全文获取类型
收费全文 | 1080篇 |
免费 | 81篇 |
专业分类
1161篇 |
出版年
2023年 | 4篇 |
2022年 | 17篇 |
2021年 | 31篇 |
2020年 | 28篇 |
2019年 | 28篇 |
2018年 | 23篇 |
2017年 | 37篇 |
2016年 | 37篇 |
2015年 | 31篇 |
2014年 | 58篇 |
2013年 | 58篇 |
2012年 | 85篇 |
2011年 | 63篇 |
2010年 | 54篇 |
2009年 | 35篇 |
2008年 | 48篇 |
2007年 | 56篇 |
2006年 | 42篇 |
2005年 | 36篇 |
2004年 | 33篇 |
2003年 | 29篇 |
2002年 | 36篇 |
2001年 | 25篇 |
2000年 | 36篇 |
1999年 | 25篇 |
1998年 | 12篇 |
1997年 | 9篇 |
1996年 | 11篇 |
1995年 | 11篇 |
1994年 | 4篇 |
1993年 | 9篇 |
1992年 | 15篇 |
1991年 | 10篇 |
1990年 | 11篇 |
1989年 | 14篇 |
1988年 | 14篇 |
1987年 | 4篇 |
1986年 | 7篇 |
1985年 | 9篇 |
1981年 | 5篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1975年 | 4篇 |
1974年 | 3篇 |
1973年 | 7篇 |
1972年 | 5篇 |
1971年 | 7篇 |
1969年 | 4篇 |
1968年 | 6篇 |
1966年 | 4篇 |
排序方式: 共有1161条查询结果,搜索用时 0 毫秒
1.
Inhibitory effect of the flavonoid silymarin on the erythrocyte hemolysis induced by phenylhydrazine
A Valenzuela T Barría R Guerra A Garrido 《Biochemical and biophysical research communications》1985,126(2):712-718
The flavonoid silymarin, which is used as a therapeutical agent in the treatment of liver diseases, can inhibit the hemolysis and lipid peroxidation induced by phenylhydrazine on erythrocytes obtained from rats treated with the flavonoid. This effect is ascribed to the antioxidant properties as a free radical scavenger exhibited by the flavonoid. Silymarin failed to inhibit the glutathione depletion induced by phenylhydrazine on erythrocytes. It is proposed that the flavonoid acts at the membrane level of the cell avoiding the lipid peroxidative and fluidizing effect of phenylhydrazine. 相似文献
2.
To investigate the effects of the prostaglandin synthetase inhibitor, meclofenamate, on postnatal ventilation, we studied 11 unanaesthetised, spontaneously-breathing lambs at an average age of 7.9 +/- 1.1 days (SEM; range 5-14 days) and an average weight of 4.9 +/- 0.5 kg (range 3.0-7.0 kg). After a 30-min control period we infused 4.23 mg/kg meclofenamate over 10 min and then gave 0.23 mg/h per kg for the remainder of the 4 h. Ventilation increased progressively from a control value of 515 +/- 72 ml/min per kg to a maximum of 753 +/- 100 ml/min per kg after 3h of infusion (P less than 0.05) due to an increased breathing rate; the effects were similar during both high- and low-voltage electrocortical activity. There were no significant changes in tidal volume, heart rate, blood pressure, arterial pH or PaCO2, the increased ventilation resulted from either an increase in dead space ventilation or an increase in CO2 production. This study indicates that meclofenamate causes an increase in ventilation in lambs but no changes in pH of PaCO2. The mechanism and site of action remain to be defined. 相似文献
3.
Marcelo dos Santos Guerra Maria Tereza M. Nogueira 《Plant Systematics and Evolution》1990,170(3-4):229-236
Analysis of several populations in a large part of the distribution area of the genusEmilia in Brazil has revealed only two species: the diploidE. sonchifolia and the tetraploidE. fosbergii. The more widely reportedE. coccinea was not found. They show a karyotype constancy in morphology and chromosome number (2n = 10 and 2n = 20, respectively), C-banding pattern and number of secondary constrictions. Some indications were found thatE. fosbergii may be an allopolyploid and that its ancestors had different genome sizes. 相似文献
4.
Guerra F. A.; Savich R. D.; Wallen L. D.; Lee C. H.; Clyman R. I.; Mauray F. E.; Kitterman J. A. 《Journal of applied physiology》1988,64(5):2160-2166
To test the hypothesis that prostaglandin (PG) E2 is a respiratory depressant in the newborn lamb, 12 chronically catheterized, unanesthetized lambs (age 2-6 days) were infused with progressively increasing doses of PGE2 (0.1, 0.5, 1.0, and 5.0 micrograms.kg-1.min-1; 30 min for each dose) into the ascending aorta. PGE2 caused significant progressive decreases in ventilation (due to decreased tidal volume and breathing rate), heart rate, blood pressure, and percent of the time spent in low-voltage electrocortical activity (LVA). PGE2 also caused respiratory acidosis, hypoxemia, and increased frequency and duration of apneic events (greater than 3 s). During the infusion there was a dose-related increase in plasma concentration of PGE2. At 30 min postinfusion, all measured variables showed recovery, although arterial pH, CO2 tension, and plasma PGE2 remained significantly different from control values, and the percent time in LVA was even higher than during control. Infusion of the vehicle alone (n = 5) caused no significant changes in any of the measured variables. The results, taken in combination with previous fetal studies, indicate that PGE2 has marked inhibitory effects on breathing movements both before and after birth. 相似文献
5.
6.
7.
8.
Sandro Cavicchi Daniela Guerra Vanna Natali Cristina Pezzoli Gianfranco Giorgi 《Journal of evolutionary biology》1989,2(4):235-251
From a laboratory stock of Drosophila melanogaster (Oregon), reared for more than 20 years at 18° C, a new population was derived and maintained at 28° C for 8 years. The chromosomal and cytoplasmic contribution to genetic divergence between the two populations was estimated. Six body traits and reproductive fitness were taken into account. The third chromosome is responsible for the adaptive difference for temperature between the two lines. Temperature-selected genes which control body size are located on the second and third chromosomes, although the contribution of each chromosome depends on the environment in which the flies develop. The correlation between the chromosomal and cytoplasmic contributions to different traits and fitness, changes with temperature. At 28° C the correlation between fitness and each body trait is proportional to the response to selection exhibited by each of them, but this is not true at 18° C. Body size has, therefore, an adaptive significance in relation to temperature, which is expressed only in the environment where selection occurs. Cytoplasmic genes affect almost all characters to an extent similar to that of chromosomal genes. Inter-chromosomal and nucleo-cytoplasmic interactions are present and also change with temperature. In general, genes selected in a given environment produce greater phenotypic changes in that environment than in another. The population that experienced both temperatures is fitter in both environments, suggesting that the capacity to adapt to warm temperatures depends on genes other than those which are involved in the adaptation to cold. 相似文献
9.
Marcelo dos Santos Guerra 《Plant Systematics and Evolution》1989,168(1-2):83-86
Azima tetracantha has an asymmetrical karyotype with large chromosomes and a large amount of heterochromatin. The haploid number (n = 11) may represent the base number of the family. However, a possible secondary origin of this base number is also considered. 相似文献
10.
Rolando Campos Argelia Garrido Ricardo Guerra Alfonso Valenzuela 《Free radical research》1990,10(4):259-264
Reperfusion of rat kidney submitted to temporal ischaemia induces a decrease in glutathione content. Lipid peroxidation is not detected in kidney homogenates but microsomes obtained after periods of reperfusion longer than 60 minutes show increased malondialdehyde values correlated with high oxygen consumption and superoxide free radical generation. Microsomes obtained from kidneys submitted to 15 or 60 minutes of reperfusion are resistant to NADPH-induced lipid peroxidation but after 120 minutes of reperfusion an increased lipid peroxidative response is observed. Although the mechanism of the protection found in microsomes against the induction of oxidative stress in the first 60 minutes of reperfusion is unknown, it is postulated that this subcellular fraction plays an important role in the oxidative stress observed after longer periods of reperfusion. 相似文献