全文获取类型
收费全文 | 462篇 |
免费 | 16篇 |
国内免费 | 1篇 |
专业分类
479篇 |
出版年
2023年 | 7篇 |
2022年 | 2篇 |
2021年 | 10篇 |
2020年 | 8篇 |
2019年 | 16篇 |
2018年 | 18篇 |
2017年 | 11篇 |
2016年 | 28篇 |
2015年 | 23篇 |
2014年 | 17篇 |
2013年 | 25篇 |
2012年 | 31篇 |
2011年 | 39篇 |
2010年 | 23篇 |
2009年 | 12篇 |
2008年 | 27篇 |
2007年 | 24篇 |
2006年 | 28篇 |
2005年 | 31篇 |
2004年 | 29篇 |
2003年 | 19篇 |
2002年 | 12篇 |
2001年 | 11篇 |
2000年 | 9篇 |
1999年 | 4篇 |
1998年 | 3篇 |
1997年 | 5篇 |
1995年 | 3篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有479条查询结果,搜索用时 15 毫秒
51.
We investigated individual and combined effects of salinity, soil boron (B), silicon (Si) and salicylic acid (SA) on the activities
of major antioxidant enzymes (superoxide dismutase, SOD; catalase, CAT and ascorbate peroxidase, APX) and non-enzymatic antioxidants
(AA), proline, chlorophyll, anthocyanin, H2O2 concentration, stomatal resistance (SR), lipid peroxidation (MDA), membrane permeability (MP), and the uptake of sodium (Na),
chloride (Cl), boron and Si of spinach plants. In general, salinity significantly increased H2O2 and proline concentrations, antioxidant activity, membrane permeability, lipid peroxidation and SR of the spinach plants,
indicating that they were stressed, whereas application of B only increased proline concentration. However, plant fresh weights
did not decline with either treatment. The application of Si decreased H2O2 and increased the activity of SOD and CAT. The application of SA increased SOD activity. Neither SA nor Si had any effect
on the proline concentration, or MP. However, application of Si increased chlorophyll concentration and decreased lipid peroxidation
(MDA concentration). Si treatment had no effect on SR. The concentration of B in the tissues, which was strongly increased
by B treatment, was decreased by NaCl. As a result of salinity, concentrations of Na+ and Cl− ions were increased in the plant tissues, and application of Si slightly increased these concentrations. These results indicate
that exogenous Si application increases stress tolerance of spinach, a plant that is naturally reasonably resistant to combined
salinity and B toxicity, by the enhancement of antioxidant mechanisms that reduce membrane damage. Exogenous SA has a less
obvious effect, although the levels of salinity and boron stress applied were not sufficient in this experiment to reduce
plant fresh weight. 相似文献
52.
53.
The number of transgenic mouse lines expressing Cre in either type of pigment cells (melanocytes and retinal pigment epithelium, RPE) is limited, and the available lines do not always offer sufficient specificity. In this study, we addressed this issue and we report on the generation of a MART‐1::Cre BAC transgenic mouse line, in which the expression of Cre recombinase is controlled by regulatory elements of the pigment cell‐specific gene MART‐1 (mlana). When MART‐1::Cre BAC transgenic mice were bred with the ROSA26‐R reporter line, ß‐galactosidase expression was observed in RPE from E12.5 onwards, and in melanocyte precursors from E17.5, indicating that the MART‐1::Cre line provides Cre recombinase activity in pigment‐producing cells rather than in a particular lineage. In addition, breeding of this mouse line to mice carrying a conditional allele of RBP‐Jκ corroborated the reported phenotypes in both pigment cell lineages, inducing hair greying and microphthalmia. Our results thus suggest, that the MART‐1::Cre line may serve as a novel and useful tool for functional studies in melanocytes and the RPE.genesis 49:403–409, 2011. © 2011 Wiley‐Liss, Inc. 相似文献
54.
【目的】为研究土壤细菌对蔬菜灰霉病的生防价值, 从辽宁、山东等地区的蔬菜种植基地采集土壤样本56份, 分离、筛选出对灰霉病具有稳定拮抗作用的细菌9株。【方法】采用平板对峙培养法进行初筛、复筛, 用抑菌圈法测定其抑菌效果, 并进行离体果实试验验证其对蔬菜灰霉病的防治效果, 通过形态学特征、生理生化特征及16S rRNA基因序列分析研究其分类地位。【结果】细菌CNY-04对蔬菜灰霉病的拮抗能力最强且遗传稳定, 抑菌圈直径达到34 mm; 初步鉴定该菌株为格氏沙雷菌(Serratia grimesii), 尚未见该菌在生防上的报道; CNY-04液体菌剂对离体番茄果实灰霉病的防效为69.23%, 50%多菌灵防效为75.39%, 24 h时接种CNY-04处理的番茄发病率为40.0%, 而48 h时接种处理的发病率为51.1%。【结论】CNY-04是一株较为理想的拮抗菌, 丰富了生防资源。 相似文献
55.
A number of studies have reported that oxidant stress reduces the activity of isolated Na(+)-K(+) ATPase and Ca(2+) ATPase which are known to affect the cell membrane integrity. The aim of the study is to determine whether the administration of lisinopril is able to protect the membrane-bound enzyme levels in isolated guinea pig hearts and also ascertain whether or not a relationship exists between oxygen free radicals and membrane bound Na(+)-K(+) ATPase and Ca(2+) ATPase. Forty guinea pig hearts were studied in an isolated Krebs-Henseleit solution-perfused Langendorff cardiac model. In all groups cardioplegic arrest was achieved by administering St. Thomas' Hospital cardioplegic solution (STHCS). Group 1 (control, n=10) received only STHCS. Group 2 (n=10) were arrested with lisinopril (l micromol l(-1)) added STHCS. Group 3 (n=10) were pretreated with oral lisinopril (0.2 mg kg(-1) twice a day) for 10 days and then arrested with STHCS. Group 4 were also pretreated with oral lisinopril (0.2 mg kg(-1) twice a day for 10 days), arrested with STHCS and reperfused with lisinopril added to Krebs-Henseleit solution (l micromol l(-1)). Hearts were subjected to normothermic global ischaemia for 90 min and then reperfused at 37 degrees C. Pretreatment and addition of lisinopril in the reperfusion buffer improved the levels of membrane-bound enzymes. When the treated groups were compared with control hearts, the best results were achieved in group 4. The Na(+)-K(+) and Ca(2+) ATPase levels increased from 466.38+/-5.99 to 560.12+/-18.02 and 884.69+/-9.13 to 1287.71+/-13.01 nmolPi mg(-1) protein h(-1) respectively (p<0.05). These results suggest that lisinopril protects the cell membrane integrity and lessens free radical-induced oxidant stress. 相似文献
56.
Işcan M Ada AO Coban T Kapucuoğlu N Aydin A Isimer A 《Biological trace element research》2002,89(2):177-190
When male rats were given a single dose of cadmium (Cd) (3.58 mg CdCl2·H2O/kg, ip) 72 hr prior to sacrifice, the testicular 7-ethoxyresorufin O-deethylase (EROD) and glutathione S-transferase (GST) activities toward the substrates 1-chloro-2,4-dinitrobenzene (CDNB), 1,2-dichloro-4-nitrobenzene (DCNB),
ethacrynic acid (EAA), 1,2-epoxy-3-(p-nitrophenoxy)-propane (EPNP), and cumene hydroperoxide (CHPx) decreased significantly as compared to controls. Cd also inhibited
reduced glutathione (GSH) level while increasing the lipid peroxidation (LP) level significantly. When the animals were given
a single dose of nickel (Ni) (59.5 mg NiCl2·6H2O/kg, ip) 16 hr prior to sacrifice, significant decreases were observed in EROD and GST activities toward CDNB, EAA, EPNP,
and CHPx, and GSH level. No significant alterations were noted in DCNB GST activity and LP level by Ni. For the combined treatment,
rats received the single dose of Ni 56 hr after the single dose of Cd and were killed 16 hr later. In these animals, lesser
depressions were observed on EROD activity and LP level than those of Cd alone. The combination of metals significantly inhibited
GST activities and GSH level but not to a greater degree than noted by Cd or Ni alone. Plasma testosterone levels of Cd-,
Ni-, and combination-treated rats decreased significantly compared to controls. The strongest depression was achieved by Cd
alone. Cd, both alone and in combination with Ni, increased the tissue Ni uptake significantly. Ni, however, did not produce
such an effect on the tissue uptake of Cd in either case. Cd treatment caused interstitial edema and coagulation necrosis
in seminiferous tubules and also caused fibrinoidal necrosis in vascular endothelium. Ni treatment did not produce any pathological
testicular alterations compared to controls. Combined treatment produced fewer pathological alterations (i.e., only interstitial
edema) than that of Cd treatment. These results reveal that the combination of Cd and Ni does not have a synergistic effect
on testicular xenobiotic metabolizing enzymes, and in contrast, Ni has an ameliorating effect on pathological disturbances
caused by Cd alone in the rat testis. 相似文献
57.
Malavasi F Deaglio S Ferrero E Funaro A Sancho J Ausiello CM Ortolan E Vaisitti T Zubiaur M Fedele G Aydin S Tibaldi EV Durelli I Lusso R Cozno F Horenstein AL 《Molecular medicine (Cambridge, Mass.)》2006,12(11-12):334-341
This paper reviews some of the results and the speculations presented at the Torino CD38 Meeting in June, 2006 and focused on CD38 and CD157 seen as a family of molecules acting as surface receptors of immune cells. This partisan view was adopted in the attempt to combine the enzymatic functions with what the immunologists consider key functions in different cell models. At the moment, it is unclear whether the two functions are correlated, indifferent, or independent. Here we present conclusions inferred exclusively on human cell models, namely T and B lymphocytes, dendritic cells, and granulocytes. As an extra analytical tool, we try to follow in the history of life when the enzymatic and receptorial functions were generated, mixing ontogeny, membrane localization, and cell anchorage. 相似文献
58.
This study aimed to examine the effects of CPB on salusin-α, salusin-β and apelin-36 bioactive peptides in people who are planned to undergo coronary artery bypass graft (CABG) operation due to coronary artery disease and to explore whether these peptides are produced in human aortic, saphenous and arterial tissues. The study included age and BMI matched 15 patients who underwent CABG operation by CPB. In order to determine salusin-α, salusin-β and apelin-36 levels, venous blood samples were collected before induction of anesthesia (T1), before CPB (T2), 5min before the removal of cross-clamp (T3), 5min after the removal of cross-clamp (T4), upon arrival in the intensive care (T5), at postoperative 24th hour (T6) and 72nd hour (T7). Salusin and apelin expressions of the tissues were shown by immunohistochemical method. Peptide amounts of sera and tissues were measured using ELISA. Salusins production by vessels occurs in fibroblast cells of the media in the aorta and smooth muscle cells of the media in the LIMA and saphena. Apelin is produced by endothelial cells of the intima and fibroblast cells of the media in the aorta and by smooth muscle cells of the media in the LIMA and saphena. Changes in the levels of salusin-β and apelin-36 were significant during CPB. Salusin-α, salusin-β and apelin-36 are locally synthesized in the arteries and veins. Salusins and apelin-36 might be important markers in the CPB, and also that salusin-β was more specific in comparison to salusin-α. 相似文献
59.
Impairment of thyroid functions brings about pathological changes in different organs of body. Findings of in vivo and in vitro studies indicate that thyroid hormones have a considerable impact on oxidative stress. Melatonin reduces oxidative damage through its free radical eliminating and direct anti-oxidant effects. The present study was undertaken to determine how a 3-week period of intraperitoneal melatonin administration affected oxidative damage caused in experimental hyperthyroidism in rat. The experimental animals were divided into 3 groups (control, hyperthyroidism, hyperthyroidism+melatonin). Malondialdehyde (MDA) and glutathione (GSH) levels were determined in different tissues. MDA levels in cerebral, liver and cardiac tissues in hyperthyroidism group were significantly higher than those in control and hyperthyroidism+melatonin supplemented groups (p<0.001). The highest GSH levels were observed in the group that was administered melatonin in addition to having hyperthyroidism (p<0.001). These results show that hyperthyroidism increased oxidative damage in cerebral, hepatic and cardiac tissues of rat. Melatonin supplementation may also suppress oxidative damage. 相似文献
60.
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