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   434篇
  免费   22篇
  国内免费   14篇
耳鼻咽喉   1篇
儿科学   7篇
妇产科学   5篇
基础医学   43篇
口腔科学   9篇
临床医学   32篇
内科学   69篇
皮肤病学   11篇
神经病学   8篇
特种医学   16篇
外科学   12篇
综合类   63篇
预防医学   100篇
眼科学   3篇
药学   49篇
中国医学   27篇
肿瘤学   15篇
  2023年   3篇
  2022年   19篇
  2021年   17篇
  2020年   13篇
  2019年   14篇
  2018年   8篇
  2017年   11篇
  2016年   10篇
  2015年   16篇
  2014年   14篇
  2013年   33篇
  2012年   19篇
  2011年   25篇
  2010年   15篇
  2009年   21篇
  2008年   24篇
  2007年   26篇
  2006年   22篇
  2005年   15篇
  2004年   9篇
  2003年   7篇
  2002年   16篇
  2001年   10篇
  2000年   7篇
  1999年   5篇
  1998年   4篇
  1997年   10篇
  1996年   3篇
  1995年   5篇
  1994年   4篇
  1993年   7篇
  1992年   4篇
  1991年   5篇
  1990年   2篇
  1989年   4篇
  1988年   4篇
  1987年   4篇
  1986年   3篇
  1985年   7篇
  1984年   5篇
  1983年   4篇
  1981年   2篇
  1980年   3篇
  1979年   1篇
  1978年   1篇
  1976年   1篇
  1975年   2篇
  1974年   1篇
  1973年   1篇
  1972年   2篇
排序方式: 共有470条查询结果,搜索用时 15 毫秒
1.
《Nutrition reviews》1987,45(10):246-248
Increasing dietary 18:2 n-6/18:3 n-3 causes similar relative changes in fatty acid profiles of phosphatidylethanolamine and phosphatidylcholine from rat neural and erythrocyte membranes.  相似文献   
2.
采用同种脂肪提取液复制犬呼吸窘迫综合征模型,观察前列腺素E_1(PGE_1)对其治疗作用。结果表明,PGE_1可改善该模型的低氧血症,降低肺毛细血管通透性,减轻肺水肿,其减轻肺损伤的机理与其抑制多形核白细胞粘附、氧自由基产生及保护Ⅱ-型肺泡上皮细胞等有关。  相似文献   
3.
Summary: Linear unsaturated nylons 6 u18 and 18 u18 have been made containing a double bond in the center of the diacid segment with potential for additional functionalization. Solution state NMR showed the presence of a small portion of cis amide units. Solid state NMR verified the presence of the double bond in the bulk, and that the polyamides were present in the α‐crystalline form. Thermal stability was comparable to linear saturated nylons, and the melting and crystallization temperatures of the unsaturated nylons were lower compared to the saturated analogs.

DSC heating and cooling thermograms for nylons 6 u18 and 18 u18.  相似文献   

4.
目的 探讨不饱和脂肪酸二十二碳六烯酸 (DHA)是否能够逆转人乳腺癌细胞的多药耐药性(MDR)。方法 采用MTT法对DHA和阿霉素合用时肿瘤细胞的半数抑制率 (IC50 )进行检测。结果 DHA(10 μg/ml)组能提高MCF 7/R细胞株对阿霉素敏感性 3.2倍 ,DHA(2 0 μg/ml)组提高 5 .1倍 ,均有非常显著性差异 (P <0 .0 1)。结论 DHA能部分逆转乳腺癌耐药细胞对阿霉素的耐药性  相似文献   
5.
Bile salts and synthetic surfactants have been used to promote nasal absorption of peptide drugs. Although a marked increase in nasal absorption has been achieved, this may not be adequate and the possibility of adjuvant-induced membrane toxicity exists. The present study employs a rat in situ nasal perfusion technique and mixed micelles between sodium glycocholate (NaGC) and various lipids as potential nasal absorption enhancers of a stable model dipeptide, [D-Arg2]kyotorphin. NaGC alone enhanced the nasal absorption of the dipeptide in a concentration-dependent manner. When linoleic acid was added to form mixed micelles with NaGC, the absorption was further enhanced (P < 0.01). The effect of mixed micelles was synergistic and much greater than with single adjuvants. Increasing ionic strength was found to increase the adjuvant activity of both NaGC and NaGC–lipid mixed micelles. Structure of the lipid component of the mixed micelles also affected the adjuvant potency. Oleic acid, a cis-unsaturated fatty acid, was more effective than elaidic acid, the trans-isomer, whereas cis-linoleic acid and trans-linolelaidic acid were equally effective ( = 0.05). Mixed micelles of mono-glycerides such as monoolein and monolinolein were also more effective than NaGC alone ( = 0.05). Micellar solubilization of these polar lipids by NaGC appears to be important for nasal absorption enhancement to occur. Reversal of the membrane permeability was also observed within approximately 20–40 min after removal of the adjuvants from the rat nasal cavity. These observations are similar to the effects of mixed micelles on the rectal mucosa and may involve the same mechanism.  相似文献   
6.
Background. The “obesogenicity” of modern environments is fueling the obesity pandemic. We describe a framework, known as ANGELO (analysis grid for environments linked to obesity), which is a conceptual model for understanding the obesogenicity of environments and a practical tool for prioritizing environmental elements for research and intervention.Methods: Development of the ANGELO framework. The basic framework is a 2 × 4 grid which dissects the environment into environmental size (micro and macro) by type: physical (what is available), economic (what are the costs), political (what are the “rules”), and sociocultural (what are the attitudes and beliefs). Within this grid, the elements which influence food intake and physical activity are characterized as obe sogenic or “leptogenic” (promoting leanness).Results: Application of the ANGELO framework. The ANGELO framework has been piloted at the population level (island communities) to prioritize the settings/sectors for intervention and at the setting level (fast food outlets) to prioritize research needs and interventions. Environmental elements were prioritized by rating their validity (evidence of impact), relevance (to the local context), and potential changeability.Conclusions. The ANGELO framework appears to be a flexible and robust instrument for the needs analysis and problem identification stages of reducing the obe sogenicity of modern environments.  相似文献   
7.
以改性二苯醚树脂为原料,合成了一种新颖不饱和聚酯型无溶剂浸渍绝缘漆。它耐高温达到H级,固化速度快,贮存周期长,挥发率低。讨论了促进剂和挥发分抑制剂对无溶剂浸渍漆性能的影响,以及促进机理和抑制机理。结果证明了促进剂可以大大缩短固化时间,挥发分抑制剂在适当配比下,能够降低苯乙烯的挥发。  相似文献   
8.
The importance of the in utero environment as a contributor to later life metabolic disease has been demonstrated in both human and animal studies. In this review, we consider how disruption of normal fetal growth may impact skeletal muscle metabolic development, ultimately leading to insulin resistance and decreased insulin sensitivity, a key precursor to later life metabolic disease. In cases of intrauterine growth restriction (IUGR) associated with hypoxia, where the fetus fails to reach its full growth potential, low birth weight (LBW) is often the outcome, and early in postnatal life, LBW individuals display modifications in the insulin-signaling pathway, a critical precursor to insulin resistance. In this review, we will present literature detailing the classical development of insulin resistance in IUGR, but also discuss how this impaired development, when challenged with a postnatal Western diet, may potentially contribute to the development of later life insulin resistance. Considering the important role of the skeletal muscle in insulin resistance pathogenesis, understanding the in utero programmed origins of skeletal muscle deficiencies in insulin sensitivity and how they may interact with an adverse postnatal environment, is an important step in highlighting potential therapeutic options for LBW offspring born of pregnancies characterized by placental insufficiency.  相似文献   
9.
ObjectiveDietary strategies in heart failure (HF) are focused on sodium and fluid restriction to minimize the risk for acute volume overload episodes. However, the importance of dietary factors beyond sodium intake in the prognosis of the disease is uncertain. The purpose of this study was to evaluate the association of macro- and micronutrients intake on 1-y mortality in patients with HF.MethodsA secondary analysis of 203 patients with chronic HF enrolled in a randomized trial of sodium reduction was completed. Patients with a complete 3-d food record at baseline were included in this analysis (N = 118); both control and intervention arms were combined. Three-d mean dietary intake was estimated. Cox multivariable regression analysis was used to evaluate the association between dietary factors and 1-y mortality.ResultsAmong the 118 included patients, 54% were men, median (25th–75th percentiles) age 66 y (52–75 y), median ejection fraction 45% (30%–60%), and ischemic etiology present in 49% of patients. The association with 1-y mortality was significant for both polyunsaturated fatty acids (PUFA; adjusted hazard ratio [HR], 0.67; 95% confidence interval [CI]. 0.51–0.86 for intake as percentage of daily energy) and saturated fatty acids (SFA; adjusted HR, 1.15; 95% CI, 1.03–1.30 for intake as percentage of daily energy). Median of intake as percentage of daily energy was 5.3% for PUFAs and 8.2% for SFAs.ConclusionsIntake of PUFAs and SFAs was independently associated with 1-y all-cause mortality in patients with chronic HF. Limiting dietary SFA and increasing PUFA intake may be advisable in this population.  相似文献   
10.
Summary A geographically based sample of 1069 Hispanic and non-Hispanic white persons aged 20–74 years, living in southern Colorado and who tested normal on an oral glucose tolerance test (World Health Organization criteria) were evaluated to determine associations of dietary factors with fasting serum insulin concentrations. Subjects were seen for up to three visits from 1984 to 1992. A 24-h diet recall and fasting insulin concentrations were collected at all visits. In longitudinal data analysis, lower age, female gender, Hispanic ethnicity, higher body mass index, higher waist circumference, and no vigorous activity were significantly related to higher fasting insulin concentrations. High total and saturated fat intake were associated with higher fasting insulin concentrations after adjusting for age, sex, ethnicity, body mass index, waist circumference, total energy intake and physical activity. Dietary fibre and starch intake were inversely associated with fasting insulin concentrations. No associations with fasting insulin concentrations were observed for monounsaturated fat, polyunsaturated fat, sucrose, glucose and fructose intake. Associations were similar in men and women and for active and inactive subjects, though associations of fibre and starch intake with insulin concentrations were strongest in lean subjects. These findings support animal studies and a limited number of human population studies which have suggested that increased saturated and total fat intake and decreased fibre and starch intake increase fasting insulin concentrations and may also increase insulin resistance. These findings, which relate habitual macronutrient consumption to hyperinsulinaemia in a large population, may have implications for studies attempting primary prevention of non-insulin-dependent diabetes mellitus. [Diabetologia (1997) 40: 430–438] Received: 6 August 1996 and in revised form: 17 December 1996  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