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   652篇
  免费   45篇
  国内免费   1篇
  698篇
  2024年   3篇
  2023年   5篇
  2022年   22篇
  2021年   37篇
  2020年   19篇
  2019年   23篇
  2018年   51篇
  2017年   30篇
  2016年   36篇
  2015年   47篇
  2014年   44篇
  2013年   38篇
  2012年   42篇
  2011年   51篇
  2010年   26篇
  2009年   28篇
  2008年   32篇
  2007年   18篇
  2006年   18篇
  2005年   19篇
  2004年   25篇
  2003年   19篇
  2002年   13篇
  2001年   3篇
  2000年   6篇
  1999年   2篇
  1998年   6篇
  1996年   2篇
  1995年   2篇
  1994年   1篇
  1992年   2篇
  1991年   1篇
  1990年   2篇
  1989年   1篇
  1988年   5篇
  1987年   2篇
  1985年   2篇
  1984年   1篇
  1981年   1篇
  1980年   5篇
  1979年   1篇
  1976年   1篇
  1974年   3篇
  1972年   1篇
  1971年   2篇
排序方式: 共有698条查询结果,搜索用时 15 毫秒
1.
BackgroundThe purpose of this study was to assess the impact of coincidental radiotherapy on the volume of the non-malignant prostate gland in rectal cancer patients treated with neo-adjuvant radiotherapy.Materials and methodsIn this retrospective analysis, thirty male patients with rectal cancer who had neoadjuvant radiotherapy met the inclusion criteria. These patients had pre-treatment magnetic resonance imaging (MRI) and at least one post-treatment MRI of the pelvis and the whole of their prostate volume received the full prescribed radiotherapy dose; 45 Gy in 25 fractions (n = 22), 45 Gy in 20 fractions (n = 4) and 25 Gy in 5 fractions (n = 4).ResultsThe median age of this patient cohort was 66 years (range: 30–87). With a median interval between pre-treatment MRI and first MRI post-treatment of 2 months (range: 1–11), the mean prostate volume reduced from 36.1 cm3 [standard deviation (SD) 14.2] pre-radiotherapy to 31.3 cm3 (SD 13.0) post radiotherapy and this difference was significant (p = 0.0004).ConclusionRadiotherapy may cause shrinkage in volume of normal (non-malignant) prostate. Further research is required in this field, since these results may be of some comfort to men contemplating the consequences of radiotherapy on their quality of life. The authors suggest recording flow-rate and international prostate symptom score (IPSS) during rectal radiotherapy as a next step.  相似文献   
2.
Cadmium (Cd) is highly toxic metal for plant metabolic processes even in low concentration due to its longer half-life and non-biodegradable nature. The current study was designed to assess the bioremediation potential of a Cd-tolerant phytobeneficial bacterial strain Bacillus sp. SDA-4, isolated, characterized and identified from Chakera wastewater reservoir, Faisalabad, Pakistan, together with spinach (as a test plant) under different Cd regimes. Spinach plants were grown with and without Bacillus sp. SDA-4 inoculation in pots filled with 0, 5 or 10 mg kg−1 CdCl2-spiked soil. Without Bacillus sp. SDA-4 inoculation, spinach plants exhibited reduction in biomass accumulation, antioxidative enzymes and nutrient retention. However, plants inoculated with Bacillus sp. SDA-4 revealed significantly augmented growth, biomass accumulation and efficiency of antioxidative machinery with concomitant reduction in proline and MDA contents under Cd stress. Furthermore, application of Bacillus sp. SDA-4 assisted the Cd-stressed plants to sustain optimal levels of essential nutrients (N, P, K, Ca and Mg). It was inferred that the characterized Cd-tolerant PGPR strain, Bacillus sp. SDA-4 has a potential to reduce Cd uptake and lipid peroxidation which in turn maintained the optimum balance of nutrients and augmented the growth of Cd-stressed spinach. Analysis of bioconcentration factor (BCF) and translocation factor (TF) revealed that Bacillus sp. SDA-4 inoculation with spinach sequestered Cd in rhizospheric zone. Research outcomes are important for understanding morpho-physio-biochemical attributes of spinach-Bacillus sp. SDA-4 synergy which might provide efficient strategies to decrease Cd retention in edible plants and/or bioremediation of Cd polluted soil colloids.  相似文献   
3.
4.

Cotton fibre quality is a multigenic trait. Genetic modification of different genes to achieve high quality fibre is difficult without knowing the mechanism lying behind genes interaction. Based on background knowledge an attempt to explore the potential structural interactions between Gossypium hirsutum Wlim5 domain1 and Gossypium hirsutum ACTIN-1 proteins was done in current study. Sequence features of the LIM domain1 of GhWlim5 protein were identified through multiple sequence alignment analysis, and a phylogenetic tree was built to identify evolutionary relationships between sequences. Conservation indicated the evolutionary importance of side chain residues and the presence of several aliphatic and/or bulky residues, which stabilize the protein core and facilitate packing of zinc fingers. The structures of GhWlim5 domain1 and GhACTIN-1 proteins were modelled and validated through computational methods. Validation of GhACTIN-1 and GhWlim5 domain1 structures indicated good structural quality with 99.7% and 100% of the favoured number of residues in allowed regions and Z-score, within the ranges of − 9.87 and − 4.17, respectively. Docking analysis indicated various possible modes of interaction between these two proteins with favourable binding affinities. Based on our strong binding interaction results between GhWlim5 domain1 and GhACTIN-1 proteins, we further investigated the role of over-expression of GhWlim5 by transformation in cotton plants under fibre specific promoter and transgenic plants displayed significant increases in fibre strength.

  相似文献   
5.
Russian Journal of Bioorganic Chemistry - In the present research work, a new series of N-(substituted-phenyl)-3-(4-phenyl-1-piperazinyl)propanamides were synthesized. The synthesis was initiated...  相似文献   
6.
The cytotoxicity in freshwater fishes due to different industrial dyes in industrial effluents is a major worldwide issue. Hematoxylin dye has a wide range of uses in textile industries and laboratories. This study was aimed to evaluate the toxic effects of hematoxylin's sublethal effect in vitro in Cirrhinus mrigala. The fish was exposed to different grading concentrations of dye in the aquarium. Fish were sacrificed and dissected to remove the kidney after exposure to hematoxylin dye for specific time intervals. Nephrotoxicity and cytotoxicity induced by this dye were detected through histopathology by using the paraffin wax method. Immediate mortality of fish was noticed against the exposure to 0.08 g/L (LC50) concentration of dye, but at 0.008 mg/L and 0.018 mg/L, it showed tremendous tissue damage in the kidneys, significant reduction in fish growth. This dye induced many alterations in the kidney such as tubular degeneration, vacuolation, shrinkage of a glomerulus, reduced lumen, congestion in the kidney, glomerulonephritis, absence of Bowmen space, necrosis of the hematopoietic interstitial tissues, clogging of tubules, necrosis in the glomerulus and increased space between glomerulus and bowmen's capsule. Although this dye has a wide range of biological and industrial applications, a minute amount of hematoxylin released in effluents is quite toxic to aquatic fauna.  相似文献   
7.
The present work aims to synthesize zinc oxide (ZnO) nanoparticles via green approaches using leaf extract of Parthenium hysterophorus. UV–vis and FT-IR tests confirmed the existence of biomolecules, active materials, and metal oxides. The X-ray diffraction structural study exposes the ZnO nanoparticles formation with hexagonal phase structures. SEM and TEM analysis reveal surface morphologies of ZnO nanoparticles and most of them are spherical with a size range of 10 nm. ZnO nanoparticles were revealed strong antimicrobial activity against both bacterial and fungal strains. The germination of seeds and vegetative growth of Sesamum indicum has been greatly improved.  相似文献   
8.
Hepatitis C virus (HCV) subtypes are pre-requisite to predict endemicity, epidemiology, clinical pathogenesis, diagnosis, and treatment of chronic hepatitis C infection. HCV genotypes 4 and 1 are the most prevalent in Saudi Arabia, however; less consensus data exist on circulating HCV subtypes in infected individuals. This study was aimed to demonstrate the virological surveillance, phylogenetic analysis, and evolutionary relationship of HCV genotypes 4 and 1 subtypes in the Saudi population with the rest of the world. Fifty-five clinical specimens from different parts of the country were analyzed based on 5′ untranslated region (5′ UTR) amplification, direct sequencing, and for molecular evolutionary genetic analysis. Pair-wise comparison and multiple sequence alignment were performed to determine the nucleotide conservation, nucleotide variation, and positional mutations within the sequenced isolates. The evolutionary relationship of sequenced HCV isolates with referenced HCV strains from the rest of the world was established by computing pairwise genetic distances and generating phylogenetic trees. Twelve new sequences were submitted to GenBank, NCBI database. The results revealed that HCV subtype 4a is more prevalent preceded by 1a in the Saudi population. Molecular phylogeny predicts the descendants’ relationship of subtype 4a isolates very close to Egyptian prototype HCV strains, while 1a isolates were homogeneous and clustering to the European and North American genetic lineages. The implications of this study highlight the importance of HCV subtyping as an indispensable tool to monitor the distribution of viral strains, to determine the risk factors of infection prevalence, and to investigate clinical differences of treatment outcomes among intergenotypic and intragenotypic isolates in the treated population.  相似文献   
9.
Preclinical studies of animals with risk factors, and how those risk factors contribute to the development of cardiovascular disease and cardiac dysfunction, are clearly needed. One such approach is to feed mice a diet rich in fat (i.e. 60%). Here, we determined whether a high fat diet was sufficient to induce cardiac dysfunction in mice. We subjected mice to two different high fat diets (lard or milk as fat source) and followed them for over six months and found no significant decrement in cardiac function (via echocardiography), despite robust adiposity and impaired glucose disposal. We next determined whether antecedent and concomitant exposure to high fat diet (lard) altered the murine heart’s response to infarct-induced heart failure; high fat feeding during, or before and during, heart failure did not significantly exacerbate cardiac dysfunction. Given the lack of a robust effect on cardiac dysfunction with high fat feeding, we then examined a commonly used mouse model of overt diabetes, hyperglycemia, and obesity (db/db mice). db/db mice (or STZ treated wild-type mice) subjected to pressure overload exhibited no significant exacerbation of cardiac dysfunction; however, ischemia-reperfusion injury significantly depressed cardiac function in db/db mice compared to their non-diabetic littermates. Thus, we were able to document a negative influence of a risk factor in a relevant cardiovascular disease model; however, this did not involve exposure to a high fat diet. High fat diet, obesity, or hyperglycemia does not necessarily induce cardiac dysfunction in mice. Although many investigators use such diabetes/obesity models to understand cardiac defects related to risk factors, this study, along with those from several other groups, serves as a cautionary note regarding the use of murine models of diabetes and obesity in the context of heart failure.  相似文献   
10.
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