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   676篇
  免费   32篇
  国内免费   4篇
  2023年   16篇
  2022年   22篇
  2021年   51篇
  2020年   31篇
  2019年   40篇
  2018年   37篇
  2017年   17篇
  2016年   35篇
  2015年   31篇
  2014年   46篇
  2013年   68篇
  2012年   53篇
  2011年   44篇
  2010年   28篇
  2009年   10篇
  2008年   24篇
  2007年   22篇
  2006年   18篇
  2005年   12篇
  2004年   19篇
  2003年   11篇
  2002年   17篇
  2001年   11篇
  2000年   6篇
  1999年   8篇
  1998年   3篇
  1997年   6篇
  1996年   3篇
  1995年   3篇
  1994年   4篇
  1993年   1篇
  1992年   5篇
  1991年   2篇
  1985年   1篇
  1984年   1篇
  1983年   1篇
  1981年   1篇
  1979年   1篇
  1976年   1篇
  1973年   1篇
  1872年   1篇
排序方式: 共有712条查询结果,搜索用时 15 毫秒
31.
Helophytic plants contribute significantly in phytoremediation of a variety of pollutants due to their physiological or biochemical mechanisms. Phenol, which is reported to have negative/deleterious effects on plant metabolism at concentrations higher than 500 mg/L, remains hard to be removed from the environmental compartments using conventional phytoremediation procedures. The present study aims to investigate the feasibility of using P. australis (a helophytic grass) in combination with three bacterial strains namely Acinetobacter lwofii ACRH76, Bacillus cereus LORH97, and Pseudomonas sp. LCRH90, in a floating treatment wetland (FTW) for the removal of phenol from contaminated water. The strains were screened based on their phenol degrading and plant growth promoting activities. We found that inoculated bacteria were able to colonize in the roots and shoots of P. australis, suggesting their potential role in the successful removal of phenol from the contaminated water. Pseudomonas sp. LCRH90 dominated the bacterial community structure followed by A. lowfii ACRH76 and B. cereus LORH97. The removal rate was significantly high when compared with the individual partners, i.e., plants and bacteria separately. The plant biomass, which was drastically reduced in the presence of phenol, recovered significantly with the inoculation of bacterial consortia. Likewise, highest reduction in chemical oxygen demand (COD), biochemical oxygen demand (BOD), and total organic carbon (TOC) is achieved when both plants and bacteria were employed. The study, therefore, suggests that P. australis in combination with efficient bacteria can be a suitable choice to FTWs for phenol-degradation in water.  相似文献   
32.
In searchof the potenttherapeutic agent as an α-glucosidase inhibitor, we have synthesized twenty-five analogs (125) of quinoline-based Schiff bases as an inhibitoragainst α-glucosidase enzyme under positive control acarbose (IC50 = 38.45 ± 0.80 µM). From the activity profile it was foundthat analogs 1, 2, 3, 4, 11, 12 and 20with IC50values 12.40 ± 0.40, 9.40 ± 0.30, 14.10 ± 0.40, 6.20 ± 0.30, 14.40 ± 0.40, 7.40 ± 0.20 and 13.20 ± 0.40 µMrespectively showed most potent inhibition among the series even than standard drug acarbose (IC50 = 38.45 ± 0.80 µM). Here in the present study analog 4 (IC50 = 6.20 ± 0.30 µM) was found with many folds better α-glucosidase inhibitory activity than the reference drug. Eight analogs like 5, 7, 8, 16, 17, 22, 24 and 25 among the whole series displayed less than 50% inhibition. The substituents effects on phenyl ring thereby superficially established through SAR study. Binding interactions of analogs and the active site of ligands proteins were confirmed through molecular docking study. Spectroscopic techniques like 1H NMR, 13C NMR and ESIMS were used for characterization.  相似文献   
33.
Abstract

The ingestion of 226Ra, inhalation, and ingestion of 222Rn in water is considered the primary health risk for lungs and stomach. This study presents the concentrations of 226Ra and 222Rn in well and tap water collected from Sik, Malaysia, using HPGe and RAD7 detectors. Maximum average concentrations of 226Ra and 222Rn were found 47.6?±?3.6 mBq/l and 9.3?±?1.4?Bq/l in well water, respectively, and minimum were found 17.1?±?3.6 mBq/l and 1.6?±?1.0?Bq/l in tap water, respectively. A positive correlation (R=.88) was found between 226Ra and 222Rn determined by HPGe and RAD7 detectors, respectively. Infants in the age group of 0–1 y appeared to be at risk with respect to the annual effective doses from 226Ra and 222Rn as compared to the other age groups. However, annual effective doses for all three age groups from intake of 226Ra and 222Rn in well and tap drinking water were found below the World Health Organization (WHO) recommended level of .1 mSv/y.  相似文献   
34.

Surface plasmon polariton (SPP) waves are the most extensively studied waves among various types of surface waves because they are easy to excite and have been used in many optical applications particularly for plasmonic communication, sensing, and harvesting solar energy. In all these applications, especially on-chip plasmonic communication, scattering can be an important issue to deal with. Therefore, this paper aimed to theoretically inspect the scattering pattern of SPP waves from a perfect electric conductor (PEC) cylindrical scatterer. The cylindrical wave approach is used to solve the scattering problem by a cylindrical object placed below a metallic layer. The scattering is investigated thoroughly by changing the size of the scatterer and its distance from the interface along which the SPP wave is excited. As the size of the scatterer increases, the scattering increases significantly. On the other hand, when the distance of the scatterer from the interface is increased, the scattered field becomes small. Two-dimensional field maps are produced for the incident angle at which SPP is excited. Numerical results are also presented for other incident angles to make a comparison. Furthermore, the forward and backward far-fields are significantly enhanced if the SPP wave is scattered in comparison with when the SPP wave is not present.

  相似文献   
35.
Phytochemistry Reviews - The production of safe foods with little or no artificial preservatives is one of the foremost leading challenges for food manufacturing industries because synthetic...  相似文献   
36.
Plant and Soil - Abiotic stresses are threatening wheat productivity across the globe, which is often associated with nutrient deficiencies. Zinc (Zn) is involved in many physiological processes of...  相似文献   
37.
Globally, riparian zones along river banks are widely recognized for their vital role in water regulation and conservation of biodiversity. Here, we specifically investigated the floristic and functional diversity of the vegetation of the riparian zones of protected forests in Kashmir Himalaya, India. A random sampling method was used for site selection while a transect method was used for data collection. Data obtained from the field was subjected to taxonomic and functional classification. Floristic analysis revealed a total of 78 species belonging to 68 genera in 40 families, suggesting an unequal distribution of species among families. Nine families contributed half of the species: Rosaceae was the dominant family with nine (12%) species followed by Asteraceae with eight species (10%), while 23 families were monotypic. In terms of functional trait diversity, herbaceous and perennial taxa dominated, and the biological spectrum showed a dominance of the therophytic life form, indicative of disturbed vegetation. The phenological spectrum revealed that the maximum flowering periods starts in March and extends into May, in which a total of 61% of the species were observed to flower. The leading leaf size spectra were mesophyll with 35%, followed by microphyll (31%). Most (64%) of the species had a simple leaf lamina type. The results of the present study serve as a means to evaluate best management practices, assess restoration and mitigation projects, prioritize riparian related resource management decisions, and establish aquatic life use standards.  相似文献   
38.
Formation of bacterial biofilms is a risk with many in situ medical devices. Biofilm-forming Bacillus species are associated with potentially life-threatening catheter-related blood stream infections in immunocompromised patients. Here, bacteria were isolated from biofilm-like structures within the lumen of central venous catheters (CVCs) from two patients admitted to cardiac hospital wards. Isolates belonged to the Bacillus cereus group, exhibited strong biofilm formation propensity, and mapped phylogenetically close to the B. cereus emetic cluster. Together, whole genome sequencing and quantitative PCR confirmed that the isolates constituted the same strain and possessed a range of genes important for and up-regulated during biofilm formation. Antimicrobial susceptibility testing demonstrated resistance to trimethoprim-sulphamethoxazole, clindamycin, penicillin and ampicillin. Inspection of the genome revealed several chromosomal β-lactamase genes and a sulphonamide resistant variant of folP. This study clearly shows that B. cereus persisting in hospital ward environments may constitute a risk factor from repeated contamination of CVCs.  相似文献   
39.
Glycoprotein Ibα (GpIbα) binding ability of A1 domain of von Willebrand factor (vWF) facilitates platelet adhesion that plays a crucial role in maintaining hemostasis and thrombosis at the site of vascular damage. There are both “loss as well as gain of function” mutations observed in this domain. Naturally occurring “gain of function” mutations leave self-activating impacts on the A1 domain which turns the normal binding to characteristic constitutive binding with GPIbα. These “gain of function” mutations are associated with the von Willebrand disease type 2B. In recent years, studies focused on understanding the mechanism and conformational patterns attached to these phenomena have been conducted, but the conformational pathways leading to such binding patterns are poorly understood as of now. To obtain a microscopic picture of such events for the better understanding of pathways, we used molecular dynamics (MD) simulations along with principal component analysis and normal mode analysis to study the effects of Pro1266Leu (Pro503Leu in structural context) mutation on the structure and function of A1 domain of vWF. MD simulations have provided atomic-level details of intermolecular motions as a function of time to understand the dynamic behavior of A1 domain of vWF. Comparative analysis of the trajectories obtained from MD simulations of both the wild type and Pro503Leu mutant suggesting appreciable conformational changes in the structure of mutant which might provide a basis for assuming the “gain of function” effects of these mutations on the A1 domain of vWF, resulting in the constitutive binding with GpIbα.  相似文献   
40.
Protection of telomere 1 (POT1) is one of the key components of shelterin complex, implicated in maintaining the telomere homeostasis, and thus stability of the eukaryotic genome. A large number of non-synonymous single nucleotide polymorphisms (nsSNPs) in the POT1 gene have been reported to cause varieties of human diseases, including cancer. In recent years, a number of mutations in POT1 has been markedly increased, and interpreting the effect of these large numbers of mutations to understand the mechanism of associated diseases seems impossible using experimental approaches. Herein, we employ varieties of computational methods such as PROVEAN, PolyPhen-2, SIFT, PoPMuSiC, SDM2, STRUM, and MAESTRO to identify the effects of 387 nsSNPs on the structure and function of POT1 protein. We have identified about 183 nsSNPs as deleterious and termed them as “high-confidence nsSNPs.” Distribution of these high-confidence nsSNPs demonstrates that the mutation in oligonucleotide binding domain 1 is highly deleterious (one in every three nsSNPs), and high-confidence nsSNPs show a strong correlation with residue conservation. The structure analysis provides a detailed insights into the structural changes occurred in consequence of conserved mutations which lead to the cancer progression. This study, for the first time, offers a newer prospective on the role of POT1 mutations on the structure, function, and their relation to associated diseases.  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