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   5546篇
  免费   331篇
  国内免费   15篇
耳鼻咽喉   41篇
儿科学   131篇
妇产科学   104篇
基础医学   705篇
口腔科学   391篇
临床医学   479篇
内科学   1165篇
皮肤病学   92篇
神经病学   438篇
特种医学   195篇
外科学   865篇
综合类   24篇
一般理论   2篇
预防医学   367篇
眼科学   83篇
药学   429篇
中国医学   16篇
肿瘤学   365篇
  2023年   28篇
  2022年   35篇
  2021年   83篇
  2020年   61篇
  2019年   73篇
  2018年   126篇
  2017年   100篇
  2016年   120篇
  2015年   137篇
  2014年   144篇
  2013年   265篇
  2012年   378篇
  2011年   370篇
  2010年   246篇
  2009年   238篇
  2008年   332篇
  2007年   334篇
  2006年   347篇
  2005年   372篇
  2004年   361篇
  2003年   347篇
  2002年   317篇
  2001年   46篇
  2000年   35篇
  1999年   63篇
  1998年   76篇
  1997年   52篇
  1996年   43篇
  1995年   51篇
  1994年   39篇
  1993年   29篇
  1992年   38篇
  1991年   42篇
  1990年   29篇
  1989年   32篇
  1988年   33篇
  1987年   37篇
  1986年   29篇
  1985年   38篇
  1984年   34篇
  1983年   27篇
  1982年   33篇
  1981年   31篇
  1980年   19篇
  1979年   19篇
  1978年   21篇
  1977年   22篇
  1976年   17篇
  1975年   18篇
  1974年   22篇
排序方式: 共有5892条查询结果,搜索用时 250 毫秒
101.

Background  

Rotational thromboelastography (ROTEG) has been proposed as a monitoring tool that can be used to monitor treatment of hemophilia with recombinant factor VIIa (rFVIIa). In these studies special non-standard reagents were used as activators of the coagulation. The aim of this study was to evaluate if standard ROTEG analysis could be used for monitoring of effects of recombinant factor VIIa (rFVIIa) on Hydroxy Ethyl Starch-induced dilutional coagulopathy.  相似文献   
102.
Amyloid diseases encompass >20 medical disorders that include amyloid protein A (AA) amyloidosis, Alzheimer's disease, and type 2 diabetes. A common feature of these conditions is the selective organ deposition of disease-specific fibrillar proteins, along with the sulfated glycosaminoglycan, heparan sulfate. We have generated transgenic mice that overexpress human heparanase and have tested their susceptibility to amyloid induction. Drastic shortening of heparan sulfate chains was observed in heparanase-overproducing organs, such as liver and kidney. These sites selectively escaped amyloid deposition on experimental induction of inflammation-associated AA amyloidosis, as verified by lack of material staining with Congo Red, as well as lack of associated polysaccharide, whereas the same tissues from control animals were heavily infiltrated with amyloid. By contrast, the spleens of transgenic mice that failed to significantly overexpress heparanase contained heparan sulfate chains similar in size to those of control spleen and remained susceptible to amyloid deposition. Our findings provide direct in vivo evidence that heparan sulfate is essential for the development of amyloid disease.  相似文献   
103.
Recent studies on the immunoglobulin variable heavy chain (IgV(H)) genes have revealed that B-cell chronic lymphocytic leukemia (B-CLL) consists of at least 2 clinical entities with either somatically mutated or unmutated V(H) genes. We have analyzed the V(H) gene mutation status and V(H) gene usage in 119 B-CLL cases and correlated them to overall survival. A novel finding was the preferential use of the V(H)3-21 gene in mutated cases, whereas biased V(H)1-69 gene usage was found in unmutated cases as previously reported. Interestingly, the subset of mutated cases using the V(H)3-21 gene displayed distinctive genotypic/phenotypic characteristics with shorter average length of the complementarity determining region 3 and clonal expression of lambda light chains. In addition, this mutated subset showed significantly shorter survival than other mutated cases and a similar clinical course to unmutated cases. We therefore suggest that B-CLL cases with mutated V(H)3-21 genes may constitute an additional entity of B-CLL.  相似文献   
104.
PURPOSE: Pouchitis represents a serious threat to patients with ulcerative colitis after restorative proctocolectomy with ileal pouch-anal anastomosis. The frequency of pouchitis is high, and it implies the risk of pouch failure and the risk of malignant mucosal transformation in the pouch. Early detection and precise classification of the inflammatory process are required for adequate therapy, which might be facilitated using a scoring system. The aim of the present study was to validate two existing scoring systems in routine outpatient practice. METHOD: The Heidelberg Pouchitis Activity Score and the Pouchitis Disease Activity Index developed at the Mayo Clinic were simultaneously prospectively applied in a consecutive series of 103 outpatient consultations of 41 patients at our hospital and comparatively validated against the diagnosis of pouchitis or no pouchitis concurrently made by a physician and a surgeon. RESULTS: The median score of examinations in which the clinicians diagnosis was consistent with pouchitis were significantly higher than those of examinations inconsistent with pouchitis in both scoring systems (Heidelberg Pouchitis Activity Score, 17 (interquartile range, 14–21) and 8 (interquartile range, 5–10), respectively, P < 0.001; Pouchitis Disease Activity Index, 7 (interquartile range, 5–8) and 2.5 (interquartile range, 1–4), respectively, P < 0.001). The sensitivity and specificity in the two total scores were 84 and 79.5 percent, respectively (Heidelberg Pouchitis Activity Score), and 60 and 96.2 percent, respectively (Pouchitis Disease Activity Index); in the field clinical manifestations 44 and 73.1 percent, respectively (Heidelberg Pouchitis Activity Score), and 20 and 87.2 percent, respectively (Pouchitis Disease Activity Index); in the field endoscopic manifestations 88 and 83.3 percent, respectively (Heidelberg Pouchitis Activity Score), and 60 and 89.7 percent, respectively (Pouchitis Disease Activity Index); and in the field histologic manifestations 72 and 76.9 percent, respectively (Heidelberg Pouchitis Activity Score), and 44 and 96.2 percent, respectively (Pouchitis Disease Activity Index). Lowering the cutoff point for diagnosis of pouchitis in the Pouchitis Disease Activity Index by 2 points (pouchitis: score 5) would result in an 88 percent sensitivity and a 67 percent specificity. CONCLUSIONS: Specificity and sensitivity of the Heidelberg Pouchitis Activity Score were satisfactory. The cutoff point for diagnosing pouchitis in the Pouchitis Disease Activity Index would have to be lowered to reach an acceptable sensitivity and specificity. The very poor validity of the field clinical manifestations in diagnosing pouchitis emphasizes the need for endoscopic and histologic examination for detection of pouchitis. The issue of whether the diagnosis of pouchitis should be based on endoscopic and histologic features alone, instead of additionally taking clinical features into account, should be addressed in future studies.  相似文献   
105.

Background/Purpose

Carcinoma of the distal bile duct is associated with poor prognosis. Surgical resection remains the only potentially curative treatment. We conducted a retrospective study to identify prognostic factors determining longterm survival.

Methods

From 1990 to 2006, 95 patients with distal and/or middle bile duct carcinoma had resections. Fifty-four patients underwent pylorus-preserving pancreaticoduodenectomy (57%) and 41 patients underwent standard Kausch-Whipple pancreaticoduodenectomy (43%). Nine patients underwent pancreaticoduodenectomy including portal vein resection (9%).

Results

Overall 1-, 3-, and 5-year survival rates were 60%, 36%, and 29%, respectively. Five-year survival after R0 resection was 34%, and after R1 resection it was 0%. Four patients died during their hospital stay (4%). Multivariate analysis showed negative resection margins (P = 0.040), lymphatic vessel invasion (P = 0.036), and portal vein infiltration (P = 0.027) as strong predictors for survival, whereas the location of the tumor (distal bile duct vs middle bile duct) and lymph node status were not identified as independent prognostic factors.

Conclusions

Five-year survival depends strongly on negative resection margins, independent of nodal status. Portal vein resections in patients with portal vein involvement fail to ameliorate long-term survival. Primary tumor site — middle bile duct or distal bile duct — did not determine prognosis.
  相似文献   
106.

Purpose

Interleukin-6 (IL-6) production and signalling are increased in the inflamed mucosa in inflammatory bowel diseases (IBD). As published serum levels of IL-6 and its soluble receptors sIL-6R and sgp130 in IBD are from small cohorts and partly contradictory, we systematically evaluated IL-6, sIL-6R and sgp130 levels as markers of disease activity in Crohn’s disease (CD) and ulcerative colitis (UC).

Methods

Consecutive adult outpatients with confirmed CD or UC were included, and their disease activity and medication were monitored. Serum from 212 CD patients (815 measurements) and 166 UC patients (514 measurements) was analysed, and 100 age-matched healthy blood donors were used as controls.

Results

IL-6 serum levels were significantly elevated in active versus inactive CD and UC, also compared with healthy controls. However, only a fraction of IBD patients showed increased serum IL-6. IL-6 levels ranged up to 32.7 ng/mL in active CD (>?5000-fold higher than in controls), but also up to 6.9 ng/mL in inactive CD. Increases in active UC (up to 195 pg/mL) and inactive UC (up to 27 pg/mL) were less pronounced. Associations between IL-6 serum levels and C-reactive protein concentrations as well as leukocyte and thrombocyte counts were observed. Median sIL-6R and sgp130 levels were only increased by up to 15%, which was considered of no diagnostic significance.

Conclusions

Only a minority of IBD patients shows elevated IL-6 serum levels. However, in these patients, IL-6 is strongly associated with disease activity. Its soluble receptors sIL-6R and sgp130 do not appear useful as biomarkers in IBD.
  相似文献   
107.

Background

A meta-analysis of randomized trials has shown a significant reduction of mortality rate in patients receiving aspirin for secondary prevention after acute myocardial infarction (AMI). However, a significant number of patients do not receive aspirin after AMI. Little is known about why aspirin is withheld or the long-term outcome of these patients today.

Methods

The Maximal Individual Therapy in Acute Myocardial Infarction (MITRA) registry is a multicenter registry of patients with AMI in Germany.

Results

Of 4902 patients, 509 (10%) did not receive aspirin at the time of discharge from the hospital. The mean follow-up period for these patients was 17 months. Relative contraindications to aspirin were significantly associated with the withholding of aspirin (in-hospital bleeding: odds ratio [OR], 3.56; 95% CI, 1.86-6.80; history of peptic ulcer: OR, 2.49; 95% CI, 1.62-3.83). Absolute contraindications to aspirin were rare (2.2%). Other medications of proven benefit were also given less often in these patients (β-blockers: 49.0% vs 61.9%, P <.001; angiotensin-converting enzyme inhibitors: 65.6% vs 70.2%, P = .06; statins: 12.2% vs 15.1%, P = .10). Patients who were not given aspirin were at high risk for vascular events. They were more likely to have a history of prior AMI (OR, 1.34; 95% CI, 1.02-1.79), were in critical clinical condition at admission more often (cardiogenic shock: OR, 1.98; 95% CI, 1.09-3.56; overt heart failure: OR, 1.6; 95% CI, 1.05-2.3), and received acute revascularization less often (OR, 1.32; 95% CI, 1.05-1.67). The 1-year mortality was 2-times higher in patients who did not receive aspirin than in patients who did receive aspirin (16.5% vs 8.3%, P <.001). A significant association of withheld aspirin at discharge with a higher long-term mortality rate was confirmed with multivariate analysis (OR, 1.62; 95% CI, 1.15-2.29).

Conclusions

Ten percent of patients who sustained an AMI did not receive aspirin at the time of hospital discharge. Most of these patients were at high risk for cardiovascular events. Withheld aspirin was significantly associated with higher mortality rate during follow up.  相似文献   
108.

Background

Our knowledge on the incidence of incisional hernia and risk factors for developing incisional hernia following surgery for colorectal cancer is far from complete.

Methods

All procedures registered in the Swedish Colorectal Cancer Register (SCRCR) 2007–2013 were identified. Patients with comorbid disease diagnoses, registered at admissions and visits prior to the procedure and relevant to this study, were obtained from the National Patient Register (NPR). These diagnoses included cardiovascular disease, connective tissue disorders, liver cirrhosis, renal failure, diabetes, chronic obstructive lung disease and chronic inflammatory conditions. Data on occurrence of incisional hernias were obtained by combining data from the SCRCR and the NPR (International Classification of Diseases code).

Results

During 2007–2013, 39,984 procedures were registered in the SCRCR. After excluding laparoscopic procedures, procedures repeated on the same patient, procedures with concomitant liver resection and procedures without laparotomy, 28,913 cases remained for analysis. Five years after surgery, the cumulative incidence of incisional hernia was 5.3%. In multivariate proportional hazard analysis, significantly increased risk for incisional hernia was found for the male gender (hazard ratio [HR] 1.40, 95% confidence interval [CI] 1.21–1.62), operation time exceeding 180 min (HR 1.25, CI 1.08–1.45), body mass index (BMI) >?30 (HR 1.78, CI 1.51–2.09), age <?70 years (HR 1.34, CI 1.16–1.56) and postoperative wound complication (HR 2.09, CI 1.70–2.58).

Discussion

Men, patients younger than 70 years and patients with BMI?>?30 face a higher risk for incisional hernia. The risk is also increased in cases where the procedure takes longer than 3 h or where postoperative wound complications occur. These patients will benefit from measures aimed at preventing the development of incisional hernia.
  相似文献   
109.
110.
Over the last decade there have been increasing efforts to develop three‐dimensional (3D) scaffolds for bone tissue engineering from bioactive ceramics with 3D printing emerging as a promising technology. The overall objective of the present study was to generate a tissue engineered synthetic bone graft with homogenously distributed osteoblasts and mineralizing bone matrix in vitro, thereby mimicking the advantageous properties of autogenous bone grafts and facilitating usage for reconstructing segmental discontinuity defects in vivo. To this end, 3D scaffolds were developed from a silica‐containing calcium alkali orthophosphate, using, first, a replica technique – the Schwartzwalder–Somers method – and, second, 3D printing, (i.e. rapid prototyping). The mechanical and physical scaffold properties and their potential to facilitate homogenous colonization by osteogenic cells and extracellular bone matrix formation throughout the porous scaffold architecture were examined. Osteoblastic cells were dynamically cultured for 7 days on both scaffold types with two different concentrations of 1.5 and 3 × 109 cells/l. The amount of cells and bone matrix formed and osteogenic marker expression were evaluated using hard tissue histology, immunohistochemical and histomorphometric analysis. 3D‐printed scaffolds (RPS) exhibited more micropores, greater compressive strength and silica release. RPS seeded with 3 × 109 cells/l displayed greatest cell and extracellular matrix formation, mineralization and osteocalcin expression. In conclusion, RPS displayed superior mechanical and biological properties and facilitated generating a tissue engineered synthetic bone graft in vitro, which mimics the advantageous properties of autogenous bone grafts, by containing homogenously distributed terminally differentiated osteoblasts and mineralizing bone matrix and therefore is suitable for subsequent in vivo implantation for regenerating segmental discontinuity bone defects. Copyright © 2016 John Wiley & Sons, Ltd.  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