全文获取类型
收费全文 | 791篇 |
免费 | 37篇 |
国内免费 | 8篇 |
专业分类
化学 | 713篇 |
晶体学 | 1篇 |
力学 | 4篇 |
数学 | 57篇 |
物理学 | 61篇 |
出版年
2024年 | 1篇 |
2023年 | 4篇 |
2022年 | 28篇 |
2021年 | 43篇 |
2020年 | 32篇 |
2019年 | 27篇 |
2018年 | 22篇 |
2017年 | 14篇 |
2016年 | 24篇 |
2015年 | 22篇 |
2014年 | 30篇 |
2013年 | 46篇 |
2012年 | 54篇 |
2011年 | 54篇 |
2010年 | 52篇 |
2009年 | 39篇 |
2008年 | 50篇 |
2007年 | 53篇 |
2006年 | 41篇 |
2005年 | 52篇 |
2004年 | 35篇 |
2003年 | 26篇 |
2002年 | 22篇 |
2001年 | 6篇 |
2000年 | 11篇 |
1999年 | 6篇 |
1998年 | 6篇 |
1997年 | 7篇 |
1996年 | 4篇 |
1995年 | 3篇 |
1994年 | 1篇 |
1992年 | 6篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 3篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1976年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有836条查询结果,搜索用时 15 毫秒
831.
Jade Vaccari María Jos Gonzlez-Soria Nicholas Carter Beatriz Maci 《Molecules (Basel, Switzerland)》2021,26(15)
A catalytic methodology for the enantioselective addition of alkylzirconium reagents to aliphatic aldehydes is reported here. The versatile and readily accessible chiral Ph-BINMOL ligand, in the presence of Ti(OiPr)4 and a zinc salt, facilitates the reaction, which proceeds under mild conditions and is compatible with functionalized nucleophiles. The alkylzirconium reagents are conveniently generated in situ by hydrozirconation of alkenes with the Schwartz reagent. This work is a continuation of our previous work on aromatic aldehydes. 相似文献
832.
We describe herein an efficient method for the synthesis of unsymmetrically-substituted biphenyls using a sonochemical variation of the Stille coupling, whose results have also been compared with the conventional silent reaction. Ultrasound significantly enhances this useful organometallic transformation affording products in higher yields and in shorter reaction times than non-irradiated reactions. The scope has been explored with a selection of arylstannanes as precursors and, remarkably, no by-products resulting from homo-coupling could be detected. 相似文献
833.
Patricia Lam Chitra Vinnakota Beatriz Calvo-Flores Guzmn Julia Newland Katie Peppercorn Warren P. Tate Henry J. Waldvogel Richard L. M. Faull Andrea Kwakowsky 《Molecules (Basel, Switzerland)》2022,27(8)
Alzheimer’s disease (AD) is a neurodegenerative disorder with an increasing need for developing disease-modifying treatments as current therapies only provide marginal symptomatic relief. Recent evidence suggests the γ-aminobutyric acid (GABA) neurotransmitter system undergoes remodeling in AD, disrupting the excitatory/inhibitory (E/I) balance in the brain. Altered expression levels of K-Cl-2 (KCC2) and N-K-Cl-1 (NKCC1), which are cation–chloride cotransporters (CCCs), have been implicated in disrupting GABAergic activity by regulating GABAA receptor signaling polarity in several neurological disorders, but these have not yet been explored in AD. NKCC1 and KCC2 regulate intracellular chloride [Cl−]i by accumulating and extruding Cl−, respectively. Increased NKCC1 expression in mature neurons has been reported in these disease conditions, and bumetanide, an NKCC1 inhibitor, is suggested to show potential therapeutic benefits. This study used primary mouse hippocampal neurons to explore if KCC2 and NKCC1 expression levels are altered following beta-amyloid (Aβ1-42) treatment and the potential neuroprotective effects of bumetanide. KCC2 and NKCC1 expression levels were also examined in 18-months-old male C57BL/6 mice following bilateral hippocampal Aβ1-42 stereotaxic injection. No change in KCC2 and NKCC1 expression levels were observed in mouse hippocampal neurons treated with 1 nM Aβ1-42, but NKCC1 expression increased 30-days post-Aβ1-42-injection in the CA1 region of the mouse hippocampus. Primary mouse hippocampal cultures were treated with 1 nM Aβ1-42 alone or with various concentrations of bumetanide (1 µM, 10 µM, 100 µM, 1 mM) to investigate the effect of the drug on cell viability. Aβ1-42 produced 53.1 ± 1.4% cell death after 5 days, and the addition of bumetanide did not reduce this. However, the drug at all concentrations significantly reduced cell viability, suggesting bumetanide is highly neurotoxic. In summary, these results suggest that chronic exposure to Aβ1-42 alters the balance of KCC2 and NKCC1 expression in a region-and layer-specific manner in mouse hippocampal tissue; therefore, this process most likely contributes to altered hippocampal E/I balance in this model. Furthermore, bumetanide induces hippocampal neurotoxicity, thus questioning its suitability for AD therapy. Further investigations are required to examine the effects of Aβ1-42 on KCC2 and NKCC1 expression and whether targeting CCCs might offer a therapeutic approach for AD. 相似文献
834.
L. Beatriz Castro-Gómez Dr. José Campos-Martínez Dr. Marta I. Hernández Dr. Ramón Hernández-Lamoneda 《Chemphyschem》2023,24(23):e202300387
We present a detailed theoretical study of the molecular oxygen trimer where the potential energy surfaces of the seven multiplet states have been calculated by means of a pair approximation with very accurate dimer ab initio potentials. In order to obtain all the states a matrix representation of the potential using the uncoupled spin representation has been applied. The and states are nearly degenerate and low-lying isomers appear for most multiplicities. A crucial point in deciding the relative stabilities is the zero-point energy which represents a sizable fraction of the electronic well-depth. Therefore, we have performed accurate diffusion Monte Carlo studies of the lowest state in each multiplicity. Analysis of the wavefunction allows a deeper interpretation of the cluster structures, finding that they are significantly floppy in most cases. 相似文献
835.
Rafaela Osuna-Gómez Tiago Mendonca da Costa Beatriz Hernández-Jiménez Gabriel Ruiz-Garzón 《Mathematical Methods in the Applied Sciences》2023,46(2):2319-2333
This paper presents necessary and sufficient conditions for generalized Hukuhara differentiability of interval-valued functions and counterexamples of some equivalences previously presented in the literature, for which important results are based on. Moreover, applications of interval generalized Hukuhara differentiability are presented. 相似文献
836.