首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1993篇
  免费   108篇
  国内免费   8篇
耳鼻咽喉   38篇
儿科学   76篇
妇产科学   130篇
基础医学   283篇
口腔科学   108篇
临床医学   145篇
内科学   296篇
皮肤病学   26篇
神经病学   209篇
特种医学   81篇
外科学   248篇
综合类   21篇
一般理论   1篇
预防医学   113篇
眼科学   11篇
药学   194篇
中国医学   7篇
肿瘤学   122篇
  2023年   17篇
  2022年   28篇
  2021年   63篇
  2020年   31篇
  2019年   51篇
  2018年   48篇
  2017年   52篇
  2016年   37篇
  2015年   47篇
  2014年   62篇
  2013年   73篇
  2012年   136篇
  2011年   156篇
  2010年   71篇
  2009年   63篇
  2008年   114篇
  2007年   97篇
  2006年   102篇
  2005年   108篇
  2004年   98篇
  2003年   72篇
  2002年   78篇
  2001年   63篇
  2000年   58篇
  1999年   70篇
  1998年   21篇
  1997年   18篇
  1995年   9篇
  1992年   21篇
  1991年   20篇
  1990年   19篇
  1989年   20篇
  1988年   12篇
  1987年   16篇
  1986年   18篇
  1985年   8篇
  1984年   7篇
  1983年   10篇
  1982年   9篇
  1981年   5篇
  1979年   5篇
  1978年   7篇
  1976年   6篇
  1975年   5篇
  1973年   5篇
  1972年   11篇
  1971年   5篇
  1970年   8篇
  1969年   10篇
  1968年   9篇
排序方式: 共有2109条查询结果,搜索用时 31 毫秒
81.
Animals can use a range of strategies to recall important locations. These include simple stimulus–response strategies and more complex spatial (place) strategies, which are thought to have distinct neural substrates. The hippocampus—and NMDA receptor activation therein—is considered to be crucial for spatial, but not response strategies. The medial prefrontal cortex has also been implicated in memory retrieval; however, evidence concerning its specific role is equivocal. Both hippocampal and prefrontal regions have been associated with flexible behavioural responding (e.g. when task demands change). Here, we investigated the use of spatial and non‐spatial strategies in the Morris water maze and their associated brain areas in rats using immediate early gene (IEG) imaging of Zif268 and c‐Fos. Specifically, we charted the involvement of hippocampal and prefrontal subregions during retrieval of spatial and non‐spatial memories. Behavioural flexibility was also examined using intact and partial cue configurations during recall. Results indicated that regions of both the hippocampus (area CA3) and prefrontal cortex (anterior cingulate cortex) were preferentially engaged in spatial memory recall compared to response learning. In addition, both spatial and non‐spatial memories were dependent on NMDA receptor activation. MK801 impaired recall performance across all groups and reduced IEG activation across hippocampal and prefrontal regions. Finally, IEG results revealed divergent patterns of Zif268 and c‐Fos activity and support the suggestion that Zif268 plays a functional role in the recall of long‐term memories.  相似文献   
82.
Consolidation treatment in acute myeloid leukemia (AML) patients achieving complete remission (CR) is warranted. High-dose cytarabine (HDAC) is considered first choice in favorable risk and an option in intermediate-risk AML. However, its optimal dose and schedule, as well as the benefit of additional chemotherapy agents remain controversial. Herein, we report on the long-term outcome of consecutive unselected AML patients treated with repeated courses of HDAC, with the addition of idarubicin, followed by autologous peripheral blood stem cell (PBSC) support, in order to limit toxicity, according to Northern Italy Leukemia Group (NILG) AML-01/00 study (EUDRACT number 00400673). Among 338 patients consecutively diagnosed from 2001 to 2017 at our center, 148 with high-risk AML (adverse cytogenetic, isolated FLT3-internal tandem duplication mutation, refractory to first induction) were addressed to allogeneic stem cell transplant. All other cases, 186 patients (55%), median age 53 (range 19–75), were considered standard-risk and received the NILG AML-01/00 program. After achieving CR, patients were mobilized with cytarabine 8 g/sqm to collect autologous CD34+-PBSC and received three consolidation cycles with HDAC (20 g/sqm) plus idarubicin (20 mg/sqm) per cycle, followed by reinfusion of limited doses of CD34+ PBSC (1-2x106/kg). The program was completed by 160 (86%) patients. Toxicity was acceptable. Neutrophils recovered a median of 10 days. Treatment-related mortality was 3/160 (1.8%). After a median follow-up of 66.4 months, overall survival (OS) and relapse-free survival (RFS) at 5-years were 61.4% and 52.4%, respectively. Twenty-eight selected patients aged >65 had similar outcomes. According to European leukemia net-2010 classification, the OS and RFS at 5-years were 76.4% and 65% in favorable risk, without differences between molecular subgroups, 52.3% and 47.2% in Intermediate-I, 45.2% and 36.5% in Intermediate-II risk patients, respectively. In conclusion, consolidation including repeated courses of high dose cytarabine and idarubicin, with limited PBSC support, proved feasible and very effective in nonhigh risk patients. The incorporation of novel agents in its backbone may be tested to further improve patient's prognosis.  相似文献   
83.
Among patients with advanced-stage classical Hodgkin lymphoma (cHL) receiving ABVD chemotherapy, PET performed after the first two treatment cycles (PET-2) has prognostic value. However, 15% of patients with a negative PET-2 will experience treatment failure. Here we prospectively evaluated serum thymus and activation-regulated chemokine (TARC) levels, to improve risk assessment in patients treated according to HD0607 PET-driven trial (#NCT00795613). In 266 patients with available serum samples, who have agreed to participate in a sub-study for assessment of the role of TARC monitoring, serum TARC levels were measured at baseline and at time of PET-2 by commercially available ELISA test kits. The primary end-point was to evaluate the association between TARC after 2 ABVD cycles and PFS. Median TARC-2 values were significantly higher in PET-2-positive patients compared to PET-2-negative patients (P = .001), and in patients with treatment failure compared to those in continuous CR (P = .01). The 4-year PFS significantly differed between patients with TARC-2 >800 pg/mL vs ≤800 pg/mL (64% vs 86%, P = .0001). Moreover, among PET-2-negative patients, elevated TARC-2 identified those with a worse prognosis (74% vs 89%; P = .01). In multivariable analysis, TARC-2 >800 pg/mL was a significant independent predictor of PFS in the whole study population (HR 2.39, P = .004) and among the PET-2-negative patients (HR 2.49, P = .02). In conclusion, our results indicate that TARC-2 serum levels above 800 pg/mL suggest the need for a stringent follow-up in PET-2-negative patients, and the evaluation of new drugs in PET-2-positive, who will likely fail to respond to intensification with escalated BEACOPP.  相似文献   
84.
Increased oxidative stress has been implicated in the pathogenesis of a number of cardiovascular diseases. Recent findings suggest that myeloperoxidase (MPO) may play a key role in the initiation and maintenance of chronic heart failure (CHF) by contributing to the depletion of the intracellular reservoir of nitric oxide (NO). NO consumption through MPO activity may lead to protein chlorination or nitration, leading to tissue damage. Primary cultures of human endocardial endothelial cells (EEC) obtained at heart transplantation of patients with CHF and human umbilical vein endothelial cells (HUVEC) were subjected to oxidative stress by incubation with hydrogen peroxide at non lethal (60 μM) dose for different exposure times (3 and 6 h). Treated and control cells were tested by immunohistochemistry and RT-PCR for MPO and 3-chlorotyrosine expression. Both endothelial cell types expressed myeloperoxidase following oxidative stress, with higher levels in EEC. Moreover, 3-chlorotyrosine accumulation in treated cells alone indicated the presence of MPO-derived hypochlorous acid. Immunohistochemistry on sections from post-infarcted heart confirmed in vivo the endothelial positivity to MPO, 3-chlorotyrosine and, to a minor extent, nitrotyrosine. Immunohistochemical observations were confirmed by detection of MPO mRNA in both stimulated EEC and HUVEC cells. This study demonstrates for the first time that EEC can express MPO after oxidative stress, both in vitro and in vivo, followed by accumulation of 3-chlorotyrosine, an end product of oxidative stress. Deregulation of endothelial functions may contribute to the development of a number of cardiovascular diseases, including CHF. The results also highlight the notion that endothelium is not only a target but also a key player in oxidative-driven cardiovascular stress. Electronic supplementary material  The online version of this article (doi: ) contains supplementary material, which is available to authorized users. G. La Rocca and A. Di Stefano contributed equally to the current work. Returned for 1. Revision: 7 January 2008 1. Revision received: 18 June 2008 Returned for 2. Revision: 17 July 2008 2. Revision received: 17 October 2008  相似文献   
85.
Reading is an expert visual and ocular motor function, learned mainly in a single orientation. Characterizing the features of this expertise can be accomplished by contrasts between reading of normal and inverted text, in which perceptual but not linguistic factors are altered. Our goal was to examine this inversion effect in healthy subjects reading text, to derive behavioral and ocular motor markers of perceptual expertise in reading, and to study these parameters before and after training with inverted reading. Seven subjects engaged in a 10-week program of 30 half-hour sessions of reading inverted text. Before and after training, we assessed reading of upright and inverted single words for response time and word-length effects, as well as reading of paragraphs for time required, accuracy, and ocular motor parameters. Before training, inverted reading was characterized by long reading times and large word-length effects, with eye movements showing more and longer fixations, more and smaller forward saccades, and more regressive saccades. Training partially reversed many of these effects in single word and text reading, with the best gains occurring in reading aloud time and proportion of regressive saccades and the least change in forward saccade amplitude. We conclude that reading speed and ocular motor parameters can serve as markers of perceptual expertise during reading and that training with inverted text over 10 weeks results in significant gains of reading expertise in this unfamiliar orientation. This approach may be useful in the rehabilitation of patients with hemianopic dyslexia.  相似文献   
86.
87.
OBJECTIVES: To estimate the combined screening performance of first and early second trimester prenatal serum markers for Down syndrome, in screening for the development of preeclampsia, and analyze the correlation among marker levels, week of onset, and severity of the disease. METHODS: A retrospective cohort study was carried out on 32 women with preeclampsia and 3044 controls. Serum samples from these pregnancies were assayed for pregnancy-associated plasma protein-A (PAPP-A), alpha-fetoprotein (AFP), unconjugated estriol (uE3), human chorionic gonadotrophin (hCG), and inhibin-A. A likelihood ratio and the odds of being affected given a positive result (OAPR) of various combinations of markers were calculated and receiver operating characteristic (ROC) curves analysis was performed. RESULTS: In the pregnancies that subsequently developed preeclampsia, first trimester PAPP-A concentration was significantly lower and concentrations of early second trimester inhibin-A and hCG significantly elevated. Levels of early second trimester uE3 and AFP were not significantly altered. We also found that inhibin-A correlates with both onset of the disease and the severity. CONCLUSION: Down syndrome biochemical markers levels are altered in those patients who subsequently developed preeclampsia and may be a useful screening test for preeclampsia. Inhibin-A is the most predictive marker and correlates with the severity of subsequent preeclampsia and inversely with the week of occurrence of preeclampsia.  相似文献   
88.
89.
The guiding hypothesis for this work is that in severe intrauterine growth-restricted (IUGR) fetuses, the time from ductus venosus (DV) reversed flow (RF) appearance to intrauterine fetal demise (IUFD) or nonreassuring fetal testing is variable. As such, there must be a transitional phase between the presence of end-diastolic forward flow (FF) and absent or reversed end-diastolic flow (A/REDF). Ductus venosus Doppler was serially studied in 19 IUGR fetuses (estimated fetal weight < 10th percentile and umbilical artery pulsatility index > 95th percentile) from diagnosis until demise or delivery occurring for nonreassuring fetal testing. Ductus venosus waveforms were assessed qualitatively: forward flow versus absent or reversed flow in diastole. Two sets of at least 30 consecutive ductus venosus waveforms were obtained at each examination. If the waveforms differed between the two sets, they were defined as alternating. Cord arterial pH and base excess (BE) were obtained at birth. In 14 cases, DVRF occurred intermittently between periods of FF during the same clinical visit. Intermittent DVRF was present from 2 to 57 days (median, 13 days) and became continuous from 1 to 23 days (median, 7 days) before the occurrence of delivery for nonreassuring fetal testing or fetal demise. One fetus had an abnormal arterial pH (< 7.0) and one had an abnormal BE (< -12). These data show that (1) there is a transitional phase in which DV alternates FF and A/RF before RF becomes persistent; (2) the time from the appearance of DVRF to delivery or IUFD is variable, and (3) not all very preterm IUGR fetuses with continuous DVRF are acidemic. Because of these findings, the decision of delivery regarding early severe IUGR fetuses should be individualized, and the DVRF Doppler information has to be integrated with other antenatal fetal parameters.  相似文献   
90.
We report here an uncommon case of deep infection by Torulopsis incospicua, associated with multibacterial sepsis and complicated by several mycotic aneurysms of hepatic artery, liver graft necrosis, and hepatic acute failure in a liver orthotopic transplant recipient. Two successive emergency liver transplants were needed, but fast relapses of infection and mycotic aneurysms were experienced. The patient died soon after the third liver transplant; disseminated mycosis was demonstrated by post mortem examination. In conclusion, fungal infection should be considered in cases of spontaneous hepatic artery rupture.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号