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   26062篇
  免费   2386篇
  国内免费   146篇
耳鼻咽喉   261篇
儿科学   620篇
妇产科学   350篇
基础医学   3182篇
口腔科学   817篇
临床医学   3452篇
内科学   5615篇
皮肤病学   642篇
神经病学   1875篇
特种医学   1257篇
外科学   3578篇
综合类   479篇
一般理论   24篇
预防医学   2687篇
眼科学   358篇
药学   2043篇
中国医学   23篇
肿瘤学   1331篇
  2021年   367篇
  2020年   204篇
  2019年   352篇
  2018年   376篇
  2017年   278篇
  2016年   341篇
  2015年   396篇
  2014年   529篇
  2013年   842篇
  2012年   1131篇
  2011年   1128篇
  2010年   664篇
  2009年   610篇
  2008年   1048篇
  2007年   1091篇
  2006年   1090篇
  2005年   1115篇
  2004年   1026篇
  2003年   982篇
  2002年   985篇
  2001年   989篇
  2000年   1020篇
  1999年   865篇
  1998年   390篇
  1997年   339篇
  1996年   344篇
  1995年   333篇
  1994年   287篇
  1993年   279篇
  1992年   628篇
  1991年   658篇
  1990年   610篇
  1989年   547篇
  1988年   520篇
  1987年   505篇
  1986年   508篇
  1985年   502篇
  1984年   352篇
  1983年   314篇
  1982年   236篇
  1981年   226篇
  1980年   172篇
  1979年   328篇
  1978年   247篇
  1977年   215篇
  1976年   176篇
  1975年   172篇
  1974年   215篇
  1973年   204篇
  1971年   193篇
排序方式: 共有10000条查询结果,搜索用时 17 毫秒
121.
Conventional teaching states that the spiral of Tillaux marks the location of the ora serrata. On literature review, no source for this was found. This study explores this anatomic relationship. In 20 cadaver eyes, narrow-gauge needles were placed penetrating the center of each rectus muscle insertion, and distance to the ora was measured. Insertions ranged from 2.25 mm posterior to 2.25 mm anterior to the ora, with 90% within 1 mm of it. In ten eyes, distance from the edge of insertion also was measured. Results indicate that the centers of rectus insertions, especially the lateral rectus, approximately overlie the ora, with the edges of the insertions more posterior and variable.  相似文献   
122.
STUDY OBJECTIVE: To compare the sedative, anxiolytic, and amnestic effects, as well as the recovery characteristics, when midazolam (vs. a placebo) is administered to patients receiving a propofol infusion for sedation during local anesthesia. DESIGN: Randomized, double-blind, placebo-controlled study to evaluate the perioperative effects of intravenous (IV) midazolam. SETTING: Outpatient surgery center of a university-affiliated medical center. PATIENTS: One hundred thirty-nine consenting, ASA physical status I, II, and III outpatients undergoing elective surgical procedures under local anesthesia. INTERVENTIONS: Patients were randomly assigned to receive either midazolam 2 mg IV or saline 2 ml IV prior to injection of local anesthesia. Intraoperative sedation was maintained using a variable-rate propofol infusion. MEASUREMENTS AND MAIN RESULTS: Preoperative assessment of sedation, anxiety, and amnesia was performed before and after IV midazolam. Intraoperative evaluations included level of sedation, as well as cardiovascular and respiratory measurements, at 1- to 5-minute intervals during the operation. Postoperatively, recovery of psychomotor function and patients' subjective feelings were assessed using the visual analog scale and questionnaires. Amnesia was assessed using picture recall during the perioperative period. In the operating room, midazolam 2 mg IV, compared with the placebo, produced a significantly greater increase in patients' level of sedation (7 +/- 13 mm to 49 +/- 21 mm for midazolam vs. 8 +/- 11 mm to 19 +/- 21 mm for the placebo; p less than 0.01) and a greater decrease in anxiety level (62 +/- 25 mm to 21 +/- 21 mm for midazolam vs. 54 +/- 27 mm to 53 +/- 22 mm for the placebo; p less than 0.01). Although the propofol dosage requirements to maintain comparable levels of sedation were similar in both groups, midazolam decreased patients' recall of intraoperative events (e.g., propofol-induced pain on injection and discomfort with local anesthetic injection) without significantly altering cardiorespiratory parameters or prolonging times to ambulation and discharge from the outpatient facility. CONCLUSIONS: Premedication with midazolam 2 mg IV produced increased sedation, amnesia, and anxiolysis when administered immediately prior to the propofol infusion as part of a sedation technique for outpatient surgery. This combination did not prolong the recovery room stay when compared with propofol alone.  相似文献   
123.
Respiratory muscle weakness is an uncommon cause of chronic respiratory failure and a rare cause of cor pulmonale. The problem may not be apparent unless specific physical signs are sought or appropriate investigations performed. We present three patients who presented diagnostic difficulty for prolonged periods until the presence of respiratory muscle weakness was considered. Once the diagnosis was established treatment with nocturnal nasal intermittent positive pressure ventilation produced a dramatic improvement in symptoms and allowed a return to a near normal lifestyle.  相似文献   
124.
125.
Twenty-five patients (21-45 years old) treated for Hodgkin's disease with mantle radiotherapy but no chemotherapy underwent chest radiography and pulmonary testing with spirometry, pulmonary mechanics and exercise test combined with arterial blood gas analysis, lung scintigraphy, assessment of pulmonary artery pressure with Doppler cardiography and vector ECG 10-20 years after treatment. The doses to mediastinum ranged from 35-43 (mean 40) Gy given in 26 fractions with the split-course technique. Radiographic signs of slight to moderate pulmonary fibrosis were seen in 18 patients. Minor restrictive ventilatory defects were found with decreased VC, TLC and lung compliance and increased maximal elastic recoil. Little evidence of airflow obstruction was found. Exercise capacity was decreased in three individuals but the mean value for the study group as a whole was normal. Arterial PO2 at maximum exercise was reduced but no patient had diminished hemoglobin saturation. Lung scintigraphy showed defects in 21 patients, mostly consisting of slight abnormalities at the lung periphery and apices. The perfusion seemed to be more affected than the ventilation, suggesting primary vascular lesions. Twelve patients showed signs of right ventricular hypertrophy in vector ECG and four of these had systolic pulmonary artery pressure greater than or equal to 30 mm Hg. The observed abnormalities were mostly of a minor degree and few clinically significant long-term effects of mantle radiotherapy on pulmonary function were observed.  相似文献   
126.
127.
Many mental health clinics rely heavily on group treatment in the outpatient care of individuals with schizophrenia. Groups are used because they economize clinician time and provide social interaction for isolated patients. Empirical evidence suggests that groups, combined with medication, are at least as effective as other common treatments. Many group formats and techniques have been used. Choices are often based on pragmatism or inclination, rather than theory or experiment. The authors review recent findings from research on the neurobiology of schizophrenia, its natural history, and the impact of psychosocial factors in its course and treatment. From these findings, they elaborate research based principles for outpatient group therapy in schizophrenia. They describe three distinct formats for group treatment, and delineate the scope of use for each. Finally, they propose guidelines for assignment of patients to appropriate group treatments.Portions of this material were presented at the 1988 Hospital Community Psychiatry Institute, and at the 1989 meeting of the American Psychiatric Association.  相似文献   
128.
129.
130.
BACKGROUND AND PURPOSE: Neutrophils are critically involved with ischemia and reperfusion injury in many tissues but have not been studied under conditions of reperfusion after focal cerebral ischemia. The present studies were conducted to confirm our previous observations quantifying neutrophils in rat permanent focal stroke using a myeloperoxidase activity assay and to extend them to transient ischemia with reperfusion. In addition, leukotriene B4 receptor binding in ischemic tissue was evaluated as a potential marker for inflammatory cell infiltration. METHODS: Histological, enzymatic, and receptor binding techniques were used to evaluate neutrophil infiltration and receptor binding in infarcted cortical tissue 24 hours after permanent middle cerebral artery occlusion (n = 25) or temporary occlusion for 80 (n = 12) or 160 (n = 22) minutes followed by reperfusion for 24 hours in spontaneously hypertensive rats. RESULTS: Sham surgery (n = 26) produced no changes in any parameter measured. After permanent middle cerebral artery occlusion, neutrophil accumulation was observed histologically, but the infiltration was moderate and typically within and adjacent to blood vessels bordering the infarcted cortex. After temporary middle cerebral artery occlusion with reperfusion, marked neutrophil infiltration was observed throughout the infarcted cortex. Myeloperoxidase activity was increased (p less than 0.05) after permanent occlusion and to a greater extent after temporary occlusion with reperfusion. Myeloperoxidase activity (units per gram wet weight) in ischemic cortex was increased over that in nonischemic (control) cortex 32.2-fold, 54.6-fold, and 92.1-fold for permanent occlusion and 80 and 160 minutes of temporary occlusion with reperfusion, respectively (p less than 0.05). Sham surgery produced no changes in myeloperoxidase activity. Leukotriene B4 receptor binding also was increased (p less than 0.05) after focal ischemia and paralleled the increases in myeloperoxidase activity. Ischemic cortex-specific receptor binding (femtomoles per milligram protein) was 3.87 +/- 0.63 in sham-operated rats and 4.57 +/- 0.98, 8.98 +/- 1.11, and 11.12 +/- 1.63 for rats subjected to permanent occlusion and 80 and 160 minutes of temporary occlusion with reperfusion, respectively (all p less than 0.05 different from sham-operated). Cortical myeloperoxidase activity was significantly correlated with the degree of cortical leukotriene B4 receptor binding (r = 0.66 and r = 0.79 in two different studies, p less than 0.01). CONCLUSION: These data indicate that neutrophils are involved in focal ischemia and that there is a dramatic accumulation of neutrophils in infarcted tissue during reperfusion that can be quantified using the myeloperoxidase activity assay. Leukotriene B4 receptor binding increases in infarcted tissue in a parallel manner, which suggests that the increased leukotriene B4 binding is to receptors located on the accumulating neutrophils.  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