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   31078篇
  免费   2656篇
  国内免费   495篇
耳鼻咽喉   194篇
儿科学   1035篇
妇产科学   500篇
基础医学   2348篇
口腔科学   726篇
临床医学   4100篇
内科学   4716篇
皮肤病学   169篇
神经病学   2554篇
特种医学   1438篇
外国民族医学   1篇
外科学   3042篇
综合类   3108篇
现状与发展   1篇
预防医学   5529篇
眼科学   236篇
药学   1818篇
  44篇
中国医学   596篇
肿瘤学   2074篇
  2024年   104篇
  2023年   639篇
  2022年   1125篇
  2021年   1621篇
  2020年   1518篇
  2019年   1379篇
  2018年   1343篇
  2017年   1225篇
  2016年   1128篇
  2015年   1096篇
  2014年   2035篇
  2013年   2251篇
  2012年   1666篇
  2011年   1882篇
  2010年   1403篇
  2009年   1563篇
  2008年   1507篇
  2007年   1480篇
  2006年   1156篇
  2005年   948篇
  2004年   805篇
  2003年   684篇
  2002年   551篇
  2001年   475篇
  2000年   425篇
  1999年   360篇
  1998年   357篇
  1997年   323篇
  1996年   274篇
  1995年   281篇
  1994年   244篇
  1993年   241篇
  1992年   218篇
  1991年   176篇
  1990年   183篇
  1989年   178篇
  1988年   170篇
  1987年   107篇
  1986年   119篇
  1985年   154篇
  1984年   135篇
  1983年   105篇
  1982年   124篇
  1981年   85篇
  1980年   58篇
  1979年   61篇
  1978年   60篇
  1977年   45篇
  1976年   45篇
  1975年   25篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
Mesial temporal sclerosis and volumetric investigations   总被引:2,自引:0,他引:2  
Volumetric MRI data acquisition permits reliable and accurate measurement of mesial temporal lobe structures. In normal subjects, these structures are very symmetric. A high degree of pathological specificity is associated with the finding of even minor volume asymmetries. Definition in this manner allows precise estimation of both absolute and relative volume differences, and precise anatomical localisation of volume loss within the hippocampus. There are good EEG and clinical correlates with the distribution of volume loss defined on MRI studies. Volumetric assessment is fast, reliable, non-invasive, and a relatively inexpensive component of the pre-operative work-up. It is the method of choice when imaging patients with clinical temporal lobe epilepsy undergoing pre-surgical evaluation. The finding of significant hippocampal volume asymmetry in a patient with clinical temporal lobe seizures being evaluated for epilepsy surgery may obviate the need for alternative sophisticated, invasive, or expensive investigative procedures. At our centre, such MRI allows "fast track" cases to proceed to surgery without further invasive investigations, and is likely to have a dramatic effect on pre-operative evaluation in most centres practising epilepsy surgery.  相似文献   
32.
Summary The growth of fetal kidney volume was studied in 290 specimens taken from 145 fresh human fetuses (85 males and 60 females) with gestational age ranging from 13 to 36 weeks postconception (WPC). Normative equations and curves of the growth of renal volume were obtained for male and female fetuses and for the whole sample in the second trimester (13–24 WPC) and in the third trimester (25–36 WPC) of gestation. There was no difference between the growth in volume of the right and left kidneys. Fetal kidney volume increases with a more intense rhythm in the early fetal period (13–24 WPC). During the second trimester, there was no difference between the values for renal volume of male and female fetuses. In the third trimester, male fetuses had renal volumes significantly greater than the female fetuses. The normative parameters of renal volume could have practical applications in detection and monitoring of renal anomalies in fetal and perinatal urology.Supported by grants 302, 369/86.4/BM-FV from the National Conucil of Scientific and Technological Development (CNPq, Brazil) and Grant E.29/170.787/89 from the Rio de Janeiro Foundation for Research Support (FAPERJ).  相似文献   
33.
34.
The effect of acute and sequential volaemic changes on the gastroduodenal flow of saline was assessed in 23 anaesthetized dogs following two different experimental protocols. Hypervolaemia, by i. v. infusion of saline, induced a gradual decrease on gastroduodenal flow which amounted to 76% below control values (P < 0.001) when volaemic expansion attained 5% of body weight. This effect was volume dependent (17% increase on gastroduodenal flow per volume of infused saline equivalent to 0.5% of body weight, P < 0.001), lasted for at least 90 minutes after infusion was completed and was also obtained by expanding previously bled animals. Hypovolaemia due to bleeding was followed by an increase on gastroduodenal flow of about 88% above control values (P < 0.05) when haemorrhage was equal to 3% of body weight. This effect was also volume dependent (23 % increase on gastroduodenal flow per volume of blood shed equivalent to a 0.5% of body weight, P < 0.01) and was reversed after blood volume was restored. These modifications in the resistance of the gastroduodenal segment to the flow of liquid due to acute volaemic changes suggest that the extracellular fluid volume modulates the contractile activity of the gastroduodenal portion of the gut possibly to set a gastroduodenal handling of liquid adequate to cope with volaemic imbalances.  相似文献   
35.
Macran  S.  Kind  P.  Collingwood  J.  Hull  R.  McDonald  I.  Parkinson  L. 《Quality of life research》2003,12(2):177-188
This study reports on the preliminary testing of a new measure designed for use alongside EQ-5D in evaluating outcomes in podiatry: the Podiatry Health Questionnaire (PHQ). Individuals aged 18 years or more, receiving podiatry services in clinic or domicilliary locations across four NHS Trusts in Yorkshire and Humberside UK took part in a questionnaire survey. Respondents reported high levels of problems on all six PHQ dimensions. Correlations suggested that the PHQ and EQ-5D were measuring distinct constructs. The levels on each dimension were well defined in terms of self-rated morbidity on the PHQ visual analogue scale (PHQvas) and the EQ-5Dvas, although PHQvas appeared to be slightly more sensitive to changes in health on the dimensions. There was a strong relationship between clinicians' Podiatry Clinical Score rating and reported symptoms for four out of six PHQ dimensions and PHQvas. The PHQ was able to distinguish respondents in terms of their self-reported morbidity in EQ-5D and in terms of their morbidity as assessed by clinicians. It is suggested that the respondent completed PHQ appears to be a useful new measure for assessing foot-related health. However, further investigation of the psychometric properties of the measure is required.  相似文献   
36.
Frozen shoulder is said to be a self-limiting entity but full recovery often takes more than 2 years. For that, most patients are unwilling to tolerate painful restriction while awaiting resolution. We prospectively investigated 30 patients (16 women, 14 men) for the outcome of arthroscopic capsular release in idiopathic frozen shoulder. Results were determined by the assessment of subjective and objective parameters to estimate both shoulder function and general health status. Symptoms persisted without improvement for a minimum of 6 months of conservative treatment. Preoperative average American shoulder and elbow surgeons score (ASES) was 35, visual analog scale (VAS) to measure pain was 7, and simple shoulder test (SST) was 4. Mean scores of the physical component of SF-36 were considerably reduced. Mean forward elevation was 85°, average abduction was 70°, mean internal rotation was 15°, and mean external rotation was 10°. Patients were followed-up at 6 weeks, 3, 6, 12 months and by a mean of 36 months. Range of motion for all planes improved (P < 0.05). Median VAS reduced to 2, average ASES increased to 91, and SST enhanced to a mean of 10 (P < 0.05). We stated improvement of the physical components in the SF-36 questionnaire in particular bodily pain and the role-physical score. There were no significant differences between the measurements in the early postoperative phase compared to the mid-term follow-up (P > 0.05). Our results demonstrate that arthroscopic release of refractory idiopathic frozen shoulder combined with a gentle manipulation provides reliable expectations for improvement in both clinical and general health status for most patients. We recommend the use of a limb-specific and a general-health-status questionnaire to conclude the benefit of the surgical intervention and contribute the optimization of a therapy concept more effectively.  相似文献   
37.
Despite decreasing mortality rates, morbidity is still high after pancreatic head resection. Comparative data in the United States and Europe show a relationship between hospital volume and mortality. Treatment strategies vary frequently, partially because of the lack of evidence-based data. We performed a multi-institutional analysis in Germany evaluating current numbers, indications, techniques, and complication rates of pancreatic head resection. Questionnaires were completed by seven high-volume surgical departments regarding quantitative and qualitative aspects of pancreatic head resections in the period from 1999 to 2004 (five prospective and two retrospective institutional databases). A total of 1454 pancreatic head resections (944 for malignancy) were reported. Mean annual hospital volume ranged from 14 to 52 (10 to 43 in malignancy). Mortality was between 1.1% and 4.8%, morbidity was between 24% and 46%, and pancreatic leakage was between 9% and 20%. In malignant disease, all centers perform standard lymphadenectomy and regard arterial infiltration as a contraindication for resection. However, the rate of portal vein resection varied from 0% to 28%. No consensus is seen on the type of surgery for malignancy and chronic pancreatitis. After resection for pancreatic cancer less than one fourth of the patients receive adjuvant therapy. The results of our analysis in Germany confirm that pancreatic head resection can be performed with low mortality in specialized units. Variations in indications, operative technique, and perioperative care may demonstrate the lack of evidence-based data and/or personal and institutional experience. The low number of patients receiving adjuvant therapy after resection of pancreatic cancer suggests that more efforts must be made to establish novel adjuvant therapies under randomized study conditions. Presented at the Forty-Sixth Annual Meeting of The Society for Surgery of the Alimentary Tract, Chicago, Illinois, May 14–18, 2005 (oral presentation).  相似文献   
38.
PURPOSE: To evaluate the effects of dissolvable collagen punctal plugs on the symptoms, tear stability and volume in aqueous deficient dry eyes. METHODS: Sixty-two aqueous deficient dry eye patients of mixed aetiology underwent lacrimal punctal occlusion with dissolvable collagen plugs. The subjects were randomly allocated to one of two treatment groups: group I (n = 36) had their lower puncta occluded and group II (n = 26) had both their upper and lower puncta occluded. The effectiveness of this treatment was clinically assessed by (1). scoring subject symptoms and (2). measuring the tear parameters of tear thinning time (TTT) and tear meniscus height (TMH) as indicators of tear stability and volume, respectively. Following baseline measurements, patients were reviewed at time intervals of 5 and 12 days post-occlusion. A group of age- and gender-matched normals (n = 45) was recruited for comparison (group III). RESULTS: Tear volume and stability were significantly higher in group III compared with I and II at baseline. In the treated groups on both days 5 and 12: (1). symptom score reduced significantly from a median value of 7 to 3 (p = <0.001); (2). tear stability increased significantly from a median value of 3 to 5 s by day 5 (p 相似文献   
39.
The relationship between primary tumor proliferative activity and clinical and pathologic characteristics was analyzed in relation to menopausal status in 32 patients with malignant or benign breast disease. The thymidine labeling index (TLI) showed significantly higher median values in the cancer patients (3.48 per cent) than in the patients with benign diseases (1.02 per cent). TLI was not significantly affected by delayed incubation at room temperature for about 1 hour. In the breast cancer patients, TLI did not significantly correlate to tumor size, the presence of axillary lymph node metastasis or pathologic nuclear grading. The only significant difference was limited to the breast cancer patients without axillary lymph node metastasis in relation to menopausal status; the TLI in the premenopausal patients (5.10 per cent) was significantly higher (p<0.05) than that in the postmenopausal patients (2.28 per cent). These data thus suggest that among premenopausal patients without axillary lymph node metastasis, those with a high TLI could be potential candidates for adjuvant chemotherapy.  相似文献   
40.
Background: Studies have shown that socioeconomic groups differ in their dietary behaviours, and it has been suggested that these differences partly account for health inequalities between social groups. To-date, however, we have a limited understanding of why socioeconomic groups differ in their dietary behaviours. This paper addresses this issue by examining the relationship between socioeconomic status, food preference (likes and dislikes) and the purchase of 'healthy' food (i.e. food consistent with dietary guideline recommendations). Methods: This study was based on a dual-sample, dual-method research design. One sample was systematically selected from the Australian Commonwealth electoral roll and the data collected using a mail-survey methodology (81% response rate, n =403). The second consisted of a convenience sample of economically disadvantaged people recruited via welfare agencies (response rate unknown, n =70). A mail survey methodology was deemed inappropriate for this sample, so the data were collected by personally delivering the questionnaire to each respondent. Results: Socioeconomic groups differed significantly in their food purchasing choices and preferences. The food choices of respondents in the welfare sample were the least consistent with dietary guideline recommendations, and they reported liking fewer healthy foods (all results were independent of age and sex). Notably, socioeconomic differences in preference explained approximately 10% of the socioeconomic variability in healthy food purchasing behaviour. Conclusion: Whilst it is not clear why socioeconomic groups differ in their food preferences, possible reasons include: reporting bias, differential exposure to healthy food as a consequence of the variable impact of health promotion campaigns, structural and economic barriers to the procurement of these foods, and subculturally specific beliefs, values, meanings, etc.  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