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   990篇
  免费   33篇
  国内免费   1篇
  2023年   15篇
  2022年   10篇
  2021年   24篇
  2020年   11篇
  2019年   10篇
  2018年   22篇
  2017年   25篇
  2016年   40篇
  2015年   36篇
  2014年   59篇
  2013年   67篇
  2012年   84篇
  2011年   81篇
  2010年   60篇
  2009年   49篇
  2008年   69篇
  2007年   46篇
  2006年   58篇
  2005年   58篇
  2004年   58篇
  2003年   64篇
  2002年   40篇
  2001年   5篇
  2000年   5篇
  1999年   2篇
  1998年   6篇
  1997年   3篇
  1996年   3篇
  1994年   5篇
  1993年   1篇
  1992年   2篇
  1991年   2篇
  1989年   1篇
  1984年   1篇
  1979年   1篇
  1977年   1篇
排序方式: 共有1024条查询结果,搜索用时 46 毫秒
931.
932.
Cevik MÖ  Erden A 《PloS one》2012,7(6):e39863
The proboscis extension reflex (PER) is triggered when insects' gustatory receptors contact appetitive stimuli, so it provides a behavioral readout for perceptual encoding of tastants. Research on the experience dependent modulation of PER in Drosophila has been hindered by the difficulty of obtaining reliable measures of memory-driven change in PER probability in the background of larger changes induced by physiological state. In this study, we showed that the course of PER habituation can be predicted by the degree of sucrose responsiveness in Drosophila. We assessed early response parameters, including the number of proboscis extensions and labellar movements in the first five trials, the trial to start responding, and the trial to make the first stop to quantify responsiveness, which predicted the upcoming pattern of both the short-term and 1 hour memory of PER habituation for individual flies. The cAMP signaling pathway mutant rutabaga displayed deficits in attunement of perceptual salience of sucrose to physiological demands and stimulus-driven sensitization.  相似文献   
933.
The aim was to investigate the prevalence of VKORC1 and CYP2C9 genotypes in patients requiring anticoagulant therapy in two different region’s populations of Turkey. The recent cohort included 292 patients that needed anticoagulant therapy, and who had a history of deep vein thrombosis and/or pulmonary artery thromboembolism. Genomic DNA was isolated from peripheral blood samples and the StripAssay reverse hybridization or Real Time PCR technique was used for genotype analysis. Genotypes for CYP2C9 were detected as follows: 165 (56.5?%) for CYP2C9*1/*1, 67 (23.0?%) for CYP2C9*1/*2, 25 (8.6?%) for CYP2C9*1/*3, 9 (3.0?%) for CYP2C9*2/*2, 21 (7.2?%) for CYP2C9*2/*3, 5(1.7?%) for CYP2C9*3/*3 for CYP2C9 and the allele frequencies were: 0.723 for allele*1, 0.182 for allele*2 and 0.095 for allele*3 respectively. Genotypes for VKORC1 were detected as follows: 64 (21.9?%) for GG, 220 (75.4?%) for GA and 8 (2.7?%) for AA alleles. The G allele frequency was detected as 0.596, and the A allele frequency was 0.404. The VKORC1 1639 G>A and CYP2C9 mutation prevalence and allele frequency of the current results from two different populations (Sivas and Canakkale) showed similarly very variable profiles when compared to the other results from the Turkish population.  相似文献   
934.
The aim of this study was to analyze the expression of microfibril-associated protein 2 (MFAP2), microfibril-associated protein 5 (MFAP5) and nuclear localized factor 2 (NLF2) genes in patients with repeated IVF failure and compare with fertile population. Total RNA was isolated from 38 patients (repeated implantation failure, group 1, n = 22; fertile patients, group 2, n = 16). mRNA expression levels were measured quantitatively using real-time polymerase chain reaction. Our results showed that mRNA expression of NLF2 significantly decreased in the infertility group as compared to control group (P = 0.023). In addition a marked decrease was observed in the expression of MFAP2 in women with repeated implantation failure. In conclusion, NLF2 gene expression levels and differences in MFAP2 and MFAP5 gene expressions (albeit being insignificant) between infertile group and control group draw attention to a genetic basis under implantation failure.  相似文献   
935.
GG Dogu  A Kargi  S Turgut  C Ayada  BY Taskoylu  G Demiray  A Yaren  C Ozlu  S Temel  A Ergin 《Gene》2012,506(2):404-407
We assessed whether single nucleotide polymorphisms (SNPs) in MDR1 gene C3435T predicted the outcome of platinum-based chemotherapies and survival in our non small cell lung cancer (NSCLC) patients. A total of 79 non-small cell lung cancer patients were enrolled to study. We determined the MDR1 C3435T single nucleotide gene polymorphisms. Median age was 60years: 91.7% male, 8.9% female. We found that CC, CT, TT genotype and T, C allele frequencies in lung cancer patients as 24.1%, 62%, 13.9% and 44.3%, 55.7%, respectively. Patients with CT genotype had a higher response rate (11.4%) than the other genotypes. However, this difference is not statistically significant (p=0.743). Cox regression analysis for overall survival showed that ECOG PS status 0 (HR PS 1 vs. 0, 5.68 p=0.002; HR of PS 2 vs. 0 is 21.579, p=0.001; HR of PS 3 vs. 0 is 35.35, p=0.001), stage ≤II (HR of stage III vs. I+II is 17.77; p=0.016, HR of stage IV vs. I+II is 26.97, p=0.006), and albumin level ≥3g/dl (HR of albumin <3g/dl vs. ≥3g/dl is 2.46, p=0.044) were the most important prognostic factors (also, time to progression was related to these factors). There was no significant association between the genotypes and clinicopathologic parameters; however, good performance status, early stage and ≥3g/dl albumin level were found to be the most important prognostic factors for overall survival and progression-free survival.  相似文献   
936.
Landraces of maize represent a valuable genetic resource for breeding and genetic studies. Since 1970, landraces have been collected from all over Turkey, but the genetic diversity represented in this collection is still largely unknown. In this study, a sample of 98 landraces sampled from 45 provinces of Turkey was assessed genotypically at 28 simple sequence repeat (SSR) loci and phenotypically for 19 morphological traits. The landraces varied significantly for all the latter traits. A total of 172 SSR alleles were detected, giving a mean of 6.21 alleles per locus. The genetic distance between pairs of landraces ranged from 0.18 to 0.63, with a mean of 0.35. Positive and negative correlation exists among different morphological and agronomic traits. Positive association among different traits showed that improvement of one character may simultaneously improve the other desired trait. Based on UPGMA dendrogram and Neighbor-Net (NNET) analyses from both morphological traits and SSR data, respectively, it is obvious that maize landraces from the same geographical region were often placed in different clusters, indicating that grouping based on genetic parameters was not closely related to the geographic origin. The wide diversity present in Turkish maize landraces could be used as genetic resource in designing maize breeding program for developing new cultivars adapted to different geographic and climatic conditions, and may also contribute to worldwide breeding programs.  相似文献   
937.
Quantification of plantar tissue behavior of the heel pad is essential in developing computational models for predictive analysis of preventive treatment options such as footwear for patients with diabetes. Simulation based studies in the past have generally adopted heel pad properties from the literature, in return using heel-specific geometry with material properties of a different heel. In exceptional cases, patient-specific material characterization was performed with simplified two-dimensional models, without further evaluation of a heel-specific response under different loading conditions. The aim of this study was to conduct an inverse finite element analysis of the heel in order to calculate heel-specific material properties in situ. Multidimensional experimental data available from a previous cadaver study by Erdemir et al. ("An Elaborate Data Set Characterizing the Mechanical Response of the Foot," ASME J. Biomech. Eng., 131(9), pp. 094502) was used for model development, optimization, and evaluation of material properties. A specimen-specific three-dimensional finite element representation was developed. Heel pad material properties were determined using inverse finite element analysis by fitting the model behavior to the experimental data. Compression dominant loading, applied using a spherical indenter, was used for optimization of the material properties. The optimized material properties were evaluated through simulations representative of a combined loading scenario (compression and anterior-posterior shear) with a spherical indenter and also of a compression dominant loading applied using an elevated platform. Optimized heel pad material coefficients were 0.001084 MPa (μ), 9.780 (α) (with an effective Poisson's ratio (ν) of 0.475), for a first-order nearly incompressible Ogden material model. The model predicted structural response of the heel pad was in good agreement for both the optimization (<1.05% maximum tool force, 0.9% maximum tool displacement) and validation cases (6.5% maximum tool force, 15% maximum tool displacement). The inverse analysis successfully predicted the material properties for the given specimen-specific heel pad using the experimental data for the specimen. The modeling framework and results can be used for accurate predictions of the three-dimensional interaction of the heel pad with its surroundings.  相似文献   
938.
939.
Objective: Heparanase (HPA) is an endo-β-D-glucuronidase capable of degrading heparin sulphate (HS) and heparin side chains. HPA plays a role in tumour growth, angiogenesis, cell invasion and in activation of the coagulation system. We aimed to investigate the relationship between HPA and thrombus burden (TB) in patients with ST-Segment Elevation Myocardial Infarction (STEMI).

Methods: This prospective study enrolled 187 patients with STEMI who were treated with primary percutaneous coronary intervention (pPCI). Blood samples were taken to determine serum HPA levels prior to coronary angiography and heparin administration. Serum HPA analysis was performed with a commercially available Human Elisa kit.

Results: Patients were divided into two groups: high TB (n:58) and low TB (n:129) group. Serum HPA levels were significantly higher in patients with high TB than low TB [250.1 (188.5–338.1) vs. 173.6 (134.3–219.8) pg/mL] (p?<?0.001). Serum HPA levels were higher in patients with no-reflow phenomenon compared with others [(409.3 (375.6–512.5) pg/mL vs. 186.2 (144.2–247.4) pg/mL, p?<?0.001]. In multiple logistic regression analysis HPA was a predictor of high TB.

Conclusion: Elevated HPA level in patients with STEMI is related to high TB. Furthermore, increased HPA level may be associated with thrombotic complications such as no-reflow phenomenon in patients with STEMI.  相似文献   

940.
Sleep and Biological Rhythms - Obstructive sleep apnea syndrome (OSAS) is a commonly seen disorder characterized by repeated episodes of upper airway obstruction during sleep leading to...  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