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   5368篇
  免费   362篇
  国内免费   9篇
耳鼻咽喉   63篇
儿科学   158篇
妇产科学   105篇
基础医学   850篇
口腔科学   57篇
临床医学   913篇
内科学   1044篇
皮肤病学   58篇
神经病学   410篇
特种医学   139篇
外科学   416篇
综合类   36篇
一般理论   10篇
预防医学   621篇
眼科学   92篇
药学   344篇
中国医学   11篇
肿瘤学   412篇
  2023年   24篇
  2022年   51篇
  2021年   129篇
  2020年   73篇
  2019年   139篇
  2018年   157篇
  2017年   88篇
  2016年   113篇
  2015年   124篇
  2014年   180篇
  2013年   273篇
  2012年   396篇
  2011年   428篇
  2010年   205篇
  2009年   192篇
  2008年   368篇
  2007年   347篇
  2006年   353篇
  2005年   348篇
  2004年   330篇
  2003年   301篇
  2002年   305篇
  2001年   51篇
  2000年   49篇
  1999年   58篇
  1998年   60篇
  1997年   54篇
  1996年   47篇
  1995年   32篇
  1994年   28篇
  1993年   30篇
  1992年   28篇
  1991年   23篇
  1990年   26篇
  1989年   20篇
  1988年   17篇
  1987年   22篇
  1986年   28篇
  1985年   23篇
  1984年   25篇
  1983年   28篇
  1982年   35篇
  1981年   13篇
  1980年   19篇
  1979年   13篇
  1978年   7篇
  1977年   12篇
  1975年   10篇
  1974年   14篇
  1973年   7篇
排序方式: 共有5739条查询结果,搜索用时 15 毫秒
101.
102.
103.
Noroviruses and sapoviruses are members of the family Caliciviridae and emerging enteric pathogens of humans and animals. Since their discovery and characterization in swine, relatively few strains have been described in detail. In order to investigate their genetic diversity, a total of 266 fecal samples collected in the province of Quebec, Canada, between 2005 and 2007 were screened for the presence of caliciviruses by RT-PCR using broadly reactive primers. Genetically heterogeneous caliciviruses were detected on the majority of farms. Typical noroviruses related to known swine genotypes were present on 20% of the farms. Sapoviruses were detected on 75% of the farms and were the most heterogeneous group. Further characterization of selected strains in their 3′ end parts was carried out for their classification and unveiled possibly new clusters of sapoviruses. No human-like noroviruses or sapoviruses were detected in the present study. GenBank accession numbers of all sequences described in this study are indicated in the figure legends.  相似文献   
104.
Despite the maternal and infant morbidity associated with gestational diabetes mellitus (GDM), few modifiable risk factors have been identified. We explored the relation between recreational physical activity performed during the year before and during the first 20 weeks of pregnancy and the risk of GDM. 155 GDM cases and 386 normotensive, non-diabetic pregnant controls provided information about the type, intensity, frequency, and duration of physical activity performed during these time periods. Women who participated in any recreational physical activity during the first 20 weeks of pregnancy, as compared with inactive women, experienced a 48% reduction in risk of GDM (odds ratio [OR] = 0.52; 95% confidence interval [CI] 0.33-0.80). The number of hours spent performing recreational activities and the energy expended were related to a decrease in GDM risk. No clear patterns related to distance walked and pace of walking emerged. Daily stair climbing, when compared with no stair climbing, was associated with a 49-78% reduction in GDM risk (P for trend <0.011). Recreational physical activity performed during the year before the index pregnancy was also associated with statistically significant reductions in GDM risk, but women who engaged in physical activity during both time periods experienced the greatest reduction in risk (OR = 0.40; 95% CI 0.23-0.68). These data suggest that recreational physical activity performed before and/or during pregnancy is associated with a reduced risk of GDM.  相似文献   
105.
Aberrant up-regulation of aromatase in eutopic endometrium and implants from women with endometriosis has been reported. Aromatase induction may be mediated by increased cyclooxygenase-2 (COX-2). Recently, we demonstrated that progesterone receptor (PR)-A and PR-B serve an antiinflammatory role in the uterus by antagonizing nuclear factor kappaB activation and COX-2 expression. PR-C, which antagonizes PR-B, is up-regulated by inflammation. Although estrogen receptor alpha (ERalpha) is implicated in endometriosis, an antiinflammatory role of ERbeta has been suggested. We examined stage-specific expression of aromatase, COX-2, ER, and PR isoform expression in eutopic endometrium, implants, peritoneum, and endometrioma samples from endometriosis patients. Endometrial and peritoneal biopsies were obtained from unaffected women and those with fibroids. Aromatase expression in eutopic endometrium from endometriosis patients was significantly increased compared with controls. Aromatase expression in endometriosis implants was markedly increased compared with eutopic endometrium. Aromatase mRNA levels were increased significantly in red implants relative to black implants and endometrioma cyst capsule. Moreover, COX-2 expression was increased in implants and in eutopic endometrium of women with endometriosis as compared with control endometrium. As observed for aromatase mRNA, the highest levels of COX-2 mRNA were found in red implants. The ratio of ERbeta/ERalpha mRNA was significantly elevated in endometriomas compared with endometriosis implants and eutopic endometrium. Expression of PR-C mRNA relative to PR-A and PR-B mRNA was significantly increased in endometriomas compared with eutopic and control endometrium. PR-A protein was barely detectable in endometriomas. Thus, whereas PR-C may enhance disease progression, up-regulation of ERbeta may play an antiinflammatory and opposing role.  相似文献   
106.
Allergic rhinitis (AR) is a common chronic condition in children and may impact a child's quality of life. Increasing treatment compliance may improve quality of life. An oral suspension of fexofenadine hydrochloride (HCl) has been developed to ease administration to children and may, therefore, improve treatment compliance. The purpose of this study was to assess the pharmacokinetic behavior, safety, and tolerability of a single dose of fexofenadine HCl oral suspension administered to children aged 2-5 years with allergic rhinitis. Children (aged 2-5 years) with AR were recruited in a multicenter, open-label, single-dose study. Fexofenadine HCl (30 mg) was administered as a 6-mg/mL suspension (5 mL). Plasma samples were collected up to 24 hours postdose. Adverse events (AEs); electrocardiograms (ECGs); vital signs; and clinical laboratory tests for hematology, blood chemistry, and urinalysis were analyzed to evaluate safety and tolerability. Fifty subjects completed the study. Mean maximum plasma concentration of fexofenadine was 224 ng/mL, and mean area under the plasma concentration curve was 898 ng . hour/mL. Treatment-emergent AEs were mild in intensity and reported in a total of seven subjects. No trends or clinically meaningful changes in mean ECG, vital sign, or clinical laboratory test data occurred during the study. In children aged 2-5 years, the exposure after a 30-mg dose of fexofenadine HCl suspension was similar to the exposures previously seen after a 30- and 60-mg dose of fexofenadine HCl in children aged 6-11 years and in adults, respectively. The suspension was also well tolerated.  相似文献   
107.
Particulate air pollution is widespread, yet we have little understanding of the long-term health implications associated with exposure. We investigated DNA damage, mutation, and methylation in gametes of male mice exposed to particulate air pollution in an industrial/urban environment. C57BL/CBA mice were exposed in situ to ambient air near two integrated steel mills and a major highway, alongside control mice breathing high-efficiency air particulate (HEPA) filtered ambient air. PCR analysis of an expanded simple tandem repeat (ESTR) locus revealed a 1.6-fold increase in sperm mutation frequency in mice exposed to ambient air for 10 wks, followed by a 6-wk break, compared with HEPA-filtered air, indicating that mutations were induced in spermatogonial stem cells. DNA collected after 3 or 10 wks of exposure did not exhibit increased mutation frequency. Bulky DNA adducts were below the detection threshold in testes samples, suggesting that DNA reactive chemicals do not reach the germ line and cause ESTR mutation. In contrast, DNA strand breaks were elevated at 3 and 10 wks, possibly resulting from oxidative stress arising from exposure to particles and associated airborne pollutants. Sperm DNA was hypermethylated in mice breathing ambient relative to HEPA-filtered air and this change persisted following removal from the environmental exposure. Increased germ-line DNA mutation frequencies may cause population-level changes in genetic composition and disease. Changes in methylation can have widespread repercussions for chromatin structure, gene expression and genome stability. Potential health effects warrant extensive further investigation.  相似文献   
108.
Hypoxia-inducible factor (HIF)-1alpha is activated on exposure to bacterial pathogens and regulates the innate immune functions of phagocytes. We show here that the HIF-1alpha agonist mimosine can boost the capacity of human phagocytes and whole blood to kill the leading pathogen Staphylococcus aureus in a dose-dependent fashion and reduce the lesion size in a murine model of S. aureus skin infection. This provides the first proof of principle for a novel approach to the treatment of bacterial infection by pharmacologically augmenting the host phagocytic function.  相似文献   
109.
The emerging of Quantum Dots utilization in industrial or medicinal fields involved a potentially increase of these nanoparticles in environment. In this work, the genotoxic (comet assay) and oxidative effects (SOD activity, TBARS) of functionalized‐QDs and cadmium chloride were investigated on Hediste diversicolor and Eisenia fetida coelomocytes. Results demonstrated that functionalized‐QDs (QDNs) and cadmium chloride induced DNA damages through different mechanisms that depended on the nano‐ or ionic nature of Cd. The minimal genotoxic concentrations for H. diversicolor (<0.001ng/g for QDNs and CdCl2) were lower than for E. fetida (between 0.01 and 0.1 ng/g for QDNs, and between 0.001 and 0.01 ng/g for CdCl2). These results showed that H. diversicolor was more sensitive than E. fetida. The two contaminants had a low impact on the oxidative stress markers. © 2014 Wiley Periodicals, Inc. Environ Toxicol 30: 918–926, 2015.  相似文献   
110.
Rationale:Meningeal melanocytoma is a rare benign melanocytic tumor of the central nervous system. We report for the first time a case of meningeal melanocytoma treated with immunotherapy.Patient concerns:A 70-year-old man with no medical history was admitted to the Emergency Room. He suffered from a motor and sensory deficit in his left lower limb and a bilateral upper arm neuralgia.Diagnoses:A contrast-enhanced magnetic resonance imaging (MRI) was performed. It showed a C7-T1 bleeding intramedullary tumor. Laminectomy was decided and performed. The results of the pathologic examination showed a melanocytic tumor harboring GNAQ mutation. Meningeal melanocytoma was the final diagnosis.Interventions:The patient was treated with 10 radiotherapy sessions and 6 cycles of nivolumab. A year later, the patient experienced neuralgia again with severe pain and an increasing sensory motor deficit. He underwent a second surgery that was incomplete. As the tumor kept growing, he received temozolomide. But the 6th cycle had to be interrupted due to bedsore infection in the hip area.Outcomes:Disease progression finally led to the patient''s death 3 years after diagnosis.Lessons:This case report is the first about a patient with meningeal melanocytoma treated with immunotherapy. Treatment based on biomolecular mutations will probably change spinal melanocytoma therapeutic approach in the next few years.  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