全文获取类型
收费全文 | 19321篇 |
免费 | 1194篇 |
国内免费 | 604篇 |
专业分类
耳鼻咽喉 | 134篇 |
儿科学 | 478篇 |
妇产科学 | 242篇 |
基础医学 | 2741篇 |
口腔科学 | 146篇 |
临床医学 | 1094篇 |
内科学 | 3841篇 |
皮肤病学 | 229篇 |
神经病学 | 1432篇 |
特种医学 | 600篇 |
外国民族医学 | 2篇 |
外科学 | 1476篇 |
综合类 | 1743篇 |
现状与发展 | 2篇 |
预防医学 | 2368篇 |
眼科学 | 224篇 |
药学 | 2609篇 |
2篇 | |
中国医学 | 862篇 |
肿瘤学 | 894篇 |
出版年
2023年 | 154篇 |
2022年 | 286篇 |
2021年 | 462篇 |
2020年 | 358篇 |
2019年 | 913篇 |
2018年 | 834篇 |
2017年 | 544篇 |
2016年 | 440篇 |
2015年 | 590篇 |
2014年 | 874篇 |
2013年 | 1062篇 |
2012年 | 1035篇 |
2011年 | 1591篇 |
2010年 | 1460篇 |
2009年 | 853篇 |
2008年 | 668篇 |
2007年 | 673篇 |
2006年 | 592篇 |
2005年 | 493篇 |
2004年 | 406篇 |
2003年 | 380篇 |
2002年 | 358篇 |
2001年 | 343篇 |
2000年 | 278篇 |
1999年 | 263篇 |
1998年 | 214篇 |
1997年 | 230篇 |
1996年 | 175篇 |
1995年 | 159篇 |
1994年 | 151篇 |
1993年 | 127篇 |
1992年 | 118篇 |
1991年 | 95篇 |
1990年 | 93篇 |
1989年 | 86篇 |
1988年 | 79篇 |
1986年 | 77篇 |
1985年 | 356篇 |
1984年 | 486篇 |
1983年 | 360篇 |
1982年 | 339篇 |
1981年 | 332篇 |
1980年 | 319篇 |
1979年 | 264篇 |
1978年 | 216篇 |
1977年 | 165篇 |
1976年 | 243篇 |
1975年 | 161篇 |
1974年 | 139篇 |
1973年 | 110篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
R. Gottschalk C. Seidl T. Löffler E. Seifried D. Hoelzer J.P. Kaltwasser 《Tissue antigens》1998,51(3):270-275
Abstract: Genetic hemochromatosis (GH) is closely associated with genes of the major histocompatibility complex (MHC) on chromosome 6. Recently, a candidate gene for GH, with structural similarities to MHC class I genes, designated HLA-H and presently named HFE, has been cloned. The HFE gene is localized telomeric to the MHC and several reports have indicated that the HFE gene is mutated in GH patients. In the present study we have analyzed the relationship of HFE gene variants and disease manifestation in GH patients and family members. Fifty-seven patients with GH, 73 family members and 153 healthy blood donors were studied for the amino acid dimorphism at codon 63 (His63Asp=H63D) and codon 282 (Cys282Tyr= C282Y) of the HFE gene. The codon 63 and 282 dimorphism were defined by PCR amplification of genomic DNA samples and restriction enzyme digestion using RsaI/SnaBI for C282Y and Bcll/Mbo 1 for H63D. Ferritin, transferrin serum levels and total iron-binding capacity were determined prior to therapeutic intervention. The Tyr-282 substitution occurred in 53 (93%) of patients compared with 8 (5.2%) of controls (OR=169, P >0.0001). Fifty-one (90%) patients were Tyr-282 homozygous. In contrast, the Asp-63 substitution was present in 5 (8.8%) of the patients compared with 34 (22%) of controls (OR=0.39, P =NS) with none of the patients being homozygous. In Tyr-282 homozygous GH patients serum ferritin levels, transferrin saturation, liver iron and liver iron index were elevated significantly compared to Tyr-282-negative patients, whereas no difference was observed between Tyr/Cys-282 heterozygous and Tyr-282-negative patients. 相似文献
72.
N. BRUNELLO M. RIVA A. VOLTERRA and G. RACAGNI 《Fundamental & clinical pharmacology》1987,1(5):327-333
Chronic administration of different antidepressant drugs reduced the number of [3H]imipramine [( 3H]IMI) binding sites in rat cerebral cortex. In the same experimental conditions, fluvoxamine and dothiepin, as well as desmethylimipramine, induced an increase in the maximal velocity of high affinity serotonin (5HT) uptake in cortical slices, whereas citalopram and viloxazine were ineffective in this regard. Our results indicate that even if 5HT uptake and [3H]IMI binding sites are located on the same nerve terminals, they are differently modulated. Increased Vmax of the 5HT uptake process could be due to a rebound phenomenon after withdrawal from drugs that acutely inhibit 5HT uptake. The effect on [3H]IMI sites might be explained through either the agonist properties of the drugs towards these sites or the involvement of mechanisms still unknown. 相似文献
73.
We have previously established a cell damage model, with damage induced by either acid or pepsin treatment for 30 min, involving a rat gastric epithelial cell line (RGM1). In the present study, pretreatment of cells with epidermal growth factor (EGF; 0.1–10ng/mL) or sucralfate (0.1–3 mg/mL) for 4 h prevented such cell damage in a concentration-dependent manner. Protection of cells by these drugs was not affected by pretreatment with indomethacin (10−5 mol/L) for 4 h. Removal of Na− , but not Ca2+ , from the acidified medium totally abolished the inhibitory effect of EGF, but not that of sucralfate. Genistein (a tyrosine kinase inhibitor) apparently reduced the inhibitory effect of EGF. DNA synthesis by RGM1 cells did not increase when cells were incubated with EGF for 4 h. We conclude that both EGF and sucralfate protect RGM1 cells from acid- and pepsin-induced damage and that the mechanism of protection by EGF against acid-induced damage seems to be via activation of Na+ /H+ exchangers. 相似文献
74.
The objective of this study was to establish to what extent muscle, cutaneous, and joint afferents alter the excitability of spinal and cortical motor neurons. This question was examined by studying the impact of electrical stimulation of the second and third digits, the median nerve at the wrist, and the recurrent thenar motor branch on the F/H and magneto-electrical cortical motor responses (MEPs) of the thenar muscles. The firing frequencies of single F/H motor unit action potentials were unaltered by the foregoing conditioning peripheral stimuli. MEPs conditioned by motor threshold stimulation of the median nerve at the wrist or the recurrent motor branch were significantly increased in size at conditioning to test intervals of 50 to 80 milliseconds. No significant change in MEP size resulted from conditioning stimulation of the digital nerves. We conclude that muscle afferents were primarily responsible for the increase in MEP size. Conditioning stimuli may allow examiners to assess central motor conduction where it would otherwise be impossible. 相似文献
75.
磺胺噻二嗪硫酮衍生物的合成及其抑菌活性 总被引:1,自引:0,他引:1
利用药物化学骈合原理设计并合成了一系列新的3,5-二取代1,3,5-噻二嗪-2-硫酮类化合物,其结构经红外光谱,紫外光谱及元素分析证实,抑菌活性试验显示了良好的抑菌活性。 相似文献
76.
77.
K. Raghunathan John C. Schmitz D. G. Priest 《Cancer chemotherapy and pharmacology》1997,40(2):126-130
Purpose: A comprehensive pharmacokinetic study of leucovorin (5-formyltetrahydrofolate, 5-HCO-FH4) and its metabolites was conducted in plasma, liver and implanted tumor tissue from mice maintained on a low folic acid diet.
While it has been previously demonstrated that the antitumor activity of fluorouracil (FU) can be potentiated by 5-HCO-FH4, the optimum time for administration of FU after 5-HCO-FH4, to maximally elevate the active folate metabolite methylenetetrahydrofolate in tumor has not been established. Human plasma
studies have defined the pharmacokinetics of circulating 5-HCO-FH4 and its metabolites, but comparison with human tumor accumulation has not been practicable because of sampling difficulties.
As an alternative, a mouse model system, based on low dietary folic acid, was used to evaluate plasma, liver and implanted
tumor reduced folates after administration of 5-HCO-FH4.Methods: Plasma and tissue samples were collected from folate-deplete mice over a 12-h period after intraperitoneal administration
of 90 mg/kg [R, S ] 5-HCO-FH4. Reduced folates were evaluated using a ternary complex assay. Results: The time at which max‐imal accumulation of parent compound and all metabolites, except 5-methyltetrahydrofolate (5-CH3FH4), occurred in tumor was the same as in plasma. Alternatively, peak liver accumulation was delayed relative to plasma for
all folates except 5-CH3FH4. Conclusions: The results suggest that mouse plasma accumulation of reduced folates, with the exception of 5-CH3FH4, can predict tumor accumulation. Hence, evaluation of human plasma folate accumulation may potentially provide a means to
improve the timing of the administration of FU relative to 5-HCO-FH4 to achieve a superior therapeutic outcome.
Received: 24 July 1996 / Accepted: 29 October 1996 相似文献
78.
目的探讨稳定、可靠建立神经干细胞体外增殖的方法,并对增殖培养的细胞进行鉴定。方法获取胚胎大鼠的脑组织,通过加入神经生长因子和采用保留细胞联系技术操作,使脑组织中的神经干细胞在体外克隆增殖并稳定传代。以免疫荧光方法对增殖克隆的神经干细胞球进行鉴定。结果神经干细胞不断增殖形成神经干细胞球且神经干细胞能快速稳定传代增殖。培养的细胞为神经干细胞特异性巢蛋白(nestin)染色阳性细胞。结论在神经生长因子的作用下,利用保留细胞联系技术操作,神经干细胞可以在体外快速、稳定克隆增殖并传代。 相似文献
79.
目的 :探讨6 7Ga心肌显像对小儿病毒性心肌炎 (VMC)诊断的临床价值。方法 :静脉注射6 7Ga 枸橼酸盐 ,48h、72h后开始显像 ,观察心脏部位放射性浓聚情况 ,并计算心 /肺 (H/L)指数 ,根据H/L指数判断心肌炎性病变的严重程度 (H/L指数 >1.2为阳性 )。结果 :78例病毒性心肌炎患儿中 ,50例阳性 (占 64% ) ,其中急性期阳性率为 84% ,恢复期阳性率为 50 % ,慢性期为 2 9% ,急性期阳性率明显高于恢复期和慢性期 (P<0 .0 5)。结论 :心肌6 7Ga放射性浓聚与心肌炎病变程度呈正相关 ,直接反映了病变心肌的炎症反应情况 ,对诊断VMC有较高的临床价值 ,并对VMC治疗、预后有指导作用 相似文献
80.
采集450例战士血清标本,分别用国家代表株甲3/济防/15/90(H3N2)和甲3/北京/32/92(H3N2)作血清血凝抑制抗体测定,青年对甲3型抗体阳性率为60%~67%,其GMT为34~45。1994~1995年两年中在军营人群中分离到3株H3N2毒株流行株,分别应用国际、国家和地方代表株作抗原性分析,证明流行株与它们之间抗原性有明显差异。本文分离到的3株流行株均上送国家流感中心鉴定,证实为H3N2亚型毒株。 相似文献