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   228272篇
  免费   17807篇
  国内免费   6508篇
耳鼻咽喉   2795篇
儿科学   10153篇
妇产科学   2950篇
基础医学   28641篇
口腔科学   4389篇
临床医学   23243篇
内科学   29937篇
皮肤病学   2147篇
神经病学   11912篇
特种医学   5580篇
外国民族医学   25篇
外科学   20285篇
综合类   33628篇
现状与发展   12篇
一般理论   26篇
预防医学   21559篇
眼科学   4952篇
药学   23295篇
  78篇
中国医学   10451篇
肿瘤学   16529篇
  2024年   359篇
  2023年   3283篇
  2022年   5527篇
  2021年   9529篇
  2020年   8858篇
  2019年   8507篇
  2018年   8177篇
  2017年   7440篇
  2016年   7682篇
  2015年   7714篇
  2014年   13438篇
  2013年   14150篇
  2012年   11828篇
  2011年   13357篇
  2010年   11250篇
  2009年   11087篇
  2008年   11054篇
  2007年   12109篇
  2006年   10648篇
  2005年   10232篇
  2004年   8739篇
  2003年   7563篇
  2002年   5632篇
  2001年   5551篇
  2000年   4588篇
  1999年   4142篇
  1998年   3016篇
  1997年   2668篇
  1996年   2714篇
  1995年   2540篇
  1994年   2278篇
  1993年   2041篇
  1992年   1760篇
  1991年   1573篇
  1990年   1313篇
  1989年   1233篇
  1988年   1131篇
  1987年   901篇
  1986年   676篇
  1985年   864篇
  1984年   847篇
  1983年   532篇
  1982年   651篇
  1981年   564篇
  1980年   505篇
  1979年   434篇
  1978年   380篇
  1977年   271篇
  1976年   346篇
  1975年   199篇
排序方式: 共有10000条查询结果,搜索用时 265 毫秒
31.
32.
《Vaccine》2016,34(15):1773-1777
BackgroundThere are conflicting findings regarding the impact of residential mobility on immunisation status. Our aim was to determine whether there was any association between residential mobility and take up of immunisations and whether they were delayed in administration.MethodsWe carried out a cohort analysis of children born in Wales, UK. Uptake and time of immunisation were collected electronically. We defined frequent movers as those who had moved: 2 or more times in the period prior to the final scheduled on-time date (4 months) for 5 in 1 vaccinations; and 3 or more times in the period prior to the final scheduled on-time date (12 months) for MMR, pneumococcal and meningitis C vaccinations. We defined immunisations due at 2–4 months delayed if they had not been given by age 1; and those due at 12–13 months as delayed if they had not been given by age 2.ResultsUptake rates of routine immunisations and whether they were given within the specified timeframe were high for both groups. There was no increased risk (odds ratios (95% confidence intervals) between frequent movers compared to non-movers for the uptake of: primary MMR 1.08 (0.88–1.32); booster Meningitis C 1.65 (0.93–2.92); booster pneumococcal 1.60 (0.59–4.31); primary 5 in 1 1.28 (0.92–1.78); and timeliness: primary MMR 0.92 (0.79–1.07); booster Meningitis C 1.26 (0.77–2.07); booster pneumococcal 1.69 (0.23–12.14); and primary 5 in 1 1.04 (0.88–1.23).DiscussionFindings suggest that children who move home frequently are not adversely affected in terms of the uptake of immunisations and whether they were given within a specified timeframe. Both were high and may reflect proactive behaviour in the primary healthcare setting to meet Government coverage rates for immunisation.  相似文献   
33.
34.
ARID1A, one of the subunits in SWI/SNF chromatin remodeling complex, is frequently mutated in gastric cancers with microsatellite instability (MSI). The most frequent MSI in solid‐type poorly differentiated adenocarcinoma (PDA) has been reported, but the SWI/SNF complex status in solid‐type PDA is still largely unknown. We retrospectively analyzed 54 cases of solid‐type PDA for the expressions of mismatch repair (MMR) proteins (MLH1, PMS2, MSH2, and MSH6), SWI/SNF complex subunits (ARID1A, INI1, BRG1, BRM, BAF155, and BAF170) and EBER, and mutations in KRAS and BRAF. We analyzed 40 cases of another histological type of gastric cancer as a control group. The solid‐type PDAs showed coexisting glandular components (76%), MMR deficiency (39%), and complete/partial loss of ARID1A (31%/7%), INI1 (4%/4%), BRG1 (48%/30%), BRM (33%/33%), BAF155 (13%/41%), and BAF170 (6%/2%), EBER positivity (4%), KRAS mutation (2%), and BRAF mutation (2%). Compared to the control group, MMR deficiency and losses of ARID1A, BRG1, BRM, and BAF155 were significantly frequent in solid‐type PDAs. Mismatch repair deficiency was associated with the losses of ARID1A, BRG1, and BAF155 in solid‐type PDAs. In the MMR‐deficient group, solid components showed significantly more frequent losses of ARID1A, BRG1, BRM, and BAF155 compared to glandular components (P = .0268, P = .0181, P = .0224, and P = .0071, respectively). In the MMR‐proficient group, solid components showed significantly more frequent loss of BRG1 compared to glandular components (P = .012). In conclusion, solid‐type PDAs showed frequent losses of MMR proteins and the SWI/SNF complex. We suggest that loss of the SWI/SNF complex could induce a morphological shift from differentiated‐type adenocarcinoma to solid‐type PDA.  相似文献   
35.
36.
37.
Academic output is just one aspect of a successful career as a plastic surgeon. However, for those with a strong interest in academia, the academic output of a department will likely be a key factor when deciding how to rank jobs. The aim of this study was to quantify and rank the academic output of plastic surgery units across the UK and Ireland. The Institute for Scientific Information (ISI) Web of Science Bibliometric analysis tool was used to collate cumulative (1950–2016), 10 year (2006–2016) and 3 years (2013–2015) research output data for plastic surgery units in the UK and Ireland. Sixty-six plastic surgery units were identified. Departments were ranked for each time period according to the number of papers produced, number of citations (Nc) and h-index (a measure of the impact of scientific output). The top 3 departments for number of papers in the last 10 years were The Royal Free Hospital, London (226) Broomfield Hospital, Chelmsford (218), and Morriston Hospital and Swansea (188). The top 3 for h-number were The Royal Free Hospital (21) Wythenshawe Hospital, Manchester (18) and Morriston Hospital (17). Academic output varies across plastic surgery units in the UK and Ireland. A number of departments have consistently maintained high academic outputs across the years and will be of interest to surgeons hoping to pursue a career in academia.  相似文献   
38.
Although an inverse relationship between body mass index (BMI) and baroreflex sensitivity (BRS) was found, the effect of waist circumference (WC) on BRS is still inconclusive. The contradictory results of previous studies may be related to the heterogeneity and relatively small sample size of the subjects examined. The aim of this population-based study was to investigate whether the influence of increased WC is more detrimental to BRS than BMI. A total of 760 community dwellers were recruited and they were classified into Q1 (n = 189), Q2 (n = 183), Q3 (n = 192) and Q4 (n = 196) groups, based on WC quartiles. Spontaneous BRS was determined by spectral α coefficient method. Valsalva ratio was the longest RR interval after release of Valsalva maneuver divided by the shortest RR interval during maneuver. Cardiac autonomic function was calculated by power spectrum of heart rate in low and high frequency (LF, 0.04–0.15 Hz; HF, 0.15–0.40 Hz), and LF/HF ratio in supine position for five minutes. There were significant differences in spontaneous BRS and Valsalva ratio among different WC groups. In multivariate analysis, obesity was inversely associated with spontaneous BRS and Valsalva ratio. However, these inverse relationships became insignificant after further adjustment for WC quartiles. In contrast, Q4 vs. Q1, Q3 vs. Q1 and Q2 vs. Q1 of WC were inversely related to spontaneous BRS. Q4 vs. Q1 and Q3 vs. Q1 of WC were negatively associated with the Valsalva ratio. In conclusion, increased and even high-normal WC had a stronger adverse effect on BRS than BMI, independent of cardio-metabolic risk factors.  相似文献   
39.
目的探讨中国9个城市(简称九市)4~7岁儿童乳恒牙替换及其与体格生长的关系,分析恒牙发育长期变化趋势。方法采用分层整群抽样的方法,以4~7岁儿童为调查对象,于2015年6—10月在北京、哈尔滨、西安(北片),上海、南京、武汉(中片),广州、福州、昆明(南片)九市进行横断面调查,共37973名儿童,其中男19035名,女18938名。6岁以下每6个月为1组,6~<7岁1岁为1组。现场检查乳牙脱落、恒牙萌出情况,测量身高、体重等,并依据2009年中国儿童生长标准计算体格指标Z分值。采用Probit概率单位回归方法计算换牙年龄。不同性别、地区、年龄分组组间比较采用χ2检验或t检验。并利用1995年中国九市儿童体格发育调查中乳恒牙替换相关数据,分析恒牙发育的长期变化趋势。结果九市37973名儿童随着年龄增长换牙率逐渐增加,从4.0~<4.5岁的0.6%(42/7568)增长至5.5~<6.0岁的30.3%(2295/7583),6.0~<7.0岁达到74.5%(5680/7627)。除4.0~4.5岁组外,无论城郊男童换牙率均低于女童(P均<0.05);城区换牙率(男5.5~<6.0岁、女4.5~<5.0岁组之后)略高于郊区,如6.0~<7.0岁组男童城郊分别为74.2%(1427/1924)、69.2%(1305/1885)(χ2=11.446,P<0.01)。九市儿童换牙年龄为6.00(95%CI:5.98~6.01)岁。换牙年龄的第3~97百分位变化范围为4.88~7.11岁。女童中位换牙年龄(5.94岁)早于男童(6.06岁);城区(5.94岁)早于郊区(6.05岁);北片(5.97岁)、中片地区(5.97岁)略早于南片地区(6.05岁)。已换牙儿童体重、身高、体质指数Z分值均高于未换牙儿童(0.35±1.17比0.03±1.13、0.32±1.00比0.03±1.02、0.23±1.16比0.04±1.13,t=20.81、21.67、12.09,P均<0.05)。与1995年相比,2015年5.0岁以后儿童换牙率明显提高,如城区男童6.0~<7.0岁组1995年为63.8%(1146/1796),2015年提高至74.2%(1427/1924)(χ2=46.748,P<0.01);中位换牙年龄2015年较1995年提前0.24岁。结论九市4~7岁儿童换牙年龄女童早于男童,城区早于郊区,北、中片早于南片地区。换牙早晚与体格生长水平有关。近20年换牙年龄存在小幅提前趋势。  相似文献   
40.

Background

It has been reported that particulate matter (PM) is associated with cardiovascular diseases (CVD) while metabolic syndrome is also an important risk factor for CVD. However, few studies have investigated the epidemiological association between PM and metabolic syndrome.

Objective

To investigate the association between one-year exposure to PM with an aerodynamic diameter <2.5?μm (PM2.5) and the risk of metabolic syndrome in Korean adults without CVD.

Methods

Exposure to PM2.5 was assessed using a Community Multiscale Air Quality (CMAQ) model. Metabolic syndrome was defined by National Cholesterol Education Program Adult Treatment Panel III. Andersen and Gill model with time-varying covariates, considering recurrent events, was used to investigate the association between one-year average PM2.5 and the risk of incident metabolic syndrome in 119,998 adults from the national health screening cohort provided by Korea National Health Insurance from 2009 to 2013.

Results

Higher risk of metabolic syndrome, waist-based obesity, hypertension, hypertriglyceridemia, low HDL cholesterol, and hyperglycemia were significantly associated with a 10-μg/m3 increase in PM2.5 [adjusted hazard ratio (HR): 1.070, 1.510, 1.499, 1.468, 1.627 and 1.380, respectively]. In addition, the risk of metabolic syndrome associated with PM2.5 exposure was significant in the consistently obese group (obese at baseline and endpoint).

Conclusion

Exposure to one-year average PM2.5 is associated with an increased risk of metabolic syndrome and its components in adults without CVD. These associations are particularly prominent in the consistently obese group (obese at baseline and endpoint). Our findings indicate that PM2.5 affects the onset of MS and its components which may lead to increase the risk of CVD.  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