全文获取类型
收费全文 | 374篇 |
免费 | 26篇 |
出版年
2023年 | 3篇 |
2022年 | 6篇 |
2021年 | 7篇 |
2020年 | 13篇 |
2019年 | 15篇 |
2018年 | 14篇 |
2017年 | 14篇 |
2016年 | 23篇 |
2015年 | 21篇 |
2014年 | 30篇 |
2013年 | 22篇 |
2012年 | 28篇 |
2011年 | 15篇 |
2010年 | 22篇 |
2009年 | 19篇 |
2008年 | 23篇 |
2007年 | 16篇 |
2006年 | 16篇 |
2005年 | 16篇 |
2004年 | 14篇 |
2003年 | 6篇 |
2002年 | 11篇 |
2001年 | 3篇 |
2000年 | 6篇 |
1999年 | 7篇 |
1998年 | 7篇 |
1997年 | 4篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1994年 | 4篇 |
1993年 | 1篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1988年 | 2篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有400条查询结果,搜索用时 15 毫秒
101.
The continuous increase of human pressure on the environment and the concomitant pollution threat call for more complete and efficient environmental protection systems. Wastewater treatment plants are a technological response to the accumulation of pollution that occurs during the human-dominated phases of water cycle. In recent years, thanks to significant improvements in sewage treatment methodology, a number of upgrades have been assessed to improve the efficiency and functionality of treatment systems. Nonetheless, this activity requires large material and energy consumptions that have to be carefully accounted for when evaluating the efficiency of the process. In this work we present an emergy approach to the evaluation of a wastewater treatment plant located along the Ligurian coast (NW Mediterranean Sea). Besides the evaluation of the water treatment plant system, a preliminary assessment of the environmental costs in terms of natural fluxes required for the treatment process was performed. In fact, at the end of the treatment discharged water is still loaded with substances that have to be adsorbed by the receiving natural system. The work done by nature assimilating this load is generally considered as free while it is counted as a further cost in the total emergy budget of the water purification process. 相似文献
102.
Pereira AS DiLeone L Souza FH Lilla S Richter M Schwartsmann G De Nucci G 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》2005,816(1-2):321-326
Bombesin (BN) and its mammalian equivalent, gastrin-releasing peptide (GRP), stimulate cell proliferation and are involved in the pathogenesis of several types of human cancer. BN/GRP and their receptors were shown to be critical for the growth of various human malignancies, such as small-cell lung, prostate, ovary, stomach and breast cancers in the human tumor xenograft model. In the present study, a fast, sensitive, robust method was developed for the determination and quantification of a BN/GRP receptor antagonist RC-3095 (D-Tpi-Gln-Trp-Ala-Val-Gly-His-Leupsi(CH2NH)Leu-NH2), in human plasma by liquid chromatography coupled with tandem mass spectrometry. RC-3095 was extracted from 0.2 ml human plasma by protein precipitation using cold acetonitrile (0.4 ml). The method has a chromatographic run of 10 min using a C(8) analytical column (150 mm x 4.6 mm i.d.) and the linear calibration curve over the range was linear from 20 to 10000 ng ml(-1) (r(2)>0.994). The between-run precision, based on the relative standard deviation replicate quality controls, was 5.7% (60 ng ml(-1)), 7.1% (600 ng ml(-1)) and 6.8% (8000 ng ml(-1)). The between-run accuracy was +/-0.0, 2.1 and 3.1% for the above-mentioned concentrations, respectively. The developed procedure allows the quantitative determination of peptide RC-3095 for pharmacokinetics studies in human plasma. 相似文献
103.
The response of the microbial community (in term of abundance and enzymatic activity) was investigated to test the effect of different bioremediation protocols to naturally enhance decomposition of organic polymers in harbour sediments (Genoa Harbour, Italy, N–W Mediterranean). Bioremediation techniques tested were bioaugmentation (5 different microorganisms inocula), biostimulation (air supply), and natural attenuation. The coupling bioaugmentation/biostimulation was also tested. After 60days, following the bioaugmentation protocol, bacterial densities correlated to the quantities of inocula amended to the boxes, suggesting that allochthonous community was able to survive and multiply. However, while bioaugmentation alone seems not to be able to carry out significative degradation, its coupling with air insufflations produced the best response: here bacterial densities increased, especially in the water (from 2.3×107 to 3.50×108cells ml–1), average cell size and enzymatic activities increased, and sedimentary organic matter was significantly depleted (PRT 5-folds reduction, CHO 1.5-folds reduction). The strong coupling observed between the sediment and water compartments together with the greatest microbial response observed in this latter suggest that the sediment–water interface may constitute a key compartment for the occurring of biodegradation processes in organic-rich sediments. 相似文献
104.
Schneider Uwe Vasi Fabiano Schmidli Kevin Besserer Jürgen 《Radiation and environmental biophysics》2020,59(3):439-450
Radiation and Environmental Biophysics - A radiation action model based on nanodosimetry is presented. It is motivated by the finding that the biological effects of various types of ionizing... 相似文献
105.
Renato David Ghisolfi Meyre Pereira da Silva Felipe Thomaz dos Santos Ricardo Nogueira Servino Mauro Cirano Fabiano Lopes Thompson 《PloS one》2015,10(2)
The Abrolhos Bank is part of the so-called Eastern Brazilian Shelf and is an area of high ecological and economic importance. The bank supports the largest and richest coral reefs in the South Atlantic and the largest rhodolith bed in the world. The spatial and seasonal variation of phytoplankton concentration, however, and the dynamic processes controlling that variability have remained poorly known. The present study investigates the seasonal and spatial distributions of chlorophyll-a (Chl-a) and water conditions by analyzing nine years (2003–2011) of level-3 Moderate-resolution Imaging Spectroradiometer (MODIS) derived Chl-a, National Centers for Environmental Prediction (NCEP)/ETA model-derived winds, NCEP model-derived heat fluxes, thermohaline and velocity results from the Hybrid Circulation Ocean Model (HYCOM) 1/12o assimilated simulation. The results show that low/high concentrations occurred in austral spring-summer (wet season)/autumn-winter (dry season), with the highest values observed in the northern portion of the Abrolhos Bank. The typical meteorological and oceanographic conditions during austral summer favor the development of strong stratification. These conditions are 1) N-NE winds that favor an upwelling-type Ekman circulation; 2) coupling between the open ocean and the continental shelf through the western boundary current, which promotes cooler subsurface water to rise onto the shelf break; and 3) positive net heat flux. In contrast, the S-SE winds during autumn are in the opposite direction of the predominant current system over the Abrolhos Bank, thus reducing their speed and inducing an inverse shear. The warmer ocean and a somewhat cool and dry atmosphere promote the evaporative cooling of the surface layer. The above processes drive mixed layer cooling and deepening that reaches its maximum in winter. The blooming of phytoplankton in the Abrolhos Bank waters appears to be regulated by changes in the mixed layer depth, with Chl-a levels that start to increase during autumn and reach their peak in June-July. 相似文献
106.
107.
108.
Gizele D. Garcia Gustavo B. Gregoracci Eidy de O. Santos Pedro M. Meirelles Genivaldo G. Z. Silva Rob Edwards Tomoo Sawabe Kazuyoshi Gotoh Shota Nakamura Tetsuya Iida Rodrigo L. de Moura Fabiano L. Thompson 《Microbial ecology》2013,65(4):1076-1086
Coral health is under threat throughout the world due to regional and global stressors. White plague disease (WP) is one of the most important threats affecting the major reef builder of the Abrolhos Bank in Brazil, the endemic coral Mussismilia braziliensis. We performed a metagenomic analysis of healthy and WP-affected M. braziliensis in order to determine the types of microbes associated with this coral species. We also optimized a protocol for DNA extraction from coral tissues. Our taxonomic analysis revealed Proteobacteria, Bacteroidetes, Firmicutes, Cyanobacteria, and Actinomycetes as the main groups in all healthy and WP-affected corals. Vibrionales, members of the Cytophaga–Flavobacterium–Bacteroides complex, Rickettsiales, and Neisseriales were more abundant in the WP-affected corals. Diseased corals also had more eukaryotic metagenomic sequences identified as Alveolata and Apicomplexa. Our results suggest that WP disease in M. braziliensis is caused by a polymicrobial consortium. 相似文献
109.
Victor Camera Pimentel Daniela Zanini Andréia Machado Cardoso Roberta Schmatz Margarete Dulce Bagatini Jessié Martins Gutierres Fabiano Carvalho Jéssica Lopes Gomes Maribel Rubin Vera Maria Morsch Maria Beatriz Moretto Mariana Colino-Oliveira Ana Maria Sebastião Maria Rosa Chitolina Schetinger 《Neurochemical research》2013,38(4):886-894
It is well known that the levels of adenosine in the brain increase dramatically during cerebral hypoxic-ischemic (HI) insults. Its levels are tightly regulated by physiological and pathophysiological changes that occur during the injury acute phase. The aim of the present study was to examine the effects of the neonatal HI event on cytosolic and ecto-enzymes of purinergic system––NTPDase, 5′-nucleotidase (5′-NT) and adenosine deaminase (ADA)––in cerebral cortex of rats immediately post insult. Furthermore, the Na+/K+-ATPase activity, adenosine kinase (ADK) expression and thiobarbituric acid reactive species (TBARS) levels were assessed. Immediately after the HI event the cytosolic NTPDase and 5′-NT activities were increased in the cerebral cortex. In synaptosomes there was an increase in the ecto-ADA activity while the Na+/K+ ATPase activity presented a decrease. The difference between ATP, ADP, AMP and adenosine degradation in synaptosomal and cytosolic fractions could indicate that NTPDase, 5′-NT and ADA were differently affected after insult. Interestingly, no alterations in the ADK expression were observed. Furthermore, the Na+/K+-ATPase activity was correlated negatively with the cytosolic NTPDase activity and TBARS content. The increased hydrolysis of nucleotides ATP, ADP and AMP in the cytosol could contribute to increased adenosine levels, which could be related to a possible innate neuroprotective mechanism aiming at potentiating the ambient levels of adenosine. Together, these results may help the understanding of the mechanism by which adenosine is produced following neonatal HI injury, therefore highlighting putative therapeutical targets to minimize ischemic injury and enhance recovery. 相似文献
110.
Chayrra Chehade Fernanda G. Amaral Giovana S. Branco Mnica Cassel Lzaro W. O. De Jesus Fabiano G. Costa Silvana A. Bordin Renata G. Moreira Maria I. Borella 《Molecular reproduction and development》2020,87(6):720-734
Gonadotropin‐releasing hormone (GnRH) is a key molecule in the initiation of the hypothalamic–pituitary–gonadal axis. Thus, knowledge about GnRH may contribute to the effectiveness of species reproduction. Using a Neotropical tetra Astyanax altiparanae as a fish model species, the GnRH forms were characterized at the molecular level and the role of injected GnRHs in vivo was evaluated. The full‐length complementary DNA (cDNA) sequences of preproGnRH2 (612 bp) and preproGnRH3 (407 bp) of A. altiparanae were obtained, and the GnRH1 form was not detected. The cDNA sequences of preproGnRH2 and preproGnRH3 were found to be conserved, but a change in the amino acid at position 8 of the GnRH3 decapeptide of A. altiparanae was observed. All the injected GnRHs stimulated lhβ messenger RNA (mRNA) expression but not fshβ mRNA expression, and only GnRH2 was able to increase maturation‐inducing steroid (MIS) levels and possibly stimulate oocyte release. Furthermore, only GnRH2 was able to start the entire reproductive hormonal cascade and induce spawning. 相似文献