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   20788篇
  免费   1698篇
  国内免费   54篇
耳鼻咽喉   258篇
儿科学   571篇
妇产科学   257篇
基础医学   2588篇
口腔科学   256篇
临床医学   2483篇
内科学   4363篇
皮肤病学   285篇
神经病学   2104篇
特种医学   745篇
外国民族医学   1篇
外科学   3587篇
综合类   321篇
一般理论   23篇
预防医学   1900篇
眼科学   440篇
药学   1156篇
中国医学   18篇
肿瘤学   1184篇
  2023年   177篇
  2022年   263篇
  2021年   899篇
  2020年   471篇
  2019年   700篇
  2018年   840篇
  2017年   548篇
  2016年   563篇
  2015年   625篇
  2014年   918篇
  2013年   1039篇
  2012年   1699篇
  2011年   1640篇
  2010年   848篇
  2009年   712篇
  2008年   1195篇
  2007年   1173篇
  2006年   986篇
  2005年   925篇
  2004年   860篇
  2003年   769篇
  2002年   593篇
  2001年   266篇
  2000年   267篇
  1999年   232篇
  1998年   144篇
  1997年   106篇
  1996年   96篇
  1995年   136篇
  1994年   166篇
  1993年   148篇
  1992年   217篇
  1991年   191篇
  1990年   154篇
  1989年   183篇
  1988年   169篇
  1987年   131篇
  1986年   134篇
  1985年   141篇
  1984年   105篇
  1983年   89篇
  1982年   70篇
  1979年   99篇
  1978年   60篇
  1977年   54篇
  1976年   54篇
  1974年   59篇
  1973年   64篇
  1972年   56篇
  1969年   53篇
排序方式: 共有10000条查询结果,搜索用时 343 毫秒
91.
Residential nursing staff were asked to complete the Maslach Burnout Inventory (MBI) each month for a total of six months throughout a service transition involving the move of a group of men with profound learning disabilities, some with additional challenging behaviours, from two hospital wards to a community-living orientated hostel. The MBI was used to measure the effect on staff of the intense reorganisation in their working environment. Significant increases in Emotional Exhaustion and Depersonalisation, and a (non significant) decrease in Personal Accomplishment were found during the transition. Levels reverted to baseline following the move, but burnout remained above the mean of a previously published study, for two of the three dimensions. Levels of absenteeism largely mirrored the pattern of the MBI scores, with a one-month lapse between high burnout and high absenteeism, supporting previous research indicating an association between the two.  相似文献   
92.
The case describes a female patient with squamous cell carcinoma of the lung who initially presented with mechanical upper-back and neck pain. She had been successfully treated with spinal manipulation for a similar complaint one year earlier, a factor that decreased the suspicion of pathological process on her second presentation. Serious disease as the cause of back pain must be considered in cases with certain historical factors, or when the patient fails to respond to treatment for mechanical back pain.  相似文献   
93.
OBJECTIVE: To evaluate the effect of preoperative localization studies on the surgical management of patients with primary hyperparathyroid disease (PHPT). SUMMARY BACKGROUND DATA: Reported cure rates of initial surgical exploration for PHPT are close to 95%. Preoperative localization studies are frequently obtained to improve surgical success and decrease operative time. METHODS: Initial cervical exploration was performed in 113 patients with PHPT from 1981 to 1993. Twenty-four patients (21%) had surgery without preoperative localization studies. The remaining 89 patients (79%) had 132 noninvasive preoperative localization studies. Success of the localization studies in tumor localization, pathologic findings, postoperative serum calcium levels, and operative times were compared. Patient costs of the studies were calculated. RESULTS: Disease was identified during operation in 23 of 24 patients (96%) having cervical exploration without preoperative localization studies, and they had normal calcium levels after surgery. Eighty-seven of 89 patients (98%) having preoperative localization studies were surgically cured. The highest sensitivity rate (60%) and highest positive predictive value (79%) of the localization studies were found with thallium-technetium scintiscanning. Average cost of the localization studies was $901 per patient. Combination studies were obtained in 32 patients at an average cost of $1,314 per patient without improving sensitivity. Mean operating time did not differ for localized and nonlocalized patients. CONCLUSIONS: Preoperative localization studies did not improve parathyroid localization or cure rate and did not substantially shorten operating time in initial cervical exploration for PHPT. The economic burden of routine preoperative localization studies in these patients is not justified.  相似文献   
94.
Use of Internet information by women with breast cancer   总被引:1,自引:0,他引:1  
  相似文献   
95.
BACKGROUND: Habitual arecanut chewing is associated with Oral Submucous Fibrosis (OSF). High copper content in arecanut plays a vital role in pathogenesis of OSF. This study evaluates the copper-staining pattern of buccal epithelial cells in oral cytological smears of non-chewers, chewers, and OSF. MATERIALS & METHODS: Alcohol fixed buccal epithelial smears of 10 histopathologically confirmed cases of OSF, 10 chewers without lesion, and 5 nonchewers were stained with modified Rhodamine technique and studied under the light microscope. Buccal epithelial smears of non-chewers dipped in copper sulphate solution were used as known positive for copper. RESULT: Copper appeared as shades of palered within the cytoplasm of chewers and did not show any stain in non-chewers. Intense red stain was seen in OSF smears as dark granules within the cytoplasm. CONCLUSION: Intense staining of copper in OSF buccal smears, than in the chewers supports the role of copper in the pathogenesis of OSF.  相似文献   
96.
Background: Pediatric cardiopulmonary arrest (CPA) outside of the hospital has a very high mortality rate. Objectives: To evaluate the etiology and initial compromise of pediatric CPA cases in hopes of developing strategies to improve out‐of‐hospital resuscitation. Methods: The Ontario Prehospital Advanced Life Support (OPALS) study was a large multicenter initiative to evaluate the impact of emergency medical services (EMS) programs on 17 communities with 40,000 critically ill and injured patients who were older than 11 years. As part of this study, the authors conducted a retrospective observational cohort study that included all children younger than 18 years of age with out‐of‐hospital CPA, during an 11‐year period from 1991–2002. CPA was defined as patient being pulseless, apneic, and requiring chest compressions. Data were collected from ambulance call reports and centralized dispatch data and were reviewed by two independent investigators. Results: There were 503 children with CPA in the sample. Mean age was 5.6 years (range, 0–17 yr); 58.4% of patients were male, and 37.8% were younger than 1 year of age. Cardiopulmonary resuscitation (CPR) first was started by a bystander in 32.4% of cases, whereas 66.0% were unwitnessed arrests. Initial rhythms were asystole 77.2% of the time, pulseless electrical activity 16.4% of the time, and ventricular fibrillation or ventricular tachycardia 4% of the time. Annual incidence was 9.1/100,000 children. CPA was witnessed in 34.0% of cases; 80.7% of these were bystander‐witnessed, and 18.1% were EMS‐witnessed. Primary pathogenic cause of arrest was medical in 61.2% of cases, trauma in 37.2% of cases, and indeterminate in 1.6% of cases. Initial underlying physiologic compromise of witnessed arrests was judged to be respiratory in 39.8% of cases, sudden collapse (presumed electrical) in 16.4% of cases, progressive shock in 1.2% of cases, and indeterminate in 42.6% of cases. Presumed etiology was trauma, 37.6%; sudden infant death syndrome (SIDS), 20.3%; and respiratory disease, 11.6%, most commonly. Survival to hospital discharge was 2.0%. Conclusions: This is one of the largest population‐based, prospective cohorts of pediatric CPA reported to date, and it reveals that most pediatric arrests are unwitnessed and receive no bystander CPR. Those that are witnessed most often are caused by respiratory arrests or trauma. Trauma, SIDS, and respiratory disease are the most common etiologies overall. These data are vital to planning large resuscitation trials looking at specific interventions (i.e., increasing bystander CPR) and highlight the need for better strategies for prevention and early recognition.  相似文献   
97.
休克期切痂对烫伤大鼠全身和肠道局部免疫功能的影响   总被引:3,自引:3,他引:0  
目的 观察休克期切痂对烫伤大鼠全身和肠道局部免疫功能的影响 ,探讨其可能的机制。 方法 选用 96只Wistar大鼠。取其中 2 4只大鼠的躯干部皮肤冻存于液氮中 ,另取 8只作正常对照组。余下 6 4只造成 30 %TBSAⅢ度烫伤后 ,随机分为A组 2 4只 ,伤后不作任何处理 ;B组 2 4只 ,伤后 2 4h腹腔注射等渗盐水 5 0ml/kg,一次性切痂后用上述冻存异体皮覆盖 ;C组 1 6只 ,伤后 72h进行处理 ,方法同B组。检测A、B组大鼠伤后 2、4、8d和C组伤后 4、8d及正常对照组大鼠的脾淋巴细胞增殖功能、血浆和肠组织白细胞介素 (IL)2水平、肠黏液分泌型免疫球蛋白A(sIgA)及肠组织中二胺氧化酶 (DAO)含量的变化。 结果 各时相点下A、B、C组大鼠脾淋巴细胞增殖功能、血浆IL 2水平、肠组织IL 2及肠黏液sIgA含量均较正常对照组减少。B组伤后 4、8d和C组伤后 8d的脾淋巴细胞增殖功能接近正常对照组 ,血浆和肠组织IL 2水平明显高于A组 (P <0.0 1)。伤后 4、8d,B组肠黏液sIgA含量分别为 (3.5 1± 2 .1 4 )、(3.0 3± 0 .95 )mg/g,C组分别为 (1 .4 0± 0 .6 4 )、(1 .5 2± 1 .2 6 )mg/g,B组较C组增加近 1倍 (P 0.0 1 )。A组伤后 4、8d肠组织DAO活性低于正常对照组和B组 (P 0.0 5)。结论 休克期切痂有助于烫伤大鼠全身和肠道  相似文献   
98.
The oxidation of body fuel stores in cancer patients.   总被引:1,自引:0,他引:1       下载免费PDF全文
In an attempt to define the mechanism of weight loss in cancer patients, fat and carbohydrate oxidation rates were calculated in 93 patients. Seventy patients with colorectal or gastric cancer were compared with a control group of 23 patients with nonmalignant illness. Twenty-seven patients with cancer and 13 control patients had lost more than 10% of their pre-illness body weight. Fat and carbohydrate oxidation rates were derived from measurements of oxygen consumption, carbon dioxide production, and urinary nitrogen excretion. Patients with cancer had significantly higher fat oxidation rates (p less than 0.01) and significantly lower carbohydrate oxidation rates (p less than 0.05) when compared with controls. Weight-losing cancer patients had significantly higher fat oxidation rates when compared with weight-stable cancer patients (p less than 0.02), weight-stable controls (p less than 0.01), and weight-losing controls (p less than 0.02). Cancer patients with liver metastases (N = 14) had significantly higher fat oxidation rates (p less than 0.01) and significantly lower carbohydrate oxidation rates (p less than 0.01) compared with cancer patients who had localized disease. There were no significant differences among the groups with respect to resting energy expenditure when expressed as kilocalorie per kilogram lean body mass per day. The presence of cancer appears to be associated with abnormal fat and carbohydrate metabolism. The increased rate of fat oxidation seen in patients with cancer, especially those with weight loss or liver metastases, may be a significant factor in the development of cancer cachexia.  相似文献   
99.
This study examined whether relationships between anger expression, hostility, social evaluative anxiety, and a presumed mechanism for coronary heart disease development, cardiovascular reactivity (CVR) to stress, are moderated by stress situation and gender and whether such relationships are attenuated by inadequate assessments. Subjects (47 men, 47 women) were assigned randomly to either a Harassment or a Social Evaluation condition, under which they performed a reaction time task. SBP, DBP, and HR measures were recorded during baseline and task. Multiple regression analyses indicated that expressed anger was related to CVR only among men in the Harassment condition; that hostile men who express anger showed the most CVR across situations, and that the traits assessed here did not predict CVR among women. Results suggest that assessments of coronary-risk and interventions to reduce risk may need to take into account attitudes, styles of emotional expression, environmental factors, and gender.This research was supported in part by an NIMH predoctoral fellowship (F31MH09836) awarded to John W. Burns and by a grant from the American Heart Association (89-01-3G) awarded to Edward S. Katkin.  相似文献   
100.
Tumor vascular signals in renal masses: detection with Doppler US   总被引:3,自引:0,他引:3  
Ramos  IM; Taylor  KJ; Kier  R; Burns  PN; Snower  DP; Carter  D 《Radiology》1988,168(3):633-637
The vascularity of 49 renal masses (26 malignant and 23 benign lesions) was investigated with duplex Doppler ultrasound. Doppler signals obtained at the margins of renal masses were defined as "tumor signals" when the Doppler-shifted frequency of the lesion exceeded the frequency shift in the ipsilateral main renal artery. These exceeded 2.5 kHz with a 3-MHz insonating frequency. Among the 26 renal masses that subsequently proved to be malignant, tumor signals were obtained in 15 of 18 (83%) untreated renal cell carcinomas, in three of four Wilms tumors, and in two patients with metastases to the kidney, but not in the one patient with lymphoma. None of the 23 benign renal masses demonstrated tumor signals. Tumor vascularity in malignant lesions gives rise to abnormal, high-velocity, Doppler-shifted signals that can help in the differential diagnosis of renal masses.  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