首页 | 官方网站   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   4188篇
  免费   30篇
工业技术   4218篇
  2024年   2篇
  2023年   5篇
  2022年   9篇
  2021年   26篇
  2020年   7篇
  2019年   16篇
  2018年   17篇
  2017年   17篇
  2016年   32篇
  2015年   9篇
  2014年   16篇
  2013年   29篇
  2012年   19篇
  2011年   22篇
  2010年   20篇
  2009年   24篇
  2008年   17篇
  2007年   18篇
  2006年   21篇
  2005年   4篇
  2004年   7篇
  2003年   9篇
  2002年   2篇
  2001年   7篇
  2000年   3篇
  1999年   138篇
  1998年   1217篇
  1997年   673篇
  1996年   421篇
  1995年   223篇
  1994年   182篇
  1993年   247篇
  1992年   26篇
  1991年   49篇
  1990年   52篇
  1989年   61篇
  1988年   63篇
  1987年   53篇
  1986年   34篇
  1985年   37篇
  1983年   8篇
  1982年   17篇
  1981年   22篇
  1980年   20篇
  1979年   2篇
  1978年   8篇
  1977年   96篇
  1976年   198篇
  1975年   10篇
  1974年   2篇
排序方式: 共有4218条查询结果,搜索用时 15 毫秒
991.
992.
993.
994.
995.
996.
Clinical and haemodynamic profile of 107 adult patients above the age of 15 years with TOF was analysed. Cardiac catherization and selective cine-angiography were performed in all cases. Infundibular pulmonary stenosis, mal-alignment type of ventricular septal defect, mitral-aortic fibrous continuity and equal systolic pressures in both the ventricles and aorta were considered mandatory for the diagnosis of Tetralogy of Fallot. Aortic regurgitation was seen in 26 cases (24%), tricuspid regurgitation in 22 cases (21%), absent pulmonary valve in 3 cases (3%), branch pulmonary artery stenosis in 9 case (8.4%), major aortopulmonary collaterals in 15 cases (14%), right atrial pressure was more than 10 mmHg in 10 cases (11%) and right ventricular end diastolic pressure more than 9 mmHg in 73 cases (68%). The left ventricular end diastolic pressure was above 13 mmHg in 58 cases (54%).  相似文献   
997.
998.
Indications for laparoscopic pelvic lymphadenectomy prior to radical prostatectomy have not been established. Criteria to predict lymph node metastases were derived from the preoperative evaluations of 164 prostate cancer patients undergoing pelvic lymphadenectomy. Decision analysis was used to determine which criteria would be optimal indicators for laparoscopic pelvic lymphadenectomy prior to intended radical prostatectomy. Besides a digital rectal examination suggesting uncontained tumor, which was the best indication for laparoscopic pelvic lymphadenectomy, the most useful criteria were sonographic tumor volume > or = 3 cc and prostate-specific antigen (PSA) > or = 20 ng/mL. If either parameter was met, the sensitivity for identifying patients with pelvic lymph node metastases was 88 percent and the positive predictive value was 42 percent. When both were met, the sensitivity fell to 47 percent but the positive predictive value increased to 67 percent. A combination of Gleason biopsy score and PSA was the best criterion that was independent of transrectal ultrasonography. Using a PSA > or = 15 ng/mL for tumors with Gleason biopsy score > or = 7 or a PSA > or = 25 ng/mL for tumors with a Gleason biopsy score of 5-6 had a sensitivity of 71 percent and positive predictive value of 48 percent for identifying patients with pelvic lymph node metastases. In selecting patients for laparoscopic pelvic lymphadenectomy prior to radical retropubic prostatectomy, criteria with a positive predictive value greater than 39 percent maximize the utility of laparoscopic pelvic lymphadenectomy. Prior to radical perineal prostatectomy, laparoscopic pelvic lymphadenectomy will identify pelvic lymph node metastases that would otherwise be undetected by prostatectomy alone. The sensitivity of selection criteria, therefore, should be increased, as long as the positive predictive value remains above 20 percent.  相似文献   
999.
OBJECTIVES: To assess the hypothesis of the existence of differential therapeutic effort according to the socioeconomic status of the patients admitted to the hospital by acute myocardial infarction. PATIENTS AND METHODS: We study retrospectively 592 patients admitted to the intensive care units from six public hospitals from the Spanish region of Valencia, using data from two cohort studies focused on the study of in-hospital inequalities in health. The socioeconomic status was measured using the British occupational classification. The therapeutic effort predicted for the severity of illness was determined using a regression model that included the logarithm of Therapeutic Intervention Scoring System (TISS) score as the dependent variable and Simplified Acute Physiology Score (SAPS) score and Killip group as predictors. The patients whose observed TISS was 3 or more pointless than predicted were considered as infra-treated. The effect of potential confounders was controlled using unconditional logistic regression analysis. RESULTS: The proportion of infra-treated patients was inversely related to socioeconomic status chi 2 for tendency = 4.31, P = 0.0378). The logistic regression analysis showed a negative association between age and therapeutic effort (p < 0.0001) but not between therapeutic effort and socioeconomic status, after controlling the effect of age (p = 0.2150). DISCUSSION: Our results suggest that older patients receive less relative therapeutic effort, measured by TISS score, than younger patients. The differential therapeutic effort observed in the crude analysis seem attributable to the higher age of the patients in the lower socioeconomic strata.  相似文献   
1000.
The pathogenic role of antineutrophil cytoplasmic autoantibodies (ANCA) remains controversial because of the difficulty in explaining how extracellular ANCA can interact with intracellular primary granule constituents. It has been postulated that cytokine priming of neutrophils (PMN), as may occur during a prodromal infection, is an important trigger for mobilization of granules to the cell surface, where they may interact with ANCA. We show by electron microscopy that apoptosis of unprimed PMN is also associated with the translocation of cytoplasmic granules to the cell surface and alignment just beneath an intact cell membrane. Immunofluorescent microscopy and FACS analysis demonstrate reactivity of ANCA-positive sera and antimyeloperoxidase antibodies with apoptotic PMN, but not with viable PMN. Moreover, we show that apoptotic PMN may be divided into two subsets, based on the presence or absence of granular translocation, and that surface immunogold labeling of myeloperoxidase occurs only in the subset of PMN showing translocation. These results provide a novel mechanism that is independent of priming, by which ANCA may gain access to PMN granule components during ANCA-associated vasculitis.  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-23

京公网安备 11010802026262号