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   6536篇
  免费   471篇
  国内免费   123篇
耳鼻咽喉   41篇
儿科学   165篇
妇产科学   220篇
基础医学   804篇
口腔科学   172篇
临床医学   648篇
内科学   1299篇
皮肤病学   99篇
神经病学   395篇
特种医学   432篇
外科学   857篇
综合类   392篇
一般理论   2篇
预防医学   387篇
眼科学   116篇
药学   494篇
  4篇
中国医学   122篇
肿瘤学   481篇
  2023年   61篇
  2022年   128篇
  2021年   207篇
  2020年   117篇
  2019年   149篇
  2018年   225篇
  2017年   139篇
  2016年   140篇
  2015年   219篇
  2014年   264篇
  2013年   328篇
  2012年   481篇
  2011年   480篇
  2010年   314篇
  2009年   293篇
  2008年   351篇
  2007年   385篇
  2006年   339篇
  2005年   288篇
  2004年   246篇
  2003年   245篇
  2002年   215篇
  2001年   136篇
  2000年   151篇
  1999年   106篇
  1998年   82篇
  1997年   76篇
  1996年   67篇
  1995年   72篇
  1994年   63篇
  1993年   44篇
  1992年   66篇
  1991年   57篇
  1990年   43篇
  1989年   60篇
  1988年   59篇
  1987年   40篇
  1986年   43篇
  1985年   45篇
  1984年   38篇
  1983年   31篇
  1982年   32篇
  1981年   34篇
  1980年   23篇
  1979年   23篇
  1978年   19篇
  1977年   26篇
  1976年   20篇
  1975年   14篇
  1974年   10篇
排序方式: 共有7130条查询结果,搜索用时 15 毫秒
81.
Risk factors for wound infection after cholecystectomy.   总被引:3,自引:0,他引:3  
BACKGROUND AND PURPOSE: Surgical site infection (SSI) after cholecystectomy is a common problem. The aim of this study was to identify the possible risk factors for the development of SSI. METHODS: 545 consecutive patients who received open (125) or laparoscopic (420) cholecystectomy due to gallbladder disease during the years 1998 to 2000 were included in the study. Potential risk factors including clinical features, biochemical data, and operative types were analyzed by univariate and multivariate analysis. RESULTS: The overall incidence of SSI was 4.4% (24/545). The wound complication rate was significantly lower in the laparoscopic group than in the open group (1.4% vs 14.4%, respectively). Factors associated with SSI found by univariate analysis (p < 0.05) included age, gender, acute cholecystitis, white blood cell count, serum albumin, blood glucose and bilirubin level, type of surgery, operative time and positive bile culture. Stepwise logistic regression analysis showed that abnormal blood glucose [odds ratio (OR), 4.7; 95% confidence interval (CI), 1.6 to 13.5], positive bile culture (OR, 3.5; 95% CI, 1.2 to 10.4), and open cholecystectomy (OR, 4.3; 95% CI, 1.3 to 13.6) were the most significant predictors of SSI. CONCLUSION: Poor control of diabetes mellitus before surgery, positive bile culture and open cholecystectomy significantly increased the rate of SSI. These findings indicate that better control of diabetes mellitus, and appropriate selection of surgical procedure and antibiotic regimen in the management of high-risk patients may reduce the incidence of postoperative SSI.  相似文献   
82.
拉米夫定对不同中医证型的慢性乙型肝炎疗效辨析   总被引:2,自引:0,他引:2  
拉米夫定是一种有效的抗乙肝病毒药物,它对病毒的逆转录酶有明显的抑制作用,可抑制乙肝病毒的复制,降低血液和肝脏中的病毒数量,改善肝脏生化功能和组织学病变,从而提高患者生存质量。为进一步提高拉米夫定治疗慢性乙型肝炎的疗效,本文收集统计了近4年的80例相关病例,从中医辨证的角度,分析应用拉米夫定治疗不同证型的慢性乙型肝炎的疗效。现报告如下。1临床资料1·1一般资料收集本院肝炎科门诊慢性乙型肝炎患者80名,其中男性47名,女性33名,年龄17~64岁,平均35岁。诊断标准依据2000年全国传染病与寄生虫病学会和肝病学会修订的病毒性肝炎诊…  相似文献   
83.
Brain undergoes neurodegeneration when excess free radicals overwhelm antioxidative defense systems during senescence, head trauma and/or neurotoxic insults. A site-specific accumulation of ferrous citrate-iron complexes in the substantia nigra dopaminergic neurons could lead to exaggerated dopamine turnover, dopamine auto-oxidation, free radical generation, and oxidant stress. Eventually, this iron-catalyzed dopamine auto-oxidation results in the accumulation of neuromelanin, a progressive loss of nigral neurons, and the development of Parkinson's disease when brain dopamine depletion is greater than 80%. Emerging evidence indicates that free radicals such as hydroxyl radicals ((.-)OH) and nitric oxide ((.-)NO) may play opposite role in cell and animal models of parkinsonism. (.-)OH is a cytotoxic oxidant whereas oNO is an atypical neuroprotective antioxidant. (.-)NO and S-nitrosoglutathione (GSNO) protect nigral neurons against oxidative stress caused by 1-methyl-4-phenylpyridinium (MPP(+)), dopamine, ferrous citrate, hemoglobin, sodium nitroprusside and peroxynitrite. MPP(+), the toxic metabolite of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), increases the nigral uptake of iron complexes and dopamine overflow leading to the generation of (.-)OH, protein oxidation, lipid peroxidation, and associated retrograde degeneration. In addition to GSNO, MPP(+)-induced oxidative neurotoxicity can be prevented by antioxidants including selegiline, 7-nitroindazole, 17beta-estradiol, melatonin, alpha-phenyl-tert-butylnitrone and U78517F. Similar to selegiline, 7-nitroindazole is a MAO-B inhibitor, which blocks the bio-activation of MPTP and oxidative stress. Freshly prepared but not light exposed, (.-)NO-exhausted GSNO is about 100 times more potent than the classic antioxidant glutathione. Via S-nitrosylation, GSNO also inhibits proteolysis and cytotoxicity caused by caspases and HIV-1 protease. Furthermore, in addition to protection against serum deprivation stress, the induction of neuronal NOS1 in human cells increases tolerance to MPP(+)-induced neuro-toxicity since newly synthesized (.-)NO prevents apoptosis possibly through up-regulation of bcl-2 and down regulation of p66(shc). In conclusion, reactive oxygen species are unavoidable by-products of iron-catalyzed dopamine auto-oxidation, which can initiate lipid peroxidation, protein oxidation, DNA damage, and nigral loss, all of which can be prevented by endogenous and exogenous (.-)NO. Natural and man-made antioxidants can be employed as part of preventative or neuroprotective treatments in Parkinson's disease and perhaps dementia complexes as well. For achieving neuroprotection and neuro-rescue in early clinical parkinsonian stages, a cocktail therapy of multiple neuroprotective agents may be more effective than the current treatment with extremely high doses of a single antioxidative agent.  相似文献   
84.
The aim of this study was to explore the relationship between activity and psychopathology in adolescents. A total of 289 high school students completed the Symptom Check List-90-R (SCL-90-R) and Wender Utah Rating Scale (WURS) in December 1998. The WURS was used to measure the students' activity level and the SCL-90-R was used as a measure of general psychopathology. Forty-one students (14.18%) scored higher than 46, the cut-off point for differentiation of attention deficit hyperactivity disorder (ADHD) from the general population according to Ward's report, in the WURS (WURS(+)). The WURS(+) students scored significantly higher than the WURS(-) students in all the subscales of SCL-90-R. The prevalence rate of adolescent WURS(+) in this study is 14.18%. This result shows that ADHD adolescents have overlapping symptoms with depression.  相似文献   
85.
Neuroimaging: do we really need new contrast agents for MRI?   总被引:8,自引:0,他引:8  
The use of exogenous contrast media in magnetic resonance imaging of the brain has brought dramatic improvement in the sensitivity of detection and delineation of pathological structures, such as primary and metastatic brain tumors, inflammation and ischemia. Disruption of the blood brain barrier leads to accumulation of the intravenously injected contrast material in the extravascular space, leading to signal enhancement. Magnetic resonance angiography benefits from T(1)-shortening effects of contrast agent, improving small vessel depiction and providing vascular visualization even in situations of slow flow. High speed dynamic MRI after bolus injection of contrast media allows tracer kinetic modeling of cerebral perfusion. Progressive enhancement over serial post-contrast imaging allows modeling of vascular permeability and thus quantitative estimation of the severity of blood brain barrier disruption. With such an array of capabilities and ever improving technical abilities, it seems that the role of contrast agents in MR neuroimaging is established and the development of new agents may be superfluous. However, new agents are being developed with prolonged intravascular residence times, and with in-vivo binding of ever-increasing specificity. Intravascular, or blood pool, agents are likely to benefit magnetic resonance angiography of the carotid and cerebral vessels; future agents may allow the visualization of therapeutic drug delivery, the monitoring of, for example, gene expression, and the imaging evaluation of treatment efficacy. So while there is a substantial body of work that can be performed with currently available contrast agents, especially in conjunction with optimized image acquisition strategies, post processing, and mathematical analysis, there are still unrealized opportunities for novel contrast agent introduction, particularly those exploiting biological specificity. This article reviews the current use of contrast media in magnetic resonance neuroimaging, discusses some of the developing strategies for new applications of imaging with these agents and finally offers some views and indications for contrast agents currently under development, as well as some speculation on unsolved problems in neuroimaging, and opportunities for novel contrast agents.  相似文献   
86.
目的:比较不同提取方法制备的石菖蒲挥发油中的挥发性化学成分。方法:采用传统的水蒸气蒸馏提取挥发油,超临界流体萃取挥发油和顶空进样直接采集挥发性成分3种方法,对石菖蒲中的挥发性成分进行GC-MS分析。结果:顶空进样技术鉴定出44种挥发性化学成分;水蒸气蒸馏法可鉴定出23种挥发性化学成分;超临界流体萃取可鉴定出25种化合物,经GC-MS分析,水蒸气蒸馏法与粉末顶空进样有14种化合物相同,超临界流体萃取与粉末顶空进样有8种化合物相同,相对含量均有一定的差异。结论:顶空进样技术分析石菖蒲中挥发性成分更简单、快速、无溶剂残留并节省药材。  相似文献   
87.
目的探究青蒿治疗人急性髓系白血病(acute myeloid leukemia,AML)的作用机制。方法根据口服生物利用度(OB)和类药性(DL)从中药系统药理学技术平台(TCMSP)中筛选出青蒿的活性成分、作用靶点,在GeneCards数据库中寻找急性髓系白血病相关靶点,将青蒿作用靶点与AML相关靶点取交集,筛选出青蒿治疗AML的活性成分及作用靶点。借助Cytoscape 3.7.2软件,构建青蒿活性成分-作用靶点网络,选出关键化合物。通过String平台构建靶蛋白相互作用网络(PPI),选出关键靶点。通过DAVID在线分析平台,对靶点基因进行GO富集分析和KEGG代谢通路分析。结果从青蒿中筛选获得22个有效活性成分,104个作用靶点,与AML有关的作用靶点94个,关键靶点14个,通路涉及免疫调节、细胞凋亡、氧化应激等,这些作用通路可能是青蒿防治AML的活性途径。结论初步研究了青蒿治疗AML的作用机制,青蒿具有多成分、多靶点的特点,可以通过多个靶点、多条通路来发挥治疗AML的作用。  相似文献   
88.
以四年生红果期吉林人参的15个组织器官为材料,利用HPLC和香草醛-硫酸比色法分别测定15个组织器官中6种单体皂苷(人参皂苷Rg1,Re,Rb1,Rc,Rb2,Rd)和总皂苷含量;同时,利用实时荧光定量PCR测定15个组织器官中法尼基焦磷酸合成酶(farnesyl pyrophosphate synthase,FPS)、鲨烯合成酶(squalene synthase,SQS)、鲨烯环氧酶(squalene epoxidase,SQE)、氧化鲨烯环化酶(oxidized squalene cyclase,OSC)、β-香树脂合成酶(β-amyrin synthase,β-AS)和细胞色素P450超家族(cytochrome P450 family,P450)基因的相对表达量。研究试图通过相关性分析,获得吉林人参15个组织器官中人参皂苷含量与生物合成途径相关酶基因表达量之间相关关系。结果表明,6种单体皂苷含量之间具有线性正相关的协同增减趋势,而单体皂苷含量与总皂苷含量之间具有相关性极显著(P<0.01)的正相关关系;总皂苷含量与人参中SQS,OSC,β-AS,SQE,P450,FPS基因之间的相关性极显著(P<0.01),单体皂苷含量与6种酶基因之间相关性各不相同。说明这6种参与人参皂苷生物合成酶基因调控人参总皂苷与单体皂苷的生物合成,它们在人参不同组织器官中的表达呈现协同增减趋势,并以集群协调表达的方式来调控人参皂苷生物合成。  相似文献   
89.
The roots of Bupleurus spp. have been used in traditional Chinese herbal medicine for curing liver diseases. Although bioactive saikosaponins have been detected in the leaves as well as in the roots, the aerial parts of the plants are discarded as waste. In the present study, a leaf infusion of B. kaoi Liu, Chao et Chuang, an indigenous Bupleurus species in Taiwan, was prepared and the antioxidant properties and in vitro hepatoprotective activity were demonstrated. The results show that the leaf infusion exerted DPPH free radical scavenging activity, inhibitory capacity on superoxide anion formation and superoxide anion scavenging activity. The hepatotoxicity of acetaminophen (APAP) and carbon tetrachloride (CCl4) on the rat liver cells were also decreased by the leaf infusion.  相似文献   
90.
Abstract

To investigate the influence of irisin on endometrial receptivity of rats with polycystic ovarian syndrome (PCOS). PCOS rats were randomly divided into PCOS group and irisin group, and normal rats were used as control group. The PCOS group and control group were injected intraperitoneally with normal saline while the irisin group with recombinant irisin. The serum and uterus were obtained. Detect serum sex hormones, including Testosterone (T), Estradiol (E2), Progesterone (P), and glucose, insulin levels. Observe endometrial morphology by hematoxylin-eosin staining. Then evaluate the expression of leukemia inhibitory factor (LIF) and integrin αvβ3 in endometrium using ELISA, immunohistochemistry and Real-time PCR. (1) Levels of serum T, glucose and insulin in PCOS group were significantly higher than those in control and irisin group. (2) For the endometrial morphology, levels of equivalent diameter, area of uterine glands and gland cavity and endometrial average thickness were lower in PCOS group than those in control and irisin group. (3) LIF and integrin αvβ3 mRNA were basically consistent with protein expression. Levels of LIF and integrin αvβ3 were decreased in PCOS group when compared with control and irisin group. Irisin may improve endometrial receptivity by promoting expression of LIF and integrin αvβ3.  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