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   422588篇
  免费   29124篇
  国内免费   2857篇
耳鼻咽喉   5804篇
儿科学   9426篇
妇产科学   11307篇
基础医学   59854篇
口腔科学   12815篇
临床医学   36058篇
内科学   86325篇
皮肤病学   9127篇
神经病学   30729篇
特种医学   15343篇
外国民族医学   83篇
外科学   66426篇
综合类   10851篇
现状与发展   1篇
一般理论   93篇
预防医学   22000篇
眼科学   10098篇
药学   34504篇
  1篇
中国医学   2260篇
肿瘤学   31464篇
  2021年   3202篇
  2019年   3400篇
  2018年   5297篇
  2017年   3989篇
  2016年   4216篇
  2015年   4749篇
  2014年   6693篇
  2013年   8891篇
  2012年   12050篇
  2011年   12275篇
  2010年   7363篇
  2009年   6886篇
  2008年   11273篇
  2007年   12188篇
  2006年   12047篇
  2005年   11091篇
  2004年   10516篇
  2003年   10206篇
  2002年   9923篇
  2001年   29698篇
  2000年   30288篇
  1999年   24932篇
  1998年   5748篇
  1997年   4745篇
  1996年   4244篇
  1995年   3934篇
  1994年   3530篇
  1993年   3230篇
  1992年   17113篇
  1991年   15824篇
  1990年   15156篇
  1989年   14880篇
  1988年   13435篇
  1987年   12924篇
  1986年   11945篇
  1985年   11187篇
  1984年   7607篇
  1983年   6193篇
  1982年   3143篇
  1979年   6045篇
  1978年   3786篇
  1977年   3325篇
  1976年   2604篇
  1975年   2921篇
  1974年   3437篇
  1973年   3196篇
  1972年   3161篇
  1971年   3073篇
  1970年   2765篇
  1969年   2807篇
排序方式: 共有10000条查询结果,搜索用时 19 毫秒
1.
Background: Weight loss is frequently observed in pancreatic cancer patients. We aimed to study the prognostic impacts of weight loss early during chemotherapy.

Methods: A total of 72 patients of Chinese ethnicity with unresectable pancreatic cancer who underwent chemotherapy were reviewed. Critical weight loss (CWL) was defined as weight loss ≥ 5% within one month after treatment. The prognostic impact of weight loss and CWL were analyzed.

Results: 47 patients (65.3%) had weight loss after one month of treatment, with 14 (19.4%) suffering from CWL. Baseline characteristics were similar between patients with and without CWL. The median OS and Time-to-treatment-failure (TTF) of patients with CWL were shorter than those without CWL (OS: 4.8?months [CWL] versus [vs.] OS 7.1?months [No CWL]; TTF 1.6?months [CWL] vs. 3.2?months [No CWL]; both P?<?0.01). CWL was an independent adverse prognosticator for OS (Hazard Ratio [HR]?=?2.50; P?=?0.01) and TTF (HR = 2.71; P?<?0.01). Other independent prognosticators for OS were serum albumin <35?mg/dl and CA19-9?≥?1000?IU/ml, while CWL was the only independent prognosticator for TTF (HR 2.71 [95% CI 1.33–5.52]; P?<?0.01).

Conclusions: Development of CWL in early course of chemotherapy was associated with worse prognosis in Chinese patients with unresectable pancreatic cancers.  相似文献   

2.
In this paper, we use optimal parameter selection technique to develop two models involving single‐vendor–multiple‐buyer supply chain, which are called the dynamic independent optimization (DIO) model and the dynamic synchronized cycles (DSC) model, respectively. These models are, respectively, similar to the traditional static independent policy model and the traditional static synchronized cycle model, except that the deterministic demands of the buyers in the above two static models are now being replaced by the stochastic demands satisfying a Wiener process, which have more real‐life applications. Similar to the above static synchronized cycles model, the synchronization of the supply chain in our DSC model is also achieved by scheduling the delivery days of the buyers and coordinating them with the vendor's production cycle. Finding the optimal expected system costs of the DIO model and the DSC model involves solving optimal parameter selection problems governed by ordinary differential equations, whose final times are continuous decision variables and discrete decision variables, respectively. Computational methods have been developed for solving these problems. Numerical results show that the coordinated policy is better than the independent optimization policy, in terms of minimizing the expected system cost of the entire supply chain. Sensitivity analysis is performed to test the effect of changing the cost coefficients and the value on the performances of these models, where is the ratio of the total mean demand rate of all the buyers over the vendor's production rate.  相似文献   
3.

Objective

Helicobacter pylori infection is common among Asians. However, evidence in the recent years has demonstrated a decrease in the prevalence of H. pylori infection among children and adults worldwide. Our aim was to update its prevalence in symptomatic children in our locality in the recent 12?years and compared to the results of our previous review published in 2005.

Methods

A retrospective review was carried out between 2005 and 2017. All children who presented with dyspepsia or gastrointestinal bleeding and underwent oesophagogastroduodenoscopy with antral biopsy taken were included. Patient demographics, endoscopic, or histological diagnosis and the H. pylori status were recorded.

Main Results

A total of 602 patients were included. There was a statistically significant decreasing trend of H. pylori infection rate between 2005 and 2017 (p?=?0.003). The overall infection rate from this study was 12.8%, compared to 25.6% from our previous review. Overall failure of eradication with first-line antibiotic therapy has increased to 29.3% from 10% in our previous review.

Conclusion

There was a decrease in the prevalence of H. pylori infection among symptomatic children for the recent 12?years, comparing to our previous data from 2005. We hypothesize that the reduction in prevalence of H. pylori infection among adults and the decrease in the practice of sharing chopsticks during meals have led to a decrease in transmission of the bacteria among family members in Hong Kong. However, the failure of eradication with first line treatment was higher, possibly due to the increase in antibiotics usage and resistance.

Level of Evidence

III  相似文献   
4.

Background

Although it is known that women do not participate in trials as frequently as men, there are limited recent data examining how women recruitment has changed over time.

Methods

We conducted MEDLINE search using a validated strategy for randomized trials published in New England Journal of Medicine, Lancet, and Journal of the American Medical Association between 1986 and 2015, and included trials evaluating pharmacologic or nonpharmacologic therapies. We abstracted data on demographics, intervention type, clinical indication, and trial design characteristics, and examined their relationships with women enrollment.

Results

In total, 598 trials met inclusion criteria. Women enrollment increased significantly over time (21% between 1986 and 1990 to 33% between 2011 and 2015; Pfor trend < 0.001) and did not differ by journal or funding source. Women enrollment varied with clinical indication, comprising 37% for non–coronary artery disease vascular trials, 30% for coronary artery disease trials, 28% for heart failure trials, and 28% for arrhythmia trials (P < 0.001), which were all significantly lower than the expected proportion in disease populations (P < 0.001). Women enrollment varied with trial type (31%, 29%, and 26% for pharmacologic, device, and procedural trials, respectively; P = 0.001). These findings were corroborated using multivariable analysis. We found significant positive correlations between women enrolled, and mean age and total number of participants. Fewer women were enrolled in trials reporting statistically significant results than those who did not (P = 0.001).

Conclusions

Although enrollment of women has increased over time, it remains lower than the relative proportion in the disease population. Future studies should elucidate the reasons for persistent under-representation of women in clinical trials.  相似文献   
5.
<正>Norepinephrine (NE; also known as noradrenaline) is the body's primary adrenergic neurotransmitter which belongs to the catecholamine family. Norepinephrine has pharmacologic effects on theα1 (Suita et al.,2015),α2 (Schwartz,1997),β1,β2 andβ3(Tsukada et al., 2003) adrenoceptors. In the brain, norepinephrine increases arousal and alertness, promotes vigilance, enhances formation and retrieval of memory, and focuses attention. It also increases restlessness and anxiety. In the remainder of the body,  相似文献   
6.
7.

Objective

Although endovascular repair of abdominal aortic aneurysms (AAAs) has been demonstrated to have favorable outcomes, not all cohorts of patients with AAA fare equally well. Our goal was to investigate perioperative and 1-year outcomes in patients with end-stage renal disease (ESRD) on dialysis, who have traditionally fared worse after vascular interventions, to assess how ESRD affects outcomes in a large modern cohort of endovascular aneurysm repair (EVAR) patients.

Methods

The Vascular Quality Initiative database was queried for all patients undergoing EVAR from 2010 to 2017. ESRD patients were compared with patients not on dialysis. Propensity-matched scoring and multivariable analysis were used to isolate the effects of ESRD.

Results

Of 28,683 EVARs identified, there were 321 (1.12%) patients with ESRD on dialysis. Patients with ESRD had no difference in presenting AAA size (57.5 ± 12.7 mm vs 56.7 ± 17.2 mm; P = .44); however, they had more urgent/emergent repairs (20.6% vs 13.6%; P = .002) than those without ESRD. ESRD patients were more often younger, nonwhite, and nonobese and less likely to have commercial insurance (P < .05). ESRD patients more often had hypertension, coronary artery disease, congestive heart failure, previous lower extremity bypass, aneurysm repair, and carotid interventions (P < .05). There was no difference in the rate of concomitant procedures. Matching based on demographics, comorbidities, and operative details showed that ESRD patients had longer hospital length of stay (4.8 ± 9.4 days vs 4.1 ± 12.6 days; P = .026) and higher 30-day mortality (7% vs 2.4%; P < .001). There was no difference in cardiac, pulmonary, lower extremity, bowel, and stroke complications or return to the operating room. On multivariable analysis, ESRD was associated with 30-day mortality (odds ratio, 4.1; 95% confidence interval, 2.6-6.7; P < .001). Of the 24,750 elective EVARs, 1.04% had ESRD on dialysis. Matched data for elective EVAR show increased postoperative length of stay, hospital mortality, and 30-day mortality for ESRD patients on dialysis compared with those who are not. There was no association with postoperative myocardial infarction or pulmonary complications. At 1 year, patients with ESRD on dialysis had worse survival (78% vs 94%; P < .001), and ESRD was associated with higher mortality (hazard ratio, 3.3; 95% confidence interval, 2.5-4.2; P < .001).

Conclusions

Among patients undergoing EVAR, ESRD is independently associated with higher perioperative and 1-year mortality despite not being associated with higher postoperative complications. This should be taken into account during informed consent for EVAR and risk-benefit considerations in this high-risk population, particularly for elective repair.  相似文献   
8.

Background

The International Agency for Research on Cancer (IARC) has recently classified glyphosate as a Group 2A ‘probably carcinogenic to humans’. Due to this carcinogenic classification and resulting international debate, there is an increased demand for studies evaluating human health effects from glyphosate exposures. There is currently limited information on human exposures to glyphosate and a paucity of data regarding glyphosate's biological half-life in humans.

Objective

This study aims to estimate the human half-life of glyphosate from human urine samples collected from amenity horticulture workers using glyphosate based pesticide products.

Methods

Full void urine spot samples were collected over a period of approximately 24?h for eight work tasks involving seven workers. The elimination time and estimation of the half-life of glyphosate using three different measurement metrics: the unadjusted glyphosate concentrations, creatinine corrected concentrations and by using Urinary Excretion Rates (UER) (μg L?1, μmol/mol creatinine and UER μg L?1) was calculated by summary and linear interpolation using regression analysis.

Results

This study estimates the human biological half-life of glyphosate as approximately 5 ½, 10 and 7 ¼ hours for unadjusted samples, creatinine corrected concentrations and by using UER (μg L?1, μmol/mol creatinine, UER μg L?1), respectively. The approximated glyphosate half-life calculations seem to have less variability when using the UER compared to the other measuring metrics.

Conclusion

This study provides new information on the elimination rate of glyphosate and an approximate biological half-life range for humans. This information can help optimise the design of sampling strategies, as well as assisting in the interpretation of results for human biomonitoring studies involving this active ingredient. The data could also contribute to the development or refinement of Physiologically Based PharmacoKinetic (PBPK) models for glyphosate.  相似文献   
9.
10.
Abstract

Purpose: We examined underlying psychosocial processes of a behavioral treatment for urinary incontinence (UI) of prostate cancer survivors.

Design: Secondary analysis of data collected from a clinical trial.

Sample: Two hundred forty-four prostate cancer survivors who participated in a clinical trial of behavioral intervention to UI as intervention or control subjects.

Methods: The participants had a 3-month behavioral intervention or usual care and were followed up for an additional 3?months. They were assessed at baseline, 3, and 6?months. Latent growth curve models were performed to examine trajectories of each study variable and relationships among the variables.

Findings: Increasing self-efficacy and social support were significantly and independently associated with more reduction of urinary leakage frequency over time.

Implications for psychosocial oncology: Providing problem-solving skills and social support, including peer support, are essential for empowering patients to reduce UI.  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