全文获取类型
收费全文 | 16941篇 |
免费 | 919篇 |
国内免费 | 164篇 |
专业分类
耳鼻咽喉 | 213篇 |
儿科学 | 322篇 |
妇产科学 | 374篇 |
基础医学 | 1950篇 |
口腔科学 | 628篇 |
临床医学 | 1311篇 |
内科学 | 4383篇 |
皮肤病学 | 213篇 |
神经病学 | 1954篇 |
特种医学 | 627篇 |
外科学 | 2804篇 |
综合类 | 40篇 |
一般理论 | 2篇 |
预防医学 | 649篇 |
眼科学 | 275篇 |
药学 | 895篇 |
中国医学 | 17篇 |
肿瘤学 | 1367篇 |
出版年
2024年 | 14篇 |
2023年 | 191篇 |
2022年 | 453篇 |
2021年 | 700篇 |
2020年 | 415篇 |
2019年 | 574篇 |
2018年 | 613篇 |
2017年 | 469篇 |
2016年 | 518篇 |
2015年 | 569篇 |
2014年 | 747篇 |
2013年 | 1000篇 |
2012年 | 1431篇 |
2011年 | 1493篇 |
2010年 | 783篇 |
2009年 | 751篇 |
2008年 | 1083篇 |
2007年 | 1079篇 |
2006年 | 937篇 |
2005年 | 918篇 |
2004年 | 891篇 |
2003年 | 693篇 |
2002年 | 640篇 |
2001年 | 83篇 |
2000年 | 46篇 |
1999年 | 76篇 |
1998年 | 130篇 |
1997年 | 115篇 |
1996年 | 85篇 |
1995年 | 73篇 |
1994年 | 70篇 |
1993年 | 52篇 |
1992年 | 31篇 |
1991年 | 27篇 |
1990年 | 36篇 |
1989年 | 32篇 |
1988年 | 17篇 |
1987年 | 14篇 |
1986年 | 22篇 |
1985年 | 10篇 |
1984年 | 18篇 |
1983年 | 19篇 |
1982年 | 24篇 |
1981年 | 15篇 |
1980年 | 18篇 |
1979年 | 7篇 |
1978年 | 6篇 |
1976年 | 4篇 |
1974年 | 3篇 |
1973年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Laura Santambrogio Maria Lipartiti Alessandro Bruni Roberto Dal Toso 《Journal of neuroimmunology》1993,45(1-2)
The presence of functional dopamine receptors on differentiated cells of the mammalian immune system is still under discussion. This study has utilized (-)-[3H]sulpride as a ligand to detect the presence of recognition sites of the dopamine D2 receptor family on human T- and B-lymphocytes. The (-)-[3H]sulpiride binding was of high affinity (Kd 0.9 nM ± 0.2 nM, specific, saturable (Bmax 10.2 ± 1.4 fmol/106 cells) and reversible. The pharmacological characterization of the recognition site suggests, similarities mainly with the D2 and D4 rather than D3 subtype of dopamine receptor. Furthermore, dopamine treatment was able to reduce the intracellular cAMP levels of lymphocytes stimulated with forskolin, thus suggesting a potential functional significance of this dopamine receptor in mediating neural-immune interactions. 相似文献
62.
63.
Prevalence of hereditary ataxias and spastic paraplegias in Molise,a region of Italy 总被引:8,自引:0,他引:8
Alessandro Filla Giuseppe De Michele Roberto Marconi Luigi Bucci Carmine Carillo Anna Elisa Castellano Lucio Iorio Claudio Kniahynicki Francesco Rossi Giuseppe Campanella 《Journal of neurology》1992,239(6):351-353
Summary An epidemiological survey of hereditary ataxias and paraplegias was conducted in Molise, a region of Italy (335, 211 inhabitants on 1 January 1989). Total prevalence was 7.5 x 10–5 inhabitants (95% confidence limits 4.8–11.1). There were 7 patients with Friedreich's disease, 5 with early onset cerebellar ataxia with retained tendon reflexes, 4 with ataxia-telangiectasia, 9 with hereditary spastic paraplegias (2 autosomal dominant and 7 autosomal recessive cases). There was no patient with autosomal dominant cerebellar ataxia. 相似文献
64.
HEALTH CARE RESEARCH: WHAT IS IT ABOUT? 总被引:1,自引:0,他引:1
65.
Testa Rodolfo Abbiati Gianalfredo Ceserani Roberto Restelli Gianvico Vanasia Alessandro Barone Domenico Gobbi Marco Mennini Tiziana 《Pharmaceutical research》1989,6(7):571-577
A series of 21 neuroleptics with different chemical structures (phenothiazines, thioxanthenes, dibenzodiazepines, butyrophenones, benzamides, etc.) was examined for their in vitro interactions with 12 neurotransmitter binding sites in the rat brain (alpha- and beta-noradrenergic, dopaminergic, muscarinic, serotoninergic, histaminic, and opioid receptors, calcium channels, and serotonin uptake binding sites). The biochemical profile obtained from the binding data was compared with reported pharmacological and clinical profiles for this class of compounds by cluster analysis. Cluster analysis on binding data classified the compounds in three main subgroups: benzamides, compounds with an affinity mainly for DA2 and 5-HT2 receptors and inactive at muscarinic receptors, and compounds with a high affinity for alpha 1-adrenergic receptors and muscarinic receptors. The main subgroups resulting from cluster analysis of previously published pharmacological and clinical data for neuroleptics contain compounds common to the present study, with some correlations. The results extend previous observations that a complete binding profile corresponds to the pharmacological and clinical profile of this class of compounds. 相似文献
66.
Fiore L Plebani A Buttinelli G Fiore S Donati V Marturano J Soresina A Martire B Azzari C Nigro G Cardinale F Trizzino A Pignata C Alvisi P Anastasio E Bossi G Ugazio AG 《Clinical immunology (Orlando, Fla.)》2004,111(1):98-102
Patients with agammaglobulinemia may excrete enteroviruses, including vaccine-derived poliovirus, for prolonged periods of time. This poses a risk to the patients but it also may pose a risk to the population after eradication of poliovirus and the cessation of routine vaccination. To assess this risk, a pilot study was performed to identify potential poliovirus long-term excretors in a cohort of 38 patients with a definite/presumptive diagnosis of X-linked agammaglobulinemia (XLA). Stool samples were analyzed to detect any polio or other enteroviruses replicating in the gut and neutralizing antibodies against polioviruses were measured in the sera. No viruses were isolated from the stool samples and most sera had neutralizing antibody levels against all three poliovirus serotypes considered by the WHO to be protective in immunocompetent individuals. This suggests that long-term excretion of enteroviruses in patients with agammaglobulinemia is relatively uncommon. 相似文献
67.
Effect of interferon-alpha therapy on epitope-specific cytotoxic T lymphocyte responses in hepatitis C virus-infected individuals. 总被引:4,自引:0,他引:4
Simona Vertuani Martina Bazzaro Guido Gualandi Fabiola Micheletti Mauro Marastoni Cinzia Fortini Alessandro Canella Michele Marino Roberto Tomatis Serena Traniello Riccardo Gavioli 《European journal of immunology》2002,32(1):144-154
The majority of hepatitis C virus (HCV)-infected individuals fail to resolve the infection and become chronically infected despite the presence of HCV-specific CTL responses directed to different HCV-derived peptide antigens. Only a minority of individuals is able to clear the virus by mounting efficient CTL responses early after acute infection, but at present it is not clear whether viral clearance is associated with CTL responses of defined specificity. To elucidate those responses associated with improvement of the disease, we analyzed CTL responses to 16 different HLA-A2-presented, HCV-derived epitopes in 12 chronically infected patients, 14 chronically infected patients treated with interferon-alpha, and in one patient with acute symptomatic disease. We show here that the majority of chronically infected individuals present CTL responses directed to an NS4-derived peptide antigen (amino acids 1789-1797). Treated patients presented stronger HCV-specific CTL responses and therapy-induced changes in CTL target choice. In particular, 13 out of 14 individuals responded to an NS3-derived epitope (amino acids 1073-1081). By longitudinal analysis we show that five individuals responding to IFN-alpha therapy with decreases in alanine aminotransferase levels presented a strong CTL activity directed to the NS3-derived epitope. One patient that spontaneously resolved the infection presented a generally strong CTL activity specific for HCV-derived epitopes with a dominant response to the NS3-derived peptide antigen. This suggests that CTL responses directed to this NS3-derived antigen may be beneficial for the control of HCV infection. Improvement of these responses may represent a therapeutic intervention in chronic HCV infection. 相似文献
68.
Monti P Marchesi F Reni M Mercalli A Sordi V Zerbi A Balzano G Di Carlo V Allavena P Piemonti L 《Virchows Archiv : an international journal of pathology》2004,445(3):236-247
There are a large number of stable pancreatic ductal carcinoma cell lines (PDCL) that are used by researchers worldwide. Detailed data about their differentiation status and genetic alterations are present in the literature, but a systematic correlation with cell biological behavior is often lacking. PDCL (n=12) were clustered by source of tumor cell (ascites, primary tumor, metastasis), and the data of functional cell biology were correlated with the reported structural and genetic profiles. Major histocompatibility complex expression, chemosensitivity and aneuploidia appeared to be related to the source of PDCL, and proliferative capacity appeared to be related to the grade of differentiation. No correlation between genetic/structural features of PDCL and biological behavior was found. All the cell lines appeared generally insensitive to in vitro treatment with 5-fluorouracil and showed variable degrees of susceptibility to gemcitabine, raltitrexed and oxaliplatin. All the PDCL showed resistance to Fas-mediated apoptosis but were significantly sensitive to the pro-apoptotic effect of inflammatory cytokines [interleukin (IL)-1, tumor necrosis factor (TNF) and interferon ]. PDCL were characterized for the secretion of several factors relevant to the tumor-immune cross talk. Vascular endothelial growth factor, CCL2, CCL5 and transforming growth factor were the factors most frequently released; less frequent was the secretion of CXCL8, CCL22, IL-6 and sporadically CXCL12, IL-10 and hepatocyte growth factor. The cytokines IL-1 and TNF were always undetectable. In conclusion, a clear correlation between structural/genetic features and function could not be detected, suggesting the weakness of a morphological classification for the in vitro studies of pancreatic cancer. 相似文献
69.
Environmental enrichment potentiates neural plasticity, enhancing acquisition and consolidation of memory traces. In the sensory cortices, after cortical circuit maturation and sensory function acquisition are completed, neural plasticity declines and the critical period 'closes'. In the visual cortex, this process can be prevented by dark-rearing, and here we show that environmental enrichment can promote physiological maturation and consolidation of visual cortical connections in dark-reared rats, leading to critical period closure. 相似文献
70.
Vasculogenic mimicry has no prognostic significance in pT3 and pT4 cutaneous melanoma 总被引:4,自引:0,他引:4
Massi D Franchi A Paglierani M Ketabchi S Borgognoni L Reali UM Santucci M 《Human pathology》2004,35(4):496-502
The concept of vasculogenic mimicry has been introduced to define periodic acid-Schiff (PAS)-positive channels and loops lined by tumor cells, instead of endothelium, able to contribute to microcirculation in uveal melanomas. Previous studies have shown that the PAS-positive patterns are associated with a poor prognosis in uveal melanoma. The aim of the current study was to investigate whether vasculogenic mimicry has a prognostic impact in pT3 and pT4 cutaneous melanoma. Fifteen patients with pT3 and pT4 cutaneous melanoma who did not experience progression after 10 years of follow-up and 30 matched controls who underwent progression were selected. Tumor sections were stained with PAS reaction, omitting the nuclear counterstaining. For immunohistochemistry, sections were stained with CD31, CD105 (endoglin), and laminin. Differences in the distribution of the PAS-positive patterns and a series of clinicopathological variables were evaluated by the Pearson chi(2) and Mann-Whitney U tests. We observed PAS-positive linear sheets, arcs, elliptical loops, and networks encircling roundish to oval aggregates of melanoma cells. The overall distribution of the PAS-positive patterns did not match with the blood microvessels' architecture as detected by immunohistochemical analysis. No statistically significant differences in the distribution of PAS-positive patterns were found between cases and controls. The presence of a parallel pattern correlated significantly with thickness (P = 0.04), whereas an inverse correlation was found with vessel area (P = 0.05). In conclusion, our results suggest that there is a mismatch between vasculogenic mimicry and tumor angiogenesis and do not support any prognostic role of vasculogenic mimicry in thick cutaneous melanoma. 相似文献