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   317135篇
  免费   8418篇
  国内免费   118篇
耳鼻咽喉   3433篇
儿科学   11457篇
妇产科学   6400篇
基础医学   38060篇
口腔科学   6218篇
临床医学   23896篇
内科学   56734篇
皮肤病学   4831篇
神经病学   30979篇
特种医学   14882篇
外国民族医学   22篇
外科学   50459篇
综合类   2971篇
一般理论   42篇
预防医学   25654篇
眼科学   5865篇
药学   19312篇
中国医学   887篇
肿瘤学   23569篇
  2023年   819篇
  2022年   557篇
  2021年   1343篇
  2020年   1250篇
  2019年   1506篇
  2018年   24561篇
  2017年   19557篇
  2016年   22405篇
  2015年   3882篇
  2014年   4074篇
  2013年   6449篇
  2012年   14148篇
  2011年   28750篇
  2010年   23148篇
  2009年   14368篇
  2008年   27273篇
  2007年   29788篇
  2006年   8991篇
  2005年   10475篇
  2004年   11189篇
  2003年   12106篇
  2002年   10257篇
  2001年   5889篇
  2000年   7475篇
  1999年   4219篇
  1998年   1798篇
  1997年   1504篇
  1996年   1122篇
  1995年   942篇
  1994年   942篇
  1993年   857篇
  1992年   959篇
  1991年   885篇
  1990年   896篇
  1989年   868篇
  1988年   732篇
  1987年   779篇
  1986年   658篇
  1985年   874篇
  1984年   798篇
  1983年   682篇
  1982年   693篇
  1981年   628篇
  1980年   630篇
  1979年   622篇
  1978年   541篇
  1977年   570篇
  1976年   486篇
  1975年   520篇
  1974年   514篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Existing knowledge and present experience relating to the indications for imaging techniques in trauma surgery were summarised, screened and considered in different ways by representatives of various professional scientific bodies, with the aim of finding what procedures should be implemented as the primary examination techniques after a careful clinical examination when particular posttraumatic situations affecting the knee, foot, ankle, or hand were found. In the course of an interdisciplinary consensus conference the evidence-based recommendations prepared by a panel were discussed and modified, giving rise to statements on the suitability of the given imaging techniques in 28 different clinical situations immediately after a clinical examination, based on scientific evidence and medical consensus. The degree of consensus was measured and carefully documented. These statements were transformed into decision algorithms and presented to doctors working in accident and emergency medicine during a conference on trauma surgery, with the aim of.measuring the acceptance of the statements among those attending the trauma surgery meeting. The remarks made by the participants during the discussion and the results of the acceptance measurements clearly show the need for further discussion among experts.  相似文献   
992.
PURPOSE: Hypotension is the most frequent complication of spinal anesthesia in pregnant patients. This study was designed to identify patients at risk for postspinal hypotension based on preoperative vital signs before and after an orthostatic challenge. METHODS: Forty healthy women scheduled for elective Cesarean section were enrolled in this prospective trial. Blood pressure (BP) and heart rate (HR) were recorded with the patient in the lateral supine position and after standing up. After a bupivacaine spinal anesthetic, BP was obtained every two minutes for 30 min. Ephedrine treatment was administered based on the degree of hypotension observed. Hemodynamic parameters were correlated to ephedrine requirements (Spearman's rank order correlation). RESULTS: There was a significant correlation in baseline maternal HR and ephedrine requirements (P=0.005). The degree of orthostatic changes in mean arterial BP and HR did not correlate with postspinal hypotension. CONCLUSIONS: Baseline HR may be predictive of obstetric spinal hypotension. Higher baseline HR, possibly reflecting a higher sympathetic tone, may be a useful parameter to predict postspinal hypotension.  相似文献   
993.
994.
The reduction of NBT to formazan has been suggested as an indicator of the reduction potential of biological systems. An increase in the amount of reduced formazan reflects the activation of the hexose monophosphate shunt of phagocytes cultivated in vitro, as a result of cellular stimulation by chemical or biological factors, or during phagocytosis. This phenomenon has been widely used for the determination of activated phagocytes by different methods. However, the technical limitations of these methods have not been evaluated carefully. In the investigations presented here threesolvents for formazan, pyridine, dioxane and dimethylformamide, have been tested for their suitability as extraction agents. For each solvent the optimal wavelength for photometric evaluation has been determined and dose relation curves between dissolved formazan and OD have been established. Several factors (time, temperature, pH, contamination with water or acid) affecting the dissolving properties and stability of formazan in different solvents have been investigated. With the solvents tested, dioxane proved to be the most suitable agent for extracting NBF. Thus, a methodology for the quantitative evaluation of NBT has been established. This method can be used for the identification of activators as well as of inhibitors of the phagocyte system.  相似文献   
995.
996.
Current activities in the case management of patients with post-traumatic stress disorders are reported. In 2002 a project was initiated by accident insurance associations. The aim is to detect accident victims with stress disorder at an early stage and to avoid medical mismanagement.  相似文献   
997.
There is some controversy over the treatment of acromioclavicular injuries. The use of the Rockwood classification as the basis for decisions on whether operative or nonoperative treatment is indicated is discussed critically, and the authors' preferred operative technique is described and illustrated by examples. We treat injuries classified according to the Rockwood classification as types I and II with conservative methods. In type III injuries the patient's age, job and free time activities determine whether or not surgery is indicated. In the case of type IV or type VI injuries we always perform temporary internal fixation of the acromioclavicular joint, using transarticular K-wire fixation or hookplate osteosynthesis. Satisfactory results of both operative and nonoperative treatment are reported in the literature. The authors' own results are presented.  相似文献   
998.
A promising treatment method for type 1 diabetes mellitus is transplantation of pancreatic islets containing beta-cells. The aim of this study was to develop an MR technique to monitor the distribution and fate of transplanted pancreatic islets in an animal model. Twenty-five hundred purified and magnetically labeled islets were transplanted through the portal vein into the liver of experimental rats. The animals were scanned using a MR 4.7-T scanner. The labeled pancreatic islets were clearly visualized in the liver in both diabetic and healthy rats as hypointense areas on T2*-weighted MR images during the entire measurement period. Transmission electron microscopy confirmed the presence of iron-oxide nanoparticles inside the cells of the pancreatic islets. A significant decrease in blood glucose levels in diabetic rats was observed; normal glycemia was reached 1 week after transplantation. This study, therefore, represents a promising step toward possible clinical application in human medicine.  相似文献   
999.
Schizophrenia is characterized by significant cognitive impairments that predict impairment in multiple domains of community outcome. Pharmacologic and psychosocial treatments are available that address these cognitive deficits. There is growing evidence that patients taking second-generation antipsychotic medications perform better on tests of cognitive function than those taking conventional neuroleptics. In addition, there have been a number of medications from other classes being investigated as cognitive enhancers for schizophrenia. Cognitive rehabilitation approaches focus on bypassing, compensating for, or remediating observed impairments in cognitive function. Outcomes for patients have been improved by cognitive remediation, errorless learning, and the use of supportive environments. Combining the newest pharmacologic interventions for cognitive dysfunction with state of the art psychosocial treatments aimed at ameliorating or bypassing deficits is likely to produce the most favorable outcomes for individuals with schizophrenia.  相似文献   
1000.
PURPOSE: The goal of this study was to analyze the effect of positive end-expiratory pressure (PEEP), with and without a lung recruitment maneuver, on dead space. METHODS: 16 anesthetized patients were sequentially studied in three steps: 1) without PEEP (ZEEP), 2) with 5 cm H(2)O of PEEP and 3) with 5 cm H(2)O of PEEP after an alveolar recruitment strategy (ARS). Ventilation was maintained constant. The single breath test of CO(2) (SBT-CO(2)), arterial oxygenation, end-expiratory lung volume (EELV) and respiratory compliance were recorded every 30 min. RESULTS: Physiological dead space to tidal volume decreased after ARS (0.45 +/- 0.01) compared with ZEEP (0.50 +/- 0.07, P < 0.05) and PEEP (0.51 +/- 0.06, P < 0.05). The elimination of CO(2) per breath increased during PEEP (25 +/- 3.3 mL.min(-1)) and ARS (27 +/- 3.2 mL.min(-1)) compared to ZEEP (23 +/- 2.6 mL.min(-1), P < 0.05), although ARS showed larger values than PEEP (P < 0.05). Pa-etCO(2) difference was lower after recruitment (0.9 +/- 0.5 kPa, P < 0.05) compared to ZEEP (1.1 +/- 0.5 kPa) and PEEP (1.2 +/- 0.5 kPa). Slope II increased after ARS (63 +/- 11%/L, P < 0.05) compared with ZEEP (46 +/- 7.7%/L) and PEEP (56 +/- 10%/L). Slope III decreased significantly after recruitment (0.13 +/- 0.07 1/L) compared with ZEEP (0.21 +/- 0.11 1/L) and PEEP (0.18 +/- 0.10 1/L). The angle between slope II and III decreased only after ARS. After lung recruitment, PaO(2), EELV, and compliance increased significantly compared with ZEEP and PEEP. CONCLUSION: Lung recruitment improved the efficiency of ventilation in anesthetized patients.  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