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   11847篇
  免费   737篇
  国内免费   62篇
耳鼻咽喉   110篇
儿科学   316篇
妇产科学   289篇
基础医学   1726篇
口腔科学   282篇
临床医学   1033篇
内科学   2701篇
皮肤病学   426篇
神经病学   1168篇
特种医学   272篇
外科学   981篇
综合类   58篇
现状与发展   1篇
一般理论   3篇
预防医学   1380篇
眼科学   241篇
药学   801篇
中国医学   50篇
肿瘤学   808篇
  2024年   11篇
  2023年   141篇
  2022年   273篇
  2021年   529篇
  2020年   270篇
  2019年   447篇
  2018年   539篇
  2017年   328篇
  2016年   313篇
  2015年   387篇
  2014年   536篇
  2013年   652篇
  2012年   1016篇
  2011年   976篇
  2010年   567篇
  2009年   464篇
  2008年   754篇
  2007年   734篇
  2006年   625篇
  2005年   659篇
  2004年   565篇
  2003年   523篇
  2002年   472篇
  2001年   86篇
  2000年   39篇
  1999年   87篇
  1998年   80篇
  1997年   65篇
  1996年   62篇
  1995年   54篇
  1994年   28篇
  1993年   40篇
  1992年   42篇
  1991年   26篇
  1990年   28篇
  1989年   15篇
  1988年   18篇
  1987年   15篇
  1986年   10篇
  1985年   13篇
  1984年   21篇
  1983年   15篇
  1981年   11篇
  1980年   7篇
  1979年   7篇
  1978年   7篇
  1977年   7篇
  1974年   7篇
  1972年   7篇
  1970年   9篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
Clinical Rheumatology - To analyze the diagnostic utility of lung ultrasound (US) to detect interstitial lung disease (ILD) in rheumatoid arthritis (RA) patients comparing with high-resolution...  相似文献   
142.
Risk factors for diffuse and focal macular edema   总被引:1,自引:0,他引:1  
OBJECTIVE: The epidemiological risk factors for the different forms of diabetic macular edema (focal or diffuse) are not differentiated in the literature. In the present study, the objective was to determine which risk factors influence the appearance of focal or diffuse macular edema. RESEARCH, DESIGN, AND METHODS: A 4-year prospective study in a population of Type II diabetic patients (NIDDM) in three groups, the first with 29 patients with diffuse diabetic macular edema (Group A), the second with 32 patients with focal macular edema (Group B), and the third with 32 patients with diabetic retinopathy but without diabetic macular edema (Group C); the three groups were selected on the basis of sex, age, and duration of diabetes with similar patterns. We studied the following risk factors: treatment of diabetes mellitus by insulin, presence of diastolic blood hypertension, presence of microalbuminuria or diabetic nephropathy, levels of HbA1c, type of diabetic retinopathy, presence of previous panretinal photocoagulation, and levels of triglycerides and fractions of cholesterol. RESULTS: In discriminant analysis and in order of importance, the epidemiological risk factors for Group A were the following: presence of panretinal laser, diastolic blood hypertension, diabetic nephropathy, and insulin treatment; for group B, the risk factors were the following: insulin treatment, presence of diastolic blood hypertension, and high levels of glycated haemoglobin (HbA1c); and for group, C the risk factors were the following: diastolic blood hypertension, insulin treatment of diabetes, and high levels of HbA1c. CONCLUSIONS: In the present study, the group of patients with focal macular edema were epidemiologically similar to the group of patients with diabetic retinopathy without macular edema, the group of patients with diffuse macular edema were epidemiologically different.  相似文献   
143.
Long-term primary cultures were established fromfetal or neonatal livers by using cell suspensionsdepleted of red blood cells and by culturing the cellsin hormonally defined medium containing dimethyl sulfoxide. Two distinct populations of hepaticprogenitor cells were evident in the cultures, based onmorphology, proliferative ability, and liver-specificgene expression. Most colonies consisted of immature hepatic progenitors: small, blastlike cells,weakly expressing alpha-fetoprotein, albumin, and-glutamyltranspeptidase, and showing evidence ofproliferation as measured by bromodeoxyuridineincorporation. At the perimeter of these colonies of immaturecells and forming some colonies by themselves were moremature hepatic progenitor cells: larger cells, withincreased cytoplasmic to nuclear ratios, little proliferation, and strongly expressing albumin,alpha-fetoprotein, and -glutamyltranspeptidase.The latter two proteins were localized to the bilecanalicular membranes of these cells. Glycogen deposits were present in the mature cells from day 14embryos after eight days of culture. Thus, DMSOtreatment of hepatic parenchymal progenitors provides anovel system for studies of liver development.  相似文献   
144.
We evaluated the effect of salvage antiretroviral therapy with lopinavir/ritonavir (LPV/r) on the immune system of heavily antiretroviral pretreated HIV-infected children. We carried out a longitudinal study in 20 antiretroviral experienced HIV-infected children to determine the changes in several immunological parameters (T cell subsets, thymic function) every 3 months during 18 months of follow-up on salvage therapy with LPV/r. Statistical analyses were performed with the Wilcoxon test, taking as a reference the basal value at the entry in the study. HIV-infected children showed an increase of CD4+ T cells, a decrease in CD8+ T cells, and an increase in T cell rearrangement excision circle (TRECs) levels. The percentage of HIV children with undetectable viral load (VL < or = 400 copies/ml) increased significantly (p = 0.007) and the percentage with SI viral phenotype decreased significantly (p = 0.002) at the end of the study. Thus, the viral phenotype changed to NSI/R5 after salvage therapy with LPV/r. Interestingly, we observed a significant decrease of memory (CD4+ CD45RO+) and a moderate decrease of activated (CD4+ HLA-DR+, CD4+ HLA-DR+CD38, CD4+, CD45RO+HLA-DR+) CD4+ T cells during the follow-up. On the other hand, memory (CD8+ CD45RO+ and CD8+ CD45RO+CD38+), activated (CD8+ HLA-DR+CD38+, CD8+ HLA-DR+, CD8+ CD38+), and effector (CD8+ CD57+, CD8+ CD28(-)CD57+) CD8+ T cells had a very significant decrease during follow-up. Our data indicate an immune system reconstitution in heavily pretreated HIV-infected children in response to salvage therapy with LPV/r as a consequence of a decrease in immune system activation and an increase in thymic function.  相似文献   
145.
INTRODUCTION: Atrial fibrillation (AF) in the left atrium (LA) is poorly defined in terms of regional differences in the degree of organization, characteristics of paroxysmal and persistent variants, and electrophysiologic events that develop at the onset of episodes. METHODS AND RESULTS: The study population consisted of 21 patients (15 men and 6 women; mean age 58+/-9.4 years) with paroxysmal (10 patients) or persistent (11 patients) AF. Mapping of the LA during sustained episodes and the onset of AF was performed with a 64-electrode basket catheter. At the onset of AF, repetitive beats starting with atrial premature complexes and ending with generation of the earliest fibrillatory activity were defined as intermediary rhythm. Patients with paroxysmal AF had longer AF cycle lengths and more pronounced regional differences than patients with persistent AF. In total, AF cycle lengths in the LA in patients with persistent AF were 20% shorter than in patients with paroxysmal AF. Initiation of AF was preceded by an intermediary rhythm of 5.5+/-2.5 cycles (6.3+/-2.7 cycles in paroxysmal AF vs 4.2+/-1.0 cycles in persistent AF; P = 0.026). At the onset of AF, the earliest generators of fibrillatory activity were located more frequently in the posterior wall of the LA. CONCLUSION: AF in the LA displays substantial regional differences in terms of AF cycle lengths and degree of organization. Patients with persistent AF have shorter cycle lengths and a higher degree of disorganized activity than patients with paroxysmal AF. Intermediary rhythms play an important role in initiation of AF via activation of generator regions in the LA.  相似文献   
146.
The Hedgehog (Hh) family of secreted signaling proteins has a broad variety of functions during metazoan development and implications in human disease. Despite Hh being modified by two lipophilic adducts, Hh migrates far from its site of synthesis and programs cellular outcomes depending on its local concentrations. Recently, lipoproteins were suggested to act as carriers to mediate Hh transport in Drosophila. Here, we examine the role of lipophorins (Lp), the Drosophila lipoproteins, in Hh signaling in the wing imaginal disk, a tissue that does not express Lp but obtains it through the hemolymph. We use the up-regulation of the Lp receptor 2 (LpR2), the main Lp receptor expressed in the imaginal disk cells, to increase Lp endocytosis and locally reduce the amount of available free extracellular Lp in the wing disk epithelium. Under this condition, secreted Hh is not stabilized in the extracellular matrix. We obtain similar results after a generalized knock-down of hemolymph Lp levels. These data suggest that Hh must be packaged with Lp in the producing cells for proper spreading. Interestingly, we also show that Patched (Ptc), the Hh receptor, is a lipoprotein receptor; Ptc actively internalizes Lp into the endocytic compartment in a Hh-independent manner and physically interacts with Lp. Ptc, as a lipoprotein receptor, can affect intracellular lipid homeostasis in imaginal disk cells. However, by using different Ptc mutants, we show that Lp internalization does not play a major role in Hh signal transduction but does in Hh gradient formation.  相似文献   
147.
148.
Macrophagic myofasciitis (MMF) is an inflammatory myopathy related to aluminum-containing vaccines. Described in 1998, most cases were reported in adults, with only 22 cases being reported in children. Three children aged between 13 months and 3½ years were investigated in our institution for neuromuscular symptoms. They underwent thorough clinical, familial, and laboratory investigations, electroneuromyography, muscle biopsy with transmission electron microscopy, scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS), and, in one case, brain magnetic resonance imaging. They had received regular immunizations. Two patients were hypotonic and one presented with myotonia. Muscle biopsy of all patients presented macrophagic infiltrates with intracytoplasmic aluminum content as revealed by SEM/EDS analysis. Their diverse clinical picture does not support a direct relationship between local morphologic findings and systemic symptoms. The atypical clinical presentation of these children may not result from the superposition of MMF upon a background systemic neuromyopathy, suggesting instead that they are two coincident and independent conditions. Although the finding of macrophage infiltrates in muscle tissue is not new, the identification of aluminum content is recent. The use of tissue sections for aluminum detection and mapping by SEM/EDS is conclusive for, diagnosis; it has not been reported previously in a pathology journal, to the authors' knowledge.  相似文献   
149.
Journal of Autism and Developmental Disorders - The objective of our study was to evaluate the frequency of treatable inborn errors of metabolism (IEM) in a clinical sample of Mexican children and...  相似文献   
150.
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