全文获取类型
收费全文 | 5733篇 |
免费 | 200篇 |
国内免费 | 16篇 |
专业分类
化学 | 4222篇 |
晶体学 | 37篇 |
力学 | 73篇 |
数学 | 894篇 |
物理学 | 723篇 |
出版年
2021年 | 64篇 |
2020年 | 70篇 |
2019年 | 70篇 |
2018年 | 44篇 |
2017年 | 50篇 |
2016年 | 139篇 |
2015年 | 124篇 |
2014年 | 137篇 |
2013年 | 226篇 |
2012年 | 293篇 |
2011年 | 322篇 |
2010年 | 221篇 |
2009年 | 217篇 |
2008年 | 308篇 |
2007年 | 249篇 |
2006年 | 283篇 |
2005年 | 234篇 |
2004年 | 247篇 |
2003年 | 190篇 |
2002年 | 170篇 |
2001年 | 48篇 |
2000年 | 44篇 |
1998年 | 44篇 |
1997年 | 71篇 |
1996年 | 75篇 |
1995年 | 72篇 |
1994年 | 69篇 |
1993年 | 61篇 |
1992年 | 65篇 |
1991年 | 69篇 |
1990年 | 57篇 |
1989年 | 55篇 |
1988年 | 62篇 |
1987年 | 56篇 |
1986年 | 66篇 |
1985年 | 86篇 |
1984年 | 96篇 |
1983年 | 58篇 |
1982年 | 75篇 |
1981年 | 95篇 |
1980年 | 74篇 |
1979年 | 67篇 |
1978年 | 83篇 |
1977年 | 46篇 |
1976年 | 72篇 |
1975年 | 56篇 |
1973年 | 58篇 |
1971年 | 42篇 |
1970年 | 33篇 |
1962年 | 36篇 |
排序方式: 共有5949条查询结果,搜索用时 15 毫秒
21.
Jan Matthias Peschel Liên Sabrina Reichel Tim Hoffmann Christoph Enzensperger Ulrich Sigmar Schubert Anja Traeger Michael Gottschaldt 《Macromolecular bioscience》2023,23(12):2300135
Branched poly(ethylene imine) (bPEI) is frequently used in RNA interference (RNAi) experiments as a cationic polymer for the delivery of small interfering RNA (siRNA) because of its ability to form stable polyplexes that facilitate siRNA uptake. However, the use of bPEI in gene delivery is limited by its cytotoxicity and a need for target specificity. In this work, bPEI is modified with d- fructose to improve biocompatibility and target breast cancer cells through the overexpressed GLUT5 transporter. Fructose-substituted bPEI (Fru−bPEI) is accessible in three steps starting from commercially available protected fructopyranosides and bPEI. Several polymers with varying molecular weights, degrees of substitution, and linker positions on d- fructose (C1 and C3) are synthesized and characterized with NMR spectroscopy, size exclusion chromatography, and elemental analysis. In vitro biological screenings show significantly reduced cytotoxicity of 10 kDa bPEI after fructose functionalization, specific uptake of siRNA polyplexes, and targeted knockdown of green fluorescent protein (GFP) in triple-negative breast cancer cells (MDA-MB-231) compared to noncancer cells (HEK293T). 相似文献
22.
Micelle‐Triggered β‐Hairpin to α‐Helix Transition in a 14‐Residue Peptide from a Choline‐Binding Repeat of the Pneumococcal Autolysin LytA 下载免费PDF全文
Héctor Zamora‐Carreras Dr. Beatriz Maestro Dr. Erik Strandberg Prof. Anne S. Ulrich Dr. Jesús M. Sanz Dr. M. Ángeles Jiménez 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(22):8076-8089
Choline‐binding modules (CBMs) have a ββ‐solenoid structure composed of choline‐binding repeats (CBR), which consist of a β‐hairpin followed by a short linker. To find minimal peptides that are able to maintain the CBR native structure and to evaluate their remaining choline‐binding ability, we have analysed the third β‐hairpin of the CBM from the pneumococcal LytA autolysin. Circular dichroism and NMR data reveal that this peptide forms a highly stable native‐like β‐hairpin both in aqueous solution and in the presence of trifluoroethanol, but, strikingly, the peptide structure is a stable amphipathic α‐helix in both zwitterionic (dodecylphosphocholine) and anionic (sodium dodecylsulfate) detergent micelles, as well as in small unilamellar vesicles. This β‐hairpin to α‐helix conversion is reversible. Given that the β‐hairpin and α‐helix differ greatly in the distribution of hydrophobic and hydrophilic side chains, we propose that the amphipathicity is a requirement for a peptide structure to interact and to be stable in micelles or lipid vesicles. To our knowledge, this “chameleonic” behaviour is the only described case of a micelle‐induced structural transition between two ordered peptide structures. 相似文献
23.
24.
Textile/Metal–Organic‐Framework Composites as Self‐Detoxifying Filters for Chemical‐Warfare Agents 下载免费PDF全文
Elena López‐Maya Dr. Carmen Montoro Dr. L. Marleny Rodríguez‐Albelo Dr. Salvador D. Aznar Cervantes Dr. A. Abel Lozano‐Pérez Prof. José Luis Cenís Dr. Elisa Barea Prof. Jorge A. R. Navarro 《Angewandte Chemie (International ed. in English)》2015,54(23):6790-6794
The current technology of air‐filtration materials for protection against highly toxic chemicals, that is, chemical‐warfare agents, is mainly based on the broad and effective adsorptive properties of hydrophobic activated carbons. However, adsorption does not prevent these materials from behaving as secondary emitters once they are contaminated. Thus, the development of efficient self‐cleaning filters is of high interest. Herein, we report how we can take advantage of the improved phosphotriesterase catalytic activity of lithium alkoxide doped zirconium(IV) metal–organic framework (MOF) materials to develop advanced self‐detoxifying adsorbents of chemical‐warfare agents containing hydrolysable P? F, P? O, and C? Cl bonds. Moreover, we also show that it is possible to integrate these materials onto textiles, thereby combining air‐permeation properties of the textiles with the self‐detoxifying properties of the MOF material. 相似文献
25.
Inside Cover: Textile/Metal–Organic‐Framework Composites as Self‐Detoxifying Filters for Chemical‐Warfare Agents (Angew. Chem. Int. Ed. 23/2015) 下载免费PDF全文
26.
Locked by Design: A Conformationally Constrained Transglutaminase Tag Enables Efficient Site‐Specific Conjugation 下载免费PDF全文
Dr. Vanessa Siegmund Dr. Stefan Schmelz Stephan Dickgiesser Jan Beck Aileen Ebenig Heiko Fittler Dr. Holm Frauendorf Dr. Birgit Piater Dr. Ulrich A. K. Betz Dr. Olga Avrutina Dr. Andrea Scrima Prof. Dr. Hans‐Lothar Fuchsbauer Prof. Dr. Harald Kolmar 《Angewandte Chemie (International ed. in English)》2015,54(45):13420-13424
Based on the crystal structure of a natural protein substrate for microbial transglutaminase, an enzyme that catalyzes protein crosslinking, a recognition motif for site‐specific conjugation was rationally designed. Conformationally locked by an intramolecular disulfide bond, this structural mimic of a native conjugation site ensured efficient conjugation of a reporter cargo to the therapeutic monoclonal antibody cetuximab without erosion of its binding properties. 相似文献
27.
28.
29.
30.
Dr. Ulrich P. Preiss Dr. Dzmitry H. Zaitsau Dr. Witali Beichel Dr. Daniel Himmel Dr. Alexander Higelin Dr. Klaus Merz Niklas Caesar Prof. Dr. Sergey P. Verevkin 《Chemphyschem》2015,16(13):2890-2898
New measurements of vaporization enthalpies for 15 1:1 ionic liquids are performed by using a quartz‐crystal microbalance. Collection and analysis of 33 available crystal structures of organic salts, which comprise 13 different cations and 12 anions, is performed. Their dissociation lattice enthalpies are calculated by a combination of experimental and quantum chemical quantities and are divided into the relaxation and Coulomb components to give an insight into elusive short‐range interaction enthalpies. An empirical equation is developed, based on interaction‐specific Hirshfeld surfaces and solvation enthalpies, which enables the estimation of the lattice enthalpy by using only the crystal‐structure data. 相似文献