of an excess of propylene, 2,4,7-trimethyl-1,4-octadiene and 2,4-dimethyl-1,4-nonadiene are selectively formed. The formation is explained by the alternating coordination of isoprene and propylene to the vanadium. When triphenylphosphine or pyridine is added to the catalyst, the cooligomerization is suppressed while the formation of the dimer and trimer of isoprene is high. 相似文献
72.
This paper deals with the free transverse vibration of orthotropic trapezoidal plates clamped at the edges. A series-type method is applied for obtaining an analytical solution of the problem, and the resulting frequency equation is presented for symmetric trapezoids. In the numerical study, accurate frequency parameters and mode shapes of the plates are calculated for the first several modes, and the effects of the orthotropy are discussed. 相似文献
73.
Anisotropic optical absorption properties of single-walled carbon nanotubes (SWNTs) are determined from a vertically aligned SWNT film for 0.5-6 eV. Absorption peaks at 4.5 and 5.25 eV are found to exhibit remarkable polarization dependence and have relevance to optical properties of graphite. A method for determining a nematic order parameter for an aligned SWNT film based on the collinear absorption peak at 4.5 eV is presented, followed by the determination of the optical absorption cross section. 相似文献
74.
Tanaka Y Hoshino W Shimizu S Youfu K Aratani N Maruyama N Fujita S Osuka A 《Journal of the American Chemical Society》2004,126(10):3046-3047
When heated, bis-Cu(II) octaphyrin(1.1.1.1.1.1.1.1) is quantitatively split into two Cu(II) porphyrins both in solution and film states, which is accompanied by large absorption spectral changes. 相似文献
75.
Nickel A Maruyama T Tang H Murphy PD Greene B Yusuff N Wood JL 《Journal of the American Chemical Society》2004,126(50):16300-16301
A total synthesis of the biologically important diterpene ingenol has been completed. Ring-closing olefin metathesis was used to construct the strained "inside-outside" tetracyclic skeleton, and a series of diastereoselective reactions were employed to complete the synthesis. Another naturally occurring ingenane, 20-deoxyingenol, has also been prepared. 相似文献
76.
Fujii T Naito A Yamaguchi S Wada A Funahashi Y Jitsukawa K Nagatomo S Kitagawa T Masuda H 《Chemical communications (Cambridge, England)》2003,(21):2700-2701
A novel hydroperoxo-copper(II) complex with a square-planar geometry has been prepared, which has exhibited a higher selectivity and catalytic reactivity for dimethyl sulfide, in contrast to that with a trigonal-bipyramidal one. 相似文献
77.
Phrutivorapongkul A Lipipun V Ruangrungsi N Kirtikara K Nishikawa K Maruyama S Watanabe T Ishikawa T 《Chemical & pharmaceutical bulletin》2003,51(2):187-190
Four new chalcone derivatives (1, 4, 7, 10) were isolated from the stem bark of Millettia leucantha KURZ (Leguminosae) along with two known ones (2, 6) and five known flavones (3, 5, 8, 9, 11). Structure elucidation and unambiguous assignment of the isolates were achieved with the aid of 1D and 2D NMR extensive studies. Correlation of 10 to 4 was successfully done by reduction with Et(3)SiH/CF(3)CO(2)H. Moderate cytotoxic activity was observed in chalcones (1, 10), whereas dihydrochalcones (4, 6) showed moderate anti-Herpes Simplex Virus (HSV) activity. Interestingly, flavone 8 showed significant anti-inflammatory effects inhibiting both cyclooxygenase (COX)-1 and -2. 相似文献
78.
傅元勇 周书华T. Koike S. Kinoshita Y. Ma Y. Miura K. Miwa Y. Miyagi K. Shirotori T. Suzuki H. Tamura K. Tsukada M. Ukai K. Futatsukawa K. Hosomi M. Kawai M. Mimori N. Terada N. Maruyama K. Aoki H Fujioka Y Kakiguchi T. Nagae D. Nakajima H Noumi T Takahashi T.N. Takahashi A. Toyota M. Dairaku T. Fukuda S. Minami W. Imoto S. Aiimura K. Tanida 《中国物理快报》2007,24(8):2216-2218
From the ^12 C(π^+,K^+)^12 AC reaction the γ -rays of 261.6±0.24 ke V(7/2^+ →5/2^+)and 1481.7±0.7 ke V(1/2^+ →5/2^+) of ^11 A B,and 2667.3±2.8 keV(1^- 2 → 2^- 1)of ^12 A C hypernuclei have been identified using a large germanium detector array Hyperball2 at K6 beam line of KEK. The observed energies of the transitions 1481.7keV and 261.6 keV are significantly different from the values predicted by the shell model using the △ and SN parameters determined from the ^7 △ Li data. 相似文献
79.
80.
Shigenori Kashimura Yoshiyuki Tane Yoshihiro Murai Tomohiro Nakai Ryuich Hirose 《Tetrahedron letters》2008,49(2):269-271
Reduction of dichlorosilanes with Mg metal in the presence of Lewis acid and LiCl was found to be the highly practical method for the synthesis of polysilanes. 相似文献