全文获取类型
收费全文 | 296篇 |
免费 | 10篇 |
国内免费 | 3篇 |
专业分类
化学 | 148篇 |
晶体学 | 2篇 |
力学 | 3篇 |
数学 | 51篇 |
物理学 | 105篇 |
出版年
2022年 | 3篇 |
2021年 | 6篇 |
2020年 | 4篇 |
2018年 | 3篇 |
2017年 | 2篇 |
2016年 | 4篇 |
2015年 | 10篇 |
2014年 | 5篇 |
2013年 | 15篇 |
2012年 | 15篇 |
2011年 | 22篇 |
2010年 | 11篇 |
2009年 | 4篇 |
2008年 | 10篇 |
2007年 | 13篇 |
2006年 | 10篇 |
2005年 | 14篇 |
2004年 | 8篇 |
2003年 | 14篇 |
2002年 | 8篇 |
2001年 | 13篇 |
2000年 | 8篇 |
1999年 | 3篇 |
1998年 | 5篇 |
1997年 | 3篇 |
1996年 | 4篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1992年 | 4篇 |
1991年 | 3篇 |
1989年 | 4篇 |
1987年 | 5篇 |
1986年 | 2篇 |
1985年 | 4篇 |
1984年 | 9篇 |
1983年 | 2篇 |
1982年 | 6篇 |
1979年 | 6篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1975年 | 5篇 |
1973年 | 4篇 |
1962年 | 1篇 |
1942年 | 2篇 |
1939年 | 3篇 |
1937年 | 4篇 |
1935年 | 2篇 |
1932年 | 3篇 |
1931年 | 3篇 |
排序方式: 共有309条查询结果,搜索用时 437 毫秒
81.
82.
Francavilla C Drake MD Bright FV Detty MR 《Journal of the American Chemical Society》2001,123(1):57-67
Dendrimeric polyphenylsulfides, -selenides, and -tellurides are prepared in high yield using propyloxy spacers to connect the phenylchalcogeno groups to the dendrimeric core. The selenides and tellurides catalyze the oxidation of bromide with hydrogen peroxide to give positive bromine species that can be captured by cyclohexene in two-phase systems. The corresponding sulfides show no catalytic activity. The increase in the rate of catalysis followed statistical effects for 1, 6, and 12 phenyltelluro groups. However, the increase in the rate of catalysis exceeds statistical contributions for the first few generations with 1, 3, 6, and 12 phenylseleno groups and suggested cooperativity among phenylseleno groups. The increase in catalytic rate was lost upon replacing all but one phenylseleno group with phenoxy groups. On the basis of H2O2 consumed, the dendrimer with 12 phenylseleno groups has a turnover number of >60 000 mol of H2O2 consumed per mole of catalyst. 相似文献
83.
Ido Efrat 《Israel Journal of Mathematics》2001,122(1):43-60
LetK be a perfect pseudo-algebraically closed field and letF be an extension ofK of relative transcendence degree 1. It is shown that the restriction map Res: Br(F)→Πp Br(F
p
h
) is injective, where p ranges over all non-trivialK-places ofF, andF
p
h
is the corresponding henselization. Conversely, the validity of this Hasse principle for all such extensionsF implies a weaker version of pseudo-algebraic closedness. As an application we determine the finitely generated pro-p closed subgroups of the absolute Galois group ofK(t). 相似文献
84.
85.
Yichao Huang Mickal Nawatha Ido Livneh Dr. Joseph M. Rogers Hao Sun Dr. Sumeet K. Singh Prof. Aaron Ciechanover Prof. Ashraf Brik Prof. Hiroaki Suga 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(36):8022-8027
Messenger RNA display of peptides containing non-proteinogenic amino acids, referred to as RaPID system, has become one of the leading methods to express libraries consisting of more than trillion-members of macrocyclic peptides, which allows for discovering de novo bioactive ligands. Ideal macrocyclic peptides should have dissociation constants (KD) as low as single-digit values in the nanomolar range towards a specific target of interest. Here, a twofold strategy to discover optimized macrocyclic peptides within this affinity regime is described. First, benzyl thioether cyclized peptide libraries were explored to identify tight binding hits. To obtain more insights into critical sequence information, sequence alignment was applied to guide rational mutagenesis for the improvement of their binding affinity. Using this twofold strategy, benzyl thioether macrocyclic peptide binders against Lys48-linked ubiquitin dimer (K48-Ub2) were successfully obtained that display KD values in the range 0.3–1.2 nm , which indicate binding two orders of magnitude stronger than those of macrocyclic peptides recently reported. Most importantly, this macrocyclic peptide also showed an improved cellular inhibition of the K48-Ub2 recognition by deubiquitinating enzymes and the 26S proteasome, resulting in the promotion of apoptosis in cancer cells. 相似文献
86.
Xia-Shi Lv Yong-Mei Cui He-Yun Wang Hai-Xia Lin Wei-Ya Ni Tomohiko Ohwada Katsutoshi Ido Kohei Sawada 《中国化学快报》2013,24(11):1023-1026
A series of hydrazone and N-acylhydrazone derivatives of dehydroabietic acid were synthesized and evaluated for BK channel-opening activities in an assay system of CHO-K1 cells expressing hBKa channels.The assay results indicated that the activities of the investigated compounds were influenced by the physicochemical properties of the substituent at hydrazone moiety. 相似文献
87.
The growing demand for titanium-based implants and the subsequent rise in implant-associated infections necessitate novel developments in anti-infective technologies. Recent research has drawn inspiration from nature to solve this problem. The nanoscale topography observed on cicada and dragonfly wings serves as a blueprint for synthetic analogs which seek to kill bacteria on contact through mechanical forces. This type of interaction has been dubbed the mechano-bactericidal effect. Various techniques have been utilized to mimic and improve upon these natural bactericidal surfaces. Alkaline hydrothermal etching is a simple and cost-effective technique to fabricate nanoscale protrusions on titanium and its alloys. This review aims to consolidate the current knowledge surrounding how fabrication parameters lead to varying surface topographies on titanium substrates, and subsequently, how surface topography and bacterial characteristics affect bactericidal activity. The bactericidal mechanism of hydrothermally etched titanium is inferred from comparisons with similar mechano-bactericidal biomaterials. The hostility of hydrothermally etched titanium toward bacteria is discussed in contrast to the observed host cell compatibility. Last, suggestions are made for the standardization of terminology in this emerging field. 相似文献
88.
We consider the p -Zassenhaus filtration (Gn) of a profinite group G . Suppose that G=S/N for a free profinite group S and a normal subgroup N of S contained in Sn. Under a cohomological assumption on the n-fold Massey products (which holds, e.g., if G has p -cohomological dimension ≤ 1), we prove that Gn+1 is the intersection of all kernels of upper-triangular unipotent (n+1)-dimensional representations of G over Fp. This extends earlier results by Miná?, Spira, and the author on the structure of absolute Galois groups of fields. 相似文献
89.
We present self-accelerating self-trapped beams in nonlinear optical media, exhibiting self-focusing and self-defocusing Kerr and saturable nonlinearities, as well as a quadratic response. In Kerr and saturable media such beams are stable under self-defocusing and weak self-focusing, whereas for strong self-focusing the beams off-shoot solitons while their main lobe continues to accelerate. Self-accelerating self-trapped wave packets are universal, and can also be found in matter waves, plasma, etc. 相似文献
90.
A method to design lasers that emit an arbitrary beam profile is studied. In these lasers, output-coupling is performed by a diffraction grating that imposes a phase and amplitude distribution onto the diffracted light. A solid-state laser emitting beams with a two-dimensional Airy intensity profile is demonstrated both theoretically and experimentally. In this case, the diffraction grating adds a transverse cubic phase to the diffracted light. An Airy beam is obtained by performing optical Fourier transform of the out-coupled light. The laser beam profile and power characteristics are shown to agree with theory. 相似文献