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   5331篇
  免费   279篇
  国内免费   24篇
耳鼻咽喉   77篇
儿科学   138篇
妇产科学   82篇
基础医学   667篇
口腔科学   576篇
临床医学   409篇
内科学   1167篇
皮肤病学   105篇
神经病学   382篇
特种医学   120篇
外科学   591篇
综合类   22篇
预防医学   614篇
眼科学   90篇
药学   373篇
中国医学   31篇
肿瘤学   190篇
  2023年   54篇
  2022年   160篇
  2021年   238篇
  2020年   173篇
  2019年   189篇
  2018年   230篇
  2017年   154篇
  2016年   157篇
  2015年   217篇
  2014年   293篇
  2013年   285篇
  2012年   428篇
  2011年   520篇
  2010年   277篇
  2009年   169篇
  2008年   319篇
  2007年   320篇
  2006年   226篇
  2005年   243篇
  2004年   167篇
  2003年   133篇
  2002年   131篇
  2001年   85篇
  2000年   81篇
  1999年   63篇
  1998年   17篇
  1997年   13篇
  1996年   27篇
  1995年   12篇
  1994年   13篇
  1993年   10篇
  1992年   37篇
  1991年   31篇
  1990年   18篇
  1989年   16篇
  1988年   13篇
  1987年   8篇
  1986年   12篇
  1985年   17篇
  1984年   9篇
  1983年   11篇
  1982年   5篇
  1979年   4篇
  1978年   4篇
  1977年   4篇
  1976年   5篇
  1971年   5篇
  1969年   4篇
  1968年   3篇
  1967年   4篇
排序方式: 共有5634条查询结果,搜索用时 14 毫秒
41.
Recurrent herpes labialis is a worldwide life-long oral health problem that remains unsolved. It affects approximately one third of the world population and causes frequent pain and discomfort episodes, as well as social restriction due to its compromise of esthetic features. In addition, the available antiviral drugs have not been successful in completely eliminating the virus and its recurrence. Currently, different kinds of laser treatment and different protocols have been proposed for the management of recurrent herpes labialis. Therefore, the aim of the present article was to review the literature regarding the effects of laser irradiation on recurrent herpes labialis and to identify the indications and most successful clinical protocols. The literature was searched with the aim of identifying the effects on healing time, pain relief, duration of viral shedding, viral inactivation, and interval of recurrence. According to the literature, none of the laser treatment modalities is able to completely eliminate the virus and its recurrence. However, laser phototherapy appears to strongly decrease pain and the interval of recurrences without causing any side effects. Photodynamic therapy can be helpful in reducing viral titer in the vesicle phase, and high-power lasers may be useful to drain vesicles. The main advantages of the laser treatment appear to be the absence of side effects and drug interactions, which are especially helpful for older and immunocompromised patients. Although these results indicate a potential beneficial use for lasers in the management of recurrent herpes labialis, they are based on limited published clinical trials and case reports. The literature still lacks double-blind controlled clinical trials verifying these effects and such trials should be the focus of future research.  相似文献   
42.

Background

Although obesity has been associated with larger prostate volumes (PV), few studies have actually investigated whether obesity enhances PV growth, especially among men using 5α-reductase inhibitors.

Objective

To examine whether obesity is associated with enhanced PV growth measured by serial transrectal ultrasound (TRUS) measurements.

Design, setting, and participants

We conducted a secondary analysis of the REduction by DUtasteride of prostate Cancer Events (REDUCE) trial, which was originally aimed at cancer risk reduction among high-risk men with a single negative prestudy biopsy.

Intervention

Per-protocol randomization to placebo or dutasteride and mandatory TRUS-guided biopsies at 2 yr and 4 yr.

Outcome measurements and statistical analysis

Percentage change in PV at 2 yr and 4 yr from baseline. We tested its association with baseline body mass index (BMI) groups of <25, 25–29.9, and ≥30 kg/m2 using multivariable linear regression. Secondarily, we tested whether BMI was associated with the likelihood of having no PV reduction among men randomized to dutasteride using multivariable logistic regression.

Results and limitations

Of 8122 participants, we analyzed 71.8% and 54.5% with complete 2-yr and 4-yr PV data, respectively. In multivariable analysis, men on placebo with BMI ≥30 versus <25 kg/m2 had enhanced PV growth from baseline (at 2 yr: 17.0% vs 10.7%, p < 0.001; at 4 yr: 29.4% vs 20.1%; p = 0.001). Men on dutasteride with BMI ≥30 versus <25 kg/m2 had attenuated PV reduction from baseline (at 2 yr: −14.3% vs −18.5%; p = 0.002; at 4 yr: −13.2% vs −19.3%; p = 0.001) and higher likelihood of having no PV reduction (at 2 yr: odds ratio [OR]: 1.44; 95% confidence interval [CI], 1.08–1.93; p = 0.014; at 4 yr: OR: 1.62; 95% CI, 1.18–2.22; p = 0.003). We found no significant interactions between BMI and dutasteride on PV change at 2 yr and 4 yr (p interaction ≥0.36). No clinical outcomes or effects of weight change were assessed.

Conclusions

Obesity enhanced PV growth and attenuated PV reduction by dutasteride. The null interaction between obesity and dutasteride for PV change implies that the effect of obesity on dutasteride-treated men is likely a combination of dutasteride-driven PV reduction with obesity-driven PV growth rather than decreased dutasteride efficacy.

ClinicalTrials.gov identifier

NCT00056407.  相似文献   
43.
PURPOSE: Renal cell carcinoma is a tumor with unpredictable behavior and defining reliable prognostic factors would be extremely valuable in the clinical setting. Tumor stage, nuclear grade and tumor cell type are the main prognostic clinical parameters available. In this study we evaluated the role of microvascular involvement in the primary lesion for predicting tumor behavior in patients with low stage clinical disease. MATERIALS AND METHODS: A total of 95 patients with clinically localized renal cell carcinoma (stages T1-T2 Nx M0) underwent radical nephrectomy and/or nephron sparing surgery, and were followed for a median of 45 months. The impact of microvascular tumor invasion on disease progression and its correlation with known pathological outcomes (tumor size, nuclear grade and cell type) were studied. RESULTS: Microvascular tumor invasion was observed in 24 patients (25%), of whom 50% had disease recurrence. Of the 71 patients without microvascular invasion only 4 (6%) showed tumor recurrence. When microvascular invasion was correlated with other histological parameters, a significant statistical association was noted with tumor diameter, perirenal fat invasion, macroscopic extension to the renal vein, nuclear grade, lymph node metastasis and sarcomatous elements in the tumor. Multivariate analysis showed that microvascular invasion and the involvement of regional lymph nodes were independent predictors of disease recurrence. Concerning cancer specific survival, microvascular invasion and perirenal fat infiltration were the only factors related to death. CONCLUSIONS: Microvascular invasion is an independent and relevant clinical prognostic parameter for low clinical stage renal cell carcinoma.  相似文献   
44.

Background

Findings of studies on the association between androgens and prostate cancer (PCa) are mixed. Androgens may affect prostate-specific antigen (PSA) levels, thereby influencing biopsy recommendations. Also, androgens may stimulate prostate growth at very low levels with no additional effects at higher levels (saturation model).

Objective

To test whether androgens were associated with PCa risk in the placebo arm of a prospective study in which biopsies were performed regardless of PSA level.

Design, setting, and participants

Of 8122 men in the Reduction by Dutasteride of Prostate Cancer Events (REDUCE) trial, 4073 men (50.1%) received placebo. Key entry criteria were PSA 2.5–10 ng/ml and one prior negative biopsy.

Intervention

Per-protocol biopsies at 2 and 4 yr; for-cause biopsies at physician discretion.

Outcome measurements and statistical analysis

Multivariable logistic regression was used to test the association between baseline log-transformed testosterone and dihydrotestosterone (DHT) levels and the risk of detecting either PCa or low-grade PCa (Gleason score <6) compared with high-grade PCa (Gleason score >7). In secondary analysis, we stratified the analysis by low baseline androgen levels (testosterone <10 nmol/l; DHT <0.76 nmol/l) compared with normal baseline androgen levels.

Results and limitations

Of 4073 men, 3255 (79.9%) had at least one biopsy after randomization and were analyzed. Androgen levels tested continuously or by quintiles were generally unrelated to PCa detection or grade. PCa detection was similar among men with low compared with normal baseline testosterone levels (25.5% and 25.1%; p = 0.831). In secondary analysis, higher testosterone levels at baseline were associated with higher PCa detection (odds ratio: 1.23; 95% confidence interval, 1.06–1.43; p = 0.006) only if men had low baseline testosterone (<10 nmol/l). For men with normal baseline testosterone (≥10 nmol/l), higher testosterone levels at baseline were unrelated to PCa risk (p = 0.33). No association was found for DHT and PCa (all p > 0.85).

Conclusions

Baseline serum testosterone and DHT levels were unrelated to PCa detection or grade. Our findings of the lowest testosterone levels being associated with the lowest PCa risk with no further changes with higher testosterone support a saturation model but must be confirmed in future studies using an a priori defined hypothesis.

ClinicalTrials.gov identifier

NCT00056407.  相似文献   
45.
46.
OBJECTIVE: The purpose of this study was to analyze the behavior of the mitral valve ring and the left ventricle in dilated cardiomyopathy. METHODS: We analyzed 68 fixed adult human hearts, divided into 48 hearts with dilated cardiomyopathy of ischemic or idiopathic origin and 20 hearts free of pathologic heart conditions. Digital images of the mitral ring perimeter, attachment of the anterior and posterior leaflets, and fibrous and muscular portions were collected. We also measured the internal perimeter of the left ventricle, the distance from the septum to the anterior and posterior papillary muscles, the distance between the papillary muscles, and the extension of interventricular septum. RESULTS: The analysis of the results showed proportional distribution of the ring's fibrous portion (r2 = 0.98) and muscular portion (r2 = 0.99) according to the degree of mitral valve dilation. Linear regression revealed that the perimeters of anterior and posterior leaflet attachments (r2 = 0.96 and r2 = 0.98, respectively) also had a proportional relation. We did not observe proportionality between the degree of dilation of the mitral ring and the left ventricle. It was observed that dilation of the left ventricle takes place globally in its segments. CONCLUSION: Differently from what was thought, in ischemic or idiopathic dilated cardiomyopathy, dilation of mitral ring is proportional and does not exclusively affect the posterior portion. The degree of left ventricular dilation does not determine the degree of dilation of the mitral ring because they are independent processes. These observations shed new light on the techniques used to correct mitral valve insufficiency in dilated cardiomyopathy.  相似文献   
47.

Background

Prostate biopsy and postbiopsy complications represent important risks of prostate-specific antigen (PSA) screening. Although landmark randomized trials and updated guidelines have challenged routine PSA screening, it is unclear whether these publications have affected rates of biopsy or postbiopsy complications.

Objective

To evaluate whether publication of the 2008 and 2012 US Preventive Services Task Force (USPSTF) recommendations, the 2009 European Randomized Study of Screening for Prostate Cancer and the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial, or the 2013 American Urological Association (AUA) guidelines was associated with changes in rates of biopsy or postbiopsy complications, and to identify predictors of postbiopsy complications.

Design, setting, and participants

This quasiexperimental study used administrative claims of 5 279 315 commercially insured US men aged ≥40 yr from 2005 to 2014, of whom 104 584 underwent biopsy.

Interventions

Publications on PSA screening.

Outcome measurements and statistical analysis

Interrupted time-series analysis was used to evaluate the association of publications with rates of biopsy and 30-d complications. Logistic regression was performed to identify predictors of complications.

Results and limitations

From 2005 to 2014, biopsy rates fell 33% from 64.1 to 42.8 per 100 000 person-months, with immediate reductions following the 2008 USPSTF recommendations (?10.1; 95% confidence interval [CI], ?17.1 to ?3.0; p < 0.001), 2012 USPSTF recommendations (?13.8; 95% CI, ?21.0 to ?6.7; p < 0 .001), and 2013 AUA guidelines (?8.8; 95% CI, ?16.7 to ?0.92; p = 0.03). Concurrently, complication rates decreased 10% from 8.7 to 7.8 per 100 000 person-months, with a reduction following the 2012 USPSTF recommendations (?2.5; 95% CI, ?4.5 to ?0.45; p = 0.02). However, the proportion of men undergoing biopsy who experienced complications increased from 14% to 18%, driven by nonsepsis infectious complications (p < 0.001). Predictors of complications included prior fluoroquinolone use (odds ratio [OR]: 1.27; 95% CI, 1.22–1.32; p < 0.001), anticoagulant use (OR: 1.14; 95% CI, 1.04–1.25; p = 0.004), and age ≥70 yr (OR: 1.25; 95% CI, 1.15–1.36; p < 0.001). Limitations included the retrospective design.

Conclusions

Although there has been an absolute reduction in rates of biopsy and 30-d complications, the relative morbidity of biopsy continues to increase. These observations suggest a need to reduce the morbidity of biopsy.

Patient summary

Absolute rates of biopsy and postbiopsy complications have decreased following landmark publications about prostate-specific antigen screening; however, the relative morbidity of biopsy continues to increase.  相似文献   
48.

Introduction and hypothesis

The aim of this study was to evaluate the correlations between the POP-Q Bp point and the perineal body (Pb) and genital hiatus (Gh) measurements and constipation, anal incontinence, severity of symptoms and quality of life.

Methods

The patients were distributed into two groups according to the posterior vaginal wall Bp point: one group with Bp ≤?1 (without posterior vaginal wall prolapse, control group) and the other group with Bp ≥0 (with posterior vaginal wall prolapse, case group). Demographic data, defecatory dysfunction and SF-36 scores were compared between the groups. Correlations between severity of posterior prolapse (Bp, Gh, Pb and Gh?+?Pb) and severity of bowel symptoms were also calculated.

Results

A total of 613 women were evaluated, of whom 174 were included, 69 (39.7%) in the control group and 105 (60.3%) in the case group. The groups were similar in terms of anal incontinence, fecal urgency and/or constipation. There was no correlation between the severity of constipation and anal incontinence according to the Wexner score, and the severity of posterior vaginal wall prolapse measured in terms of point Bp. There were, however, statistically significant differences in Pb, Gh and Gh?+?Pb between the groups. The Pb and Gh?+?Pb measurements were positively correlated with symptoms of constipation, as well as with the scores of some SF-36 domains, but were not correlated with anal incontinence.

Conclusions

These results suggest that the severity of posterior vaginal wall prolapse is not correlated with constipation or anal incontinence, but Pb and Gh?+?Pb measurements are correlated with constipation and SF-36 scores.
  相似文献   
49.

Objectives

To evaluate the influence of bilateral or left sympathectomy on left ventricular remodeling and function after myocardial infarction in rats.

Methods

Myocardial infarction was induced in rats by ligation of the left anterior descending coronary. Seven days later, rats were divided into 4 groups: the myocardial infarction, myocardial infarction with left sympathectomy, myocardial infarction with bilateral sympathectomy, and sham groups. After 8 weeks, left ventricular function was evaluated with the use of a pressure-volume conductance catheter under steady-state conditions and pharmacological stress. Infarct size and extracellular matrix fibrosis were evaluated, and cardiac matrix metalloproteinases and myocardial inflammatory markers were analyzed.

Results

The myocardial infarction and left sympathectomy group had an increased end diastolic volume, whereas the bilateral sympathectomy group had a mean end-diastolic volume similar to that of the sham group (P < .002). Significant reduction in ejection fraction was observed in the myocardial infarction and left sympathectomy group, whereas it was preserved after bilateral sympathectomy (P < .001). In response to dobutamine, left ventricular contractility increased in sham rats, rising stroke work, cardiac output, systolic volume, end-diastolic volume, ejection fraction, and dP/dt max. Only bilateral sympathectomy rats had significant increases in ejection fraction (P < .001) with dobutamine. Fibrotic tissue and matrix metalloproteinase expression decreased in the bilateral sympathectomy group compared to that in the myocardial infarction group (P < .001) and was associated with left ventricular wall thickness maintenance and better apoptotic markers in noninfarcted myocardium.

Conclusions

Bilateral sympathectomy effectively attenuated left ventricular remodeling and preserved systolic function after myocardial infarction induction in rats.  相似文献   
50.
Even though very precise at describing pelvic organ position, our criticism to the Pelvic Organ Prolapse Quantification (POP-Q) system is its limited ability to quantify the prolapse itself, since it still classifies prolapse into four stages, almost the same way as Baden and Walker (Clin Obstet Gynecol 15(4):1070-1072, 1972) did in 1972. As a result, the same grade can include a wide prolapse intensity range. The objective of this study was to assess inter-observer reliability in the Pelvic Organ Prolapse Quantification Index (POP-Q-I; Lemos et al., Int Urogynecol J 18(6):609-611, 2007) on a prospective randomized trial. Fifty consecutive women were prospectively examined by two members of the urogynecology staff, blinded to each other's results. Spearman's rank correlation was used to assess inter-observer reliability. Excellent correlation coefficients were observed, with an overall coefficient of 96.5% (CI: 0.889-1.042; p < 0.0001). The POP-Q-I is a method that makes POP research more efficient by directly measuring prolapse as a continuous variable, which is statistically more powerful than the categorical variables proposed by the POP-Q system. This study suggests that the POP-Q-I is applicable to clinical POP research.  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