全文获取类型
收费全文 | 1074篇 |
免费 | 101篇 |
出版年
2023年 | 6篇 |
2022年 | 12篇 |
2021年 | 25篇 |
2020年 | 27篇 |
2019年 | 34篇 |
2018年 | 47篇 |
2017年 | 34篇 |
2016年 | 41篇 |
2015年 | 57篇 |
2014年 | 62篇 |
2013年 | 57篇 |
2012年 | 91篇 |
2011年 | 76篇 |
2010年 | 52篇 |
2009年 | 49篇 |
2008年 | 54篇 |
2007年 | 52篇 |
2006年 | 44篇 |
2005年 | 41篇 |
2004年 | 40篇 |
2003年 | 36篇 |
2002年 | 28篇 |
2001年 | 21篇 |
2000年 | 21篇 |
1999年 | 19篇 |
1998年 | 8篇 |
1997年 | 4篇 |
1996年 | 7篇 |
1995年 | 5篇 |
1994年 | 3篇 |
1993年 | 7篇 |
1992年 | 5篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1989年 | 5篇 |
1988年 | 8篇 |
1987年 | 4篇 |
1986年 | 12篇 |
1985年 | 7篇 |
1984年 | 8篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 5篇 |
1980年 | 8篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1977年 | 6篇 |
1975年 | 4篇 |
1973年 | 7篇 |
1972年 | 3篇 |
排序方式: 共有1175条查询结果,搜索用时 15 毫秒
91.
Nelo Eidy Zanchi Frederico Gerlinger-Romero Lucas Guimarães-Ferreira Mário Alves de Siqueira Filho Vitor Felitti Fabio Santos Lira Marília Seelaender Antonio Herbert LanchaJr. 《Amino acids》2011,40(4):1015-1025
Amino acids such as leucine and its metabolite α-ketoisocaproate (KIC), are returning to be the focus of studies, mainly because
of their anti-catabolic properties, through inhibition of muscle proteolysis and enhancement of protein synthesis. It is clear
that these effects may counteract catabolic conditions, as well as enhance skeletal muscle mass and strength in athletes.
Moreover, beta-hydroxy-beta-methylbutyrate (HMB) has been shown to produce an important effect in reducing muscle damage induced
by mechanical stimuli of skeletal muscle. This review aims to describe the general scientific evidence of KIC and HMB supplementation
clinical relevance, as well as their effects (e.g., increases in skeletal muscle mass and/or strength), associated with resistance
training or other sports. Moreover, the possible mechanisms of cell signaling regulation leading to increases and/or sparing
(during catabolic conditions) of skeletal muscle mass are discussed in detail based on the recent literature. 相似文献
92.
Use of experimental design to investigate biodiesel production by multiple-stage Ultra-Shear reactor
Da Silva Nde L Garnica JA Batistella CB Maciel MR Maciel Filho R 《Bioresource technology》2011,102(3):2672-2677
This work presents biodiesel production from soybean oil and bioethanol by multiple-stage Ultra-Shear reactor (USR). The experiments were carried out in the following conditions: reaction time from 6 to 12 min; catalyst concentration from 0.5% to 1.5% by weight of soybean oil; ethanol: soybean oil molar ratio from 6:1 to 10:1. The experimental design was used to investigate the influence of process variables on the conversion in biodiesel. The best ethyl ester conversion obtained was 99.26 wt.%, with ethanol:soybean oil molar ratio of 6:1, catalyst concentration of 1.35% and with 12 min of reaction time. 相似文献
93.
Analysis of the NAC transcription factor gene family in citrus reveals a novel member involved in multiple abiotic stress responses 总被引:1,自引:0,他引:1
94.
Carolina A. Lima José L. Lima Filho Benício B. Neto Attilio Converti Maria G. Carneiro da Cunha Ana L. F. Porto 《Biotechnology and Bioprocess Engineering》2011,16(3):549-560
A 24 full factorial design was used to identify the main effects and interactions of the initial medium pH, soybean flour concentration,
temperature and orbital agitation speed on extracellular collagenase production by Penicillium aurantiogriseum URM4622. The most significant variables for collagenase production were soybean flour concentration and initial medium pH
that had positive main effects, and temperature that had a negative one. Protein concentration in soybean flour revealed to
be a significant factor for the production of a collagenase serine proteinase. The most favorable production conditions were
found to be 0.75% soybean flour, pH 8.0, 200 rpm, and 28°C, which led to a collagenase activity of 164 U. The enzyme showed
an optimum activity at 37°C and pH 9.0, was stable over wide ranges of pH and temperature (6.0 ∼ 10.0 and 25 ∼ 45°C, respectively)
and was strongly inhibited by 10 mM phenylmethylsulphonylfluoride. The firstorder rate constants for collagenase inactivation
in the crude extract, calculated from semi-log plots of the residual activity versus time, were used in Arrhenius and Eyring
plots to estimate the main thermodynamic parameters of thermoinactivation (E*
d
= 107.4 kJ/mol and ΔH*
d
= 104.7 kJ/mol). The enzyme is probably an extracellular neutral serine collagenase effective on azocoll, gelatin and collagen
decomposition. 相似文献
95.
Marina O. S. Dias Marcelo Pereira da Cunha Rubens Maciel Filho Antonio Bonomi Charles D. F. Jesus Carlos E. V. Rossell 《Journal of industrial microbiology & biotechnology》2011,38(8):955-966
Sugarcane bagasse is used as a fuel in conventional bioethanol production, providing heat and power for the plant; therefore,
the amount of surplus bagasse available for use as raw material for second generation bioethanol production is related to
the energy consumption of the bioethanol production process. Pentoses and lignin, byproducts of the second generation bioethanol
production process, may be used as fuels, increasing the amount of surplus bagasse. In this work, simulations of the integrated
bioethanol production process from sugarcane, surplus bagasse and trash were carried out. Selected pre-treatment methods followed,
or not, by a delignification step were evaluated. The amount of lignocellulosic materials available for hydrolysis in each
configuration was calculated assuming that 50% of sugarcane trash is recovered from the field. An economic risk analysis was
carried out; the best results for the integrated first and second generation ethanol production process were obtained for
steam explosion pretreatment, high solids loading for hydrolysis and 24–48 h hydrolysis. The second generation ethanol production
process must be improved (e.g., decreasing required investment, improving yields and developing pentose fermentation to ethanol)
in order for the integrated process to be more economically competitive. 相似文献
96.
Sugarcane (Saccharum X officinarum): A Reference Study for the Regulation of Genetically Modified Cultivars in Brazil 总被引:1,自引:0,他引:1
Cheavegatti-Gianotto A de Abreu HM Arruda P Bespalhok Filho JC Burnquist WL Creste S di Ciero L Ferro JA de Oliveira Figueira AV de Sousa Filgueiras T Grossi-de-Sá MD Guzzo EC Hoffmann HP de Andrade Landell MG Macedo N Matsuoka S de Castro Reinach F Romano E da Silva WJ de Castro Silva Filho M César Ulian E 《Tropical plant biology》2011,4(1):62-89
Global interest in sugarcane has increased significantly in recent years due to its economic impact on sustainable energy production. Sugarcane breeding and better agronomic practices have contributed to a huge increase in sugarcane yield in the last 30?years. Additional increases in sugarcane yield are expected to result from the use of biotechnology tools in the near future. Genetically modified (GM) sugarcane that incorporates genes to increase resistance to biotic and abiotic stresses could play a major role in achieving this goal. However, to bring GM sugarcane to the market, it is necessary to follow a regulatory process that will evaluate the environmental and health impacts of this crop. The regulatory review process is usually accomplished through a comparison of the biology and composition of the GM cultivar and a non-GM counterpart. This review intends to provide information on non-GM sugarcane biology, genetics, breeding, agronomic management, processing, products and byproducts, as well as the current technologies used to develop GM sugarcane, with the aim of assisting regulators in the decision-making process regarding the commercial release of GM sugarcane cultivars. 相似文献
97.
98.
Arthur de Sá Ferreira José Barbosa Filho Marcio Nogueira de Souza 《Biomedical signal processing and control》2011,6(4):410-413
Post-occlusive reactive hyperemia is a noninvasive maneuver to assess microvascular reactivity related to the bioavailability and/or bioactivity of endothelial-derived factors. The inability to respond to endogenous vasodilator substances is mostly described by a low peak flow after an event associated with a peak flow. The aim of this study is to propose a model to describe post-occlusive responses observed in the pressure waveforms after occlusion release. Model variables were investigated in search of those representatives of the endothelial response to the ischemic process. Radial pressure pulse waveforms were acquired in the anterior region of the wrist, superficial to the radial artery, using a piezoelectric transducer acquired by a 12 bits acquisition board model at a sampling rate of 1.0 kHz to increase the temporal resolution. The occlusion maneuver was performed using an arm-cuff placed over the brachial artery. A time series of pulse pressure (PP) values, calculated from successive values of beat-to-beat systolic and diastolic pressures, was found to be a useful variable representing blood pressure signal in the model. This data time series of the pulse pressure presents reduced initial values compared with the baseline measurement, and an increasing value until a steady state behavior was sustained after approximately 60 s. This behavior for the pulse pressure series was described by a hyperbolic tangent model with parameters K (rate of change of PP), PP0 (first value of PP after cuff release), and ΔPP (change in PP). The model was applied to pulse pressure signals from normotensive and hypertensive subjects. The observed responses between groups suggest that PP0 and ΔPP are related to an endothelial response to the ischemic process and could be used as a clinical tool to assess endothelial function in hypertension. 相似文献
99.
F M da Cunha T S Fr?de G L Mendes A Malheiros V Cechinel Filho R A Yunes J B Calixto 《Life sciences》2001,70(2):159-169
This study evaluates further the anti-inflammatory and anti-allergic properties of polygodial, a sesquiterpene extracted from the barks plant Drymis winteri (Winteraceae). Polygodial (12.8-128.1 micromol/kg, i.p.) 30 min prior, inhibited significantly the mouse paw oedema induced by prostaglandin E2, bradykinin (BK) substance P (SP), dextran, platelet activating factor (PAF) or carrageenan. Polygodial also inhibited arachidonic acid-, capsaicin- and croton oil-induced ear oedema in mice. Polygodial (42.7 micromol/kg, i.p.), significantly inhibited both exudation and cell influx when assessed in the pleurisy induced by SP and histamine, and to a less extent the inflammatory response caused by carrageenan, PAF, BK and des-Arg9-BK. Finally, polygodial (4.2-42.7 micromol/kg, i.p.) produced dose-related inhibition of paw oedema induced by ovalbumin, protecting in a time-dependent manner the anaphylactic shock induced by endovenous administration of ovalbumin in animals which had been actively sensitised by this antigen. These and our previous results indicate that the major component present in the bark of the plant D. winteri, the sesquiterpene polygodial exerts an interesting anti-inflammatory and anti-allergic properties when assessed in rats and mice. 相似文献
100.
Morphological and oxidative alterations on Sertoli cells cytoskeleton due to retinol-induced reactive oxygen species 总被引:1,自引:0,他引:1
de Oliveira RB Klamt F Castro MA Polydoro M Zanotto Filho A Gelain DP Dal-Pizzol F Moreira JC 《Molecular and cellular biochemistry》2005,271(1-2):189-196
Retinol (vitamin A) is involved in several cellular processes, like cell division, differentiation, transformation and apoptosis. Although it has been shown that retinol is a limitant factor for all these processes, the precise mechanisms by which retinol acts are still unknown. In the present study we hypothesised that alterations in the cytoskeleton of Sertoli cells induced by retinol supplementation could indicate an adaptive maintenance of its functions, since it plays an important role in the transformation process that we observed. Previous results demonstrated that Sertoli cells treated with retinol showed an oxidative imbalance, that leads the cell to two phenotypes: apoptosis or transformation. Our group has identified characteristics of Sertoli cells transformed by retinol which results in normal cell functions modification. In the present study the actin filament fluorescence assay and the deformation coefficient showed a modification in the morphology induced by retinol. We also observed an oxidative alteration in isolated cytoskeleton proteins and did not show alterations when these proteins are analyzed by electrophoreses. Our results showed an increase in mitochondria superoxide production and a decrease in nitric oxide levels. All results were partially or completely reverted by co-treatment of the antioxidant Trolox®. These findings suggest that the cytoskeleton components suffer individual alterations in different levels and that these alterations generate a global phenotype modification and that these processes are probably ROS dependent. We believe that the results from this study indicate an adaptation of the cytoskeleton to oxidative imbalance since there was not a loss of its function. (Mol Cell Biochem 271: 189–196, 2005) 相似文献