全文获取类型
收费全文 | 487篇 |
免费 | 16篇 |
专业分类
503篇 |
出版年
2023年 | 8篇 |
2022年 | 5篇 |
2021年 | 11篇 |
2020年 | 9篇 |
2019年 | 16篇 |
2018年 | 19篇 |
2017年 | 11篇 |
2016年 | 30篇 |
2015年 | 24篇 |
2014年 | 19篇 |
2013年 | 25篇 |
2012年 | 33篇 |
2011年 | 40篇 |
2010年 | 25篇 |
2009年 | 13篇 |
2008年 | 27篇 |
2007年 | 24篇 |
2006年 | 28篇 |
2005年 | 35篇 |
2004年 | 29篇 |
2003年 | 20篇 |
2002年 | 12篇 |
2001年 | 11篇 |
2000年 | 9篇 |
1999年 | 4篇 |
1998年 | 4篇 |
1997年 | 5篇 |
1995年 | 2篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1976年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有503条查询结果,搜索用时 15 毫秒
71.
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
72.
73.
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
74.
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
75.
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
76.
77.
Insecticidal Metabolites from the Rhizomes of Veratrum album against Adults of Colorado Potato Beetle,Leptinotarsa decemlineata 下载免费PDF全文
Tuba Aydin Ahmet Cakir Cavit Kazaz Neslihan Bayrak Yasin Bayir Yavuz Taşkesenligil 《化学与生物多样性》2014,11(8):1192-1204
The dried rhizomes of Veratrum album were individually extracted with CHCl3, acetone, and NH4OH/benzene to test the toxic effects against the Colorado potato beetle, Leptinotarsa decemlineata, which is an important agricultural pest. Fifteen compounds in various amounts were isolated from the extracts using column and thin‐layer chromatography. The chemical structures of 14 compounds were characterized as octacosan‐1‐ol ( 1 ), β‐sitosterol ( 2 ), stearic acid ( 3 ), diosgenin ( 4 ), resveratrol ( 5 ), wittifuran X ( 6 ), oxyresveratrol ( 7 ), β‐sitosterol 3‐O‐β‐D ‐glucopyranoside ( 8 ), diosgenin 3‐O‐α‐L ‐rhamnopyranosyl‐(1→2)‐β‐D ‐glucopyronoside ( 9 ), oxyresveratrol 3‐O‐β‐D ‐glucopyranoside ( 10 ), jervine ( 11 ), pseudojervine ( 13 ), 5,6‐dihydro‐1‐hydroxyjervine ( 14 ), and saccharose ( 15 ) using UV, IR, MS, 1H‐ and 13C‐NMR, and 2D‐NMR spectroscopic methods. However, the chemical structure of 12 , an oligosaccharide, has not fully been elucidated. Compounds 4, 6, 9 , and 10 were isolated from V. album rhizomes for the first time in the current study. The toxic effects of three extracts (acetone, CHCl3, and NH4OH/benzene) and six metabolites, 2, 2 + 4, 5, 7, 8 , and 11 , were evaluated against the Colorado potato beetle. The assay revealed that all three extracts, and compounds 7, 8 , and 11 exhibited potent toxic effects against this pest. This is the first report on the evaluation of the toxic effects of the extracts and secondary metabolites of V. album rhizomes against L. decemlineata. Based on these results, it can be concluded that the extracts can be used as natural insecticides. 相似文献
78.
Demir R Acar G Tanriover G Seval Y Kayisli UA Agar A 《Folia histochemica et cytobiologica / Polish Academy of Sciences, Polish Histochemical and Cytochemical Society》2005,43(3):143-150
The aim of this study was to investigate whether excess of vitamin B6 leads to ultrastructural changes in cerebral cortex of forty-eight healthy albino rats which were included in the study. Saline solution was injected to to the control groups (CG-10, n = 12 for 10 days; CG-15, n = 12 for 15 days; CG-20, n=12 for 20 days). The three experimental groups (EG-10, n = 12; EG-15, n = 12; EG-20, n = 12) were treated with 5 mg/kg vitamin B6 daily for 10 days (EG-10), 15 days (EG-15) and 20 days (EG-20). Brain tissues were prepared by glutaraldehyde-osmium tetroxide double fixation for ultrastructural analysis. No significant changes were observed in the control groups. The ultrastructural analysis revealed that the numbers of damaged mitochondria, lipofuscin granules and vacuoles were significantly higher in all the experimental groups than in the control groups (p < 0.05). However, synaptic density was significantly decreased in the experimental groups as compared to the control groups (p < 0.05). The results suggest that the excess of vitamin B6 intake causes damage to the cerebral cortex due to cellular intoxication and decreased synaptic density. Thus, careful attention should be paid to the time and dose of vitamin B6 recommended for patients who are supplemented with this vitamin. 相似文献
79.
Neurochemical Research - Ferulago angulata (Apiaceae) is a shrub indigenous to western Iran, Turkey and Iraq. In traditional medicine, F. angulata is recommended for treating digestive pains,... 相似文献
80.
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