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   9565篇
  免费   626篇
  国内免费   34篇
耳鼻咽喉   131篇
儿科学   315篇
妇产科学   325篇
基础医学   1352篇
口腔科学   483篇
临床医学   1090篇
内科学   1815篇
皮肤病学   164篇
神经病学   791篇
特种医学   200篇
外科学   805篇
综合类   66篇
一般理论   3篇
预防医学   1274篇
眼科学   100篇
药学   674篇
中国医学   32篇
肿瘤学   605篇
  2024年   15篇
  2023年   101篇
  2022年   176篇
  2021年   265篇
  2020年   251篇
  2019年   282篇
  2018年   351篇
  2017年   279篇
  2016年   254篇
  2015年   330篇
  2014年   369篇
  2013年   520篇
  2012年   800篇
  2011年   820篇
  2010年   432篇
  2009年   391篇
  2008年   671篇
  2007年   645篇
  2006年   569篇
  2005年   551篇
  2004年   502篇
  2003年   456篇
  2002年   409篇
  2001年   57篇
  2000年   39篇
  1999年   56篇
  1998年   63篇
  1997年   58篇
  1996年   37篇
  1995年   50篇
  1994年   46篇
  1993年   45篇
  1992年   22篇
  1991年   30篇
  1990年   21篇
  1989年   12篇
  1988年   18篇
  1987年   15篇
  1986年   18篇
  1985年   26篇
  1984年   19篇
  1983年   18篇
  1982年   9篇
  1981年   11篇
  1980年   14篇
  1979年   13篇
  1978年   12篇
  1975年   6篇
  1974年   9篇
  1971年   7篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
The aims of this study were to analyse the effect of different body positions on pelvic floor muscle (PFM) assessment using digital muscle testing, manometry and transabdominal ultrasound. In addition, subject acceptance of each testing position was recorded. Subjects were 20 women's health physiotherapists. The testing protocol included the best of three maximum voluntary contractions tested in each of four positions (crook lying, supine, sitting and standing). Significant differences in muscle strength and subject acceptance between positions were found with each tool, most often between lying and upright positions. Digital muscle testing and vaginal squeeze-pressure scores were highest in the lying position, and vaginal resting pressure and transabdominal ultrasound scores were highest in the standing position. Subjects preferred the lying positions for internal examinations. The clinical significance of these differences and the reasons for these variations require further investigation.  相似文献   
102.
A FRAX model for Canada was constructed for prediction of osteoporotic and hip fracture risk using national hip fracture data with and without the use of femoral neck bone mineral density (BMD). Performance of this system was assessed independently in a large clinical cohort of 36,730 women and 2873 men from the Manitoba Bone Density Program database that tracks all clinical dual‐energy X‐ray absorptiometry (DXA) test results for the Province of Manitoba, Canada. Linkage with other provincial health databases allowed for the direct comparison of fracture risk estimates from the Canadian FRAX model with observed fracture rates to 10 years (549 individuals with incident hip fractures and 2543 with incident osteoporotic fractures). The 10‐year Kaplan‐Meier estimate for hip fractures in women was 2.7% [95% confidence interval (CI) 2.1–3.4%] with a predicted value of 2.8% for FRAX with BMD, and in men the observed risk was 3.5% (95% CI 0.8–6.2%) with predicted value of 2.9%. The 10‐year estimate of osteoporotic fracture risk for all women was 12.0% (95% CI 10.8–13.4%) with a predicted value of 11.1% for FRAX with BMD, and in men, the observed risk was 10.7% (95% CI 6.6–14.9%) with a predicted value of 8.4%. Discrepancies were observed within some subgroups but generally were small. Fracture discrimination based on receiver operating characteristic curve analysis was comparable with published meta‐analyses with area under the curve for osteoporotic fracture prediction of 0.694 (95% CI 0.684–0.705) for FRAX with BMD and for hip fractures 0.830 (95% CI 0.815–0.846), both of which were better than FRAX without BMD or BMD alone. Individual risk factors considered by FRAX made significant independent contributions to fracture prediction in one or more of the models. In conclusion, a Canadian FRAX tool calibrated on national hip fracture data generates fracture risk predictions that generally are consistent with observed fracture rates across a wide range of risk categories. © 2010 American Society for Bone and Mineral Research.  相似文献   
103.
Chronic tubulo-interstitial disease, an important cause of end-stage renal disease, often results from the combined effects of a disturbed urinary outflow tract and urinary tract infection. Acute unilateral ureteral obstruction in rats rapidly induces foci of medullary necrosis, confined to the region of the papilla and fornices. This injury may provide a nidus for bacterial invasion and may invoke reactive and regenerative changes, ultimately leading to chronic pyelonephritis and tubulo-interstitial nephropathy. To explore this possibility, adult rats underwent renal morphological evaluation 2–7 days following transient 24-h unilateral ureteral obstruction. In some experiments the bladder was inoculated with bacteria (108–109 cfu/ml Escherichia coli in 0.5 ml) after release of ureteral obstruction, with subsequent cultures obtained from the pelvis of both kidneys and from the urinary bladder. Morphologic evaluation of perfusion-fixed kidneys, 2–7 days after the release of 24-h ureteral obstruction disclosed papillary necrosis, urothelial proliferation, marked inner-stripe interstitial expansion, and fibrosis and proximal tubular (S3) dilatation. The lateral (perihilar region) was predominantly affected, with lesions spreading from the fornices. There was some progression of interstitial fibrosis during the postobstructive time course or following more prolonged ureteral obstruction. By contrast, infection hardly contributed to the tubulointerstitial changes. In rats subjected to infection, cultures were positive in all 15 postobstructive kidneys, as opposed to five contralateral kidneys (P < 0.0001). Viable counts from the postobstructive kidney were also higher than those from the contralateral side (79,000 ± 12,000 vs 2900 ± 1600 cfu/ml, mean ± SEM, P < 0.0001), and were comparable to those obtained from the bladder (77,000 ± 13,000 cfu/ml). We conclude that transient ureteral obstruction predisposes to ascending pyelonephritis and to tubulointerstitial disease. This vulnerability may relate to altered urodynamics and medullary tissue destruction. Received: 28 December 1999 / Accepted: 28 September 2000  相似文献   
104.
Few cases of successful portal vein arterialization in orthotopic and auxiliary liver transplantation have been reported. AIM: To evaluate the effect of portal vein arterialization on hepatic hemodynamics and long-term clinical outcome in three patients undergoing liver transplantation. METHODS: Two patients with extensive splanchnic venous thrombosis received an orthotopic liver transplant and one with fulminant hepatic failure received an auxiliary heterotopic graft. Portal vein arterialization was performed in all cases. RESULTS: One patient died 4 months after transplant and two are still alive. Auxiliary liver graft was removed 3 months post-transplant when complete native liver regeneration was achieved. Immediate post-transplant liver function was excellent in all cases. Only one patient developed encephalopathy and variceal bleeding owing to prehepatic portal hypertension secondary to arterioportal fistula 14 months after transplant. He was successfully treated by embolization of the hepatic artery. Hepatic hemodynamic measurements demonstrated a normal pressure gradient between wedged and free hepatic venous pressures in all cases. Liver biopsy showed acceptable graft architecture in two cases and microsteatosis in one. CONCLUSIONS: Liver transplantation with portal vein arterialization is an acceptable salvage alternative when insufficient portal venous flow to the graft is present. The double arterial supply does not imply changes in hepatic hemodynamics, at least in the early months post-transplant.  相似文献   
105.
106.
Background: Bariatric surgery is expanding to meet the global epidemic of morbid obesity, because this surgery is successful in achieving sustained weight loss. After having recently established a rat model of gastric banding, our aim now was to investigate the relative fat mass content and the feeding patterns of gastric banded rats. Methods: Two groups of Wistar rats, submitted either to gastric banding or to sham surgery, were followed-up for 26 days regarding weight, daily food intake and feeding patterns both under resting conditions and when refed after fasting. Weight of the epididymal fat pad was used as a measure to evaluate changes in white adipose tissue in the rats. Results: 10 days after surgery and thereafter, rats submitted to gastric banding showed the same daily food intake that was observed in sham-operated rats. Nevertheless, gastric banded rats kept lower body weights and were leaner than controls. These differences were associated with distinctive feeding patterns, both under resting conditions and when refed after fasting, suggesting that gastric banded rats present a significant increase in feeding frequency when compared with controls. Conclusion: This data is the first experimental evidence that an increase in feeding frequency is associated with weight loss after gastric banding, even if there is no decrease in total energy intake. Thus, medical advice on the advantages of fractionating daily caloric intake into multiple meals is further supported by the herein new information obtained in an animal model of gastric banding.  相似文献   
107.
BACKGROUND: Hypercholesterolemia after organ transplantation is common. Previously, we observed higher serum total cholesterol (TC) concentrations in our pediatric kidney than liver or heart transplant recipients. To find an explanation to the observed difference, our kidney recipients' cholesterol synthesis and absorption efficiency was compared to those of liver and heart recipients. METHODS: Serum noncholesterol sterol ratios (10 x mmol to the mol of TC, surrogate estimates of hepatic cholesterol synthesis and intestinal absorption) were studied in 50 pediatric kidney, 25 liver and 12 heart transplant recipients without diabetes or cholestasis, and in 29 controls. RESULTS: The kidney recipients had lower Delta-cholesterol (P=0.031), similar lathosterol and higher desmosterol ratios (markers of cholesterol synthesis) (P=0.020), and similar campesterol and sitosterol ratios (markers of cholesterol absorption) when compared to the controls. The liver recipients had lower campesterol ratios than the kidney recipients and controls (P=0.002). Glomerular filtration rates were not associated with the ratios of noncholesterol sterols. Multivariate analysis showed markers of cholesterol synthesis to be lower and absorption to be higher in the kidney than the liver or the heart transplant recipients. Weight-adjusted dosages of immunosuppressive agents were associated with some ratios of noncholesterol sterols and cholestanol though these varied between the transplant recipient groups. CONCLUSIONS: Serum TC concentration in kidney recipients was not significantly associated with absorption efficiency or synthesis of cholesterol, though kidney transplantation was associated with low synthesis and high absorption efficiency of cholesterol. Immunosuppressive therapy with cyclosporine and methylprednisolone may modulate absorption efficiency and synthesis of cholesterol.  相似文献   
108.
Purpose:This study assessed the regeneration potential of mesenchymal stem cells (MSC) from adipose tissue associated with platelet-rich plasma (PRP) in bone regeneration.Methods:Thirty Wistar rats (Rattus norvegicus albinos) were divided into five groups (according to the grafting material and time to euthanasia): (1) autograft - 14 days (control), (2) autograft - 28 days (control), (3) MSC + PRP - 14 days, (4) MSC + PRP + papaverine - 14 days and (5) MSC + PRP + papaverine - 28 days. After euthanasia, the graft was removed and histological slides were prepared. They were assessed by a blinded pathologist using a previously published histological scale as parameter.Results:There was some degree of neoformed bone trabeculae (NBT) in 93.3% of the samples, as well as osteoblastic activity (OA). The autograft groups (14 and 28 days) had higher levels in the formation of bone trabeculae. Nonparametric data were analyzed using the Wilcoxon-Mann-Whitney test and proved not to be statistically significant at p < 0.05.Conclusions:Experimental parietal bone reconstruction, combining MSC, PRP and papaverine presented regeneration in all groups with no significant difference among them.Key words: Bone Regeneration, Platelet-Rich Plasma, Tissue Engineering, Rats  相似文献   
109.
Occupational diseases of dentists and dental nurses were compiled from the Finnish Register of Occupational Diseases. The cases were recorded during 3 3-year observation periods, namely 1982-1984, 1986-1988, and 1992-1994 (i.e., 9 observation years). The relative risk of developing occupational allergic contact dermatitis in different occupations was calculated from the statistics of the years 1986-1991, and was expressed as the age-standardized rate ratio (SRR). During the 9 observation years, the majority of registered occupational diseases of dentists and dental nurses were skin diseases (221/312; 70.8%), followed by occupational repetitive strain injuries (61/312; 19.6%) and occupational respiratory diseases (20/312; 6.4%). The incidence rate (IR) for allergic contact dermatoses/10,000 workers (contact urticaria included) increased from 26 (95% confidence interval (CI) 16-40) in 1982-1984 to 79 (95%, CI 64-97) in 1992-1994. The IR/10,000 of allergic contact dermatoses increased especially for dentists, from 5.4 (95% CI 0.7-19) in 1982 to 67 (95% CI 45-95) in 1992-1994. The increase of the IR/10,000 dental nurses was smaller: from 43 (95%, CI 26-66) in 1982-1984 to 87 (95% CI 67-111) in 1992-1994. There was no increase in the IR/10,000 cases of irritant dermatoses. The most common causes of allergic contact dermatitis were plastics, disinfectants and antimicrobials, rubber chemicals, and mercury/mercury salts. The most common causes of irritant contact dermatitis were detergents, wet and dirty work, plastic chemicals and antimicrobials. Currently, Finnish dentists have the highest risk and dental nurses have the 4th highest risk of any occupation for developing occupational allergic contact dermatitis: the risk was 6.4-fold (SRR 6.4) in dentists and 6.1-fold in dental nurses, as compared to the general working population. It is evident that safer acrylics and protective gloves, better product declarations and material safety data sheets, as well as more information about protective measures, including non-touch working techniques, are needed.  相似文献   
110.
PURPOSE: Schnyder crystalline corneal dystrophy (SCCD; MIM 121800) is a rare autosomal dominant disease characterized by an abnormal increase in cholesterol and phospholipid deposition in the cornea, leading to progressive corneal opacification. Although SCCD has been mapped to a genetic interval between markers D1S1160 and D1S1635, reclassification of a previously unaffected individual expanded the interval to D1S2667 and included nine additional genes. Three candidate genes that may be involved in lipid metabolism and/or are expressed in the cornea were analyzed. METHODS: DNA samples were obtained from six families with clinically confirmed SCCD. Analysis of FRAP1, ANGPTL7, and UBIAD1 was performed by PCR-based DNA sequencing, to examine protein-coding regions, RNA splice junctions, and 5' untranslated region (UTR) exons. RESULTS: No disease-causing mutations were found in the FRAP1 or ANGPTL7 gene. A mutation in UBIAD1 was identified in all six families: Five families had the same N102S mutation, and one family had a G177R mutation. Predictions of the protein structure indicated that a prenyl-transferase domain and several transmembrane helices are affected by these mutations. Each mutation cosegregated with the disease in four families with DNA samples from both affected and unaffected individuals. Mutations were not observed in 100 control DNA samples (200 chromosomes). CONCLUSIONS: Nonsynonymous mutations in the UBIAD1 gene were detected in six SCCD families, and a potential mutation hot spot was observed at amino acid N102. The mutations are expected to interfere with the function of the UBIAD1 protein, since they are located in highly conserved and structurally important domains.  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