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   196721篇
  免费   17968篇
  国内免费   7562篇
耳鼻咽喉   1194篇
儿科学   4624篇
妇产科学   2686篇
基础医学   37217篇
口腔科学   3775篇
临床医学   12354篇
内科学   33467篇
皮肤病学   3250篇
神经病学   16080篇
特种医学   3716篇
外国民族医学   57篇
外科学   14312篇
综合类   24134篇
现状与发展   30篇
预防医学   8860篇
眼科学   2296篇
药学   26028篇
  21篇
中国医学   6776篇
肿瘤学   21374篇
  2024年   515篇
  2023年   3101篇
  2022年   6321篇
  2021年   8010篇
  2020年   6752篇
  2019年   7742篇
  2018年   7344篇
  2017年   7239篇
  2016年   7084篇
  2015年   8502篇
  2014年   11859篇
  2013年   13245篇
  2012年   12186篇
  2011年   14445篇
  2010年   12286篇
  2009年   11650篇
  2008年   11053篇
  2007年   9843篇
  2006年   8908篇
  2005年   7591篇
  2004年   6646篇
  2003年   5644篇
  2002年   4374篇
  2001年   3732篇
  2000年   3087篇
  1999年   2801篇
  1998年   2402篇
  1997年   2178篇
  1996年   1883篇
  1995年   1583篇
  1994年   1380篇
  1993年   1163篇
  1992年   969篇
  1991年   867篇
  1990年   714篇
  1989年   599篇
  1988年   513篇
  1987年   415篇
  1986年   422篇
  1985年   796篇
  1984年   820篇
  1983年   574篇
  1982年   644篇
  1981年   508篇
  1980年   418篇
  1979年   365篇
  1978年   280篇
  1977年   221篇
  1976年   206篇
  1975年   142篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
目的:在女性性早熟患儿中检测雌激素受体基因6号外显子及内含子基因序列可能存在的突变。方法:PCR扩增雌激素受体基因6号外显子及内含子,对扩增产物进行DNA序列分析。结果:在6号内含子一侧,发现两个100%连锁的单核苷酸多态性(SNPs),分别为.53G—67A和53T—67G。结论:这一对单核苷酸多态性并不引起氨基酸的替代,与女孩性早熟的发生也无关,但是否和其他疾病有连锁关系尚待进一步探讨。  相似文献   
102.
The MIC values of the antifungal drug ketoconazole were evaluated on 66 Candida albicans strains. These strains were isolated from 26 HIV-1 infected patients with oral recurrent candidosis. Each episode of oral candidosis observed in these patients was orally treated with ketoconazole (200 mg/day) until the clinical disappearance of the lesions. The most frequent MIC values were 20 micrograms/ml and 10 micrograms/ml, observed in 37 and 19 isolates respectively. Only strains from five patients showed changes in their susceptibility to ketoconazole. This fact could indicate that a different strain causes the subsequent reappearance of the oral lesions, rather than the drug selecting resistant fungal strains. Our results stress the role of host characteristics in the occurrence of candidal infections, pointing to the progressing failure of the immunological response as the most important factor responsible for the recurrence of oral candidosis during HIV-1 infection.  相似文献   
103.
Diagnostic accuracy has been addressed previously for Parkinson's disease in a brain bank collection, but accuracy of progressive supranuclear palsy (PSP) has not been addressed in a similar setting. Clinical and genetic features of pathologically confirmed cases of PSP were compared with misdiagnosed cases to determine ways to improve diagnostic accuracy. Medical records were reviewed for 180 cases sent to the Society of Progressive Supranuclear Palsy Brain Bank that had standardized neuropathologic evaluations as well as determination of apolipoprotein E and tau genotypes. Of the 180 cases studied, 137 had PSP and 43 had other pathologic diagnoses. Corticobasal degeneration (CBD), multiple system atrophy (MSA), and diffuse Lewy body disease (DLBD) accounted for 70% of the misdiagnosed cases. History of tremor, psychosis, dementia, and asymmetric findings were more frequent in misdiagnosed cases. The frequency of H1 tau haplotype (93 vs. 80%) and H1H1 genotype (86 vs. 66%) were significantly greater and APOE epsilon4 carrier state was significantly less (17 vs. 41 %) in PSP compared with misdiagnosed cases. Pathologic evaluation of clinically diagnosed PSP remains important for definitive diagnosis, and CBD, MSA, and DLBD are the disorders most likely to be misdiagnosed as PSP. Tremor, psychosis, early dementia, asymmetric findings, absence of H1 haplotype, and presence of APOE epsilon4 should raise questions about a diagnosis of PSP.  相似文献   
104.
105.
Cyclin D1 in astrocytic tumours: an immunohistochemical study   总被引:1,自引:0,他引:1  
Forty-eight astrocytic tumours were stained immunohistochemically with antibodies to the cell cycle-regulating protein, cyclin D1, and to the proliferation marker MIB1 (Ki-67) using formalin fixed paraffin embedded tissue and a microwave antigen retrieval system. Cases were classified by the WHO system (1993). The labelling indices (LI) for both antibodies were compared with each other and with the tumour type. The mean labelling indices for both antibodies increased with the degree of malignancy, and a significant difference was seen between the pilocytic astrocytoma and diffuse astrocytoma together vs anaplastic astrocytoma and glioblastoma together. However, within each tumour type there was considerable variation in the labelling indices and a clear cut off value could not be demonstrated. There was a strong positive correlation between labelling indices for cyclin D1 and MIB1 in diffuse astrocytoma, but this correlation broke down increasingly in anaplastic astrocytoma and glioblastoma. There was poor correlation between cyclin D1 and MIB1 in pilocytic astrocytoma, a feature which appeared to separate them from the diffuse astrocytoma. Average labelling indices for cyclin D1 were higher than those of MIB1, which suggests that cyclin D1 positive cells represent a pool of cells from which proliferation and hence MIB1 expression can take place. In conclusion, cyclin D1 is overexpressed in astrocytic tumours, more so with increasing grade of malignancy and in a way which approximately correlates with MIB1 expression.  相似文献   
106.
The matrix metalloproteinase matrilysin (MMP-7) is a member of the matrix metallo-proteinase gene family, which is believed to play an important role in tumor invasion and metastasis. We have previously found that matrilysin mRNA is specifically expressed in colorectal cancers and adenomas and that its message is localized in the tumor cells themselves. We examined the effects of activated Ki-ras oncogene on the expression of matrilysin in colon cancer cells. We showed that both mRNA and the enzymatic activity of matrilysin were induced by the introduction of activated Ki-ras into SW1417 colon cancer cells. To understand the mechanisms regulating this induction, we analyzed alterations of AP-1 activity induced by activated Ki-ras, using the chloramphenicol acetyltransferase assay. AP-1 activity in SW1417 cells expressing activated Ki-ras was higher than that in control cells. The gel-shift assay also showed higher levels of AP-1 binding protein in SW1417 cells expressing activated Ki-ras than those in control cells. Our results suggest that activated Ki-ras may play a role in inducing expression of matrilysin through an AP-1-dependent pathway in colon cancer cells.  相似文献   
107.
Gingival crevicular fluid (GCF) IL-8 and IL-1,1β levels were determined by sandwich enzyme-linked immunosorbent assays. Associations between IL-8 and IL-1β GCF levels, and between these cytokines and patient estrogen status were evaluated. IL-8 and IL-1β were detected more frequently and in higher amounts/30 s GCF sample in estrogen-deficient patients than in estrogensufficient patients. IL-8 and IL-1β GCF levels were significantly correlated. These lindings suggest that GCF IL-8 levels are associated with patient estrogen status and local IL-1β concentrations.  相似文献   
108.
In neurons, a network of endocytic proteins accomplishes highly regulated processes such as synaptic vesicle cycling and the timely internalization of intracellular signaling molecules. In this review, we discuss recent advances on molecular networks created through interactions between proteins bearing the Eps15 homology (EH) domain and partner proteins containing the Asn–Pro–Phe (NPF) motif, which participate in important aspects of neuronal function as the synaptic vesicle cycle, the internalization of nerve growth factor (NGF), the determination of neuronal cell fate, the development of synapses and the trafficking of postsynaptic receptors. We discuss novel functional findings on the role of intersectin and synaptojanin and then we focus on the features of an emerging family of EH domain proteins termed EHDs (EH domain proteins), which are important for endocytic recycling of membrane proteins.  相似文献   
109.
目的探讨前列腺素E1(PGE1)应用于尸体肾移植术后肾功能延迟恢复(DGF)患者对移植肾功能恢复的影响.方法回顾性分析因急性排斥(AR)和急性肾小管坏死(ANT)导致DGF的127例临床资料,其中应用PGE1治疗56例(PGE1组),未用PGE1者71例(对照组).比较两组在出现DGF后的透析治疗时间、肾功能恢复情况、彩超的移植肾血流阻力指数(RI)及6个月内AR发生率.结果与对照组比较,PGE1组透析治疗时间明显缩短(P<0.05),移植肾的血肌酐下降速度快(P<0.05),RI及6个月内AR发生率低(P<0.05).结论PGE1有利于尸体肾移植术后DGF患者移植肾功能的早期恢复,并能降低AR的发生率.  相似文献   
110.
AIMS: To determine the most appropriate regression models to use when assessing risk factors for severe hypoglycaemia and to investigate the impact of model misspecification and its clinical implications. METHODS: A total of 1229 children with Type 1 diabetes (mean age 11.7 years sd 4.1), of which 605 (49.2%) were males, were studied. Prospective assessment of severe hypoglycaemia (an event leading to loss of consciousness or seizure) was made over the 9-year period, 1992-2001. Patients were seen every 3 months and episodes of hypoglycaemia along with clinical data were recorded. Over 70% of children never experienced a severe hypoglycaemic event. Data were analysed using the Poisson regression, negative binomial, zero-inflated Poisson (ZIP) and zero-inflated negative binomial (ZINB) models. The over-dispersion and likelihood ratio statistics were calculated and the analytical methods compared. RESULTS: The Poisson regression model did not fit the data well. The negative binomial and the zero inflated Poisson and negative binomial models fitted the data better than Poisson. CONCLUSIONS: The commonly used Poisson regression models to analyse hypoglycaemia epidemiology may lead to biased parameter estimates and incorrect determination of risk factors for hypoglycaemia. We recommend the use of the negative binomial or zero inflated models to examine any risk factors associated with severe hypoglycaemia. Careful consideration must be given to the interpretation of hypoglycaemia surveys and their analysis.  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