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   1046篇
  免费   92篇
  国内免费   19篇
儿科学   77篇
妇产科学   4篇
基础医学   131篇
口腔科学   63篇
临床医学   119篇
内科学   185篇
皮肤病学   47篇
神经病学   29篇
特种医学   241篇
外科学   77篇
综合类   29篇
预防医学   49篇
眼科学   13篇
药学   30篇
  1篇
肿瘤学   62篇
  2023年   3篇
  2022年   3篇
  2021年   5篇
  2020年   9篇
  2019年   8篇
  2018年   14篇
  2017年   7篇
  2016年   13篇
  2015年   27篇
  2014年   23篇
  2013年   42篇
  2012年   22篇
  2011年   21篇
  2010年   54篇
  2009年   52篇
  2008年   23篇
  2007年   34篇
  2006年   25篇
  2005年   27篇
  2004年   15篇
  2003年   26篇
  2002年   20篇
  2001年   15篇
  2000年   5篇
  1999年   22篇
  1998年   81篇
  1997年   76篇
  1996年   59篇
  1995年   52篇
  1994年   37篇
  1993年   45篇
  1992年   7篇
  1991年   23篇
  1990年   14篇
  1989年   42篇
  1988年   35篇
  1987年   25篇
  1986年   18篇
  1985年   18篇
  1984年   9篇
  1983年   12篇
  1982年   14篇
  1981年   14篇
  1980年   15篇
  1979年   3篇
  1978年   13篇
  1977年   11篇
  1976年   10篇
  1975年   8篇
  1954年   1篇
排序方式: 共有1157条查询结果,搜索用时 11 毫秒
31.
Objectives: To describe the physical growth patterns of infants born to narcotic dependent mothers (INDM) over a 12 months period and, if possible, to relate the growth to drug taking patterns during pregnancy.
Methodology: The growth of a cohort of 43 INDM was measured during the first 12 months of life. Weight and length measurements were compared with percentile charts and converted to Z scores. Questionnaire data about drug taking practices, demographic variables and the neonatal period (including withdrawal scores) were obtained.
Results: Twenty-four (55.8%) of INDM had evidence of neonatal drug withdrawal requiring treatment with phenobarbitone. At birth, Z scores for weight and length indicated relative intrauterine growth retardation. By 12 months, there had been some catch up growth, but Z scores for weight and length were still below zero. Persistent weight retardation at 12 months was correlated with methadone dosage during pregnancy, but not the need for phenobarbitone therapy.
Conclusions: The growth patterns of INDM in the first 12 months of life indicated that at birth there was evidence of intrauterine growth retardation, but by 12 months the growth was little different from the rest of the community. There appears to be some influence of narcotic agents taken while pregnant on subsequent growth of INDM.  相似文献   
32.
33.
Aflatoxin B1 (AFB1), a mutagen and hepatocarcinogen in rats and humans, is a contaminant of the human food supply, particularly in parts of Africa and Asia. AFB1-induced changes in gene expression may play a part in the development of the toxic, immunosuppressive and carcinogenic properties of this fungal metabolite. An understanding of the-role of AFB1 in modulating gene regulation should provide insight regarding mechanisms of AFB1-induced carcinogenesis. We used three PCR- based subtractive techniques to identify AFB1-responsive genes in cultured primary rat hepatocyte RNA: differential display PCR (DD-PCR), representational difference analysis (RDA) and suppression subtractive hybridization (SSH). Each of the three techniques identified AFB1- responsive genes, although no individual cDNA was isolated by more than one technique. Nine cDNAs isolated using DD-PCR, RDA or SSH were found to represent eight genes that are differentially expressed as a result of AFB1 exposure. Genes whose mRNA levels were increased in cultured primary rat hepatocytes after AFB1 treatment were corticosteroid binding globulin (CBG), cytochrome P450 4F1 (CYP4F1), alpha-2 microglobulin, C4b-binding protein (C4BP), serum amyloid A-2 and glutathione S-transferase Yb2 (GST). Transferrin and a small CYP3A-like cDNA had reduced mRNA levels after AFB1 exposure. Full-length CYP3A mRNA levels were increased. When liver RNA from AFB1-treated male F344 rats was evaluated for transferrin, CBG, GST, CYP3A and CYP4F1 expression, a decrease in transferrin mRNA and an increase in CBG, GST, CYP3A and CYP4F1 mRNA levels was also seen. Analysis of the potential function of these genes in maintaining cellular homeostasis suggests that their differential expression could contribute to the toxicity associated with AFB1 exposure.   相似文献   
34.
目的研究选择性头部降温对缺血性脑损伤胎羊纹状体神经元凋亡和星形胶质细胞增殖的影响。方法胎羊于妊娠117~124d时通过双侧颈动脉阻塞30min造成双侧脑缺血损伤,损伤后将胎羊随机分为:损伤组(n=10)、2h低温组(损伤后2h开始亚低温治疗,n=7)和6h低温组(损伤后6h开始亚低温治疗,n=8),另设正常对照组(n=5)。通过冷循环水进行选择性头部降温,取脑组织用免疫组化法检测胎羊纹状体caspase-3(半胱天冬氨酸酶-3),GFAP(胶质纤维酸性蛋白)和PCNA(增殖细胞核抗原)的表达。结果①纹状体神经元凋亡:正常对照组中,caspase-3表达极少(11.00±13.77),损伤组caspase-3免疫阳性细胞为177.70±48.69,明显增加(P=0.000),损伤后2h治疗组(54.14±39.44,P=0.000)和损伤后6h治疗组(122.43±52.36,P=0.017)均能减少caspase-3免疫阳性细胞。②纹状体星形胶质细胞增殖:与正常对照组(163.40±21.98)相比,缺血性脑损伤组的GFAP免疫阳性细胞明显增多(433.25±66.69,P=0.000),损伤后2h开始亚低温治疗(219.50±35.31,P=0.000)和损伤后6h开始亚低温治疗(272.50±86.20,P=0.000)均能减少GFAP免疫阳性细胞。③纹状体PCNA阳性细胞的表达:在正常对照组中,PCNA免疫阳性细胞较少,为153.40±12.46,缺血性脑损伤组的PCNA免疫阳性细胞明显增多(353.70±45.60,P=0.000),损伤后2h开始亚低温治疗(187.14±26.26,P=0.000)和损伤后6h开始亚低温治疗(230.25±67.46,P=0.000)均能减少PCNA免疫阳性细胞。结论亚低温可以抑制纹状体神经元的凋亡和星形胶质细胞的增殖,该作用可能为选择性头部降温的脑保护作用机制之一。  相似文献   
35.
孙爱军  盛杰  王荣  马骏 《医学争鸣》2007,28(22):2103-2104
恶性肿瘤靶向给药是指利用具有一定肿瘤靶向性的导向分子(载体)携带治疗肿瘤的药物,在肿瘤局部选择性杀伤肿瘤细胞(及转移的肿瘤细胞),以避免药物的全身毒副作用,提高疗效的一种治疗方法.由于抗癌药物在杀伤肿瘤细胞的同时也杀伤正常细胞,增加了全身的毒副作用.因此,近几年来,对恶性肿瘤靶向治疗的研究突飞猛进,发展了人源性抗HER-2mAb、依西美坦、放射性核素、  相似文献   
36.
37.
38.

Background

The effectiveness of diclofenac versus paracetamol in primary care patients with pain caused by knee osteoarthritis is unclear.

Aim

To assess the effectiveness of diclofenac compared with paracetamol over a period of 2, 4, and 12 weeks in patients with knee osteoarthritis.

Design and setting

Randomised controlled trial in general practice.

Method

There were 104 patients included in the study, they were aged ≥45 years consulting their GP with knee pain caused by knee osteoarthritis. Patients were randomly allocated to diclofenac (n = 52) or paracetamol (n = 52) for at least 2 weeks. Primary outcomes were daily knee pain severity, and knee pain and function measured with the Knee Injury and Osteoarthritis Outcome Score (KOOS).

Results

Over a period of 2- and 4-weeks follow-up, no significant difference in daily knee pain was found between the patient groups: estimated differences of 0.5 (95% CI = −0.2 to 1.3) and −0.2 (95% CI = −1.0 to 0.7), respectively. Over the 12-weeks follow-up, no significant differences were found between both groups for KOOS pain: estimated difference of −2.8 (95% CI = −10.7 to 5.1) and KOOS function of −2.7 (−10.6 to 5.0).

Conclusion

Over a period of 2- and 4-weeks follow-up no significant difference in daily measured knee pain severity was found between primary care patients with knee osteoarthritis taking paracetamol or diclofenac. Also, over a period of 12-weeks follow-up no significant differences were found regarding KOOS pain and KOOS function between both groups. Patients more frequently reported minor adverse events after taking diclofenac (64%) than paracetamol (46%).  相似文献   
39.
Phospholipase A2 levels in acute chest syndrome of sickle cell disease   总被引:4,自引:2,他引:4  
Acute chest syndrome (ACS) is associated with significant morbidity and is the leading cause of death in patients with sickle cell disease (SCD). Recent reports suggest that bone marrow fat embolism can be detected in many cases of severe ACS. Secretory phospholipase A2 (sPLA2) is an important inflammatory mediator and liberates free fatty acids, which are felt to be responsible for the acute lung injury of the fat embolism syndrome. We measured SPLA2 levels in 35 SCD patients during 20 admissions for ACS, 10 admissions for vaso-occlusive crisis, and during 12 clinic visits when patients were at the steady state. Eleven non-SCD patients with pneumonia were also evaluated. To determine if there was a relationship between sPLA2 and the severity of ACS we correlated SPLA2 levels with the clinical course of the patient. In comparison with normal controls (mean = 3.1 +/- 1.1 ng/mL), the non- SCD patients with pneumonia (mean = 68.6 +/- 82.9 ng/mL) and all three SCD patient groups had an elevation of SPLA2 (steady state mean = 10.0 +/- 8.4 ng/mL; vaso-occlusive crisis mean = 23.7 +/- 40.5 ng/mL; ACS mean = 336 +/- 209 ng/mL). In patients with ACS sPLA2 levels were 100- fold greater than normal control values, 35 times greater than values in SCD patients at baseline, and five times greater than non-SCD patients with pneumonia. The degree of SPLA2 elevation in ACS correlated with three different measures of clinical severity and, in patients followed sequentially, the rise in SPLA2 coincided with the onset of ACS. The dramatic elevation of SPLA2 in patients with ACS but not in patients with vaso-occlusive crisis or non-SCD patients with pneumonia and the correlation between levels of SPLA2 and clinical severity suggest a role for SPLA2 in the diagnosis and, perhaps, in the pathophysiology of patients with ACS.  相似文献   
40.
AJ  Fay  T  McMahon  C  Im  C  Bair-Marshall  KJ  Niesner  H  Li  A  Nelson  SM  Voglmaier  Y-H  Fu  LJ  Ptáček 《Neurogenetics》2021,22(3):171-185

Paroxysmal kinesigenic dyskinesia is an episodic movement disorder caused by dominant mutations in the proline-rich transmembrane protein PRRT2, with onset in childhood and typically with improvement or resolution by middle age. Mutations in the same gene may also cause benign infantile seizures, which begin in the first year of life and typically remit by the age of 2 years. Many details of PRRT2 function at the synapse, and the effects of mutations on neuronal excitability in the pathophysiology of epilepsy and dyskinesia, have emerged through the work of several groups over the last decade. However, the age dependence of the phenotypes has not been explored in detail in transgenic models. Here, we report our findings in heterozygous and homozygous Prrt2 knockout mice that recapitulate the age dependence of dyskinesia seen in the human disease. We show that Prrt2 deletion reduces the levels of synaptic proteins in a dose-dependent manner that is most pronounced at postnatal day 5 (P5), attenuates at P60, and disappears by P180. In a test for foot slippage while crossing a balance beam, transient loss of coordination was most pronounced at P60 and less prominent at age extremes. Slower traverse time was noted in homozygous knockout mice only, consistent with the ataxia seen in rare individuals with biallelic loss of function mutations in Prrt2. We thus identify three age-dependent phenotypic windows in the mouse model, which recapitulate the pattern seen in humans with PRRT2-related diseases.

  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