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   11748篇
  免费   855篇
  国内免费   99篇
耳鼻咽喉   89篇
儿科学   388篇
妇产科学   269篇
基础医学   1296篇
口腔科学   180篇
临床医学   1069篇
内科学   2493篇
皮肤病学   153篇
神经病学   832篇
特种医学   545篇
外科学   1799篇
综合类   261篇
一般理论   7篇
预防医学   694篇
眼科学   979篇
药学   751篇
中国医学   70篇
肿瘤学   827篇
  2023年   104篇
  2022年   140篇
  2021年   297篇
  2020年   186篇
  2019年   269篇
  2018年   309篇
  2017年   209篇
  2016年   204篇
  2015年   255篇
  2014年   322篇
  2013年   407篇
  2012年   622篇
  2011年   687篇
  2010年   416篇
  2009年   369篇
  2008年   609篇
  2007年   708篇
  2006年   679篇
  2005年   650篇
  2004年   592篇
  2003年   544篇
  2002年   502篇
  2001年   448篇
  2000年   397篇
  1999年   329篇
  1998年   144篇
  1997年   112篇
  1996年   111篇
  1995年   91篇
  1994年   80篇
  1993年   82篇
  1992年   180篇
  1991年   177篇
  1990年   157篇
  1989年   132篇
  1988年   142篇
  1987年   154篇
  1986年   113篇
  1985年   115篇
  1984年   70篇
  1983年   85篇
  1982年   69篇
  1981年   50篇
  1980年   56篇
  1979年   68篇
  1978年   52篇
  1977年   32篇
  1976年   24篇
  1973年   16篇
  1972年   15篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
Energy drinks containing significant quantities of caffeine, taurine and sugar are increasingly consumed, particularly by adolescents and young adults. The putative effects of chronic ingestion of either standard energy drink, MotherTM (ED), or its sugar-free formulation (sfED) on metabolic syndrome were determined in wild-type C57BL/6J mice, in comparison to a soft drink, Coca-Cola (SD), a Western-styled diet enriched in saturated fatty acids (SFA), and a combination of SFA + ED. Following 13 weeks of intervention, mice treated with ED were hyperglycaemic and hypertriglyceridaemic, indicating higher triglyceride glucose index, which was similar to the mice maintained on SD. Surprisingly, the mice maintained on sfED also showed signs of insulin resistance with hyperglycaemia, hypertriglyceridaemia, and greater triglyceride glucose index, comparable to the ED group mice. In addition, the ED mice had greater adiposity primarily due to the increase in white adipose tissue, although the body weight was comparable to the control mice receiving only water. The mice maintained on SFA diet exhibited significantly greater weight gain, body fat, cholesterol and insulin, whilst blood glucose and triglyceride concentrations remained comparable to the control mice. Collectively, these data suggest that the consumption of both standard and sugar-free forms of energy drinks induces metabolic syndrome, particularly insulin resistance.  相似文献   
102.
The European Journal of Health Economics - Social support is increasingly acknowledged as an important resource for promoting well-being. We test whether social support changes around retirement....  相似文献   
103.
104.
Osteoporosis is a systemic skeletal disease characterized by low bone mass and bone structural deterioration that may result in fragility fractures. Use of bone imaging modalities to accurately predict fragility fractures is always an important issue, yet the current gold standard of dual-energy X-ray absorptiometry (DXA) for diagnosis of osteoporosis cannot fully satisfy this purpose. The latest high-resolution peripheral quantitative computed tomography (HR-pQCT) is a three-dimensional (3D) imaging device to measure not only volumetric bone density, but also the bone microarchitecture in a noninvasive manner that may provide a better fracture prediction power. This systematic review and meta-analysis was designed to investigate which HR-pQCT parameters at the distal radius and/or distal tibia could best predict fragility fractures. A systematic literature search was conducted in Embase, PubMed, and Web of Science with relevant keywords by two independent reviewers. Original clinical studies using HR-pQCT to predict fragility fractures with available full text in English were included. Information was extracted from the included studies for further review. In total, 25 articles were included for the systematic review, and 16 articles for meta-analysis. HR-pQCT was shown to significantly predict incident fractures and/or major osteoporotic fractures (MOFs). Of all the HR-pQCT parameters, our meta-analysis revealed that cortical volumetric bone mineral density (Ct.vBMD), trabecular thickness (Tb.Th), and stiffness were better predictors. Meanwhile, HR-pQCT parameters indicated better performance in predicting MOFs than incident fractures. Between the two standard measurement sites of HR-pQCT, the non-weight-bearing distal radius was a more preferable site than distal tibia for fracture prediction. Furthermore, most of the included studies were white-based, whereas very few studies were from Asia or South America. These regions should build up their densitometric databases and conduct related prediction studies. It is expected that HR-pQCT can be used widely for the diagnosis of osteoporosis and prediction of future fragility fractures. © 2021 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).  相似文献   
105.
Tioman virus, a novel paramyxovirus isolated from fruit bats in Malaysia   总被引:18,自引:0,他引:18  
Chua KB  Wang LF  Lam SK  Crameri G  Yu M  Wise T  Boyle D  Hyatt AD  Eaton BT 《Virology》2001,283(2):215-229
A search for the natural host of Nipah virus has led to the isolation of a previously unknown member of the family Paramyxoviridae. Tioman virus (TiV) was isolated from the urine of fruit bats (Pteropus hypomelanus) found on the island of the same name off the eastern coast of peninsular Malaysia. An electron microscopic study of TiV-infected cells revealed spherical and pleomorphic-enveloped viral particles (100--500 nm in size) with a single fringe of embedded peplomers. Virus morphogenesis occurred at the plasma membrane of infected cells and morphological features of negative-stained ribonucleoprotein complexes were compatible with that of viruses in the family Paramyxoviridae. Serological studies revealed no cross-reactivity with antibodies against a number of known Paramyxoviridae members except for the newly described Menangle virus (MenV), isolated in Australia in 1997. Failure of PCR amplification using MenV-specific primers suggested that this new virus is related to but different from MenV. For molecular characterization of the virus, a cDNA subtraction strategy was employed to isolate virus-specific cDNA from virus-infected cells. Complete gene sequences for the nucleocapsid protein (N) and phosphoprotein (P/V) have been determined and recombinant N and V proteins produced in baculovirus. The recombinant N and V proteins reacted with porcine anti-MenV sera in Western blot, confirming the serological cross-reactivity observed during initial virus characterization. The lack of a C protein-coding region in the P/V gene, the creation of P mRNA by insertion of 2-G residues, and the results of phylogenetic analyses all indicated that TiV is a novel member of the genus Rubulavirus.  相似文献   
106.
Acute porphyria is rare in orientals. We describe a Chinese woman with recurrent generalised tonic-clonic seizures and abdominal pain. Genomic DNA studies identified a heterozygous base substitution from guanine to adenine at nucleotide position 503, resulting in substitution of arginine by histidine at position 168 of the protein (R168H). This genetic abnormality is similar to the mutation reported in Caucasians with variegate porphyria. To the best of our knowledge, this is the first report in the English literature a Chinese patient with variegate porphyria with an identifiable mutation. A brief review of porphyria is presented.  相似文献   
107.
Acquired resistance to chemotherapy is the major obstacle to cure of small cell lung cancer (SCLC). Some of the most active drugs in the treatment of this tumor exert their cytotoxicity by interacting with the nuclear enzyme topoisomerase II (topo II), which in mammalian cells occurs in two isoforms, alpha and beta. We examined the relationship between levels of topo II alpha and beta and drug response in a panel of 25 unselected SCLC cell lines. Chemosensitivity to several topo II-interactive drugs, as well as other chemotherapeutic agents, was quantitated previously using a modified MTT assay. Topo II levels were determined by immunoblot analysis of whole cell lysates, with topo II alpha and beta isoform-specific antibodies, and results were expressed relative to levels found in NCI-H209 cells which had the highest topo II alpha in this series of cell lines. Levels of topo II alpha and beta mRNA were determined by Northern blotting. Pearson correlation analysis was used to determine the significance of the relationship between topo II alpha and beta levels and response to the various chemotherapeutic drugs, as well as the treatment history of the patients from whom the cell lines were derived. These analyses revealed an inverse correlation between topo II alpha levels and resistance to all of the tested drugs, including several drugs which are not known to interact with topo II. This correlation was statistically significant for doxorubicin, cisplatin, epirubicin, melphalan, nitrogen mustard, and vinblastine. With one exception (cisplatin), there were no significant correlations between topo II beta levels and drug response. There was no significant correlation between topo II alpha and beta levels and treatment history. Taken together, our results are consistent with the hypothesis that levels of topo II alpha are important determinants of drug response in SCLC.  相似文献   
108.
PURPOSE: Most studies of depressed mood and its correlates in adolescents have been conducted in Western countries. This study examined the relationship between a broad range of stressors and depressed mood in a community sample of Hong Kong adolescents. METHODS: Secondary school students (n = 996) completed the Chinese Beck Depression Inventory (C-BDI), provided demographic information, and indicated their perceptions of family and peer relationships, school function and pressures, and subjective health, and some measures salient to the Hong Kong environment: triad gang pressure, religiosity, and intent to emigrate. The correlation between C-BDI and these variables was assessed in bivariate and multivariate analyses. RESULTS: Hong Kong adolescents reported higher levels of depressive symptoms than a comparison group of Western teenagers. Girls showed more symptoms than boys. All stressors correlated in bivariate analyses with C-BDI, indicating similar influences on depressed mood in Western and Hong Kong teenagers. In multivariate analyses, the stressors contributed cumulatively to the C-BDI score. Perceptions of a lack of parental understanding and peer acceptance appeared as the strongest variables in predicting depressed mood. CONCLUSIONS: Depressed mood is highly prevalent among Hong Kong teenagers. Stressors play a cumulative role in their relationship to mood. Our findings point to the importance of broad screening of this vulnerable population.  相似文献   
109.
AIM: To investigate whether PTEN/MMAC1 mutations play a role in the carcinogenesis of oesophageal squamous cell carcinoma. METHODS: A panel of 33 primary oesophageal squamous cell carcinoma tumour samples and 20 corresponding morphologically normal tissues was examined for mutations in all nine exons of the PTEN/MMAC1 gene by means of polymerase chain reaction single strand conformational polymorphism analysis (PCR-SSCP) and direct DNA sequencing methods. RESULTS: Only one of 33 oesophageal squamous cell carcinomas showed an aberrant SSCP band. Further sequencing analysis of this sample revealed an 802 -29 T-->C substitution in intron 7. PTEN/MMAC1 mutations were not found in the mutational "hot spot" in exon 5, even after direct sequencing of six oesophageal squamous cell carcinoma samples and three normal tissues. However, a deletion of one nucleotide T at position 492 +8 in intron 5 was seen in all samples. CONCLUSION: These results suggest that PTEN/MMAC1 mutations do not play a major role in the carcinogenesis of oesophageal squamous cell carcinoma.  相似文献   
110.
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