全文获取类型
收费全文 | 1962篇 |
免费 | 71篇 |
国内免费 | 8篇 |
专业分类
化学 | 1390篇 |
晶体学 | 19篇 |
力学 | 74篇 |
数学 | 290篇 |
物理学 | 268篇 |
出版年
2023年 | 19篇 |
2022年 | 37篇 |
2021年 | 42篇 |
2020年 | 55篇 |
2019年 | 40篇 |
2018年 | 31篇 |
2017年 | 25篇 |
2016年 | 55篇 |
2015年 | 49篇 |
2014年 | 68篇 |
2013年 | 117篇 |
2012年 | 129篇 |
2011年 | 172篇 |
2010年 | 74篇 |
2009年 | 77篇 |
2008年 | 135篇 |
2007年 | 134篇 |
2006年 | 109篇 |
2005年 | 113篇 |
2004年 | 95篇 |
2003年 | 98篇 |
2002年 | 105篇 |
2001年 | 22篇 |
2000年 | 16篇 |
1999年 | 21篇 |
1998年 | 25篇 |
1997年 | 26篇 |
1996年 | 22篇 |
1995年 | 16篇 |
1994年 | 14篇 |
1993年 | 14篇 |
1992年 | 12篇 |
1991年 | 8篇 |
1989年 | 9篇 |
1988年 | 4篇 |
1987年 | 5篇 |
1986年 | 2篇 |
1985年 | 9篇 |
1984年 | 5篇 |
1983年 | 2篇 |
1982年 | 5篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1974年 | 2篇 |
1895年 | 1篇 |
1887年 | 2篇 |
排序方式: 共有2041条查询结果,搜索用时 15 毫秒
941.
N4‐Methylation of Cytosine Drastically Favors the Formation of (6‐4) Photoproducts in a TCG Context 下载免费PDF全文
Thierry Douki Jarah A. Meador Izabel Bérard Aude Wack 《Photochemistry and photobiology》2015,91(1):102-108
Methylation of cytosine is a common biological process both in prokaryotic and eukaryotic cells. In addition to 5‐methylcytosine (5mC), some bacterial species contain in their genome N4‐methylcytosine (N4mC). Methylation at C5 has been shown to enhance the formation of pyrimidine dimeric photoproducts but nothing is known of the effect of N4 methylation on UV‐induced DNA damage. In the present work, we compared the yield and the nature of bipyrimidine photoproducts induced in a series of trinucleotides exhibiting a TXG sequence where X is either T, C, 5mC or N4mC. HPLC associated to tandem mass spectrometry was used to quantify cyclobutane pyrimidine dimers (CPD), (6‐4) photoproducts (64PP) and their Dewar valence isomer. Methylation at position N4 was found to drastically increase the reactivity of C upon exposure to both UVC and UVB and to favor the formation of 64PP. In contrast methylation at C5 increased the yield of CPD at the expense of 64PP. In addition, enhancement of photoreactivity by C5 methylation was much higher in the UVB than in the UVC range. These results show the drastic effect of the methylation site on the photochemistry of cytosine. 相似文献
942.
Design and Synthesis of New Hybrid Molecules That Activate the Transcription Factor Nrf2 and Simultaneously Release Carbon Monoxide 下载免费PDF全文
Dr. Jayne Louise Wilson Sarah Fayad Kobeissi Dr. Souhila Oudir Dr. Benjamin Haas Dr. Brian Michel Prof. Jean‐Luc Dubois Randé Dr. Anthony Ollivier Prof. Thierry Martens Dr. Michael Rivard Dr. Roberto Motterlini Dr. Roberta Foresti 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(45):14698-14704
943.
Nadia Mustapha Inès Bouhlel Fadwa Chaabane Imèn Mokdad Bzéouich Kamel Ghedira Thierry Hennebelle Leila Chekir-Ghedira 《Applied biochemistry and biotechnology》2014,172(4):2266-2275
The present study was carried out to characterize the cellular antioxidant effect of the aqueous extract of Crataegus azarolus and its antigenotoxic potential using human myelogenous cells, K562. The antioxidant capacity of this extract was evaluated by determining its cellular antioxidant activity (CAA) in K562 cells. Also, preceding antigenotoxicity assessment, its eventual genotoxicity property was investigated by evaluating its capacity to induce the DNA degradation of treated cell nuclei. As no genotoxicity was detected at different exposure times, its ability to protect cell DNA against H2O2 oxidative effect was investigated, using the “comet assay.” It appears that 800 μg/mL of extract inhibited the genotoxicity induced by H2O2 with a rate of 41.30 %, after 4 h of incubation. In addition, this extract revealed a significant cellular antioxidant capacity against the reactive oxygen species in K562 cells. 相似文献
944.
Binauld S Damiron D Hamaide T Pascault JP Fleury E Drockenmuller E 《Chemical communications (Cambridge, England)》2008,(35):4138-4140
A novel step growth polymerization A-B strategy based on the click chemistry polyaddition of tailor-made alpha-azide-omega-alkyne low molar mass monomers was developed, leading to polytriazole (co)polymers with tunable structures and properties. 相似文献
945.
Goll E Leininger T Manby FR Mitrushchenkov A Werner HJ Stoll H 《Physical chemistry chemical physics : PCCP》2008,10(23):3353-3357
We introduce local and density fitting approximations into a hybrid approach which couples short-range density functionals with long-range wave-functions. The use of density fitting methods within the local-correlation approximation makes it possible to tackle bigger systems than without these methods, so that we are now able to treat systems of biological interest within the DFT/ab initio scheme. In first benchmark calculations, we apply it to the S22 database of Hobza and co-workers for binding energies of weakly bound molecular clusters. 相似文献
946.
947.
The alkylation reactions of an amide enolate derived from a trifluoromethylated oxazolidine (Fox) chiral auxiliary occur with a complete diastereoselectivity and in good yields with various electrophiles. This reaction provides a versatile and straightforward strategy for the synthesis of beta(2)-amino acids and gamma-amino alcohols in enantiopure form. 相似文献
948.
949.
Felix Houard Quentin Evrard Guillaume Calvez Yan Suffren Carole Daiguebonne Olivier Guillou Frdric Gendron Boris Le Guennic Thierry Guizouarn Vincent Dorcet Matteo Mannini Kevin Bernot 《Angewandte Chemie (International ed. in English)》2020,59(2):780-784
We report a single‐chain magnet (SCM) made of a terbium(III) building block and a nitronyl‐nitroxide radical (NIT) functionalized with an aliphatic chain. This substitution is targeted to induce a long‐range distortion of the polymeric chain and accordingly it gives rise to chains that are curled with almost 20 nm helical pitch. They self‐organize as a chiral tubular superstructure made of 11 chains wound around each other. The supramolecular tubes have a 4.5 nm internal diameter. Overall, this forms a porous chiral network with almost 44 % porosity. Ab initio calculations highlight that each TbIII ion possesses high magnetic anisotropy. Indeed, notwithstanding the supramolecular arrangement each chain behaves as a SCM. Magnetic relaxation with both finite and infinite‐size regimes is observed and confirms the validity of the Ising approximation. This is associated with quite strong coercive field and magnetic remanence (Hc=2400 Oe MR=2.09 μB at 0.5 K) for this class of compounds. 相似文献
950.
Florent Monie Bruno Grignard Jean‐Michel Thomassin Raphael Mereau Thierry Tassaing Christine Jerome Christophe Detrembleur 《Angewandte Chemie (International ed. in English)》2020,59(39):17033-17041
Polyurethane (PU) foams are indisputably daily essential materials found in many applications, notably for comfort (for example, matrasses) or energy saving (for example, thermal insulation). Today, greener routes for their production are intensively searched for to avoid the use of toxic isocyanates. An easily scalable process for the simple construction of self‐blown isocyanate‐free PU foams by exploiting the organocatalyzed chemo‐ and regioselective additions of amines and thiols to easily accessible cyclic carbonates is described. These reactions are first validated on model compounds and rationalized by DFT calculations. Various foams are then prepared and characterized in terms of morphology and mechanical properties, and the scope of the process is illustrated by modulating the composition of the reactive formulation. With impressive diversity and accessibility of the main components of the formulations, this new robust and solvent‐free process could open avenues for construction of more sustainable PU foams, and offers the first realistic alternative to the traditional isocyanate route. 相似文献