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   1067篇
  免费   116篇
  国内免费   28篇
耳鼻咽喉   3篇
儿科学   8篇
妇产科学   18篇
基础医学   99篇
口腔科学   24篇
临床医学   62篇
内科学   145篇
皮肤病学   75篇
神经病学   27篇
特种医学   95篇
外科学   31篇
综合类   109篇
预防医学   168篇
眼科学   14篇
药学   153篇
中国医学   134篇
肿瘤学   46篇
  2023年   14篇
  2022年   42篇
  2021年   54篇
  2020年   35篇
  2019年   48篇
  2018年   38篇
  2017年   51篇
  2016年   44篇
  2015年   36篇
  2014年   57篇
  2013年   91篇
  2012年   51篇
  2011年   64篇
  2010年   58篇
  2009年   60篇
  2008年   48篇
  2007年   56篇
  2006年   51篇
  2005年   51篇
  2004年   24篇
  2003年   33篇
  2002年   29篇
  2001年   18篇
  2000年   11篇
  1999年   11篇
  1998年   16篇
  1997年   17篇
  1996年   9篇
  1995年   11篇
  1994年   9篇
  1993年   7篇
  1992年   11篇
  1991年   6篇
  1990年   7篇
  1989年   4篇
  1988年   3篇
  1987年   7篇
  1986年   5篇
  1985年   4篇
  1984年   6篇
  1983年   2篇
  1982年   3篇
  1979年   1篇
  1978年   2篇
  1977年   3篇
  1975年   2篇
  1973年   1篇
排序方式: 共有1211条查询结果,搜索用时 31 毫秒
21.
22.
23.

Objective

To document the demographic changes in new HIV diagnoses at the Royal Free Hospital, London, UK, between 1994 and 2000.

Design

Retrospective case note review.

Methods

Data were extracted from the Royal Free HIV database identifying new diagnoses for 1994, 1997 and 2000. All case notes were reviewed and patients were included if they had their first positive HIV test at the Royal Free Hospital, or if they first tested positive elsewhere and attended the Royal Free HIV unit for their initial HIV care. Data extracted included sex, ethnicity, age, risk factor(s) for HIV, reason for test, clinical stage of disease, CD4 count and HIV RNA viral load at diagnosis.

Results

One hundred and forty‐four patients were identified for 1994, 136 for 1997 and 110 for 2000. Over this time period the proportion of white patients dropped from 72% (n = 104) to 48% (n = 53), P= 0.0001, whilst the proportion of black Africans rose from 24% (n = 34) to 45% (n = 49), P= 0.0004. The median CD4 count at diagnosis of the white cohort was 475 cells/µL in 1994 and 286/µL in 2000, P= 0.005, whilst in the black African patients it was 240/µL and 230/µL for the same years.

Conclusions

There has been a reduction in new HIV diagnoses among the white population and a rise in the black Africans at this centre between 1994 and 2000. The clinical and immunological parameters of HIV disease have worsened over this time period for the white group, but have remained stable in the black Africans.
  相似文献   
24.
The present study was undertaken to investigate the food–drug interaction of carbamazepine (CBZ). Common fruit juices [grapefruit juice (GFJ), lime juice (LJ)], known to inhibit the enzyme cytochrome P450 3A4 (CYP3A4), and some widely consumed beverages [milk (M), black tea (BT)] were involved in this study in the presence of CBZ, as might happen during clinical therapy. The effects of the beverages on the pharmacokinetics and drug-induced toxicity of CBZ was observed after concomitant administration for a period of 28 days. Accordingly, the influence of altered bioavailability of CBZ on its antiepileptic activity was investigated. A significant shift in the Cmax as well as Tmax of CBZ was observed in the presence of LJ and GFJ. This increase in bioavailability significantly enhanced hepatotoxicity and delayed the onset of tremor and piloerection against pentylene tetrazole (PTZ)-induced seizure in experimental animals. However, increased toxicity of CBZ was found to be absent with BT. Thus, from our observation, LJ or GFJ in the presence of CBZ significantly increased the bioavailability of CBZ, which might lead to increased toxicity and antiepileptic activity of the drug.  相似文献   
25.
Rationale:Acute esophageal necrosis (AEN) is a rare syndrome with characteristic endoscopic and pathologic findings. It usually results from a combination of tissue hypoperfusion, impaired local defense barriers, and massive reflux of gastric contents. We report a case of AEN after a kidney transplant.Patient concerns:A 53-year-old man with hypertension and end-stage renal disease presented with abdominal pain and a single episode of hematemesis 14 days after kidney transplantation.Diagnosis:Upper endoscopy revealed circumferential black coloration in the mid to lower esophageal mucosa. Esophageal biopsy showed ulcer, and immunostains were negative for viral etiology.Interventions:Conservative management was done with total parenteral nutrition and proton pump inhibitor.Outcomes:The patient experienced no further episodes of hematemesis or abdominal pain and follow-up endoscopy showed remarkable changes from the black mucosa to a red friable mucosa with whitish exudates.Lessons:In the case, AEN occurred in the setting of normal blood pressure after major surgery despite the absence of preceding factors such as hypotension and infections. The possibility of AEN should be considered in patients with solid organ transplantation who present with abdominal pain, dysphagia, and hematemesis.  相似文献   
26.
27.
《Connective tissue research》2013,54(3-4):303-318
Parietal yolk sacs isolated from 14.5-day rat embryos and incubated in vitro with either [14C]proline, [3H]mannose or 3H-labeled amino acid mixture synthesized and secreted basement membrane collagenous and noncollagenous glycoprotein components with relative molecular weights of 350,000 (350K), 220,000 (220K), 185,000 (185K), 175,000 (175K) and 150,000 (150K). The 185K and 175K components appeared to be similar to the pro-α1(IV) and pro-α2(IV) chains, respectively, which have been isolated from other sources. These components were completely susceptible to bacterial collagenase, but were only partially susceptible to α-chymotrypsin digestion. The 350K and 220K components appeared to be similar to subunits of laminin (or PYS A and PYS B, respectively) which have been characterized by others, while the 150K component may be similar to entactin (or PYS C). These components were completely resistant to bacterial collagenase and completely susceptible to α-chymotrypsin digestion. In addition, the basement membrane of the parietal yolk sac (Reichert's membrane) stained intensely with antibodies directed against either rat laminin or mouse basement membrane procollagen. The results of these experiments suggest that the 14.5-day rat embryo parietal yolk sac is a useful system for studying the structure, biosynthesis and deposition of basement membrane components.  相似文献   
28.
The distribution of cone photoreceptor subtypes (important for color vision and vision quality) varies widely in different carnivore species, but there have been limited studies on bear (ursid) cone distribution. A previous behavioral study suggests that American black bears (Ursus americanus) are dichromatic, indicating that they possess two cone subtypes, although the retinal distribution of cones is unknown. The purpose of this study was to examine the subtype and topography of cones in American black bear retinas to further predict the nature of their color vision and image resolution. We studied 10 eyes from seven individual legally hunted black bears in northeastern North Carolina. Cryosections and retinal wholemounts were labeled using antibodies targeting two cone opsin subtypes: long/medium (L/M) wavelength sensitive and short (S) wavelength sensitive. Cones in fluorescent microscopy images were counted and density maps were created for retinal wholemounts. The black bear retina contains both cone subtypes and L/M cones outnumber S cones by at least 3:1, a finding confirmed in retinal frozen sections. There are higher concentrations of S cones present than typically seen in other carnivores with some evidence for co-expression of L/M and S cones. A cone-dense area centralis is present dorsotemporal to the optic nerve, similar to other carnivores. These results confirm that American black bears are predicted to have a dichromatic vision with high acuity indicated by the presence of a dorsotemporally located area centralis.  相似文献   
29.
Adherence of low-income women to cancer screening recommendations   总被引:2,自引:0,他引:2       下载免费PDF全文
BACKGROUND: African-American and low-income women have lower rates of cancer screening and higher rates of late-stage disease than do their counterparts. OBJECTIVE: To examine the effects of primary care, health insurance, and HMO participation on adherence to regular breast, cervical, and colorectal cancer screening. DESIGN: Random-digit-dial and targeted household telephone survey of a population-based sample. SETTING: Washington, D.C. census tracts with > or =30% of households below 200% of federal poverty threshold. PARTICIPANTS: Included in the survey were 1,205 women over age 40, 82% of whom were African American. MAIN OUTCOME MEASURES: Adherence was defined as reported receipt of the last 2 screening tests within recommended intervals for age. RESULTS: The survey completion rate was 85%. Overall, 75% of respondents were adherent to regular Pap smears, 66% to clinical breast exams, 65% to mammography, and 29% to fecal occult blood test recommendations. Continuity with a single primary care practitioner, comprehensive service delivery, and higher patient satisfaction with the relationships with primary care practitioners were associated with higher adherence across the 4 screening tests, after considering other factors. Coordination of care also was associated with screening adherence for women age 65 and over, but not for the younger women. Compared with counterparts in non-HMO plans, women enrolled in health maintenance organizations were also more likely to be adherent to regular screening (e.g., Pap, odds ratio [OR] 1.89, 95% confidence interval [CI] 1.11 to 3.17; clinical breast exam, OR 2.04, 95% CI 1.21 to 3.44; mammogram, OR 1.95, 95% CI 1.15 to 3.31; fecal occult blood test, OR 1.70, 95% CI 1.01 to 2.83.) CONCLUSIONS: Organizing healthcare services to promote continuity with a specific primary care clinician, a comprehensive array of services available at the primary care delivery site, coordination among providers, and better patient-practitioner relationships are likely to improve inner-city, low-income women's adherence to cancer screening recommendations.  相似文献   
30.
黑色塑料地膜覆盖灭螺近期效果观察   总被引:5,自引:2,他引:5  
目的观察有螺排灌沟使用黑色塑料地膜结合氯硝柳胺不同用量一次性喷洒与未覆盖近期灭螺效果。方法选择1条有螺排灌沟,分12段,覆盖6段分设氯硝柳胺0、2、4、6、8、10g/m^2组。未覆盖6段分设空白对照,氯硝柳胺2、4、6、8、10g/0组,试前各组按系统抽样法每组调查7框,捕获框内全部土表钉螺观察。调查后各组按设计用药量每m^2加水1000ml配制喷洒,各组覆盖黑色塑料地膜。试后12个组1、2、3、5、7、10d按试前调查方法捕获钉螺观察,同时每天8、10、12、16、18时测环境气温覆盖与未覆盖土表、土内3cm、6cm、15cm处温度。结果覆盖组10:00-16:00土表温度最高,晴天维持在40℃~62℃之间,土层内3~15em深处均在22℃~36℃之间。在盖膜10d内,无药组累计钉螺死亡率44.55%,密度下降72.90%,加药各组死亡率为64.79%~85.59%。密度下降率84.83%~95.24%,未覆盖各组死亡率58.03%~83.81%,密度下降率59.96%~90.17%。结论黑色塑料地膜灭螺近期效果,喷药各组均比不喷药组钉螺死亡率和活螺平均密度下降率高,同时高于对应未覆盖各组,该方法省时、省工、操作简便,灭螺效果好,易检查考核,适合多种有螺环境灭螺,宜继续研究和推广应用。  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