全文获取类型
收费全文 | 1227篇 |
免费 | 32篇 |
国内免费 | 2篇 |
专业分类
化学 | 1006篇 |
晶体学 | 22篇 |
力学 | 4篇 |
数学 | 112篇 |
物理学 | 117篇 |
出版年
2023年 | 12篇 |
2022年 | 10篇 |
2021年 | 55篇 |
2020年 | 31篇 |
2019年 | 34篇 |
2018年 | 22篇 |
2017年 | 24篇 |
2016年 | 48篇 |
2015年 | 42篇 |
2014年 | 45篇 |
2013年 | 117篇 |
2012年 | 90篇 |
2011年 | 77篇 |
2010年 | 51篇 |
2009年 | 60篇 |
2008年 | 54篇 |
2007年 | 65篇 |
2006年 | 64篇 |
2005年 | 50篇 |
2004年 | 53篇 |
2003年 | 37篇 |
2002年 | 27篇 |
2001年 | 18篇 |
2000年 | 14篇 |
1999年 | 10篇 |
1998年 | 12篇 |
1997年 | 8篇 |
1996年 | 6篇 |
1995年 | 13篇 |
1994年 | 7篇 |
1993年 | 12篇 |
1992年 | 9篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1987年 | 6篇 |
1986年 | 9篇 |
1985年 | 9篇 |
1984年 | 3篇 |
1983年 | 8篇 |
1982年 | 4篇 |
1981年 | 5篇 |
1980年 | 8篇 |
1979年 | 2篇 |
1978年 | 4篇 |
1977年 | 2篇 |
1974年 | 3篇 |
1962年 | 2篇 |
1937年 | 1篇 |
排序方式: 共有1261条查询结果,搜索用时 140 毫秒
991.
Chat-Wilk Karolina Rudnik Ewa Włoch Grzegorz Osuch Piotr 《Journal of Solid State Electrochemistry》2022,26(8):1715-1731
Journal of Solid State Electrochemistry - The codeposition of zinc and nickel from slightly acidic chloride, sulfate, and chloride-sulfate solutions containing a gluconate complexing agent was... 相似文献
992.
The importance of electromigration techniques in molecular biology and medicine is increasing rapidly, especially in systematic studies on proteomes and metabolomes. Staphylococcus aureus and Escherichia coli are bacterial species most frequently encountered in human infections, and many serious illnesses can be observed in the hospital environment. In this contribution we proposed a CE method with different modification of internal capillary surface and with monolithic beds as a selective material for determination of bacteria in clinical samples. The electrophoretic separation depends on the differential mobility of bacteria in the capillary and selective interactions between bacterial cells and stationary phases (modified surface, monolithic beads). Proposed procedures could become an effective tool for diagnosis of certain diseases caused by S. aureus and E. coli as well as Proteus vulgaris. 相似文献
993.
The aquation of chromium(III)-isocinchomeronato and quinolinato complexes, mer-[Cr(icaH)3]0 and mer-[Cr(quinH)3]0 (where icaH− and quinH− are N,O-bonded isocinchomeronic and quinolinic acid anion, respectively) was studied in NaOH solutions. The process leads
to successive ligand liberation in the fully deprotonated species. The kinetics of the first ligand liberation were studied
spectrophotometrically in the visible region. A mechanism is proposed in which the rate of the chelate-ring opening at the
Cr–N bond is much faster than the rate of the Cr–O bond breaking. The rate-determining step is described by the rate law:
k
obs1 = k
OH(1) + k
O
Q
2 [OH−], where k
OH(1) and k
O are rate constants of the first ligand liberation from the hydroxo- and oxo-forms of the intermediate, respectively, and
Q
2 is an equilibrium constant between these two protolytic forms. The first pseudo-first-order rate constants (k
obs1) were calculated using SPECFIT software for an A → B → C reaction pattern. The results are compared with those determined
in acidic medium. Kinetics of the second and third ligand liberation were also studied and values of successive pseudo-first-order
rate constants (k
obs2, k
obs3) are [OH−] independent. Effect of chromium(III)-quinolinato and isocinchomeronato complexes on 3T3 fibroblast proliferation was evaluated.
Cytotoxicity of these complexes is low, suggesting they may be promising candidates as novel dietary supplements. 相似文献
994.
The chromium(III) complexes with a new potential chromium transporting ligand—2,5-pyridinedicarboxylic acid (isocinchomeronic
acid, icaH2):[Cr(icaH)3]0, [Cr(icaH)2 (H2O)2]+ and [Cr(icaH)(H2O)4]2+ (where icaH = N,O-bonded isocinchomeronic acid anion), have been obtained and characterized in solution. The [Cr(icaH)3]0 complex undergoes aquation in acidic media to the diaqua-product. Kinetics of this process was studied spectrophotometrically
in the 0.1–1.0 M HClO4 range, at I = 1.0 M. The first aquation stage, the chelate-ring opening at the Cr–N bond, is a much faster than the second one. The rate
laws are of the form: k
obs = k
1 + k
−1/Q
1[H+] and k
obs = k
2
Q
2[H+]/(1 + Q
2[H+]), where k
1 and k
2 are the rate constants for the chelate-ring opening and the ligand liberation, respectively, k
−1 is the rate constant of the chelate-ring closure, Q
1 and Q
2 are the protonation constants of the pyridine nitrogen and 5-carboxylate group in the one-end bonded intermediate, respectively.
The results are discussed in terms of potential pharmaceutical application of the complex. 相似文献
995.
Janik E Grudziński W Gruszecki WI Krupa Z 《Journal of photochemistry and photobiology. B, Biology》2008,90(1):47-52
Leaves of Secale cereale seedlings were exposed to high light illumination (1200micromolm(-2)s(-1)) and Cd ions at 5 or 50microM concentrations. Influence of these stress factors on violaxanthin cycle pigments content was analysed chromatographically. Chlorophyll a fluorescence induction was used to analyse response of PSII to stress conditions and contribution of light-harvesting complex (LHCII) in non-photochemical quenching of excitation energy. The Cd-induced all-trans violaxanthin isomerization was analysed by HPLC technique in acetonitrile:methanol:water (72:8:3, v/v) solvent mixture. Interestingly, in the control and Cd-treated leaves subjected to high light, photochemical utilization of absorbed energy increased. This indicates plant adaptation to high light stress. In control plants high light caused zeaxanthin formation, however, the presence of Cd in the nutrient solution resulted in reduction of the second step of violaxanthin de-epoxidation process and anteraxanthin accumulation. In this study we have also shown, that non-photochemical quenching can be independent of anteraxanthin and zeaxanthin content. The particular increase in the cis isomers fraction in Cd-treated leaves has been explained in terms of a direct metal-pigment interaction as confirmed by Cd-induced all-trans violaxanthin isomerization in organic solvent, leading to formation of 13-cis, 9-cis and 15-cis isomers. 相似文献
996.
Michal Swierczewski Dr. Fabrice Cousin Dr. Ewa Banach Dr. Arnulf Rosspeintner Dr. Latevi Max Lawson Daku Dr. Abolfazl Ziarati Dr. Rania Kazan Prof. Gunnar Jeschke Raymond Azoulay Dr. Lay-Theng Lee Prof. Thomas Bürgi 《Angewandte Chemie (International ed. in English)》2023,62(16):e202215746
A bidentate chiral dithiol (diBINAS) is utilised to bridge Au25 nanoclusters to form oligomers. Separation by size allows the isolation of fractions that are stable thanks to the bidentate nature of the linker. The structure of the products is elucidated by small-angle X-ray scattering and calculated using density functional theory. Additional structural details are studied by diffusion-ordered nuclear magnetic resonance spectroscopy, transmission electron microscopy and matrix-assisted laser desorption/ionization time of flight mass spectrometry. Significant changes in the optical properties are analysed by UV/Vis and fluorescence spectroscopies, with the latter demonstrating a strong emission enhancement. Furthermore, the emergent chiral characteristics are studied by circular dichroism. Due to the geometry constraints of the nanocluster assemblies, diBINAS can be regarded as a templating molecule, taking a step towards the directed self-assembly of metal clusters. 相似文献
997.
Dr. Rebecca Walker Dr. Damian Pociecha Dr. Miroslaw Salamonczyk Prof. John M. D. Storey Prof. Ewa Gorecka Prof. Corrie T. Imrie 《Chemphyschem》2023,24(6):e202300105
The front cover artwork is provided by Dr Rebecca Walker of the Liquid Crystals Group at the University of Aberdeen. The image is a cartoon depiction of the formation of the heliconical chiral twist-bend nematic phase (N*TB) from its constituent bent molecules. The presence of a single enantiomer of the chiral, lactate-based liquid crystal dimers biases the formation of helices with only one handedness, unlike in the conventional NTB phase, observed for achiral molecules, for which the left- and right-handed helices are doubly degenerate. Read the full text of the Research Article at 10.1002/cphc.202200807 . 相似文献
998.
Marek Konop Ewa Kodziska Joanna Borowiec Anna Katarzyna Laskowska Joanna Czuwara Piotr Konieczka Bartomiej Cielik Emilia Waraksa Lidia Rudnicka 《Electrophoresis》2019,40(11):1565-1572
The recent emergence of nanotechnology has provided a new therapeutic modality in case of silver nanoparticles. Dressings containing silver form the basis for the treatment of burns and wounds, either acute or chronic ones. The aim of the study was to examine silver release from the different wound dressings: commercially available (Atrauman Ag, Aquacel Ag) and experimental (FKDP‐AgNPs) using MEKC. In order to characterize prepared keratin based wound dressing before and after its modification with AgNPs, a compositional analysis was conducted using energy dispersive X‐ray spectroscopy. Nanosilver toxicity was evaluated with the 3‐(4,5‐dimethylthiazol‐2‐yl)‐5‐(3‐carboxymethoxyphenyl)‐2‐(4 sulfophenyl)‐2H‐tetrazolium test. Silver release from wound dressings was assessed using MEKC. The best separation was observed for MEKC in 20 mM borate buffer at pH 9 with 20 mM SDS addition. In vitro studies showed silver at higher concentration than 10 ppm exerted a toxic effect on fibroblasts isolated from diabetic mice versus. NIH/3T3 and BJ cell lines (p < 0.05). We observed silver was released more gradually from experimental FKDP‐AgNPs wound dressing, in compare to commercially available wound dressings. The fast and low‐cost method utilizing MEKC can be used in clinical practice to detect silver release from the wound dressings. 相似文献
999.
Dolatowska-Żebrowska Karolina Ostrowska-Ligęza Ewa Wirkowska-Wojdyła Magdalena Bryś Joanna Górska Agata 《Journal of Thermal Analysis and Calorimetry》2019,138(4):2769-2779
Journal of Thermal Analysis and Calorimetry - A relatively unexplored goat’s milk fat and goat’s milk chocolate were investigated to enhance thermal properties of both. Differential... 相似文献
1000.
Szymon Sip Natalia Rosiak Andrzej Miklaszewski Patrycja Talarska Ewa Dudziec Judyta Cielecka-Piontek 《Molecules (Basel, Switzerland)》2021,26(17)
The amorphous form of carvedilol phosphate (CVD) was obtained as a result of grinding. The identity of the obtained amorphous form was confirmed by powder X-ray diffraction (PXRD), different scanning calorimetry (DSC), and FT-IR spectroscopy. The process was optimized in order to obtain the appropriate efficiency and time. The crystalline form of CVD was used as the reference standard. Solid dispersions of crystalline and amorphous CVD forms with hydrophilic polymers (hydroxypropyl-β-cyclodextrin, Pluronic® F-127, and Soluplus®) were obtained. Their solubility at pH 1.2 and 6.8 was carried out, as well as their permeation through a model system of biological membranes suitable for the gastrointestinal tract (PAMPA-GIT) was established. The influence of selected polymers on CVD properties was defined for the amorphous form regarding the crystalline form of CVD. As a result of grinding (four milling cycles lasting 15 min with 5 min breaks), amorphous CVD was obtained. Its presence was confirmed by the “halo effect” on the diffraction patterns, the disappearance of the peak at 160.5 °C in the thermograms, and the changes in position/disappearance of many characteristic bands on the FT-IR spectra. As a result of changes in the CVD structure, its lower solubility at pH 1.2 and pH 6.8 was noted. While the amorphous dispersions of CVD, especially with Pluronic® F-127, achieved better solubility than combinations of crystalline forms with excipients. Using the PAMPA-GIT model, amorphous CVD was assessed as high permeable (Papp > 1 × 10−6 cm/s), similarly with its amorphous dispersions with excipients (hydroxypropyl-β-cyclodextrin, Pluronic® F-127, and Soluplus®), although in their cases, the values of apparent constants permeability were decreased. 相似文献