首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   184篇
  免费   5篇
  国内免费   2篇
  2023年   4篇
  2022年   6篇
  2021年   10篇
  2020年   4篇
  2019年   4篇
  2018年   4篇
  2017年   3篇
  2016年   4篇
  2015年   11篇
  2014年   12篇
  2013年   14篇
  2012年   8篇
  2011年   19篇
  2010年   2篇
  2009年   7篇
  2008年   10篇
  2007年   11篇
  2006年   3篇
  2005年   7篇
  2004年   4篇
  2003年   7篇
  2002年   8篇
  2001年   4篇
  2000年   7篇
  1998年   5篇
  1996年   2篇
  1995年   3篇
  1994年   1篇
  1991年   1篇
  1988年   1篇
  1984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191条查询结果,搜索用时 31 毫秒
71.
BackgroundSevere mental illness (SMI; schizophrenia, bipolar disorders (BDs), and other nonorganic psychoses) is associated with increased risk of cardiovascular disease (CVD) and CVD-related mortality. To date, no systematic review has investigated changes in population level CVD-related mortality over calendar time. It is unclear if this relationship has changed over time in higher-income countries with changing treatments.Methods and findingsTo address this gap, a systematic review was conducted, to assess the association between SMI and CVD including temporal change. Seven databases were searched (last: November 30, 2021) for cohort or case–control studies lasting ≥1 year, comparing frequency of CVD mortality or incidence in high-income countries between people with versus without SMI. No language restrictions were applied. Random effects meta-analyses were conducted to compute pooled hazard ratios (HRs) and rate ratios, pooled standardised mortality ratios (SMRs), pooled odds ratios (ORs), and pooled risk ratios (RRs) of CVD in those with versus without SMI. Temporal trends were explored by decade. Subgroup analyses by age, sex, setting, world region, and study quality (Newcastle–Ottawa scale (NOS) score) were conducted. The narrative synthesis included 108 studies, and the quantitative synthesis 59 mortality studies (with (≥1,841,356 cases and 29,321,409 controls) and 28 incidence studies (≥401,909 cases and 14,372,146 controls). The risk of CVD-related mortality for people with SMI was higher than controls across most comparisons, except for total CVD-related mortality for BD and cerebrovascular accident (CVA) for mixed SMI. Estimated risks were larger for schizophrenia than BD. Pooled results ranged from SMR = 1.55 (95% confidence interval (CI): 1.33 to 1.81, p < 0.001), for CVA in people with BD to HR/rate ratio = 2.40 (95% CI: 2.25 to 2.55, p < 0.001) for CVA in schizophrenia. For schizophrenia and BD, SMRs and pooled HRs/rate ratios for CHD and CVD mortality were larger in studies with outcomes occurring during the 1990s and 2000s than earlier decades (1980s: SMR = 1.14, 95% CI: 0.57 to 2.30, p = 0.71; 2000s: SMR = 2.59, 95% CI: 1.93 to 3.47, p < 0.001 for schizophrenia and CHD) and in studies including people with younger age. The incidence of CVA, CVD events, and heart failure in SMI was higher than controls. Estimated risks for schizophrenia ranged from HR/rate ratio 1.25 (95% CI: 1.04 to 1.51, p = 0.016) for total CVD events to rate ratio 3.82 (95% CI: 3.1 to 4.71, p < 0.001) for heart failure. Incidence of CHD was higher in BD versus controls. However, for schizophrenia, CHD was elevated in higher-quality studies only. The HR/rate ratios for CVA and CHD were larger in studies with outcomes occurring after the 1990s. Study limitations include the high risk of bias of some studies as they drew a comparison cohort from general population rates and the fact that it was difficult to exclude studies that had overlapping populations, although attempts were made to minimise this.ConclusionsIn this study, we found that SMI was associated with an approximate doubling in the rate ratio of CVD-related mortality, particularly since the 1990s, and in younger groups. SMI was also associated with increased incidence of CVA and CHD relative to control participants since the 1990s. More research is needed to clarify the association between SMI and CHD and ways to mitigate this risk.

Amanda Lambert and co-workers study associations between severe mental illness and cardiovascular disease outcomes over time.  相似文献   
72.
In the study, water, ethanol, methanol, dichloromethane, and acetone extracts of Asparagus officinalis L. were obtained by maceration. DPPH⋅, ABTS⋅+, FRAP, and CUPRAC methods determined the antioxidant capacities of all extracts. Moreover, the in vitro effects of extracts on acetylcholinesterase (AChE), butyrylcholinesterase (BChE), carbonic anhydrase (CA)-I, CA-II and α-Glycosidase were investigated. At a 10 μg/ml concentration, the extract with the highest Fe3+ reduction capacity was ethanol (AE), and the extract with the highest Cu2+ reduction capacity was acetone (AA). AE for AChE (IC50=21.19 μg/ml) and α-Glycosidase (IC50: 70.00 μg/ml), methanol (AM) for BChE (IC50=17.33 μg/ml), CA−I and II (IC50=79.65 and 36.09 μg/ml, respectively) showed the most potent inhibition effect. The content analysis of acetone extract was performed with LC/MS-MS, the first three phytochemicals found most were p-Coumaric acid, rutin, and 4-hydroxybenzoic acid (284.29±3.97, 135.39±8.19, and 102.06±5.51 μg analyte/g extract, respectively).  相似文献   
73.
In the present study, the volatile composition of Ulva rigida (U. rigida) was elucidated by two different methods. As a result of the identification process of volatile components using the GC/MS-FID instrument, 31 compounds were identified by hydrodistillation (HD) method, and 15 compounds were identified by solid-phase microextraction (SPME) method, elucidating the structure of 99.86 % and 92.65 %, respectively. The most abundant compounds in the essential oil of U. rigida were n-hexadecanoic acid and pentadecanal, while the most abundant compound according to the SPME analysis was heptadecyne, a hydrocarbon compound. In the next step, hexane, dichloromethane, chloroform and methanol solvent extracts of U. rigida were prepared and the antimicrobial activities of the extracts and the essential oil obtained by hydro-distillation as well as the scolicidal activities of the solvent extracts were determined. The results of the antimicrobial activity test of the essential oil showed a high level of activity against Bacillus cereus ATCC 10876 and MRSA. The highest activity was found on the microorganism of Pseudomonas aeruginosa ATCC 9027 in chloroform and methanol extracts of U. rigida. Furthermore, viability detection was performed and the scolicidal effects of the extracts on protoscoleces were assessed. The values of lethal concentration doses (LD50, LD75 and LD90) were calculated using probit analysis.  相似文献   
74.
During a slow desiccation in photosynthetically fully active leaves of the poikilochlorophyllous desiccation-tolerant (PDT) monocotyledon Xerophyta scabrida (Pax) Th. Dur. et Schinz (Velloziaceae), thylakoid activity, CO2 assimilation and respiration decline and chlorophylls and carotenoids are successively broken down. The initially slow rate of leaf water loss is related to the large reduction in leaf area which is reflected in the decrease of specific leaf area. Chlorophylls are broken down faster than carotenoids. The ratio of the variable chlorophyll fluorescence, an indicator of photosynthetic activity (Rfd690-values), shows that the functionality of thylakoids and chlorophylls is successively lost during desiccation. The decline in net CO2 assimilation in desiccating leaves is largely caused by stomatal closure. The complete cessation of CO2 assimilation, however, is due to the breakdown of chlorophylls and thylakoids. Respiration continued during desiccation and remained active far below -3.2 MPa leaf water potential. The differences during desiccation of the photosynthetic apparatus between poikilochlorophyllous and homoiochlorophyllous desiccation-tolerant plants are discussed.  相似文献   
75.
76.
The inhibitory effects of the cationic triarylmethane (TAM+) dyes, pararosaniline (PR+), malachite green (MG+), and methyl green (MeG+) on human plasma cholinesterase (BChE) were studied at 25 degrees C in 100 mM Mops, pH 8.0, with butyrylthiocholine as substrate. PR+ and MG+ caused linear mixed inhibition of enzyme activity. The respective inhibitory parameters were K(i) = 1.9 +/- 0.23 microM, alpha = 13 +/- 48, beta = 0 and K(i) = 0.28 +/- 0.037 microM, alpha = 23 +/- 7.4, beta = 0. MeG+ acted as a competitive inhibitor with K(i) = 0.12 +/- 0.017 microM (alpha, infinity, beta, not applicable). The K(i) values were within the same range reported for a number of ChE inhibitors including propidium ion, donepezil, and the phenothiazines, suggesting that TAM+s are active site ligands. On the other hand, the alpha values failed to correlate with values previously reported for a number of ChE inhibitors. It appears that mixed inhibition is the combined result of more than one type of binding and S-I interference. The impact of ligands at the choline-specific and peripheral anionic sites (or, possibly, accessory structural domains) on BChE activity needs to be studied in further detail.  相似文献   
77.
Szente  K.  Nagy  Z.  Tuba  Z. 《Photosynthetica》1998,35(4):637-640
Net CO2 assimilation rate (PN), stomatal conductance (gs), transpiration rate (E), and water use efficiency (WUE) in four perennial C3 species (grasses: Dactylis glomerata, Festuca rupicola, dicots: Filipendula vulgaris, Salvia nemorosa) grown for 231 d in open-top chambers at ambient (CA, 350 µmol mol-1) or elevated (CE, 700 µmol mol-1) CO2 concentrations were compared. When measured at CE, PN was significantly higher in CE plants of all four species than in the CA ones. The increase in PN was less prominent in the two grasses than in the two dicots. The E was significantly higher in the CE-grass F. rupicola and CE-dicot F. vulgaris than in the CA plants. There was no change in E owing to CE in the other grass and dicot. The gs in F. vulgaris and F. rupicola increased, while there was a decrease in D. glomerata and no change in S. nemorosa. WUE increased in all species grown in CE: four- to five-fold in the dicots and less than two-fold in the grasses. The increase in WUE was primarily due to an increase in PN and not to a decrease in E.  相似文献   
78.
79.

Background and Aims

The putative FASCICLIN-LIKE ARABINOGALACTAN PROTEIN 4 (At-FLA4) locus of Arabidopsis thaliana has previously been shown to be required for the normal growth of wild-type roots in response to moderately elevated salinity. However, the genetic and physiological pathway that connects At-FLA4 and normal root growth remains to be elucidated.

Methods

The radial swelling phenotype of At-fla4 was modulated with growth regulators and their inhibitors. The relationship of At-FLA4 to abscisic acid (ABA) signalling was analysed by probing marker gene expression and the observation of the At-fla4 phenotype in combination with ABA signalling mutants.

Key Results

Application of ABA suppresses the non-redundant role of At-FLA4 in the salt response. At-FLA4 positively regulates the response to low ABA concentration in roots and is required for the normal expression of ABA- and abiotic stress-induced genes. The At-fla4 phenotype is enhanced in the At-abi4 background, while two genetic suppressors of ABA-induced gene expression are required for salt oversensitivity of At-fla4. Salt oversensitivity in At-fla4 is suppressed by the CYP707A inhibitor abscinazole E2B, and salt oversensitivity in At-fla4 roots is phenocopied by chemical inhibition of ABA biosynthesis.

Conclusions

The predicted lipid-anchored glycoprotein At-FLA4 positively regulates cell wall biosynthesis and root growth by modulating ABA signalling.  相似文献   
80.
Sporopollenin is a natural polymer obtained from Lycopodium clavatum, which is highly stable with constant chemical structure and has high resistant capacity to chemical attack. In this study, immobilization of lipase from Candida rugosa (CRL) on sporopollenin by adsorption method is reported for the first time. Besides this, the enzyme adsorption capacity, activity and thermal stability of immobilized enzyme have also been investigated. It has been observed that under the optimum conditions (Spo-E(0.3)), the specific activity of the immobilized lipase on the sporopollenin by adsorption was 16.3 U/mg protein, which is 0.46 times less than that of the free lipase (35.6 U/mg protein). The pH and temperature of immobilized enzyme were optimized, which were 6.0 and 40 °C respectively. Kinetic parameters Vmax and Km were also determined for the immobilized lipase. It was observed that there is an increase of the Km value (7.54 mM) and a decrease of the Vmax value (145.0 U/mg-protein) comparing with that of the free lipase.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号