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   4354篇
  免费   259篇
  国内免费   6篇
耳鼻咽喉   41篇
儿科学   221篇
妇产科学   93篇
基础医学   568篇
口腔科学   307篇
临床医学   301篇
内科学   635篇
皮肤病学   89篇
神经病学   200篇
特种医学   96篇
外科学   764篇
综合类   71篇
一般理论   4篇
预防医学   196篇
眼科学   132篇
药学   503篇
  1篇
中国医学   44篇
肿瘤学   353篇
  2023年   40篇
  2022年   109篇
  2021年   172篇
  2020年   110篇
  2019年   128篇
  2018年   178篇
  2017年   131篇
  2016年   168篇
  2015年   149篇
  2014年   210篇
  2013年   268篇
  2012年   413篇
  2011年   401篇
  2010年   206篇
  2009年   177篇
  2008年   228篇
  2007年   219篇
  2006年   163篇
  2005年   127篇
  2004年   121篇
  2003年   89篇
  2002年   85篇
  2001年   61篇
  2000年   45篇
  1999年   44篇
  1998年   19篇
  1997年   11篇
  1996年   16篇
  1995年   14篇
  1992年   44篇
  1991年   37篇
  1990年   34篇
  1989年   41篇
  1988年   23篇
  1987年   36篇
  1986年   24篇
  1985年   20篇
  1984年   22篇
  1983年   23篇
  1981年   15篇
  1980年   10篇
  1979年   15篇
  1977年   15篇
  1976年   14篇
  1975年   14篇
  1974年   24篇
  1973年   13篇
  1972年   11篇
  1970年   9篇
  1967年   9篇
排序方式: 共有4619条查询结果,搜索用时 13 毫秒
81.
Cloned DNA-B components, belonging to the bipartite begomoviruses Indian cassava mosaic virus (ICMV) and Sri Lankan cassava mosaic virus (SLCMV), family Geminiviridae, when co-inoculated along with previously cloned DNA-A components of the respective viruses onto the experimental host Nicotiana benthamiana, generated defective DNAs (def-DNA) ranging in size from 549 to 1555 nucleotides. All the cloned def-DNAs contained the common region (CR) as well as portions of either DNA-A or DNA-B and, in a few cases, both DNA-A and DNA-B, representing recombinant products, the junction points of which correspond to repeats of 2-11 bases found in the parental molecules. The DNA-B-derived def-DNAs were, in some cases, associated with a decrease in levels of DNA-B, with a concomitant change in the symptoms from downward leaf curling in the older leaves to upward leaf-rolling in newly emerging leaves, more typical of monopartite begomoviruses.  相似文献   
82.
The present study aimed at formulating and optimizing natamycin (NT)-loaded polyethylene glycosylated nano-lipid carriers (NT-PEG-NLCs) using Box-Behnken design and investigating their potential in ocular applications. Response surface methodology computations and plots for optimization were performed using Design-Expert® software to obtain optimum values for response variables based on the criteria of desirability. Optimized NT-PEG-NLCs had predicted values for the dependent variables which are not significantly different from the experimental values. NT-PEG-NLCs were characterized for their physicochemical parameters; NT's rate of permeation and flux across rabbit cornea was evaluated, in vitro, and ocular tissue distribution was assessed in rabbits, in vivo. NT-PEG-NLCs were found to have optimum particle size (<300 nm), narrow polydispersity index, and high NT entrapment and NT content. In vitro transcorneal permeability and flux of NT from NT-PEG-NLCs was significantly higher than that of Natacyn®. NT-PEG-NLC (0.3%) showed improved delivery of NT across the intact cornea and provided concentrations statistically similar to the marketed suspension (5%) in inner ocular tissues, in vivo, indicating that it could be a potential alternative to the conventional suspension during the course of fungal keratitis therapy.  相似文献   
83.
84.
International Urology and Nephrology - Non-traumatic obliterative bulbar urethral stricture with residual urethral lumen below 3&nbsp;Fr is a challenging surgical scenario for reconstructive...  相似文献   
85.
European Journal of Orthopaedic Surgery & Traumatology - The safety and efficacy of tranexamic acid (TXA) in reducing blood loss after total joint arthroplasty and spinal fusion surgery has...  相似文献   
86.
87.
88.

Background

For breast-conserving surgery, the method of margin assessment that most frequently achieves negative margins without increasing the volume of tissue excised is uncertain. We examined our institutional experience with three different margin assessment methods used by six experienced breast surgeons.

Methods

Patients undergoing breast-conserving surgery for invasive carcinoma during July to December of a representative year during which each method was performed (perpendicular, 2003; tangential, 2004; cavity shave, 2011) were included. The effect of margin method on the positive margin rate at first excision and the total volume excised to achieve negative margins were evaluated by multivariable analysis, by surgeon, and by tumor size and presence of extensive intraductal component (EIC).

Results

A total of 555 patients were identified, as follows: perpendicular, 140; tangential, 124; and cavity shave, 291. The tangential method had a higher rate of positive margins at first excision than the perpendicular and cavity-shave methods (49, 15, 11 %, respectively; p < 0.0001). Median volumes to achieve negative margins were similar (55 ml perpendicular; 64 ml tangential; 62 ml cavity shave; p = 0.24). Four of six surgeons had the lowest rate of positive margins with the cavity-shave method, which was significant when compared to the tangential method (p < 0.0001) but not the perpendicular method (p = 0.37). The volume excised by the three methods varied by surgeon (p < 0.0001). The perpendicular method was optimal for T1 tumors without EIC; the cavity-shave method tended to be superior for T2–T3 tumors and/or EIC.

Conclusions

Although the cavity-shave method may decrease the rates of positive margins, its effect on volume is variable among surgeons and may result in an increase in the total volume excised for some surgeons and for small tumors without EIC.  相似文献   
89.

Introduction

For women with ductal carcinoma in situ (DCIS) undergoing breast-conserving surgery (BCS), the benefit of magnetic resonance imaging (MRI) remains unknown. Here we examine the relationship of MRI and locoregional recurrence (LRR) and contralateral breast cancer (CBC) for DCIS treated with BCS, with and without radiotherapy (RT).

Methods

A total of 2,321 women underwent BCS for DCIS from 1997 to 2010. All underwent mammography, and 596 (26 %) also underwent perioperative MRI; 904 women (39 %) did not receive RT, and 1,391 (61 %) did. Median follow-up was 59 months, and 548 women were followed for ≥8 years. The relationship between MRI and LRR was examined using multivariable analysis.

Results

There were 184 LRR events; 5- and 8-year LRR rates were 8.5 and 14.6 % (MRI), respectively, and 7.2 and 10.2 % (no-MRI), respectively (p = 0.52). LRR was significantly associated with age, menopausal status, margin status, RT, and endocrine therapy. After controlling for these variables and family history, presentation, number of excisions, and time period of surgery, there remained no trend toward association of MRI and lower LRR [hazard ratio (HR) 1.18, 95 % confidence interval (CI) 0.79–1.78, p = 0.42]. Restriction of analysis to the no-RT subgroup showed no association of MRI with lower LRR rates (HR 1.36, 95 % CI 0.78–2.39, p = 0.28). No difference in 5- or 8-year rates of CBC was seen between the MRI (3.5 and 3.5 %) and no-MRI (3.5 and 5.1 %) groups (p = 0.86).

Conclusions

We observed no association between perioperative MRI and lower LRR or CBC rates in patients with DCIS, with or without RT. In the absence of evidence that MRI improves outcomes, the routine perioperative use of MRI for DCIS should be questioned.  相似文献   
90.
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