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   1712149篇
  免费   129473篇
  国内免费   5737篇
耳鼻咽喉   21928篇
儿科学   55963篇
妇产科学   46490篇
基础医学   241937篇
口腔科学   49131篇
临床医学   154324篇
内科学   334027篇
皮肤病学   38869篇
神经病学   131246篇
特种医学   64772篇
外国民族医学   249篇
外科学   258707篇
综合类   45837篇
现状与发展   26篇
一般理论   531篇
预防医学   126080篇
眼科学   40548篇
药学   127266篇
  47篇
中国医学   6830篇
肿瘤学   102551篇
  2021年   12744篇
  2019年   14310篇
  2018年   20709篇
  2017年   16174篇
  2016年   17403篇
  2015年   20303篇
  2014年   27929篇
  2013年   39797篇
  2012年   55521篇
  2011年   58183篇
  2010年   34894篇
  2009年   32477篇
  2008年   53497篇
  2007年   56822篇
  2006年   57088篇
  2005年   54153篇
  2004年   51896篇
  2003年   49211篇
  2002年   47125篇
  2001年   92325篇
  2000年   93981篇
  1999年   76967篇
  1998年   18980篇
  1997年   16457篇
  1996年   16555篇
  1995年   16772篇
  1994年   15340篇
  1993年   14058篇
  1992年   57342篇
  1991年   55294篇
  1990年   52986篇
  1989年   50753篇
  1988年   46135篇
  1987年   44938篇
  1986年   42222篇
  1985年   39989篇
  1984年   29315篇
  1983年   24848篇
  1982年   13842篇
  1979年   25469篇
  1978年   17528篇
  1977年   14849篇
  1976年   13829篇
  1975年   14513篇
  1974年   17601篇
  1973年   16907篇
  1972年   15664篇
  1971年   14433篇
  1970年   13416篇
  1969年   12504篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
IntroductionScales for predicting venous thromboembolism (VTE) recurrence are useful for deciding the duration of the anticoagulant treatment. Although there are several scales, the most appropriate for our setting has not been identified. For this reason, we aimed to validate the DASH prediction score and the Vienna nomogram at 12 months.MethodsThis was a retrospective study of unselected consecutive VTE patients seen between 2006 and 2014. We compared the ability of the DASH score and the Vienna nomogram to predict recurrences of VTE. The validation was performed by stratifying patients as low-risk or high-risk, according to each scale (discrimination) and comparing the observed recurrence with the expected rate (calibration).ResultsOf 353 patients evaluated, 195 were analyzed, with an average age of 53.5 ± 19 years. There were 21 recurrences in 1 year (10.8%, 95% CI: 6.8%-16%). According to the DASH score, 42% were classified as low risk, and the rate of VTE recurrence in this group was 4.9% (95% CI: 1.3%-12%) vs. the high-risk group that was 15% (95% CI: 9%-23%) (p <.05). According to the Vienna nomogram, 30% were classified as low risk, and the rate of VTE recurrence in the low risk group vs. the high risk group was 4.2% (95% CI:0.5%-14%) vs. 16.2% (95% CI: 9.9%-24.4%) (p <.05).ConclusionsOur study validates the DASH score and the Vienna nomogram in our population. The DASH prediction score may be the most advisable, both because of its simplicity and its ability to identify more low-risk patients than the Vienna nomogram (42% vs. 30%).  相似文献   
993.
994.
995.
In insects, lipid digestion is controversial because insects have no bile salts to solubilize dietary lipids. One hypothesis is that a secretory type of phospholipase A2 (sPLA2) provides lysophospholipid (LPL) from dietary phospholipids (PLs). We identified a sPLA2, Se‐sPLA2, in beet armyworm, Spodoptera exigua, that hydrolyses PLs at sn‐2. Our goal was to investigate its role in lipid digestion. Se‐sPLA2 was expressed in the entire alimentary canal. Incubating the isolated midgut in a cell culture medium led to secretion of Se‐sPLA2 and other proteins. Ex vivo RNA interference (RNAi) of Se‐sPLA2 expression in isolated midgut culture led to significantly decreased Se‐sPLA2 secretion into the medium. Feeding double‐stranded RNA specific to Se‐sPLA2 to larvae suppressed sPLA2 activity in gut contents. A recombinant Se‐sPLA2 was susceptible to benzylideneacetone (BZA), a specific PLA2 inhibitor. After feeding BZA to larvae, we recorded significant decreases in gut content sPLA2 activity, body growth and total haemolymph lipid contents. RNAi against Se‐sPLA2 resulted in reduced digestibility. Addition of a specific LPL, 1‐palmitoyl‐sn‐glycero‐3‐phosphocholine, to BZA‐treated larvae rescued digestibility and larval growth. These results strongly bolster our hypothesis that Se‐sPLA2 secreted from the midgut acts in lipid digestion by providing necessary LPL to solubilize dietary neutral lipids.  相似文献   
996.

Purpose

Chest wall pain is an uncommon but bothersome late complication following lung stereotactic body radiation therapy. Despite numerous studies investigating predictors of chest wall pain, no clear consensus has been established for a chest wall constraint. The aim of our study was to investigate factors related to chest wall pain in a homogeneous group of patients treated at our institution.

Patients and methods

All 122 patients were treated with the same stereotactic body radiation therapy regimen of 48 Gy in three fractions, seen for at least 6 months of follow-up, and planned with heterogeneity correction. Chest wall pain was scored according to the Common Terminology Criteria for Adverse Events classification v3.0. Patient (age, sex, diabetes, osteoporosis), tumour (planning target volume, volume of the overlapping region between planning target volume and chest wall) and chest wall dosimetric parameters (volumes receiving at least 30, 40, and 50 Gy, the minimal doses received by the highest irradiated 1, 2, and 5 cm3, and maximum dose) were collected. The correlation between chest wall pain (grade 2 or higher) and the different parameters was evaluated using univariate and multivariate logistic regression.

Results

Median follow-up was 18 months (range: 6–56 months). Twelve patients out of 122 developed chest wall pain of any grade (seven with grade 1, three with grade 2 and two with grade 3 pain). In univariate analysis, only the volume receiving 30 Gy or more (P = 0.034) and the volume of the overlapping region between the planning target volume and chest wall (P = 0.038) significantly predicted chest wall pain, but these variables were later proved non-significant in multivariate regression.

Conclusion

Our analysis could not find any correlation between the studied parameters and chest wall pain. Considering our present study and the wide range of differing results from the literature, a reasonable conclusion is that a constraint for chest wall pain is yet to be defined.  相似文献   
997.
998.
999.
BACKGROUND Approximately 20% of patients with neuroendocrine tumours(NETs) develop carcinoid syndrome(CS),characterised by flushing and diarrhoea.Somatostatin analogues or telotristat can be used to control symptoms of CS through inhibition of serotonin secretion.Although CS is often the cause of diarrhoea among patients with gastroenteropancreatic NETs(GEP-NETs),other causes to consider include pancreatic enzyme insufficiency(PEI),bile acid malabsorption and small intestinal bacterial overgrowth.If other causes of diarrhoea unrelated to serotonin secretion are mistaken for CS diarrhoea,these treatments may be ineffective against the diarrhoea,risking detrimental effects to patient quality of life.AIM To identify and synthesise qualitative and quantitative evidence relating to the differential diagnosis of diarrhoea in patients with GEP-NETs.METHODS Electronic databases(MEDLINE,Embase and the Cochrane Library) were searched from inception to September 12,2018 using terms for NETs and diarrhoea.Congresses,systematic literature review bibliographies and included articles were also hand-searched.Any study designs and publication types were eligible for inclusion if relevant data on a cause(s) of diarrhoea in patients with GEP-NETs were reported.Studies were screened by two independent reviewers at abstract and full-text stages.Framework synthesis was adapted to synthesise quantitative and qualitative data.The definition of qualitative data was expanded to include all textual data in any section of relevant publications.RESULTS Forty-seven publications(44 studies) were included,comprising a variety of publication types,including observational studies,reviews,guidelines,case reports,interventional studies,and opinion pieces.Most reported on PEI on/after treatment with somatostatin analogs;9.5%-84% of patients with GEP-NETs had experienced steatorrhoea or confirmed PEI.Where reported,14.3%–50.7% of patients received pancreatic enzyme replacement therapy.Other causes of diarrhoea reported in patients with GEP-NETs included bile acid malabsorption(80%),small intestinal bacterial overgrowth(23.6%-62%),colitis(20%) and infection(7.1%).Diagnostic approaches included faecal elastase,breath tests,tauroselcholic(selenium-75) acid(Se HCAT) scan and stool culture,although evidence on the effectiveness or diagnostic accuracy of these approaches was limited.Assessment of patient history or diarrhoea characteristics was also reported as initial approaches for investigation.From the identified evidence,if diarrhoea is assumed to be CS diarrhoea,consequences include uncontrolled diarrhoea,malnutrition,and perceived ineffectiveness of CS treatment.Approaches for facilitating differential diagnosis of diarrhoea include improving patient and clinician awareness of non-CS causes and involvement of a multidisciplinary clinical team,including gastroenterologists.CONCLUSION Diarrhoea in GEP-NETs can be multifactorial with misdiagnosis leading to delayed patient recovery and inefficient resource use.This systematic literature review highlights gaps for further research on prevalence of non-CS diarrhoea and suitability of diagnostic approaches,to determine an effective algorithm for differential diagnosis of GEP-NET diarrhoea.  相似文献   
1000.
Objective. To examine pharmacy students’ performance on and perceptions regarding the use of an interactive online tool for practicing to take objective structured clinical examinations (OSCEs).Methods. The Monash OSCE Virtual Experience (MOVE), an online module consisting of 20 pharmacy case scenarios with virtual patients, was piloted with final-year pharmacy students at Monash University campuses in Australia and Malaysia. A mixed methods approach that included reviewing user attempts and comparing grades, collecting student-administered questionnaires, and holding focus groups was used to examine students’ perception and performance.Results. More than 99% of all students attempted at least one online case scenario in preparation for their final in-person OSCE, and 81% attempted all 20 scenarios two or more times. Ninety percent of students at the Malaysia campus and 70% of students at the Australia campus reported that MOVE was a helpful study tool for their OSCE preparation. However, a raw comparison of user attempts and OSCE grades did not find a direct correlation between online module attempts and assessment grades. Self-administered questionnaire and focus group results indicated that MOVE prepared students for targeted and time-restricted history-taking and problem-solving skills. Overall, students perceived MOVE to be a useful learning tool and a less overwhelming learning experience than were face-to-face sessions. Nevertheless, students still preferred face-to-face OSCE practice with simulated patients over online practice with virtual patients.Conclusion. The Monash OSCE Virtual Experience was perceived by our students as a flexible and useful online learning aid in preparing for their final-year OSCE However, there was no direct correlation between online practice attempts and students’ exam grades.  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