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   2699篇
  免费   270篇
  国内免费   17篇
耳鼻咽喉   27篇
儿科学   56篇
妇产科学   48篇
基础医学   407篇
口腔科学   67篇
临床医学   358篇
内科学   511篇
皮肤病学   27篇
神经病学   247篇
特种医学   155篇
外科学   316篇
综合类   56篇
一般理论   1篇
预防医学   257篇
眼科学   73篇
药学   193篇
中国医学   4篇
肿瘤学   183篇
  2022年   18篇
  2021年   42篇
  2020年   24篇
  2019年   40篇
  2018年   58篇
  2017年   34篇
  2016年   27篇
  2015年   59篇
  2014年   47篇
  2013年   77篇
  2012年   130篇
  2011年   103篇
  2010年   77篇
  2009年   95篇
  2008年   117篇
  2007年   94篇
  2006年   95篇
  2005年   102篇
  2004年   115篇
  2003年   94篇
  2002年   79篇
  2001年   90篇
  2000年   83篇
  1999年   80篇
  1998年   46篇
  1997年   42篇
  1996年   43篇
  1995年   47篇
  1994年   30篇
  1993年   29篇
  1992年   67篇
  1991年   69篇
  1990年   61篇
  1989年   75篇
  1988年   57篇
  1987年   42篇
  1986年   57篇
  1985年   56篇
  1984年   45篇
  1983年   43篇
  1982年   34篇
  1980年   23篇
  1979年   34篇
  1978年   26篇
  1976年   25篇
  1975年   30篇
  1973年   24篇
  1972年   17篇
  1971年   17篇
  1969年   21篇
排序方式: 共有2986条查询结果,搜索用时 0 毫秒
1.
2.
BACKGROUND: Delays in seeking treatment for signs and symptoms of acute myocardial infarction are longer for African Americans than for whites. OBJECTIVE: To determine factors associated with prolonged delay and the extent to which perceived racism influences prehospital delay in African Americans with acute myocardial infarction. METHODS: Sixty-one African Americans with acute myocardial infarction were interviewed within 1 month of hospital admission. Delay times were calculated on the basis of the interviews. Independent t tests and chi(2) tests were used to determine factors associated with prolonged delays. RESULTS: Median delay was 4.25 hours and did not differ significantly between women and men (4.42 vs 3.50 hours). Most patients (69%) experienced their initial signs and symptoms at home, often witnessed by family members or friends (70%). Delay was longer for insured patients than for uninsured patients (4.45 vs 0.50 hours). Single, widowed, or divorced patients had longer delay times than did married patients (5.33 vs 2.50 hours), and patients with diabetes delayed longer than did those without diabetes (7.29 vs 3.50 hours). Perceived racism did not differ significantly between patients who delayed seeking treatment and those who did not. CONCLUSIONS: Median delay times were substantially longer than the recommended time of less than 1 hour, reducing the benefit from reperfusion therapies. Education and counseling of patients and their families should be a major strategy in optimizing patients' outcomes and decreasing the time to definitive treatment.  相似文献   
3.
The aim of this study was to evaluate the effectiveness of incremental and maximum bite advancement during treatment of Class II Division 1 malocclusion with the Twin-block appliance in the permanent dentition. It was performed at 3 district general hospitals in the United Kingdom with 4 operators. Two hundred three patients, 10-14 years old, were randomized. Control patients had the initial bite taken edge-to-edge for appliance construction with a standard Twin-block. Experimental patients had 2 mm initial bite advancement and subsequent 2 mm advancements at 6 weekly intervals with a Twin-block appliance incorporating advancement screws. Data were collected at the start and the finish of Twin-block treatment. The use of incremental advancement of the Twin-block did not confer any advantages in terms of process and outcome of the treatment. However, patient compliance was influenced by operator and patient age. The duration of treatment was influenced by operator and initial overjet. Incremental bite advancement produced no advantages over maximum advancement.  相似文献   
4.
Primary dystonia is a disorder of movement for which no consistent pathophysiology has been identified; in the absence of evidence to the contrary, it is assumed to be cognitively benign. We have studied a clinically heterogeneous group of 14 patients with primary dystonia on a battery of neuropsychological tests. Despite well-preserved speed of information processing, language, spatial, memory and general intellectual skills relative to normal controls, we have identified a constellation of attentional-executive cognitive deficits on the Cambridge Neuropsychological Test Automated Battery (CANTAB). Specifically, patients demonstrated significant difficulties negotiating the extra-dimensional set-shifting phase of the IED task. The implications of these findings for the pathophysiology of primary dystonia are discussed. This is, to the best of our knowledge, the first report of a significant cognitive deficit in patients with primary dystonia.  相似文献   
5.
Background. Hypoxia and warm ischemia produce severe injury to cardiac grafts harvested from non–heart-beating donors. To potentially improve recovery of such grafts, we studied the effects of intravenous phenylephrine preconditioning.Methods. Thirty-seven blood-perfused rabbit hearts were studied. Three groups of non–heart-beating donors underwent intravenous treatment with phenylephrine at 12.5 (n = 8), 25 (n = 7), or 50 μg/kg (n = 7) before initiation of apnea. Non–heart-beating controls (n = 8) received saline vehicle. Hypoxic cardiac arrest occurred after 6 to 12 minutes of apnea, followed by 20 minutes of warm in vivo ischemia. A 45-minute period of ex vivo reperfusion ensued. Nonischemic controls (n = 7) were perfused without antecedent hypoxia or ischemia.Results. Phenylephrine 25 μg/kg significantly delayed the onset of hypoxic cardiac arrest compared with saline controls (9.6 ± 0.5 versus 7.7 ± 0.4 minutes; p = 0.00001), yet improved recovery of left ventricular developed pressure compared with saline controls (57.1 ± 5.3 versus 41.0 ± 3.4 mm Hg; p = 0.04). Phenylephrine 25 μg/kg also yielded a trend toward less myocardial edema than saline vehicle (p = 0.09).Conclusions. Functional recovery of nonbeating cardiac grafts is improved by preconditioning. We provide evidence that the myocardium can be preconditioned with phenylephrine against hypoxic cardiac arrest.(Ann Thorac Surg 1997;63:1664–8)  相似文献   
6.
We report a patient with alcohol-induced necrotizing pancreatitis who developed a severe ileus followed by incarceration of a portion of the transverse colon within a ventral hernia. Laparotomy 9 days after the onset of symptoms revealed infarction of the transverse colon and infection of the pancreas. This is the first report of a case of acute pancreatitis that led to a strangulated ventral hernia of the colon. We believe that the enteric organisms that infected the pancreas originated in the incarcerated transverse colon.  相似文献   
7.
OBJECTIVES: We tested the hypothesis that mastoid volume buffers the rate of change in middle ear pressure caused by transmucosal, inert gas exchange. STUDY DESIGN: Twelve monkeys were randomly assigned to group 1 or group 2. Right ears of group 1 had sham surgery and of group 2 had obstruction of the mastoid antrum. Before and after surgery, the time constant for transmucosal N(2)O exchange was estimated from N(2)O breathing experiments. The hypothesis predicts that the postoperative time constant measured for right ears of group 2 but not group 1 is greater than that measured before surgery. RESULTS: Mastoid antrum block significantly decreased right middle ear volume but did not affect the time constant for transmucosal N(2)O exchange. CONCLUSION: A mastoid gas-reserve function is not supported by the experimental data. SIGNIFICANCE: These results for monkeys and the theory developed to explain the effect of mastoid volume on transmucosal inert gas exchange suggest that the results for previous experiments in humans interpreted as evidencing a mastoid gas-reserve function are consistent with alternative explanations.  相似文献   
8.
9.
New York State’s Children and Youth Intensive Case Management (CYICM) was implemented in 1988 as one of several community-based initiatives for children with serious emotional disturbance (SED). Underlying this program is the goal of maintaining children with SED in the least restrictive environment appropriate to their needs. This paper presents CYICM child, family, and system outcomes over six years, describes program refinements, and explores continuing research efforts. Data are supportive of the positive outcomes associated with intensive case management for children with SED. Associated with enrollment in CYICM are a decrease in symptoms, improvement in functioning, and fewer hospitalizations in state-operated psychiatric centers, which translates into cost savings and a possible reduction in hospital beds.  相似文献   
10.
Zolmitriptan (ZomigTM) is a 5HT1B/1D agonist which has the ability to cross the intact blood-brain barrier to access central as well as peripheral receptors. Because of the potential for central nervous system side effects, this randomized, double-blind, placebo-controlled, 6-period crossover study evaluated the effects of 2.5 and 5 mg doses of zolmitriptan on psychomotor performance and investigated any pharmacodynamic or pharmacokinetic interaction with diazepam. Twelve healthy volunteers received the following "treatments" as single doses: zolmitriptan 2.5 mg, zolmitriptan 5 mg, diazepam 10 mg, zolmitriptan 2.5 mg+diazepam 10 mg, zolmitriptan 5 mg+diazepam 10 mg and placebo. Pre-dose and at 1, 4, 8, and 24 h post-dose, the following validated battery of psychomotor tests was performed: Bond-Lader visual analogue scales (calmness, contentedness, and alertness factors), critical flicker fusion test, choice reaction time (recognition, motor, and total reaction times), finger-tapping test, number cancellation test and digit symbol substitution test. Plasma concentrations of zolmitriptan, its active metabolite, and diazepam and its active metabolites were measured at the same timepoints. Zolmitriptan 2.5 and 5 mg had no effect on psychomotor function when given alone. In contrast, diazepam 10 mg had profound effects, consistent with its sedative properties, but there was no synergism on concomitant administration of either dose of zolmitriptan. Plasma concentrations of zolmitriptan, diazepam, and their respective active metabolites were similar when the two drugs were given alone or in combination.  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