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   185292篇
  免费   1485篇
  国内免费   24篇
耳鼻咽喉   1237篇
儿科学   6918篇
妇产科学   3275篇
基础医学   18620篇
口腔科学   1746篇
临床医学   13270篇
内科学   32369篇
皮肤病学   818篇
神经病学   17483篇
特种医学   9307篇
外科学   29970篇
综合类   2402篇
一般理论   3篇
预防医学   18917篇
眼科学   2848篇
药学   10085篇
中国医学   654篇
肿瘤学   16879篇
  2021年   153篇
  2020年   100篇
  2019年   145篇
  2018年   22063篇
  2017年   17461篇
  2016年   19649篇
  2015年   1090篇
  2014年   1043篇
  2013年   1112篇
  2012年   7529篇
  2011年   21572篇
  2010年   19131篇
  2009年   11814篇
  2008年   19999篇
  2007年   22208篇
  2006年   1084篇
  2005年   2726篇
  2004年   3875篇
  2003年   4798篇
  2002年   2957篇
  2001年   363篇
  2000年   469篇
  1999年   270篇
  1998年   325篇
  1997年   290篇
  1996年   170篇
  1995年   194篇
  1994年   165篇
  1993年   121篇
  1992年   94篇
  1991年   151篇
  1990年   177篇
  1989年   124篇
  1988年   100篇
  1987年   81篇
  1985年   81篇
  1984年   74篇
  1980年   76篇
  1974年   75篇
  1938年   92篇
  1933年   115篇
  1932年   132篇
  1931年   89篇
  1930年   113篇
  1929年   73篇
  1928年   92篇
  1927年   86篇
  1926年   98篇
  1925年   87篇
  1924年   87篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Background/Aims The aim of this work is to determine the long-term therapeutic benefit(s) of daclizumab induction therapy with triple immunosuppressive protocols including prednisolone, cyclosporine microemulsion (CsA), and mycophenolate mofetil (MMF) in the living related donor kidney transplantation. Methods Twenty-one adult recipients of their first kidney allograft were allocated to receive daclizumab with triple immunosuppressive therapy (steroids, CsA, and MMF). They were compared to 50 recipients of their first grafts who received a maintenance triple immunosuppressive therapy (steroids, CsA, and azathioprine). The patients were followed up for 5 years. Results Daclizumab group significantly experienced a marked reduction of acute rejection (7/21) when compared to the control group (31/50) with subsequent significant reduction of cumulative steroids doses at the end of 5 years. The overall incidence of post-transplant complications was comparable among the two treatment groups. There was no significant difference in patients and graft survival; 5-year patient and graft survival were 95.3%, 85.7% for daclizumab and 96%, 88% for control group, respectively. Conclusions Although prophylactic daclizumab with triple immunosuppressive protocol including MMF have drastically reduced the incidence of acute rejections, the graft and patient survival are unchanged in this long-term follow up.  相似文献   
992.
Mediastinal irradiation has been reported to induce cardiac diseases such as pericardial disease, accelerated arteriosclerosis of the coronary arteries, valvular disease, conduction abnormalities, and calcification of the aorta. We experienced four cases of radiation-induced valvular disease. All patients had histories of radiation therapy and had aortic valve disease. All patients had marked fibrosis of the mediastinum and hypertrophy of pericardium. The aortic valve leaflets were tricuspid and fibrotic with focal dystrophic calcification and markedly thickened. In the pathological findings, certain rheumatic endocarditis changes such as endocardial reduplication and vascularization were not found in all aortic valves. The mechanism of radiation-induced cardiac disease is not clear. However, those changes seem to progress very slowly. Thus, long-term follow-up care is particularly important for patients undergoing radiation therapy. Fortunately, today's irradiation techniques are much less harmful; therefore, radiation-induced cardiac disease will likely become more rare in the future.  相似文献   
993.
Background The aim of the present study was to develop a risk-scoring method for prediction of immediate postoperative outcome after infrainguinal surgical revascularization for critical limb ischemia. Methods The Finnvasc registry included data on 3,925 infrainguinal surgical revascularization procedures. This database was randomly divided into a derivation and a validation data set of similar sizes. Results In the overall series, 30-day postoperative mortality and major amputation rates were 3.1% and 6.3%, respectively. The 30-day postoperative mortality and/or limb-loss rate was 9.2%. Diabetes, coronary artery disease, foot gangrene, and urgent operation were independent predictors of 30-day postoperative mortality and/or major lower-limb amputation. A risk score was developed by assigning 1 point each to the latter risk factors. In the derivation data set, the 30-day postoperative mortality/amputation rates in patients with scores of 0, 1, 2, 3, and 4 were 7.7%, 6.4%, 11.1%, 20.4%, and 27.3%, respectively, (P < 0.0001); mortality rates were 1.3%, 2.3%, 4.1%, 7.7%, and 12.1%, respectively, (P < 0.0001); and major amputation rates were 6.4%, 4.3%, 7.1%, 12.7%, and 18.2%, respectively, (P < 0.0001). In the validation data set, the 30-day postoperative mortality/amputation rates in patients with scores of 0, 1, 2, 3, and 4 were 4.8%, 7.5%, 10.1%, 15.9%, and 22.2%, respectively, (P < 0.0001); mortality rates were 0.7%, 2.3%, 4.2%, 5.5%, and 14.8%, respectively, (P < 0.0001); and major amputation rates were 4.6%, 5.3%, 6.4%, 11.0%, and 14.0%, respectively (P = 0.011). Conclusions This simple risk-scoring method can be useful to stratify the immediate postoperative outcome of patients undergoing infrainguinal surgical revascularization for critical lower-limb ischemia.  相似文献   
994.
There are few reports on urinary tract infections caused by Haemophilus influenzae or Haemophilus parainfluenzae in children. The true incidence is not known, since bacteria of Haemophilus species do not grow in standard urine culture media. With the objective of investigating the occurrence and character of urinary tract infections (UTIs) caused by Haemophilus bacteria in children, we searched the files of our UTI clinic. Over a 24-year period 36 children with Haemophilus spp. bacteriuria were identified out of a total of more than 5,000 UTI episodes. There was a significant gender difference in that Haemophilus influenzae dominated in girls and Haemophilus parainfluenzae in boys. With one exception, all children had important urinary tract abnormalities, such as malformation, gross reflux or bladder dysfunction. Permanent renal damage was seen in 25. We conclude that growth of Haemophilus bacteria in urine is associated with serious urinary tract abnormalities. The inability of bacteria of the Haemophilus species to grow in standard media commonly used for culture of uropathogens suggests that the true frequency of these strains as a cause of urinary tract infections is underestimated.  相似文献   
995.
Background: Abdominal lipectomy is becoming an increasingly common surgical procedure in patients with esthetic deformities resulting from massive weight loss induced by bariatric surgery. Sometimes a midline incisional hernia coexists with the pendulus abdomen. Herein presented is a technique to perform a retromuscular mesh repair of the incisional hernia while sparing the umbilicus. Methods: The abdominal lipectomy with concomitant retro-muscular mesh repair of a midline incisional hernia is done sparing the vascular supply of the umbilicus on one side only. Results: 5 consecutive women with pendulus abdomen resulting from bariatric surgery-induced massive weight loss and concomitant midline incisional hernia underwent abdominal lipectomy and incisional hernia mesh repair. Mean BMI was 28.6 kg/m2 (range 26–35), one patient was a smoker, and another had type 2 diabetes requiring oral hypoglycemic agents. Two patients had had a previous incisional hernia repair with intraperitoneal mesh. One patient had partial necrosis of the umbilicus and another experienced necrosis of only the epidermis that recovered fully. Conclusions: The umbilicus can be safely spared during abdominal lipectomy with concomitant midline incisional hernia mesh repair. Recurrent incisional hernia and common risk factors for wound healing such as diabetes and obesity increase the risk of umbilical necrosis.  相似文献   
996.
997.
A lot of new implant devices for spine surgery are coming onto the market, in which vertebral screws play a fundamental role. The new screws developed for surgery of spine deformities have to be compared to established systems. A biomechanical in vitro study was designed to assess the bone–screw interface fixation strength of seven different screws used for correction of scoliosis in spine surgery. The objectives of the current study were twofold: (1) to evaluate the initial strength at the bone–screw interface of newly developed vertebral screws (Universal Spine System II) compared to established systems (product comparison) and (2) to evaluate the influence of screw design, screw diameter, screw length and bone mineral density on pullout strength. Fifty-six calf vertebral bodies were instrumented with seven different screws (USS II anterior 8.0 mm, USS II posterior 6.2 mm, KASS 6.25 mm, USS II anterior 6.2 mm, USS II posterior 5.2 mm, USS 6.0 mm, USS 5.0 mm). Bone mineral density (BMD) was determined by quantitative computed tomography (QCT). Failure in axial pullout was tested using a displacement-controlled universal test machine. USS II anterior 8.0 mm showed higher pullout strength than all other screws. The difference constituted a tendency (P = 0.108) when compared to USS II posterior 6.2 mm (+19%) and was significant in comparison to the other screws (+30 to +55%, P < 0.002). USS II posterior 6.2 mm showed significantly higher pullout strength than USS 5.0 mm (+30%, P = 0.014). The other screws did not differ significantly in pullout strength. Pullout strength correlated significantly with BMD (P = 0.0015) and vertebral body width/screw length (P < 0.001). The newly developed screws for spine surgery (USS II) show higher pullout strength when compared to established systems. Screw design had no significant influence on pullout force in vertebral body screws, but outer diameter of the screw, screw length and BMD are good predictors of pullout resistance.  相似文献   
998.
Abstract Posttraumatic synostosis of the forearm bones is a rare but serious complication following fixation or even conservative treatment of adult forearm fractures. This is the second report in the English literature of such a complication at the pin-track site following external fixation of proximal forearm fractures. A 36-year-old male patient sustained an open fracture of his proximal right forearm after a road traffic accident. It was managed by external fixation of the ulna and plate fixation of the radius. At follow-up, a type 3 radio-ulnar synostosis at the pin-track site became evident, which was treated after 20 months with surgical resection of the bony bridge to regain the rotatory motion of his forearm. An erratum to this article is available at .  相似文献   
999.
Background Many studies have shown that angiogenesis plays an important role in the process of cancer development and progression. Vascular endothelial growth factor (VEGF) has a potent angiogenic activity, and cyclooxygenase-2 (COX-2) supports angiogenesis by regulated production of angiogenic factors, including VEGF. The purpose of this study was to examine the expression of VEGF in combination with COX-2 and CD34, their correlation with various clinicopathological factors, and their prognostic significance in human gastric carcinoma. Methods Specimens from 169 patients with different grade and stage gastric carcinoma were investigated by immunohistochemistry for COX-2 and VEGF expression. Tumor microvessel density was assessed with CD34 immunostaining. Correlations between the expression of VEGF, COX-2, CD34, and various clinicopathological factors were studied. The effect of these proteins on patient survival was determined. Results COX-2 and VEGF were positively expressed in 36.7% and 50.3% of the patients, respectively. Positive correlation was found between VEGF and COX-2 and between VEGF and CD34. VEGF expression was correlated with depth of invasion; metastatic lymph nodes; lymphatic and venous invasion; and tumor, node, metastasis system stage. Patients with positive staining for VEGF showed far lower disease-free (64.9% vs. 81.3%) and overall (58.3% vs. 76.9%) survival rates than VEGF-negative patients. In multivariate analysis, only tumor location, depth of invasion, and lymph node metastasis were shown to be independent prognostic factors. Conclusions VEGF expression correlates with angiogenesis and tumor progression and is a valuable prognostic factor in patients with gastric carcinoma.  相似文献   
1000.
Background Breast carcinoma is the most frequently diagnosed malignancy in women of the North America. The combination of breast-conservation surgery and radiotherapy has become a standard of treatment for most breast cancers. It is critical to obtain clear margins to minimize local recurrence. The literature suggests that intraoperative touch preparation cytology (IOTPC) can be useful in evaluation of margins. Invasive lobular carcinoma (ILC) accounts for 10% to 15% of all breast cancers. Obtaining clear margins in ILC can be more challenging. Literature shows the positive margin rate for ILC to be as high as 60%. This report describes our experience with IOTPC for margin assessment in ILC by a single surgeon at Beth Israel Medical Center. The purpose of this study is to determine whether IOTPC is reliable for ILC. Methods A prospective review of 73 patients who underwent breast-conservation surgery with the use of IOTPC for margin assessment at Beth Israel Medical Center was performed. Pathology revealed ILC in 12 of these patients (16.4%), who are the subjects of this study. The lumpectomy specimens were oriented by the surgeon intraoperatively and were submitted fresh to pathology for cytologic assessment. IOTPC consisted of touching the corresponding margin onto the glass slide. The principle of this technique is that if cancer cells are present, they will stick to the slide, whereas fat cells will not. Six slides were prepared for each lumpectomy specimen. Air-dried samples were stained immediately by the Diff-Quik method and examined under the microscope by a cytopathologist. Results Twelve patients with ILC underwent breast-conservation surgery with IOTPC for assessment of 72 margins. Ten patients had lobular carcinoma only, and the remaining two patients had a combination of lobular and ductal carcinoma. There was a correlation between IOTPC and final pathology in 60 of 72 margins, which accounted for 83.3% of the cases. IOTPC for assessment of margins in patients undergoing breast-conservation surgery for ILC has a sensitivity of 8.3%, specificity of 98.3%, positive predictive value of 50%, and negative predictive value of 84.3%. Conclusions On the basis of our experience, IOTPC is of limited value for intraoperative assessment of margins for ILC. Poster presentation at the Sixth Annual Meeting of the American Society of Breast Surgeons, March 16–20, 2005, Los Angeles, California.  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