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   2949篇
  免费   198篇
  国内免费   5篇
耳鼻咽喉   12篇
儿科学   84篇
妇产科学   78篇
基础医学   370篇
口腔科学   36篇
临床医学   327篇
内科学   639篇
皮肤病学   95篇
神经病学   426篇
特种医学   48篇
外科学   206篇
综合类   29篇
预防医学   131篇
眼科学   404篇
药学   132篇
肿瘤学   135篇
  2022年   23篇
  2021年   33篇
  2020年   29篇
  2019年   31篇
  2018年   32篇
  2017年   26篇
  2016年   46篇
  2015年   58篇
  2014年   50篇
  2013年   113篇
  2012年   149篇
  2011年   136篇
  2010年   74篇
  2009年   68篇
  2008年   133篇
  2007年   149篇
  2006年   135篇
  2005年   122篇
  2004年   130篇
  2003年   127篇
  2002年   87篇
  2001年   89篇
  2000年   97篇
  1999年   93篇
  1998年   36篇
  1997年   24篇
  1996年   26篇
  1995年   33篇
  1994年   21篇
  1992年   55篇
  1991年   66篇
  1990年   64篇
  1989年   62篇
  1988年   55篇
  1987年   53篇
  1986年   51篇
  1985年   57篇
  1984年   46篇
  1983年   24篇
  1982年   28篇
  1981年   25篇
  1980年   24篇
  1979年   57篇
  1978年   33篇
  1977年   22篇
  1975年   33篇
  1974年   26篇
  1973年   28篇
  1970年   20篇
  1966年   19篇
排序方式: 共有3152条查询结果,搜索用时 15 毫秒
81.
Zusammenfassung Die Diagnose eines flottierenden Thrombus in einem offenen Foramen ovale wird selten gestellt. Wir berichten über einen Patienten, bei dem aufgrund des dringenden Verdachtes auf eine Pulmonalembolie eine trans?sophageale Echokardiographie (TEE) durchgeführt wurde. Mit Hilfe der TEE konnte der Verdacht der Pulmonalembolie erh?rtet werden. Als überraschungsbefund fand sich jedoch im rechten und linken Vorhof ein langer, wurmf?rmiger, sehr mobiler Thrombus, der im offenen Foramen ovale eingekeilt war. Der Patient wurde aufgrund dieser Diagnose unverzüglich einem chirurgischem Eingriff unterzogen, wobei sich der TEE-Befund best?tigte und ein 19 cm langer Thrombus entfernt wurde. Mit Hilfe der TEE konnte der Riesenthrombus erkannt und einer entsprechenden Therapie zugeführt werden, wodurch Komplikationen, wie das Auftreten einer neuerlichen Pulmonalembolie oder einer paradoxen Embolie, verhindert werden konnten. Eingegangen: 10. August 1998 Akzeptiert: 12. August 1998  相似文献   
82.
We have previously shown that the synthetic peptide pGlu-Glu-Asp-Cys-Lys (pEEDCK monomer) inhibits the cytostatic drug-induced proliferation of hematopoietic stem cells CFU-S. Keeping CFU-S quiescent by pEEDCK treatment renders them insensitive to cycle-specific cytostatic drugs and leads to reduced toxicity. Here we show that pEEDCK application during repeated (twice) administration of clinically relevant (nonlethal) 1-beta-D-arabinofuranosylcytosine (Ara-C) doses reduced the percentage of CFU-S in S-phase from 60%-70% to 25%-30% and led to a sustained stem cell number in the bone marrow (BM), whereas unprotected mice had lost about 75% of their CFU-S population. Owing to its cysteine content, the pEEDCK monomer is easily oxidized. The resulting dimer (pEEDCK)2 is a potent stimulator of hematopoiesis. As we show, it can be used for postchemotherapy acceleration of hematologic recovery, similar to the use of recombinant hematopoietic growth factors. A single injection of 30 micrograms/kg pEEDCK monomer to mice 2 hours before the second Ara-C injection retarded onset of neutropenia (by 2 to 3 days) and improved recovery after depression. The quantitative degree of neutropenia was not changed. Postchemotherapy (Ara-C administered twice, followed by N-mustard) infusion of the stimulatory (pEEDCK)2 dimer (1.4 micrograms/kg/d) produced a 4.6-fold increase of progenitor levels (6.7 CFU-GM/1,000 BM cells v 1.45 CFU-GM/1,000 in normal mice) 2 days after the end of the cytostatic treatment when CFU-GM were not detectable in unprotected mice. This increase was followed after several days by strongly elevated granulocyte counts, which remained high for approximately 1 week. Up to 75% of the peripheral leukocytes were mature polymorphonuclear leukocytes (PMN) during this phase. Ara-C (twice) and monomer treatment as above followed by dimer infusion resulted in the complete protection of hematopoiesis. Mice treated with the protective pEEDCK monomer plus stimulatory dimer did not develop the leukocyte depression noted in unprotected animals. The inhibitory monomer appears to keep the stem cell population numerically and qualitatively intact, thus providing optimum target cell conditions for the subsequent stimulator (dimer) treatment. Our results show that the hemoregulatory peptide monomer and dimer can be used for improving the hematologic status of mice treated with clinically relevant doses of cytostatic drugs (antimetabolite and alkylating, alone and in combination). Combining both peptides can prevent occurrence of neutropenia completely. Both peptides can be obtained easily by chemical synthesis and are also active on human cells. They are thus highly promising candidates for application as multilevel hemoprotectors in cancer chemotherapy.  相似文献   
83.
84.
Aims/hypothesis Progression to type 1 diabetes is associated with intramolecular epitope spreading to disease-specific antibody epitopes located in the middle region of glutamic acid decarboxylase 65 (GAD65).Methods The relationship between intramolecular epitope spreading of autoantibodies specific to GAD65 in relation to the risk of developing type 1 diabetes was tested in 22 high-risk individuals and 38 low-risk individuals. We determined the conformational epitopes in this longitudinal study by means of competition experiments using recombinant Fab of four GAD65-specific monoclonal antibodies.Results Sera from high-risk children in the preclinical stage recognise a specific combination of GAD65 antibody epitopes located in the middle and the C-terminus of GAD65. High risk of progressing to disease is associated with the emergence of antibodies specific for conformational epitopes at the N-terminus and the middle region. Binding to already established antibody epitopes located in the middle and at the N-terminus increases and shows a significant relation (p=0.005) with HLA, which confers risk of developing diabetes.Conclusions/interpretation In type 1 diabetes, GAD65 antibodies are initially generated against the middle and C-terminal regions of GAD65. In genetically predisposed subjects the autoimmune response may then undergo intramolecular epitope spreading towards epitopes on the N-terminus and further epitopes located in the middle. These findings clearly demonstrate that the GAD65 autoantibody response in the preclinical stage of type 1 diabetes is dynamic and related to the HLA genotypes that confer risk of diabetes. GAD65-specific Fab should prove useful in predicting progression from islet autoimmunity to clinical onset of type 1 diabetes.  相似文献   
85.
Understanding how and where in the brain sentence-level meaning is constructed from words presents a major scientific challenge. Recent advances have begun to explain brain activation elicited by sentences using vector models of word meaning derived from patterns of word co-occurrence in text corpora. These studies have helped map out semantic representation across a distributed brain network spanning temporal, parietal, and frontal cortex. However, it remains unclear whether activation patterns within regions reflect unified representations of sentence-level meaning, as opposed to superpositions of context-independent component words. This is because models have typically represented sentences as “bags-of-words” that neglect sentence-level structure. To address this issue, we interrogated fMRI activation elicited as 240 sentences were read by 14 participants (9 female, 5 male), using sentences encoded by a recurrent deep artificial neural-network trained on a sentence inference task (InferSent). Recurrent connections and nonlinear filters enable InferSent to transform sequences of word vectors into unified “propositional” sentence representations suitable for evaluating intersentence entailment relations. Using voxelwise encoding modeling, we demonstrate that InferSent predicts elements of fMRI activation that cannot be predicted by bag-of-words models and sentence models using grammatical rules to assemble word vectors. This effect occurs throughout a distributed network, which suggests that propositional sentence-level meaning is represented within and across multiple cortical regions rather than at any single site. In follow-up analyses, we place results in the context of other deep network approaches (ELMo and BERT) and estimate the degree of unpredicted neural signal using an “experiential” semantic model and cross-participant encoding.SIGNIFICANCE STATEMENT A modern-day scientific challenge is to understand how the human brain transforms word sequences into representations of sentence meaning. A recent approach, emerging from advances in functional neuroimaging, big data, and machine learning, is to computationally model meaning, and use models to predict brain activity. Such models have helped map a cortical semantic information-processing network. However, how unified sentence-level information, as opposed to word-level units, is represented throughout this network remains unclear. This is because models have typically represented sentences as unordered “bags-of-words.” Using a deep artificial neural network that recurrently and nonlinearly combines word representations into unified propositional sentence representations, we provide evidence that sentence-level information is encoded throughout a cortical network, rather than in a single region.  相似文献   
86.
BackgroundAlpha-gal syndrome (AGS) is an emerging immunoglobulin E (IgE)–mediated allergy to galactose-alpha-1,3-galactose (alpha-gal). The geographic distribution and burden of AGS in the United States are unknown.ObjectiveTo characterize alpha-gal IgE testing patterns and describe the trends and distribution from 2010 to 2018 in the United States.MethodsThis retrospective analysis included all persons tested for alpha-gal IgE antibodies by Viracor-IBT Laboratories (Lee’s Summit, Missouri), the primary site of testing in the United States. Data included age and sex of person tested, specimen state of origin, collection date, and result value; persons with at least 1 positive test result (≥0.1 kU/L) were compared with negatives. Proportions tested and with positive test results were calculated using the US Census population estimates.ResultsOverall, 122,068 specimens from 105,674 persons were tested for alpha-gal IgE during July 1, 2010, to December 31, 2018. Nearly one-third (34,256, 32.4%) had at least 1 positive result. The number of persons receiving positive test results increased 6-fold from 1110 in 2011 to 7798 in 2018. Of those receiving positive test results, mean [SD] age was 46.9 (19.8) years; men were more likely to test positive than women (43.3% vs 26.0%). Arkansas, Virginia, Kentucky, Oklahoma, and Missouri had the highest number of persons who were tested and had a positive result per 100,000 population.ConclusionMore than 34,000 persons, most presumably symptomatic, have received positive test results for IgE antibodies to alpha-gal, suggesting AGS is an increasingly recognized public health problem. The geographic distribution of persons who tested positive is consistent with exposure to Amblyomma americanum ticks.  相似文献   
87.
AIMS: We investigated the value of a novel early biomarker, heart-type fatty acid-binding protein (H-FABP), in risk stratification of patients with acute pulmonary embolism (PE). METHODS AND RESULTS: We prospectively included 107 consecutive patients with confirmed PE. The endpoints were (i) PE-related death or major complications and (ii) overall 30-day mortality. Overall, 29 patients (27%) had abnormal (>6 ng/mL) H-FABP levels at presentation. Of those, 12 (41%) had a complicated course, whereas all patients with normal baseline H-FABP had a favourable 30-day outcome (OR, 71.45; P<0.0001). At multivariable analysis, H-FABP (P<0.0001), but not cardiac troponin T (P=0.13) or N-terminal pro-brain natriuretic peptide (P=0.36), predicted an adverse outcome. Evaluation of a strategy combining biomarker testing with echocardiography revealed that patients with a negative H-FABP test had an excellent prognosis regardless of echocardiographic findings. In contrast, patients with a positive H-FABP test had a complication rate of 23.1% even in the presence of a normal echocardiogram, and this rose to 57.1% if echocardiography also demonstrated right ventricular dysfunction (OR vs. a negative H-FABP test, 5.6 and 81.4, respectively). CONCLUSION: H-FABP is a promising early indicator of right ventricular injury and dysfunction in acute PE. It may help optimize risk stratification algorithms and treatment strategies.  相似文献   
88.
89.
TUBERCULOUS PERICARDITIS   总被引:1,自引:0,他引:1  
  相似文献   
90.
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