收费全文 | 2369149篇 |
免费 | 167708篇 |
国内免费 | 17855篇 |
耳鼻咽喉 | 33566篇 |
儿科学 | 70803篇 |
妇产科学 | 64699篇 |
基础医学 | 328233篇 |
口腔科学 | 66689篇 |
临床医学 | 217187篇 |
内科学 | 445358篇 |
皮肤病学 | 51149篇 |
神经病学 | 180435篇 |
特种医学 | 92223篇 |
外国民族医学 | 691篇 |
外科学 | 351445篇 |
综合类 | 81897篇 |
现状与发展 | 54篇 |
一般理论 | 710篇 |
预防医学 | 167270篇 |
眼科学 | 57670篇 |
药学 | 188172篇 |
179篇 | |
中国医学 | 16014篇 |
肿瘤学 | 140268篇 |
2021年 | 24713篇 |
2019年 | 21585篇 |
2018年 | 28250篇 |
2017年 | 23203篇 |
2016年 | 24905篇 |
2015年 | 30289篇 |
2014年 | 40766篇 |
2013年 | 54248篇 |
2012年 | 74011篇 |
2011年 | 79005篇 |
2010年 | 47148篇 |
2009年 | 43177篇 |
2008年 | 69260篇 |
2007年 | 74101篇 |
2006年 | 74505篇 |
2005年 | 72143篇 |
2004年 | 66481篇 |
2003年 | 63435篇 |
2002年 | 61130篇 |
2001年 | 108673篇 |
2000年 | 111738篇 |
1999年 | 95301篇 |
1998年 | 27374篇 |
1997年 | 25028篇 |
1996年 | 23727篇 |
1995年 | 22292篇 |
1994年 | 20532篇 |
1992年 | 71119篇 |
1991年 | 68602篇 |
1990年 | 67217篇 |
1989年 | 65070篇 |
1988年 | 59937篇 |
1987年 | 58728篇 |
1986年 | 55872篇 |
1985年 | 52830篇 |
1984年 | 39207篇 |
1983年 | 33299篇 |
1982年 | 19452篇 |
1979年 | 36851篇 |
1978年 | 25863篇 |
1977年 | 22701篇 |
1976年 | 20381篇 |
1975年 | 23114篇 |
1974年 | 27301篇 |
1973年 | 26621篇 |
1972年 | 25324篇 |
1971年 | 23720篇 |
1970年 | 22244篇 |
1969年 | 21377篇 |
1968年 | 19723篇 |
Material and Methods: This retrospective study included 365 eyes that underwent PK using corneas from 231 donors between June 2010 and June 2015. Patients were divided into three groups (group 1: primary endothelial diseases; group 2: iatrogenic endothelial disorders; and group 3: other pathologies with a healthy endothelium) according to PK indications. The primary outcome measure was corneal graft survival at the last visit (clear or opaque). Graft clarity was assessed using Kaplan–Meier survival analysis.
Results: The most frequent PK indication was keratoconus (KC) (20.5%) followed by pseudophakic bullous keratopathy (PBK) (18.9%). Donor age had a negative impact on endothelial cell density (ECD) measured by an eye bank specular microscope (p < 0.001). Median best-corrected visual acuity in logarithm of the minimum angle of resolution units increased from 2.1 to 0.8 at 1 year after PK (p < 0.001). The clear graft rate was 96.7% at year 1, 88.8% at year 2, and 85.5% at year 3. Overall graft survival was 84.9% during a median of 39 months (range: 24–79 months) of follow-up. A higher graft survival rate (67.2%) was observed in KC compared to PBK during 6 years (p < 0.001). Recipients younger than 50 years of age showed a better graft survival rate than those older than 70 years of age (p = 0.037). Donor ECD, time between excision and death, and preservation time had no significant effect on graft survival. Frequent graft rejection episodes (GREs) and additional procedures during surgery had a negative impact on graft survival (p < 0.001 and p = 0.014, respectively). A worse graft survival was observed in group 2 compared to groups 1 and 3 (p = 0.042).
Conclusions: Young recipient age and KC were associated with a better graft survival. Graft endothelial density and preservation time had no impact on graft survival. PBK, low vision at baseline and year 1, frequent GREs, and additional interventions during surgery had a negative impact on graft survivals. 相似文献
Aims
Delaying progression, ameliorating symptoms and maintaining quality of life (QoL) are primary aims of treatment for metastatic castrate-resistant prostate cancer (mCRPC). Real-world rather than clinical trial data about symptoms and side-effects are sparse. In EXTREQOL, patients' QoL, pain and information needs were recorded during treatment.Material and methods
Men with mCRPC from 20 UK cancer centres starting various systemic mCRPC treatments completed QoL, pain and information needs questionnaires at baseline, 3 and 6 months.Results
In total, 132 patients were recruited. Overall QoL declined significantly by 6 months (Functional Assessment of Cancer Therapy-Prostate [FACT-P] mean = –3.89, 95% confidence interval –6.7 to –1.05, P = 0.007; Trial Outcome Index [TOI] analysis mean = –3.10, 95% confidence interval –5.34 to –0.83, P = 0.007). Those who came off novel therapy and remained on luteinising hormone-releasing hormone agonist therapy alone had worse scores than patients receiving concomitant chemotherapy (Prostate Concerns Subscale mean difference = –4.45, 95% confidence interval –7.06 to –1.83, P = 0.001; TOI mean difference = –5.62, 95% confidence interval –10.97 to –0.26, P = 0.040). At 3 and 6 months, men who reported pain at baseline improved (43%, 40%), but for others pain levels remained the same (45%, 42%) or worsened (13%, 18%). Information regarding supportive care was lacking throughout the period of time on the study.Conclusion
Most mCRPC treated patients experience reduced QoL and inadequate pain control. More help with pain management and better information provision regarding supportive care is warranted. 相似文献Aims
To obtain an overview of the management and outcomes of children aged 18 years or younger diagnosed with differentiated thyroid carcinoma of follicular cell origin across the UK, by collecting and analysing data from the limited number of centres treating these patients. This multicentre data might provide a more realistic perspective than single-institution series.Materials and methods
Six centres submitted data extracted from historical records on patients aged 18 years or younger, diagnosed between 1964 and 2017. The univariate and multivariable Cox proportional hazard model was used to identify potential predictors of progression-free survival, using national data as a control.Results
Data on 166 patients were available for analysis. Females (74%) were predominant, and the age ranged from 3 to 19 years at diagnosis, mean 14.1 years. Nodal metastases were present in 51%; 12% had distant metastases. After surgery, 95% received radioactive iodine (39% on more than one occasion) and 4% received external beam radiotherapy. With a median follow-up duration of 5 years, 69% are alive with no evidence of disease; 20% are alive with a raised thyroglobulin level as the only evidence of residual disease; 6% have residual structural disease detectable on imaging; 2% have died, from cerebral metastases.Conclusion
Despite most patients having advanced disease at presentation, outcomes are very good. A national prospective registry should allow systematic collection of good-quality data and may facilitate research to further improve outcomes. 相似文献Introduction
Malignant pleural mesothelioma (MPM) is an uncommon cancer with a poor prognosis and heterogeneous survival. Surgery for MPM is offered in some specialist centers to highly selected patients. A previously described classification and regression tree (CART) model stratified survival in unselected MPM patients using routinely collected clinical data. This study aimed to examine the performance of this CART model on a highly selected surgical population.Methods
Data were collected from subjects undergoing cytoreductive surgery for MPM from specialist centers in Hyõgo, Japan, and Sydney, Australia, between 1991 and 2016. The CART model was applied using the combination of clinical variables to stratify subjects into risk groups (1 through 4); survival characteristics were then compared.Results
Two hundred eighty-nine cases were included (205 from Australia, 84 from Japan). Overall median survival was 34.6 (interquartile range: 17.5–56.1) months; median age was 63.0 (interquartile range: 57.0–67.8) years, and 83.0% (n = 240) were male. There were no clinically meaningful differences between the two cohorts. Survival across the four risk groups was significantly different (p < 0.0001); the model stratified survival well with a Harrell's concordance statistic of 0.62 (95% confidence interval: 0.57–0.66) at 36 months. The group with the longest survival (median, 82.5 months) had: no weight loss, hemoglobin > 153 g/L and serum albumin > 43 g/L at time of referral to the surgical center.Conclusions
Using routinely available clinical variables, the CART model was able to stratify surgical patients into risk groups with statistically different survival characteristics with fair to good performance. Presence of weight loss, anemia, and low albumin should confer caution when considering surgical therapy for MPM. 相似文献Cellular arachidonic acid (AA), an unsaturated fatty acid found ubiquitously in plasma membranes, is metabolized to different prostanoids, such as prostacyclin (PGI2) and prostaglandin E2 (PGE2), by the three-step reactions coupling the upstream cyclooxygenase (COX) isoforms (COX-1 and COX-2) with the corresponding individual downstream synthases. While the vascular actions of these prostanoids are well-characterized, their specific roles in the hippocampus, a major brain area for memory, are poorly understood. The major obstacle for its understanding in the brain was to mimic the biosynthesis of each prostanoid. To solve the problem, we utilized Single-Chain Hybrid Enzyme Complexes (SCHECs), which could successfully control cellular AA metabolites to the desired PGI2 or PGE2. Our in vitro studies suggested that neurons with higher PGI2 content and lower PGE2 content exhibited survival protection and resistance to Amyloid-β-induced neurotoxicity. Further extending to an in vivo model, the hybrid of PGI2-producing transgenic mice and Alzheimer’s disease (AD) mice showed restored long-term memory. These findings suggested that the vascular prostanoids, PGI2 and PGE2, exerted significant regulatory influences on neuronal protection (by PGI2), or damage (by PGE2) in the hippocampus, and raised a concern that the wide uses of aspirin in cardiovascular diseases may exert negative impacts on neurodegenerative protection.
相似文献