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   1931篇
  免费   89篇
  国内免费   13篇
耳鼻咽喉   13篇
儿科学   78篇
妇产科学   34篇
基础医学   342篇
口腔科学   24篇
临床医学   116篇
内科学   300篇
皮肤病学   31篇
神经病学   307篇
特种医学   60篇
外科学   216篇
综合类   3篇
预防医学   41篇
眼科学   209篇
药学   161篇
中国医学   12篇
肿瘤学   86篇
  2022年   14篇
  2021年   32篇
  2020年   16篇
  2019年   36篇
  2018年   47篇
  2017年   33篇
  2016年   42篇
  2015年   46篇
  2014年   46篇
  2013年   75篇
  2012年   97篇
  2011年   91篇
  2010年   56篇
  2009年   56篇
  2008年   77篇
  2007年   86篇
  2006年   117篇
  2005年   96篇
  2004年   75篇
  2003年   66篇
  2002年   72篇
  2001年   28篇
  2000年   18篇
  1999年   16篇
  1998年   19篇
  1992年   11篇
  1991年   12篇
  1990年   21篇
  1989年   19篇
  1988年   15篇
  1987年   11篇
  1986年   12篇
  1936年   10篇
  1934年   9篇
  1933年   14篇
  1932年   12篇
  1931年   13篇
  1930年   15篇
  1929年   15篇
  1928年   19篇
  1927年   18篇
  1926年   16篇
  1925年   22篇
  1924年   24篇
  1923年   16篇
  1922年   16篇
  1921年   10篇
  1911年   11篇
  1908年   9篇
  1905年   9篇
排序方式: 共有2033条查询结果,搜索用时 9 毫秒
21.
Phase-derived parameters and time autocorrelation functions were used to analyze the behavior of murine B16 cells exposed to different amplitudes of electroporation pulses. Cells were observed using an off-axis digital holographic microscope equipped with a fast camera. Series of quantitative phase images of cells were reconstructed and further processed using MATLAB codes. Projected area, dry mass density, and entropy proved to be predictors for permeabilized cells that swell or collapse. Autocorrelation functions of phase fluctuations in different regions of the cell showed a good correlation with the local effectiveness of permeabilization.  相似文献   
22.
23.
24.
It has been recently shown that 20 min of mechanical flutter stimulation induces lasting motor cortical excitability changes, as assessed by transcranial magnetic stimulation in relaxed hand muscles. The present functional magnetic resonance imaging (fMRI) study aims to examine if such neuromodulatory changes are reflected in the BOLD signal during a motor test. Therefore, two groups were recruited: one group receiving whole‐hand flutter stimulation with a frequency of 25 Hz (FSTIM group, n = 22) and a second group receiving no stimulation (NOSTIM group, n = 22). As motor test finger‐to‐thumb tapping was performed to activate a wide sensorimotor network during the fMRI measurements. Three fMRI measurements were obtained with this test: before stimulation (PRE), after stimulation (POST1), and 1 h after stimulation (POST2). Three regions of interest (ROIs) were defined: primary motor area (M1), primary somatosensory area (S1), and supplementary motor area. In the absence of baseline differences between both groups, the FSTIM group showed increased movement‐related brain activations compared with the NOSTIM group, both at POST1 and POST2. ROI analysis revealed increased blood‐oxygenation‐level‐dependent (BOLD) responses within contralateral S1 (+20%) and M1 (+25%) at POST1, which lasted until POST2. These poststimulatory effects within S1 and M1 obviously reflect neuroplastic changes associated with augmented cortical excitability. These findings are of high clinical relevance, for example, to improve the treatment of stroke patients. Hum Brain Mapp 34:2767–2774, 2013. © 2012 Wiley Periodicals, Inc.  相似文献   
25.
26.
Red cell superoxide dismutase (SOD), glutathione peroxidase (GPX) and catalase (CAT) were measured in 66 burned patients (57 men, 9 women, age 16–78 years). BSAB varied from 15 to 93% and ABSI from 3 to 14 points. In the first week after injury the activity of SOD was significantly decreased as compared with the activity of the enzymes in the control group and was also below the reference values. Later the activity of SOD increased up to the normal range. The activity of CAT followed a similar pattern but the differences were not significant. No significant changes in red cell GPX were found during the monitored period. We did not find any significant association between the antioxidant enzyme activities and the markers of burns severity. On the other side there was a significant indirect association between the change of SOD activity (calculated as a difference between the first week values after the injury and the activities measured later) and BSAB.  相似文献   
27.
28.
29.

Background

Patients with cleidocranial dysplasia (CCD) present a thickend and fibrotic gingiva.

Purpose

To the best of our knowledge it was analysed for the first time, whether this is correlated with an increased rate of collagen I in oral mucosa.

Patients and methods

27 soft tissue biopsies of six CCD-patients and 17 tissue samples of 12 healthy persons were labled with a monoclonal antibody against collagen I and the bound antibodies were detected with alkaline phosphatase-anti-alkaline phophatase-kit. The histological slices were analysed by a digital image recognition software under a fully automated microscope and the rate of collagen I was converted into amounts of grey tones.

Results

The amount of grey tones reached from 11.909 to 15.319 in the CCD-group, and from 2752 to 12.556 in the control group. The U-Test of Mann, Whitney and Wilcoxon for two independent samples generated a rank sum of 91,50 for CCD-patients, and of 79,50 for the control group. The Z-value was 3,246, the p-value 0,005. “Fisher`s exact test” identified a p-value of 0,0003.

Conclusions

The rate of collagen I in the oral mucosa seems to be increased significantly in CCD. This could explain the typical thick and fibrotic consistency of the gingiva and could be one reason for the delayed or missing dentition.  相似文献   
30.
Close structural relationships between approved drugs and bioactive compounds were systematically assessed using matched molecular pairs. For structural analogs of drugs, target information was assembled from ChEMBL and compared to drug targets reported in DrugBank. For many drugs, multiple analogs were identified that were active against different targets. Some of these additional targets were closely related to known drug targets while others were not. Surprising discrepancies between reported drug targets and targets of close structural analogs were often observed. On one hand, the results suggest that hypotheses concerning alternative drug targets can often be formulated on the basis of close structural relationships to bioactive compounds that are easily detectable. It is conceivable that such obvious structure–target relationships are frequently not considered (or might be overlooked) when compounds are developed with a focus on a primary target and a few related (or undesired) ones. On the other hand, our findings also raise questions concerning database content and drug repositioning efforts.  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