全文获取类型
收费全文 | 1080篇 |
免费 | 51篇 |
国内免费 | 2篇 |
出版年
2022年 | 7篇 |
2021年 | 22篇 |
2020年 | 18篇 |
2019年 | 16篇 |
2018年 | 33篇 |
2017年 | 27篇 |
2016年 | 43篇 |
2015年 | 56篇 |
2014年 | 65篇 |
2013年 | 70篇 |
2012年 | 84篇 |
2011年 | 111篇 |
2010年 | 49篇 |
2009年 | 42篇 |
2008年 | 73篇 |
2007年 | 78篇 |
2006年 | 95篇 |
2005年 | 43篇 |
2004年 | 64篇 |
2003年 | 57篇 |
2002年 | 37篇 |
2001年 | 3篇 |
2000年 | 2篇 |
1999年 | 8篇 |
1998年 | 7篇 |
1997年 | 6篇 |
1996年 | 4篇 |
1995年 | 5篇 |
1994年 | 2篇 |
1990年 | 1篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1982年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有1133条查询结果,搜索用时 140 毫秒
161.
Marta Michalczuk Beata Urban Tadeusz Porowski Anna Wasilewska Alina Bakunowicz-Łazarczyk 《Metabolomics : Official journal of the Metabolomic Society》2018,14(6):82
Introduction
Citrate is an old metabolite which is best known for the role in the Krebs cycle. Citrate is widely used in many branches of medicine. In ophthalmology citrate is considered as a therapeutic agent and an useful diagnostic tool—biomarker.Objectives
To summarize the published literature on citrate usage in the leading causes of blindness and highlight the new possibilities for this old metabolite.Methods
We conducted a systematic search of the scientific literature about citrate usage in ophthalmology up to January 2018. The reference lists of identified articles were searched for providing in-depth information.Results
This systematic review included 30 articles. The role of citrate in the leading causes of blindness is presented.Conclusions
Citrate might help inhibit cataract progression, in case of questions confirm glaucoma diagnosis or improve cornea repair treatment as adjuvant agent (therapy of ulcerating cornea after alkali injury, crosslinking procedure). However, the knowledge about possible citrate usage in ophthalmology is not widely known. Promoting recent scientific knowledge about citrate usage in ophthalmology may not only benefit of medical improvement but may also limit economic costs caused by leading causes of blindness. Further studies on citrate usage in ophthalmology should continuously be the field of scientific interest.162.
Purinergic P2X receptors, when activated under pathological conditions, participate in induction of the inflammatory response and/or cell death. Both neuroinflammation and neurodegeneration represent hallmarks of multiple sclerosis (MS), an autoimmune disease of the central nervous system. In the current study, we examined whether P2X7R is expressed in brain microvasculature of rats subjected to experimental autoimmune encephalomyelitis (EAE) and explore possible relationships with blood-brain barrier (BBB) protein—claudin-5 after administration of P2X7R antagonist—Brilliant Blue G (BBG). Capillary fraction isolated from control and EAE rat brains was subjected to immunohistochemical and Western blot analyses. We document the presence of P2X7R in brain capillaries isolated from brain tissue of EAE rats. P2X7R is found to be localized on the abluminal surface of the microvessels and is co-expressed with PDGFβR, a marker of pericytes. We also show over-expression of this receptor in isolated capillaries during the course of EAE, which is temporally correlated with a lower protein level of PDGFβR, as well as claudin-5, a tight junction-building protein. Administration of a P2X7R antagonist to the immunized rats significantly reduced clinical signs of EAE and enhances protein expression of both claudin-5 and PDGFβR. These results indicate that P2X7 receptor located on pericytes may contribute to pathological mechanisms operated during EAE in cerebral microvessels influencing the BBB integrity. 相似文献
163.
Yan Chen Sing-Yuen Sit Jie Chen Jacob J. Swidorski Zheng Liu Ny Sin Brian L. Venables Dawn D. Parker Beata Nowicka-Sans Zeyu Lin Zhufang Li Brian J. Terry Tricia Protack Sandhya Rahematpura Umesh Hanumegowda Susan Jenkins Mark Krystal Ira D. Dicker Alicia Regueiro-Ren 《Bioorganic & medicinal chemistry letters》2018,28(9):1550-1557
The design and synthesis of a series of C28 amine-based betulinic acid derivatives as HIV-1 maturation inhibitors is described. This series represents a continuation of efforts following on from previous studies of C-3 benzoic acid-substituted betulinic acid derivatives as HIV-1 maturation inhibitors (MIs) that were explored in the context of C-28 amide substituents. Compared to the C-28 amide series, the C-28 amine derivatives exhibited further improvements in HIV-1 inhibitory activity toward polymorphisms in the Gag polyprotein as well as improved activity in the presence of human serum. However, plasma exposure of basic amines following oral administration to rats was generally low, leading to a focus on moderating the basicity of the amine moiety distal from the triterpene core. The thiomorpholine dioxide (TMD) 20 emerged from this study as a compound with the optimal antiviral activity and an acceptable pharmacokinetic profile in the C-28 amine series. Compared to the C-28 amide 3, 20 offers a 2- to 4-fold improvement in potency towards the screening viruses, exhibits low shifts in the EC50 values toward the V370A and ΔV370 viruses in the presence of human serum or human serum albumin, and demonstrates improved potency towards the polymorphic T371A and V362I virus variants. 相似文献
164.
Adamus-Białek Wioletta Baraniak Anna Wawszczak Monika Głuszek Stanisław Gad Beata Wróbel Klaudia Bator Paulina Majchrzak Marta Parniewski Paweł 《Molecular biology reports》2018,45(5):1055-1065
Molecular Biology Reports - The spreading mechanisms of antibiotic resistance are related to many bacterial and environment factors. The overuse of antibiotics is leading to an unceasing emergence... 相似文献
165.
Densification of cyanobacteria from a lake leading to production of β‐cyclocitral and related volatile organic compounds and species change
下载免费PDF全文
![点击此处可从《Phycological Research》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Suzue Arii Kiyomi Tsuji Koji Tomita Masateru Hasegawa Ryuji Yamashita Beata Bober Ken‐Ichi Harada 《Phycological Research》2018,66(3):161-166
The purpose of the present study was to demonstrate that the lysis with the blue color formation was caused by densification of the cyanobacteria, and related events of the species change in the cyanobacteria were induced by the resulting volatile organic compounds (VOCs), particularly β‐cyclocitral. In order to obtain a high cell density of cyanobacteria in the laboratory, a concentration technique (graduated cylinder method) using the buoyancy of the gas vesicles was successfully used. The collected scum contained mainly Dolichospermum spp. and Microcystis, and the dispersed cyanobacteria were concentrated in the surface layer after several hours and the concentration ratio became approximately 10. The concentrated cyanobacteria were gradually lysed, while some of the cyanobacteria sank to the bottom, which finally died and disappeared. This method has the additional advantage that it is possible to visualize the entire lysis process. During the concentration process, β‐cyclocitral and its oxidation products together with β‐ionone were significantly detected. Because β‐cyclocitral was easily oxidized to the corresponding carboxylic acid, the pH of the water in the graduated cylinder decreased to approximately 6. Under favorable conditions, lysis with the blue color from phycocyanin could be observed due to the acid stress. Overall, the results of the present study were consistent with the hypothesis that VOCs were produced when the cyanobacteria are highly dense, and that the lysis with the blue color formation occurs due to the higher density. 相似文献
166.
Isolation of chlorophylls and carotenoids from freshwater algae using different extraction methods
下载免费PDF全文
![点击此处可从《Phycological Research》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Joanna Fabrowska Beata Messyasz Jakub Szyling Jędrzej Walkowiak Bogusława Łęska 《Phycological Research》2018,66(1):52-57
Usually marine algae are an excellent source of pigments for different commercial sectors. Freshwater macroalgae can be exploited as a good source of biologically active compounds provided an appropriate extraction method is developed. The efficiency of four methods, like microwave‐assisted (MAE), ultrasound‐assisted extraction (UAE), supercritical fluid extraction (SFE) with ethanol as a co‐solvent, as well as conventional Soxhlet extraction were studied in the same conditions (time, solvent and temperature) for the recovery of chlorophylls and carotenoids from three freshwater green algae species: Cladophora glomerata, Cladophora rivularis and Ulva flexuosa. UV‐Vis spectrophotometry was used to determine chlorophyll a, chlorophyll b and total carotenoid content in obtained extracts. The results of this study showed that the advantages of novel extraction techniques (MAE and UAE) include higher yield and, in consequence, lower costs compared to traditional solvent extraction techniques. These methods were much more efficient in freshwater green algae pigment recovery than the classic Soxhlet extraction as well as SFE. 相似文献
167.
Agnieszka Grinn-Gofroń Beata Bosiacka Aleksandra Bednarz Tomasz Wolski 《Aerobiologia》2018,34(1):45-54
Air sampling was conducted in Szczecin (Poland) throughout April–September 2013. The final data set included 177 daily and 4248 hourly samples. The total of 21 types of spores, which occurred in a number >10 in the season, were taken into account. The following meteorological parameters were analyzed: air temperature, relative humidity, precipitation and wind speed. Effects of individual weather parameters on hourly and daily concentrations of different fungal spore types were examined using Spearman’s rank association test, whereas effects of complex of meteorological factors on hourly and daily compositions of spore were assessed using detrended correspondence analysis (DCA) and redundancy analysis (RDA). Airborne fungal spore distribution patterns in relation to meteorological variables were determined by RDA, after DCA results detected a linear structure of the spore data. The RDA results obtained indicated that all the applied variables accounted for 20 and 22% of the total variance in the hourly and daily spore data, respectively. The results of stepwise forward selection of variables revealed all included hourly and daily meteorological variables were statistically significant. The largest amount of the total variance in the spore composition was explained by the air temperature in both cases (16%). Multivariate ordination did not show large differences between the hourly and daily relationships (with exception of wind speed impact), while the differences between simple hourly and daily correlations were more clear. Correlations between daily values of variables were in most cases higher than between hourly values of variables. 相似文献
168.
Mysliwa-Kurdziel Beata; Barthelemy Xavier; Strzalka Kazimierz; Franck Fabrice 《Plant & cell physiology》1997,38(11):1187-1196
The relationship between functional and structural aspects ofPSII formation during greening of etiolated barley leaves hasbeen investigated using fluorescence lifetime measurements,fluorescence kinetics analysis and analysis of chlorophyll-proteincomplexes by IEF-PAGE. Two phases of different character couldbe distinguished in the course of the greening process in dark-grownplants. An early phase covering the first 34 h afterthe onset of illumination and a late phase covering the subsequentgreening. During the first phase the formation of PSII reactioncenters and their minor antenna components was observed as manifestedby the IEF-PAGE polypeptide pattern. This was accompanied byshortening of the slow and middle components of the fluorescencelifetime, as well as by the rapid drop in the amplitude of theslow component. A room temperature emission band at 676 nm wasassociated with uncoupled chlorophyll and with the slow fluorescencelifetime component during the first hours of greening. Duringthe late greening phase peripheral light-harvesting complexesof PSII were formed concomitantly to an increase in lifetimeand amplitude of the fast component and to a further decreasein the lifetime of the middle component. The gradual increasein PSII complexity during both phases of greening was also manifestedby changes in proportion and kinetic properties of PSII 相似文献
169.
Audrey Arnal Beata Ujvari Leonard Nunney Eric Solary Lucie Laplane François Bonhomme Marion Vittecoq Aurélie Tasiemski François Renaud Pascal Pujol Benjamin Roche Frédéric Thomas 《Evolution; international journal of organic evolution》2016,70(1):1-6
Similar to seemingly maladaptive genes in general, the persistence of inherited cancer‐causing mutant alleles in populations remains a challenging question for evolutionary biologists. In addition to traditional explanations such as senescence or antagonistic pleiotropy, here we put forward a new hypothesis to explain the retention of oncogenic mutations. We propose that although natural defenses evolve to prevent neoplasm formation and progression thus increasing organismal fitness, they also conceal the effects of cancer‐causing mutant alleles on fitness and concomitantly protect inherited ones from purging by purifying selection. We also argue for the importance of the ecological contexts experienced by individuals and/or species. These contexts determine the locally predominant fitness‐reducing risks, and hence can aid the prediction of how natural selection will influence cancer outcomes. 相似文献