全文获取类型
收费全文 | 2536篇 |
免费 | 107篇 |
国内免费 | 23篇 |
专业分类
化学 | 1697篇 |
晶体学 | 16篇 |
力学 | 66篇 |
数学 | 361篇 |
物理学 | 526篇 |
出版年
2023年 | 26篇 |
2022年 | 39篇 |
2021年 | 55篇 |
2020年 | 66篇 |
2019年 | 78篇 |
2018年 | 54篇 |
2017年 | 56篇 |
2016年 | 98篇 |
2015年 | 55篇 |
2014年 | 69篇 |
2013年 | 134篇 |
2012年 | 166篇 |
2011年 | 195篇 |
2010年 | 109篇 |
2009年 | 69篇 |
2008年 | 136篇 |
2007年 | 178篇 |
2006年 | 158篇 |
2005年 | 121篇 |
2004年 | 104篇 |
2003年 | 80篇 |
2002年 | 54篇 |
2001年 | 30篇 |
2000年 | 35篇 |
1999年 | 42篇 |
1998年 | 21篇 |
1997年 | 27篇 |
1996年 | 25篇 |
1995年 | 14篇 |
1994年 | 10篇 |
1993年 | 16篇 |
1992年 | 20篇 |
1991年 | 11篇 |
1990年 | 11篇 |
1989年 | 18篇 |
1988年 | 21篇 |
1987年 | 10篇 |
1985年 | 19篇 |
1984年 | 16篇 |
1983年 | 9篇 |
1982年 | 9篇 |
1981年 | 17篇 |
1980年 | 14篇 |
1979年 | 12篇 |
1978年 | 17篇 |
1977年 | 9篇 |
1976年 | 12篇 |
1974年 | 9篇 |
1973年 | 7篇 |
1887年 | 6篇 |
排序方式: 共有2666条查询结果,搜索用时 343 毫秒
131.
Kaiprathu Anjali Velayudham Parthiban Teller Hanan Schechter Alex 《Journal of Solid State Electrochemistry》2022,26(9):1897-1917
Journal of Solid State Electrochemistry - Electrocatalytic nitrogen reduction reaction (E-NRR) to ammonia is becoming a major topic of interest in the field of large-scale energy storage from... 相似文献
132.
Jakkarin Limwongyut Dr. Alex S. Moreland Dr. Chenyao Nie Prof. Javier Read de Alaniz Prof. Guillermo C. Bazan 《ChemistryOpen》2022,11(2):e202100260
Cationic conjugated oligoelectrolytes (COEs) are a class of compounds that can be tailored to achieve relevant in vitro antimicrobial properties with relatively low cytotoxicity against mammalian cells. Three distyrylbenzene-based COEs were designed containing amide functional groups on the side chains. Their properties were compared to two representative COEs with only quaternary ammonium groups. The optimal compound, COE2−3C−C3-Apropyl , has an antimicrobial efficacy against Escherichia coli with an MIC=2 μg mL−1, even in the presence of human serum albumin low cytotoxicity (IC50=740 μg mL−1) and minimal hemolytic activity. Moreover, we find that amide groups increase interactions between COEs and a bacterial lipid mimic based on calcein leakage assay and allow COEs to readily permeabilize the cytoplasmic membrane of E. coli. These findings suggest that hydrogen bond forming moieties can be further applied in the molecular design of antimicrobial COEs to further improve their selectivity towards bacteria. 相似文献
133.
Melissa M. Cadelis Soeren Geese Benedict B. Uy Daniel R. Mulholland Shara J. van de Pas Alex Grey Bevan S. Weir Brent R. Copp Siouxsie Wiles 《Molecules (Basel, Switzerland)》2021,26(4)
Antimicrobial bioassay-guided fractionation of the endophytic fungi Neofusicoccum australe led to the isolation of a new unsymmetrical naphthoquinone dimer, neofusnaphthoquinone B (1), along with four known natural products (2–5). Structure elucidation was conducted by nuclear magnetic resonance (NMR) spectroscopic methods, and the antimicrobial activity of all the natural products was investigated, revealing 1 to be moderately active towards methicillin-resistant Staphylococcus aureus (MRSA) with a minimum inhibitory concentration (MIC) of 16 µg/mL. 相似文献
134.
Many natural and artificial two-states signaling devices are connected forming networks. The information-processing potential of these systems is usually related to the response to weak external signals. Here, using a network of overdamped bistable elements, we study the effect of a heterogeneous complex topology on the signal response. The analysis of the problem in random scale-free networks, reveals that heterogeneity plays a crucial role in amplifying external signals. We have contrasted numerical simulations with analytical calculations in simplified topologies. 相似文献
135.
Paths to synchronization on complex networks 总被引:1,自引:0,他引:1
The understanding of emergent collective phenomena in natural and social systems has driven the interest of scientists from different disciplines during decades. Among these phenomena, the synchronization of a set of interacting individuals or units has been intensively studied because of its ubiquity in the natural world. In this Letter, we show how for fixed coupling strengths local patterns of synchronization emerge differently in homogeneous and heterogeneous complex networks, driving the process towards a certain global synchronization degree following different paths. The dependence of the dynamics on the coupling strength and on the topology is unveiled. This study provides a new perspective and tools to understand this emerging phenomena. 相似文献
136.
Granwehr J Harel E Hilty C Garcia S Chavez L Pines A Sen PN Song YQ 《Magnetic resonance imaging》2007,25(4):449-452
Remote detection nuclear magnetic resonance and magnetic resonance imaging can be used to study fluid flow and dispersion in a porous medium from a purely Eulerian point of view (i.e., in a laboratory frame of reference). Information about fluid displacement is obtained on a macroscopic scale in a long-time regime, while local velocity distributions are averaged out. It is shown how these experiments can be described using the common flow propagator formalism and how experimental data can be analyzed to obtain effective porosity, flow velocity inside the porous medium, fluid dispersion and flow tracing of fluid. 相似文献
137.
138.
Zhibo Liu Maral Pourghiasian Mark Alex Radtke Joseph Lau Dr. Jinhe Pan Gemma M. Dias Dr. Donald Yapp Dr. Kuo‐Shyan Lin Prof. Dr. Francois Bénard Prof. Dr. David M. Perrin 《Angewandte Chemie (International ed. in English)》2014,53(44):11876-11880
A new zwitterionic organotrifluoroborate is appended to three radiosynthons that afford undergo facile bioconjugation to several clinically relevant peptides and one enzyme inhibitor. Molecularly complex bioconjugates are 18F‐labeled in a single aqueous step in rapid time (<15 min) without HPLC purification to afford tracers in good yields (>200 mCi, 20–40 %) at high specific activity (≥3 Ci/μmol) and at >98 % purity. PET imaging shows in vivo stability and tumor uptake. 相似文献
139.
Roselis A. Landaeta Aponte Andreas Luxenburger Scott A. Cameron Alex Weymouth-Wilson Richard H. Furneaux Lawrence D. Harris Benjamin J. Compton 《Molecules (Basel, Switzerland)》2022,27(7)
Bile acid receptors have been identified as important targets for the development of new therapeutics to treat various metabolic and inflammatory diseases. The synthesis of new bile acid analogues can help elucidate structure–activity relationships and define compounds that activate these receptors selectively. Towards this, access to large quantities of a chenodeoxycholic acid derivative bearing a C-12 methyl and a C-13 to C-14 double bond provided an interesting scaffold to investigate the chemical manipulation of the C/D ring junction in bile acids. The reactivity of this alkene substrate with various zinc carbenoid species showed that those generated using the Furukawa methodology achieved selective α-cyclopropanation, whereas those generated using the Shi methodology reacted in an unexpected manner giving rise to a rearranged skeleton whereby the C ring has undergone contraction to form a novel spiro–furan ring system. Further derivatization of the cyclopropanated steroid included O-7 oxidation and epimerization to afford new bile acid derivatives for biological evaluation. 相似文献
140.
Manoel Raimundo dos Santos Junior Elinia Castro Costa Caio Campos Ferreira Lucas Pinto Bernar Marcilene Paiva da Silva Andria de Andrade Mncio Marcelo Costa Santos Sílvio Alex Pereira da Mota Douglas Alberto Rocha de Castro Sergio Duvoisin Junior Luiz Eduardo Pizarro Borges Marilena Emmi Araújo Nlio Teixeira Machado 《Molecules (Basel, Switzerland)》2022,27(7)
In this work, the deoxygenation of organic liquid products (OLP) obtained through the thermal catalytic cracking of palm oil at 450 °C, 1.0 atmosphere, with 10% (wt.) Na2CO3 as a catalyst, in multistage countercurrent absorber columns using supercritical carbon dioxide (SC-CO2) as a solvent, with an Aspen-HYSYS process simulator, was systematically investigated. In a previous study, the thermodynamic data basis and EOS modeling necessary to simulate the deoxygenation of OLP was presented. This work addresses a new flowsheet, consisting of 03 absorber columns, 10 expansions valves, 10 flash drums, 08 heat exchanges, 01 pressure pump, and 02 make-ups of CO2, aiming to improve the deacidification of OLP. The simulation was performed at 333 K, 140 bar, and (S/F) = 17; 350 K, 140 bar, and (S/F) = 38; 333 K, 140 bar, and (S/F) = 25. The simulation shows that 81.49% of OLP could be recovered and that the concentrations of hydrocarbons in the extracts of absorber-01 and absorber-02 were 96.95 and 92.78% (wt.) on a solvent-free basis, while the bottom stream of absorber-03 was enriched in oxygenated compounds with concentrations of up to 32.66% (wt.) on a solvent-free basis, showing that the organic liquid products (OLP) were deacidified and SC-CO2 was able to deacidify the OLP and obtain fractions with lower olefin contents. The best deacidifying condition was obtained at 333 K, 140 bar, and (S/F) = 17. 相似文献