全文获取类型
收费全文 | 17984篇 |
免费 | 937篇 |
国内免费 | 125篇 |
专业分类
耳鼻咽喉 | 168篇 |
儿科学 | 396篇 |
妇产科学 | 387篇 |
基础医学 | 2115篇 |
口腔科学 | 422篇 |
临床医学 | 1323篇 |
内科学 | 5423篇 |
皮肤病学 | 457篇 |
神经病学 | 1542篇 |
特种医学 | 349篇 |
外科学 | 2476篇 |
综合类 | 98篇 |
一般理论 | 8篇 |
预防医学 | 1172篇 |
眼科学 | 329篇 |
药学 | 1101篇 |
中国医学 | 40篇 |
肿瘤学 | 1240篇 |
出版年
2024年 | 14篇 |
2023年 | 144篇 |
2022年 | 322篇 |
2021年 | 733篇 |
2020年 | 333篇 |
2019年 | 661篇 |
2018年 | 724篇 |
2017年 | 429篇 |
2016年 | 435篇 |
2015年 | 475篇 |
2014年 | 788篇 |
2013年 | 861篇 |
2012年 | 1585篇 |
2011年 | 1566篇 |
2010年 | 835篇 |
2009年 | 746篇 |
2008年 | 1206篇 |
2007年 | 1215篇 |
2006年 | 1045篇 |
2005年 | 1010篇 |
2004年 | 930篇 |
2003年 | 767篇 |
2002年 | 770篇 |
2001年 | 133篇 |
2000年 | 142篇 |
1999年 | 140篇 |
1998年 | 116篇 |
1997年 | 108篇 |
1996年 | 81篇 |
1995年 | 65篇 |
1994年 | 56篇 |
1993年 | 49篇 |
1992年 | 63篇 |
1991年 | 48篇 |
1990年 | 58篇 |
1989年 | 32篇 |
1988年 | 38篇 |
1987年 | 19篇 |
1986年 | 19篇 |
1985年 | 22篇 |
1984年 | 25篇 |
1983年 | 17篇 |
1982年 | 14篇 |
1981年 | 16篇 |
1980年 | 17篇 |
1979年 | 19篇 |
1975年 | 14篇 |
1973年 | 14篇 |
1971年 | 14篇 |
1970年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
New lanostanoids from the fungus Ganoderma concinna 总被引:1,自引:0,他引:1
González AG León F Rivera A Padrón JI González-Plata J Zuluaga JC Quintana J Estévez F Bermejo J 《Journal of natural products》2002,65(3):417-421
Three new compounds, 5 alpha-lanosta-7,9(11),24-triene-3beta-hydroxy-26-al (1), 5 alpha-lanosta-7,9(11),24-triene-15 alpha-26-dihydroxy-3-one (2), and 8 alpha,9 alpha-epoxy-4,4,14 alpha-trimethyl-3,7,11,15,20-pentaoxo-5 alpha-pregnane (3), were isolated from Ganoderma concinna along with 12 known compounds. The structures of compounds 1 and 2 were determined on the basis of MS and NMR studies. The structure of 3 was determined by MS, NMR, and single-crystal X-ray diffraction. Compounds 1, 2, and 3 induce apoptosis in human promyelocytic leukemia HL-60 cells, as indicated by examining the morphological features of cells and detection of DNA fragmentation by gel electrophoresis. 相似文献
992.
993.
The cellular origin of the acetylcholinesterase (AChE) associated with amyloid plaques in the Alzheimer's disease (AD) brain is unknown. In this study we report that amyloid beta-peptides (Abeta) increased AChE levels in both neuronal and astrocytic primary cultures, supporting the possibility that both neurons and glia may make a direct contribution to the pool of AChE seen around amyloid deposits in the AD brain. 相似文献
994.
Golpe R Mateos A Pérez-Valcárcel J Lapeña JA García-Figueiras R Blanco J 《Respiration; international review of thoracic diseases》2003,70(3):306-309
Crohn's disease (CD) can be associated with respiratory involvement. Multiple pulmonary nodules are an infrequent finding in patients with CD. When they are found, histology usually shows sterile necrobiotic nodules, which are spherical aggregates of neutrophils, which frequently cavitate. We report a patient with inactive CD treated with mesalazine, who presented with multiple pulmonary nodules. Transthoracic biopsy of one of the nodules disclosed a benign, nongranulomatous inflammatory lymphoid infiltration. The radiographic abnormalities responded well to oral prednisone. Focal, nongranulomatous lymphoid infiltration thus must be considered in the differential diagnosis of multiple pulmonary nodules in patients with CD. 相似文献
995.
Morales-Espinoza EM Sánchez-Pérez HJ García-Gil Mdel M Vargas-Morales G Méndez-Sánchez JD Pérez-Ramírez M 《Salud pública de México》2003,45(5):379-388
OBJECTIVE: To assess the prevalence of intestinal parasitic infections among children in highly deprived areas, and its possible association with demographic and socioeconomic indicators. MATERIAL AND METHODS: From March to September 1998 in a convenience sample of 32 communities of the border region of Chiapas, Mexico, selected at random based on the level of poverty and distance from the community to the nearest health care unit (< 1 hour; 1 hour or more), one of every four households with children under 15 years of age was randomly selected to provide three stool samples from their children (n 1478). Bivariate and multivariate (generalized linear models for correlated binary data), analysis were performed. RESULTS: The global prevalence of intestinal parasitosis was 67% (95% confidence interval [CI] 64-70%). Sixty percent had multiple parasites. The prevalence of Entamoeba histolytica/E dispar was 51.2%, that of Giardia lamblia 18.3%, and that of Ascaris lumbricoides 14.5%. Multivariate analysis showed that age and speaking an indigenous language were significantly associated with the presence of E histolytical E dispar and Giardia lamblia. Source of water and lacking a refrigerator and electricity were associated with the presence of Ascaris lumbricoides. CONCLUSIONS: Measures should be taken to improve water quality, sewage disposal, and domestic hygiene. Furthermore, health programs should be established to promote breast-feeding, and education policies aimed at reinforcing the use of indigenous languages by physicians in the health services. 相似文献
996.
997.
Patel N Kay GN Sanchez J Ideker RE Smith WM 《Journal of cardiovascular electrophysiology》2003,14(7):698-704
INTRODUCTION: Ablation of muscular fascicles around the ostium of pulmonary veins (PVs) resulting in electrical isolation of the veins may prove to be an effective treatment for atrial fibrillation (AF). Correctly discriminating atrial and PV potentials is necessary to effectively isolate PVs from the left atrium in patients with paroxysmal AF. METHODS AND RESULTS: A training set of 151 electrode recordings obtained from 10 patients with AF was used to develop an algorithm to discriminate atrial and PV potentials. Bipolar electrograms were collected from a multielectrode basket catheter placed sequentially into each PV. Amplitude, slope, and normalized slopes of both bipolar and quadripolar electrograms (difference between adjacent bipoles) were entered into a binary logistic regression model. A receiver operating characteristic curve was used to define a threshold able to effectively discriminate atrial and PV potentials. The normalized slopes of both domains, bipolar and quadripolar, produced a logistic function that discriminated atrial and PV potentials against a threshold (0.38) with 97.8% sensitivity and 94.9% specificity. The algorithm then was evaluated on a test set of 214 electrode recordings from four patients who also had paroxysmal AF. These patient electrograms also were evaluated by two independent electrophysiologists. The algorithm and electrophysiologists matched identification of activation origin in 84% of electrograms. CONCLUSION: Atrial and PV potentials acquired from a multielectrode basket catheter can be discriminated using the normalized slopes of bipolar and quadripolar electrograms. These additional parameters need to be included by physicians determining the preferential ablation site within PVs. 相似文献
998.
Effects of acute hypoxia and lipopolysaccharide on nitric oxide synthase-2 expression in acute lung injury 总被引:5,自引:0,他引:5
Agorreta J Garayoa M Montuenga LM Zulueta JJ 《American journal of respiratory and critical care medicine》2003,168(3):287-296
The potential role of nitric oxide synthase-2 (NOS2) in acute lung injury (ALI) has gained increasing attention. This study evaluates the effects of hypoxia, an important feature of ALI, on NOS2 expression in a rat model of ALI caused by exposure to hypoxia and LPS. Exposure to hypoxia alone had no effect on the expression of NOS2 in rat lungs. LPS treatment resulted in a significant increase in NOS2 in the lungs, which was further enhanced by concomitant exposure to hypoxia. Immunohistochemical analysis and in situ hybridization showed no changes in the expression of NOS2 in lung resident cells under any conditions. The increase in NOS2 levels is mainly due to the influx of NOS2-expressing inflammatory cells. By morphologic analysis, these inflammatory cells were identified as neutrophils, lymphocytes, and monocytes. In vitro experiments of lung epithelial and endothelial cell lines showed no detectable expression of NOS2 with any of the treatments. In a macrophage cell line, LPS-induced NOS2 expression was not affected by the concomitant exposure to hypoxia. In conclusion, LPS increases NOS2 expression in rat lungs through the recruitment of NOS2-producing leukocytes. Simultaneous exposure to LPS and hypoxia results in a greater influx of inflammatory cells that further enhances NOS2 expression. 相似文献
999.
Arpa J Cruz-Martínez A Campos Y Gutiérrez-Molina M García-Rio F Pérez-Conde C Martín MA Rubio JC Del Hoyo P Arpa-Fernández A Arenas J 《Muscle & nerve》2003,28(6):690-695
We report 50 patients with various clinical phenotypes of mitochondrial disease studied over the past 10 years in a large urban area (Madrid Health Area 5). The clinical phenotypes showed a large variety of abnormalities in molecular biology and biochemistry. The prevalence of mitochondrial diseases was found to be 5.7 per 100,000 in the population over 14 years of age. Clinical and electrophysiological assessment reveal signs of neuropathy in 10 patients. Electromyographic findings consistent with myopathy were obtained in 37 cases. Six patients died of medical complications. Disease phenotype influenced survival to some degree (P < 0.01). Age of onset and gender were not associated with differences in survival. Mitochondrial disease is thus far more common than expected and a common cause of chronic morbidity. 相似文献
1000.