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   4535篇
  免费   436篇
  国内免费   27篇
耳鼻咽喉   39篇
儿科学   147篇
妇产科学   81篇
基础医学   585篇
口腔科学   77篇
临床医学   528篇
内科学   727篇
皮肤病学   61篇
神经病学   369篇
特种医学   331篇
外科学   624篇
综合类   96篇
一般理论   3篇
预防医学   495篇
眼科学   50篇
药学   407篇
中国医学   3篇
肿瘤学   375篇
  2021年   48篇
  2020年   32篇
  2019年   42篇
  2018年   43篇
  2017年   35篇
  2016年   55篇
  2015年   46篇
  2014年   87篇
  2013年   137篇
  2012年   204篇
  2011年   212篇
  2010年   120篇
  2009年   100篇
  2008年   171篇
  2007年   175篇
  2006年   168篇
  2005年   166篇
  2004年   155篇
  2003年   158篇
  2002年   167篇
  2001年   135篇
  2000年   154篇
  1999年   155篇
  1998年   96篇
  1997年   74篇
  1996年   75篇
  1995年   75篇
  1994年   54篇
  1993年   62篇
  1992年   131篇
  1991年   119篇
  1990年   100篇
  1989年   112篇
  1988年   104篇
  1987年   135篇
  1986年   113篇
  1985年   106篇
  1984年   53篇
  1983年   52篇
  1982年   42篇
  1981年   49篇
  1980年   41篇
  1979年   71篇
  1978年   40篇
  1977年   33篇
  1976年   60篇
  1975年   34篇
  1974年   43篇
  1973年   36篇
  1967年   29篇
排序方式: 共有4998条查询结果,搜索用时 15 毫秒
31.
OBJECTIVE: Depression after hip fracture surgery is prevalent and associated with increased mortality rates and impaired functional recovery. The incidence of new-onset depressive symptoms in patients initially not depressed after hip fracture surgery and their relationship with functional recovery is unknown. METHODS: A cohort of 139 nondepressed elderly patients (>60 years) hospitalized for hip fracture surgery were followed up for six months. Clinically significant depressive symptoms were defined as a score of 7 or more on the 15-item Geriatric Depression Scale. RESULTS: The authors found a cumulative incidence rate of 20.5% adjusted for dropouts. Multiple Cox-regression analyses yielded the presence of subthreshold symptoms of depression, anxiety, pain, and cognitive impairment at baseline, the premorbid level of mobility, and a history of (treated) depression as risk factors for incident depression (p <0.05). A forward, conditional procedure identified postoperative pain (hazard ratio [HR] = 1.32, 95% confidence interval [CI]: 1.14-1.53, Wald chi(2) = 13.57, df = 1, p <0.001) and baseline anxiety (HR = 1.25, 95% CI: 1.08-1.44, Wald chi(2) = 8.86, df = 1, p = 0.003) as the strongest independent risk factors. Incident depression was associated with a less favorable outcome at 3 months follow-up. CONCLUSION: This exploratory study identified two treatable baseline characteristics that predicted incident depression in nondepressed patients after hip-fracture surgery.  相似文献   
32.
A pilot survey of one third-year medical school class was carried out to explore student perceptions of mistreatment and professional misconduct in medical school training. Students were asked to rate the frequency and cite sources of mistreatment and misconduct among classmates, faculty, residents, and interns. They were also asked to assess the effects of such episodes on their physical health, emotional well-being, social and family life, and attitudes toward becoming a physician. The results indicate that students perceive mistreatment (particularly verbal abuse and unfair tactics) to be pervasive and professional misconduct all too common. As many as three fourths of the students report having become more cynical about academic life and the medical profession as a result of these episodes. Two thirds feel they are worse off than their peers in other professions. More than a third have considered dropping out of medical school and one fourth report they would have chosen a different profession had they known in advance about the extent of mistreatment they would experience. Rather than dismiss these problems as isolated events, we need to examine this issue more closely.  相似文献   
33.
Persistent otorrhea after tympanostomy tube placement in children is a common complication. Previous reports have suggested that bacteria present within the ear canal may be the cause of postoperative drainage. Preparation of the ear canal with povidone-iodine solutions has been recommended to decrease these infections. A prospective study evaluating the efficacy of povidone-iodine ear canal preparation before myringotomy and tube placement was performed in 111 children (220 ears) with documented chronic otitis media with effusion. One ear in each patient was prepared with povidone-iodine. The contralateral ear in each child was used as control. Postoperative otorrhea developed in seven (6.3%) of the treated ears within 14 days, compared to eleven (10%) of the ears in the control group. The difference was not statistically significant (p greater than 0.05). Purulent or mucoid middle ear effusions and edematous or granular middle ear mucosa were associated with a significantly higher incidence of postoperative otorrhea (p less than 0.05). This study suggests that postoperative otorrhea is generally a consequence of preoperative middle ear condition rather than contamination from the external canal. Antimicrobial therapy should be considered when purulent effusion or granulation tissue is seen.  相似文献   
34.
A quantitative model is presented which accurately reproduces the time activity curve of the human left ventricular blood pool. Four parameters receive numerical values and may be of clinical value.  相似文献   
35.
This intervention study compares the effectiveness of two approaches on caregiving stress reduction. Caregivers' psychobiological symptom experience and coping were profiled over time by identifying the types of stress-related symptoms most frequently experienced. Following pretesting (and selected matching procedures) using family functioning, coping, stress and mental status instruments, random assignment of caregivers was made to one of four groups: educative/didactic, psychotherapeutic/support, placebo, or control. Patients were tested at the end of eight weekly 2-hour sessions and again at 1-, 3-, 6-, and 12-month intervals after treatment. Although both the educative and psychotherapeutic groups were effective interventions for the reduction of strain, the psychotherapeutic/support group was the most effective over time, both at posttest and at the 3-month intervals. Neither group intervention was more effective than the control groups in reducing other types of stress, including anxiety, somatization, or depression. The psychobiological symptoms experienced by caregivers peaked at crisis periods in the caregiving trajectory, or when multiple demands were made of the caregiver during any one point in time.  相似文献   
36.
Periodic breathing cycle duration (PCD), the time interval from the beginning of one respiratory pause to the beginning of the next pause within an episode of periodic breathing (PB), was measured by examination of 24-h impedance pneumograms in 51 preterm infants. Calculations of the SD of PCD within a given PB episode (approximately 3 s) and comparison of PCD values between two PB episodes in each infant (r = 0.68) revealed considerable variability in PCD. This variability was not related to the number of cycles in the PB episode or to the amount of PB in the recording. Contrary to the decrease in PCD from 15.0 s at 1 wk to 12.4 s at 12 wk in term infants reported previously, PCD did not vary as a function of postconceptional, gestational, or postnatal age in our preterm population. PCD has limited value as an indicator of chemoreceptor maturation in the preterm infant, and most likely reflects transient adjustments in respiratory system control.  相似文献   
37.
Lynch  DA; Gamsu  G; Ray  CS; Aberle  DR 《Radiology》1988,169(3):603-607
In 260 asbestos-exposed individuals evaluated by means of computed tomography (CT), 43 unsuspected pulmonary masses were found in 27 individuals. The masses included fissural pleural plaques (n = 10), dense fibrotic bands (n = 3), round atelectasis (n = 11), carcinomas (n = 3), and other presumed benign masses (n = 16). The most helpful features in the diagnosis of rounded atelectasis with CT were (a) contiguity to areas of diffuse pleural thickening, (b) a lentiform or wedge-shaped outline, (c) evidence of volume loss in the adjacent lung, and (d) a characteristic "comet tail" of vessels and bronchi sweeping into the margins of the mass. Less advanced areas of focal atelectasis had fewer classic features. Intrafissural pleural plaques were readily identified with high-resolution CT. In asbestos-related masses, the demonstration of stability over time is necessary. Careful interpretation of CT and high-resolution CT features and close surveillance can obviate the need for biopsy in the majority of instances.  相似文献   
38.
Proteinuria in IgA nephropathy   总被引:4,自引:0,他引:4  
Clinicopathological data in 74 patients with IgA nephropathy were analyzed with special attention to level of proteinuria and its prognostic significance in this disease. Excretion rates exceeding 3 g per day (heavy), in the range of 1 to 2.9 g (moderate) and under 1 g per day (mild) each occurred in approximately equal proportions of patients. One-sixth of those with more than 1 g developed end-stage renal failure, while serum creatinine never exceeded 2 mg/dl in any with mild proteinuria. "Renal survival" (serum creatinine of 2 mg/dl or less) at five years after presentation was 100% in patients with persistently mild proteinuria, 87% in those whose protein excretion reached the moderate range, and 69% when heavy or nephrotic range proteinuria developed. Of significance, only rarely did mild proteinuria at presentation increase to higher levels. A correlation existed between level of protein excretion and severity of mesangial, segmental or global proliferation, glomerulosclerosis, podocyte effacement, interstitial infiltration, tubular atrophy and vascular sclerosis, even in patients with unimpaired renal function. Moderate or heavy proteinuria typically preceded the onset of hypertension and occurred prior to the development of renal insufficiency. Our results underscore magnitude of proteinuria as an early marker of glomerular damage in the prognosis of IgA nephropathy.  相似文献   
39.
Histamine is known to cause a substantial increase in the permeability of venules to both water and proteins. However, this increase is transient, i.e., the initially elevated permeability returns toward control levels, or "recovers," even during continuous histamine stimulation. In this investigation, we attempted to identify the possible chemical signal(s) initiating the permeability recovery process in single venules of rat mesentery. Specifically, we tested whether histamine's binding to H2 receptors and/or the production of prostacyclin by endothelial cells was involved in this process. To achieve this aim, the time course of endothelial cells was involved in this process. To achieve this aim, the time course of histamine-induced changes in permeability to alpha-lactalbumin was measured in the presence of H2 receptor antagonist (cimetidine) or of prostacyclin synthetase inhibitor (tranylcypromine), respectively. Permeability of individually perfused microvessels was measured using fluorescence microscopy. The results demonstrated that permeability recovery was not affected by the H2 receptor antagonist but was suppressed or even abolished by the prostacyclin synthesis inhibitor. Therefore, these results suggest that the production of prostacyclin by endothelial cells might serve as one chemical signal to initiate the permeability recovery process, whereas histamine's binding to H2 receptors is not involved in this phenomenon.  相似文献   
40.
The Hemopump Cardiac Assist System is a relatively new intraarterial, axial-flow circulatory assist device that offers temporary left ventricular support to patients in refractory cardiogenic shock, without requiring major surgery for insertion. Use of the Hemopump is associated with a low complication rate. Device-related morbidity is extremely rare. Because the Hemopump is safe for use in community hospitals, the number of patients supported by this device is expected to increase. In this report, we present general guidelines for the care of patients supported by the Hemopump. We describe techniques for the management of afterload reduction, supravalvular dislodgement, device malfunction, ventricular ectopy, intracardiac shunting, and inflow cannula obstruction.  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