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   256864篇
  免费   23237篇
  国内免费   11693篇
耳鼻咽喉   3261篇
儿科学   5612篇
妇产科学   3150篇
基础医学   40871篇
口腔科学   9291篇
临床医学   22409篇
内科学   32113篇
皮肤病学   5737篇
神经病学   12944篇
特种医学   8435篇
外国民族医学   164篇
外科学   26308篇
综合类   40367篇
现状与发展   68篇
预防医学   7258篇
眼科学   4614篇
药学   19111篇
  86篇
中国医学   8349篇
肿瘤学   41646篇
  2024年   2053篇
  2023年   3899篇
  2022年   6931篇
  2021年   9491篇
  2020年   8607篇
  2019年   8035篇
  2018年   8119篇
  2017年   8595篇
  2016年   9215篇
  2015年   10246篇
  2014年   15293篇
  2013年   17193篇
  2012年   14344篇
  2011年   16060篇
  2010年   13137篇
  2009年   12840篇
  2008年   13412篇
  2007年   13760篇
  2006年   12457篇
  2005年   11419篇
  2004年   9951篇
  2003年   8618篇
  2002年   7186篇
  2001年   6286篇
  2000年   5124篇
  1999年   4648篇
  1998年   4195篇
  1997年   3869篇
  1996年   3474篇
  1995年   3063篇
  1994年   2679篇
  1993年   2173篇
  1992年   1834篇
  1991年   1710篇
  1990年   1335篇
  1989年   1244篇
  1988年   1175篇
  1987年   968篇
  1986年   861篇
  1985年   1138篇
  1984年   999篇
  1983年   687篇
  1982年   772篇
  1981年   661篇
  1980年   534篇
  1979年   411篇
  1978年   301篇
  1977年   235篇
  1976年   216篇
  1975年   82篇
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
51.
52.
Context: Protection of neurons from degeneration is an important preventive strategy for dementia. Much of the dementia pathology implicates oxidative stress pathways. Turmeric (Curcuma longa L.) contains curcuminoids which has anti-oxidative and neuro-protective effects. These effects are considered to be similar to those of citicoline which has been regularly used as one of standard medications for dementia.

Objective: This study aimed at investigating the effects of turmeric rhizome extract on the hippocampus of trimethyltin (TMT)-treated Sprague-Dawley rats.

Materials and methods: The rats were divided randomly into six groups, i.e., a normal control group (N); Sn group, which was given TMT chloride; Sn-Cit group, which was treated with citicoline and TMT chloride; and three Sn-TE groups, which were treated with three different dosages of turmeric rhizome extract and TMT chloride. Morris water maze test was carried out to examine the spatial memory. The estimated total number of CA1 and CA2–CA3 pyramidal cells was calculated using a stereological method.

Results: The administration of turmeric extract at a dose of 200?mg/kg bw has been shown to prevent the deficits in the spatial memory performance and partially inhibit the reduction of the number of CA2–CA3 regions pyramidal neurons.

Discussion: TMT-induced neurotoxic damage seemed to be mediated by the generation of reactive oxygen species and reactive nitrogen species. Turmeric extract might act as anti inflammatory as well as anti-oxidant agent.

Conclusions: The effects of turmeric extract at a dose of 200?mg/kg bw seem to be comparable to those of citicoline.  相似文献   
53.
Nodular basal cell carcinoma is a deep skin lesion and one of the most common cancers. Conventional photodynamic therapy is limited to treatment of superficial skin lesions. The parenteral administration of near-IR preformed photosensitizers suffers from poor selectivity and may result in prolonged skin photosensitivity. Microneedles (MNs) can provide localized drug delivery to skin lesions. Intradermal delivery of the preformed near-IR photosensitizer; 5,10,15,20-tetrakis(2,6-difluoro-3-N-methylsulfamoylphenyl bacteriochlorin (Redaporfin?) using dissolving MN was successful in vitro and in vivo. MN demonstrated complete dissolution 30 min after skin application and showed sufficient mechanical strength to penetrate the skin to a depth of 450 μm. In vitro deposition studies illustrated that the drug was delivered and detected down to 5 mm in skin. In vivo biodistribution studies in athymic nude mice Crl:NU(NCr)-Foxn1nu showed both fast initial release and localized drug delivery. The MN-treated mice showed a progressive decrease in the fluorescence intensity at the application site over the 7-day experiment period, with the highest and lowest fluorescence intensities measured being 9.2 × 1010 ± 2.5 × 1010 and 3.8 × 109 ± 1.6 × 109 p/s, respectively. By day 7, there was some migration of fluorescence away from the site of initial MN application. However, the majority of the body surfaces showed fluorescence levels that were comparable to those seen in the negative control group. This work suggests utility for polymeric MN arrays in minimally invasive intradermal delivery to enhance photodynamic therapy of deep skin lesions.  相似文献   
54.
ObjectiveOsteopontin (OPN, Spp1) is a protein upregulated in white adipose tissue (WAT) of obese subjects. Deletion of OPN protects mice from high-fat diet-induced WAT inflammation and insulin resistance. However, the alterations mediated by loss of OPN in WAT before the obesogenic challenge have not yet been investigated. Therefore, we hypothesised that the lack of OPN might enhance the pro-adipogenic micro environment before obesity driven inflammation.MethodsOPN deficiency was tested in visceral (V) and subcutaneous (SC) WAT from WT and Spp1−/− female mice. Gene expression for hypoxia, inflammation and adipogenesis was checked in WT vs. Spp1−/− mice (n = 15). Adipocytes progenitor cells (APC) were isolated by fluorescence cell sorting and role of OPN deficiency in adipogenesis was investigated by cell images and RT-PCR.ResultsWe show that Spp1−/− maintained normal body and fat-pad weights, although hypoxia and inflammation markers were significantly reduced. In contrast, expression of genes involved in adipogenesis was increased in WAT from Spp1−/− mice. Strikingly, APC from Spp1−/− were diminished but differentiated more efficiently to adipocytes than those from control mice.ConclusionsAPC from SC-WAT of lean OPN-deficient mice display an enhanced capacity for differentiating to adipocytes. These alterations may explain the healthy expansion of WAT in the OPN-deficient model which is associated with reduced inflammation and insulin resistance.  相似文献   
55.
Pharmacokinetics and tissue distribution of crotonoside   总被引:1,自引:0,他引:1  
1.?Crotonoside is a bioactive ingredient from Croton Herba with a strong antitumour activity. This study aimed to develop a highly sensitive and selective high-performance liquid chromatography (HPLC) method to quantify crotonoside in biological samples for pharmacokinetics and distribution studies.

2.?Protein precipitation by perchloric acid was used to separate crotonoside from the biological samples, and the recovery rates for crotonoside and the internal standard (luteoloside) were >80%. All calibration curves examining the crotonoside levels in plasma and tissues were linear (all correlation coefficients >?0.99).

3.?The response to crotonoside appeared to be dose disproportional to the maximum plasma concentration and the area under the time–concentration curve in plasma over the range of 12.5–50.0?mg/kg, and crotonoside was highly distributed in tissues after intravenous administration. The highest crotonoside level was detected in the liver (28.79?±?14.96?μg/g), whereas crotonoside was undetected in the brain.  相似文献   
56.
Aims: To investigate the value of visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) in a cohort of a community’s residents who were diagnosed as pre-diabetes, and to evaluate the association of VAT and SAT with insulin resistance.

Methods: This study was based on cross-sectional analysis of data from 107 adults. VAT and SAT were assessed by computed tomography. Insulin resistance was defined by homeostasis model assessment of insulin resistance >2.69. The relationship of VAT and SAT with insulin resistance were examined by linear regression. Logistic regression was used to analyze the association of VAT and SAT with insulin resistance.

Results: A total of 87 subjects had VAT ≥100?cm2. Thirty-six out of 107 (33.6%) subjects were detected to have insulin resistance, 71 were normal (66.4%), and all had insulin resistance with VAT ≥100?cm2. VAT (r?=?0.378, p?r?=?0.357, p?p?=?.003), but that of SAT was lost.

Conclusion: Pre-diabetic subjects with insulin resistance had elevated levels of VAT. VAT was more strongly associated with insulin resistance than SAT in Chinese subjects with pre-diabetes.  相似文献   
57.
58.
Protein transduction domains (PTDs) have been shown to promote the delivery of therapeutic proteins or peptides into the living cells. In a previous study, we showed that the double mutant of TCTP-PTD 13, TCTP-PTD 13M2, was more effective in the delivery of insulin than the wild-type TCTP-PTD 13. In this study, we applied this approach to the nasal delivery of a different peptide, exendin-4, using as carriers, several modified TCTP-PTDs, such as TCTP-PTD 13M1, 13M2, and 13M3. Nasal co-administration of TCTP-PTD 13M2 with exendin-4 showed the highest exendin-4 uptake among the three analogs in normal rats, and also decreased blood glucose levels by 43.3% compared with that of exendin-4 alone and by 18.6% compared with that of exendin-4 plus TCTP-PTD 13 in diabetic mice. We also designed an additional covalently linked conjugate of TCTP-PTD 13M2 and exendin-4 and evaluated its hypoglycemic effect after subcutaneous or intranasal delivery. Subcutaneous administration of exendin-4 that its C-terminus is covalently linked to TCTP-PTD 13M2 showed hypoglycemic effect of 42.2% compared to that in untreated group, whereas intranasal delivery was not successful in diabetic mice. We conclude that a simple mixing TCTP-PTD 13M2 with peptide/protein drugs can be potentially a generally applicable approach for intranasal delivery into animals.  相似文献   
59.
目的构建体外百草枯(paraquat,PQ)细胞纤维化模型,观察PQ对A549细胞中解整合素-金属蛋白酶17(ADAM17)表达的影响,探讨ADAM17在PQ中毒致肺纤维化中的作用。方法体外培养A549细胞,分为正常对照组、不同浓度PQ组,应用CCK-8检测细胞活力,筛选PQ浓度和时间,显微镜下观察细胞形态,ELISA测定各组纤维化标志物I型胶原(type I collagen,Col I)和纤连蛋白(fibronectin,FN)的表达,建立细胞纤维化模型;免疫细胞化学检测A549细胞中ADAM17的分布情况,RT-PCR和Western blot分别半定量检测ADAM17 mRNA及蛋白水平的表达情况。结果(1)随着PQ浓度增加及作用时间延长,A549细胞活力呈下降趋势,差异有统计学意义(P〈0.05),呈剂量依赖性和时间依赖性。(2)正常的A549细胞融合呈铺路石样生长,排列比较紧密,经PQ诱导后细胞排列较松散,细胞间连接变疏松,部分细胞溶解、死亡。(3)ELISA显示,随PQ浓度增加,Col I和FN表达增强,差异有统计学意义(P〈0.05);随PQ时间延长,Col I和FN表达也逐渐增强,差异有统计学意义(P〈0.05),成功建立PQ细胞纤维化模型。(4)免疫细胞化学显示,ADAM17在A549细胞胞浆表达。(5)RT-PCR和Western blot表明,随着PQ浓度增加,ADAM17 mRNA及蛋白水平表达明显增加,差异有统计学意义(P〈0.05),以PQ 200 umol/L时最为明显。随着PQ作用时间延长,ADAM17 mRNA及蛋白表达水平也明显增加,差异有统计学意义(P〈0.05),在24 h达到高峰。结论百草枯可引起肺泡上皮细胞形态学改变,导致细胞损伤,成功建立细胞的纤维化模型,对A549细胞的毒性作用具有剂量和时间依赖性。ADAM17在PQ诱导的A549细胞中过表达,可能参与了百草枯诱导的肺纤维化过程。  相似文献   
60.
目的研究靶向下调上皮细胞黏附分子(ECAM)对结直肠癌干细胞增殖、侵袭及药物敏感性的影响。方法用肿瘤微球法从人结直肠癌细胞系LoVo中获取结直肠癌干细胞,用结直肠癌干细胞表面特殊标志物[ECAM和人类细胞分化抗原44(CD44)]对其进行鉴定并进行后续研究。用lipofectamine 2000脂质体介导完成转染,根据处理方法不同将细胞分为3组:实验组(ECAM抑制组),对照组(转染公共抑制剂lipofectamine 2000-抑制剂),空白组(不作任何处理),并进行培养,取3组对数期的细胞分别给予几个浓度(1,5,10,15,20,25,30,35,40,45,50 mg·L-1)伊立替康和几个浓度(50,100,150,200,250,300,350,400,450,500,550,600 mg·L-1)卡培他滨,继续培养。用实时荧光定量检测用药前后3组细胞中ECAM mRNA的表达水平,用噻唑蓝(MTT)法检测用药前后3组细胞的增殖能力和药物敏感性,用Transwell小室检测3组细胞的侵袭能力。结果在富集前后的LoVo细胞系中,EpCAM^+CD44^+双阳结直肠癌干细胞的百分率分别是0.95%,85.78%,与富集前比较差异均有统计学意义(均P<0.05)。空白组、对照组和实验组中EpCAM mRNA的表达水平分别为8.17±0.64,7.94±0.83,2.16±0.12,对照组和实验组与空白组比较,差异均有统计学意义(P<0.05,P<0.01);实验组与对照组比较,差异有统计学意义(P<0.05),说明3组细胞构建成功。空白组、对照组和实验组中侵袭细胞分别为79.22±5.25,80.12±4.89,31.23±2.36。对照组和实验组与空白组比较,差异均有统计学意义(P<0.05,P<0.01);实验组与对照组比较,差异有统计学意义(P<0.05)。空白组、对照组与实验组的伊立替康对结直肠癌干细胞的IC50分别为(20.25±4.35),(19.22±3.99),(10.24±2.04)mg·L-1;这3组的卡培他滨对结直肠癌干细胞的IC50分别为(320.13±23.65),(315.79±21.03),(250.22±15.45)mg·L-1,实验组与对照组比较,差异有统计学意义(P<0.05)。结论靶向下调ECAM可以有效地抑制结肠癌干细胞增殖及侵袭能力,同时增强其对药物的敏感性。  相似文献   
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