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   194339篇
  免费   18388篇
  国内免费   12371篇
耳鼻咽喉   1755篇
儿科学   2030篇
妇产科学   2536篇
基础医学   23362篇
口腔科学   3440篇
临床医学   25394篇
内科学   28439篇
皮肤病学   2519篇
神经病学   10189篇
特种医学   7084篇
外国民族医学   102篇
外科学   20184篇
综合类   31208篇
现状与发展   40篇
一般理论   26篇
预防医学   13025篇
眼科学   4986篇
药学   20851篇
  192篇
中国医学   11579篇
肿瘤学   16157篇
  2024年   762篇
  2023年   3131篇
  2022年   8143篇
  2021年   10238篇
  2020年   7717篇
  2019年   6696篇
  2018年   7023篇
  2017年   6432篇
  2016年   6032篇
  2015年   9269篇
  2014年   11288篇
  2013年   10436篇
  2012年   15152篇
  2011年   16372篇
  2010年   10456篇
  2009年   8039篇
  2008年   10691篇
  2007年   10135篇
  2006年   9751篇
  2005年   9483篇
  2004年   6121篇
  2003年   5672篇
  2002年   4717篇
  2001年   3960篇
  2000年   4071篇
  1999年   4079篇
  1998年   2452篇
  1997年   2463篇
  1996年   1895篇
  1995年   1833篇
  1994年   1587篇
  1993年   962篇
  1992年   1351篇
  1991年   1187篇
  1990年   949篇
  1989年   904篇
  1988年   805篇
  1987年   671篇
  1986年   496篇
  1985年   423篇
  1984年   213篇
  1983年   174篇
  1982年   101篇
  1981年   132篇
  1980年   84篇
  1979年   117篇
  1978年   57篇
  1977年   59篇
  1976年   47篇
  1974年   47篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
Coxsackievirus B3 (CVB3) infection can result in myocarditis, which in turn may lead to a protracted immune response and subsequent dilated cardiomyopathy. Human decay-accelerating factor (DAF), a binding receptor for CVB3, was synthesized as a soluble IgG1-Fc fusion protein (DAF-Fc). In vitro, DAF-Fc was able to inhibit complement activity and block infection by CVB3, although blockade of infection varied widely among strains of CVB3. To determine the effects of DAF-Fc in vivo, 40 adolescent A/J mice were infected with a myopathic strain of CVB3 and given DAF-Fc treatment 3 days before infection, during infection, or 3 days after infection; the mice were compared with virus alone and sham-infected animals. Sections of heart, spleen, kidney, pancreas, and liver were stained with hematoxylin and eosin and submitted to in situ hybridization for both positive-strand and negative-strand viral RNA to determine the extent of myocarditis and viral infection, respectively. Salient histopathologic features, including myocardial lesion area, cell death, calcification and inflammatory cell infiltration, pancreatitis, and hepatitis were scored without knowledge of the experimental groups. DAF-Fc treatment of mice either preceding or concurrent with CVB3 infection resulted in a significant decrease in myocardial lesion area and cell death and a reduction in the presence of viral RNA. All DAF-Fc treatment groups had reduced infectious CVB3 recoverable from the heart after infection. DAF-Fc may be a novel therapeutic agent for active myocarditis and acute dilated cardiomyopathy if given early in the infectious period, although more studies are needed to determine its mechanism and efficacy.  相似文献   
992.
Park IK  Yang J  Jeong HJ  Bom HS  Harada I  Akaike T  Kim SI  Cho CS 《Biomaterials》2003,24(13):2331-2337
Galactose moiety as the hepatocyte anchorage was covalently coupled with chitosan for the development of synthetic extracellular matrix. Hepatocytes adhesion to galactosylated chitosan (GC)-coated polystyrene (PS) dish became as high as 94.7% after 2 h incubation whereas the hepatocytes adhesion to chitosan-coated PS dish was 69.1%, indication of galactose-specific recognition between GC molecules and asialoglycoprotein receptors of hepatocytes. The DNA synthesis of the hepatocytes adhered to GC-coated dish was increased in the presence of epidermal growth factor (EGF) at low concentration of GC (0.05 microg/ml) whereas the DNA synthesis of the hepatocytes adhered to GC-coated dish was decreased in the presence of EGF at high concentration of GC (5 microg/ml). The spreading shapes of the hepatocytes adhered to the surface in the presence of EGF at low concentration of GC (0.05 microg/ml) were enhanced than in the absence of EGF. The hepatocytes adhered to the surface at high concentration of GC (5 microg/ml) showed round shapes and exhibited many spheroid formation after 24 h in the presence of EGF.  相似文献   
993.
研究了18例新鲜尸体T12-L5腰段脊柱应力松弛,蠕变特性。测定了完整脊柱(正常组)及模拟前路(对照1组),后路手术(对照2组)腰段脊柱的应力松弛和蠕变效应,得出了在恒应变,应力条件下应力-时间曲线及数据,用回归分析的方法处理实验数据,得出了归一化应务松弛,蠕变函数及曲线,对前路间盘摘除术与后路间盘摘除术对脊柱粘弹性的影响进行分析讨论。  相似文献   
994.
IntroductionHepatocellular carcinoma (HCC) is one of the most common cancers worldwide. Despite the therapeutic advances in HCC in the past few decades, the mortality rate of HCC is still high. Hepatitis C (HCV) infection is one of the major etiological risk factors of HCCs. However, the underlying mechanisms of HCV-induced hepatocarcinogenesis remain largely unclear.Material and methodsOur study represented the comprehensive analysis of differentially expressed lncRNAs in HCV-positive HCC for the first time by analyzing the public dataset GSE17856. Co-expression network and gene ontology (GO) analysis revealed the functions of those differentially expressed lncRNAs.ResultsWe identified 256 upregulated lncRNAs and 198 downregulated lncRNAs in HCV- positive HCC compared to the normal liver tissues. Co-expression network and GO analysis showed that these lncRNAs were involved in regulating metabolism, energy pathways, proliferation and the immune response. Seven lncRNAs (LOC341056, CCT6P1, PTTG3P, LOC643387, LOC100133920, C3P1 and C22orf45) were identified as key lncRNAs and co-expressed with more than 100 differentially expressed genes (DEGs) in HCV-related HCC. Kaplan-Meier analysis showed that higher expression levels of LOC643387, PTTG3P, LOC341056, CCT6P1 and lower expression levels of C3P1 and C22orf45 were associated with shorter survival time in the TCGA dataset.ConclusionsWe believe that this study can provide novel potential therapeutic and prognostic biomarkers for HCV-positive HCC.  相似文献   
995.

Objectives

Rigorous visual evidence on whether or not biofilms are involved in diabetic foot osteomyelitis (DFO) is lacking. We employed a suite of molecular and microscopic approaches to investigate the microbiome, and phenotypic state of microorganisms involved in DFO.

Methods

In 20 consecutive subjects with suspected DFO, we collected intraoperative bone specimens. To explore the microbial diversity present in infected bone we performed next generation DNA sequencing. We used scanning electron microscopy (SEM) and peptide nucleic acid fluorescent in situ hybridization (PNA-FISH) with confocal microscopy to visualize and confirm the presence of biofilms.

Results

In 19 of 20 (95%) studied patients presenting with DFO, it was associated with an infected diabetic foot ulcer. By DNA sequencing of infected bone, Corynebacterium sp. was the most commonly identified microorganism, followed by Finegoldia sp., Staphylococcus sp., Streptococcus sp., Porphyromonas sp., and Anaerococcus sp. Six of 20 bone samples (30%) contained only one or two pathogens, while the remaining 14 (70%) had polymicrobial communities. Using a combination of SEM and PNA-FISH, we identified microbial aggregates in biofilms in 16 (80%) bone specimens and found that they were typically coccoid or rod-shaped aggregates.

Conclusions

The presence of biofilms in DFO may explain why non-surgical treatment of DFO, relying on systemic antibiotic therapy, may not resolve some chronic infections caused by biofilm-producing strains.  相似文献   
996.
Basu S  Yang ST 《Tissue engineering》2005,11(5-6):940-952
The ability of human astrocytes grown in nonwoven fibrous matrices to produce glial cell line-derived neurotrophic factor (GDNF) was studied. GDNF has the ability to selectively nourish and regenerate dopaminergic neurons and thus can provide a new treatment of Parkinson's disease. Compressed polyethylene terephthalate (PET) fabrics (porosity, 88.8%; mean pore diameter, 64 microm), treated with boiling NaOH, was effective in supporting high-density growth of astrocytes with stable GDNF production over the entire period of 18 days studied. Treatment of PET with NaOH renders the fiber surface more hydrophilic, thereby facilitating attachment and spreading of cells, whereas matrix compression allows cells to grow along and also between the fibers of these matrices to a higher density. The average production of GDNF by cells grown in these matrices (approximately 2 cm in diameter) was 21.7 pg/mL x day, with an average high concentration of 64.6 pg/mL, which is well above the effective concentration of 40 pg/mL. This work shows promise in culturing astrocytes in PET matrices as the first step in developing a potential implantable tissue-engineering device for treating patients with Parkinson's disease.  相似文献   
997.
In our previous study we demonstrated that acupuncture at Shenmen (HT7) points suppressed a decrease of accumbal dopamine (DA) release in ethanol-withdrawn rats. Furthermore, here we found that it inhibited behavioral withdrawal signs of ethanol. In an effort to better understand the mechanisms underlying this inhibition, the potential role of GABA receptor system in acupuncture was investigated. Male Sprague–Dawley rats were treated with 3 g/kg/day of ethanol (20%, w/v) or saline by intraperitoneal injection for 21 days. Following 48 or 72 h of ethanol withdrawal, acupuncture was applied at bilateral HT7 for 1 min. The selective GABAA antagonist bicuculline and the selective GABAB antagonist SCH 50911 were injected intraperitoneally 20 min before acupuncture, respectively. Importantly, suppressive effects of acupuncture on DA deficiency were completely abolished by SCH 50911, but not by bicuculline, whereas ameliorating effects of acupuncture on ethanol withdrawal syndrome were completely blocked either by SCH 50911 or bicuculline. These results suggest that acupuncture at specific acupoint HT7 may normalize the DA release in the mesolimbic system and attenuate withdrawal syndrome through the GABAB receptor system in ethanol-withdrawn rats.  相似文献   
998.
Stargardt disease 1 (STGD1) is the most prevalent retinal dystrophy caused by pathogenic biallelic ABCA4 variants. Forty‐two unrelated patients mostly originating from Western China were recruited. Comprehensive ophthalmological examinations, including visual acuity measurements (subjective function), fundus autofluorescence (retinal imaging), and full‐field electroretinography (objective function), were performed. Next‐generation sequencing (target/whole exome) and direct sequencing were conducted. Genotype grouping was performed based on the presence of deleterious variants. The median age of onset/age was 10.0 (5–52)/29.5 (12–72) years, and the median visual acuity in the right/left eye was 1.30 (0.15–2.28)/1.30 (0.15–2.28) in the logarithm of the minimum angle of resolution unit. Ten patients (10/38, 27.0%) showed confined macular dysfunction, and 27 (27/37, 73.7%) had generalized retinal dysfunction. Fifty‐eight pathogenic/likely pathogenic ABCA4 variants, including 14 novel variants, were identified. Eight patients (8/35, 22.8%) harbored multiple deleterious variants, and 17 (17/35, 48.6%) had a single deleterious variant. Significant associations were revealed between subjective functional, retinal imaging, and objective functional groups, identifying a significant genotype–phenotype association. This study illustrates a large phenotypic/genotypic spectrum in a large well‐characterized STGD1 cohort. A distinct genetic background of the Chinese population from the Caucasian population was identified; meanwhile, a genotype–phenotype association was similarly represented.  相似文献   
999.
Summary Three major types of HTLV-I had been proposed, the Melanesian type, the Zairian type, and the cosmopolitan type, which was further divided into subtypes A, B and C, according to the phylogenetic tree constructed from LTR sequences of current HLTV-I isolates. In this study, the envelope gene sequences of HTLV-I from 9 Taiwanese were analyzed. Based on the phylogenetic tree constructed by unweighed pair group method and the sequence homology analysis by GCG computer programs, the envelope gene sequences of HTLV-I proviruses from these 9 Taiwanese belonged to subtype A or subtype B of the cosmopolitan type and were closely related to HTLV-I from Japan. Twelve subtype-specific nucleotide variations were deduced from the comparison of complete or partial envelope gene sequences of 16 HTLV-I isolates of known subtypes as well as those of 9 Taiwanese. These data provided the basis for subtyping the cosmopolitan type of HTLV-I by amplification of envelope gene sequences and restriction fragment length polymorphism studies. A more extensive survey based upon this proposal was warranted.  相似文献   
1000.
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