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   1664325篇
  免费   131130篇
  国内免费   8703篇
耳鼻咽喉   21315篇
儿科学   49932篇
妇产科学   45220篇
基础医学   228160篇
口腔科学   47055篇
临床医学   146542篇
内科学   343952篇
皮肤病学   39176篇
神经病学   133624篇
特种医学   67263篇
外国民族医学   353篇
外科学   262959篇
综合类   40138篇
现状与发展   3篇
一般理论   475篇
预防医学   121553篇
眼科学   36312篇
药学   120849篇
  6篇
中国医学   4147篇
肿瘤学   95124篇
  2018年   17087篇
  2017年   13383篇
  2016年   15627篇
  2015年   17481篇
  2014年   24572篇
  2013年   35773篇
  2012年   44406篇
  2011年   47233篇
  2010年   29481篇
  2009年   28719篇
  2008年   44153篇
  2007年   47242篇
  2006年   48217篇
  2005年   46177篇
  2004年   43983篇
  2003年   42959篇
  2002年   40701篇
  2001年   89382篇
  2000年   91876篇
  1999年   76585篇
  1998年   21127篇
  1997年   18617篇
  1996年   19194篇
  1995年   19072篇
  1994年   17620篇
  1993年   16464篇
  1992年   61064篇
  1991年   58601篇
  1990年   56383篇
  1989年   54175篇
  1988年   49902篇
  1987年   48745篇
  1986年   45712篇
  1985年   43873篇
  1984年   32521篇
  1983年   27131篇
  1982年   16236篇
  1981年   14384篇
  1980年   13482篇
  1979年   28496篇
  1978年   20100篇
  1977年   17076篇
  1976年   15206篇
  1975年   16123篇
  1974年   18889篇
  1973年   18054篇
  1972年   16814篇
  1971年   15631篇
  1970年   14216篇
  1969年   13483篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
Abstract

This study was undertaken to compare the concentrations of pro- and anti-angiogenic growth factors, nitric oxide (NO) stable metabolites in maternal serum and embryonic left ventricular (LV) isovolumic relaxation time (IRT, ms) during the first trimester in two groups of women: with pregnancy conceived by assisted reproductive technologies (ART, n?=?39) and normally conceived (control group, n?=?68) pregnancy. The concentration of vasoconstrictor endothelin 1 was 45.5 times more in ART than in control group. On the contrary, the concentrations of NO stable metabolites in ART were 1.9 times less than in control women. The assessment of angiogenic suppressors in ART women demonstrates the decrease in s-endoglin concentration was 1.6 times and in soluble receptor to vascular endothelial growth factor concentration was 2.0 times in comparison with control group. There was a significant increase in LV IRT in ART embryos in comparison to control ones. These data suggest significant changes in pro- anti-angiogenic factors balance and increase in vascular impedance in ART-conceived embryos.  相似文献   
93.
94.
ABSTRACT

Adolescents and young adults smoke waterpipe tobacco (WT) and cigarillos, at least in part, based on erroneous beliefs that these products are safer than cigarettes. To address this challenge, we used a systematic, three-phase process to develop a health communication campaign to discourage WT and cigarillo smoking among at-risk (tobacco users and susceptible non-users) 16- to 25-year-olds. In Phase 1, we used a national phone survey (N = 896) to determine salient message beliefs. Participants reported constituents (i.e., harmful chemicals) emitted by the products were worrisome. In Phase 2, we developed and evaluated four message executions, with varying imagery, tone, and unappealing products with the same constituents, using focus groups (N = 38). Participants rated one execution highly, resulting in our development of a campaign where each message: (1) identified a tobacco product and constituent in the smoke; (2) included an image of an unappealing product containing the constituent (e.g., pesticides, gasoline) to grab attention; and (3) used a humorous sarcastic tone. In Phase 3, we tested the campaign messages (17 intervention and six control) with a nationally representative online survey (N = 1,636). Participants rated intervention and control messages highly with few differences between them. Exposure to messages resulted in significant increases in all risk beliefs from pre to post (< 0.05). For WT, intervention messages increased beliefs about addiction more than control messages (p < 0.05). This systematic, iterative approach resulted in messages that show promise for discouraging WT and cigarillo use.  相似文献   
95.
Digestive Diseases and Sciences - To determine whether the presence of portal vein thrombosis (PVT) where venous flow within the liver may be altered may delay the diagnosis of HCC and be...  相似文献   
96.

Background and aims

It is not known whether non alcoholic fatty liver disease (NAFLD) is a risk factor for diabetes in non obese, non centrally-obese subjects. Our aim was to investigate relationships between fatty liver, insulin resistance and a biomarker score for liver fibrosis with incident diabetes at follow up, in subjects who were neither obese nor centrally-obese.

Methods and results

As many as 70,303 subjects with a body mass index (BMI) < 25 kg/m2 and without diabetes were followed up for a maximum of 7.9 years. At baseline, fatty liver was identified by liver ultrasound, insulin resistance (IR) by homeostatic model assessment of insulin resistance (HOMA-IR) ≥2.0, and central obesity by waist circumference (waist circumference ≥90 cm (men) and ≥85 cm (women). The Fibrosis-4 (FIB-4 score) was used to estimate extent of liver fibrosis. Cox proportional hazards models adjusted for confounders were used to estimate hazard ratios (aHRs) for incident diabetes. As many as 852 incident cases of diabetes occurred during follow up (median [IQR] 3.71 [2.03] years). Mean ± SD BMI was 22.8 ± 1.8 and 21.7 ± 2.0 kg/m2 in subjects with and without diabetes at follow up. In subjects without central obesity and with fatty liver, aHRs (95% CI) for incident diabetes at follow up were 2.17 (1.56, 3.03) for men, and 2.86 (1.50,5.46) for women. Similar aHRs for incident diabetes occurred with fatty liver, IR and the highest quartile of FIB-4 combined, in men; and there was a non significant trend toward increased risk in women.

Conclusions

In normal weight, non-centrally obese subjects NAFLD is an independent risk factor for incident diabetes.  相似文献   
97.
ABSTRACT

Purpose

To investigate the effect of 1% tropicamide on anterior chamber aqueous flare (ACAF) measurements acquired with laser flare meter in patients with pseudoexfoliation.  相似文献   
98.
99.
100.
A cluster randomized experiment was undertaken testing two sets of interventions encouraging enrollment in the Individually Paying Program (IPP), the voluntary component of the Philippines' social health insurance program. In early 2011, 1037 unenrolled IPP‐eligible families in 179 randomly selected intervention municipalities were given an information kit and offered a 50% premium subsidy valid until the end of 2011; 383 IPP‐eligible families in 64 control municipalities were not. In February 2012, the 787 families in the intervention sites who were still IPP‐eligible but had not enrolled had their vouchers extended, were resent the enrollment kits and received SMS reminders. Half the group also received a ‘handholding’ intervention: in the endline interview, the enumerator offered to help complete the enrollment form, deliver it to the insurer's office in the provincial capital, and mail the membership cards. The main intervention raised the enrollment rate by 3 percentage points (ppts) (p = 0.11), with an 8 ppt larger effect (p < 0.01) among city‐dwellers, consistent with travel time to the insurance office affecting enrollment. The handholding intervention raised enrollment by 29 ppts (p < 0.01), with a smaller effect (p < 0.01) among city‐dwellers, likely because of shorter travel times, and higher education levels facilitating unaided completion of the enrollment form. Copyright © The World Bank Health Economics © 2015 John Wiley & Sons, Ltd.  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