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   8107篇
  免费   841篇
  国内免费   174篇
耳鼻咽喉   92篇
儿科学   305篇
妇产科学   187篇
基础医学   469篇
口腔科学   116篇
临床医学   1636篇
内科学   1709篇
皮肤病学   140篇
神经病学   478篇
特种医学   342篇
外科学   1894篇
综合类   92篇
一般理论   1篇
预防医学   667篇
眼科学   357篇
药学   273篇
中国医学   1篇
肿瘤学   363篇
  2023年   118篇
  2021年   89篇
  2020年   124篇
  2019年   80篇
  2018年   186篇
  2017年   203篇
  2016年   224篇
  2015年   174篇
  2014年   273篇
  2013年   393篇
  2012年   215篇
  2011年   267篇
  2010年   299篇
  2009年   402篇
  2008年   226篇
  2007年   213篇
  2006年   234篇
  2005年   211篇
  2004年   144篇
  2003年   157篇
  2002年   130篇
  2001年   211篇
  2000年   213篇
  1999年   235篇
  1998年   219篇
  1997年   238篇
  1996年   339篇
  1995年   292篇
  1994年   228篇
  1993年   141篇
  1992年   185篇
  1991年   203篇
  1990年   116篇
  1989年   177篇
  1988年   147篇
  1987年   115篇
  1986年   137篇
  1985年   117篇
  1984年   105篇
  1983年   100篇
  1982年   79篇
  1981年   71篇
  1980年   86篇
  1979年   60篇
  1978年   75篇
  1977年   57篇
  1976年   51篇
  1975年   57篇
  1974年   53篇
  1964年   54篇
排序方式: 共有9122条查询结果,搜索用时 15 毫秒
91.
Donnelly LF  Helms CA  Bisset GS 《Radiology》1999,211(1):233-236
The clinical and imaging (magnetic resonance [MR] imaging, radiography, and bone scintigraphy) findings in three adolescent boys with chronic avulsive injury at the deltoid insertion are presented. MR imaging enabled the exclusion of findings suggestive of malignancy and the localization of abnormalities to the deltoid insertion site. Findings included cortical thickening and irregularity of the deltoid tubercle, with or without adjacent soft-tissue edema.  相似文献   
92.
Donnelly LF  Foss JN  Frush DP  Bisset GS 《Radiology》1999,210(2):493-497
PURPOSE: To (a) determine the appearances and timing of heterogeneous splenic enhancement at spiral computed tomography (CT) and (b) identify variables influencing heterogeneous splenic enhancement. MATERIALS AND METHODS: Sequential isolevel (24-mAs) CT images of the spleen obtained at 6-second intervals after initiation of contrast material injection in 112 children (mean age, 4.5 years) were reviewed. Heterogeneity characteristics assessed included type, onset, maximum, and resolution. Relationship to variables (injection rate, age, splenomegaly) was assessed with the Fisher exact test. RESULTS: Eighty-one of the 112 patients (72%) had transient heterogeneity: archiform (45 patients), diffuse (25 patients), and focal (11 patients). Mean times were as follows: initial visualization after onset of contrast material injection, 19.2 seconds; maximum heterogeneity, 27.3 seconds; and resolution, 47.4 seconds. Statistically significant relationships were seen between frequency of heterogeneity and injection rate (> or = 1 mL/sec, 82%; < 1 mL/sec, 50% [P = .001]), age (> 1 year, 76%; < or = 1 year, 46% [P = .04]), and splenomegaly (present, 20%; absent, 77% [P = .048]). CONCLUSION: Heterogeneous splenic contrast enhancement is common, has several patterns of appearance, and is predictably encountered during the 70 seconds after the initiation of contrast material injection. Injection rate, age, and presence of splenic disease influence the frequency with which these artifacts are encountered.  相似文献   
93.
OBJECTIVE: Manual administration of IV contrast material results in unpredictable injection rates. Our purpose was to determine the effect of bolus tracking on overall abdominal helical CT scan quality, particularly on hepatic enhancement, in children with manually administered contrast media. MATERIALS AND METHODS: We compared 33 abdominal helical CT scans of 29 children in whom bolus tracking was used with 22 CT scans of a control group of 21 children in whom bolus tracking was not used. All contrast material was administered by manual injection. Qualitative assessment was made of organ and vessel enhancement and overall scan appearance. Quantitative assessment using region-of-interest cursors was performed at three anatomic levels, and the results for the two groups of children were compared. RESULTS: Qualitative comparison of enhancement parameters between the bolus tracking group (number given first) and the control group (number given second) yielded the following: splenic artifact in 9% versus 23% (p = .24); inferior vena cava flow artifact in 3% versus 27% (p = .01); scanning during the nephrographic phase in 89% versus 59% (p = .02); and good quality grade in 79% versus 64% (p = .23). Significantly greater hepatic enhancement (as measured in mean Hounsfield units) was achieved in the bolus tracking group than in the control group at the superior (48.5 versus 28.6; p < .001), middle (47.9 versus 32.3; p < .001), and inferior (48.2 versus 36.5; p = .01) levels. Hepatic enhancement increased significantly from the superior to the inferior level in the control group (p < .02), whereas enhancement was homogeneous in the bolus tracking group (p > .50). CONCLUSION: Bolus tracking provides improved contrast enhancement, including significantly greater hepatic enhancement, during abdominal helical CT in children in whom the rate of injection of contrast material is unpredictable.  相似文献   
94.
The intrathoracic manifestations of neurofibromatosis-I are protean and can, on occasion, mimic those of malignancy. Many of the intrathoracic findings are characteristic of the disease and can be expected to be present. Knowledge of the full spectrum of radiologic findings can thus be useful in preventing diagnostic error. Furthermore, an unexpected finding, such as rapid growth of a neural tumor, should be recognized as an atypical feature (suspicious for malignant degeneration) and result in further evaluation.  相似文献   
95.
96.
Our aim was to examine the feasibility of a totally laparoscopic insertion of a bifurcated aortofemoral bypass graft in a canine model and to compare the surgical results with those in control animals undergoing standard grafting and laparoscopic-assisted bypass procedures. Using a six-port approach, we exposed and cross clamped the aorta, tunneled a bifurcated Dacron graft, and performed an end-to-end aortic anastomosis while maintaining pneumoperitoneum by means of CO2. Proximal anastomoses were performed with 4/0 double-ended continuous Prolene sutures and distal anastomoses were performed through standard groin incisions. Total operating and aortic cross-clamp times were measured as was the total blood loss for each procedure. Clinical outcome was also documented. Eight female laboratory-bred hounds underwent successful totally laparoscopic aortobifemoral bypass grafting, eight underwent open grafting, and eight underwent laparoscopic-assisted bypass. Mean operating time was 193 minutes in the animals undergoing totally laparoscopic insertion vs. 156 minutes in the open group and 180 minutes in the laparoscopic-assisted group. Aortic cross-clamping time was also significantly longer at 87 minutes vs. 43 minutes (p < 0.001)=" in=" the=" totally=" laparoscopic=" group,=" but=" blood=" loss=" was=" less.=" all=" eight=" laparotomy=" and=" laparoscopic-assisted=" dogs=" were=" still=" alive=" with=" no=" complications=" at=" 28=" days,=" whereas=" three=" of=" the=" eight=" in=" the=" totally=" laparoscopic=" group=" showed=" evidence=" of=" temporary=" paraplegia.=" this=" experimental=" study=" demonstrates=" that=" a=" totally=" laparoscopic=" approach=" can=" be=" used=" to=" insert=" a=" bifurcated=" aortofemoral=" bypass=" with=" a=" proximal=" end-to-end=" anastomosis=" but=" currently=" does=" not=" save=" time=" and=" may=" increase=" the=" risk=" of=" neurologic=">Presented at the Twentieth Annual Meeting of the Peripheral Vascular Surgery Society, New Orleans, La., June 10, 1995.  相似文献   
97.
The success of vertical gastroplasty may be jeopardized by gastric leakage or ulceration due to failure of the technique. Reports of band erosion and staple-line leakage have led us to seek technical improvements to reduce technical failures. We describe a modification to the technique of band placement and a manoeuvre to aid the placement of staples when the TA90 staple gun is used.  相似文献   
98.
Many forms of gastric banding have been described and high reoperation rates reported. These can be mainly attributed to excess vomiting associated both with and without stenosis. Reflux oesophagitis and the ‘sump’ effect may be other causes. This paper examines the problems associated with banding leading to revisional surgery and introduces a new technique, ‘fundal supporting suture’, to correct these problems. Preliminary results on 126 bandings without the modification and 22 with the modification are presented.  相似文献   
99.
100.
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