全文获取类型
收费全文 | 599篇 |
免费 | 17篇 |
国内免费 | 2篇 |
出版年
2023年 | 10篇 |
2022年 | 6篇 |
2021年 | 18篇 |
2020年 | 9篇 |
2019年 | 19篇 |
2018年 | 20篇 |
2017年 | 11篇 |
2016年 | 30篇 |
2015年 | 32篇 |
2014年 | 25篇 |
2013年 | 34篇 |
2012年 | 36篇 |
2011年 | 53篇 |
2010年 | 23篇 |
2009年 | 17篇 |
2008年 | 35篇 |
2007年 | 33篇 |
2006年 | 29篇 |
2005年 | 36篇 |
2004年 | 32篇 |
2003年 | 24篇 |
2002年 | 20篇 |
2001年 | 14篇 |
2000年 | 16篇 |
1999年 | 4篇 |
1998年 | 8篇 |
1997年 | 5篇 |
1996年 | 2篇 |
1995年 | 5篇 |
1994年 | 1篇 |
1991年 | 1篇 |
1988年 | 1篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1976年 | 1篇 |
1970年 | 1篇 |
1957年 | 1篇 |
1955年 | 1篇 |
1943年 | 1篇 |
排序方式: 共有618条查询结果,搜索用时 31 毫秒
31.
ABA treatment increases both the desiccation tolerance of photosynthesis,and nonphotochemical quenching in the moss Atrichum undulatum 总被引:2,自引:0,他引:2
Pulse amplitude modulation fluorescence was used to investigate whether abscisic acid (ABA) pretreatment increases the desiccation tolerance of photosynthesis in the moss Atrichum undulatum. In unstressed plants, ABA pretreatment decreased the F
V/F
m ratio, largely as a result of an increase in F
o. This indicated a reduction in energy transfer between LHCII and PSII, possibly hardening the moss to subsequent stress by reducing the production of the reactive oxygen species near PSII. During desiccation, F
0, F
m, F
v/F
m, PSII, and NPQ and F
0 quenching declined in ABA-treated and nontreated mosses. However, during rehydration, F
0, F
m, F
v/F
m, and PSII recovered faster in ABA-treated plants, suggesting that ABA improved the tolerance of photosystem II to desiccation. NPQ increased upon rehydration in mosses from both treatments, but much more rapidly in ABA-treated plants; during the first hour of rehydration, NPQ was two-fold greater in plants treated with ABA. F
0quenching followed a similar pattern, indicating that ABA treatment stimulated zeaxanthin-based quenching. The implications of these results for the mechanisms of ABA-induced desiccation tolerance in A. undulatum are discussed. 相似文献
32.
Tuba Z Bardin CW Dancsi A Francsics-Czinege E Molnár C Csörgei J Falkay G Koide SS Kumar N Sundaram K Dukát-Abrók V Balogh G 《Steroids》2000,65(5):266-274
The progestational activity of second- and third-generation progestins in oral contraceptives were markedly increased by addition of an 18-methyl group. A new progestin, the 18-methyl analog of Nestorone, 16-methylene-17alpha-hydroxy-18-methyl-19-norpregn-4-ene-3,2 0-dione acetate (10), was synthesized. The relative binding affinity and biologic activity of 10 was compared with Nestorone, levonorgestrel, and progesterone using a binding assay for rat progesterone receptors, the Clauberg assay in the rabbit, and by assessing pregnancy maintenance in the rat. These studies, as summarized in Table 4, show that 10 is three to ten times more potent than Nestorone. The addition of the 18-methyl group to Nestorone markedly increased its potency as noted above, but is unlikely to change its rate of delivery from sustained release systems. 10 should be ideally suited for administration by implants or small skin patches. 相似文献
33.
Fulya Tekşen Bekir Sitki Şayli Ahmet Aydin Ahmet Sayal Aşkin Işimer 《Biological trace element research》1998,63(2):123-127
Down syndrome is the most common cause of mental retardation, affecting 1 in 700–800 liveborn infants. Although numerous biochemical
abnormalities accompanying the syndrome have not yet been completely clarified, the antioxidant defense system enzymes have
shown to be altered due to increased gene dosage on chromosome 21 and overproduction of superoxide dismutase (SOD-1 or Cu/Zn
SOD). The purpose of this study was to investigate the activities of SOD-1 and glutathione peroxidase (GSH-Px) enzymes and
the levels of their cofactors zinc (Zn), copper (Cu) and selenium (Se) in plasma of 20 Down syndrome patients.
In comparison with age and sex-matched controls (n=15), plasma GSH-Px, SOD, and Cu levels were significantly decreased in the patient group, but Zn and Se concentrations remained
unchanged.
This study was presented as a poster in 29th Annual Meeting of European Society of Human Genetics held in Genoa in May, 1997. 相似文献
34.
Fadime Atalay Fehmi Odabasoglu Mesut Halici Ahmet Cakir Elif Cadirci Ali Aslan Ozlem Aydin Berktas Cavit Kazaz 《化学与生物多样性》2015,12(11):1756-1767
Two lichen metabolites, rhizonaldehyde ( 1 ) and rhizonyl alcohol ( 2 ), were isolated from the acetone extract of Lobaria pulmonaria by chromatographic methods, and their chemical structures were determined by UV/VIS, IR, and 1D‐ and 2D‐NMR spectroscopic methods. The gastroprotective and in vivo antioxidant activities of extracts of L. pulmonaria and its metabolites, 1 and 2 , were investigated in indomethacin‐induced ulcer models in rats. The gastric lesions were significantly reduced by acetone, hexane, and CHCl3 extracts, with 75.3–41.5% inhibition. Rhizonyl alcohol ( 2 ) significantly reduced the gastric lesions with an inhibition rate of 84.6–42.8%, whereas rhizonaldehyde ( 1 ) significantly increased the gastric lesions. Antioxidant parameters and myeloperoxidase activities were also evaluated in the gastric tissues of the rats. Indomethacin caused oxidative stress, which resulted in lipid peroxidation in gastric tissues by decreasing the levels of the antioxidants as compared to healthy rat tissues. In contrast to indomethacin, all extracts and rhizonyl alcohol ( 2 ) caused a significant decrease in lipid peroxidation levels and an increase in antioxidant parameters, superoxide dismutase, glutathione peroxidase, and glutathione‐S‐transferase, and reduced glutathione in gastric tissues. The administration of rhizonyl alcohol ( 2 ) also resulted in a decrease in gastric myeloperoxidase activity increased by indomethacin. The gastroprotective effect of rhizonyl alcohol ( 2 ) can be attributed to its antioxidant properties and its suppressing effect on neutrophil infiltration into gastric tissues. 相似文献
35.
Melanie Brügger Thomas Dmoulins G. Tuba Barut Beatrice Zumkehr Blandina I. Oliveira Esteves Kemal Mehinagic Quentin Haas Aline Schgler Marie-Anne Rameix-Welti Jean-Franois Elouët Ueli Moehrlen Thomas M. Marti Ralph A. Schmid Artur Summerfield Horst Posthaus Nicolas Ruggli Sean R. R. Hall Marco P. Alves 《PLoS pathogens》2021,17(7)
36.
Cahide Gokkusu Makbule Aydin Elif Ozkok Feti Tulubas Ali Elitok Burak Pamukcu Berrin Umman 《Cytokine》2010,49(1):58-63
Interleukin-15 (IL-15) is a potent proinflammatory cytokine that is now considered a key component of atherosclerosis. Proinflammatory gene polymorphisms lead to variations in the production and level of the proteins. In light of these findings, we hypothesized that variations in the gene coding for IL-15 influence the risk of coronary heart disease (CHD) by modulating the IL-15 levels. To test this hypothesis, we examined 5 single nucleotide polymorphisms (SNPs) in IL-15 gene and IL-15 levels in 102 patients with acute coronary syndrome (ACS), 102 patients with chronic ischemic stable CHD and 162 healthy control subjects. This study is the first report showing the influences of IL-15 gene variants and IL-15 levels on CHD. The five single nucleotide polymorphisms (SNPs) within the IL-15 gene, G367A, C267T, A14035T, C13687A, and A10504G were carried out by polymerase chain reaction/restriction fragment length polymorphism (PCR/RFLP). Serum IL-15 levels were significantly higher in both acute and chronic patients than in controls. Genetic variants of IL-15 gene and IL-15 levels were associated with CHD. In conclusion, our study supports the hypothesis that genetic variation in IL-15 gene and IL-15 levels influence the risk of CHD. Further studies are needed to confirm our hypothesis. 相似文献
37.
S. Ercan F. Ertugrul Y. Aydin F. S. Akfirat S. Hasancebi K. Akan Z. Mert N. Bolat O. Yorgancilar A. Altinkut-Uncuoglu 《Biologia Plantarum》2010,54(4):691-696
Expressed sequenced tags containing simple sequence repeats (EST-SSRs) were used to identify molecular markers associated
with yellow rust resistance in wheat (Triticum aestivum L.). A cross between yellow rust resistant (PI178383) and susceptible (Harmankaya99) wheat genotypes was performed and respective
DNA pools from the resistant and susceptible F2 seedlings were constructed. 78 EST-SSR primers were used for bulked segregant analysis and one EST-SSR marker (Pk54), identified as 200 bp fragment, was present in the resistant parent and resistant F2 hybrids but not in the susceptible ones. 108 wheat genotypes differing in yellow rust resistance were screened with Pk54 and 68 % of the wheat genotypes, known to be yellow rust resistant, had the Pk54 marker, further suggesting that the presence of this marker correlates with yellow rust resistance. 相似文献
38.
The protective effects of melatonin, vitamin E, and selenium alone or in combination were tested against cadmium-induced oxidative
damage in rat testes. A total of 60 male rats were equally divided into five study groups, one of which acted as control receiving
subcutaneous injections of physiological saline. The remaining four groups were treated with subcutaneous injections of cadmium
chloride at a dose of 1 mg/kg weight. The first study group received no treatment. The second group was treated with a combination
of 60 mg/kg vitamin E and 1 mg/kg sodium selenite. Group 3 was treated with 10 mg/kg melatonin, and the fourth group received
a combination of vitamin E, sodium selenite, and melatonin at the doses mentioned above. After 1 month, the animals were killed,
and the testes were excised for histological inspection and determination of tissue malondialdehyde and the activity of superoxide
dismutase. The animals receiving no treatment showed significantly higher malondialdehyde levels and reduced activity of the
enzyme (p < 0.05). Treatment with antioxidants resulted in a significant reduction in malondialdehyde when compared to the nontreated
animals (p < 0.05) and an increase in the superoxide dismutase activity that was almost the same as the controls. The combination of
melatonin, vitamin E, and selenium appears to have the more profound effect against cadmium-induced testicular injury. 相似文献
39.
Gunes A Inal A Alpaslan M Eraslan F Bagci EG Cicek N 《Journal of plant physiology》2007,164(6):728-736
It has been proposed that salicylic acid (SA) acts as an endogenous signal molecule responsible for inducing abiotic stress tolerance in plants. The effect of varying salicylic acid (SA) supply (0, 0.1, 0.5 and 1.0mM) on growth, mineral uptake, membrane permeability, lipid peroxidation, H(2)O(2) concentration, UV-absorbing substances, chlorophyll and carotenoid concentrations of NaCl (40 mM) stressed maize (Zea mays L.) was investigated. Exogenously applied SA increased plant growth significantly both in saline and non-saline conditions. As a consequence of salinity stress, lipid peroxidation, measured in terms of malondialdehyde (MDA) content and membrane permeability was decreased by SA. UV-absorbing substances (UVAS) and H(2)O(2) concentration were increased by increasing levels of SA. SA also strongly inhibited Na(+) and Cl(-) accumulation, but stimulated N, Mg, Fe, Mn and Cu concentrations of salt stressed maize plants. These results suggest that SA could be used as a potential growth regulator to improve plant salinity stress resistance. 相似文献
40.
The effect of silicon (Si) on the growth, sodium (Na), chloride (Cl), boron (B) concentrations, lipid peroxidation (MDA), membrane permeability (MP), lypoxygenase activity (LOX), proline (PRO) and H(2)O(2) accumulation, and the activities of major antioxidant enzymes (superoxide dismutase, SOD; catalase, CAT and ascorbate peroxidase, APX) of barley grown in original sodic-B toxic soil were investigated. Si applied to the sodic-B toxic soil at 70, 140 and 280 mg kg(-1) levels significantly increased Si concentrations of the plants and counteracted the deleterious effects of sodicity (Na ions) and B on shoot growth. Membrane permeability and the concentrations of H(2)O(2) and MDA increased, while PRO concentration decreased in plants grown in sodic-B toxic soil without Si. LOX activity was increased by applied Si. Compared with control plants, the activities of SOD and CAT were decreased, but APX was increased by applied Si levels. 相似文献