全文获取类型
收费全文 | 25486篇 |
免费 | 1810篇 |
国内免费 | 56篇 |
专业分类
耳鼻咽喉 | 316篇 |
儿科学 | 519篇 |
妇产科学 | 552篇 |
基础医学 | 3240篇 |
口腔科学 | 395篇 |
临床医学 | 2990篇 |
内科学 | 5136篇 |
皮肤病学 | 348篇 |
神经病学 | 2231篇 |
特种医学 | 972篇 |
外科学 | 4329篇 |
综合类 | 213篇 |
一般理论 | 167篇 |
预防医学 | 1959篇 |
眼科学 | 639篇 |
药学 | 1657篇 |
中国医学 | 21篇 |
肿瘤学 | 1668篇 |
出版年
2024年 | 27篇 |
2023年 | 266篇 |
2022年 | 440篇 |
2021年 | 1051篇 |
2020年 | 522篇 |
2019年 | 893篇 |
2018年 | 974篇 |
2017年 | 709篇 |
2016年 | 743篇 |
2015年 | 846篇 |
2014年 | 1249篇 |
2013年 | 1412篇 |
2012年 | 2297篇 |
2011年 | 2345篇 |
2010年 | 1218篇 |
2009年 | 1121篇 |
2008年 | 1726篇 |
2007年 | 1665篇 |
2006年 | 1508篇 |
2005年 | 1410篇 |
2004年 | 1211篇 |
2003年 | 1063篇 |
2002年 | 881篇 |
2001年 | 168篇 |
2000年 | 150篇 |
1999年 | 128篇 |
1998年 | 127篇 |
1997年 | 96篇 |
1996年 | 73篇 |
1995年 | 53篇 |
1994年 | 55篇 |
1993年 | 48篇 |
1992年 | 69篇 |
1991年 | 68篇 |
1990年 | 62篇 |
1989年 | 79篇 |
1988年 | 60篇 |
1987年 | 49篇 |
1986年 | 63篇 |
1985年 | 63篇 |
1984年 | 35篇 |
1983年 | 30篇 |
1982年 | 31篇 |
1981年 | 22篇 |
1980年 | 25篇 |
1979年 | 27篇 |
1977年 | 18篇 |
1976年 | 21篇 |
1975年 | 19篇 |
1966年 | 20篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
Fiona Murray Paul A. Insel Jason X.-J. Yuan 《Respiratory physiology & neurobiology》2006,151(2-3):192
High altitude pulmonary edema (HAPE) is a potentially fatal complication in response to exposure to low O2 at high altitudes. Hypoxia, by causing pulmonary vasoconstriction, increases pulmonary vascular resistance and pulmonary arterial pressure, both of which are features in the pathogenesis of HAPE. Uneven hypoxic pulmonary vasoconstriction is thought to be responsible for increased capillary pressure and leakage, resulting in edema. O2-sensitive ion channels are known to play pivotal roles in determining vascular tone in response to hypoxia. K+, Ca2+ and Na+ channels are ubiquitously expressed in both endothelial and smooth muscle cells of the pulmonary microvasculature, subfamilies of which are regulated by local changes in PO2. Hypoxia reduces activity of voltage-gated K+ channels and down-regulates their expression leading to membrane depolarization, Ca2+ influx in pulmonary artery smooth muscle cells (by activating voltage-dependent Ca2+ channels) and vasoconstriction. Hypoxia up-regulates transient receptor potential channels (TRPC) leading to enhanced Ca2+ entry through receptor- and store-operated Ca2+ channels. Altered enrichment of ion channels in membrane microdomains, in particular in caveolae, may play a role in excitation–contraction coupling and perhaps in O2-sensing in the pulmonary circulation and thereby may contribute to the development of HAPE. We review the role of ion channels, in particular those outlined above, in response to low O2 on vascular tone and pulmonary edema. Advances in the understanding of ion channels involved in the physiological response to hypoxia should lead to a greater understanding of the pathogenesis of HAPE and perhaps in the identification of new therapies. 相似文献
112.
Variation in response latency to identical sensory stimuli has been attributed to variation in neural activity mediating preparatory set. Here we report evidence for a relationship between saccadic reaction time (SRT) and set-related brain activity measured with event-related functional magnetic resonance imaging. We measured hemodynamic activation time-courses during a preparatory "gap" period, during which no visual stimulus was present and no saccades were made. The subjects merely anticipated appearance of the target. Saccade direction and latency were recorded during scanning, and trials were sorted according to SRT. Both the frontal (FEF) and supplementary eye fields showed pre-target preparatory activity, but only in the FEF was this activity correlated with SRT. Activation in the intraparietal sulcus did not show any preparatory activity. These data provide evidence that the human FEF plays a central role in saccade initiation; pre-target activity in this region predicts both the type of eye movement (whether the subject will look toward or away from the target) and when a future saccade will occur. 相似文献
113.
114.
Eric B. Hekler Jason Rubenstein Elliot J. Coups Suzanne Gilligan Alexander W. Kusnecov Richard J. Contrada Matthew J. Steiner Alan K. Tannenbaum Elaine A. Leventhal and Tyrone J. Krause 《Journal of Applied Biobehavioral Research》2007,12(2):65-81
Inflammatory activity has been associated with both coronary disease and depressive symptoms. We sought to determine whether inflammatory markers in myocardial infarction (MI) patients are prospectively associated with depressive symptomatology. Participants were a convenience sample of MI patients. Depressive symptoms were assessed soon after the MI and again 7 months postdischarge. Inflammatory markers examined were interleukin-6 (IL-6) and interleukin-1β. Results suggest no significant cross-sectional association between inflammatory markers and depressive symptoms at baseline. However, bivariate and multiple regression analyses revealed a significant positive prospective association between baseline IL-6 and depressive symptoms 7 months later ( β = .57, p < .01). The results suggest that temporal considerations are important in understanding relationships between inflammation and depressive symptoms following MI. 相似文献
115.
BACKGROUND AND AIMS: Angiomyolipomas (AMLs) of the liver are rare neoplasms composed of large epithelioid cells with intermixed fat and blood vessels. Hepatic AMLs have no clear normal-cell counterpart in the liver. However, AMLs and stellate cells both are positive for neural crest-derived markers including HMB-45 antigen. METHODS: To further explore the similarities between hepatic AMLs and stellate cells, gene expression of a hepatic AML was studied by cDNA microarray. Real-time polymerase chain reaction was used to confirm gene expression. Hepatic stellate cells can be quiescent, activated, or have a myofibroblastic phenotype depending on their state of activation. Expression of known markers of activated stellate cells was compared between the AML, activated primary mouse stellate cells, and stellate cell lines with activated and myofibroblastic phenotypes. Next, 5 novel genes from the AML were selected because they were not previously known to be markers of stellate cells and mRNA expression measured in the activated mouse stellate cells and in myofibroblastic stellate cell lines. Finally, expression levels of 10 novel genes were determined in 5 cirrhotic and 5 noncirrhotic human livers. RESULTS: Overexpression of known markers of activated stellate cells including transforming growth factor beta (TGF- beta ), smooth muscle actin, and collagen was found in the hepatic AML. Three of 5 novel markers that were identified in the AML, RRAD (Ras-related associated with diabetes), CTSK (cathepsin K), and NIBAN were also found to be overexpressed in activated stellate cells compared with quiescent or myofibroblastic stellate cells. In addition, 9 of 10 novel genes overexpressed in AML were also overexpressed in cirrhotic human livers versus noncirrhotic livers. CONCLUSIONS: Hepatic AMLs share a similar gene expression profile and may differentiate toward activated stellate cells. 相似文献
116.
Smith CM Wilson NS Waithman J Villadangos JA Carbone FR Heath WR Belz GT 《Nature immunology》2004,5(11):1143-1148
Several studies have indicated that CD8(+) T cells require CD4(+) T cell help for memory formation. Evidence suggests that such help can be antigen independent, challenging whether the 'licensing' of dendritic cells (DCs) by CD4(+) T cells is ever required for cytotoxic T lymphocyte (CTL) responses. We show here that help is essential for the generation of CTL immunity to herpes simplex virus 1 and that CD4(+) T cells mediate help in a cognate, antigen-specific way. We provide direct in vivo evidence for DC licensing by helper T cells and show that licensing is rapid and essential for the formation of effector and memory CTLs. In situations in which DCs are poorly licensed by pathogen-derived signals, our findings suggest that CTL immunity may be heavily dependent on cognate DC licensing. 相似文献
117.
On the ERN and the significance of errors 总被引:3,自引:0,他引:3
The error-related negativity (ERN) is an event-related brain potential observed when subjects commit errors. To examine whether the ERN is sensitive to the value of errors, the motivational significance of errors was manipulated in two experiments. In Experiment 1, low and high monetary value errors were compared to evaluate the effect of trial value on the ERN. In Experiment 2, subjects performed a flanker task both while their performance was being evaluated and during a control condition. Consistent with the notion that the error-detection system is sensitive to the significance of errors, the ERN was significantly larger on high-value trials in Experiment 1 and during evaluation in Experiment 2. There were no corresponding effects on the correct response negativity, and no behavioral differences between conditions were evident in either experiment. These results are discussed in terms of the functional role of the ERN in response monitoring. 相似文献
118.
Alessio HM Hagerman AE Nagy S Philip B Byrnes RN Woodward JL Callahan P Wiley RL 《Physiology & behavior》2005,84(1):65-72
Voluntary and forced exercise decrease morbidity and mortality in laboratory animals. Caloric restriction has similar effects on health and unique benefits on life span. Nonetheless, in most experiments, animals do not have access to physical activity and are fed ad libitum (AL). We hypothesized that with regular access to either unlimited running wheel exercise (EX) or limited physical activity (PA), key biomarkers of health would be enhanced enough to counter some consequences of a sedentary AL lifestyle. This 16-month study compared body weight, tumor number and size, tissue lesions, oxidative stress, and reactive stress in (1) sedentary animals with no access to physical activity (SED); (2) animals with access to hour-long, twice weekly activity in a large box (PA); and (3) animals with access every other day to a running wheel (EX). At the end of the study, EX body weight was 8-9% lower than PA and SED. In addition, EX had no kidney lesions versus 50% in PA and SED, and had smaller tumor size (10+/-2 vs. 14+/-4 and 30+/-4 mm). Exhaustive exercise lowered glutathione/oxidized glutathione ratio in EX and PA, but in SED, the ratio was depressed even in resting animals. In all treatments, prolactin (PRL) levels were lower in resting animals than in acutely exercised animals. In conclusion, EX had the most favorable health biomarkers while SED had the least. PA did not confer gross health benefits different than the SED group, but was biochemically more similar to EX animals. 相似文献
119.
Leonard A. Jason Steven B. Pokorny Mazna Patka Monica Adams Taylor Morello 《Journal of community psychology》2007,35(8):967-979
Two primary outlets for community psychology research, the American Journal of Community Psychology and the Journal of Community Psychology, were assessed to rank institutions based on publication frequency and scientific influence of publications over a 32‐year period. Three specific periods were assessed (1973–1983, 1984–1994, 1995–2004). Findings indicate that there were a large group of institutions that published articles during these periods. Those academic institutions that had the most published articles as well as the largest influence, based on citations by other authors, were identified. Using archival data from the community psychology literature represents one approach for identifying those settings that made substantial contributions to the development and growth of the field. © 2007 Wiley Periodicals, Inc. J Comm Psychol 35: 967–979, 2007. 相似文献
120.
Kennedy J Jackson G Ramsden S Taylor J Newman W Wright MJ Donnai D Elles R Briggs MD 《European journal of human genetics : EJHG》2005,13(5):547-555
The skeletal dysplasias are a clinically and genetically heterogeneous group of conditions affecting the development of the osseous skeleton and fall into the category of rare genetic diseases in which the diagnosis can be difficult for the nonexpert. Two such diseases are pseudoachondroplasia (PSACH) and multiple epiphyseal dysplasia (MED), which result in varying degrees of short stature, joint pain and stiffness and often resulting in early onset osteoarthritis. PSACH and some forms of MED result from mutations in the cartilage oligomeric matrix protein (COMP) gene and to aid the clinical diagnosis and counselling of patients with a suspected diagnosis of PSACH or MED, we developed an efficient and accurate molecular diagnostic service for the COMP gene. In a 36-month period, 100 families were screened for a mutation in COMP and we identified disease-causing mutations in 78% of PSACH families and 36% of MED families. Furthermore, in several of these families, the identification of a disease-causing mutation provided information that was immediately used to direct reproductive decision-making. 相似文献