全文获取类型
收费全文 | 44828篇 |
免费 | 3514篇 |
国内免费 | 110篇 |
专业分类
耳鼻咽喉 | 557篇 |
儿科学 | 1106篇 |
妇产科学 | 845篇 |
基础医学 | 5599篇 |
口腔科学 | 644篇 |
临床医学 | 4942篇 |
内科学 | 9482篇 |
皮肤病学 | 580篇 |
神经病学 | 4280篇 |
特种医学 | 1759篇 |
外科学 | 6883篇 |
综合类 | 587篇 |
一般理论 | 51篇 |
预防医学 | 4211篇 |
眼科学 | 677篇 |
药学 | 3208篇 |
中国医学 | 30篇 |
肿瘤学 | 3011篇 |
出版年
2023年 | 288篇 |
2022年 | 542篇 |
2021年 | 1204篇 |
2020年 | 741篇 |
2019年 | 1117篇 |
2018年 | 1337篇 |
2017年 | 960篇 |
2016年 | 984篇 |
2015年 | 1174篇 |
2014年 | 1739篇 |
2013年 | 2300篇 |
2012年 | 3304篇 |
2011年 | 3364篇 |
2010年 | 1787篇 |
2009年 | 1662篇 |
2008年 | 2927篇 |
2007年 | 2825篇 |
2006年 | 2609篇 |
2005年 | 2636篇 |
2004年 | 2428篇 |
2003年 | 2169篇 |
2002年 | 1984篇 |
2001年 | 493篇 |
2000年 | 532篇 |
1999年 | 521篇 |
1998年 | 443篇 |
1997年 | 359篇 |
1996年 | 366篇 |
1995年 | 262篇 |
1994年 | 253篇 |
1993年 | 229篇 |
1992年 | 335篇 |
1991年 | 345篇 |
1990年 | 309篇 |
1989年 | 293篇 |
1988年 | 257篇 |
1987年 | 262篇 |
1986年 | 269篇 |
1985年 | 260篇 |
1984年 | 216篇 |
1983年 | 204篇 |
1982年 | 172篇 |
1981年 | 132篇 |
1980年 | 123篇 |
1979年 | 190篇 |
1978年 | 122篇 |
1977年 | 105篇 |
1975年 | 107篇 |
1974年 | 109篇 |
1973年 | 108篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Changes in the cause of death among HIV positive subjects across Europe: results from the EuroSIDA study 总被引:12,自引:0,他引:12
Mocroft A Brettle R Kirk O Blaxhult A Parkin JM Antunes F Francioli P D'Arminio Monforte A Fox Z Lundgren JD;EuroSIDA study group 《AIDS (London, England)》2002,16(12):1663-1671
OBJECTIVES: The causes of death among HIV-positive patients may have changed since the introduction of highly active antiretroviral therapy (HAART). We investigated these changes, patients who died without an AIDS diagnosis and factors relating to pre-AIDS deaths. METHODS: Analyses of 1826 deaths among EuroSIDA patients, an observational study of 8556 patients. Incidence rates of pre-AIDS deaths were compared to overall rates. Factors relating to pre-AIDS deaths were identified using Cox regression. RESULTS: Death rates declined from 15.6 to 2.7 per 100 person-years of follow-up (PYFU) between 1994 and 2001. Pre-AIDS incidence declined from 2.4 to 1.1 per 100 PYFU. The ratio of overall to pre-AIDS deaths peaked in 1996 at 8.4 and dropped to < 3 after 1998. The adjusted odds of dying following one AIDS defining event (ADE) increased yearly (odds ratio, 1.53; P < 0.001), conversely the odds of dying following three or more ADE decreased yearly (odds ratio, 0.79; P < 0.001). The proportion of deaths that followed an HIV-related disease decreased by 23% annually; in contrast there was a 32% yearly increase in the proportion of deaths due to known causes other than HIV-related or suicides. Injecting drug users (IDU) were significantly more likely to die before an ADE than homosexuals (relative hazard, 2.97; P < 0.0001) and patients from northern/eastern Europe (relative hazard, 2.01; P < 0.0001) were more likely to die pre-AIDS than southern patients. CONCLUSIONS: The proportion of pre-AIDS deaths increased from 1994 to 2001; however, the incidence of pre-AIDS deaths and deaths overall declined. IDU and subjects from northern/eastern Europe had an increased risk of pre-AIDS death. HIV-positive patients live longer therefore it is essential to continue to monitor all causes of mortality to identify changes. 相似文献
992.
Discovery of lipid peroxidation products formed in vivo with a substituted tetrahydrofuran ring (isofurans) that are favored by increased oxygen tension 下载免费PDF全文
Fessel JP Porter NA Moore KP Sheller JR Roberts LJ 《Proceedings of the National Academy of Sciences of the United States of America》2002,99(26):16713-16718
Free radicals have been implicated in the pathogenesis of an increasing number of diseases. Lipids, which undergo peroxidation, are major targets of free radical attack. We report the discovery of a pathway of lipid peroxidation that forms a series of isomers in vivo that are characterized by a substituted tetrahydrofuran ring structure, termed isofurans (IsoFs). We have proposed two distinct pathways by which IsoFs can be formed based on 18O2 and H2 18O labeling studies. Measurement of F2-isoprostanes (IsoPs), prostaglandin F2-like compounds formed nonenzymatically as products of lipid peroxidation, is considered one of the most reliable approaches for assessing oxidative stress status in vivo. However, one limitation with this approach is that the formation of IsoPs becomes limited at high oxygen tension. In contrast, the formation of IsoFs becomes increasingly favored as oxygen tension increases. IsoFs are present at readily detectable levels in normal fluids and tissues, and levels increase dramatically in CCl4-treated rats, an animal model of oxidant injury. The ratio of IsoFs to IsoPs in major organs varies according to normal steady-state tissue oxygenation. In addition, IsoFs show a marked increase early in the course of hyperoxia-induced lung injury, whereas IsoPs do not significantly increase. We propose that combined measurement of IsoFs and IsoPs should provide a more reliable index of oxidant stress severity than quantification of either alone because of the opposing modulation of the two pathways by oxygen tension, which can vary widely in different organs and disease states. 相似文献
993.
In patients with ventricular or atrial septal defect, the ventricle which is chronically volume overloaded might not appropriately respond to increased demand for an augmentation in output and thereby might limit total cardiac function. In this study we simultaneously measured right and left ventricular response to exercise in 10 normal individuals, 10 patients with ventricular septal defect (VSD), and 10 patients with atrial septal defect (ASD). The normal subjects increased both right and left ventricular ejection fraction, end-diastolic volume, and stroke volume to achieve a higher cardiac output during exercise. Patients with VSD failed to increase right ventricular ejection fraction, but increased right ventricular end-diastolic volume and stroke volume. Left ventricular end-diastolic volume did not increase in these patients but ejection fraction, stroke volume, and forward left ventricular output achieved during exercise were comparable to the response observed in healthy subjects. In the patients with ASD, no rest-to-exercise change occurred in either right ventricular ejection fraction, end-diastolic volume, or stroke volume. In addition, left ventricular end-diastolic volume failed to increase, and despite an increase in ejection fraction, left ventricular stroke volume remained unchanged from rest to exercise. Therefore, cardiac output was augmented only by the heart rate increase in these patients. Right ventricular function appeared to be the major determinant of total cardiac output during exercise in patients with cardiac septal defects and left-to-right shunt. 相似文献
994.
995.
Bacterial infection as a complication of liver transplantation: epidemiology and risk factors 总被引:14,自引:0,他引:14
D L George P M Arnow A S Fox A L Baker J R Thistlethwaite J C Emond P F Whitington C E Broelsch 《Reviews of infectious diseases》1991,13(3):387-396
A retrospective survey was undertaken to characterize the epidemiology of bacterial infection in 79 patients who underwent 103 operations for orthotopic liver transplantation. Fifty-four patients (68%) developed 115 bacterial infections (1.46 episodes per patient), and seven patients died as a result of these infections. Fifty-three percent of bacterial infections occurred within 2 weeks after transplantation and were designated as early infections. The most common sites of infection were the abdomen (35 cases), the bloodstream (31 cases), and the surgical wound (19 cases). Aerobic enteric gram-negative bacilli were the predominant pathogens, and other pathogenic organisms were enterococci, staphylococci, and Pseudomonas bacteria. Logistic regression analysis identified prolonged duration of surgery (greater than or equal to 8 hours) and an elevated bilirubin level (greater than or equal to 12 mg/dL) as risk factors for early bacterial infection at any site; risk factors for abdominal or wound infection were prolonged duration of surgery, increased operative transfusion requirement (greater than or equal to 2 blood volumes), and prior hepatobiliary surgery. Awareness of the sites, pathogens, and time of onset of bacterial infection provides a basis for improved prophylaxis and empiric therapy. 相似文献
996.
HMGB1 in sepsis 总被引:7,自引:0,他引:7
997.
The role of fondaparinux as an adjunct to thrombolytic therapy in acute myocardial infarction: a subgroup analysis of the OASIS-6 trial. 总被引:3,自引:0,他引:3
Ron J G Peters Campbell Joyner Jean-Pierre Bassand Rizwan Afzal Susan Chrolavicius Shamir R Mehta Jonas Oldgren Lars Wallentin Andrzej Budaj Keith A Fox Salim Yusuf 《European heart journal》2008,29(3):324-331
AIMS: No antithrombotic therapy has been shown to reduce mortality when used with thrombolytics in acute myocardial infarction (AMI). In the OASIS-6 trial, fondaparinux significantly reduced mortality and reinfarction without increasing bleeding in 12 092 patients with acute ST elevation MI. METHODS AND RESULTS: We report the results of a subgroup analysis in the 5436 patients (45%) receiving thrombolytics. According to local practice, 4415 patients did not have an indication for unfractionated heparin (stratum 1) and 1021 did (stratum 2). Fondaparinux reduced the primary study outcome of death or MI at 30 days [Hazard ratio (HR) 0.79, 95% confidence interval (CI) 0.68-0.92] with consistent reductions in both mortality (HR and CI) and reinfarction (HR and CI). There was a non-significantly lower rate of stroke (HR 0.77, CI 0.48-1.25). The risk of severe bleeding was significantly reduced (HR 0.62, CI 0.40-0.94), and thus the balance of benefit and risk (death, MI and severe haemorrhage) was clearly reduced by fondaparinux (HR 0.77, 95% CI 0.67-0.90). Results were consistent in the two strata, by the different types of thrombolytics and across various time intervals from symptom onset to treatment. CONCLUSION: In STEMI patients treated with thrombolytic agents (predominantly streptokinase), fondaparinux significantly reduced the risk of death, re-MI and severe bleeds. 相似文献
998.
999.
1000.
Blumer JB Lord K Saunders TL Pacchioni A Black C Lazartigues E Varner KJ Gettys TW Lanier SM 《Endocrinology》2008,149(8):3842-3849
Activator of G protein signaling (AGS)-3 plays functional roles in cell division, synaptic plasticity, addictive behavior, and neuronal development. As part of a broad effort to define the extent of functional diversity of AGS3-regulated-events in vivo, we generated AGS3 null mice. Surprisingly, AGS3 null adult mice exhibited unexpected alterations in cardiovascular and metabolic functions without any obvious changes in motor skills, basic behavioral traits, and brain morphology. AGS3 null mice exhibited a lean phenotype, reduced fat mass, and increased nocturnal energy expenditure. AGS3 null mice also exhibited altered blood pressure control mechanisms. These studies expand the functional repertoire for AGS3 and other G protein regulatory proteins providing unexpected mechanisms by which G protein systems may be targeted to influence obesity and cardiovascular function. 相似文献