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   5458篇
  免费   278篇
  国内免费   228篇
耳鼻咽喉   18篇
儿科学   67篇
妇产科学   20篇
基础医学   761篇
口腔科学   47篇
临床医学   403篇
内科学   1037篇
皮肤病学   73篇
神经病学   680篇
特种医学   97篇
外科学   249篇
综合类   666篇
预防医学   86篇
眼科学   43篇
药学   1346篇
中国医学   244篇
肿瘤学   127篇
  2023年   51篇
  2022年   78篇
  2021年   118篇
  2020年   106篇
  2019年   116篇
  2018年   126篇
  2017年   109篇
  2016年   103篇
  2015年   128篇
  2014年   268篇
  2013年   333篇
  2012年   249篇
  2011年   303篇
  2010年   273篇
  2009年   245篇
  2008年   284篇
  2007年   256篇
  2006年   226篇
  2005年   205篇
  2004年   192篇
  2003年   168篇
  2002年   143篇
  2001年   138篇
  2000年   116篇
  1999年   117篇
  1998年   114篇
  1997年   104篇
  1996年   76篇
  1995年   84篇
  1994年   82篇
  1993年   98篇
  1992年   54篇
  1991年   60篇
  1990年   70篇
  1989年   62篇
  1988年   40篇
  1987年   43篇
  1986年   46篇
  1985年   82篇
  1984年   77篇
  1983年   68篇
  1982年   65篇
  1981年   73篇
  1980年   59篇
  1979年   43篇
  1978年   50篇
  1977年   23篇
  1976年   22篇
  1974年   4篇
  1973年   4篇
排序方式: 共有5964条查询结果,搜索用时 17 毫秒
1.
2.
BackgroundIschemia reperfusion (I/R) play an imperative role in the expansion of cardiovascular disease. Sinomenine (SM) has been exhibited to possess antioxidant, anticancer, anti-inflammatory, antiviral and anticarcinogenic properties. The aim of the study was scrutinized the cardioprotective effect of SM against I/R injury in rat.MethodsRat were randomly divided into normal control (NC), I/R control and I/R + SM (5, 10 and 20 mg/kg), respectively. Ventricular arrhythmias, body weight and heart weight were estimated. Antioxidant, inflammatory cytokines, inflammatory mediators and plasmin system indicator were accessed.ResultsPre-treated SM group rats exhibited the reduction in the duration and incidence of ventricular fibrillation, ventricular ectopic beat (VEB) and ventricular tachycardia along with suppression of arrhythmia score during the ischemia (30 and 120 min). SM treated rats significantly (P < 0.001) altered the level of antioxidant parameters. SM treatment significantly (P < 0.001) repressed the level of creatine kinase MB (CK-MB), creatine kinase (CK) and troponin I (Tnl). SM treated rats significantly (P < 0.001) repressed the tissue factor (TF), thromboxane B2 (TXB2), plasminogen activator inhibitor 1 (PAI-1) and plasma fibrinogen (Fbg) and inflammatory cytokines and inflammatory mediators.ConclusionOur result clearly indicated that SM plays anti-arrhythmia effect in I/R injury in the rats via alteration of oxidative stress and inflammatory reaction.  相似文献   
3.
Melatonin is a neurohormone secreted principally by the pineal gland. This molecule has various pharmacological properties including improving immune system, prevent cancer, anti-aging, and anti-oxidant effects. The anticonvulsant effects of melatonin have been proved by previous studies. Adenosine triphosphate (ATP)-sensitive potassium (KATP) channels are considered as an important target in the seizure modulation. The aim of the present study was to investigate the anticonvulsant effect of melatonin in pentylenetetrazole (PTZ)-induced seizures in mice, focusing on its ability to regulate KATP channels. Acute intraperitoneal administration of melatonin (40 and 80 mg/kg) increased clonic seizure threshold induced by intravenous administration of PTZ. Melatonin (40 and 80 mg/kg) increased the latency of clonic seizure and reduced its frequency in mice receiving an intraperitoneal injection of PTZ. Administration of glibenclamide, a KATP channels blocker, before intravenous injection of PTZ reduced melatonin anticonvulsant effect. Diazoxide and cromakalim, as KATP channels openers, increased antiseizure effect of melatonin in PTZ model of seizures. These findings suggest that the antiseizure effect of melatonin probably is gained through increasing the opening of KATP channels.  相似文献   
4.
5.
枳实薤白桂枝汤HPLC指纹图谱及10种指标成分含量测定研究   总被引:3,自引:0,他引:3  
袁海建  李卫  祝一飞  张光际  封亮  贾晓斌  王卉  周涛 《中草药》2020,51(9):2448-2459
目的建立枳实薤白桂枝汤HPLC指纹图谱分析方法和复方中10种指标成分(辛弗林、槲皮素、桂皮酸、厚朴酚、柚皮苷、腺苷、香豆素、橙皮苷、和厚朴酚、新橙皮苷)含量测定方法,开展相关评价分析。方法采用HPLC法建立枳实薤白桂枝汤指纹图谱,开展相似度评价研究;测定复方中10个指标成分,分析复方中药材不同配伍对其量的变化影响;采用聚类分析等化学计量学方法,对获取相关数据进行分析,评价枳实薤白桂枝汤的质量控制相关指标的影响和价值。结果 10批样品的相似度在0.376~0.990,部分批次相似度大于0.9(5批),说明10批样品相似度差异较大。10批样品中S1~S3、S5、S6、S8、S10为一组,S4、S9为一组,S7单独为一组。共标定了30个特征峰,经主成分分析,主成分1~6是影响药材样品质量评价的主要因子;30个特征峰中对样品分组起关键作用的成分为21(新橙皮苷)、26、29(和厚朴酚)、3、23、17、30(厚朴酚)、5、24(香豆素)、28和7。含量测定结果显示,除槲皮素外,其余9种成分在测定的质量浓度范围内线性关系、精密度、稳定性和重复性良好;不同配伍会对药材中相关成分产生增加或抑制溶出的作用。结论所建立的HPLC方法可用于同时测定枳实薤白桂枝汤中10种化学成分的含量,该方法高效、准确、重复性好,可用于枳实薤白桂枝汤的质量控制和评价。  相似文献   
6.
We performed a caffeine (N-3-methyl-13C) breath test (CafeBT) to determine whether it can be employed to identify caffeine metabolism-associated single nucleotide polymorphisms. The study included 130 healthy adults (mean age: 21.9 years). Saliva was collected using an Oragene®•DNA saliva collection kit. Breath samples were collected from the subjects. The subjects orally ingested 100 mg 13C-caffeine dissolved in distilled water. Subsequently, breath samples were collected in bags every 10 min for a total of 90 min. An analysis of 13CO2 in the expired breath was performed by infrared spectroscopy, and the sum of Δ13CO2 over 90 min (S90m) was calculated. DNA from saliva samples was genotyped using TaqMan® SNP Genotyping for the following genes: cytochrome P4501A2: rs762551, rs2472297, aryl-hydrocarbon receptor (rs4410790), and adenosine A2A receptor (rs5751876). All subjects had the genotype CC in rs2472297 alleles. No significant difference was observed in S90m among the genotypes of rs762551 and rs5751876; however, a significant difference was found in S90m among the genotypes of rs4410790 (C > T). Our findings suggest that the N-3 demethylation of caffeine is dependent on the rs4410790 allele and that CafeBT may be used to determine rs4410790 genotypes.  相似文献   
7.
目的:完善金水宝胶囊生产过程中的质量控制体系,为该制剂的后续研究与应用提供实验依据。方法:采用高效液相色谱法(HPLC),Ultimate AQ-C18色谱柱(4.6 mm×150 mm,5μm),腺苷、鸟苷、尿苷含量测定的色谱条件为流动相甲醇(A)-0.1%甲酸水溶液(B)梯度洗脱(0~14 min,100%~99%B;14~19 min,99%~89%B;19~39 min,89%~85%B),流速0.4 m L·min^-1,柱温30℃,进样量10μL,检测波长260 nm。麦角甾醇含量测定的色谱条件为流动相甲醇-水(98∶2),流速1 m L·min^-1,柱温25℃,进样量10μL,检测波长283 nm。结果:发酵虫草菌粉不同生产阶段样品的指纹图谱中主要色谱峰差异性较小。腺苷、鸟苷、尿苷的线性关系良好(R2均>0.999);三者的加样回收率分别为106.06%,101.25%,105.88%,RSD均<3.0%。于2016-2018年各抽取的20批样品中腺苷、麦角甾醇的含量均符合2015年版《中国药典》的要求,鸟苷、尿苷的质量分别为0.97~1.36,0.67~1.38 mg/粒。结论:市面所售金水宝胶囊质量较为稳定。建立的方法可用于检测金水宝胶囊的质量,且操作简便、稳定可靠,可为发酵虫草菌粉类产品的检测提供参考。  相似文献   
8.
Background: Cellular metabolism generates reactive oxygen species. The oxidation and deamination of the deoxynucleoside triphosphate (dNTP) pool results in the formation of non-canonical, toxic dNTPs that can cause mutations, genome instability, and cell death. House-cleaning or sanitation enzymes that break down and detoxify non-canonical nucleotides play major protective roles in nucleotide metabolism and constitute key drug targets for cancer and various pathogens. We hypothesized that owing to their protective roles in nucleotide metabolism, these house-cleaning enzymes are key drug targets in the malaria parasite.

Methods: Using the rodent malaria parasite Plasmodium berghei we evaluate here, by gene targeting, a group of conserved proteins with a putative function in the detoxification of non-canonical nucleotides as potential antimalarial drug targets: they are inosine triphosphate pyrophosphatase (ITPase), deoxyuridine triphosphate pyrophosphatase (dUTPase) and two NuDiX hydroxylases, the diadenosine tetraphosphate (Ap4A) hydrolase and the nucleoside triphosphate hydrolase (NDH).

Results: While all four proteins are expressed constitutively across the intraerythrocytic developmental cycle, neither ITPase nor NDH are required for parasite viability. dutpase and ap4ah null mutants, on the other hand, are not viable suggesting an essential function for these proteins for the malaria parasite.

Conclusions: Plasmodium dUTPase and Ap4A could be drug targets in the malaria parasite.  相似文献   

9.
New conjugates of mycophenolic acid (MPA) and adenosine derivatives were synthesized and assessed as potential immunosuppressants on Jurkat cell line and peripheral blood mononuclear cells (PBMC) from healthy donors. As compared to MPA, all compounds were found to be more active against Jurkat cell line. The antiproliferative activities were compared with MPA and adenosine, in both 2′,3′-O-isopropylidene protected and free hydroxyl groups possessing forms. The obtained results were also discussed in terms of selectivity index, defined as SI = IC50/EC50.  相似文献   
10.
《Vaccine》2019,37(35):4963-4974
Vaccination is the most efficient strategy to protect from infectious diseases and the induction of a protective immune response not only depends on the nature of the antigen, but is also influenced by the vaccination strategy and the co-administration of adjuvants. Therefore, the precise monitoring of adjuvant candidates and their immune modulatory properties is a crucial step in vaccine development. Here, one central aspect is the induction of appropriate humoral and cellular effector mechanisms.In our study we performed a direct comparison of two promising candidates in adjuvant development, the STING activator bis-(3,5)-cyclic dimeric adenosine monophosphate (c-di-AMP) and the Toll-like receptor ligand formulation poly(I:C)/CpG. These were evaluated in C57BL/6 mice using the model antigen ovalbumin (OVA) in subcutaneous vaccination with soluble protein as well as in a dendritic cell (DC) targeting approach (αDEC-OVA). Strikingly, c-di-AMP as compared to poly(I:C)/CpG resulted in significantly higher antigen-specific IgG antibody levels when used in immunization with soluble OVA as well as in antigen targeting to DC. In vaccination with soluble OVA, c-di-AMP induced a significantly stronger CTL, Th1 and IFNγ-producing CD8+ memory T cell response than poly(I:C)/CpG. The response was CTL and Th1 cell dominated, a profile shared by both adjuvants. In the context of targeting OVA to DC, c-di-AMP induced significantly increased Th1 and Th2 cell responses as compared to poly(I:C)/CpG. Interestingly, the Th1 response dominated the overall T cell response only when c-di-AMP was used, indicating a distinct modulatory property of c-di-AMP when the DC targeting immunization approach was exploited.Taken together, we describe superior properties of c-di-AMP as compared to poly(I:C)/CpG in subcutaneous vaccination with soluble antigen as well as antigen targeting to DC. This indicates exceptionally effective adjuvant properties for c-di-AMP and provides compelling evidence of its potential for further adjuvant development, especially also when using DC targeting approaches.  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