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   9695篇
  免费   768篇
  国内免费   296篇
耳鼻咽喉   63篇
儿科学   55篇
妇产科学   34篇
基础医学   1670篇
口腔科学   247篇
临床医学   565篇
内科学   1546篇
皮肤病学   83篇
神经病学   561篇
特种医学   234篇
外科学   419篇
综合类   1329篇
预防医学   860篇
眼科学   128篇
药学   2159篇
  8篇
中国医学   637篇
肿瘤学   161篇
  2024年   7篇
  2023年   126篇
  2022年   189篇
  2021年   438篇
  2020年   314篇
  2019年   262篇
  2018年   226篇
  2017年   287篇
  2016年   304篇
  2015年   378篇
  2014年   546篇
  2013年   728篇
  2012年   606篇
  2011年   620篇
  2010年   498篇
  2009年   531篇
  2008年   525篇
  2007年   460篇
  2006年   403篇
  2005年   400篇
  2004年   314篇
  2003年   299篇
  2002年   227篇
  2001年   209篇
  2000年   190篇
  1999年   190篇
  1998年   145篇
  1997年   118篇
  1996年   128篇
  1995年   92篇
  1994年   95篇
  1993年   86篇
  1992年   73篇
  1991年   79篇
  1990年   65篇
  1989年   76篇
  1988年   71篇
  1987年   57篇
  1986年   57篇
  1985年   54篇
  1984年   61篇
  1983年   43篇
  1982年   45篇
  1981年   28篇
  1980年   29篇
  1979年   20篇
  1978年   18篇
  1977年   11篇
  1976年   11篇
  1973年   6篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
目前在中医界已发布的冠心病痰湿证辨证标准是以主症、次症形式定性地给出,存在主观性较强的问题。本文引入约束隐结构分析,该方法将主症、次症的语义作为约束条件加入隐结构分析过程,得到含有主症、次症语义约束的定量化中医证候辨证规则。使用该方法对冠心病痰湿证患者556条无标签数据的分析,得到其约束隐结构模型,最后建立定量化痰湿证辨证规则,舌胖边有齿痕(3.16)、苔腻(3.12)、苔白滑(4.72)、胸闷(1.73)、脉濡或滑(6.04);次症:肢体困重(0.48)、口黏(0.63)、体胖(0.49)、大便粘滞(1.38)、脘腹痞满(0.97)、面色晦浊(0.79)、嗜睡(1.18)、纳差(1.07)。与经典隐结构模型得到规则和中医界已发布的定性化辨证规则相比,约束隐结构得到的规则客观性强,具有可重复性。在证候类大小、规则的量化合理度上较好地反映了主症、次症的特点,得到的规则切合中医实际,为冠心病痰湿证辨证标准的定量化研究提供帮助和参考。  相似文献   
2.
Intervertebral disc disease (IVDD) is a common musculoskeletal disease affecting about 5% of all individuals. It is characterized by lumbar disc herniation, which causes nerve root irritation, either mechanically or via inflammatory mediators, and results in radiating pain, known as sciatica. Numerous studies have been conducted to identify the causes and risk factors for IVDD. Lifting heavy loads, torsional stress, and motor vehicle driving are among the best-identified environmental risk factors. However, it has become evident recently from family and twin studies that genetic factors may also be important in IVDD. This hypothesis was strengthened by the identification of two collagen IX alleles associated with sciatica and lumbar disc herniation. In addition, disc degeneration has been shown to be related to an aggrecan gene polymorphism, a Vitamin D receptor and matrix metalloproteinase-3 gene alleles. This review highlights the genetic role and occupational aspects of IVDD.  相似文献   
3.
Researchers continue to lament the lack of organisational focus in the sociology of health and illness. Although studies have increasingly focused on boundaries between organizations, little such research has focused on the formal boundaries within the hospital itself. Given its dramatic compartmentalisation, and continuing prevalence in health systems, the lack of organisational perspective in hospital research limits insights into the effects (as well as the construction) of the order of health work and care. With a greater emphasis on ‘ordering’ in the concept of negotiated order, the aim of this study is to examine the manifestation and consequences of the formal boundaries of hospital departments. Fieldwork featured 12 months of ethnography, including formal and informal observations, 80 audio‐recorded, semi‐structured interviews, and 56 field interviews, in the Emergency Departments (EDs) of two tertiary referral hospitals. Compared with in‐patient hospital departments, the ED has limited legitimacy claims of organ‐specific knowledge to transfer patients out of the ED. The manifestation of specialised knowledge hierarchies in organisational structures disadvantages patients who are older and who have chronic conditions, underpinning the argument that effects as well as the negotiation of stable organisational orders deserve increased attention in the sociology of health and illness.  相似文献   
4.
目的 探讨以行为-结构化-关系(BSR)干预模式对短期住院孤独症谱系障碍(ASD)儿童的干预疗效,为改善ASD儿童的预后提供参考依据。方法 选取2015年12月-2016年12月确诊为ASD的2~6岁儿童141例,随机分为治疗组和对照组。治疗组ASD儿童均接受BSR模式的短期课程训练,训练课程包括个别辅导、游戏课、运动课、音乐课等,每天训练时间6 h,持续1个月;对照组ASD儿童处于干预等待,接受随访观察和评估。所有ASD儿童干预前、后均接受儿童心理教育评估(第三版)(PEP-3)来进行各方面能力变化的评估。结果 治疗组、对照组干预前各副测验的原积分差异无统计学意义(P>0.05)。两组ASD儿童干预后认知、语言理解、模仿、情感表达、社会互动、行为特征-非语言、适应行为的原积分比较,差异均有统计学意义(t=2.41、2.02、4.14、3.69、4.42、2.69、2.96,P<0.05);但小肌肉、大肌肉、自理的原积分比较,差异无统计学意义(t=-1.13、-1.05、-0.84,P>0.05)。结论 BSR干预模式能够有效改善短期住院ASD儿童的预后,可推广用于儿童ASD的治疗。  相似文献   
5.
The purpose of this study was to compare acoustic structure quantification (ASQ) with transient elastography for staging liver fibrosis. One hundred eighty-two patients with chronic hepatitis B and without moderate to severe hepatic steatosis scheduled for liver biopsy underwent ASQ and transient elastography examinations. All ASQ parameters, including total mode, total average, red mode, red average, red standard deviation, blue mode, blue average, blue standard deviation and focal disturbance (FD) ratio and liver stiffness obtained via transient elastography were found to correlate with fibrosis stage (Spearman's r?=?0.783, 0.791, 0.750, 0.771, 0.544, 0.718, 0.691, 0.439, 0.815 and 0.814, respectively; all p values < 0.001). Among the ASQ parameters, the FD ratio had the highest correlation with the stage of fibrosis. The areas under the receiver operating characteristic curves (AUCs) of FD ratio and liver stiffness were 0.911 and 0.906 for F ≥ F1, 0.918 and 0.882 for F ≥ F2, 0.911 and 0.914 for F ≥ F3 and 0.926 and 0.978 for F?=?F4, respectively. There was no significant difference in AUCs between FD ratio and liver stiffness in predicting different stages of fibrosis (p?=?0.062–0.912). ASQ is a promising technique for assessing liver fibrosis in the absence of moderate to severe hepatic steatosis.  相似文献   
6.
Cocrystallization and salt formation were used to produce new multicomponent forms of a novel antimalarial imidazopyridazine drug lead (MMV652103) that displayed improved physicochemical properties. The drug lead had earlier shown good in vitro potency against multidrug resistant (K1) and sensitive (NF54) strains of the human malaria parasite Plasmodium falciparum, and high in vivo efficacy in both Plasmodium berghei and Plasmodium falciparum mouse models. A major drawback of MMV652103 is its limited aqueous solubility. Various new supramolecular products, including several multicomponent solid forms, are reported here, namely 3 cocrystal forms with the dicarboxylic acid coformers adipic acid, glutaric acid, and fumaric acid, and a salt form with malonic acid. These were characterized by thermal methods and their structures elucidated by single-crystal X-ray diffraction. A customized solubility experiment was performed in fasted-state simulated intestinal fluid for comparison of the solubility behavior of each new form of the drug lead with that of the untreated starting material. All of the multicomponent forms showed an improvement in the maximum concentrations (Cmax) attained by the drug lead and the rate at which it dissolved. The recorded Cmax values exceeded the concentration of the untreated compound by factors in the range 4.6-5.6.  相似文献   
7.
We previously found that circulating β2‐glycoprotein I inhibits human endothelial cell migration, proliferation, and angiogenesis by diverse mechanisms. In the present study, we investigated the antitumor activities of β2‐glycoprotein I using structure‐function analysis and mapped the critical region within the β2‐glycoprotein I peptide sequence that mediates anticancer effects. We constructed recombinant cDNA and purified different β2‐glycoprotein I polypeptide domains using a baculovirus expression system. We found that purified β2‐glycoprotein I, as well as recombinant β2‐glycoprotein I full‐length (D12345), polypeptide domains I‐IV (D1234), and polypeptide domain I (D1) significantly inhibited melanoma cell migration, proliferation and invasion. Western blot analyses were used to determine the dysregulated expression of proteins essential for intracellular signaling pathways in B16‐F10 treated with β2‐glycoprotein I and variant recombinant polypeptides. Using a melanoma mouse model, we found that D1 polypeptide showed stronger potency in suppressing tumor growth. Structural analysis showed that fragments A and B within domain I would be the critical regions responsible for antitumor activity. Annexin A2 was identified as the counterpart molecule for β2‐glycoprotein I by immunofluorescence and coimmunoprecipitation assays. Interaction between specific amino acids of β2‐glycoprotein I D1 and annexin A2 was later evaluated by the molecular docking approach. Moreover, five amino acid residues were selected from fragments A and B for functional evaluation using site‐directed mutagenesis, and P11A, M42A, and I55P mutations were shown to disrupt the anti‐melanoma cell migration ability of β2‐glycoprotein I. This is the first study to show the therapeutic potential of β2‐glycoprotein I D1 in the treatment of melanoma progression.  相似文献   
8.
9.
目的:研究临泉产穿心莲地上部分黄酮类化学成分。方法:利用硅胶、凝胶Sephadex LH-20、ODS柱色谱等方法,对临泉产穿心莲地上部分90%乙醇提取物的化学成分进行分离和纯化,运用波谱学技术对分离得到的单体化合物进行结构鉴定。结果:从穿心莲的乙醇提取物中分离并鉴定出14个黄酮类化合物,分别是双氢汉黄芩素(1)、5-羟基-6,7-二甲氧基黄酮(2)、2-羟基-3,4,6-三甲氧基查尔酮(3)、5-羟基-7,8-二甲氧基黄酮(4)、穿心莲素(5)、5-羟基-7,8,2',5'-四甲氧基黄酮(6)、5,7,8-三甲氧基二氢黄酮(7)、2'-甲氧基-5,6,7-三甲基黄芩素(8)、5,7,4'-三甲氧基黄酮(9)、高车前素(10)、7,8,2',5'-四甲氧基黄酮-5-O-β-D-吡喃葡萄糖苷(11)、穿心莲黄酮苷A(12)、穿心莲黄酮苷C(13)、穿心莲黄酮苷G(14)。结论:其中化合物1、2、3、8首次从穿心莲中分离得到。  相似文献   
10.
目的:利用简单序列重复区间扩增多态性(ISSR)分子标记技术对江西省锐尖山香圆进行亲缘关系和遗传结构分析,为该药材资源的保护和利用提供理论依据。方法:采集江西省4个县6个采样地的22份锐尖山香圆叶片样本,利用试剂盒法提取基因组DNA。利用64条通用ISSR分子标记引物进行聚合酶链式反应(PCR)扩增,运用聚丙烯酰胺凝胶电泳(PAGE)方法检测条带。选择NTsys 2. 10e软件,采用非加权配对算术平均法(UPGMA)计算遗传相似系数并聚类分析。利用Structure 2. 1软件分析群体遗传结构。结果:有48条ISSR引物扩增后获得了产物,多态性条带百分率处于45. 45%~100%。UPGMA聚类分析表明4个县的锐尖山香圆资源不能按照行政区域划分分别聚为一类,群体遗传结构分析表明22份锐尖山香圆群体可以划分为3个类群。结论:江西省锐尖山香圆群体间存在着基因交流,会影响该药材不同地理来源种质资源的遗传结构组成。  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