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   1995篇
  免费   213篇
  国内免费   2篇
耳鼻咽喉   16篇
儿科学   61篇
妇产科学   60篇
基础医学   318篇
口腔科学   9篇
临床医学   276篇
内科学   313篇
皮肤病学   52篇
神经病学   115篇
特种医学   33篇
外科学   253篇
综合类   42篇
一般理论   1篇
预防医学   239篇
眼科学   105篇
药学   155篇
中国医学   1篇
肿瘤学   161篇
  2021年   23篇
  2020年   20篇
  2019年   30篇
  2018年   41篇
  2017年   20篇
  2016年   45篇
  2015年   38篇
  2014年   46篇
  2013年   62篇
  2012年   91篇
  2011年   96篇
  2010年   43篇
  2009年   64篇
  2008年   76篇
  2007年   102篇
  2006年   100篇
  2005年   77篇
  2004年   77篇
  2003年   67篇
  2002年   71篇
  2001年   59篇
  2000年   68篇
  1999年   49篇
  1998年   33篇
  1997年   31篇
  1996年   18篇
  1995年   19篇
  1994年   25篇
  1993年   24篇
  1992年   37篇
  1991年   27篇
  1990年   30篇
  1989年   30篇
  1988年   27篇
  1987年   23篇
  1986年   36篇
  1985年   51篇
  1984年   28篇
  1983年   19篇
  1982年   16篇
  1979年   19篇
  1978年   17篇
  1977年   26篇
  1976年   20篇
  1974年   22篇
  1973年   17篇
  1972年   16篇
  1971年   30篇
  1970年   32篇
  1969年   19篇
排序方式: 共有2210条查询结果,搜索用时 15 毫秒
91.
OBJECTIVES: We sought to develop and evaluate a risk adjustment model for in-hospital mortality following percutaneous coronary intervention (PCI) procedures using data from a large, multi-center registry. BACKGROUND: The 1998-2000 American College of Cardiology-National Cardiovascular Data Registry (ACC-NCDR) dataset was used to overcome limitations of prior risk-adjustment analyses. METHODS: Data on 100,253 PCI procedures collected at the ACC-NCDR between January 1, 1998, and September 30, 2000, were analyzed. A training set/test set approach was used. Separate models were developed for presentation with and without acute myocardial infarction (MI) within 24 h. RESULTS: Factors associated with increased risk of PCI mortality (with odds ratios in parentheses) included cardiogenic shock (8.49), increasing age (2.61 to 11.25), salvage (13.38) urgent (1.78) or emergent PCI (5.75), pre-procedure intra-aortic balloon pump insertion (1.68), decreasing left ventricular ejection fraction (0.87 to 3.93), presentation with acute MI (1.31), diabetes (1.41), renal failure (3.04), chronic lung disease (1.33); treatment approaches including thrombolytic therapy (1.39) and non-stent devices (1.64); and lesion characteristics including left main (2.04), proximal left anterior descending disease (1.97) and Society for Cardiac Angiography and Interventions lesion classification (1.64 to 2.11). Overall, excellent discrimination was achieved (C-index = 0.89) and application of the model to high-risk patient groups demonstrated C-indexes exceeding 0.80. Patient factors were more predictive in the MI model, while lesion and procedural factors were more predictive in the analysis of non-MI patients. CONCLUSIONS: A risk adjustment model for in-hospital mortality after PCI was successfully developed using a contemporary multi-center registry. This model is an important tool for valid comparison of in-hospital mortality after PCI.  相似文献   
92.
Birt-Hogg-Dubé (BHD) syndrome is an autosomal dominant genodermatosis characterized by the development of small dome-shaped papules on the face, neck, and upper trunk (fibrofolliculomas). In addition to these benign hair follicle tumors, BHD confers an increased risk of renal neoplasia and spontaneous pneumothorax. To date, there has been no systematic pathologic analysis of the renal tumors associated with this syndrome. We reviewed 130 solid renal tumors resected from 30 patients with BHD in 19 different families. Preoperative computed tomography scans demonstrated a mean of 5.3 tumors per patient (range 1-28 tumors), the largest tumors averaging 5.7 cm in diameter (+/- 3.4 cm, range 1.2-15 cm). Multiple and bilateral tumors were noted at an early age (mean 50.7 years). The resected tumors consisted predominantly of chromophobe renal cell carcinomas (44 of 130, 34%) or of hybrid oncocytic neoplasms that had areas reminiscent of chromophobe renal cell carcinoma and oncocytoma (65 of 130, 50%). Twelve clear cell (conventional) renal carcinomas (12 of 130, 9%) were diagnosed in nine patients. These tumors were on average larger (4.7 +/- 4.2 cm) than the chromophobe (3.0 +/- 2.5 cm) and hybrid tumors (2.2 +/- 2.4 cm). Microscopic oncocytosis was found in the renal parenchyma of most patients, including the parenchyma of five patients with evidence of clear cell renal cell carcinoma. Our findings suggest that microscopic oncocytic lesions may be precursors of hybrid oncocytic tumors, chromophobe renal cell carcinomas, and perhaps clear cell renal cell carcinomas in patients with BHD syndrome. Recognition by the pathologist of the unusual renal tumors associated with BHD may assist in the clinical diagnosis of the syndrome.  相似文献   
93.
Purpose: The aim of this retrospective study was to determine the rate of visually significant posterior capsular opacification formation after cataract surgery for Australian Aborigines living in rural or remote areas in the ‘Top End’ of the Northern Territory, Australia, and then to assess these patients’ outcomes after capsulotomy. Methods: Aboriginal patients living in remote areas of the Top End of the Northern Territory who underwent cataract surgery between 1994 and 1999 were identified from records at the three major hospitals in the region. The presence of posterior capsular opacification (PCO) was determined by clinical examination. The primary endpoint for this study was the presence of axial opacification of the posterior capsule and the need for subsequent Nd:YAG posterior capsulotomy to improve sight. Linear regression analysis of the time from surgery to follow up and the number of eyes requiring Nd:YAG capsulotomy was performed. Operated eyes were grouped according to the interval between surgery and follow up (Group 1: follow up within 1 year of surgery, n= 25; Group 2: follow up 1?3 years after surgery, n= 42; Group 3: follow up 3?5 years after surgery, n= 51). Results: One hundred and eighteen operated eyes were examined. Eyes in Group 3 were found to have the highest incidence of visually significant PCO (27.5%). There were more eyes requiring capsulotomy after 3 years than after 1 year following surgery. Linear regression analysis revealed an odds ratio of 1.4 (P = 0.07). All nine eyes in the 1?3 year group that had developed visually significant PCO had undergone extra‐capsular cataract extraction. Conclusions: For the remote Aboriginal patient who has undergone cataract surgery, there is a relatively minor chance of developing PCO within the first postoperative year regardless of the type of surgery undertaken. This study illustrates that the longer the time after surgery the greater the chance of developing visually significant PCO. For the remote Aboriginal patient there is a high chance (approximately 28%) of developing visually significant PCO within 5 years after cataract surgery. These figures are lower than those reported from other parts of Australia.  相似文献   
94.
The need for an enterprise-wide person-centric approach to patient identification is presented, along with the challenges to achieving that objective and guidelines to the actions and technology that will support the enterprise view.  相似文献   
95.
OBJECTIVES: To revise and update a risk adjustment model for in-hospital mortality following percutaneous coronary intervention (PCI) procedures using all data from the 1.1 version of the American College of Cardiology National Cardiovascular Data Registry (ACC-NCR). BACKGROUND: A model based on data received at the ACC-NCDR from 1998-2000 was previously reported. The revision of this mortality model reflects all of the data submitted using 1.1 data specifications and collected through the second quarter of 2001. The model was applied to selected high-risk subgroups from a sample of data collected during the year 2001 from version 2.0 of the NCDR. METHODS: Data on 173,743 PCI procedures collected at the ACC-NCDR between January 1, 1998 and March 31, 2001 were analyzed. A mortality model was generated as well as separate models for presentation with and without acute myocardial infarction within 24 hours. The model was used to generate predicted mortalities that were compared to observed mortalities in more current high-risk patient subgroups in the NCDR. RESULTS: The same factors that were previously found to be associated with increased risk of PCI mortality were re-verified in the current analysis. Inclusion of the complete 1.1 dataset produced some changes in the regression weights and the constant value. Excellent discrimination was achieved in the revised model (C-Index = 0.89). The model was applied to high-risk patient groups from data collected on 76,249 during the calendar year 2001 using the 2.0 NCDR data elements and definitions. These analyses showed a high level of agreement between observed mortality of each subgroup and the predicted mortality rates generated from the revised 1.1 PCI mortality model. CONCLUSIONS: Risk adjustment models for in-hospital mortality following PCI for all patients and for those with and without recent MI were regenerated using all data collected from the 1.1 data specifications of the ACC-NCDR and validated on high-risk groups from data collected during 2001 under data version 2.0 of the NCDR. These models reflect the most up-to-date analysis of mortality prediction from this large, multi-center national database.  相似文献   
96.
Anopheline vectors and malaria transmission were studied in 2 river-irrigated, rice-growing districts of eastern Afghanistan from May 1995 to December 1996. Clinical malaria was monitored in 12 rural villages (population 14,538) by passive case detection at local clinics. Adult mosquitoes were collected by space-spraying of living quarters and stables and by cattle bait catches. Mosquito head-thoraces (17,255 specimens) were tested for Plasmodium falciparum and P. vivax circumsporozoite protein (CSP) using enzyme-linked immunosorbent assay. The recorded incidence of P. vivax and P. falciparum was 199 and 41 episodes per 1000 person years, respectively. Twelve species of anopheline were recorded; Anopheles stephensi comprised 82% and A. culicifacies 5%. Eight species tested positive for CSP: A. stephensi, A. culicifacies, A. fluviatilus, A. annularis, A. pulcherrimus, A. maculatus, A. splendidus and A. superpictus. Among infected mosquitoes 46% were positive for P. falciparum, 45% for P. vivax VK-247, and 9% for P. vivax PV-210. Estimates of the feeding rates of infective vectors on humans indicated that A. stephensi would contribute 76% of infective bites, A. fluviatilis and A. pulcherrimus 7% each, and A. culicifacies and A. superpictus 3% each. The overall infective vector feeding rate correlated with the P. vivax incidence rate in the human population. The conventional view of A. culicifacies being the main rural vector and A. stephensi important only in urban settings needs to be reconsidered in western outreaches of the Indo-Pakistan subcontinent.  相似文献   
97.
Hexavalent chromium [Cr(VI)] and ozone are produced in many arc-welding processes. Cr(VI) is formed when welding with chromium-containing alloys and is a suspected carcinogen. Ozone is formed by the action of ultraviolet light from the arc on oxygen and can cause severe irritation to the eyes and mucous membranes. Previous work has demonstrated that reduction of sodium and potassium in manual metal arc-welding electrodes leads to substantial reductions in Cr(VI) concentrations in the fume as well as a reduction in the fume formation rate. In this paper replacement of potassium by lithium in a tubular wire welding electrode (self-shielding flux-cored) is shown to give reductions in Cr(VI) concentrations and fume formation rates. Previous work has also demonstrated that use of a tubular wire (metal cored) containing 1% zinc can, under certain conditions, result in a reduction in Cr(VI) formation rate and in ozone concentration near the arc but with a rise in the total fume formation rate. The effects of different shield gases and different levels of zinc are examined. An experimental chromium-containing tubular wire with 1% zinc was used with the following shield gases: argon, Argoshield 5, Argoshield 20, Helishield 101, Ar + 2% CO2, Ar + 5% CO2, Ar + 1% O2 and Ar + 2% O2. The wire gave > 98% reduction in Cr(VI) formation rate compared to the control wire provided the shield gas contained no oxygen. When the shield gas did contain oxygen, 1% zinc enhanced Cr(VI) formation rate, resulting in more than double the rates measured when welding with the control wire. Experiments with zinc concentrations, from 0.018 to 0.9% using Helishield 101, gave results indicating that there is an optimum zinc concentration from the point of view of Cr(VI) reduction. Implications of the use of lithium or zinc on the overall exposure risk are discussed.  相似文献   
98.
99.
100.
Background/Purpose: Reconstructive surgery often is limited by the availability of normal tissue. Tissue engineering provides promise in the development of [ldquo ]artificial tissues.[rdquo ] The purpose of this study was to test the efficacy and viability of the use of a biologic surgical adhesive TISSEEL in combining engineered bronchial epithelium with engineered cartilage. Methods: Using isolated human cells, bronchial epithelium and mature cartilage were engineered. Using a contact adhesive technique, TISSEEL was used to biologically fuse the bronchial epithelium and the cartilage. The fused composite then was supported for 5 days in tissue culture. The mechanical properties of the adhesion were tested, and the construct was studied morphologically to assess viability of the cartilage and the bronchial epithelium. The bronchial epithelium showed a normal cell size (337.2 [mu ]m2) and epithelial thickness (46.47 [mu ]m). Results: TISSEEL was effective in fusing the epithelium to the cartilage. The construct remained viable for 5 days in culture. There was no difference in the dimensions of the bronchial epithelium or the epithelial cells. Mechanical adhesion was achieved. Conclusions: Biologically compatible fibrin glue is an effective surgical adhesive that allows the tissue types to be fused while remaining viable and morphologically accurate. Surgical adhesives may show promise in the development of composite tissue development in the field of bioengineering. J Pediatr Surg 37:1034-1037.  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