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   7967篇
  免费   451篇
  国内免费   36篇
耳鼻咽喉   129篇
儿科学   208篇
妇产科学   139篇
基础医学   1045篇
口腔科学   573篇
临床医学   807篇
内科学   1362篇
皮肤病学   310篇
神经病学   692篇
特种医学   143篇
外科学   600篇
综合类   34篇
一般理论   6篇
预防医学   1117篇
眼科学   118篇
药学   555篇
中国医学   56篇
肿瘤学   560篇
  2024年   5篇
  2023年   57篇
  2022年   93篇
  2021年   194篇
  2020年   129篇
  2019年   185篇
  2018年   204篇
  2017年   153篇
  2016年   219篇
  2015年   257篇
  2014年   314篇
  2013年   451篇
  2012年   657篇
  2011年   809篇
  2010年   415篇
  2009年   339篇
  2008年   538篇
  2007年   641篇
  2006年   564篇
  2005年   514篇
  2004年   451篇
  2003年   373篇
  2002年   348篇
  2001年   48篇
  2000年   36篇
  1999年   47篇
  1998年   55篇
  1997年   50篇
  1996年   34篇
  1995年   32篇
  1994年   33篇
  1993年   30篇
  1992年   12篇
  1991年   14篇
  1990年   14篇
  1989年   18篇
  1988年   7篇
  1987年   15篇
  1986年   13篇
  1985年   5篇
  1984年   9篇
  1983年   13篇
  1982年   9篇
  1981年   8篇
  1980年   5篇
  1979年   9篇
  1977年   3篇
  1974年   3篇
  1973年   3篇
  1971年   3篇
排序方式: 共有8454条查询结果,搜索用时 15 毫秒
81.
BackgroundBariatric surgery is well established in adults as the most effective tool for sustained weight loss and reduction of obesity-related co-morbidities, and is an emerging option for adolescents in whom conservative approaches have failed. Narratives are vital in understanding the motivating reasons and psychosocial profiles of adolescents considering bariatric surgery during a developmental period of evolving self-concept, body image sensitivity, peer pressure, and increased opportunity for risky behaviors.ObjectivesTo explore preoperative adolescent patient perspectives on their decision to pursue bariatric surgery, anticipated physical and psychosocial effects, and preparation process.SettingsThe Hospital for Sick Children (SickKids) in Toronto, Ontario, Canada.MethodsWe conducted 14 semi-structured interviews with adolescents (16–18 yr old) 2–4 months before bariatric surgery. A theoretical thematic analysis was conducted with 3 independent reviewers (interrater reliability, Cronbach’s α= .81) and conflicts were resolved through discussion.ResultsPatients’ perspectives are captured in 4 themes: motivation for surgery, effects on health and habits, psychosocial changes, and support systems during preparation. Participants perceived surgery as a tool but not a solution for weight loss. Most were motivated for health and daily functional improvement rather than aesthetic reasons, and some anticipated improved social interactions while maintaining their self-identity. Participants were selective in sharing news of their surgery, and received varying levels of support from families, friends, and healthcare teams.ConclusionAdolescents seem generally prepared for and informed about surgery, with expectations for weight loss and psychosocial improvements, although uncertainty and contradictory thoughts were prevalent. Insights provided by these adolescent patients will help optimize bariatric surgery assessments and support from clinical teams and inform preoperative education for future patients and families.  相似文献   
82.
ObjectivesTo estimate provincial all-cause mortality rates of Saskatchewan people with rheumatoid arthritis (RA) for comparison with the general population over time and between different geographic regions.MethodsSaskatchewan provincial administrative health databases (2001–2019) were utilized as data sources. Two RA case definitions were employed: (1) ≥ 3 physician billing diagnoses, at least 1 from a specialist (rheumatologist, general internist or orthopaedic surgeon) within 2 years; (2) ≥ 1 hospitalization diagnosis (ICD-9 code 714, and ICD-10-CA codes M05, M06). Data from these definitions were combined to create an administrative data RA cohort. All-cause mortality rates across geographic regions, between rural/urban residences and between sexes were examined.ResultsOver an 18-year span, between fiscal-year 2001–2002 and fiscal-year 2018–2019, age- and sex-adjusted mortality rates ranged from 17.10 to 21.04 (95% CI 14.77, 19.44; 18.03, 24.05)/1000 RA person-years, compared with mortality rates for the general Saskatchewan population without RA, which ranged from 9.37 to 10.88 (95% CI 9.23, 9.51; 10.72, 11.05)/1000 person-years. Fiscal-year mortality rate ratios ranged from 1.82 to 2.13 (95% CI 1.56, 2.13; 1.83, 2.46). Provincial mortality rates were higher in men than in women for both general and RA populations. Northern Saskatchewan mortality rates were significantly higher in the general population but did not achieve significance compared with other provincial regions for the RA population. Regression analysis identified age, male sex, RA and geographic region as factors contributing to increased mortality. A trend towards lower mortality rates over time was observed.ConclusionHigher mortality rates were observed in the RA population overall. Men had higher mortality rates, as did residents of Northern Saskatchewan compared with residents of other regions for the general population.  相似文献   
83.
Pertussis is a globally distributed infectious disease that is a significant cause of morbidity and mortality, especially in infants who are too young to be immunized. This disease is common in childhood, and when it occurs during the first few months of life, it leads to hospitalization and, sometimes, death. Brazil has adopted the strategy of maternal immunization against pertussis in late 2014. This study aims to analyze public data on the disease to determine whether there was an impact on the disease burden following the introduction of the vaccine Tdap in pregnant women and its magnitude. We performed a time-series analysis of the incidence of pertussis between October 2010 and January 2019. We stratified the population of interest into three groups: infants aged less than two months old, infants aged two to six months, and infants aged six months to one year, according to Brazil's vaccination schedule. We found a protective effect of maternal vaccination in all age groups, more prominent on the first group. Before the intervention, infants under two months had a higher risk of getting pertussis in comparison with infants two to six months old (HR 1.15, CI 95%: 1.11–1.19). After the intervention, age under two months is a protective factor compared with two to six months (HR 0.90, CI 95%: 0.82–0.98). The pertussis incidence reduced in all age groups and all Brazil's Regions.  相似文献   
84.
85.
The two-pore-domain potassium channels TASK-1, TASK-3 and TASK-5 possess a conserved C-terminal motif of five amino acids. Truncation of the C-terminus of TASK-1 strongly reduced the currents measured after heterologous expression in Xenopus oocytes or HEK293 cells and decreased surface membrane expression of GFP-tagged channel proteins. Two-hybrid analysis showed that the C-terminal domain of TASK-1, TASK-3 and TASK-5, but not TASK-4, interacts with isoforms of the adapter protein 14-3-3. A pentapeptide motif at the extreme C-terminus of TASK-1, RRx(S/T)x, was found to be sufficient for weak but significant interaction with 14-3-3, whereas the last 40 amino acids of TASK-1 were required for strong binding. Deletion of a single amino acid at the C-terminal end of TASK-1 or TASK-3 abolished binding of 14-3-3 and strongly reduced the macroscopic currents observed in Xenopus oocytes. TASK-1 mutants that failed to interact with 14-3-3 isoforms (V411*, S410A, S410D) also produced only very weak macroscopic currents. In contrast, the mutant TASK-1 S409A, which interacts with 14-3-3-like wild-type channels, displayed normal macroscopic currents. Co-injection of 14-3-3ζ cRNA increased TASK-1 current in Xenopus oocytes by about 70 %. After co-transfection in HEK293 cells, TASK-1 and 14-3-3ζ (but not TASK-1ΔC5 and 14-3-3ζ) could be co-immunoprecipitated. Furthermore, TASK-1 and 14-3-3 could be co-immunoprecipitated in synaptic membrane extracts and postsynaptic density membranes. Our findings suggest that interaction of 14-3-3 with TASK-1 or TASK-3 may promote the trafficking of the channels to the surface membrane.  相似文献   
86.
Ghrelin, a regulator of food intake and energy expenditure, has been shown to be associated with insufficient sleep. The goal of the present study was to investigate the effect of a single night of total sleep deprivation on fasting saliva ghrelin and on nocturnal variation of saliva ghrelin concentration. A further aim of the study was to investigate the influence of body mass index on changes in saliva ghrelin levels. Altogether 35 adolescents (18 boys; age: 13.8 ± 1.14 years) were studied on two subsequent days (sleep and total sleep deprivation). Saliva samples were collected during the two experimental nights at 21:00 hours, 01:00 hours and 06:00 hours. Total-ghrelin concentration showed a continuous increase from the evening until 06:00 hours. This increase was blunted significantly (p = 0.003) by total sleep deprivation. Total-ghrelin level was significantly lower (p = 0.02) during total sleep deprivation at 06:00 hours (median 403.6 pg ml−1; 95% confidence interval: 343.1–468.9 pg ml−1) as compared with values during the sleep condition (median 471.2 pg ml−1; 95% confidence interval: 205.4–1578.7 pg ml−1). Acyl-ghrelin levels did not present any change at the three time points, and were not affected by total sleep deprivation. Stratifying the study population according to body mass index (normal weight and overweight/obese groups), the blunting effect of total sleep deprivation was more pronounced in the obese/overweight group (sleep: median 428.2 pg ml−1; 95% confidence interval: 331.3–606.9 pg ml−1 versus total sleep deprivation: median 333.1 pg ml−1; 95% confidence interval: 261.5–412.9 pg ml−1; p = 0.0479). Saliva total-ghrelin concentrations gradually increased during the night, and total sleep deprivation significantly blunted this increase. This blunting effect was mainly observed in subjects with overweight/obesity. The physiological and clinical implications of the present observation are to be clarified by further studies.  相似文献   
87.
The functional restoration approach to treating chronic spinal disability consists of a medically directed, interdisciplinary team approach to physical reconditioning and a cognitive-behavioral crisis intervention procedure for dealing with related psychosocial problems. One- and two-year follow-up studies have demonstrated the clinical efficacy of this approach. The present article describes this approach and summarizes the research documenting its success in treating patients with chronic spinal disability. This article also highlights the pitfalls in misunderstanding and misrepresenting the components of the functional restoration approach when evaluating treatment efficacy.  相似文献   
88.
Clonidine induced hyperphagia and weight gain in monkeys   总被引:2,自引:0,他引:2  
The effect of the -noradrenergic receptor agonist, clonidine, on food intake and weight was examined in ten adult Stumptail macaque monkeys. An intramuscular injection of 0.1 mg/kg of clonidine HCl for seven consecutive days significantly increased food intake from baseline levels throughout treatment. All but two monkeys gained weight during clonidine treatment with seven animals gaining from 5–15% of their original body weight by the end of 1 week.To whom offprint requests should be sent  相似文献   
89.
PURPOSE: There is considerable morphologic overlap between various entities of high-grade gliomas, and, therefore, a further planning of their optimal treatment is a controversial issue. The aim of this study was molecular stratification of morphologically ambiguous high-grade gliomas composed from small cells. Fluorescence in situ hybridization (FISH) with commercially available probes was used for this purpose. EXPERIMENTAL DESIGN: We analyzed a set of 114 high-grade small-cell gliomas that were difficult to interpret diagnostically because of their distinct cytological origin. FISH assay with locus probes for EGFR, p16, PTEN, and 1p and 19q was done. RESULTS: Morphologically uniform high-grade gliomas composed of small cells varied greatly in terms of molecular features and clinical outcome. Four clinically relevant subsets of patients whose tumors showed distinctly different molecular profiles were identified as follows: (a) 13 patients whose tumors exhibited no discernable molecular alterations (5-year survival rate, 83%); (b) 20 patients whose tumors harbored either 1p/19q codeletion or isolated deletion of 19q unaccompanied by other molecular abnormalities (5-year survival rate, 59%); (c) 35 patients whose tumors showed p16 and/or PTEN deletions unaccompanied by EGFR amplification (5-year survival rate, 8%); and (d) 46 patients whose tumors harbored EGFR amplification (5-year survival rate, 0). CONCLUSIONS: The FISH method provides clinically useful information in the molecular analysis of morphologically ambiguous malignant small-cell gliomas that could potentially enhance the quality of patient care.  相似文献   
90.
PURPOSE: Vascular endothelial growth factor (VEGF)-A isa key mediator of angiogenesis in malignant gliomas. Soluble VEGF receptor 1 (sVEGFR-1) can complex VEGF-A and reduce its bioavailability. In several animal models sVEGFR-1 inhibited angiogenesis and tumor growth. We analyzed the levels of endogenous sVEGFR-1 in gliomas of different malignancy grades in relation to tumor vascularity and VEGF-A. EXPERIMENTAL DESIGN: The concentration of sVEGFR-1 was determined by ELISA in 104 gliomas and normal brain. Levels of sVEGFR-1 were compared with malignancy grade, microvessel density, and VEGF-A concentration. Effects of sVEGFR-1 on glioma extract-induced endothelial cell chemotaxis were analyzed in vitro. RESULTS: The concentration of sVEGFR-1 correlated with the malignancy grade and was 12-fold higher in glioblastomas than in diffuse astrocytomas (P < 0.001), with intermediate levels for anaplastic astrocytomas. VEGF-A levels were 30-fold higher (P < 0.001) in glioblastomas than in diffuse astrocytomas. The sVEGFR-1:VEGF-A ratio was 0.27 in glioblastomas and 0.70 in diffuse astrocytomas. Both sVEGFR-1 and VEGF-A correlated with microvessel density (P < 0.001) and with each other (P < 0.001); sVEGFR-1 and VEGF-A also correlated with each other when only glioblastomas were analyzed (P = 0.001). In vitro, recombinant sVEGFR-1 inhibited endothelial cell chemotaxis induced by tumor extracts. CONCLUSIONS: Although absolute levels of sVEGFR-1 are increased in the more malignant gliomas, the sVEGFR-1:VEGF-A ratio is decreased 2.6-fold in glioblastomas compared with diffuse astrocytomas, suggesting that the ensuing increased bioavailability of VEGF-A favors angiogenesis. The inhibition of tumor extract-induced endothelial chemotaxis by sVEGFR-1 suggests that sVEGFR-1 could be useful as an angiogenesis inhibitor in the specific context of human gliomas.  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