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   777篇
  免费   63篇
  国内免费   3篇
  2024年   4篇
  2023年   11篇
  2022年   25篇
  2021年   28篇
  2020年   28篇
  2019年   30篇
  2018年   40篇
  2017年   22篇
  2016年   33篇
  2015年   33篇
  2014年   54篇
  2013年   52篇
  2012年   55篇
  2011年   67篇
  2010年   29篇
  2009年   29篇
  2008年   30篇
  2007年   18篇
  2006年   21篇
  2005年   20篇
  2004年   23篇
  2003年   19篇
  2002年   21篇
  2001年   11篇
  2000年   8篇
  1999年   6篇
  1998年   3篇
  1996年   5篇
  1995年   8篇
  1994年   5篇
  1992年   7篇
  1987年   3篇
  1986年   6篇
  1985年   5篇
  1984年   5篇
  1982年   3篇
  1981年   4篇
  1979年   5篇
  1978年   5篇
  1976年   4篇
  1975年   6篇
  1974年   4篇
  1973年   2篇
  1972年   4篇
  1971年   2篇
  1969年   4篇
  1968年   2篇
  1967年   4篇
  1965年   4篇
  1964年   2篇
排序方式: 共有843条查询结果,搜索用时 31 毫秒
161.
162.
Patients with a decrease in limb perfusion with a potential threat to limb viability manifested by ischemic rest pain, ischemic ulcers, and/or gangrene are considered to have critical limb ischemia (CLI). Because of this generally poor outcome, there is a strong need for attempting any procedure to save the affected limb. The aim of this work is to evaluate the possibility to use stem cell therapy as a treatment option for patients with chronic critical lower limb ischemia with no distal run off. This study includes 20 patients with chronic critical lower limb ischemia with no distal run off who are unsuitable for vascular or endovascular option. These patients underwent stem cell therapy (SCT) by autologous transplantation of bone marrow derived mononuclear cells. 55 % of patients treated with SCT showed improvement of the rest pain after the first month, 60 % continued improvement of the rest pain after 6 months, 75 % after 1 year and 80 % after 2 years and continued without any deterioration till the third year. Limb salvage rate after STC was 80 % after the first year till the end of the second and third years. SCT can result in angiogenesis in patients with no-option CLI, providing a foundation for the application of this therapy to leg ischemia.  相似文献   
163.
Multiple DNA double-strand break (DSB) repair pathways are active in S phase of the cell cycle; however, DSBs are primarily repaired by homologous recombination (HR) in this cell cycle phase. As the non-homologous end-joining (NHEJ) factor, Ku70/80 (Ku), is quickly recruited to DSBs in S phase, we hypothesized that an orchestrated mechanism modulates pathway choice between HR and NHEJ via displacement of the Ku heterodimer from DSBs to allow HR. Here, we provide evidence that phosphorylation at a cluster of sites in the junction of the pillar and bridge regions of Ku70 mediates the dissociation of Ku from DSBs. Mimicking phosphorylation at these sites reduces Ku''s affinity for DSB ends, suggesting that phosphorylation of Ku70 induces a conformational change responsible for the dissociation of the Ku heterodimer from DNA ends. Ablating phosphorylation of Ku70 leads to the sustained retention of Ku at DSBs, resulting in a significant decrease in DNA end resection and HR, specifically in S phase. This decrease in HR is specific as these phosphorylation sites are not required for NHEJ. Our results demonstrate that the phosphorylation-mediated dissociation of Ku70/80 from DSBs frees DNA ends, allowing the initiation of HR in S phase and providing a mechanism of DSB repair pathway choice in mammalian cells.  相似文献   
164.
165.

Purpose/Objectives

To investigate pN1 prostate cancer (PCa) patients treated surgically without immediate adjuvant treatment.

Materials and Methods

We analyzed the database of 2316 patients at our institution who underwent robot-assisted radical prostatectomy (RARP)/radical prostatectomy (RP) between July 2005 and November 2012. 87 patients with pN1 PCa and received no neoadjuvant and immediate adjuvant therapy were included in the study. Included pN1 PCa patients were followed up for median of 60 months. Biochemical recurrence (BCR)-free survival, metastasis-free survival (MFS), cancer specific survival (CSS), and overall survival (OS) rates were determined by using Kaplan-Meier analysis. Cox regression analysis was performed to investigate the impact of prostate-specific antigen (PSA) level, Gleason score, extraprostatic extension, seminal vesicle invasion, perineural invasion, lymphovascular invasion, positive surgical margin, tumor volume, early post-operative PSA(6 weeks), PSA nadir, lymph node yield, and number of pathologically positive lymph nodes on survival.

Results

The 5-year OS rate of patients was 86.1%, while the CSS rate was 89.6%. The metastasis-free and BCR-free survival rates were 71% and 19.1%, respectively, and each was significantly correlated with the number of positive lymph nodes on log rank tests (p = 0.004 and p = 0.039, respectively). The presence of 2 or more pathologically positive LNs (HR:2.20; 95% CI 1.30–3.72; p = 0.003) and a Gleason score ≥8 (HR: 2.40;95% CI: 1.32–4.38; p = 0.04) were significant negative predictors of BCR free survival on multivariable regression analysis. Furthermore, the presence of 2 or more positive lymph nodes (HR: 1.06; 95% CI 1.01–1.11; p = 0.029) were significant negative predictors of metastasis-free survival on multivariable regression analysis. Additionally, in the patients who had no BCR without adjuvant treatment 9 patients out of 10 (90%) had single positive LN and 5 patients out of 10 (50%) had Gleason score 7. Therefore, single positive LN, and Gleason scores ≤7 have significantly low risk of disease progression.

Conclusions

pN1 PCa patients have heterogenous clinical courses. Patients with single positive LN, and Gleason scores ≤7 have low risk of recurrence. Close observation with delayed adjuvant hormone therapy can be considered in these patients.  相似文献   
166.
Hemicellulose was extracted from horse bean and wheat straws in a yield of 5 and 9% respectively. The whole hemicellulose was hydrolysed and the molar ratio of the component monosaccharides was determined. Uronic acid, galactose, glucose, arabinose and xylose were found in both hemicelluloses. The molar ratio of the monosaccharides was determined in each of 4 fractions derived from the saccharide. The main fractions (B and C) were partially hydrolysed and an oligosaccharide containing arabinose and xylose (1:1) was isolated from both hemicelluloses. Another oligosaccharide containing xylose and glucose (2:1) was also isolated from wheat straw hemicellulose. Periodate oxidation was carried out on fractions B and C. The formic acid and the consumed periodate were determined. Each hemicellulose was subjected to Smith's degradation. Glycerol, erythrytol and compounds containing xylose and glycerol (1:1), and xylose and erythrytol (1:1) were isolated.  相似文献   
167.
1. The effects of lethal zinc concentrations on some physiological and biochemical parameters in Clarias lazera and Tilapia zilli were investigated. 2. The analyses of lactate, pyruvate and glycogen in both liver and muscle tissues and the relation among them have been studied in detail. 3. Significant increases were observed in liver and serum proteins, serum alkaline phosphatase (ALP), erythrocyte count (RBCs), haematocrit or packed cell volume (PCV) and haemoglobin (HB) concentrations. 4. Zinc exposure reduced liver and serum acid phosphatase (ACP) as well as liver alkaline phosphatase (ALP).  相似文献   
168.
The diatom flora of a district in Jebel Marra, Sudan, has been qualitatively analysed. The periphyton is related to the type of substratum with which the various diatoms associated. Certain diatoms were found to be restricted to one habitat, while others were common to more than one. All species recorded belong to the Pennales. Comparison with regions in the Southern and Northern hemisphere is made.  相似文献   
169.
170.
This study presents a novel three‐dimensional analysis using statistical atlases and automated measurements to assess diaphyseal morphology of the clavicle and its relationship to muscle asymmetry. A sample of 505 individuals (285 males, 220 females) from the William McCormick Clavicle Collection was CT scanned, segmented, and added to a statistical bone atlas that captures correspondence between homologous points on the bone surfaces. Muscle attachment sites were localized on the atlas and then propagated across the entire population. Cross‐sectional contours were extracted at 5% increments along the entire bone, as well as at muscle attachment sites and the clavicle waist; maximum and minimum dimensions of each cross‐sectional contour were calculated. In addition, the entire three‐dimensional surface was examined for asymmetry by analyzing the magnitude and directional differences between homologous points across all bone surfaces in the dataset. The results confirm the existing studies on clavicle asymmetry, namely that the left clavicle is longer than the right, but the right is more robust than the left. However, the patterns of asymmetry are sexually dimorphic. Males are significantly asymmetric in all dimensions and at muscle and ligament attachment sites (P < 0.05), whereas female asymmetry is more variable. We hypothesize that this is related to absolute and relative differences in male muscle strength compared to females. However, an area with no muscle attachments on the posterior midshaft was significantly asymmetric in both sexes. We suggest that this is a curvature difference caused by opposing muscle actions at the medial and lateral ends of the bone. Am J Phys Anthropol 2012. © 2012 Wiley Periodicals, Inc.  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