全文获取类型
收费全文 | 85577篇 |
免费 | 5040篇 |
国内免费 | 188篇 |
专业分类
耳鼻咽喉 | 1033篇 |
儿科学 | 1967篇 |
妇产科学 | 1678篇 |
基础医学 | 11348篇 |
口腔科学 | 3255篇 |
临床医学 | 6956篇 |
内科学 | 21050篇 |
皮肤病学 | 1841篇 |
神经病学 | 7669篇 |
特种医学 | 2247篇 |
外国民族医学 | 1篇 |
外科学 | 11322篇 |
综合类 | 669篇 |
一般理论 | 42篇 |
预防医学 | 7303篇 |
眼科学 | 1772篇 |
药学 | 5730篇 |
中国医学 | 259篇 |
肿瘤学 | 4663篇 |
出版年
2023年 | 518篇 |
2022年 | 297篇 |
2021年 | 1360篇 |
2020年 | 794篇 |
2019年 | 1421篇 |
2018年 | 2349篇 |
2017年 | 1467篇 |
2016年 | 1571篇 |
2015年 | 2323篇 |
2014年 | 2490篇 |
2013年 | 3758篇 |
2012年 | 6899篇 |
2011年 | 6829篇 |
2010年 | 3197篇 |
2009年 | 2533篇 |
2008年 | 5972篇 |
2007年 | 6246篇 |
2006年 | 6468篇 |
2005年 | 6155篇 |
2004年 | 5576篇 |
2003年 | 5093篇 |
2002年 | 4976篇 |
2001年 | 1828篇 |
2000年 | 2323篇 |
1999年 | 1247篇 |
1998年 | 485篇 |
1997年 | 393篇 |
1996年 | 371篇 |
1995年 | 368篇 |
1994年 | 294篇 |
1993年 | 278篇 |
1992年 | 315篇 |
1991年 | 279篇 |
1990年 | 266篇 |
1989年 | 228篇 |
1988年 | 242篇 |
1987年 | 231篇 |
1986年 | 225篇 |
1985年 | 244篇 |
1984年 | 255篇 |
1983年 | 205篇 |
1982年 | 271篇 |
1981年 | 265篇 |
1980年 | 225篇 |
1979年 | 172篇 |
1978年 | 137篇 |
1977年 | 118篇 |
1976年 | 106篇 |
1974年 | 119篇 |
1973年 | 93篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
981.
目的:报道经玻璃体腔内注射高剂量曲安奈德(triamcinolone acetonide,TA)联合光动力学疗法(photodynamic therapy,PDT)治疗老年性黄斑变性( age related macular degeneration, AMD)的脉络膜新生血管(choroidal neovascularization,CNV)后发生的脉络膜毛细血管萎缩。方法:我们采用非随机回顾性干涉治疗病例。在阿利坎特学院眼科,连续观察51眼(实验组)玻璃体腔内的注射(19.4±2.1)mg/0.1mL TA联合PDT治疗AMD的全部中心凹下型CNV患者,经过2a的随访,检查黄斑部脉络膜毛细血管和视网膜色素上皮细胞(RPE)萎缩情况。同时,采用单独PDT治疗的连续30眼患者作为对照组,其年龄,性别和AMD的CNV类型及大小与实验组相匹配。结果:随访24mo后,在治疗区域21/47眼(45%,实验组)和7/30眼(23%,对照组)发展成黄斑部RPE和脉络膜毛细血管萎缩(P=0.04,卡方检验)。实验组平均最大萎缩区域的直径为(5044±1666)μm,而对照组为(4345±1550)μm。在实验组中,RPE萎缩患者的平均最佳矫正视力为(0.87±0.33),而非RPE萎缩患者的平均最佳矫正视力为(0.66±0.26) (P=0.11,秩和U检验)。结论:玻璃体腔内注射大剂量TA联合PDT治疗可能会增加RPE和脉络膜毛细血管萎缩的风险。 相似文献
982.
Marie-Laure Paillère Martinot Jean-Luc Martinot Damien Ringuenet André Galinowski Thierry Gallarda Frank Bellivier Jean-Pascal Lefaucheur Hervé Lemaitre Eric Artiges 《Neuropsychopharmacology》2011,36(13):2710-2719
Neuroimaging studies of patients with treatment-resistant depression (TRD) have reported abnormalities in the frontal and temporal regions. We sought to determine whether metabolism in these regions might be related to response to repetitive transcranial magnetic stimulation (TMS) in patients with TRD. Magnetic resonance images and baseline resting-state cerebral glucose uptake index (gluMI) obtained using 18F-fluorodeoxyglucose positron emission tomography were analyzed in TRD patients who had participated in a double-blind, randomized, sham-controlled trial of prefrontal 10 Hz TMS. Among the patients randomized to active TMS, 17 responders, defined as having 50% depression score decrease, and 14 nonresponders were investigated for prestimulation glucose metabolism and compared with 39 healthy subjects using a voxel-based analysis. In nonresponders relative to responders, gluMI was lower in left lateral orbitofrontal cortex (OFC), and higher in left amygdala and uncinate fasciculus. OFC and amygdala gluMI negatively correlated in nonresponders, positively correlated in responders, and did not correlate in healthy subjects. Relative to healthy subjects, both responders and nonresponders displayed lower gluMI in right dorsolateral prefrontal (DLPFC), right anterior cingulate (ACC), and left ventrolateral prefrontal cortices. Additionally, nonresponders had lower gluMI in left DLPFC, ACC, left and right insula, and higher gluMI in left amygdala and uncus. Hypometabolisms were partly explained by gray matter reductions, whereas hypermetabolisms were unrelated to structural changes. The findings suggest that different patterns of frontal–temporal–limbic abnormalities may distinguish responders and nonresponders to prefrontal magnetic stimulation. Both preserved OFC volume and amygdala metabolism might precondition response to TMS. 相似文献
983.
Gene expression changes induced by ochratoxin A in renal and hepatic tissues of male F344 rat after oral repeated administration 总被引:2,自引:0,他引:2
Arbillaga L Vettorazzi A Gil AG van Delft JH García-Jalón JA López de Cerain A 《Toxicology and applied pharmacology》2008,230(2):197-207
Ochratoxin A (OTA), a naturally occurring mycotoxin, is nephrotoxic in all animal species tested and is considered a potent renal carcinogen, particularly in male rats. Its mechanism of toxicity is still unknown, although oxidative stress appears to be a plausible mechanism. Therefore, the objective of this study was to identify the biological pathways that are modulated in vivo by OTA in male F344 rats in order to gain further insight into its mechanism of renal toxicity. Rats were gavaged daily with OTA (500 microg/kg bw) and gene expression profiles in target and non-target organs were analyzed after 7 and 21 days administration. As was expected, a time-dependent increase of OTA concentrations was found in plasma, kidney and liver, with the concentrations found in both tissues being quite similar. However, histopathological examinations only revealed changes in kidney; signs of nephrotoxicity involving single cell necrosis and karyomegalic nuclei were observed in the treated rats. The number of differentially expressed genes in kidney was much higher than in liver (541 versus 11 at both time points). Several similarities were observed with other in vivo gene expression data. However, great differences were found with previous in vitro gene expression data, with the exception of DNA damage response which was not observed at mRNA level in any of our study conditions. Down-regulation was the predominant effect. Oxidative stress response pathway and genes involved in metabolism and transport were inhibited at both time points. RGN (regucalcin) - a gene implicated in calcium homeostasis - was strongly inhibited at both time points and genes implicated in cell survival and proliferation were up-regulated at day 21. Moreover, translation factors and annexin genes were up-regulated at both time points. Apart from oxidative stress, alterations of the calcium homeostasis and cytoskeleton structure may be present at the first events of OTA toxicity. 相似文献
984.
Chanellé Hendrikse Hilmar Klaus Lückhoff Jean-Paul Fouché Leigh L. van den Heuvel Robin Emsley Soraya Seedat Stefan du Plessis 《Journal of neuroscience research》2024,102(2):e25308
Childhood trauma (CT) may influence brain white matter microstructure; however, few studies have examined the differential impact of distinct CT types on white matter microstructure in psychiatrically healthy adults living in a developing country. In adults without significant medical or psychiatric disorders, we investigated the association(s) between CT, including abuse and neglect, and fractional anisotropy (FA) of limbic tracts previously shown to be associated with CT. Participants underwent diffusion tensor imaging and completed the Childhood Trauma Questionnaire. Multivariate analysis of variance models were used to test the effects of total overall CT, as well as CT subtypes, on FA in six fronto-limbic tracts, adjusting for age, sex, and educational level. The final sample included 69 adults (age 47 ± 17 years; 70% female). Overall, CT had a significant main effect on FA for tracts of interest (p < .001). Greater CT severity was associated with lower FA for the bilateral and left stria terminalis (uncorrected) as well as the bilateral, left, and right anterior limb of the internal capsule (ALIC; corrected). Exposure to total non-violent/deprivational trauma specifically was associated with lower FA of the bilateral, left, and right ALIC, suggesting that distinct types of CT are associated with differential white matter changes in apparently healthy adults. The ALIC predominantly carries fibers connecting the thalamus with prefrontal cortical regions. Microstructural alterations in the ALIC may be associated with functional brain changes, which may be adaptive or increase the risk of accelerated age-related cognitive decline, maladaptive behaviors, and subsyndromal psychiatric symptoms. 相似文献
985.
Elizabeth Abbs Naomi Schoenfeld Mason Lai Shannon Satterwhite Sara Zhou Joshua Bamberger Barry Zevin 《Journal of urban health》2023,100(2):303
In this study, we consider the patient, provider, and public health repercussions of San Francisco’s (SF) COVID-related response to homelessness using tourist hotels to house people experiencing homelessness (PEH). We describe the demographics, medical comorbidities, and healthcare utilization patterns of a subset of PEH who accessed the shelter-in-place (SIP) hotel sites during the 2020–2021 pandemic. We focus on how SIP hotels impacted connection to outpatient care and higher-cost emergency utilization. Our mixed methods study integrates qualitative and quantitative data to consider the impact of this temporary housing initiative among a medically complex cohort in a time of increased morbidity and mortality related to substance use. We found that temporary SIP housing increased outpatient care and reduced higher-cost hospital utilization. Our results can inform the future design and implementation of integrated supportive housing models to reduce mortality and promote wellness for PEH. 相似文献
986.
Arian Khorshid Anjali Wignarajah Jiaqi Zhang Ruben Alvero Ruth B. Lathi Barry Behr Gayathree Murugappan 《Journal of assisted reproduction and genetics》2023,40(1):153
Purpose To explore perceptions towards embryo disposition among patients donating excess embryos to a research biobank.MethodsCross-sectional study of survey responses collected as part of enrollment in a research biobank. Patients are asked questions regarding the difficulty of their disposition decision, their alternative disposition choice if donation to research was not available, quality of the counseling they received, and if additional counseling throughout their treatment would have been beneficial. Survey responses use 5-point Likert scales, with “1” being lowest/least and “5” being highest/most.ResultsA total of 157 men and 163 women enrolled in the biobank. Median scores for difficulty of disposition decision were 3 for females and 2 for males, and for quality of counseling, the median scores were 4 for females and 3 for males. Seventy percent of patients would have chosen to discard their excess embryos had donation to research not been an option. Statistical analyses showed no significant difference in responses based on variations in race, religion, sexual orientation, and infertility diagnoses. Concordance of responses within heterosexual couples was tested and found to be poor to moderate.ConclusionsAssessing patients’ perceptions towards embryo disposition after donation of their excess embryos to a research biobank affords a unique perspective. The difficulty of the disposition decision, the tendency to discard embryos in the absence of a means for donation to research, and the poor agreement between heterosexual partners highlight the importance of donation to research as an accessible disposition option and the need for a personalized approach to counseling and consenting for embryo disposition.Supplementary InformationThe online version contains supplementary material available at 10.1007/s10815-022-02659-x.Keyword: Embryo disposition 相似文献
987.
988.
Eduardo Tamayo Inma Fierro Juan Bustamante-Munguira María Heredia-Rodríguez Pablo Jorge-Monjas Laura Maroto Esther Gómez-Sánchez Francisco Jesús Bermejo-Martín Francisco Javier álvarez José Ignacio Gómez-Herreras 《Critical care (London, England)》2013,17(5):R209
IntroductionThe risk of mortality in cardiac surgery is generally evaluated using preoperative risk-scale models. However, intraoperative factors may change the risk factors of patients, and the organism functionality parameters determined upon ICU admittance could therefore be more relevant in deciding operative mortality. The goals of this study were to find associations between the general parameters of organism functionality upon ICU admission and the operative mortality following cardiac operations, to develop a Post Cardiac Surgery (POCAS) Scale to define operative risk categories and to validate an operative mortality risk score.MethodsWe conducted a prospective study, including 920 patients who had undergone cardiac surgery with cardiopulmonary bypass. Several parameters recorded on their ICU admission were explored, looking for a univariate and multivariate association with in-hospital mortality (90 days). In-hospital mortality was 9%. Four independent factors were included in the POCAS mortality risk model: mean arterial pressure, bicarbonate, lactate and the International Normalized Ratio (INR). The POCAS scale was compared with four other risk scores in the validation series.ResultsIn-hospital mortality (90 days) was 9%. Four independent factors were included in the POCAS mortality risk model: mean arterial pressure, bicarbonate ratio, lactate ratio and the INR. The POCAS scale was compared with four other risk scores in the validation series. Discriminatory power (accuracy) was defined with a receiver-operating characteristics (ROC) analysis. The best accuracy in predicting in-hospital mortality (90 days) was achieved by POCAS. The areas under the ROC curves of the different systems analyzed were 0.890 (POCAS), followed by 0.847 (Simplified Acute Physiology Score (SAP II)), 0.825 (Sepsis-related Organ Failure Assessment (SOFA)), 0.768 (Acute Physiology and Chronic Health Evaluation (APACHE II)), 0.754 (logistic EuroSCORE), 0.714 (standard EuroSCORE) and 0.699 (Age, Creatinine, Ejection Fraction (ACEF) score).ConclusionsOur new system to predict the operative mortality risk of patients undergoing cardiac surgery is better than others used for this purpose (SAP II, SOFA, APACHE II, logistic EuroSCORE, standard EuroSCORE, and ACEF score). Moreover, it is an easy-to-use tool since it only requires four risk factors for its calculation. 相似文献
989.
Amniotic membrane stimulates cell migration by modulating transforming growth factor‐β signalling 下载免费PDF全文
Sergio Liarte Carmen Luisa Insausti Diego Angosto José M. Moraleda Gregorio Castellanos Francisco José Nicolás 《Journal of tissue engineering and regenerative medicine》2018,12(3):808-820
Keratinocyte migration is a mandatory aspect of wound healing. We have previously shown that amniotic membrane (AM) applied to chronic wounds assists healing through a process resulting in the overexpression of c‐Jun at the wound's leading edge. We have also demonstrated that AM modifies the genetic programme induced by transforming growth factor‐ß (TGF‐ß) in chronic wounds. Here we used a scratch assay of mink lung epithelial cells (Mv1Lu) and a spontaneously immortalized human keratinocyte cell line (HaCaT) cells to examine the influence of AM application on the underlying signalling during scratch closure. AM application induced c‐Jun phosphorylation at the leading edge of scratch wounds in a process dependent on MAPK and JNK signalling. Strikingly, when the TGF‐ß‐dependent Smad‐activation inhibitor SB431542 was used together with AM, migration improvement was partially restrained, whereas the addition of TGF‐ß had a synergistic effect on the AM‐induced cell migration. Moreover, antagonizing TGF‐ß with specific antibodies in both cell lines or knocking out TGF‐ß receptors in Mv1Lu cells had similar effects on cell migration as using SB431542. Furthermore, we found that AM was able to attenuate TGF‐ß‐Smad signalling specifically at the migrating edge; AM treatment abated Smad2 and Smad3 nuclear localization in response to TGF‐ß in a process dependent on mitogen‐activated protein kinase kinase 1 (MEK1) activation but independent of EGF receptor or JNK activation. The involvement of Smad signalling on AM effects on HaCaT keratinocytes was further corroborated by overexpression of either Smad2 or Smad3 and the use of Smad phosphorylation‐specific inhibitors, revealing a differential influence on AM‐induced migration for each Smad. Thus, AM TGF‐ß‐Smad signalling abating is essential for optimal cell migration and wound closure. 相似文献
990.
Rachael N. Martinez Bridget M. Smith Dustin D. French Timothy P. Hogan Beverly Gonzalez Chad M. Osteen Maya Hatch Vicki Anderson Elizabeth Tarlov Abigail Silva Barry Goldstein Kevin T. Stroupe 《The journal of spinal cord medicine》2022,45(4):575
Context/Objective: Provisions of the Affordable Care Act (ACA) potentially increase insurance options for Veterans with disabilities. We examined Veterans with spinal cord injuries and disorders (SCI/D) to assess whether the ACA was associated with changes in healthcare utilization from Department of Veterans Affairs (VA) healthcare facilities.Design: Using national VA data, we investigated impacts on VA healthcare utilization pre- (2012/13) and post-ACA (2014/15) implementation with negative binomial regression models.Setting: VA healthcare facilities.Participants: 8,591 VA users with SCI/D. Veterans with acute myelitis, Guillain-Barré syndrome, multiple sclerosis, or amyotrophic lateral sclerosis were excluded as were patients who died during the study period.Interventions: We assessed VA healthcare utilization before and after ACA implementation.Outcome Measures: Total numbers of VA visits for SCI/D care, diagnostic care, primary care, specialty care, and mental health care, and VA admissions.Results: The number of VA admissions was 7% higher in the post than pre-ACA implementation period (P < 0.01). The number of VA visits post-implementation increased for SCI/D care (8%; P < 0.01) and specialty care (12%; P < 0.001). Conversely, the number of mental health visits was 17% lower in the post-ACA period (P < 0.001). Veterans with SCI/D who live <5 miles from their nearest VA facility received VA care more frequently than those ≥40 miles from VA (P < 0.001).Conclusion: Counter to expectations, results suggest that Veterans with SCI/D sought more frequent VA care after ACA implementation, indicating Veterans with SCI/D continue to utilize the lifelong, comprehensive care provided at VA. 相似文献