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   2953篇
  免费   165篇
  国内免费   33篇
耳鼻咽喉   17篇
儿科学   29篇
妇产科学   184篇
基础医学   277篇
口腔科学   275篇
临床医学   278篇
内科学   632篇
皮肤病学   31篇
神经病学   277篇
特种医学   139篇
外科学   502篇
综合类   5篇
一般理论   1篇
预防医学   90篇
眼科学   43篇
药学   110篇
中国医学   1篇
肿瘤学   260篇
  2024年   12篇
  2023年   31篇
  2022年   76篇
  2021年   140篇
  2020年   88篇
  2019年   92篇
  2018年   119篇
  2017年   74篇
  2016年   93篇
  2015年   91篇
  2014年   123篇
  2013年   141篇
  2012年   222篇
  2011年   217篇
  2010年   131篇
  2009年   115篇
  2008年   179篇
  2007年   197篇
  2006年   153篇
  2005年   202篇
  2004年   142篇
  2003年   131篇
  2002年   78篇
  2001年   28篇
  2000年   27篇
  1999年   27篇
  1998年   25篇
  1997年   22篇
  1996年   23篇
  1995年   12篇
  1994年   17篇
  1993年   7篇
  1992年   10篇
  1991年   18篇
  1990年   14篇
  1989年   7篇
  1988年   6篇
  1987年   6篇
  1986年   5篇
  1985年   4篇
  1984年   8篇
  1983年   6篇
  1982年   6篇
  1981年   3篇
  1979年   4篇
  1978年   3篇
  1976年   3篇
  1975年   4篇
  1974年   3篇
  1973年   3篇
排序方式: 共有3151条查询结果,搜索用时 15 毫秒
1.
BACKGROUND: The activity and isoenzyme composition of N-acetyl-beta-D-hexosaminidase (EC.3.2.1.52) in seminal plasma of fertile and infertile men have been evaluated. However, no data are available on the isoenzyme content in seminal plasma from patients with secretory azoospermia. METHODS: The activity and isoenzyme composition of seminal plasma from 15 normozoospermic controls and 18 patients with secretory azoospermia were determined by fluorimetric methods. 4-Methylumbelliferil-2-acetamido-2-deoxy-beta-D-glucopyranoside and 4-methylumbelliferil-2-acetamido-2-deoxy-beta-D-glucopyranoside-6-sulfate were used as fluorigenic substrates. Receiver-operating characteristic (ROC) curve analysis was performed to evaluate the diagnostic efficiency of the assays. RESULTS: No significant difference was found in total enzyme activity between the two groups, while isoenzyme A activity was significantly lower (p=0.004) and the ratio between total enzyme activity and isoenzyme A activity was significantly higher (p=0.04) in azoospermic patients compared to controls. The diagnostic efficiency of these evaluations was low (< or =75.7%). CONCLUSIONS: Our findings show that the isoenzyme composition of N-acetyl-beta-D-hexosaminidase in seminal plasma from patients with secretory azoospermia is significantly different from controls, but this difference does not represent a useful marker of secretory azoospermia. The fluorimetric assays are simple and rapid methods for evaluating the isoenzyme composition.  相似文献   
2.
OBJECTIVE: To verify the feasibility and compare the results of thoracoscopic sympathectomy under local anaesthesia (LA) and spontaneous breathing vs. general anaesthesia (GA) with one-lung ventilation. METHODS: Two groups of consecutive patients underwent one stage bilateral T2-T3 thoracoscopic sympathectomy under LA (n=15) and GA (n=30) by the same surgical team for treatment of primary palmar hyperhidrosis. The groups were homogeneous for relevant demographic, physiological and clinical data, including pulmonary function. In both groups, patient's satisfaction was evaluated 24h after surgery by a simple interview and scored into five grades (1=very poor to 5=excellent), while quality of life (QOL) was evaluated by SF-36 and Nottingham's Health Profile questionnaires before and 6 months after surgery. A cost comparison between groups concerning devices, drugs, global in operating room time, medical personnel and hospital stay was also carried out. RESULTS: No operative mortality was recorded. The overall in operating room time for the whole bilateral procedure under LA was 63.55+/-10.58 vs. 86.05+/-5.75 under GA (P<0.01) and temperature increased in all patients from a baseline of 25.42+/-0.56 up to 32.15+/-0.84 degrees C. All patients undergone LA were discharged the same day after a chest roentgenogram and a short stay in the outpatient clinic. Among them three patients (20%) experienced a minimal (<30%) pneumothorax that required no treatment, while five (33.3%) had a trunk compensatory sweating that spontaneously resolved on the long run. Patients undergoing GA were discharged after a mean stay of 1.38+/-0.6 days. Among these, eight (26.6%) had prolonged trunk compensatory sweating that did not persist longer than 3 months. At a follow-up of 7.16+/-2.97 months, QOL was significantly improved with no difference between groups. The overall rate of satisfaction was greater in the LA group (P<0.05). CONCLUSIONS: In our study, awake one stage bilateral thoracoscopic sympathectomy for palmar hyperhidrosis could be safely and effectively performed as an outpatient procedure in patients refusing GA. Postoperative quality of life was equal to that in patients undergone the same procedure under GA, while patient satisfaction was better and cost were significantly reduced.  相似文献   
3.
4.
OBJECTIVE: To examine the outcomes of surgery for active infective endocarditis with paravalvular abscess. METHODS: Paravalvular abscess was defined as infective necrosis of the valve annulus that required patch reconstruction before implanting a new valve. Of 383 patients with active infective endocarditis who underwent surgical treatment, 135 (35%) had paravalvular abscess. Patients' mean age was 51+/-16 years and 68% were men. The infected valve was native in 69 patients and prosthetic in 66. The abscess involved the aortic annulus in 73 patients, the mitral annulus in 27, the aortic and mitral annuluses in 33, and the aortic and tricuspid and/or pulmonary annuluses in 2. Surgery consisted of radical resection of the abscess, reconstruction of the annulus with patches and valve replacement. Mean follow-up was 6.2+/-5.2 years and complete. RESULTS: There were 21 (15.5%) operative deaths. Preoperative shock and abscess in the aortic and mitral annuluses were independent predictors of operative death. There were 34 (25%) late deaths. Survival at 15 years was 43+/-6% for all patients, 50+/-8% for native valve endocarditis and 35+/-9% for prosthetic (p=0.41). Age by increments of 5 years and recurrent endocarditis were independent predictors of late death. There were 16 episodes of recurrent endocarditis in 15 patients, and the freedom from recurrent endocarditis was 82+/-4% at 15 years. Fifteen reoperations were performed in 14 patients. Freedom from reoperation was 72+/-9% at 15 years. CONCLUSIONS: Surgery for active endocarditis with paravalvular abscess was associated with high operative mortality, particularly in patients in shock and abscess of both mitral and aortic annuluses. Long-term survival was adversely affected by age and recurrent bouts of endocarditis.  相似文献   
5.
Abstract The purpose of this study was to determine the clinical response to local delivery of tetracycline in relation to clinical and microbiological conditions of the other teeth. 4 deep pockets were monitored in 19 subjects with multiple deep periodontal lesions and high counts of P. gingivalis. In 9 patients (XT) only 2 of the selected lesions were treated by placement of tetracycline fibers (Actisite®). while the rest of the dentition was left untreated. In the other 10 patients, all teeth were supragingivally scaled and then treated by application of polymeric tetracycline HCl containing fibers, the whole dentition was subject to full mouth scaling and root planing, and the patients rinsed with 0.2% chlorhexidine (FT). A significant reduction in mean PPD was observed in all treated sites after two months. This reduction was maintained over the following 4 months. The magnitude of the effect was significantly greater in the FT group (1.74 mm) than in the LT group (0.88 mm). The mean attachment level changes were similar after 2 months in locally and fully treated subjects. A tendency of relapse was noted for treated sites in LT patients from month 2 to 6. A level of statistical significance was not reached for this effect. Data from measurements recorded at 6 sites around all teeth in the full mouth treated patients were analyzed using multiple linear regression. This analysis showed local changes in PPD and AL were significantly and strongly correlated with the baseline value of the respective parameter at the same site. In addition, more pocket depth reduction was noted if a site was not bleeding on probing at 6 months, if the location of a site was not approximal and if the tooth was not a second molar. Sites located on second molars showed also less AL gain than sites located on other teeth. Smokers showed significantly less reduction in PPD and significantly less AL gain. Furthermore, if subjects had a high % of pockets deeper than 4 mm at baseline they showed significantly less attachment gain.  相似文献   
6.
7.
Donkeys, an endangered species, have recently gained a new application with the use of their milk to feed humans with allergic processes. The Ragusana donkey breed from Sicily is used to produce milk for humans with allergic diseases. In order to evaluate the hygienic, nutritional and management measures on a farm of Ragusana donkeys, complete blood counts, extended biochemical profiles and serum protein electrophoresis, as part of metabolic profile test (MPT), were performed in Ragusana donkeys. Fifty-four donkeys were studied and grouped according to their age, (1) 29 females and a single stallion (n=30), (2) young females, 1 – 3 years old (n=10) and (3) young of both sexes under 1 year old (n=14). The RBC count, RDW value, Lymp, and Mono counts, and PDW values were statistically greater in donkeys under one year old than in adult donkeys, while the Seg Neu count was lower. The CPK, ALP, iPhos, and HCO3, values were statistically higher in the group of donkeys under 1 year of age than adult donkeys while Cl and LDH values were statistically lower in donkeys under 1 year than adult donkeys. Additionally, statistically significant increased values for CPK, ALP, Alb, Chol, iPhos, HCO3, and UIBC in young donkeys under 1 year when compared with young donkeys, 1 – 3 years were observed. A statistically significant decreased value for Urea and an increased value for Crea in young donkeys, 1 – 3 years old were found as compared to adults. The serum protein fractions recognised by electrophoresis were: albumin, alpha globulin (subdivided into alpha-1 and alpha-2-globulins), beta globulin, and gamma globulin. In the alpha-1-globulin region three small peaks were constantly noticed, and alpha-2-globulins were statistically different between the three groups being greater in young donkeys under 1 year of age. The results obtained were used both to establish reference ranges and a data bank for the farm of Ragusana donkeys for future needs in assessing the metabolic status and health of the animals.  相似文献   
8.
The aim of the study was to evaluate the effects of transcutaneous electric nerve stimulation (TENS) on CO(2) laser evoked potentials (LEPs) in 16 normal subjects. The volar side of the forearm was stimulated by 10 Hz TENS in eight subjects and by 100 Hz TENS in the remainder; the skin of the forearm was stimulated by CO(2) laser and the LEPs were recorded in basal conditions and soon after and 15 min after TENS. Both low and high frequency TENS significantly reduced the subjective rating of heat stimuli and the LEPs amplitude, although high frequency TENS appeared more efficacious. TENS seemed to exert a mild inhibition of the perception and processing of pain induced by laser Adelta fibres activation; the implications of these effects in the clinical employment of TENS remain to be clarified.  相似文献   
9.
Apoptosis is a key phenomenon in the regulation of the life span of terminally differentiated leukocytes. Human gingiva represents an established model to study immune responses to bacterial infection. In this investigation, we used the TUNEL (terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling) technique to evaluate presence and topographic location of apoptosis-associated DNA damage in human gingival biopsies along with the expression of the p53 and Bcl-2 apoptosis-regulating proteins. Qualitative data analysis showed high densities of cells expressing DNA damage and p53 both within the epithelial attachment to the tooth and in the perivascular infiltrate (infiltrated connective tissue [ICT]) immediately underlying the site of chronic bacterial aggression. Topographic consistency between DNA damage- and p53-positive cells was consistently observed. Quantitative analysis of the ICT showed mean densities of DNA damage- and p53-positive cells of 345 ± 278 and 403 ± 182 cells/mm2, respectively. Numerical consistency was confirmed by multivariate regression analysis: densities of DNA damage-positive cells were significantly predicted by densities of p53-positive cells (P = 0.001, r2 = 0.84). In the ICT, cells displaying biotinylated DNA nicks were 3.8% ± 2.7% of total cellularity, while p53- and Bcl-2-positive cells represented 4.4% ± 1.7% and 15.4% ± 6.7% of total cells, respectively. It is suggested that p53 expression associated with DNA damage is a prevalent phenomenon in chronically inflamed human gingiva, and that apoptosis may be a relevant process for the maintenance of local immune homeostasis at sites of chronic bacterial challenge in vivo.  相似文献   
10.
BACKGROUND: Oxidative stress mechanisms are involved in the pathophysiology of many reproductive disorders. The objective of this study was to characterize oxidative stress parameters in hydrosalpingeal fluid (HSF) and examine their possible role in early embryo development. METHODS AND RESULTS: HSF was aspirated at laparoscopic salpingectomy in 11 infertile women. Reactive oxygen species (ROS), total (non-enzymatic) antioxidant capacity (TAC) and lipid peroxidation (LPO) were assayed. Two-cell mouse embryos were incubated with 25, 50 or 75% HSF and the blastocyst development rate was observed. ROS was detected in five of 11 (45%) HSF samples with a mean of 4.2 x 10(4) c.p.m. LPO was detected in all samples at a mean (+/- SD) value of 5575.4 +/- 6091.9 micromol/l malonaldehyde. The mean blastocyst development rate at 25, 5+/- 0 and 75% HSF and in the control group was 88.9 +/- 9.4, 65.7 +/- 19.1, 45.7 +/- 5.7 and 96.7% respectively (P < 0.0001). The blastocyst development rate was positively correlated to ROS concentrations (P < 0.02) but was not significantly related to LPO. CONCLUSIONS: The blastocyst development rate decreased with increasing concentrations of HSF. For the first time, the presence of ROS, LPO and TAC activity in human HSF was characterized. A possible role of oxidative stress in the embryotoxicity of HSF is suggested.  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