全文获取类型
收费全文 | 6237篇 |
免费 | 466篇 |
国内免费 | 16篇 |
专业分类
耳鼻咽喉 | 34篇 |
儿科学 | 123篇 |
妇产科学 | 96篇 |
基础医学 | 1158篇 |
口腔科学 | 137篇 |
临床医学 | 554篇 |
内科学 | 1260篇 |
皮肤病学 | 200篇 |
神经病学 | 707篇 |
特种医学 | 230篇 |
外科学 | 513篇 |
综合类 | 12篇 |
一般理论 | 6篇 |
预防医学 | 595篇 |
眼科学 | 136篇 |
药学 | 383篇 |
中国医学 | 16篇 |
肿瘤学 | 559篇 |
出版年
2024年 | 9篇 |
2023年 | 65篇 |
2022年 | 108篇 |
2021年 | 190篇 |
2020年 | 125篇 |
2019年 | 167篇 |
2018年 | 171篇 |
2017年 | 184篇 |
2016年 | 200篇 |
2015年 | 236篇 |
2014年 | 263篇 |
2013年 | 348篇 |
2012年 | 533篇 |
2011年 | 537篇 |
2010年 | 302篇 |
2009年 | 288篇 |
2008年 | 413篇 |
2007年 | 442篇 |
2006年 | 380篇 |
2005年 | 388篇 |
2004年 | 316篇 |
2003年 | 308篇 |
2002年 | 250篇 |
2001年 | 58篇 |
2000年 | 48篇 |
1999年 | 51篇 |
1998年 | 44篇 |
1997年 | 43篇 |
1996年 | 22篇 |
1995年 | 23篇 |
1994年 | 29篇 |
1993年 | 18篇 |
1992年 | 28篇 |
1991年 | 17篇 |
1990年 | 12篇 |
1989年 | 14篇 |
1988年 | 5篇 |
1987年 | 13篇 |
1986年 | 9篇 |
1985年 | 5篇 |
1984年 | 5篇 |
1983年 | 7篇 |
1982年 | 8篇 |
1981年 | 7篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1978年 | 3篇 |
1977年 | 6篇 |
1973年 | 3篇 |
1968年 | 2篇 |
排序方式: 共有6719条查询结果,搜索用时 15 毫秒
31.
Interest in plant-based nutrition has steadily increased in the western world in the recent years. The number of people following a meat-reduced, flexitarian diet is growing continuously. However, little is known about the diet quality of flexitarians compared to vegans or omnivores. Therefore, in this cross-sectional study, the food intake of 94 participants aged between 25–45 years was recorded via a validated food frequency questionnaire and 28 self-designed questions about the consumption of plant-based alternatives. An adapted Healthy Eating Index, HEI-flex, was developed to evaluate the diet quality of flexitarians, vegans and omnivores. Higher score points (SP) of the HEI-flex are associated with higher compliance with the official diet recommendations (Vmax = 100 SP). Finally, flexitarians scored significantly more highly when compared to omnivores (54 ± 8 vs. 47 ± 9 SP; p = 0.008) but lower than vegans (54 ± 8 vs. 61 ± 10 SP; p = 0.010). The results showed that the HEI-flex is a useful tool for assessing and comparing the diet quality of flexitarians, vegans and omnivores. Despite the consumption of highly processed plant-based alternatives, reduction in meat and meat products seems to be accompanied by increased overall diet quality. 相似文献
32.
Anja C. M. de Bruin Mathis Funk Monique I. Spronken Alexander P. Gultyaev Ron A. M. Fouchier Mathilde Richard 《Viruses》2022,14(7)
Highly Pathogenic Avian Influenza Viruses (HPAIVs) arise from low pathogenic precursors following spillover from wild waterfowl into poultry populations. The main virulence determinant of HPAIVs is the presence of a multi-basic cleavage site (MBCS) in the hemagglutinin (HA) glycoprotein. The MBCS allows for HA cleavage and, consequently, activation by ubiquitous proteases, which results in systemic dissemination in terrestrial poultry. Since 1959, 51 independent MBCS acquisition events have been documented, virtually all in HA from the H5 and H7 subtypes. In the present article, data from natural LPAIV to HPAIV conversions and experimental in vitro and in vivo studies were reviewed in order to compile recent advances in understanding HA cleavage efficiency, protease usage, and MBCS acquisition mechanisms. Finally, recent hypotheses that might explain the unique predisposition of the H5 and H7 HA sequences to obtain an MBCS in nature are discussed. 相似文献
33.
Jelle Koopsen Catharina E. van Ewijk Roisin Bavalia Akke Cornelissen Sylvia M. Bruisten Floor de Gee Alvin X. Han Maarten de Jong Menno D. de Jong Marcel Jonges Norin Khawaja Fleur M.H.P.A. Koene Mariken van der Lubben Iris Mikulic Sjoerd P.H. Rebers Colin A. Russell Janke Schinkel Anja J.M. Schreijer Judith A. den Uil Matthijs R.A. Welkers Tjalling Leenstra 《Emerging infectious diseases》2022,28(5):1012
We report a severe acute respiratory syndrome coronavirus 2 superspreading event in the Netherlands after distancing rules were lifted in nightclubs, despite requiring a negative test or vaccination. This occurrence illustrates the potential for rapid dissemination of variants in largely unvaccinated populations under such conditions. We detected subsequent community transmission of this strain. 相似文献
34.
Anja Lazi Miodrag Koci Neboja Trajkovi Cristian Popa Leonardo Alexandre Peyr-Tartaruga Johnny Padulo 《Nutrients》2022,14(9)
Caffeine supplementation has become increasingly popular among athletes. The benefits of caffeine include delaying the negative effects of fatigue, maintaining a high level of physical and mental performance, and improving certain abilities necessary for sport success. Given the complex nature of basketball, caffeine could be a legal, ergogenic stimulant substance, which will positively affect overall basketball performance. The purpose of this systematic review was to summarize evidence for the effect of acute caffeine ingestion on variables related to the basketball performance. Web of Science, PubMed, Scopus and ProQuest, MEDLINE, and ERIC databases were searched up to February 2021. Studies that measured the acute effect of caffeine on basketball performance were included and analyzed. Eight studies published between 2000 and 2021 were included in the analysis. Pre-exercise caffeine intake increased vertical jump height, running time at 10 and 20 m without the ball, overall basketball performance (number of body impacts, number of free throws, rebounds, and assists) during simulated games, and reduced the time required to perform a basketball-specific agility test. Equivocal results between caffeine and placebo groups were found for aerobic capacity, free throw and three-point accuracy, and dribbling speed. Pre-exercise caffeine ingestion did not affect RPE, but insomnia and urinary excretion were increased. The pre-exercise ingestion of 3 and 6 mg/kg caffeine was found to be effective in increasing several physical performance variables in basketball players during sport-specific testing and simulated matches. However, considering the intermittent nature and complexity of basketball, and individual differences between players, future studies are needed. 相似文献
35.
36.
Ilkka Immonen Anja Siimes Ulf-Håkan Stenman Jorma Kärkkäinen Frej Fyhrquist 《Scandinavian journal of clinical and laboratory investigation》2013,73(1):61-65
Relationship between concentrations of serum oestrogens, plasma renin substrate and plasma renin activity were studied in six women throughout pregnancy. There was a significant positive correlation between serum oestradiol-17β and plasma renin substrate concentrations (r=0.60). Serum oestriol concentrations also correlated significantly with plasma renin substrate concentrations (r=0.68). Correlation coefficients calculated separately for each subject throughout pregnancy were higher than those for the whole group. Also, there was much individual variation in dose-response of serum oestrogens to plasma renin substrate concentrations. There was no significant correlation between serum oestrogens and plasma renin activity.Our results support the view that oestrogens cause the increase in plasma renin substrate concentration during pregnancy, and emphasize the individual variation in response of renin substrate concentration to serum level of oestrogens. 相似文献
37.
38.
Summary To clarify the heterogeneity of Type 1 (insulin-dependent) diabetes mellitus, differences between patients with different HLA risk antigens were investigated with regard to sex, age at diagnosis, season of year and calendar year at diagnosis of the disease. The study consisted of 293 HLA-typed patients from the Department of Paediatrics, University of Oulu, Oulu, Finland. HLA-Dw2 was extremely rare among diabetic patients, whereas Dw3 and Dw4 were associated with increased risk in this as in other series. Male patients more often had the HLA-A1 antigen than females. On comparison of the Dw3 positive patients, boys more frequently had the combination A1,B8 than girls. A1,B8-positive patients were more often diagnosed during the warm months, in the late summer and autumn. Patients with both Dw3 and Dw4 were younger at diagnosis when compared with the rest of the patients. The results support the concept of heterogeneity in the pathogenesis of Type 1 diabetes associated with HLA-linked genetic determinants. 相似文献
39.
Probiotics partly reverse increased bacterial translocation after simultaneous liver resection and colonic anastomosis in rats 总被引:11,自引:0,他引:11
Seehofer D Rayes N Schiller R Stockmann M Müller AR Schirmeier A Schaeper F Tullius SG Bengmark S Neuhaus P 《The Journal of surgical research》2004,117(2):262-271
BACKGROUND: Bacterial translocation is one important cause of nosocomial infections following major abdominal surgery. Oral administration of probiotics has been proposed to diminish bacterial translocation. MATERIAL AND METHODS: In total 68 rats were divided into seven groups: five of the groups received standard rat chow and were subjected to either sham-operation, 70% liver resection, colonic anastomosis, or a combination of 30 or 70% liver resection with synchronous colonic anastomosis, respectively. In two additional groups with synchronous operation, a combination of four different lactic acid bacteria and four fibers was administered two times daily pre- and postoperatively. Bacterial concentrations in cecum, mesenteric lymph nodes, liver, and spleen were analyzed and blood cultures were taken 48 h after operation. Furthermore, the following parameters were assessed: histological changes in the intestine, intestinal paracellular permeability (Ussing chamber), bursting pressure of the colonic anastomosis, and mitosis rate of the remnant liver. RESULTS: Bacterial translocation was observed in all rats, except in the sham group. Following liver resection, the highest bacterial concentrations were seen in liver and spleen, following colon anastomosis in the mesenteric lymph nodes. Bacterial translocation was increased in the animals with combined operation, in parallel to the extent of liver resection. In rats with colon anastomosis, bacterial concentration in the cecum was also higher than in the sham group. Application of probiotics significantly decreased bacterial concentration in the lymph nodes. In addition, animals with a high cecal concentration of lactobacilli had less translocation than the others. No histological changes were observed in the intestine. Paracellular permeability for ions, but not for the larger molecule lactulose, was increased in the colon in all groups with colon anastomosis. The bursting pressure of the colon anastomosis was not significantly different between the groups. Seventy percent liver resection led to a high rate of hepatocyte mitosis, whereas combination with colon anastomosis impaired the regeneration process. CONCLUSION: Synchronous liver resection and colon anastomosis led to increased bacterial translocation compared to the single operations in the rat model. It is possible to diminish this process by oral administration of probiotics. Bacterial overgrowth in the cecum and impaired hepatic regeneration, but not histological changes or alterations of paracellular permeability, are potential pathogenic mechanisms for translocation in this setting. 相似文献
40.
Dagmara Borzych-Duzalka Yelda Bilginer Il Soo Ha Mustafa Bak Lesley Rees Francisco Cano Reyner Loza Munarriz Annabelle Chua Silvia Pesle Sevinc Emre Agnieszka Urzykowska Lily Quiroz Javier Darío Ruscasso Colin White Lars Pape Virginia Ramela Nikoleta Printza Andrea Vogel Dafina Kuzmanovska Eva Simkova Dirk E. Müller-Wiefel Anja Sander Bradley A. Warady Franz Schaefer for the International Pediatric Peritoneal Dialysis Network Registry 《Journal of the American Society of Nephrology : JASN》2013,24(4):665-676
Little information exists regarding the efficacy, modifiers, and outcomes of anemia management in children with CKD or ESRD. We assessed practices, effectors, and outcomes of anemia management in 1394 pediatric patients undergoing peritoneal dialysis (PD) who were prospectively followed in 30 countries. We noted that 25% of patients had hemoglobin levels below target (<10 g/dl or <9.5 g/dl in children older or younger than 2 years, respectively), with significant regional variation; levels were highest in North America and Europe and lowest in Asia and Turkey. Low hemoglobin levels were associated with low urine output, low serum albumin, high parathyroid hormone, high ferritin, and the use of bioincompatible PD fluid. Erythropoiesis-stimulating agents (ESAs) were prescribed to 92% of patients, and neither the type of ESA nor the dosing interval appeared to affect efficacy. The weekly ESA dose inversely correlated with age when scaled to weight but did not correlate with age when normalized to body surface area. ESA sensitivity was positively associated with residual diuresis and serum albumin and inversely associated with serum parathyroid hormone and ferritin. The prevalence of hypertension and left ventricular hypertrophy increased with the degree of anemia. Patient survival was positively associated with achieved hemoglobin and serum albumin and was inversely associated with ESA dose. In conclusion, control of anemia in children receiving long-term PD varies by region. ESA requirements are independent of age when dose is scaled to body surface area, and ESA resistance is associated with inflammation, fluid retention, and hyperparathyroidism. Anemia and high ESA dose requirements independently predict mortality.Almost three decades after the advent of recombinant erythropoietin, the management of renal anemia has become a recent focus of attention and changing paradigms. Whereas correction of hemoglobin (Hb) levels to near-normal has previously been recommended on the basis of association studies linking more severe anemia to morbidity and mortality with dialysis,1–3 interventional clinical trials consistently demonstrate that near-normalization of Hb increases the risk of vascular events and mortality in adults receiving maintenance hemodialysis and in those with CKD who are not undergoing dialysis.4–6 This has prompted ongoing reevaluation and revisions of treatment targets in patients exposed to erythropoiesis-stimulating agents (ESAs).7The appropriateness of applying treatment recommendations established in adult hemodialysis populations at high cardiovascular risk and adults with CKD to children undergoing dialysis is questionable because cardiovascular events are far less common in children with CKD. Furthermore, two thirds of children requiring dialysis initially opt for peritoneal dialysis (PD), and there are no systematic studies in the adult PD population to inform the optimal Hb target range in these patients. The risk profile of patients receiving PD may differ from that of the hemodialysis setting because of the absence of dialysis-induced intermittent hemoconcentration and lack of contact activation of the complement and coagulation systems.Further aspects to consider in pediatric anemia management are the greater physical activity of children and the need for optimal cognitive functioning at school.8,9 The significant physiologic variation of the normal Hb range with age10 and the relative ESA sensitivity that reportedly increases with age during early childhood are also noteworthy.11The registry of the International Pediatric Peritoneal Dialysis Network (IPPN) prospectively collects detailed clinical, biochemical, dialysis, and medication-related information (including ESA types and doses and modalities of iron supplementation) from a substantial number of children undergoing long-term PD around the world. In-depth analysis of this unique database has allowed us to (1) gain insight into the demographic characteristics of renal anemia and its treatment in the pediatric PD population worldwide, (2) explore the relationship between ESA dose requirements and body dimensions, (3) identify factors contributing to ESA resistance in children, and (4) associate anemia control with patient outcomes. 相似文献