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   8813篇
  免费   702篇
  国内免费   14篇
耳鼻咽喉   92篇
儿科学   289篇
妇产科学   166篇
基础医学   1326篇
口腔科学   132篇
临床医学   1111篇
内科学   1680篇
皮肤病学   173篇
神经病学   858篇
特种医学   171篇
外科学   847篇
综合类   51篇
一般理论   8篇
预防医学   1421篇
眼科学   111篇
药学   516篇
中国医学   4篇
肿瘤学   573篇
  2024年   14篇
  2023年   119篇
  2022年   169篇
  2021年   310篇
  2020年   217篇
  2019年   326篇
  2018年   301篇
  2017年   282篇
  2016年   293篇
  2015年   321篇
  2014年   399篇
  2013年   529篇
  2012年   825篇
  2011年   811篇
  2010年   432篇
  2009年   404篇
  2008年   654篇
  2007年   625篇
  2006年   568篇
  2005年   515篇
  2004年   414篇
  2003年   343篇
  2002年   292篇
  2001年   34篇
  2000年   32篇
  1999年   38篇
  1998年   31篇
  1997年   32篇
  1996年   31篇
  1995年   30篇
  1994年   29篇
  1993年   22篇
  1992年   9篇
  1991年   10篇
  1990年   5篇
  1989年   5篇
  1988年   5篇
  1987年   4篇
  1986年   5篇
  1985年   6篇
  1984年   1篇
  1983年   11篇
  1982年   10篇
  1981年   6篇
  1980年   5篇
  1978年   2篇
  1977年   1篇
  1976年   1篇
  1928年   1篇
排序方式: 共有9529条查询结果,搜索用时 203 毫秒
61.
Errors in timed choice tasks typically produce an error-related negativity (ERN) in the event-related potential (ERP). The error specificity of the ERN has been challenged by studies showing a correct response negativity (CRN). Forty-five participants engaged in a flanker task in which both compatibility between flankers and target and the probability of compatible flankers were manipulated. Correct responses elicited a CRN, the amplitude of which increased with the degree of mismatch between the presence of conflict and conflict probability, even on low-conflict (compatible) trials. The fronto-central N2 component was larger on high-conflict (incompatible) correct response trials. However, in contrast to some recent accounts, this N2 was largest for highly probable stimuli. These findings suggest revision to models of the effects of conflict on response-related negativity to account for strategic adjustments made in preparation for the response.  相似文献   
62.
The epidermal growth factor receptor (EGFR) regulates multiple patterning events in Drosophila limb development, but its role in vertebrate limb morphogenesis has received little attention. The EGFR and several of its ligands are expressed in developing vertebrate limbs in manners consistent with potential patterning roles. To gain insight into functions of EGFR signaling in vertebrate limb development, we expressed a constitutively active EGFR in developing chick limbs in ovo. Expression of activated EGFR causes pre- and postaxial polydactyly, including mirror-image-type digit duplication, likely due to induction of ectopic expression and/or modulation of genes involved in anterior-posterior (AP) patterning such as Sonic hedgehog (Shh), dHand, Patched (Ptc), Gli3, Hoxd13, Hoxd11, bone morphogenetic protein 2 (Bmp2), Gremlin, and FGF4. Activation of EGFR signaling dorsalizes the limb and alters expression of the dorsal-ventral (DV) patterning genes Wnt7a, Lmx, and En1. Ectopic and/or extended FGF8 expressing apical ectodermal ridges (AERs) are also seen. Interdigital regression is inhibited and the digits fail to separate, leading to syndactyly, likely due to antiapoptotic and pro-proliferative effects of activated EGFR signaling on limb mesoderm, and/or attenuation of interdigital Bmp4 expression. These findings suggest potential roles for EGFR signaling in AP and DV patterning, AER formation, and cell survival during limb morphogenesis.  相似文献   
63.
Summary Monoclonal antibodies (MCAbs) were used to dissect the antigenic sites of the surface glycoproteins of the prototype cell-adapted Wyoming strain of equine infectious anemia virus (EIAV) Serologic reactivities of these MCAbs were determined by ELISA, additive ELISA, competitive ELISA, and Western blot assays. The results indicated that antigenic reactivity of gp90 was localized on at least four distinct epitopes, two of which were important in neutralization. Our studies also revealed that these epitopes were localized on overlapping antigenic sites on gp90. On the other hand, only two distinct non-overlapping epitopes were identified on gp45. Competitive binding studies of neutralizing MCAbs and reference EIA-positive horse serum delineated the presence of a neutralization domain on gp90 that appears to be immunodominant both in naturally infected horses and in mice immunized with EIAV. Limited proteolytic fragmentation of the gp90 component of several serologically distinct EIAV isolates produced common 12K immunoreactive fragments that contained a conserved epitope. These results indicate the occurrence of conserved antigenic regions on EIAV glycoproteins as well as a neutralization domain on gp90, which can be used as potential targets for vaccine development.  相似文献   
64.
Dengue control approaches are best informed by granular spatial epidemiology of these viruses, yet reconstruction of inter- and intra-household transmissions is limited when analyzing case count, serologic, or genomic consensus sequence data. To determine viral spread on a finer spatial scale, we extended phylogenomic discrete trait analyses to reconstructions of house-to-house transmissions within a prospective cluster study in Kamphaeng Phet, Thailand. For additional resolution and transmission confirmation, we mapped dengue intra-host single nucleotide variants on the taxa of these time-scaled phylogenies. This approach confirmed 19 household transmissions and revealed that dengue disperses an average of 70 m per day between households in these communities. We describe an evolutionary biology framework for the resolution of dengue transmissions that cannot be differentiated based on epidemiologic and consensus genome data alone. This framework can be used as a public health tool to inform control approaches and enable precise tracing of dengue transmissions.  相似文献   
65.
66.
AimTo evaluate the impact of the implementation of a best practice infection prevention and control bundle on healthcare associated burn wound infections in a paediatric burns unit.BackgroundBurn patients are vulnerable to infection. For this patient population, infection is associated with increased morbidity and mortality, thereby representing a significant challenge for burns clinicians who care for them.MethodsAn interrupted time series was used to compare healthcare associated burn wound infections in paediatric burn patients before and after implementation of an infection prevention and control bundle. Prospective surveillance of healthcare associated burn wound infections was conducted from 2012 to 2014. Other potential healthcare associated infection rates were also reviewed over the study period, including urinary tract infections, pneumonia, upper respiratory tract infections and sepsis. An infection prevention and control bundle developed in collaboration between the paediatric burn unit and infection control clinicians was implemented in 2013 in addition to previous standard practice.ResultsDuring the study period a total of 626 patients were admitted to the paediatric burns unit. Healthcare associated burn wound infections reduced from 34 in 2012 to 0 in 2014 following the implementation of the infection prevention and control bundle. Pneumonia and sepsis also reduced to 0 in 2013 and 2014, however one upper respiratory tract infection occurred in 2013 and urinary tract infections persisted in 2013.ConclusionThe implementation of an infection prevention and control bundle was effective in reducing healthcare associated burn wound infections, pneumonia and sepsis within our paediatric burns unit. Urinary tract infections remain a challenge for future improvement.  相似文献   
67.
Neurosurgical Review - Exposure of the anterior skull base is challenging due to strategic structures. The interhemispheric approach (IHA) has turned out to be a feasible technique. We report our...  相似文献   
68.
Strict isolation of vulnerable individuals has been a strategy implemented by authorities to protect people from COVID-19. Our objective was to investigate health-related quality of life (HRQoL), uncertainty and coping behaviours in solid organ transplant (SOT) recipients during the COVID-19 pandemic. A cross-sectional survey of adult SOT recipients undergoing follow-up at our institution was performed. Perceived health status, uncertainty and coping strategies were assessed using the EQ-5D-5L, Short-form Mishel Uncertainty in Illness Scale (SF-MUIS) and Brief Cope, respectively. Interactions with COVID-19 risk perception, access to health care, demographic and clinical variables were assessed. The survey was completed by 826 of 3839 (21.5%) invited participants. Overall, low levels of uncertainty in illness were reported, and acceptance was the major coping strategy (92%). Coping by acceptance, feeling protected, self-perceived susceptibility to COVID-19 were associated with lower levels of uncertainty. Health status index scores were significantly lower for those with mental health illness, compromised access to health care, a perceived high risk of severe COVID-19 infection and higher levels of uncertainty. A history of mental health illness, risk perceptions, restricted healthcare access, uncertainty and coping strategies was associated with poorer HRQoL in SOT recipients during strict isolation. These findings may allow identification of strategies to improve HRQoL in SOT recipients during the pandemic.  相似文献   
69.
BackgroundHow malignant insulinomas present relative to benign insulinomas is unknown.MethodsA single-institution retrospective study identified patients with insulinoma. Malignancy was defined by distant metastases, positive lymph node(s), T stage of 4, direct invasion into surrounding peripancreatic tissue, or presence of lymphovascular invasion. Wilcoxon Rank Sum tests and Kaplan-Meier analysis were used.ResultsA total of 311 patients were identified: 51 malignant and 260 benign. Patients with malignant insulinoma presented with higher levels of insulin, proinsulin, and c-peptide. Malignant lesions were larger: 4.2 ± 3.2 vs 1.8 ± 0.8 cm in benign lesions, p < 0.01. Overall survival at 5 years was 66.8% vs 95.4% for malignant and benign insulinoma respectively, p < 0.01.ConclusionsLarger size of insulinoma and increased serum β-cell polypeptide concentrations were associated with malignancy. Malignant insulinoma has poorer survival. Further work-up to rule out malignancy may be indicated for larger pancreatic lesions and for patients with higher pre-operative insulin and pro-insulin.  相似文献   
70.
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