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   10520篇
  免费   1143篇
  国内免费   26篇
耳鼻咽喉   73篇
儿科学   352篇
妇产科学   354篇
基础医学   1515篇
口腔科学   186篇
临床医学   1155篇
内科学   2128篇
皮肤病学   103篇
神经病学   797篇
特种医学   550篇
外科学   1461篇
综合类   332篇
一般理论   7篇
预防医学   1097篇
眼科学   106篇
药学   863篇
中国医学   4篇
肿瘤学   606篇
  2021年   145篇
  2020年   101篇
  2019年   146篇
  2018年   149篇
  2017年   136篇
  2016年   126篇
  2015年   168篇
  2014年   247篇
  2013年   345篇
  2012年   473篇
  2011年   514篇
  2010年   279篇
  2009年   263篇
  2008年   425篇
  2007年   438篇
  2006年   435篇
  2005年   417篇
  2004年   398篇
  2003年   386篇
  2002年   379篇
  2001年   321篇
  2000年   338篇
  1999年   309篇
  1998年   167篇
  1997年   158篇
  1996年   164篇
  1995年   128篇
  1994年   138篇
  1993年   131篇
  1992年   233篇
  1991年   260篇
  1990年   226篇
  1989年   217篇
  1988年   233篇
  1987年   246篇
  1986年   225篇
  1985年   217篇
  1984年   170篇
  1983年   150篇
  1982年   105篇
  1981年   105篇
  1979年   109篇
  1978年   94篇
  1977年   87篇
  1976年   82篇
  1975年   88篇
  1973年   89篇
  1972年   85篇
  1971年   77篇
  1970年   72篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
161.
The Diagnosis Related Group (DRG) classification system is widely used to describe the casemix of acute care hospitals, making it possible to compare the casemix of hospitals from different countries. However, in order to fully understand these comparisons, it is necessary to clarify the impact which the different coding systems used in various countries may have had on the results. The DRG system is based on codes from the International Classification of Diseases 9th Revision Clinical Modification (ICD9CM). Countries which use other coding systems convert, i.e. map, their codes into the nearest ICD9CM equivalent before allocating the DRGs. The impact of mapping on both medical and surgical DRGs is discussed and new titles are given for the affected DRGs. As far as possible, problems caused by mapping are distinguished from those caused by differences in coding practices. Based on the analysis of the classification systems, the mapping tables and the resulting DRG data, it is concluded that using mapped data does not have a great impact on the DRGs. Only 37 DRGs (7.8%), 15 medical and 22 surgical classes, are affected by mapping problems. However, while the scale of these problems is not large, given the large number of different surgical classification systems currently in use in Europe, the introduction of a standard surgical classification system for Europe is recommended.  相似文献   
162.
Acute intravenous prazosin (0.05 mg/kg) caused marked falls in mean arterial pressure and postsynaptic alpha 1-adrenoceptor blockade in rabbits. During chronic oral dosing (3--21 days), tolerance developed and blood pressure returned to base-line pretreatment levels. This did not appear to be related to changes in plasma renin activity, body weight, prazosin kinetics, or alpha 2-adrenoceptor responsiveness. However, pressor responses to the alpha 1-adrenoceptor agonist phenylephrine and the mixed alpha 1/alpha 2-agonist noradrenaline increased during chronic prazosin therapy. Despite the development of apparent "tolerance," the response to bolus injections of prazosin was unchanged. No changes in the maximum number of prazosin binding sites or their dissociation constant were observed in the heart, spleen, forebrain, or hindbrain after 21 days treatment. It appears that although compensatory mechanisms develop during chronic prazosin treatment, they are not mediated by alterations in alpha 1-receptor binding but are related to changes in alpha 1-adrenoceptor responsiveness beyond the drug-receptor binding site.  相似文献   
163.
To evaluate the risk of definitive intracranial microsurgical aneurysm obliteration as a function of the timing of the operative intervention, we retrospectively reviewed 106 consecutive patients in good clinical condition who underwent such surgery. The patients who were operated upon within the first 8 days of their most recent subarachnoid hemorrhage formed the "early" group; the patients operated upon between the 9th and 31st day were considered to have undergone "late" surgery. On the basis of their clinical outcome the patients were allocated to one of four outcome categories ("good," "fair," "death") both at the time of their hospital discharge and at their most recent clinical re-evaluation, a minimum of 6 months after discharge from the hospital. There was no significant difference in the operative mortality in each group (early surgery, 5%; late surgery, 4%); additionally, no significant difference was noted in the incidence of either intraoperative complications or postoperative morbidity. A suggestive but statistically insignificant increase in the incidence of postoperative cerebral ischemic events was seen in the "early" surgery group (8% vs. 4% for the "late" surgery group). The potential significance of these findings for the timing of intracranial aneurysm surgery is discussed.  相似文献   
164.
1 The cardiovascular effects of bromocriptine, a dopamine receptor agonist, were investigated in twenty-eight Parkinsonian patients.

2 Bromocriptine caused a significant impairment of postural compensation with a fall in systolic pressure and an absence of the rise in diastolic pressure after standing for 1 min when patients taking active drug were compared to the same patients on placebo. The hypotensive effect persisted for at least 6 weeks of treatment. There was also a significant reduction in supine heart rate.

3 One patient had marked falls in supine and erect blood pressure after a single oral dose of bromocriptine (2.5 mg) and a further patient developed paroxysmal atrial tachyarrhythmias. Both blood pressure and heart rate changes reversed spontaneously after stopping bromocriptine.

4 It is proposed that dopaminergic mechanisms either in the central nervous system or the periphery contribute to cardiovascular regulation in man.

  相似文献   
165.
Two studies assessed the relation between ADHD symptomatology and correlates of cerebral dominance. In the first, laterality was examined in school children (N=57), 28 with ADHD. Parental reports of greater attentional symptoms were related to non-righthandedness, but teacher reports were related to anomalous laterality of foot, ear and eye, as well as hand. This suggests that the previously reported association between ADHD and non-righthandedness may not be unique, but instead indicative of a more general condition of anomalous lateralization. This possibility was examined in study two, in which 234 undergraduates were assessed. As expected, the 26 adults identified by the Wender Utah Rating Scale (WURS) as retrospectively reporting more ADHD characteristics were found to be generally male. Also, in a replication of study one, enhanced WURS scores were associated with anomalous lateralization beyond handedness. In this case, ADHD characteristics were associated with a shift away from a right bias for hand, foot, and ear, but not eye. Factor analysis of the extensive Steenhuis and Bryden handedness questionnaire was then undertaken to determine whether all aspects of handedness, or only a subset, are associated with ADHD. The factor analysis indicated that the retrospective reports of ADHD characteristics were associated with only two of the three dimensions. Though limitations such as the gender composition of the groups in study one tempers the conclusions, the results of both studies support previous findings that ADHD is associated with anomalous laterality, but also indicate that non-righthandedness is not an adequate characterization of this relationship.  相似文献   
166.
BACKGROUND AND PURPOSE: Stroke patients in western countries frequently have coronary artery disease (CAD). In black Africans, CAD has been reported as being rare in both stroke patients and the general population. In this study, an attempt has been made to determine the prevalence of CAD in a black South African stroke population. METHODS: The prevalence of CAD was determined by indicators identified through a series of 5 observational studies in black patients diagnosed with stroke. CAD indicators included (1) bedside diagnosis in 741 patients; (2) resting ECG in 555 consecutively admitted patients; (3) a combination of clinical examination, cardiac ultrasound, radionuclide scintigraphy, and multigated blood pool studies in 102 consecutively admitted patients; (4) thallium scintigraphy in 60 patients; and (5) necropsy in 23 patients. RESULTS: On bedside questioning, only 0.7% complained of previous angina. There was no history given of myocardial infarction (MI), but documentation of this was found in the clinical notes of 0.7% of the patients. In the resting ECG study, evidence of myocardial ischemia was present in 14.6% and MI in 2.1%. In the combined study, cardiac ischemia was documented on ECG in 12.7% of patients and evidence of previous MI in 5.8%. Cardiac scintigraphic studies revealed changes of myocardial ischemia in 31.7% and MI in 13.3% of the 60 patients studied. Four (17.4%) of 23 patients in the necropsy study had histological evidence of previous MI, and 50% of all patients had evidence of >50% atherosclerotic stenosis in 1, 2, or 3 coronary arteries. CONCLUSIONS: The prevalence of CAD in black African stroke patients is significantly higher than has been documented in the general nonstroke black population as well as in stroke patients. Black stroke patients may have a risk for CAD similar to that of their white counterparts.  相似文献   
167.
Hazard RG  Reid S  Haugh LD  McFarlane G 《Spine》2000,25(11):1419-1423
STUDY DESIGN: Randomized controlled trial. OBJECTIVE: To test the ability of an educational pamphlet to improve recovery in terms of pain, work status, and health care utilization after occupational low back injury. BACKGROUND: Low back pain and disability persist as occupational health problems of epidemic proportions. Because interventions based on biomechanical models have had limited impact, recent educational approaches to preventing back problems have stressed psychosocial recovery issues. METHODS: A pamphlet was developed by compiling activity resumption, self-care, and attitudinal advice from recent publications. The pamphlet was sent at random to half of all consenting workers reporting back pain within 11 days of occupational injury between 7/96 and 6/97. Three and 6 months later, back pain, work status, health care use, and pamphlet impact outcomes were assessed through structured telephone interviews. RESULTS: Of the 726 eligible workers, 486 consented to participate. Consenters and nonconsenters and intervention and control groups were similar in initial demographic variables. The pamphlet had no statistically significant impact at the 0.05 significance level on pain severity or reduction, health care visits, or work absence. Of the 229 pamphlet recipients, 129 thought it had provided useful information, but only 25 thought it had helped them return to work more quickly. CONCLUSIONS: In this trial, a pamphlet stressing psychosocial recovery issues did not prevent or reduce postinjury pain, health care use, or work absence.  相似文献   
168.
Intensive care medical and nursing staff self-rate their communication skills as improved following attendance at the European Donor Hospital Education Programme (EDHEP) workshop. A prospective study was conducted to determine what impact EDHEP has on communication skills. Doctor-nurse pairs from 10 experimental and 10 control Intensive Care Units undertook two standardized simulated relative encounters (Breaking Bad News and Donation Request) at three measurement points (pre, post and follow-up). Nurses showed no change in communication skills. Experimental group doctors showed significant improvement in breaking bad news and requesting donation; most of these improvements were not maintained. Control group doctors showed some improvement in breaking bad news, indicating that participating in measurement by itself initiates some transient change in communication skills. Attendance at EDHEP does lead to significant improvement in some, but not all, communication skills essential in breaking bad news and requesting donation. Further research is necessary to determine what factors additional to EDHEP will contribute to enduring change in these particular skills.  相似文献   
169.
The ability of three Lactobacillus strains to inhibit the adhesion and growth of naturally occurring uropathogens on silicone rubber was investigated in human urine. The importance of biosurfactant production by Lactobacillus in discouraging uropathogen growth was determined in relation to the binding affinities of the lactobacilli for silicone rubber. L. fermentum B54 markedly inhibited uropathogen growth on the silicone rubber disks after 8 days for all five men included in the study, albeit to various extents ranging from 77% to 100%. In urine from women, however, this inhibition was less clear, as it was absent for two of the four women participating in this study. L. casei rhamnosus 36 completely discouraged uropathogen growth on the disks after 8 days for three of the four women, whereas its effect in urine from men was less pronounced (inhibition ranged from 48% to 100% and was absent for one man). L. casei rhamnosus ATCC 7469T was the least inhibitory Lactobacillus strain tested and inhibition was absent for a number of both male and female participants, possibly as a result of the low binding affinity of this strain for silicone rubber and of its inability to release biosurfactants. We conclude that the inhibition of uropathogen growth is dependent on the Lactobacillus strain involved, and for L. fermentum B54 it was demonstrated to be sex-related. Hence, inhibition must be considered a multifactorial process.  相似文献   
170.
Colorectal adenomatous polyps are considered to be the precursor lesion of colorectal cancer (1-3). Greater understanding of the association between smoking and adenoma development enable better detection and prevention of colorectal cancer. This study was conducted in men and women, ages 40-80, participating in a randomized trial testing the effects of wheat bran fiber supplement on adenoma recurrence. First, we investigated smoking exposure (status, cigarettes/day, and years of smoking) and colorectal adenoma characteristics (location, histology, size, and multiplicity) at baseline colonoscopy (n = 1429). Second, we evaluated smoking exposure and adenoma recurrence (n = 1304). The prevalence of distal versus proximal adenomas was greater for < or =30 cigarettes/day [odds ratio (OR), 1.48; 95% CI, 1.02-2.16] and 15 to <25 years of smoking (OR, 1.95; 95% CI, 1.23-3.09) compared with never smokers. Tubular versus villous histology prevalence was increased for > or =30 cigarettes and > or =35 years of smoking (OR, 1.74; 95% CI, 1.21-2.49 and OR, 1.74; 95% CI, 1.24-2.45, respectively) compared with never-smokers. Years of smoking increased prevalence of multiple versus single adenomas, whereas cigarettes/day and years of smoking were associated with large adenomas (> or =1 cm) prevalence as compared with small lesions (< or =0.5 cm). Greater than 35 years of smoking was significantly associated with an increased risk of adenoma recurrence (OR, 1.42; 95% CI, 1.01-1.98). These results suggest that the association between smoking and adenoma prevalence varies by the characteristic of the lesion. Furthermore, the association between smoking and adenoma recurrence is modest and was only significant after a long duration of exposure. Additional investigations that characterize the genetic changes in specific subgroups of prevalent and recurrent adenomas associated with smoking exposure are needed.  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