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   6496篇
  免费   339篇
  国内免费   20篇
耳鼻咽喉   102篇
儿科学   192篇
妇产科学   112篇
基础医学   825篇
口腔科学   570篇
临床医学   455篇
内科学   1273篇
皮肤病学   162篇
神经病学   408篇
特种医学   488篇
外科学   572篇
综合类   50篇
一般理论   2篇
预防医学   931篇
眼科学   57篇
药学   427篇
  1篇
中国医学   65篇
肿瘤学   163篇
  2023年   55篇
  2022年   114篇
  2021年   194篇
  2020年   120篇
  2019年   179篇
  2018年   202篇
  2017年   149篇
  2016年   150篇
  2015年   183篇
  2014年   296篇
  2013年   266篇
  2012年   408篇
  2011年   531篇
  2010年   259篇
  2009年   236篇
  2008年   307篇
  2007年   358篇
  2006年   322篇
  2005年   279篇
  2004年   242篇
  2003年   164篇
  2002年   160篇
  2001年   106篇
  2000年   88篇
  1999年   104篇
  1998年   105篇
  1997年   92篇
  1996年   94篇
  1995年   75篇
  1994年   50篇
  1993年   70篇
  1992年   48篇
  1991年   39篇
  1990年   48篇
  1989年   72篇
  1988年   66篇
  1987年   74篇
  1986年   69篇
  1985年   83篇
  1984年   42篇
  1983年   35篇
  1982年   33篇
  1981年   38篇
  1980年   42篇
  1979年   15篇
  1978年   27篇
  1977年   30篇
  1976年   28篇
  1975年   27篇
  1971年   10篇
排序方式: 共有6855条查询结果,搜索用时 0 毫秒
101.
OBJECTIVE: We previously reported that intrauterine undernutrition increased the oxidative stress by decreasing superoxide dismutase activity. In the present study, we tested whether NADPH oxidase, xanthine oxidase, cyclooxygenase or nitric oxide synthase are responsible for the increased O(2)(-) generation observed in rats submitted to intrauterine undernutrition. In addition, we investigated the effect of angiotensin II (ANG II) on O(2)(-) production via activation of NADPH oxidase. METHODS: Female pregnant Wistar rats were fed either normal or 50% of the normal intake diets, during the whole gestational period. At 16 weeks of age, the rats were used for the study of intravital fluorescence microscopy; microvascular reactivity, local ANG II concentration and AT(1), p22(phox) and gp91(phox) gene expression. In this study only the male offspring was used. RESULTS: Treatment of mesenteric arterioles with the xanthine oxidase inhibitor oxypurinol, the nitric oxide synthase inhibitor L-NAME or the cyclooxygenase inhibitor diclofenac did not significantly change superoxide production. Thus, these vascular sources of superoxide were not responsible for the increased superoxide concentration. In contrast, treatment with the NADPH oxidase inhibitor apocynin significantly decreased superoxide generation and improved vascular function. On the other hand, intrauterine undernutrition did not alter the gene expression for p22(phox) and gp91(phox). The fact that the local ANG II concentration was increased and the attenuation of oxidative stress by blocking AT(1) receptor with losartan, led us to suggest that ANG II induces O(2)(-) generation in intrauterine undernourished rats. CONCLUSION: Our study shows that NADPH oxidase inhibition attenuated superoxide anion generation and ameliorated vascular function in rats submitted to intrauterine undernutrition. Although it is not clear which mechanisms are responsible for the increase in NADPH oxidase activity, a role for ANG II-mediated superoxide production via activation of NADPH oxidase is suggested.  相似文献   
102.
AIMS: To assess plasma levels of vascular cellular adhesion molecule-1, a marker of endothelial dysfunction, in patients presenting with coronary syndromes submitted to coronary angiography. METHODS AND RESULTS: Plasma levels of soluble vascular cellular adhesion molecule-1 were measured by enzymatic immunoabsorbent assay in eight patients with angina-like chest pain and angiographically normal coronary arteries; in 14 patients with stable angina and in 18 patients with unstable angina, both with coronary lesions by angiography, and in 10 healthy volunteers. Levels of soluble vascular cellular adhesion molecule-1 were higher in unstable angina patients (1777+/-161 SE pg ml(-1)) compared to patients with stable angina (1178+/-206 SE pg ml(-1), P<0.05). Moreover, patients with angina-like chest pain and normal coronary arteries had significantly higher soluble vascular cellular adhesion molecule-1 levels (2307+/-295 SE pg ml(-1)) compared to stable angina patients (P<0.05), but similar levels compared to unstable angina patients. Patient groups had higher values of soluble vascular cellular adhesion molecule-1 compared to the control group (734+/-97 SE pg ml(-1)). CONCLUSIONS: Increased levels of soluble vascular cellular adhesion molecule-1 are associated with coronary artery disease in patients with anatomically established lesions. In patients free of flow-limiting lesions and angina-like chest pain, high levels of this marker may indicate endothelial dysfunction.  相似文献   
103.
Cranial CT scans of eleven immunocompetent children with central nervous system (CNS) infection due to Cryptococcus neoformans var. gattii were retrospectively reviewed. These children had an average age of 8.8 years and positive culture for C. n. var. gattii in cerebrospinal fluid. The most common signs and symptoms were headache, fever, nuchal rigidity, nausea and vomiting. No normal cranial CT was detected in any patient. Hypodense nodules were observed in all patients. The remaining scan abnormalities were as follows: nine had diffuse atrophy, six had hydrocephalus, and five had hydrocephalus coexistent with diffuse atrophy.  相似文献   
104.
Cassileth  PA; Suholet  D; Cooper  RA 《Blood》1981,58(2):237-243
The HL-60 leukemia cell line derived from a human acute promyelocytic leukemia is stimulated to differentiate into macrophages within 24-28 hr after exposure to the phorbol ester, 12-O-tetradecanoylphorbol-13- acetate (TPA). We studied early alterations (within 90 min of exposure to TPA) in phosphatidylcholine metabolism in HL-60 cells and found that phosphatidylcholine synthesis by methylation is phosphatidylethanolamine was inhibited in a dose-dependent fashion. In contrast, synthesis of phosphatidylcholine from endogenous choline was enhanced and correlated inversely with the degree of inhibition of the methylation pathway. Phorbol ester congeners of TPA caused similar alterations in phosphatidylcholine metabolism in direct relationship to their capacity to induce differentiation in HL-60 cells. Perturbation of phosphatidylcholine metabolism is an early membrane even in TPA- induced HL-60 cell differentiation.  相似文献   
105.
Sport Sciences for Health - Social isolation due to the coronavirus disease 2019 (COVID-19) pandemic has reduced physical activity levels in both men and women. The identification of barriers to...  相似文献   
106.
An increasing number of elderly people in renal support is expected in the coming years. The objective of this study was to report the clinical and socio-demographic data of end-stage renal disease (ESRD) adult patients undergoing regular dialysis treatment comparing elderly (≥65 years old) and non-elderly subjects using data from the Brazilian Dialysis Registry database. The regional distribution of the sample was Southeast (48.8%), South (33.7), Northeast (13.1%), Midwest (5.1%), and North (0.1%). A total of 18,030 patients were included in the analysis with elderly patients accounting for 29.5% of the sample. The elderly patients were predominantly male, white, retired, and literate. Elderly ESRD patients had a slightly higher frequency of undernourishment and a lower frequency of obesity than the non-elderly adults. A higher frequency of elderly patients were from the South and Southeast regions. The dialysis treatment of patients from both groups was predominantly funded by the public system, but the percent of non-public funding was higher for the elderly group. The most used initial access in the elderly was the central venous catheter and hemodialysis was the main modality at the beginning of treatment (93.2%), as well as during maintenance therapy (91.8%). Advanced age was associated with greater use of central venous catheter in the first dialysis session. The survival of the elderly on dialysis was lower than that of the non-elderly early in the course of dialysis and this difference increased over time. This is yet the largest national epidemiological study of elderly people on chronic dialysis.  相似文献   
107.
Odontology - Evaluate, through a randomized clinical trial, the efficacy of brushing associated with oral irrigation in maintaining implant and overdenture hygiene. Thirty-eight participants, who...  相似文献   
108.
BackgroundIn nurse and in medicine courses, the use of reflective portfolios as a pedagogical tool is becoming a common practice; in the last years, this practice has gradually migrated from paper-based to electronic-based portfolios. Current approaches for reflective e-portfolios, however, do not widely operate at outdoor sites, where data networks are limited or nonexistent. Considering that many of the activities related to nurse and medicine courses relate to professional practices conducted in such conditions, these network shortcomings restrict the adoption of e-portfolios.PurposeThe present study describes the requirements specification, design, implementation, and evaluation of the Ubiquitous Reflective E-Portfolio Architecture, a solution proposed to support the development of systems based on mobile and wired access for both online and offline operation.MethodsWe have implemented a prototype named Professional Practice Module to evaluate the Ubiquitous Reflective E-Portfolio Architecture; the module was based on requirements observed during the professional practice, the paper-based portfolio in use, and related learning meetings in the Medicine Course of a Brazilian University. The evaluation of the system was carried out with a learning group of 2nd year students of the medicine course, who answered to extensive evaluation questionnaires.ResultsThe prototype proved to be operational in the activities of the professional practice of the Medicine Course object of the study, including homework tasks, patient care, data sharing, and learning meetings. It also demonstrated to be versatile with respect to the availability of the computer network that, many times, was not accessible. Moreover, the students considered the module useful and easy to use, but pointed out difficulties about the keyboard and the display sizes of the netbook devices, and about their operational system. Lastly, most of the students declared preference for the electronic Professional Practice Module in internal and in group activities, and for the paper-based version while in patient attendance.ConclusionsThere is evidence that the environment where the professional practice takes place influences the usage of the e-portfolio. Mobile devices were able to support students in their professional practice; however, these devices present characteristics that must be judiciously selected, otherwise, they may limit the execution of important tasks. The main shortcoming identified during the evaluation tests was about the use of the module, and of the access device, during patient attendance. For this reason, we have envisioned a new version of the Professional Practice Module that shall follow a twofold requisite: by one side, it will include all the features of the module, to be used at the university or in the students’ homes; from the other side, it will include only the features that are essential for the practice of patient attendance.  相似文献   
109.
110.
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