全文获取类型
收费全文 | 1125篇 |
免费 | 31篇 |
国内免费 | 6篇 |
专业分类
化学 | 710篇 |
晶体学 | 7篇 |
力学 | 23篇 |
数学 | 125篇 |
物理学 | 297篇 |
出版年
2022年 | 9篇 |
2020年 | 24篇 |
2019年 | 20篇 |
2016年 | 21篇 |
2015年 | 29篇 |
2014年 | 24篇 |
2013年 | 30篇 |
2012年 | 43篇 |
2011年 | 49篇 |
2010年 | 38篇 |
2009年 | 33篇 |
2008年 | 45篇 |
2007年 | 49篇 |
2006年 | 47篇 |
2005年 | 50篇 |
2004年 | 38篇 |
2003年 | 24篇 |
2002年 | 21篇 |
2001年 | 24篇 |
2000年 | 13篇 |
1999年 | 17篇 |
1998年 | 16篇 |
1997年 | 16篇 |
1996年 | 12篇 |
1995年 | 11篇 |
1994年 | 14篇 |
1993年 | 11篇 |
1992年 | 11篇 |
1991年 | 9篇 |
1989年 | 11篇 |
1987年 | 9篇 |
1985年 | 9篇 |
1984年 | 8篇 |
1983年 | 14篇 |
1982年 | 15篇 |
1981年 | 18篇 |
1980年 | 13篇 |
1978年 | 10篇 |
1976年 | 8篇 |
1975年 | 9篇 |
1974年 | 9篇 |
1973年 | 9篇 |
1943年 | 12篇 |
1933年 | 11篇 |
1931年 | 8篇 |
1930年 | 9篇 |
1924年 | 8篇 |
1923年 | 10篇 |
1902年 | 7篇 |
1881年 | 7篇 |
排序方式: 共有1162条查询结果,搜索用时 31 毫秒
81.
Solladié N Walther ME Gross M Duarte TM Bourgogne C Nierengarten JF 《Chemical communications (Cambridge, England)》2003,(19):2412-2413
In addition to the ammonium-crown ether recognition, pi-stacking interactions between the C60 sphere and the porphyrin moiety have been evidenced in a supramolecular complex obtained from a porphyrin-crown ether conjugate and a fullerene derivative bearing an ammonium unit. 相似文献
82.
The development of an all-solid-state cw laser system for optical absorption measurements of the OH radical in the UV spectral range is described. The tunable output of a 1064-nm external-cavity diode laser is amplified by use of a Nd:doped, double-clad fiber amplifier. The amplified near-IR radiation is frequency doubled by a periodically poled lithium niobate crystal and then quadrupled in a beta-barium borate crystal. The design and operation of the system and measurements of OH absorption in the (2, 0) band of the A(2)?(+)- X(2)? electronic transition are discussed. 相似文献
83.
We propose a scheme for slowing down decay into a continuum. We make use of a sequence of ultrashort 2pi pulses applied on an auxiliary transition of the system so that there is a destructive interference between the two transition amplitudes--one before the application of the pulse and the other after the application of the pulse. We give explicit results for a structured continuum. Our scheme can also inhibit unwanted transitions. 相似文献
84.
85.
Rasmus Fonseca Glennie Helles Pawel Winter 《Journal of Mathematical Modelling and Algorithms》2011,10(4):357-369
One reason why ab initio protein structure predictors do not perform very well is their inability to reliably identify long-range
interactions between amino acids. To achieve reliable long-range interactions, all potential pairings of β-strands (β-topologies) of a given protein are enumerated, including the native β-topology. Two very different β-topology scoring methods from the literature are then used to rank all potential β-topologies. This has not previously been attempted for any scoring method. The main result of this paper is a justification
that one of the scoring methods, in particular, consistently top-ranks native β-topologies. Since the number of potential β-topologies grows exponentially with the number of β-strands, it is unrealistic to expect that all potential β-topologies can be enumerated for large proteins. The second result of this paper is an enumeration scheme of a subset of β-topologies. It is shown that native-consistent β-topologies often are among the top-ranked β-topologies of this subset. The presence of the native or native-consistent β-topologies in the subset of enumerated potential β-topologies relies heavily on the correct identification of β-strands. The third contribution of this paper is a method to deal with the inaccuracies of secondary structure predictors
when enumerating potential β-topologies. The results reported in this paper are highly relevant for ab initio protein structure prediction methods based
on decoy generation. They indicate that decoy generation can be heavily constrained using top-ranked β-topologies as they are very likely to contain native or native-consistent β-topologies. 相似文献
86.
87.
Bernard Walther Pierre-Alain Carrupt Nabil El Tayar Bernard Testa 《Helvetica chimica acta》1989,72(3):507-517
The 8-substituted xanthines 1 – 21 (including compound S 9795), caffeine ( 22 ), and the three isomeric dimethyl-xanthines 23 – 25 (see Table 1), were examined for their lipophilic behaviour using a reversed-phase HPLC technique. A number of flexible compounds showed a smaller-than-expected lipophilicity which based on conformational and tautomeric calculations were ascribed to the predominance of folded forms. A QSAR analysis of the phosphodiesterase-inhibitory potency of several compounds showed favourable factors to be a low lipophilicity and the absence of a substituent on the N7 position. 相似文献
88.
89.
90.
Walther Hempel 《Fresenius' Journal of Analytical Chemistry》1877,16(1):454-457
Ohne ZusammenfassungDresden, Juni 1877, Laboratorium des Herrn Professor Schmitt im Polytechnikum. 相似文献