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   192729篇
  免费   3939篇
  国内免费   427篇
耳鼻咽喉   2749篇
儿科学   7396篇
妇产科学   5831篇
基础医学   24887篇
口腔科学   5739篇
临床医学   14972篇
内科学   34718篇
皮肤病学   4474篇
神经病学   11416篇
特种医学   10562篇
外国民族医学   98篇
外科学   28894篇
综合类   1090篇
一般理论   2篇
预防医学   16161篇
眼科学   4274篇
药学   13389篇
  2篇
中国医学   137篇
肿瘤学   10304篇
  2018年   3494篇
  2017年   3847篇
  2016年   3135篇
  2015年   4809篇
  2014年   4217篇
  2013年   3293篇
  2012年   9692篇
  2011年   4560篇
  2010年   2100篇
  2009年   3760篇
  2008年   1916篇
  2007年   2638篇
  2006年   2892篇
  2005年   11029篇
  2004年   12518篇
  2003年   8115篇
  2002年   3337篇
  2001年   4300篇
  2000年   1661篇
  1999年   5812篇
  1998年   500篇
  1995年   368篇
  1992年   6855篇
  1991年   7093篇
  1990年   7336篇
  1989年   6936篇
  1988年   6463篇
  1987年   6228篇
  1986年   5947篇
  1985年   5237篇
  1984年   3586篇
  1983年   2910篇
  1982年   999篇
  1981年   766篇
  1980年   835篇
  1979年   3827篇
  1978年   2362篇
  1977年   1782篇
  1976年   1560篇
  1975年   2473篇
  1974年   3106篇
  1973年   2738篇
  1972年   2757篇
  1971年   2741篇
  1970年   2556篇
  1969年   2466篇
  1968年   2238篇
  1967年   2163篇
  1966年   1900篇
  1965年   1132篇
排序方式: 共有10000条查询结果,搜索用时 17 毫秒
1.
The aim of this safety study in mice was to determine in vivo toxicity and biodistribution potential of a single and multiple doses of L-glutamic acid-g-p(HEMA) polymeric nanoparticles as a drug delivery system. The single dose did not cause any lethal effect, and its acute oral LD50 was >2.000 mg/kg body weight (bw). Multiple doses (25, 50, or 100 mg/kg bw) given over 28 days resulted in no significant differences in body and relative organ weights compared to control. These results are supported by biochemical and histological findings. Moreover, nanoparticle exposure did not result in statistically significant differences in micronucleus counts in bone marrow cells compared to control. Nanoparticle distribution was time-dependent, and they reached the organs and even bone marrow by hour 6, as established by ex vivo imaging with the IVIS® spectrum imaging system. In conclusion, L-glutamic acid-g-p(HEMA) polymeric nanoparticles appear biocompatible and have a potential use as a drug delivery system.KEY WORDS: biocompatibility, blood biochemistry, genotoxicity, histology, in vivo toxicity, micronucleus test, polymers  相似文献   
2.
3.
4.
5.
Sprengel deformity is a congenital anomaly arising mainly in the shoulder girdle, associated with elevation of dysplastic scapula. skeletal anomalies, mainly Klippel-Feil syndrome, hemivertebrae, and omovertebral bone may be present along Sprengel anomaly. The omovertebral bone is an abnormal bone that originates from the superomedial edge of the scapula with different insertion points along the posterior cervical spine, seen in about third of the patients with Sprengel anomaly. While cosmetic to functional impairment is a common presentation to the omovertebral bone, cervical myelopathy is a rare presentation. Here, we described our experience, management and follow up of 13-year-old boy presented with cervical myelopathy secondary to the omovertebral bone.

Sprengel deformity is a complex anomaly of the shoulder girdle, associated with elevation of dysplastic scapula.1-4 Clinically, it is associated with disfigurement and limitation of shoulder movement. Other skeletal anomalies – mainly, Klippel–Feil syndrome, hemivertebrae, and omovertebral bone may be present.4 The omovertebral bone is an abnormal bone that originates from the superomedial edge of the scapula with different insertion points along the posterior cervical spine, seen in about a third of patients with Sprengel anomaly.2,5 The clinical presentation ranges from cosmetic to functional impairment, while cervical myelopathy is a rare presentation related to omovertebral bone. The management and follow up is less described in the literature contributed to its rare occurance.6 Here, the author described a 13-year- old boy diagnosed with Sprengel deformity presented with myelopathic manifestation, where cervical magnetic resonance imaging (MRI) showed signal cord changes secondary to compression by intraspinal extension of the omovertebral bone. The patient underwent uneventful resection of the abnormal bone, and spinal cord decompression.  相似文献   
6.
肿瘤内微生物群(组)已被证实广泛存在于各类肿瘤内,对肿瘤微环境的形成、调控肿瘤生长均发挥着重要作用,并直接影响药物干预肿瘤的疗效。随着新一代基因测序技术的广泛应用,针对肿瘤内微生物功能和分类的研究日益增温。诸多研究表明不同肿瘤内微生物种属分布不同,且不同种微生物所发挥的促/抑瘤机制不同。针对肿瘤内微生物的编辑技术亦取得了许多成果,有望成为检测与治疗肿瘤的新手段。本文旨在对近年来肿瘤内微生物群(组)相关研究进展加以综述,并展望其应用前景。  相似文献   
7.
8.
In this study, the cytotoxicity of the recently described subtilase variant SubAB2-2 of Shiga toxin-producing Escherichia coli was determined and compared to the plasmid-encoded SubAB1 and the chromosome-encoded SubAB2-1 variant. The genes for the respective enzymatic active (A) subunits and binding (B) subunits of the subtilase toxins were amplified and cloned. The recombinant toxin subunits were expressed and purified. Their cytotoxicity on Vero cells was measured for the single A and B subunits, as well as for mixtures of both, to analyze whether hybrids with toxic activity can be identified. The results demonstrated that all three SubAB variants are toxic for Vero cells. However, the values for the 50% cytotoxic dose (CD50) differ for the individual variants. Highest cytotoxicity was shown for SubAB1. Moreover, hybrids of subunits from different subtilase toxins can be obtained which cause substantial cytotoxicity to Vero cells after mixing the A and B subunits prior to application to the cells, which is characteristic for binary toxins. Furthermore, higher concentrations of the enzymatic subunit SubA1 exhibited cytotoxic effects in the absence of the respective B1 subunit. A more detailed investigation in the human HeLa cell line revealed that SubA1 alone induced apoptosis, while the B1 subunit alone did not induce cell death.  相似文献   
9.
Background: The aim of present study is evaluation of vitamin A supplementation efficacy on IFN-? and T-bet gene expression in atherosclerotic patients.

Methods: Thirty-one patients and 15 healthy controls participated in this study. Healthy control and patients in Vitamin A group received 25?000?IU retinyl palmitate daily for 4 months. Control patients also received 1 pearl of placebo per day up to 4 months. Gene expression levels were assessed by real-time PCR using SYBR green detection method.

Results: IFN-γ gene expression in fresh cells of patients taking vitamin A declined slightly (0.85-fold, p?=?0.068), whereas the expression of this gene was increased in patients taking placebo, and in healthy control subjects 1.2-fold (p?=?0.267) and 1.7-fold (p?=?0.580), respectively. There were no significant difference (p?=?0.159) between 3 groups in terms of IFN-γ gene expression in cells stimulated with PHA. In order to determine whether PHA stimulation of PBMCs in vitro had an effect on T-bet expression, we measured the difference between the 3 groups of studied. The results showed significant differences between the groups (p?=?0.046). IFN-γ gene expression in cells activated with ox-LDL in healthy control subjects and patients taking vitamin A, was reduced 0.43 (p?=?0.0001) and 0.41 (p?=?0.001) respectively, but in placebo patients was increased 2.2-fold (p?=?0.959).

Conclusion: Considering role of vitamin A on suppression of Th1 cells in atherosclerotic patients, it can be concluded that vitamin A supplementation may be advantageous for these patients.  相似文献   
10.
After 4 years of early benefit assessment (EBA) in Germany, it is becoming evident that the Federal Joint Committee (FJC) frequently considers well-established clinical endpoints as not being relevant to patients. Focusing on assessments of oncology medicines, we analysed the FJC’s view on primary endpoints and compared it with the approach used by regulatory authorities. Mortality data were accepted by both stakeholders. Whereas regulatory authorities accepted primary morbidity endpoints such as progression-free survival and response rates, the FJC mostly excluded these from its assessments. Health-related quality of life (HRQoL) data have been poorly reflected in the approval process; for EBAs, those data have rarely impacted on benefit ratings. We argue that agreement between regulatory authorities and the FJC is required regarding primary study endpoints that are relevant to patients, and that clarification of acceptable endpoints by the FJC, especially in the morbidity domain, has to be provided. Moreover, in order to fully acknowledge the benefit of a new medicinal product, mortality, morbidity and HRQoL should be weighted differentially, according to the condition.  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