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   2679篇
  免费   209篇
  国内免费   18篇
耳鼻咽喉   55篇
儿科学   104篇
妇产科学   65篇
基础医学   210篇
口腔科学   122篇
临床医学   309篇
内科学   470篇
皮肤病学   225篇
神经病学   147篇
特种医学   189篇
外科学   373篇
综合类   103篇
一般理论   1篇
预防医学   152篇
眼科学   80篇
药学   128篇
  1篇
中国医学   43篇
肿瘤学   129篇
  2023年   23篇
  2022年   20篇
  2021年   56篇
  2020年   57篇
  2019年   78篇
  2018年   103篇
  2017年   79篇
  2016年   74篇
  2015年   112篇
  2014年   114篇
  2013年   152篇
  2012年   175篇
  2011年   209篇
  2010年   124篇
  2009年   81篇
  2008年   124篇
  2007年   153篇
  2006年   111篇
  2005年   119篇
  2004年   113篇
  2003年   100篇
  2002年   115篇
  2001年   78篇
  2000年   63篇
  1999年   48篇
  1998年   48篇
  1997年   33篇
  1996年   38篇
  1995年   27篇
  1994年   26篇
  1993年   16篇
  1992年   16篇
  1991年   21篇
  1990年   10篇
  1989年   20篇
  1988年   25篇
  1987年   16篇
  1986年   20篇
  1985年   15篇
  1984年   13篇
  1983年   7篇
  1982年   11篇
  1980年   10篇
  1979年   6篇
  1978年   4篇
  1977年   5篇
  1976年   7篇
  1975年   5篇
  1970年   4篇
  1966年   4篇
排序方式: 共有2906条查询结果,搜索用时 78 毫秒
11.
Oral opportunistic infections developing secondary to human immunodeficiency virus (HIV) infection have been reported from the early days of the epidemic and have been classified by both the EC-Clearinghouse and the World Health Organisation (WHO). Among the fungal infections, oral candidiasis, presenting in African HIV-infected patients has been sporadically documented. We review the literature with respect to candidal carriage, oral candidiasis prevalence and the predictive value of oral candidiasis for a diagnosis of underlying HIV disease in African HIV-infected patients. The use of oral candidiasis as a marker of disease progression, the species of yeasts isolated from the oral cavity in Africa and the resistance of the yeasts to antifungal agents and treatment regimens are discussed. Orofacial lesions as manifestations of the systemic mycoses are rarely seen in isolation and few cases are reported in the literature from Africa. In spite of the high incidence of noma, tuberculosis, chronic osteomyelitis and syphilis in Africa, surprisingly there have been very few reported cases of the oral manifestations of these diseases in HIV-positive individuals. Orofacial disease in HIV-infected patients is associated with marked morbidity, which is compounded by malnutrition. The authors indicate specific research areas, initially directed at the most effective management strategies, which would complete data in this important area.  相似文献   
12.
Herein we report treatment for a 19-year-old female patient with severe osteoarthritis of the temporomandibular joint. The patient had severe open bite with a Class II molar relationship. She had limited mouth opening and pain. Clinical examination and magnetic resonance imaging revealed that she had anterior disc displacement without reduction. By splint therapy, limited mouth opening and pain was eliminated, but an anterior open bite developed after the treatment. By orthodontic treatment, an acceptable occlusion was achieved with a Class I molar relationship.  相似文献   
13.

Objective

The aim of this study was to evaluate the antibacterial activity of a composite resin modified by TiO2 and TiO2/Ag nanoparticles and their influence over different properties.

Methods

TiO2 and TiO2/Ag NPs were synthesized by polymeric precursor and microwave-assisted hydrothermal methods and then, characterized by different techniques. Direct contact test was performed using Filtek? Z350XT blended with 0.5; 1 and 2% (wt.) of NPs against Streptococcus mutans to determine the best concentration to the other tests. After that, the modified composite resin was tested against S. mutans 7-day biofilm (CFU/mL). Also, compressive and diametral tensile strength (n = 40), degree of conversion (n = 25) and surface roughness (n = 50) was performed. The data were analyzed by ANOVA and Tukey’s test for multiple comparison at 5% significance level.

Results

The direct contact test demonstrates that by increasing the nanoparticle content, the bacterial growth is significantly reduceed (p < 0.05). The inclusion of 2% of TiO2/Ag NPs significantly decreased (p < 0.05) the biofilm accumulation of S. mutans on the composite resin surface compared to the control Group. The TiO2 NPs treated with an organosilane increased compressive strength of composite resin (p < 0.05). Degree of conversion remained unchanged (p > 0.05) and the surface roughness increased with the NPs (p < 0.05), except for the TiO2 by polymeric precursor Group (p > 0.05).

Significance

The development of an antibacterial dental restorative material that hinder S. mutans biofilm without sacrificing the mechanical and physical properties is desirable in dental material science.  相似文献   
14.
15.

Purpose

Pure ureter cancers are rare and account for only 1–3 % of urothelial carcinomas with limited data. Nowadays, nephron-sparing methods are reserved mainly for imperative cases. This study intends to assess the oncologic outcome between segmental ureterectomy (SU) and radical nephroureterectomy (RNU) for pure ureteral urothelial carcinoma.

Methods

From July 2004 to August 2010, 112 patients at a single tertiary referral center were included. Perioperative data were obtained from our institutional database. Postoperative CT scan, cystoscopy, and contralateral renal echo were performed regularly for survey of disease recurrence.

Results

The mean length of follow-up was 43.8 and 48.3 months for the RNU and SU group, respectively. The bladder recurrences, local recurrences, distant metastasis, and cancer-specific survival rates showed no significant differences between RNU and SU (36.4 vs. 34.2 %, p = 0.83; 23.4 vs. 14.3 %, p = 0.27; and 16.9 vs. 8.6 %, p = 0.244, and 13.0 vs. 5.7 %, p = 0.249, respectively).

Conclusion

The study suggested that SU is not inferior to RNU for ureter cancer in oncologic outcomes and is less invasive and better nephron preservation.  相似文献   
16.

Objectives

To evaluate the temporal relationship between interval to biochemical recurrence (BCR) following radical prostatectomy (RP) and prostate cancer-specific mortality (PCSM).

Patients and methods

The study comprised of 2,116 men from the Victorian Radical Prostatectomy Register, a whole-of-population database of all RPs performed between 1995 and 2000 in Victoria, Australia. Follow-up prostate-specific antigen and death data were obtained via record linkage to pathology laboratories and the Victorian Registry of Births, Deaths and Marriages. Poisson regression models with PCSM as the outcome were fit to the data. Models included age at surgery, Gleason score and tumour stage as covariates.

Results

Median post-surgery and post-BCR follow-up was 10.3 and 7.5 years, respectively. 695 men (33 %) experienced BCR during follow-up, of which 82 % occurred within 5 years of RP; 66 men died from prostate cancer. Men with combined high Gleason sum (≥4 + 3) and extra-prostatic (≥pT3a) disease had substantially increased mortality rate with early BCR, while those experiencing BCR after a longer interval had significantly lower mortality. Men with combined low Gleason sum (≤3 + 4) and organ-confined disease (≤pT2c) risk disease were not at any substantial risk of death in this time frame regardless of timing of BCR following RP.

Conclusions

This study evaluates the temporal relationship between BCR and PCSM using a whole-of-population cohort of men treated with RP. Men with low-risk features of prostate cancer at time of RP have low mortality even if they experience early BCR. This subgroup may be counselled regarding their favourable long-term prognosis.  相似文献   
17.

Background

The aim of this study was to evaluate the presence of subclinical cardiovascular disease (CVD) and its relation to risk factors in pediatric patients with steroid-resistant nephrotic syndrome (NS).

Methods

Thirty-seven patients with normal renal function were compared with 22 healthy controls regarding the presence of subclinical CVD. Measurements included aortic pulse wave velocity (PWV), carotid intima media thickness (IMT), and left ventricular mass (LVM). Patients were additionally assessed for blood pressure (BP) pattern and the presence of hypertension by 24-h ambulatory blood pressure monitoring.

Results

Compared with the controls, patients had significantly higher mean aortic PWV-standard deviation scores (SDS), mean carotid IMT-SDS, and LVM index (p?<?0.001 for all). Increased aortic PWV was noted in 5 % of patients, increased carotid IMT in 22 %, and increased LVM index in 19 %. Five patients (14 %) were hypertensive, and mean BP indexes, SDS, and BP loads during nighttime were significantly higher than those during daytime (p?<?0.001 for all). Multivariate analysis revealed a significant relationship between PWV-SDS and ferritin (R 2?=?0.269, p?=?0.006) and between carotid IMT-SDS and proteinuria (R 2?=?0.141, p?=?0.022). The LVM index was independently associated only with higher body mass index SDS (R 2?=?0.317, p?<?0.001). In addition, six patients (16 %) had multiple abnormal subclinical CVD markers, and increased subclinical CVD risk was independently associated only with higher low-density lipoprotein cholesterol (R 2?=?0.292, p?=?0.044).

Conclusions

Based on these results, steroid-resistant NS children generally are at high risk of cardiovascular complications, but the increased risk is likely to be multifactorial.  相似文献   
18.
This study demonstrated the prevalence of Porcine circovirus type 2 (PCV2) among pig farms in Vietnam. Analyses of the genome, capsid protein and phylogeny classified all 30 Vietnamese PCV2 strains as the PCV2b genotype, belonging to the clusters of 1A, 1B, 1C and recombinant forms. Each viral genome was 1767 nucleotides long and shared 96.0–100% nucleotide sequence identity. The amino acid substitutions in the capsid protein of the Vietnamese PCV2 strains were in immunodominant regions, and the majority of strains (24/30) contained a lysine extension at the C‐terminus. Bayesian phylogeographic analysis revealed epidemic links of the PCV2 recombinant cluster within and among countries, which supports a circulating recombinant form of PCV2. Further analysis by the Jameson–Wolf antigenic index indicated antigenic alterations at important sites in the capsid protein (sites 131–133) among the recombinant cluster and the other clusters of PCV2b.  相似文献   
19.

Purpose

To introduce a new diagnostic parameter: the linear combination of apparent integrated backscatter and spectral centroid shift.

Methods

Ultrasonic backscatter measurements were performed at the calcanei of 1262 volunteers in vivo. The hip and spine bone mineral densities of the volunteers were measured using dual X-ray absorptiometry. The apparent integrated backscatter and spectral centroid shift were calculated. A new diagnostic parameter, i.e., the linear combination of apparent integrated backscatter and spectral centroid shift, was introduced and its correlation to bone mineral density was analyzed.

Results

The results show that the combination of apparent integrated backscatter and spectral centroid shift is significantly correlated to bone mineral density (R = 0.73–0.84, n = 1262, p < 0.05), and that this correlation is more significant than the correlation between the apparent integrated backscatter and bone mineral density or the correlation between spectral centroid shift and bone mineral density (R = 0.48–0.69, p < 0.05).

Conclusion

The combination of apparent integrated backscatter and spectral centroid shift can provide the complementary information of attenuation of the two parameters and predict more information about cancellous bone, and may be employed to assess cancellous bone status.
  相似文献   
20.
The aim of this study was to identify the effects of adding quercetin (Q) to Tris extender in order to identify levels of oxidative stress in bull sperm after freeze thawing. Ejaculates were collected via artificial vagina from Holstein bulls. Semen was divided into five tools and diluted to a final concentration of 15 × 106 spermatozoa/ml with the Tris extender containing Q (25, 50, 100 and 200 μg/ml) and no additive (control; C). All examples were equilibrated at 4°C during 4 hr then were loaded into 0.25‐ml straws and frozen using a controlled rate. Sperm motility and motility characteristics were determined using the computer‐assisted semen analyser. Sperm membrane integrity was assessed using the hypoosmotic swelling test. Sperm chromatin integrity was investigated using the single cell gel electrophoresis. Total antioxidant capacities were performed colorimetrically. Q supplementation used as an antioxidant did not produce better results in the proportion of sperm progressive and total motility, plasma membrane integrity and sperm abnormalities. Q supplementation exhibited the favourable tail length, tail DNA and tail moment. In conclusion, when whole parameters are considered, Q25 can be added to the Tris extender due to its positive effect on sperm DNA integrity and no adverse effect on the progressive and total motilities of sperm.  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