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   9882篇
  免费   526篇
  国内免费   113篇
耳鼻咽喉   212篇
儿科学   216篇
妇产科学   305篇
基础医学   1153篇
口腔科学   125篇
临床医学   755篇
内科学   2855篇
皮肤病学   339篇
神经病学   726篇
特种医学   334篇
外科学   1043篇
综合类   235篇
一般理论   1篇
预防医学   558篇
眼科学   297篇
药学   807篇
  2篇
中国医学   70篇
肿瘤学   488篇
  2024年   7篇
  2023年   68篇
  2022年   293篇
  2021年   500篇
  2020年   179篇
  2019年   287篇
  2018年   347篇
  2017年   238篇
  2016年   235篇
  2015年   302篇
  2014年   336篇
  2013年   482篇
  2012年   788篇
  2011年   765篇
  2010年   435篇
  2009年   288篇
  2008年   520篇
  2007年   596篇
  2006年   642篇
  2005年   583篇
  2004年   564篇
  2003年   491篇
  2002年   444篇
  2001年   156篇
  2000年   148篇
  1999年   152篇
  1998年   56篇
  1997年   46篇
  1996年   43篇
  1995年   37篇
  1994年   25篇
  1993年   20篇
  1992年   47篇
  1991年   45篇
  1990年   42篇
  1989年   38篇
  1988年   43篇
  1987年   39篇
  1986年   24篇
  1985年   14篇
  1984年   17篇
  1983年   16篇
  1982年   7篇
  1981年   13篇
  1980年   11篇
  1979年   10篇
  1973年   8篇
  1971年   8篇
  1969年   7篇
  1967年   12篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
BackgroundThe EPI-SCAN study (Epidemiologic Study of COPD in Spain), conducted from May 2006 to July 2007, determined that the prevalence of COPD in Spain according to the GOLD criteria was 10.2% of the 40 to 80 years population. Little is known about the current geographical variation of COPD in Spain.ObjectivesWe studied the prevalence of COPD, its under-diagnosis and under-treatment, smoking and mortality in the eleven areas participating in EPI-SCAN. COPD was defined as a post-bronchodilator FEV1/FVC ratio <0.70 or as the lower limit of normal (LLN).ResultsThe ratio of prevalences of COPD among the EPI-SCAN areas was 2.7-fold, with a peak in Asturias (16.9%) and a minimum in Burgos (6.2 %) (P<.05). The prevalence of COPD according to LLN was 5.6% (95% CI 4.9–6.4) and the ratio of COPD prevalence using LLN was 3.1-fold, but with a peak in Madrid-La Princesa (10.1%) and a minimum in Burgos (3.2%) (P<.05). The ranking of prevalences of COPD was not maintained in both sexes or age groups in each area. Variations in under-diagnosis (58.6% to 72.8%) and under-treatment by areas (24.1% to 72.5%) were substantial (P<.05). The prevalence of smokers and former smokers, and cumulative exposure as measured by pack-years, and the age structure of each of the areas did not explain much of the variability by geographic areas. Nor is there any relation with mortality rates published by Autonomous Communities.ConclusionThere are significant variations in the distribution of COPD in Spain, either in prevalence or in under-diagnosis and under-treatment.  相似文献   
103.
Background: A new system has been developed that circulates warm water through a whole body garment worn by the patient during surgery. In this study the authors compared two different strategies for the maintenance of intraoperative normothermia. One strategy used a new water garment warming system that permitted active warming of both the upper and lower extremities and the back. The other strategy used a single (upper body) forced-air warming system.

Methods: In this prospective, randomized study, 53 adult patients were enrolled in one of two intraoperative temperature management groups during open abdominal surgery with general anesthesia. The water-garment group (n = 25) received warming with a body temperature (rectal) set point of 36.8[degrees]C. The forced-air-warmer group (n = 28) received routine warming therapy using upper body forced-air warming system (set on high). The ambient temperature in the operating room was maintained constant at approximately 20[degrees]C. Rectal, distal esophageal, tympanic, forearm, and fingertip temperatures were recorded perioperatively and during 2 h after surgery. Extubated patients in both groups were assessed postoperatively for shivering, use of additional warming devices, and subjective thermal comfort.

Results: The mean rectal and esophageal temperatures at incision, 1 h after incision, at skin closure, and immediately postoperatively were significantly higher (0.4-0.6[degrees]C) in the group that received water-garment warming when compared with the group that received upper body forced-air warming. The calculated 95% confidence intervals for the above differences in core temperatures were 0.7-0.1, 0.8-0.2, 0.8-0.2, and 0.9-0.1, retrospectively. In addition, 14 and 7% of patients in the control upper body forced-air group remained hypothermic (< 35.5[degrees]C) 1 and 2 h after surgery, respectively. No core temperature less than 35.5[degrees]C was observed perioperatively in any of the patients from the water-garment group. A similar frequency of the thermal stress events (shivering, use of additional warming devices, subjective thermal discomfort) was observed after extubation in both groups during the 2 h after surgery.  相似文献   

104.
Objectives: Cardioplegic arrest during cardiac surgery induces severe abnormalities of the pyruvate metabolism, which may affect functional recovery of the heart. We aimed to evaluate the effect of pyruvate and dichloroacetate administration during reperfusion on recovery of mechanical function and energy metabolism in the heart subjected to prolonged cardioplegic arrest. Methods: Four groups of rat hearts perfused in working mode were subjected to cardioplegic arrest (St. Thomas’ No. 1), 4 h of ischaemia at 8°C and reperfusion with either Krebs buffer alone (C) or with 2.8 mM pyruvate (P), with 1 mM dichloroacetate (D), or with a combination of both (PD). Mechanical function was recorded before cardioplegic arrest and at the end of experiments. In groups C and PD, additional experiments were performed using 31P nuclear magnetic resonance spectroscopy in non-working Langendorff mode to evaluate cardiac high-energy phosphate concentration changes throughout the experiment. Results: Improved recovery of cardiac output (% of the preischaemic value±SEM, n=9–12) was observed in all three treated groups (65.7±4.3, 59.5±5.2 and 59.5±5.3% in PD, P and D, respectively) as compared with C (42.2±4.6%; P<0.05). Recovery of coronary flow was improved from 66.4±3.8 in C to 94.9±8.6% in PD (P<0.05). The phosphocreatine recovery rate in the first minutes of reperfusion was increased from 9.9±1.5 in C to 31.5±4.3 μmol/min per g dry wt in PD (P<0.001). No differences were observed in ATP or phosphocreatine concentrations at the end of experiment. Conclusions: The administration of pyruvate and dichloroacetate improves the recovery of mechanical function following hypothermic ischaemia. Accelerated restoration of the energy equilibrium in the initial phase of reperfusion may underlie the metabolic mechanism of this effect.  相似文献   
105.
106.
OBJECTIVE: To analyse the need for operation for pyloric stenosis caused by duodenal ulcer over a period of 24 years (1976-1999). DESIGN: Retrospective study. SETTING: University hospital, Spain. SUBJECTS: 156 patients operated on for peptic pyloric stenosis. MAIN OUTCOME MEASURES: The number of patients operated on yearly were grouped into 4-year periods for statistical comparison. RESULTS: The number of cases operated on each year steadily decreased between 1976 and 1999. In the 1988-1991 period there was a significant reduction (p <0.05), which continued over the next two 4-year periods, particularly the last (p <0.01). CONCLUSION: Although we cannot use this study to establish a direct relation between the decrease in the indication for operations for peptic pyloric stenosis and the use of H2 antagonists, proton pump inhibitors, or treatment to eradicate Helicobacter pylori, we did find a significance difference between the years before and after the introduction of these drugs.  相似文献   
107.
We compared the incorporation of bone allografts with or without vancomycin in tibial defects of 18 pigs. High-quality radiographs, histological examination, immunological expression of metalloproteinase-13 (MMP-13) and transforming growth factor-beta 2 (TGFß2) indicated that there was no significant difference in bone allograft incorporation between up to 220 times the MIC (minimum inhibitory concentration) in bone allografts with 1 g of vancomycin in each 300 g of allograft or without this supplement.  相似文献   
108.
Background We analyzed the outcomes and factors associated with false-negative (FN) results of sentinel lymph node (SLN) biopsy findings in patients with cutaneous melanoma. SLN biopsy failure rate was defined as nodal recurrence in the biopsied regional basin without previous local or in-transit recurrence.Methods Between April 1997 and December 2004, a total of 1207 patients with cutaneous melanoma with a median Breslow thickness of 2.4 mm underwent SLN biopsy by preoperative and intraoperative lymphoscintigraphy combined with dye injection. In 228 cases, we found positive SLNs; of these, 220 underwent completion lymph node dissection (CLND). Median follow-up was 3 years.Results The SLN biopsy failure rate was 5.8% (57 of 979 SLN negative). Median time to occurrence of FN relapse after SLN biopsy was 16 months (range, 3–74 months). The FN SLN biopsy results correlated with primary tumor thickness >4 mm (P = .0012), primary tumor ulceration (P = .0002), primary tumor level of invasion Clark stage IV/V (P = .0005), and nodular melanoma histological type (P = .0375). Five-year overall survival, calculated from the date of primary tumor excision, in the FN group was 53.7%, which was not statistically significantly worse than the CLND group (56.8%; P = .9). The FN group was characterized by a higher ratio of two or more metastatic nodes and extracapsular involvement of lymph nodes after LND compared with the CLND group (P < .0001 and P < .0001, respectively). Additional detailed pathological review of FN SLN revealed metastatic disease in 14 patients, which decreased the SLN biopsy failure rate to 4.4% (43 of 979).Conclusions Survival of patients with FN results of SLN biopsy does not differ statistically significantly from that of patients undergoing CLND, although it is slightly lower. The SLN biopsy failure rate is approximately 5.0% in long-term follow-up and is associated mainly with the same factors that indicate a poor prognosis in primary melanoma.Preliminary results of this study were presented as an oral presentation during the Melanoma Session on the 59th Annual Cancer Symposium of the Society of Surgical Oncology, San Diego, CA, March 23–25, 2006.  相似文献   
109.
Measurements of bone biochemical markers are increasingly being used to evaluate the state of bone turnover in the management of bone metabolic diseases, especially osteoporosis. However, changes in the bone turnover rate vary with age. The aim of this study was to establish the laboratory reference range of serum bone-specific alkaline phosphatase (sBAP), serum type I collagen cross-linked C-terminal telopeptide (sCTx), and urine CTx (uCTx), based on values from 665 healthy Chinese women aged 20–80 years. We measured the levels of sBAP, sCTx, serum alkaline phosphatase (sALP), and uCTx and evaluated the age-related changes and their relationship with bone mineral density (BMD) in the anteroposterior (AP) lumbar spine, hip, and left forearm. We found significant correlations between biochemical markers and age, with coefficients of determination (R 2) of 0.358 for sBAP, 0.126 for sCTx, 0.125 for uCTx, and 0.336 for sALP. The net changes in different biochemical markers were inversely correlated with the rates of BMD loss in the AP lumbar spine. After correction for age, body weight, and height, the levels of the markers had significant negative correlations with the BMD of the AP lumbar spine, femoral neck, and ultradistal forearm. All four biochemical markers had the highest negative correlation with BMD of the AP lumbar spine (partial correlation coefficients of −0.366, −0.296, −0.290, and −0.258 for sBAP, sCTx, uCTx, and sALP, respectively). The mean and SD values of these markers in premenopausal and postmenopausal women with normal BMD values were used as the normal reference ranges. The reference ranges of sBAP, sCTx, and uCTx for pre- vs postmenopausal women were 17.3 ± 6.23 vs 18.9 ± 7.52 U/l, 3.18 ± 1.49 vs 3.23 ± 1.57 nmol/l, and 15.5 ± 11.4 vs 16.2 ± 12.4 nM bone collagen equivalents/mM urinary creatinine, respectively. Levels of the bone formation marker (sBAP) and bone resorption markers (sCTx, uCTx) increased rapidly in women with osteopenia or osteoporosis, indicating that they may be sensitive markers to determine the bone turnover rate in healthy Chinese women.  相似文献   
110.
目的:研究长链非编码 RNA (LncRNA ) LOC100288637在肝癌中的表达差异,对肝癌细胞增殖的影响及相关机制。方法分析GEO数据集GSE58043和GSE10694,得出LOC100288637及hsa‐miR‐101‐3p在肝癌组织中差异表达,RNA‐hy‐brid分析LOC100288637与hsa‐miR‐101‐3p的结合具有可能性。逆转录‐聚合酶链式反应在组织和细胞水平检测LOC100288637表达量。荧光原位杂交观察LOC100288637在细胞中的定位。敲低LOC100288637后CCK‐8检测细胞增殖情况。过表达hsa‐miR‐101‐3p后,检测 LOC100288637的变化。结果 LOC100288637在肝癌组织中的表达量高于癌旁组织( P<0.05);LOC100288637在肝癌细胞系中的表达量高于肝细胞系(P<0.05)。LOC100288637在 HepG2细胞核质均有表达,以细胞质居多。敲低LOC100288637后 HepG2细胞增殖活性降低(P<0.01)。过表达hsa‐miR‐101‐3p后,LOC100288637表达量下降(P<0.05)。结论 LncRNA LOC100288637可能在肝癌发生,发展过程中起重要作用并接受hsa‐miR‐101‐3p靶向调控影响肝癌细胞的增殖。  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