全文获取类型
收费全文 | 6316篇 |
免费 | 451篇 |
国内免费 | 26篇 |
专业分类
耳鼻咽喉 | 60篇 |
儿科学 | 252篇 |
妇产科学 | 175篇 |
基础医学 | 1108篇 |
口腔科学 | 182篇 |
临床医学 | 587篇 |
内科学 | 1320篇 |
皮肤病学 | 123篇 |
神经病学 | 608篇 |
特种医学 | 116篇 |
外科学 | 472篇 |
综合类 | 33篇 |
一般理论 | 9篇 |
预防医学 | 670篇 |
眼科学 | 119篇 |
药学 | 441篇 |
中国医学 | 15篇 |
肿瘤学 | 503篇 |
出版年
2024年 | 9篇 |
2023年 | 80篇 |
2022年 | 135篇 |
2021年 | 292篇 |
2020年 | 159篇 |
2019年 | 248篇 |
2018年 | 262篇 |
2017年 | 166篇 |
2016年 | 196篇 |
2015年 | 263篇 |
2014年 | 287篇 |
2013年 | 356篇 |
2012年 | 590篇 |
2011年 | 543篇 |
2010年 | 314篇 |
2009年 | 226篇 |
2008年 | 441篇 |
2007年 | 349篇 |
2006年 | 377篇 |
2005年 | 357篇 |
2004年 | 282篇 |
2003年 | 269篇 |
2002年 | 204篇 |
2001年 | 29篇 |
2000年 | 20篇 |
1999年 | 25篇 |
1998年 | 37篇 |
1997年 | 14篇 |
1996年 | 30篇 |
1995年 | 19篇 |
1994年 | 14篇 |
1993年 | 14篇 |
1992年 | 6篇 |
1991年 | 9篇 |
1988年 | 5篇 |
1987年 | 7篇 |
1984年 | 11篇 |
1983年 | 5篇 |
1982年 | 10篇 |
1981年 | 7篇 |
1980年 | 9篇 |
1978年 | 8篇 |
1977年 | 6篇 |
1976年 | 7篇 |
1975年 | 5篇 |
1973年 | 7篇 |
1961年 | 5篇 |
1932年 | 4篇 |
1931年 | 4篇 |
1925年 | 4篇 |
排序方式: 共有6793条查询结果,搜索用时 15 毫秒
101.
Wernicke D Schulze-Westhoff C Bräuer R Petrow P Zacher J Gay S Gromnica-Ihle E 《Arthritis and rheumatism》2002,46(1):64-74
OBJECTIVE: To study the expression of collagenase 3 (matrix metalloproteinase 13 [MMP-13]) and collagenase 1 (MMP-1) in synovial fibroblasts from patients with rheumatoid arthritis (RA) when cultured within 3-dimensional collagen gels or coimplanted with normal cartilage in immunodeficient NOD/SCID mice. METHODS: Messenger RNA (mRNA) and protein expression of collagenase 3 and collagenase 1 were characterized in synovial and skin fibroblasts by Northern blot and Western blot analysis. The mRNA expression of both collagenases in cell-cartilage implants in NOD/SCID mice was investigated by in situ hybridization in combination with immunohistochemistry of human fibroblasts. RESULTS: Synovial fibroblasts coimplanted with normal cartilage in NOD/SCID mice deeply invaded adjacent cartilage tissue. In this in vivo system of cartilage destruction, collagenase 3 mRNA was induced in synovial fibroblasts at sites of cartilage erosion, while the expression of collagenase 1 mRNA could not be detected. Culture of synovial fibroblasts within 3-dimensional collagen gels was associated with a marked increase in collagenase 3 mRNA expression and proenzyme production. This stimulatory effect was 1 order of magnitude higher in comparison with a 2-4-fold increase upon treatment with interleukin-1beta or tumor necrosis factor a. In contrast, mRNA expression and proenzyme production of collagenase 1 were increased strongly, and to a similar extent, either by contact with 3-dimensional collagen or by proinflammatory cytokines. CONCLUSION: The expression of collagenase 3, in contrast to that of collagenase 1, is preferentially stimulated in synovial fibroblasts by 3-dimensional collagen rather than by proinflammatory cytokines. The induction of collagenase 3 by cell-matrix interactions represents a potential mechanism contributing to the invasive phenotype of synovial fibroblasts at sites of synovial invasion into cartilage in RA. 相似文献
102.
Additive effects of simulated climate changes,elevated CO2, and nitrogen deposition on grassland diversity 总被引:7,自引:0,他引:7
下载免费PDF全文
![点击此处可从《Proceedings of the National Academy of Sciences of the United States of America》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Zavaleta ES Shaw MR Chiariello NR Mooney HA Field CB 《Proceedings of the National Academy of Sciences of the United States of America》2003,100(13):7650-7654
Biodiversity responses to ongoing climate and atmospheric changes will affect both ecosystem processes and the delivery of ecosystem goods and services. Combined effects of co-occurring global changes on diversity, however, are poorly understood. We examined plant diversity responses in a California annual grassland to manipulations of four global environmental changes, singly and in combination: elevated CO2, warming, precipitation, and nitrogen deposition. After 3 years, elevated CO2 and nitrogen deposition each reduced plant diversity, whereas elevated precipitation increased it and warming had no significant effect. Diversity responses to both single and combined global change treatments were driven overwhelmingly by gains and losses of forb species, which make up most of the native plant diversity in California grasslands. Diversity responses across treatments also showed no consistent relationship to net primary production responses, illustrating that the diversity effects of these environmental changes could not be explained simply by changes in productivity. In two- to four-way combinations, simulated global changes did not interact in any of their effects on diversity. Our results show that climate and atmospheric changes can rapidly alter biological diversity, with combined effects that, at least in some settings, are simple, additive combinations of single-factor effects. 相似文献
103.
Erythroid differentiation and protoporphyrin IX down-regulate frataxin expression in Friend cells: characterization of frataxin expression compared to molecules involved in iron metabolism and hemoglobinization
下载免费PDF全文
![点击此处可从《Blood》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Friedreich ataxia (FA) is caused by decreased frataxin expression that results in mitochondrial iron (Fe) overload. However, the role of frataxin in mammalian Fe metabolism remains unclear. In this investigation we examined the function of frataxin in Fe metabolism by implementing a well-characterized model of erythroid differentiation, namely, Friend cells induced using dimethyl sulfoxide (DMSO). We have characterized the changes in frataxin expression compared to molecules that play key roles in Fe metabolism (the transferrin receptor [TfR] and the Fe transporter Nramp2) and hemoglobinization (beta-globin). DMSO induction of hemoglobinization results in a marked decrease in frataxin gene (Frda) expression and protein levels. To a lesser extent, Nramp2 messenger RNA (mRNA) levels were also decreased on erythroid differentiation, whereas TfR and beta-globin mRNA levels increased. Intracellular Fe depletion using desferrioxamine or pyridoxal isonicotinoyl hydrazone, which chelate cytoplasmic or cytoplasmic and mitochondrial Fe pools, respectively, have no effect on frataxin expression. Furthermore, cytoplasmic or mitochondrial Fe loading of induced Friend cells with ferric ammonium citrate, or the heme synthesis inhibitor, succinylacetone, respectively, also had no effect on frataxin expression. Although frataxin has been suggested by others to be a mitochondrial ferritin, the lack of effect of intracellular Fe levels on frataxin expression is not consistent with an Fe storage role. Significantly, protoporphyrin IX down-regulates frataxin protein levels, suggesting a regulatory role of frataxin in Fe or heme metabolism. Because decreased frataxin expression leads to mitochondrial Fe loading in FA, our data suggest that reduced frataxin expression during erythroid differentiation results in mitochondrial Fe sequestration for heme biosynthesis. 相似文献
104.
Katherine R. Amato Marie-Claire Arrieta Meghan B. Azad Michael T. Bailey Josiane L. Broussard Carlijn E. Bruggeling Erika C. Claud Elizabeth K. Costello Emily R. Davenport Bas E. Dutilh Holly A. Swain Ewald Paul Ewald Erin C. Hanlon Wrenetha Julion Ali Keshavarzian Corinne F. Maurice Gregory E. Miller Geoffrey A. Preidis Laure Segurel Burton Singer Sathish Subramanian Liping Zhao Christopher W. Kuzawa 《Proceedings of the National Academy of Sciences of the United States of America》2021,118(25)
Individuals who are minoritized as a result of race, sexual identity, gender, or socioeconomic status experience a higher prevalence of many diseases. Understanding the biological processes that cause and maintain these socially driven health inequities is essential for addressing them. The gut microbiome is strongly shaped by host environments and affects host metabolic, immune, and neuroendocrine functions, making it an important pathway by which differences in experiences caused by social, political, and economic forces could contribute to health inequities. Nevertheless, few studies have directly integrated the gut microbiome into investigations of health inequities. Here, we argue that accounting for host–gut microbe interactions will improve understanding and management of health inequities, and that health policy must begin to consider the microbiome as an important pathway linking environments to population health. 相似文献
105.
Benefits of repeated individual dietary counselling in long‐term weight control in women after delivery
下载免费PDF全文
![点击此处可从《Maternal & child nutrition》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Johanna Jaakkola Erika Isolauri Tuija Poussa Kirsi Laitinen 《Maternal & child nutrition》2015,11(4):1041-1048
As pregnancy may trigger overweight in women, new means for its prevention are being sought. The aim here was to investigate the effect of individual dietary counselling during and after pregnancy on post‐partum weight and waist circumference up to 4 years post‐partum. A cohort of women (n = 256) were randomized to receive repeated individual dietary counselling by a nutritionist during and after pregnancy, or as controls not receiving dietary counselling, from the first trimester of pregnancy until 6 months after delivery. Counselling aimed to bring dietary intake into line with recommendations, with particular focus on the increase in the intake of unsaturated fatty acids instead of saturated. Pre‐pregnancy weight was taken from welfare clinic records. Weight and waist circumference were measured at 4 years after delivery. The proportion of overweight women increased from 26% prior to pregnancy to 30% at 4 years after delivery among women receiving dietary counselling, as against considerably more, from 32% to 57%, among controls. The prevalence of central adiposity was 31% in women receiving dietary counselling, 64% in controls. Likewise, both the risk of overweight (odds ratio: 0.23, 0.08–0.63, P = 0.005) and central adiposity (odds ratio: 0.18, 0.06–0.52, P = 0.002) were lower in women receiving dietary counselling compared with controls. Repeated dietary counselling initiated in early pregnancy can be beneficial in long‐term weight control after delivery. 相似文献
106.
Takeda K Cretney E Hayakawa Y Ota T Akiba H Ogasawara K Yagita H Kinoshita K Okumura K Smyth MJ 《Blood》2005,105(5):2082-2089
Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) is a key effector molecule expressed by natural killer (NK) cells and has been shown to prevent tumor initiation, growth, and metastasis. Here we demonstrate that TRAIL is the dominant cytotoxic effector molecule expressed by NK cells in fetal mice. On birth and with age, NK cells develop full functional capacity, including the ability to secrete interferon gamma (IFN-gamma) and interleukin 13 (IL-13) and mediate perforin- and Fas ligand-mediated cytotoxicity. However, interestingly, a phenotypically immature TRAIL+ NK cell subpopulation is retained in the liver of adult mice, and its retention is dependent on IFN-gamma but not dependent on host IL-12, IL-18, or endogenous host pathogens. Adoptive transfer of either adult liver or neonatal TRAIL+ NK cells resulted in the appearance of TRAIL- NK cells with a mature phenotype, suggesting that these TRAIL+ NK cells were indeed a precursor. Although inducers of IFN-gamma stimulated TRAIL expression on mature NK cells, our data indicated that constitutive TRAIL expression was a hallmark of immature cytotoxic NK cells. This study is the first to describe the concomitant maturation of NK cell effector function with surface phenotype in vivo and implies an important defense role for NK cell TRAIL in the developing immune system. 相似文献
107.
108.
Patient‐level Factors and the Quality of Care Delivered in Pediatric Emergency Departments
下载免费PDF全文
![点击此处可从《Academic emergency medicine》网站下载免费的PDF全文](/ch/ext_images/free.gif)
James P. Marcin MD MPH Patrick S. Romano MD MPH Parul Dayal MS Madan Dharmar MBBS PhD James M. Chamberlain MD Nanette Dudley MD Charles G. Macias MD MPH Lise E. Nigrovic MD MPH Elizabeth C. Powell MD MPH Alexander J. Rogers MD Meridith Sonnett MD Leah Tzimenatos MD Elizabeth R. Alpern MD MSCE Rebecca Andrews‐Dickert MD Dominic A. Borgialli DO MPH Erika Sidney MD T. Charles Casper PhD J. Michael Dean MD Nathan Kuppermann MD MPH for the Pediatric Emergency Care Applied Research Network 《Academic emergency medicine》2018,25(3):301-309
Objective
Quality of care delivered to adult patients in the emergency department (ED) is often associated with demographic and clinical factors such as a patient's race/ethnicity and insurance status. We sought to determine whether the quality of care delivered to children in the ED was associated with a variety of patient‐level factors.Methods
This was a retrospective, observational cohort study. Pediatric patients (<18 years) who received care between January 2011 and December 2011 at one of 12 EDs participating in the Pediatric Emergency Care Applied Research Network (PECARN) were included. We analyzed demographic factors (including age, sex, and payment source) and clinical factors (including triage, chief complaint, and severity of illness). We measured quality of care using a previously validated implicit review instrument using chart review with a summary score that ranged from 5 to 35. We examined associations between demographic and clinical factors and quality of care using a hierarchical multivariable linear regression model with hospital site as a random effect.Results
In the multivariable model, among the 620 ED encounters reviewed, we did not find any association between patient age, sex, race/ethnicity, and payment source and the quality of care delivered. However, we did find that some chief complaint categories were significantly associated with lower than average quality of care, including fever (–0.65 points in quality, 95% confidence interval [CI] = –1.24 to –0.06) and upper respiratory symptoms (–0.68 points in quality, 95% CI = –1.30 to –0.07).Conclusion
We found that quality of ED care delivered to children among a cohort of 12 EDs participating in the PECARN was high and did not differ by patient age, sex, race/ethnicity, and payment source, but did vary by the presenting chief complaint.109.
Erin L. Hickey Erika K. Dumke Rollin L. Ballentine Brooke L. Brown 《Journal of interprofessional care》2018,32(2):250-253
Negative perceptions or underdeveloped understanding of healthcare team member roles can impact the functionality of the team and stunt innovations in interprofessional practice and education. Therefore, the intent of this study was to explore the perception of pharmacists’ role on the healthcare team by future team members: prospective health professional students. The study utilised a survey to examine these perceptions in prospective health professional students (n = 34) nearing the application process to health professional school. A coding process was used to explore open-ended text responses through a line-by-line analysis and identify emerging themes regarding perception of pharmacists’ roles, responsibilities, and practice settings. Quantitative data examined perception of pharmacists by intended prospective profession, healthcare experience, and pharmacy experience. Results indicate that while prospective health professional students find pharmacists to be an important part of the healthcare team, they lack a developed understanding of pharmacists’ roles, responsibilities, and practice settings. Identifying and addressing prospective health professional students’ misperceptions surrounding pharmacists’ roles and responsibilities may encourage them to make informed career decisions and shape them into more knowledgeable future professionals with the ability to better impact patient care on interprofessional teams. 相似文献
110.