全文获取类型
收费全文 | 791篇 |
免费 | 59篇 |
专业分类
850篇 |
出版年
2023年 | 13篇 |
2022年 | 15篇 |
2021年 | 24篇 |
2020年 | 12篇 |
2019年 | 21篇 |
2018年 | 32篇 |
2017年 | 29篇 |
2016年 | 46篇 |
2015年 | 61篇 |
2014年 | 50篇 |
2013年 | 68篇 |
2012年 | 81篇 |
2011年 | 85篇 |
2010年 | 38篇 |
2009年 | 26篇 |
2008年 | 45篇 |
2007年 | 45篇 |
2006年 | 32篇 |
2005年 | 38篇 |
2004年 | 33篇 |
2003年 | 23篇 |
2002年 | 12篇 |
2000年 | 1篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 3篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1975年 | 4篇 |
1969年 | 1篇 |
排序方式: 共有850条查询结果,搜索用时 16 毫秒
841.
We describe how self-reported health (SRH) varies with gender and John Henryism (a strong behavioral predisposition to engage in high-effort coping to overcome adversity) in a low income sample of Serbian Roma. Data were collected in 2016 in several Roma settlements around Belgrade, Serbia. The sample consisted of 90 men and 112 women. In addition to John Henryism (JH), measured by a Serbian version of the John Henryism Scale, demographic data and data on SRH and family relationships dynamics were collected. SRH was positively correlated with age and JH, and negatively correlated with a history of chronic disease. Roma males and females differed significantly on JH and a number of other variables. For Roma women, multiple regression analyses revealed that a history of chronic disease, unemployment, age and daily stress level were negatively associated with SRH, while JH, SES and harmonious relationships with one’s family/children were positively associated with SRH. For Roma men, there was no association between JH and SRH, but older age, being on welfare, a diagnosis of hypertension and extended family disputes were associated with poorer SRH. Hence, despite economic disadvantage and social exclusion from mainstream society, some Roma report good health and the ability to cope actively with economic disadvantage and social exclusion. This study adds to the literature on the cross-cultural relevance of JH theory for understanding health variations within socially and economically marginalized populations. 相似文献
842.
Sanja Milovi Ivan Stankovi Dejan Nikoli Jelena Radovi Marina Kolundi Vesna Nikoli Tatjana Stanojkovi Slavica Petovi Tatjana Kundakovi‐Vasovi 《化学与生物多样性》2019,16(10)
Three seaweeds (Halimeda tuna, Codium bursa and Cystoseira barbata) and one seagrass (Cymodocea nodosa) were collected from the Coast of Montenegro, Gulf of Boka Kotorska and their chemical analysis was performed. In seagrass C. nodosa, three phenolic compounds were identified (diosmetin 7‐sulfate, caftaric and coutaric acid). The content of β‐glucan, fatty acids, sterols and micro‐ and macro‐elements were investigated among all samples. The highest content of β‐glucan was detected in C. nodosa seagrass (13.04±0.42 g/100 g). The highest polyunsaturated fatty acids (PUFAs) level was reported in C. barbata, the brown alga (7.157 mg/g), which also had the significant sterol content (fucosterol, 21.76±0.1 μg/g). Green algae, C. bursa and H. tuna, showed the highest level of sterols (β‐sitosterol, 95.21±0.16 μg/g and 73.90±0.08 μg/g, respectively). H. tuna had the highest content of calcium (Ca) in amount of 55125 μg/g. In C. bursa, C. barbata and C. nodosa, the Na/K ratio was low (0.43, 0.46 and 0.69, respectively). 相似文献
843.
Exposure of an organism to stress, results in oxidative stress and increased nitric oxide (NO) production in the brain. The role of the processes caused by chronic stress in the prefrontal cortex has not been fully investigated. Considering that chronic stress increases NO production by the enzyme nitric oxide synthase (NOS), we examined the cytosolic neuronal (nNOS) or inducible (iNOS) protein levels in the prefrontal cortex of rats exposed to 21 d of chronic social isolation stress, an animal model of depression, alone or in combination with 2 h of acute immobilization or cold (4 °C) stress (combined stress). Antioxidative status via cytosolic CuZnSOD and mitochondrial MnSOD activity, cytosolic redox status via reduced glutathione (GSH) concentration were determined. Furthermore, cytosolic inducible heat shock protein 70 (Hsp70i), cytosolic/nuclear distributions of NF-κB and serum corticosterone (CORT) were also investigated to elucidate the possible mechanism involved in the cellular NOS pathway. Our results showed that both acute stressors led to increases of CORT and nNOS protein while iNOS protein expression was unaffected. In contrast to the acute stress, chronic social isolation compromised hypothalamic–pituitary-adrenal axis functioning such that the normal stress response was impaired following subsequent acute stressors. Downregulated redox GSH status as well as decreased activity of CuZnSOD and MnSOD suggests the existence of oxidative stress which remained as such following combined stressors. Changes in redox-status associated with decreased Hsp70i protein expression enabled NF-κB translocation into the nucleus, causing increased cytosolic nNOS and iNOS protein expression. Results suggest that NOS signaling pathway plays a differential role between acute and chronic stress whereby state of oxidative/nitrosative stress after chronic social isolation is caused, at least in part, by NF-κB activation and increased iNOS protein expression. 相似文献
844.
Violeta M. Arsovski Bojan Đ. Božić Jelena M. Mirković Vesna D. Vitnik Željko J. Vitnik Slobodan D. Petrović Gordana S. Ušćumlić Dušan Ž. Mijin 《Journal of molecular modeling》2015,21(9):239
To complement a previous UV study, we present a quantitative evaluation of substituent effects on spectroscopic data (1H and 13C NMR chemical shifts as well as FT-IR absorption frequency) applied to N,N'-bisarylmalonamides, using simple and extended Hammett equations as well as the Swain-Lupton equation. Furthermore, the DFT CAM-B3LYP/6–311+G(d,p) method was applied to study the impact of different solvents on the geometry of the molecules and their spectral data. Additionally, experimental data are correlated with theoretical results; excellent linear dependence was obtained. The overall results presented in this paper show that N,N'-bisarylmalonamides are prominent candidates for model molecules. 相似文献
845.
Lipid peroxidation and antioxidant status in blood of patients with uterine myoma, endometrial polypus, hyperplastic and malignant endometrium 总被引:1,自引:0,他引:1
Oxidative stress is considered to be involved in pathogenesis of many disorders of the female genital tract. In this study, we explored the lipid peroxidation levels and antioxidant enzyme activities in women diagnosed with different forms of uterine diseases in order to evaluate the extent of oxidative stress in blood of such patients. Blood samples of healthy subjects and gynecological patients were collected and subjected to assays for superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase and lipid hydroperoxides. The results show that alterations of measured parameters vary with the enzyme type and diagnosis. However, both reduction in antioxidants and elevation of lipid peroxidation were observed in general. Lipid hydroperoxides level was negatively correlated to superoxide dismutase and glutathione peroxidase activities, as well as positively correlated to catalase activity. In addition, the lipid hydroperoxides/ glutathione peroxidase ratio was found to be increased, according to the type of uterine disease. The obtained results show that perturbation of antioxidant status is more pronounced in blood of patients with premalignant (hyperplastic) and malignant (adenocarcinoma) lesions, compared to those with benign uterine changes such as polypus and myoma. 相似文献
846.
847.
Conidia of a new pathotype of Bipolaris zeicola (Stout) Shoemaker, which causes Helminthosporium corn leaf spot (HCLS) on inbreds derived from B73, are morphologically atypical on potato dextrose agar (PDA). The average conidial length on PDA (31.9 μm) is half that on naturally infected leaf (65.2 μm). Conidiogenuous cells terminally and subterminally located on short conidiophores produce new conidia which behave as initial conidia, i.e. they immediately elongate or germinate. Sometimes, they appear in chains. Based on conidial morphology on leaf materials and on wheat straw agar (WSA), the investigated fungus was identified as B. zeicola. 相似文献
848.
Jelena Cvetkovic Ilka Haferkamp Regina Rode Isabel Keller Benjamin Pommerrenig Oliver Trentmann Jacqueline Altensell Michaela Fischer-Stettler Simona Eicke Samuel C Zeeman H Ekkehard Neuhaus 《Plant physiology》2021,186(1):315
Maltose, the major product of starch breakdown in Arabidopsis (Arabidopsis thaliana) leaves, exits the chloroplast via the maltose exporter1 MEX1. Consequently, mex1 loss-of-function plants exhibit substantial maltose accumulation, a starch-excess phenotype and a specific chlorotic phenotype during leaf development. Here, we investigated whether the introduction of an alternative metabolic route could suppress the marked developmental defects typical for mex1 loss-of-function mutants. To this end, we ectopically expressed in mex1 chloroplasts a functional maltase (MAL) from baker’s yeast (Saccharomyces cerevisiae, chloroplastidial MAL [cpMAL] mutants). Remarkably, the stromal MAL activity substantially alleviates most phenotypic peculiarities typical for mex1 plants. However, the cpMAL lines contained only slightly less maltose than parental mex1 plants and their starch levels were, surprisingly, even higher. These findings point to a threshold level of maltose responsible for the marked developmental defects in mex1. While growth and flowering time were only slightly retarded, cpMAL lines exhibited a substantially improved frost tolerance, when compared to wild-types. In summary, these results demonstrate the possibility to bypass the MEX1 transporter, allow us to differentiate between possible starch-excess and maltose-excess responses, and demonstrate that stromal maltose accumulation prevents frost defects. The latter insight may be instrumental for the development of crop plants with improved frost tolerance.Expressing a yeast maltase in chloroplasts of the Arabidopsis maltose transporter mutant mex1 prevents the marked developmental defects typical for that mutant and enhances plant frost tolerance. 相似文献
849.
Carolyn N. Brown Daniel Atwood Deepak Pokhrel Sara J. Holditch Christopher Altmann Nataliya I. Skrypnyk Jennifer Bourne Jelena Klawitter Judith Blaine Sarah Faubel Andrew Thorburn Charles L. Edelstein 《Cell death & disease》2021,12(3)
Many surgical models are used to study kidney and other diseases in mice, yet the effects of the surgical procedure itself on the kidney and other tissues have not been elucidated. In the present study, we found that both sham surgery and unilateral nephrectomy (UNX), which is used as a model of renal compensatory hypertrophy, in mice resulted in increased mammalian target of rapamycin complex 1/2 (mTORC1/2) in the remaining kidney. mTORC1 is known to regulate lysosomal biogenesis and autophagy. Genes associated with lysosomal biogenesis and function were decreased in sham surgery and UNX kidneys. In both sham surgery and UNX, there was suppressed autophagic flux in the kidney as indicated by the lack of an increase in LC3-II or autophagosomes seen on immunoblot, IF and EM after bafilomycin A1 administration and a concomitant increase in p62, a marker of autophagic cargo. There was a massive increase in pro-inflammatory cytokines, which are known to activate ERK1/2, in the serum after sham surgery and UNX. There was a large increase in ERK1/2 in sham surgery and UNX kidneys, which was blocked by the MEK1/2 inhibitor, trametinib. Trametinib also resulted in a significant decrease in p62. In summary, there was an intense systemic inflammatory response, an ERK-mediated increase in p62 and suppressed autophagic flux in the kidney after sham surgery and UNX. It is important that researchers are aware that changes in systemic pro-inflammatory cytokines, ERK1/2 and autophagy can be caused by sham surgery as well as the kidney injury/disease itself.Subject terms: Autophagy, Kidney 相似文献
850.