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   126520篇
  免费   9886篇
  国内免费   4972篇
耳鼻咽喉   1759篇
儿科学   1509篇
妇产科学   1550篇
基础医学   18152篇
口腔科学   2638篇
临床医学   12958篇
内科学   20139篇
皮肤病学   2995篇
神经病学   7430篇
特种医学   6262篇
外国民族医学   21篇
外科学   14596篇
综合类   12220篇
现状与发展   30篇
一般理论   22篇
预防医学   7683篇
眼科学   3417篇
药学   12887篇
  66篇
中国医学   4458篇
肿瘤学   10586篇
  2024年   163篇
  2023年   1098篇
  2022年   2919篇
  2021年   5159篇
  2020年   3263篇
  2019年   3321篇
  2018年   3866篇
  2017年   3371篇
  2016年   3898篇
  2015年   5783篇
  2014年   7080篇
  2013年   7401篇
  2012年   11062篇
  2011年   11020篇
  2010年   6923篇
  2009年   6012篇
  2008年   7970篇
  2007年   7405篇
  2006年   6752篇
  2005年   6007篇
  2004年   4787篇
  2003年   4526篇
  2002年   3779篇
  2001年   3011篇
  2000年   2631篇
  1999年   2134篇
  1998年   1145篇
  1997年   932篇
  1996年   804篇
  1995年   711篇
  1994年   661篇
  1993年   471篇
  1992年   700篇
  1991年   657篇
  1990年   567篇
  1989年   517篇
  1988年   418篇
  1987年   428篇
  1986年   317篇
  1985年   260篇
  1984年   174篇
  1983年   150篇
  1982年   93篇
  1981年   85篇
  1980年   68篇
  1979年   97篇
  1978年   74篇
  1975年   57篇
  1974年   64篇
  1973年   61篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.

Objective

The advantage of arteriovenous fistulas (AVFs) in older patients requiring dialysis is controversial. We reviewed our vascular access experience in patients ≥70 years of age (older group) compared with younger patients.

Methods

We analyzed consecutive patients who underwent access surgery between 2013 and 2016. Primary success (PS) and primary patency (PP) data were analyzed between the older and younger groups before and after propensity score matching of the patients' characteristics and access composition. PS was defined as the achievement of access function that was amenable to two sessions of successful cannulation without early occlusion or maturation failure requiring revision. PP was defined as the time with uninterrupted patency without intervention.

Results

A total of 594 consecutive accesses were created among 563 patients, of whom 119 were allocated into each group after propensity score matching. In the whole cohort, 193 accesses (32.5%) were performed in older patients. AVFs were performed in 130 (67.4%) older patients and 293 (73.1%) younger patients. Regarding AVFs, the PS rate (83.6% in the older group vs 94.3% in the younger group; P = .001) and the overall PP at 6 and 12 months (73.1% and 57.1%, respectively, in the older group vs 86.7% and 77.7%, respectively, in the younger group; P = .009) were lower in the older group than in the younger group. However, no differences were found in the PS and PP rates for arteriovenous grafts between groups. Regarding the AVF location, the PS rate for forearm AVFs was significantly lower in the older group than in the younger group (76% vs 93%; P < .001); however, the PS rate of the upper arm was not different between the groups (94% vs 97%; P = .425). In the patients with PS, the PP rate of AVFs was similar between the two groups. In the older group with forearm AVFs, the median diameter of the radial artery was larger in the patients with PS than in the patients without PS (2.20 mm with PS vs 2.00 mm without PS; P = .008). The propensity score matching results demonstrated similar trends for the whole cohort, with lower PS (P = .042) and PP rates (P = .023) for AVF in the older group.

Conclusions

The outcomes after AVF were poorer in the older group than in the younger group, which was primarily due to unsatisfactory outcomes in patients with forearm AVFs. Thus, stricter criteria, especially regarding the radial artery diameter, should be applied for forearm AVFs in older patients, and additional research is necessary to delineate the risk factors for primary failure.  相似文献   
32.
33.
Mammary carcinoma (MC) is one of most common malignancy in women, and ring finger protein 2 (RNF2) possesses various roles in vast human tumors. In MC tissues as well as in cell lines RNF2 exhibited high expression, had significant association with tumor size, lymph node status, TNM stage, patients’ poor survival, and promoted cell proliferation, colony formation, cell migration and invasion of MC cell lines which was mediated by downregulation of E-cadherin protein. These data reveal that RNF2 protein plays a vital role in the development of MC and may be a potential therapy target of MC.  相似文献   
34.
35.
A typical time series in functional magnetic resonance imaging (fMRI) exhibits autocorrelation, that is, the samples of the time series are dependent. In addition, temporal filtering, one of the crucial steps in preprocessing of functional magnetic resonance images, induces its own autocorrelation. While performing connectivity analysis in fMRI, the impact of the autocorrelation is largely ignored. Recently, autocorrelation has been addressed by variance correction approaches, which are sensitive to the sampling rate. In this article, we aim to investigate the impact of the sampling rate on the variance correction approaches. Toward this end, we first derived a generalized expression for the variance of the sample Pearson correlation coefficient (SPCC) in terms of the sampling rate and the filter cutoff frequency, in addition to the autocorrelation and cross‐covariance functions of the time series. Through simulations, we illustrated the importance of the variance correction for a fixed sampling rate. Using the real resting state fMRI data sets, we demonstrated that the data sets with higher sampling rates were more prone to false positives, in agreement with the existing empirical reports. We further demonstrated with single subject results that for the data sets with higher sampling rates, the variance correction strategy restored the integrity of true connectivity.  相似文献   
36.
37.
38.
39.
40.
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