全文获取类型
收费全文 | 479篇 |
免费 | 21篇 |
国内免费 | 3篇 |
专业分类
化学 | 390篇 |
晶体学 | 12篇 |
力学 | 8篇 |
数学 | 26篇 |
物理学 | 67篇 |
出版年
2023年 | 6篇 |
2021年 | 5篇 |
2020年 | 10篇 |
2019年 | 13篇 |
2018年 | 8篇 |
2017年 | 4篇 |
2016年 | 7篇 |
2015年 | 8篇 |
2014年 | 18篇 |
2013年 | 26篇 |
2012年 | 33篇 |
2011年 | 32篇 |
2010年 | 16篇 |
2009年 | 7篇 |
2008年 | 34篇 |
2007年 | 22篇 |
2006年 | 11篇 |
2005年 | 21篇 |
2004年 | 19篇 |
2003年 | 25篇 |
2002年 | 18篇 |
2001年 | 6篇 |
2000年 | 7篇 |
1999年 | 3篇 |
1998年 | 7篇 |
1997年 | 9篇 |
1996年 | 6篇 |
1995年 | 5篇 |
1994年 | 3篇 |
1993年 | 6篇 |
1992年 | 6篇 |
1991年 | 8篇 |
1990年 | 9篇 |
1989年 | 4篇 |
1988年 | 5篇 |
1987年 | 4篇 |
1986年 | 4篇 |
1985年 | 5篇 |
1984年 | 6篇 |
1983年 | 5篇 |
1982年 | 2篇 |
1980年 | 5篇 |
1979年 | 10篇 |
1978年 | 4篇 |
1977年 | 6篇 |
1976年 | 5篇 |
1975年 | 3篇 |
1974年 | 8篇 |
1970年 | 2篇 |
1968年 | 6篇 |
排序方式: 共有503条查询结果,搜索用时 15 毫秒
91.
Dr. Hayato Fukuda Yuko Nishiyama Shiina Nakamura Yutaro Ohno Prof. Dr. Tadashi Eguchi Prof. Dr. Yoshiharu Iwabuchi Prof. Dr. Takeo Usui Prof. Dr. Naoki Kanoh 《化学:亚洲杂志》2012,7(12):2872-2881
We have developed two syntheses of vicenistatin and its analogues. Our first‐generation strategy included the rapid and sequential assembly of the macrocyclic lactam by using an intermolecular Horner–Wadsworth–Emmons reaction between the C3–C13 fragment and the C1–C2, C14–C19 fragment, followed by an intramolecular Stille coupling reaction. The second‐generation strategy utilized a ring‐closing metathesis of a hexaene intermediate to generate the desired 20‐membered macrolactam. This second‐generation strategy made it possible to prepare synthetic analogues of vicenistatin, including the C20‐ and/or C23‐demethyl analogues. Evaluation of the cytotoxic effect of these analogues indicated the importance of the fixed conformation of aglycon for determining the biological activity of the vicenistatins. 相似文献
92.
93.
High-frequency ripple (spike noise) effects in the qualitative properties of DC/DC converter circuits. This study investigates the bifurcation structure of a chaotic attractor in a switched dynamical system with spike noise. First, we introduce the system dynamics and derive the associated Poincaré map. Next, we show the bifurcation structure of the chaotic attractor in a system with spike noise. Finally, we investigate the dynamical effect of spike noise in the existence region of the chaotic attractor compare with that of a chaotic attractor in a system with ideal switching. The results suggest that spike noise enlarges an invariant set and generates a new bifurcation structure of the chaotic attractor. 相似文献
94.
95.
Matsuura S Yokoyama T Ishii R Itoh T Tomon E Hamakawa S Tsunoda T Mizukami F Nanbu H Hanaoka TA 《Chemical communications (Cambridge, England)》2012,48(56):7058-7060
A flow-type microreactor containing glutaminase-mesoporous silica composites with 10.6 nm pore diameter (TMPS10.6) was developed for the continuous synthesis of theanine, a unique amino acid. High enzymatic activity was exhibited by the local control of the reaction temperature. 相似文献
96.
A nonporous crystalline solid consisting of an organoarsenic platinum(II) complex, i.e., a mononuclear diiodoplatinum(II) complex trans-PtI(2)(cis-DHDAtBu)(2) (1) with cis-1,4-dihydro-1,4-dimethyl-2,3,5,6-tetrakis(tert-butoxycarbonyl)-1,4-diarsinine (cis-DHDAtBu), shows on-off solid-state luminescence switching through reversible solvent vapor uptake and escape. The on-off switching of solid-state luminescence was achieved without changing the structure or electronic state of the organoarsenic platinum(II) complex. 相似文献
97.
Takuji Sato 《Journal of Geometry》2004,80(1-2):196-208
We construct non-compact examples of Hermitian manifolds with pointwise constant anti-holomorphic sectional curvature. Our examples are obtained by conformal change of the metric on an open set of the complex space form. 相似文献
98.
Takuji HiroseBenjamin G. Kopek Zhao-Hui WangRitsuko Yusa Bruce W. Baldwin 《Tetrahedron letters》2003,44(9):1831-1833
Using imidazole as promotion agent, primary, secondary and phenolic alcohol compounds were esterified with aliphatic and aromatic carboxylic acid anhydrides. Heating a ternary mixture of alcohol, anhydride and imidazole in an unmodified microwave oven produced esters in low to high yields, depending on the steric bulk of the alcohol. 相似文献
99.
Takuji Nakamura 《Proceedings of the American Mathematical Society》2007,135(2):559-567
As a generalization of pretzel surfaces, L. Rudolph has introduced a notion of braidzel surfaces in his study of the quasipositivity for pretzel surfaces. In this paper, we show that any oriented link has a braidzel surface. We also introduce a new geometric numerical invariant of links with respect to their braidzel surface and study relationships among them and other ``genus' for links.
100.
In this paper we consider robust parameter estimation based on a certain cross entropy and divergence. The robust estimate is defined as the minimizer of the empirically estimated cross entropy. It is shown that the robust estimate can be regarded as a kind of projection from the viewpoint of a Pythagorean relation based on the divergence. This property implies that the bias caused by outliers can become sufficiently small even in the case of heavy contamination. It is seen that the asymptotic variance of the robust estimator is naturally overweighted in proportion to the ratio of contamination. One may surmise that another form of cross entropy can present the same behavior as that discussed above. It can be proved under some conditions that no cross entropy can present the same behavior except for the cross entropy considered here and its monotone transformation. 相似文献