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   14972篇
  免费   957篇
  国内免费   95篇
耳鼻咽喉   125篇
儿科学   500篇
妇产科学   349篇
基础医学   2169篇
口腔科学   262篇
临床医学   1327篇
内科学   3636篇
皮肤病学   457篇
神经病学   1577篇
特种医学   316篇
外科学   1346篇
综合类   43篇
一般理论   7篇
预防医学   1263篇
眼科学   279篇
药学   1143篇
中国医学   40篇
肿瘤学   1185篇
  2024年   23篇
  2023年   202篇
  2022年   516篇
  2021年   866篇
  2020年   408篇
  2019年   614篇
  2018年   677篇
  2017年   413篇
  2016年   482篇
  2015年   562篇
  2014年   708篇
  2013年   930篇
  2012年   1299篇
  2011年   1291篇
  2010年   767篇
  2009年   593篇
  2008年   921篇
  2007年   897篇
  2006年   798篇
  2005年   730篇
  2004年   596篇
  2003年   520篇
  2002年   476篇
  2001年   66篇
  2000年   40篇
  1999年   71篇
  1998年   88篇
  1997年   77篇
  1996年   42篇
  1995年   31篇
  1994年   33篇
  1993年   22篇
  1992年   27篇
  1991年   20篇
  1990年   17篇
  1989年   8篇
  1988年   10篇
  1987年   9篇
  1986年   15篇
  1985年   10篇
  1984年   9篇
  1983年   16篇
  1982年   8篇
  1981年   6篇
  1980年   12篇
  1979年   8篇
  1978年   8篇
  1977年   10篇
  1974年   12篇
  1973年   7篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Ramucirumab plus paclitaxel is considered the standard of care in the second-line treatment of gastric carcinoma (GC). The aim of this study was to evaluate plasma vascular endothelial growth factor-A (VEGF-A), VEGF-D, and circulating soluble VEGF receptor-2 (sVEGFR-2) as possible markers of resistance or response to ramucirumab administered with paclitaxel in pretreated metastatic GC patients. Plasma samples were collected at different time points (on days 1 and 15 of the first 3 cycles, at best radiologic response and at disease progression). VEGF-A, VEGF-D and sVEGFR-2 were analysed by ELISA. Correlations of biomarker baseline levels or dynamic changes with outcome measures were assessed. Progression-free survival (PFS) was the primary endpoint of the study. Forty-one patients were enrolled. VEGF-A and VEGF-D, but not sVEGFR-2, values significantly increased during treatment compared to baseline (P < 0.001). A positive correlation between VEGF-A and sVEGFR-2 at cycle 2 was found (P=0.045). At univariate analysis, higher baseline levels of VEGF-A were associated with worse OS (P=0.015). Early increase of sVEGFR-2 levels after the first treatment cycle was the only factor associated with longer PFS (6.6 vs. 3.6 months, P=0.049) and OS (18.6 vs. 5.2 months, P=0.008). Significance of sVEGFR-2 early increase was retained at multivariate analysis for OS (HR 0.32; 95% CI 0.12-0.91; P=0.032). The reported results confirmed the prognostic role of baseline VEGF-A and, with the limitations of the limited sample size and the lack of a control arm, suggested that the early increase of sVEGFR-2 after 1 cycle of treatment could be a potential predictive biomarker of benefit from second-line ramucirumab plus paclitaxel in GC.  相似文献   
102.
103.
Renal impairment (RI) is common in patients with multiple myeloma (MM) and new therapies that can improve renal function are needed. The phase III IKEMA study (clinicaltrials gov. Identifier: NCT03275285) investigated isatuximab (Isa) with carfilzomib and dexamethasone (Kd) versus Kd in relapsed MM. This subgroup analysis examined results from patients with RI, defined as estimated glomerular filtration rate <60 mL/min/1.73 m². Addition of Isa prolonged progression-free survival (PFS) in patients with RI (hazard ratio: 0.27; 95% confidence interval [CI]: 0.11–0.66; median PFS not reached for Isa-Kd versus 13.4 months for Kd [20.8-month follow-up]). Complete renal responses occurred more frequently with Isa-Kd (52.0%) versus Kd (30.8%) and were durable in 32.0% versus 7.7% of patients, respectively. Treatment exposure was longer with Isa-Kd, with median number of started cycles and median duration of exposure of 20 versus 9 cycles and 81.0 versus 35.7 weeks for Isa-Kd versus Kd, respectively. Among patients with RI, the incidence of patients with grade ≥3 treatment-emergent adverse events was similar between the two arms (79.1% in Isa-Kd vs. 77.8% in Kd). In summary, the addition of Isa to Kd improved clinical outcomes with a manageable safety profile in patients with RI, consistent with the benefit observed in the overall IKEMA study population.  相似文献   
104.
105.
Despite the existence of an effective live-attenuated vaccine, measles can appear in vaccinated individuals. We investigated breakthrough measles cases identified during our surveillance activities within the measles/rubella surveillance network (MoRoNet) in Milan and surrounding areas (Northern Italy). Between 2017 and 2021, we confirmed measles virus (genotypes B3 or D8) infections in 653 patients and 51 of these (7.8%) were vaccinees. Among vaccinated individuals whose serum was available, a secondary failure was evidenced in 69.4% (25/36) of cases while 11 patients (30.6%) were non-responders. Non-responders were more frequently hospitalized and had significantly lower Ct values in both respiratory and urine samples. Median age and time since the last immunization were similar in the two groups. Importantly, we identified onward transmissions from vaccine failure cases. Vaccinees were involved in 20 outbreaks, in 10 of them they were able to transmit the virus, and in 8 of them, they were the index case. Comparing viral hemagglutinin sequences from vaccinated and non-vaccinated subjects did not show a specific mutation pattern. These results suggest that vaccination failure was likely due to the poor immune response of single individuals and highlights the importance of identifying breakthrough cases and characterizing their clinical and virologic profiles.  相似文献   
106.
Bacteriophage JC1 is a Podoviridae phage with a C1 morphotype, isolated on host strain Burkholderia cenocepacia Van1. Phage JC1 is capable of infecting an expansive range of Burkholderia cepacia complex (Bcc) species. The JC1 genome exhibits significant similarity and synteny to Bcep22-like phages and to many Ralstonia phages. The genome of JC1 was determined to be 61,182 bp in length with a 65.4% G + C content and is predicted to encode 76 proteins and 1 tRNA gene. Unlike the other Lessieviruses, JC1 encodes a putative helicase gene in its replication module, and it is in a unique organization not found in previously analyzed phages. The JC1 genome also harbours 3 interesting moron genes, that encode a carbon storage regulator (CsrA), an N-acetyltransferase, and a phosphoadenosine phosphosulfate (PAPS) reductase. JC1 can stably lysogenize its host Van1 and integrates into the 5′ end of the gene rimO. This is the first account of stable integration identified for Bcep22-like phages. JC1 has a higher global virulence index at 37 °C than at 30 °C (0.8 and 0.21, respectively); however, infection efficiency and lysogen stability are not affected by a change in temperature, and no observable temperature-sensitive switch between lytic and lysogenic lifestyle appears to exist. Although JC1 can stably lysogenize its host, it possesses some desirable characteristics for use in phage therapy. Phage JC1 has a broad host range and requires the inner core of the bacterial LPS for infection. Bacteria that mutate to evade infection by JC1 may develop a fitness disadvantage as seen in previously characterized LPS mutants lacking inner core.  相似文献   
107.
The Smith-Watson-Topper parameter (SWT) in its original form was designed to estimate the fatigue life of metal materials in a uniaxial load state (tension–compression) in the range up to fatigue crack initiation, with non-zero mean values. This parameter is based on the analysis of both stress and strain. Therefore, the stress–strain criterion is the focus, rather than the energy criterion. This paper presents the original SWT model and its numerous modifications. The first part presents different versions of this parameter defined by the normal parameters. Then, it presents versions defined through the tangent parameter and the most promising parameter defined through the tangent and normal parameters. It was noted that the final form of the equivalent value is defined either by stress or by an energy parameter. Therefore, the possible characteristics from which the fatigue life can be determined are also presented.  相似文献   
108.
BackgroundAuditory verbal hallucinations (AVH) commonly occur in the context of borderline personality disorder (BPD) yet remain poorly understood. AVH are often perceived by patients with BPD as originating from inside the head and hence viewed clinically as “pseudohallucinations,” but they nevertheless have a detrimental impact on well-being.MethodsThe current study characterized perceptual, subjective, and neural expressions of AVH by using an auditory detection task, experience sampling and questionnaires, and functional neuroimaging, respectively.ResultsPerceptually, reported AVH correlated with a bias for reporting the presence of a voice in white noise. Subjectively, questionnaire measures indicated that AVH were significantly distressing and persecutory. In addition, AVH intensity, but not perceived origin (i.e., inside vs outside the head), was associated with greater concurrent anxiety. Neurally, fMRI of BPD participants demonstrated that, relative to imagining or listening to voices, periods of reported AVH induced greater blood oxygenation level–dependent activity in anterior cingulate and bilateral temporal cortices (regional substrates for language processing). AVH symptom severity was associated with weaker functional connectivity between anterior cingulate and bilateral insular cortices.ConclusionIn summary, our results indicate that AVH in participants with BPD are (1) underpinned by aberrant perceptual-cognitive mechanisms for signal detection, (2) experienced subjectively as persecutory and distressing, and (3) associated with distinct patterns of neural activity that inform proximal mechanistic understanding. Our findings are like analogous observations in patients with schizophrenia and validate the clinical significance of the AVH experience in BPD, often dismissed as “pseudohallucinations.” These highlight a need to reconsider this experience as a treatment priority.  相似文献   
109.
Gemma  G.  Kenter  Marij  J.P.  Welters  Rob  P.M.  Valentijn  梁伟 《中国处方药》2009,(12):61-61
背景及目的:最近,关于叶酸的安全性引起了广泛的关注,尤其是其与肿瘤风险的关系。本研究是通过两项随机对照试验评价叶酸和维生素B治疗对肿瘤发生率和全因死亡率的影响。  相似文献   
110.
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