全文获取类型
收费全文 | 3068篇 |
免费 | 125篇 |
国内免费 | 16篇 |
专业分类
化学 | 1906篇 |
晶体学 | 5篇 |
力学 | 131篇 |
数学 | 617篇 |
物理学 | 550篇 |
出版年
2024年 | 3篇 |
2023年 | 33篇 |
2022年 | 95篇 |
2021年 | 128篇 |
2020年 | 73篇 |
2019年 | 92篇 |
2018年 | 69篇 |
2017年 | 52篇 |
2016年 | 116篇 |
2015年 | 114篇 |
2014年 | 126篇 |
2013年 | 193篇 |
2012年 | 229篇 |
2011年 | 256篇 |
2010年 | 150篇 |
2009年 | 112篇 |
2008年 | 209篇 |
2007年 | 175篇 |
2006年 | 165篇 |
2005年 | 167篇 |
2004年 | 120篇 |
2003年 | 108篇 |
2002年 | 98篇 |
2001年 | 44篇 |
2000年 | 36篇 |
1999年 | 27篇 |
1998年 | 16篇 |
1997年 | 30篇 |
1996年 | 22篇 |
1995年 | 18篇 |
1994年 | 16篇 |
1993年 | 18篇 |
1992年 | 8篇 |
1991年 | 3篇 |
1990年 | 8篇 |
1989年 | 8篇 |
1988年 | 4篇 |
1986年 | 6篇 |
1985年 | 6篇 |
1984年 | 10篇 |
1983年 | 8篇 |
1982年 | 4篇 |
1981年 | 5篇 |
1980年 | 5篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1974年 | 3篇 |
1937年 | 2篇 |
排序方式: 共有3209条查询结果,搜索用时 15 毫秒
81.
Tinuccia Dettori Giuseppina Sanna Andrea Cocco Gabriele Serreli Monica Deiana Vanessa Palmas Valentina Onnis Luca Pilia Nicola Melis Davide Moi Paola Caria Francesco Secci 《Molecules (Basel, Switzerland)》2022,27(24)
A series of 6- and 6,8-halocoumarin derivatives have been investigated as potential antiproliferative compounds against a panel of tumor and normal cell lines. Cytotoxic effects were determined by the MTT method. To investigate the potential molecular mechanism involved in the cytotoxic effect, apoptosis assay, cell cycle analysis, reactive oxygen species (ROS), and reduced glutathione analysis were performed. Among the screened compounds, coumarins 6,8-dibromo-2-oxo-2H-chromene-3-carbonitrile 2h and 6,8-diiodo-2-oxo-2H-chromene-3-carbonitrile 2k exhibited the most antiproliferative effect in thyroid cancer-derived cells TPC-1. The apoptosis assay showed that both 2h and 2k induced apoptosis in TPC-1 thyroid cancer cells. According to these experiments, both coumarins induced a slight increase in TPC-1 cells in the G2/M phase and a decrease in the S phase. A significant increase in ROS levels was observed in TPC-1 treated with diiodocoumarin 2k, while the dibromocoumarin 2h induced a decrease in ROS in a dose and time-dependent manner. 相似文献
82.
83.
Chao Li Yingying Wang Hongyan Li Jing Liu Jianping Song Luca Fusaro Zhi-Yi Hu Yanxin Chen Yu Li Bao-Lian Su 《Journal of Energy Chemistry》2021,(8):396-404
Lithium-selenium (Li-Se) battery has attracted growing attention.Nevertheless,its practical application is still impeded by the shuttle effect of the formed pol... 相似文献
84.
Dr. Luca Scapinello Sara Grecchi Dr. Sergio Rossi Prof. Fabiana Arduini Dr. Serena Arnaboldi Prof. Andrea Penoni Dr. Roberto Cirilli Prof. Patrizia Romana Mussini Prof. Tiziana Benincori 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(52):13190-13202
A family of inherently chiral electroactive selectors based on the 2,2’-biindole atropisomeric scaffold, of easy synthesis and modulable functional properties, is studied in cascade in two enantioselection contexts. They are at first investigated as probes in enantioselective HPLC, studying molecular structure and temperature effects, and achieving very efficient semipreparative enantioseparation. The enantiomers thus obtained, of remarkable chiroptical features (optical rotation as well as circular dichroism), are successfully applied as selectors in chiral voltammetry in different media for discrimination of the enantiomers of chiral electroactive probes, either by conversion into enantiopure electroactive electrode surfaces by electrooligomerization on glassy carbon substrate (the two monomers with shorter alkyl chains), or as chiral additive in achiral ionic liquid (the monomer with longest alkyl chains). Discrimination is conveniently and reproducibly achieved in terms of significant potential differences for the two enantiomers, specularly inverting either probe or selector configuration. In one case successful discrimination is also observed with the two probe enantiomers concurrently present, either as racemate or with enantiomeric excesses, neatly accounted for by the peak current ratios. 相似文献
85.
Chiara Capolungo Dr. Damiano Genovese Prof. Marco Montalti Prof. Enrico Rampazzo Prof. Nelsi Zaccheroni Prof. Luca Prodi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(70):17529-17541
The growing numbers related to plastic pollution are impressive, with ca. 70 % of produced plastic (>350 tonnes/year) being indiscriminately wasted in the environment. The most dangerous forms of plastic pollution for biota and human health are micro- and nano-plastics (MNPs), which are ubiquitous and more bioavailable. Their elimination is extremely difficult, but the first challenge is their detection since existing protocols are unsatisfactory for microplastics and mostly absent for nanoplastics. After a discussion of the state of the art for MNPs detection, we specifically revise the techniques based on photoluminescence that represent very promising solutions for this problem. In this context, Nile Red staining is the most used strategy and we show here its pros and limitations, but we also discuss other more recent approaches, such as the use of fluorogenic probes based on perylene-bisimide and on fluorogenic hyaluronan nanogels, with the added values of biocompatibility and water solubility. 相似文献
86.
In this study, the Schrodinger equation of a valence electron in a periodic crystal potential is formulated and solved using the elliptic function formalism. The method allows double-periodic lattice planes to be represented in the Gauss plane. The reality of the obtained eigenfunctions and the structure of the valence and conduction bands are also investigated.
相似文献87.
Dr. Robert Ludmerczki Prof. Luca Malfatti Dr. Luigi Stagi Dr. Manuela Meloni Prof. Carlo Maria Carbonaro Prof. Maria Francesca Casula Dr. Dóra Bogdán Dr. Stefania Mura Prof. István M. Mándity Prof. Plinio Innocenzi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(7):2543-2550
Carbonized polymer dots (CPDs), a peculiar type of carbon dots, show extremely high quantum yields, making them very attractive nanostructures for application in optics and biophotonics. The origin of the strong photoluminescence of CPDs resides in a complicated interplay of several radiative mechanisms. To understand the correlation between CPD processing and properties, the early stage formation of carbonized polymer dots has been studied. In the synthesis, citric acid monohydrate and 2-amino-2-(hydroxymethyl)propane-1,3-diol have been thermally degraded at 180 °C. The use of an oil bath instead of a more traditional hydrothermal reactor has allowed the CPD properties to be monitored at different reactions times. Transmission electron microscopy, time-resolved photoluminescence, nuclear magnetic resonance, infrared, and Raman spectroscopy have revealed the formation of polymeric species with amide and ester bonds. Quantum chemistry calculations have been employed to investigate the origin of CPD electronic transitions. At short reaction times, amorphous C-dots with 80 % quantum yield, have been obtained. 相似文献
88.
89.
90.
Abstract The compound 4-cyano-4′-(α,α,α-trifluoromethoxy)biphenyl (1OCBF3) has been synthesized. Unlike the fully protonated analogue, 4-cyano-4′-methoxybiphenyl (1OCB), it does not show a liquid crystalline phase on cooling from the melting point (51°C) to room temperature. The transition temperature to a monotropic nematic phase was obtained as approximately 0°C by determining the transition temperatures of mixtures with 1OCB. The structures, conformational properties and orientational ordering of both 1OCB and 1OCBF3 as solutes in a nematic solvent ZLI 1132 have been investigated via the 17 dipolar couplings obtained by analysing the proton and fluorine NMR spectra of these solutions. It is concluded that the major difference between the two molecules lies in the potential, V(φ2), governing rotation about the ring–oxygen bonds. In 1OCB the potential has the same form as in anisole, with a minimum when the C–O bond is in the plane of the attached ring (φ2 = 0°), and a maximum of about 15 kJ mol?1 when φ2 is 90°. In 1OCBF3 the barrier to rotation about the ring–O bond decreases substantially to being near zero. 相似文献