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   20767篇
  免费   1124篇
  国内免费   112篇
耳鼻咽喉   222篇
儿科学   414篇
妇产科学   454篇
基础医学   2676篇
口腔科学   577篇
临床医学   1625篇
内科学   5571篇
皮肤病学   515篇
神经病学   1860篇
特种医学   508篇
外科学   3202篇
综合类   106篇
现状与发展   1篇
一般理论   4篇
预防医学   1523篇
眼科学   391篇
药学   1037篇
中国医学   43篇
肿瘤学   1274篇
  2023年   164篇
  2022年   368篇
  2021年   804篇
  2020年   349篇
  2019年   700篇
  2018年   807篇
  2017年   463篇
  2016年   474篇
  2015年   555篇
  2014年   757篇
  2013年   1066篇
  2012年   1725篇
  2011年   1633篇
  2010年   944篇
  2009年   879篇
  2008年   1381篇
  2007年   1411篇
  2006年   1325篇
  2005年   1305篇
  2004年   1055篇
  2003年   996篇
  2002年   943篇
  2001年   122篇
  2000年   72篇
  1999年   133篇
  1998年   145篇
  1997年   139篇
  1996年   116篇
  1995年   119篇
  1994年   99篇
  1993年   84篇
  1992年   68篇
  1991年   65篇
  1990年   45篇
  1989年   39篇
  1988年   35篇
  1987年   37篇
  1986年   38篇
  1985年   42篇
  1984年   39篇
  1983年   23篇
  1982年   29篇
  1981年   40篇
  1980年   26篇
  1979年   33篇
  1978年   34篇
  1977年   22篇
  1976年   28篇
  1975年   19篇
  1974年   23篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
The outcome of ischemic acute renal failure (IARF) is better in young than adult rats. Insulin-like growth factor I (IGF-I) treatment may increase mortality of adult rats with IARF, probably because of an exaggerated inflammatory response. We report the response to IGF-I therapy in young rats with IARF. Male rats, aged 28+/-1 days, with IARF were given subcutaneous IGF-I, 50 microg/100 g at 0, 8, and 16 h after reperfusion (IGF) or were untreated (ARF). Sham-operated rats were used as controls. At 2 and 7 days after ischemia, serum urea nitrogen and histological damage score, cell proliferation, apoptosis, neutrophil infiltration, and IGF-I receptor mRNA in kidneys were analyzed. The degree of renal failure, mortality rate, histological damage, cell proliferation, and neutrophil infiltration were not different between IGF-I and ARF rats. Hence, short-term IGF-I treatment did not modify the course of IARF in young rats.  相似文献   
992.
STUDY OBJECTIVE: To compare postoperative nausea, emesis, analgesia, and recovery between propofol-ketamine and propofol-fentanyl in outpatient laparoscopic tubal ligations with general anesthesia. STUDY DESIGN: Prospective, randomized, blinded study. SETTING: Tertiary-care women's hospital. PATIENTS: 120 ASA physical status I and II ambulatory patients scheduled for elective laparoscopic tubal ligation. INTERVENTIONS: Patients were randomized to two groups to receive either ketamine (1-1.5 mg/kg) or fentanyl (3-5 microg/kg). MEASUREMENTS: Measured variables included total dose of ketamine, fentanyl, propofol, and operating time. Vital signs, pain visual analog scale scores (VAS), nausea VAS, presence of emesis, treatment for nausea and vomiting, pruritus, sedation, and presence of dreaming were recorded on postanesthesia care unit (PACU) admission, PACU discharge, stepdown unit admission, and hospital discharge. Results are expressed as means +/- SD or medians and analyzed using t-test, Chi-square, or Mann-Whitney (p < 0.05). MAIN RESULTS: No differences were noted with respect to propofol dose, operating times, pain or nausea VAS scores, emesis, treatment for nausea and vomiting, pruritus, and sedation on PACU admission, PACU discharge, stepdown unit admission, and hospital discharge. The ketamine group had a higher heart rate, required more pain medication, and had a higher frequency of dreaming on PACU admission than the fentanyl group. These differences became insignificant on PACU discharge. CONCLUSIONS: For outpatient laparoscopic tubal ligations with general anesthesia, propofol-ketamine does not improve postoperative nausea, emesis, analgesia or recovery compared with the propofol-fentanyl combination.  相似文献   
993.
PURPOSE: To determine changes in keratocyte density in the first year after laser in situ keratomileusis (LASIK). DESIGN: Prospective interventional cohort study. METHODS: Seventeen eyes of 11 patients received LASIK with a planned 180-microm flap to correct refractive errors between -2.0 diopters and -11.0 diopters. Images of the full-thickness cornea were obtained by using confocal microscopy in vivo before LASIK and at 1 week, 1, 3, 6, and 12 months after LASIK. Bright objects (that resembled keratocytes) in images without motion blur were manually counted by one observer. Cell densities were determined in anterior and posterior halves of the stromal flap, anterior and posterior halves of the layer 100 microm-thick immediately deep to the ablation (retroablation layer), and in the posterior third of the stroma. The region of stroma that was ablated (as measured 1 month after LASIK) was omitted from the preoperative analysis. RESULTS: Keratocyte density in the anterior flap was 28,978 +/- 5849 cells/mm(3) (mean +/- SD) pre-LASIK, and was decreased at all postoperative examinations, but the difference was not significant until 12 months after LASIK (22% decrease). Keratocyte densities in the posterior flap were 20,397 +/- 4215 cells/mm(3) pre-LASIK and were decreased by 20%-40% at all postoperative examinations 1 week to 1 year after LASIK. Keratocyte densities in the anterior half of the retroablation layer were 16,605 +/- 3595 cells/mm(3) pre-LASIK and decreased by 16%-30% between 3 and 12 months after LASIK. Keratocyte densities in the posterior half of the retroablation layer and posterior stroma did not change. CONCLUSIONS: Keratocyte densities in the posterior flap and anterior retroablation layer (regions adjacent to the lamellar cut) decrease at 1 week and 3 months, respectively, after LASIK and remain decreased in these regions at 12 months after LASIK. In the anterior flap, keratocyte density decreases 1 year after LASIK. The long-term effects of these cellular deficits, if any, require further study.  相似文献   
994.
PURPOSE: To determine changes in central epithelial and stromal thickness in human corneas in vivo after laser in situ keratomileusis (LASIK). DESIGN: Prospective, nonrandomized, comparative trial. PARTICIPANTS: Eighteen eyes of 12 patients received LASIK (performed using the VISX Star laser [VISX, Santa Ana, CA]) with a planned 180- micro m flap (created using an automated Hansatome microkeratome [Bausch & Lomb, Irvine, CA]) to correct refractive errors between -2.0 diopters (D) and -11.0 D. METHODS: Corneas were examined by using confocal microscopy in vivo before LASIK and at 1 week and 1, 3, 6, and 12 months after LASIK. Epithelial thickness was the distance between images of the surface epithelium and subbasal nerve plexus or, when nerves were not visible, the subbasal peak (if present in the light intensity profile). Total flap thickness was the distance between images of the surface epithelium and interface debris (or peak), and total stromal thickness was the distance between images of the most anterior keratocytes and endothelium. MAIN OUTCOME MEASURES: Corneal epithelial and stromal thickness. RESULTS: Epithelial thickness before LASIK was 46 +/- 5 micro m (mean +/- standard deviation) and increased 22% by 1 month after LASIK (56 +/- 5 micro m; P = 0.01). Thereafter, epithelial thickness did not change, but remained thicker at 12 months after LASIK (54 +/- 8 micro m) than before LASIK (P = 0.02). Total flap thickness at 1 month after LASIK was 160 +/-28 micro m and did not change thereafter. Changes in total stromal thickness between 1 and 12 months after LASIK were not significant. CONCLUSIONS: The central corneal epithelium was thicker in the first year after LASIK than before LASIK. There was no change in central stromal thickness between 1 month and 12 months after LASIK.  相似文献   
995.
PURPOSE: The authors sought to quantify neighboring and distant interpoint correlations of threshold values within the visual field in patients with glaucoma. METHODS: Visual fields of patients with confirmed or suspected glaucoma were analyzed (n = 255). One eye per patient was included. Patients were examined using the 32 program of the Octopus 1-2-3. Linear regression analysis among each of the locations and the rest of the points of the visual field was performed, and the correlation coefficient was calculated. The degree of correlation was categorized as high (r(2) > 0.66), moderate (0.66 > or = r(2) > 0.33), or low (r(2) < or = 0.33). The standard error of threshold estimation was calculated. RESULTS: Most locations of the visual field had high and moderate correlations with neighboring points and with distant locations corresponding to the same nerve fiber bundle. Locations of the visual field had low correlations with those of the opposite hemifield, with the exception of locations temporal to the blind spot. The standard error of threshold estimation increased from 0.6 to 0.9 dB with an r(2) reduction of 0.1. CONCLUSION: Locations of the visual field have highest interpoint correlation with neighboring points and with distant points in areas corresponding to the distribution of the retinal nerve fiber layer. The quantification of interpoint correlations may be useful in the design and interpretation of visual field tests in patients with glaucoma.  相似文献   
996.
997.
Summary. Background: Although an important secondary prevention trial reported an impressive protection by a Mediterranean dietary pattern on reinfarction and cardiovascular death, scarce direct epidemiologic evidence is currently available regarding the role of the Mediterranean diet in the aetiology of coronary heart disease. Aims: The aim of the study was to quantify the risk reduction of incident myocardial infarction provided by a Mediterranean dietary pattern. Methods: We included 342 subjects (171 patients who suffered their first acute myocardial infarction and 171 matched controls) in a case-control study. A validated semi-quantitative food frequency questionnaire (136 items) was used. We defined an a priori Mediterranean dietary pattern. We assessed six food items that we considered protective: 1) olive oil, 2) fiber, 3) fruits, 4)vegetables, 5) fish and 6) alcohol. For each of these six dietary factors, we calculated the distribution according to quintiles within the study and assigned each participant a score of 1 to 5 corresponding to the quintile of intake, with 1 representing the lowest and 5 representing the highest quintile. We also estimated the quintiles of two other elements assumed to be associated with a higher risk: 7) meat/meat products and 8) some items with high glycaemic load (white bread, pasta and rice). For these two elements we inversely ranked the score, with 1 representing the highest and 5 representing the lowest quintile. Finally, we summed up the eight quintile values for each participant. A second score (post hoc pattern) was built using only a single cut-off point for these eight elements. The cut-off points for each element in this post hoc pattern were decided according to the dose-response relationships between the consumption of each food item and the risk of myocardial infarction observed in the analyses that used quintiles of each food item. Results: For both patterns, we found that the higher the score, the lower the odds ratio of myocardial infarction. A significant linear trend was apparent after adjustment for the main cardiovascular risk factors. For each additional point in the a priori Mediterranean pattern (observed range: 9–38) the odds ratio (95 % confidence intervals) was 0.92 (0.86–0.98). This estimate was 0.55 (0.42–0.73) when we used the post hoc pattern (range: 0–8). Conclusions: Our data support the hypothesis that a Mediterranean diet (that emphasizes olive oil, fiber, fruits, vegetables, fish and alcohol and reduces meat/meat products) can be an effective measure for reducing the risk of myocardial infarction. However, our results support the exclusion of refined cereals with a high glycaemic load as healthy elements of this pattern. Received: 24 January 2002, Accepted: 13 May 2002  相似文献   
998.
999.
1000.
OBJECTIVES: To evaluate the burden of illness in irritable bowel syndrome (IBS), in terms of resource utilisation (direct and indirect) and health-related quality of life (HR-QOL), in individuals with IBS who meet Rome I and Rome II criteria. METHODS: A cross-sectional study, carried out by personal interview, on a representative sample (n = 2000) of the Spanish population. Individuals with suspected IBS were identified via a screening question and subsequently given an epidemiological questionnaire to complete. The questionnaire collected information on IBS symptoms, resource utilisation, and HR-QOL [Medical Outcomes Study 36-item Short Form (SF-36)]. RESULTS: Sixty-five individuals met Rome II criteria for IBS, while 146 individuals met exclusively Rome I criteria. Of Rome II individuals, 67.7% had consulted some type of healthcare professional in the previous 12 months, compared with only 41.8% of those individuals meeting exclusively Rome I criteria (p vs 17.1%); 'drug consumption' (70.8 vs 45.2%); and 'reduced performance in main activity' (60 vs 27.4%). Compared with the general population, the study sample reported significantly worse HR-QOL scores in four dimensions of the SF-36 ('bodily pain', 'vitality', 'social functioning' and 'role-emotional'. Additionally, individuals meeting Rome II criteria reported worse HR-QOL scores than those individuals meeting exclusively Rome I criteria, especially in the 'bodily pain' and 'general health' dimensions. CONCLUSIONS: The burden of illness in IBS is important and correlated to the diagnostic criteria employed. Individuals who met Rome II criteria reported a higher level of resource utilisation and worse HR-QOL than individuals meeting exclusively Rome I criteria.  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