全文获取类型
收费全文 | 28334篇 |
免费 | 3080篇 |
国内免费 | 1903篇 |
专业分类
耳鼻咽喉 | 310篇 |
儿科学 | 530篇 |
妇产科学 | 556篇 |
基础医学 | 2678篇 |
口腔科学 | 433篇 |
临床医学 | 3286篇 |
内科学 | 3789篇 |
皮肤病学 | 327篇 |
神经病学 | 1367篇 |
特种医学 | 1008篇 |
外国民族医学 | 11篇 |
外科学 | 3410篇 |
综合类 | 5387篇 |
现状与发展 | 6篇 |
一般理论 | 2篇 |
预防医学 | 2425篇 |
眼科学 | 485篇 |
药学 | 3019篇 |
33篇 | |
中国医学 | 1990篇 |
肿瘤学 | 2265篇 |
出版年
2024年 | 143篇 |
2023年 | 553篇 |
2022年 | 1316篇 |
2021年 | 1725篇 |
2020年 | 1312篇 |
2019年 | 1053篇 |
2018年 | 1066篇 |
2017年 | 1090篇 |
2016年 | 964篇 |
2015年 | 1500篇 |
2014年 | 1765篇 |
2013年 | 1921篇 |
2012年 | 2521篇 |
2011年 | 2536篇 |
2010年 | 1822篇 |
2009年 | 1432篇 |
2008年 | 1595篇 |
2007年 | 1450篇 |
2006年 | 1299篇 |
2005年 | 1141篇 |
2004年 | 786篇 |
2003年 | 772篇 |
2002年 | 671篇 |
2001年 | 522篇 |
2000年 | 421篇 |
1999年 | 329篇 |
1998年 | 151篇 |
1997年 | 176篇 |
1996年 | 132篇 |
1995年 | 113篇 |
1994年 | 119篇 |
1993年 | 66篇 |
1992年 | 111篇 |
1991年 | 106篇 |
1990年 | 93篇 |
1989年 | 79篇 |
1988年 | 84篇 |
1987年 | 67篇 |
1986年 | 55篇 |
1985年 | 40篇 |
1984年 | 26篇 |
1983年 | 23篇 |
1982年 | 14篇 |
1981年 | 12篇 |
1980年 | 19篇 |
1979年 | 16篇 |
1978年 | 14篇 |
1977年 | 11篇 |
1976年 | 12篇 |
1970年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
42.
43.
【目的】研制一个计算机辅助的心血管信号检测和处理系统。【方法】本系统的硬件设计采用奔腾 Ⅱ / 2 33多媒体微机系统 ,多路模 /数转换器和心电电极、心音传感器、脉搏波传感器及由运算放大器等构成相关的放大器及滤波器。本系统采用可视化编程环境构建系统结构和功能模块设计的方法 ,基于多媒体技术和小波变换原理 ,在 32位Windows平台下 ,利用可视化编程语言VisualC 6 0和多媒体著作工具Authorware等进行系统的软件设计。【结果】本系统能完成心电、心音、脉搏波信号检测和处理 ,并将结果以图、文、声并茂的形式显示、打印或播放 ,还具有病案管理和心音听诊多媒体计算机辅助教学功能。【结论】它是一个新型的多功能心血管信号检测和处理系统。 相似文献
44.
Journal of Digital Imaging - Although medical imaging is frequently used to diagnose diseases, in complex diagnostic situations, specialists typically need to look at different modalities of image... 相似文献
45.
Ma S Li X Fang Q Ross MG Chao CR 《Brain research. Developmental brain research》1999,118(1-2):119-127
Transition from fetal to newborn life is accompanied by a marked rise in circulating norepinephrine (NE) concentrations though arterial blood pressure does not substantively change. Nitric oxide (NO) plays an important role in the central regulation of sympathetic tone in the nucleus tractus solitarius (NTS) and neuronal NO synthase (nNOS) expression is functionally regulated in the brain. The purpose of these studies was to determine the influence of transition at birth on nNOS expression in the brainstem nuclei, particularly in the NTS, associated with changes in arterial pressure and plasma NE concentration. Experiments were performed using time-dated gestational ewes with twin fetuses. Arterial blood pressure was recorded and arterial blood NE concentrations were measured in the term fetus (gestational 147-148 days) and newborn lambs (4 h of postnatal age). The fetal and newborn animals were then perfused with 4% paraformaldehyde. Sections of the medulla were examined by using both immunolabeling with a polyclonal antibody directed against nNOS and nicotinamide adenine dinucleotide phosphate diaphorase (NADPHd) histochemistry, a marker for expression of nNOS. Micrographs were quantified using a microscope with reticule grid to measure the number of positive cells containing color staining in the brainstem nuclei. Plasma NE concentration in the newborn was more than two-fold greater compared to fetal values but mean arterial blood pressure was similar between fetus and newborn. The nNOS positive cells and NADPHd positive cells were significantly increased in the medial NTS (mNTS) of the newborn compared to fetus. nNOS immunoreactivity and NADPHd reactivity tended to increase in the rostral ventral medulla (RVM) in newborn, but were not altered in other brainstem nuclei during the transition from fetal to newborn life. The results suggest that nNOS expression in the mNTS is predominately enhanced at 4 h of neonatal age vs. the term fetus. We conclude that elevated circulating NE is associated with up-regulation of nNOS in the mNTS which may serve a protective role in central regulation of neonatal arterial blood pressure. 相似文献
46.
报道58例非心脏手术的围手术期心脏起搏临床应用,重点讨论围手术期心脏起搏的方法与适应症。认为经静脉右室起搏疗效恒定可靠,适应症范围广。对伴有缓慢型或快速型心律失常的心脏病或潜在心脏病患者,围手术期心脏起搏适应症可适当放宽,以确保麻醉手术顺利进行 相似文献
47.
Neuroprotective mechanism of glial cell line-derived neurotrophic factor on dopamine neurons: role of antioxidation. 总被引:5,自引:0,他引:5
Recombinant human GDNF was infused into the rat striatum either acutely or subchronically. Its effects and its interactions with MPP+ on antioxidant enzyme activities were examined. Results indicated that acute GDNF infusion significantly increased glutathione peroxidase, superoxide dismutase and catalase activities. Subchronic GDNF treatment decreased the DA level and enhanced DA turnover. Pre-treatment with GDNF markedly protected DA neurons against MPP+-induced toxicity. These results suggest that GDNF protects DA neurons through its activation of the antioxidant enzyme systems. 相似文献
48.
Chao CC 《Environmental toxicology and pharmacology》1996,1(3):199-205
We have previously reported a cisplatin-resistant HeLa variant cell line (HeLa/CPR) which exhibited an enhancement in repairing cisplatin-DNA adducts (Chao, 1994, Mol. Pharmacol. 45, 1137-1144). In this study, using this cell line, we investigated the modification, by arsenite, of cisplatin-induced cytotoxicity and DNA repair in the resistant cell line. By a sublethal dose of arsenite, cytotoxicity of the resistant cells was enhanced by 2.5-fold, compared to 1.62-fold in the parental cells. Using enzyme-linked immunosorbent assay (ELISA) and a monoclonal antibody specific for cisplatin-DNA adducts, we found that the resistant cells showed a 5.15-fold decrease in the adduct formation compared to the parental cells. However, in the presence of arsenite, the resistant cells showed only a 1.47-fold decrease in the adduct formation, indicating a more than 3-fold modification. Using host cell reactivation of transfected plasmid DNA carrying cisplatin damage (an indirect detection of DNA repair), arsenite also revealed a ~2-fold modification of adduct formation in the resistant cells. In addition, the time-dependent potentiation of cytotoxicity by arsenite in both cell lines was parallel to the increase of adduct formation. These results indicate that arsenite is an effective modifier of cisplatin-induced resistance and enhanced DNA repair in HeLa/CPR cells. The results are consistent with the notion that the cisplatin-resistant phenotype in HeLa cells is mainly mediated by enhancement of DNA repair. 相似文献
49.
Objective To investigate the activation of apoptotic genes of the brain with hypoxia- ischemia (HI) in newborn SD rats, and MRI changes and memory and learning ability in adulthood. Methods HI was induced by right carotid artery ligation followed by 2.5 h of hypoxia (6% O2) on 3-day-old SD rats (n=36). Control pups were sham-operated (n = 27). Right brain hemisphere was collected at 12 h and 7 d after HI and subjected to an apoptosis Oligo GEArrayR. MRI and Morris water maze test were performed on both groups at 42 and 44 days old, respectively. Results Comparing to 12 h after HI, up-regulated apoptotic genes included TNF, Caspase and pro-apoptotit genes of Bcl2 families, whereas the anti-apoptotic genes of Bcl2 family were down-regulated at 7 d after HI. The MRI assessment of the rats in HI group demonstrated that the area of the right cerebra l cortex was significantly smaller than the left side and control [periventricular layer: (23.5±3.6) mm2 vs (33.0±4.3) mm2, (34.5±3.9) mm2; hippocampus layer: (18.9±4.4) mm2 vs (29.1±5.0) mm2,(30.8±4.5) mm2, both P<0.01]. During the navigation trial, the HI rats demonstrated longer escape latency (4th day: (52.7±35.9) vs (17.8±8. 9) s, P<0.01). HI rats passed the platform less times than the control ones (T= 292.5, P<0.05) in space probe trial. Conclusions The activation of apoptotic genes induced by HI brain injury remains until 7 days later, involving intrinsic and extrinsic apoptotic pathway. The apoptosis of neural cells may lead to poor development of the cortex and impair the memory and learning ability in the adult rats after neonatal hypoxia- ischemia injury. 相似文献
50.
CT-based delineation of lymph node levels and related CTVs in the node-negative neck: DAHANCA, EORTC, GORTEC, NCIC,RTOG consensus guidelines. 总被引:25,自引:0,他引:25
Vincent Grégoire Peter Levendag Kian K Ang Jacques Bernier Marijel Braaksma Volker Budach Cliff Chao Emmanuel Coche Jay S Cooper Guy Cosnard Avraham Eisbruch Samy El-Sayed Bahman Emami Cai Grau Marc Hamoir Nancy Lee Philippe Maingon Karin Muller Hervé Reychler 《Radiotherapy and oncology》2003,69(3):227-236
BACKGROUND AND PURPOSE: The appropriate application of 3-D CRT and IMRT for HNSCC requires a standardization of the procedures for the delineation of the target volumes. Over the past few years, two proposals--the so-called Brussels guidelines from Grégoire et al., and the so-called Rotterdam guidelines from Nowak et al.--emerged from the literature for the delineation of the neck node levels. Detailed examination of these proposals however revealed some important discrepancies. MATERIALS AND METHODS: Within this framework, the Brussels and Rotterdam groups decided to review their guidelines and derive a common set of recommendations for delineation of neck node levels. This proposal was then discussed with representatives of major cooperative groups in Europe (DAHANCA, EORTC, GORTEC) and in North America (NCIC, RTOG), which, after some additional refinements, have endorsed them. The objective of the present article is to present the consensus guidelines for the delineation of the node levels in the node-negative neck. RESULTS AND CONCLUSIONS: First a short discussion of the discrepancies between the previous Brussels and the Rotterdam guidelines is presented. The general philosophy of the consensus guidelines and the methodology used to resolve the various discrepancies are then described. The consensus proposal is then presented and representative CTVs that are consistent with these guidelines are illustrated on CT sections. Last, the limitations of the consensus guidelines are discussed and some concerns about the direct applications of these guidelines to the node-positive neck and the post-operative neck are described. 相似文献