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   8929篇
  免费   676篇
  国内免费   585篇
耳鼻咽喉   17篇
儿科学   34篇
妇产科学   60篇
基础医学   350篇
口腔科学   147篇
临床医学   335篇
内科学   468篇
皮肤病学   270篇
神经病学   92篇
特种医学   128篇
外国民族医学   1篇
外科学   789篇
综合类   1286篇
预防医学   1143篇
眼科学   502篇
药学   2159篇
  2篇
中国医学   2224篇
肿瘤学   183篇
  2024年   19篇
  2023年   98篇
  2022年   149篇
  2021年   294篇
  2020年   245篇
  2019年   230篇
  2018年   222篇
  2017年   297篇
  2016年   331篇
  2015年   311篇
  2014年   550篇
  2013年   695篇
  2012年   677篇
  2011年   683篇
  2010年   500篇
  2009年   444篇
  2008年   428篇
  2007年   511篇
  2006年   425篇
  2005年   313篇
  2004年   311篇
  2003年   265篇
  2002年   217篇
  2001年   223篇
  2000年   183篇
  1999年   158篇
  1998年   142篇
  1997年   139篇
  1996年   138篇
  1995年   122篇
  1994年   131篇
  1993年   112篇
  1992年   94篇
  1991年   62篇
  1990年   73篇
  1989年   68篇
  1988年   71篇
  1987年   46篇
  1986年   45篇
  1985年   48篇
  1984年   30篇
  1983年   30篇
  1982年   15篇
  1981年   8篇
  1980年   11篇
  1979年   5篇
  1978年   7篇
  1977年   6篇
  1976年   3篇
  1975年   4篇
排序方式: 共有10000条查询结果,搜索用时 437 毫秒
51.
BACKGROUND: Breast milk contains many immunomodulatory factors (soluble CD14 (sCD14), IgA and cytokines) with the potential to influence infant immune development. OBJECTIVE: To determine if changes in breast milk omega-3 polyunsaturated fatty acid (n-3 PUFA) composition as a result of maternal dietary fish oil supplementation during pregnancy can modify levels of these immunological parameters in breast milk. METHOD: In a randomized controlled trial, 83 atopic women received either 4 g fish oil capsules (containing 3.7 g n-3 PUFA) (n = 40) or 4 g olive oil capsules (n = 43) from 20 weeks gestation until delivery. Breast milk was collected 3 days post-partum and fatty acids were analysed by gas liquid chromatography and IgA, sCD14 and cytokines (IL-5, IL-6, IL-10, TNF-alpha and IFN-gamma) were quantitated by ELISA or time resolved fluorescence (TRF). RESULTS: Omega-3 docosahexaenoic acid (DHA; 22:6n-3) and eicosapentaenoic acid (EPA; 20:5n-3) levels were significantly higher (P < 0.001) in breast milk from women supplemented with fish oil (n = 33, DHA mean 1.15%, SD 0.47% and EPA mean 0.16%, SD 0.07%) than in samples from the control group (n = 40, DHA mean 0.50%, SD 0.17% and EPA mean 0.05%, SD 0.02%). Breast milk arachidonic acid (AA; 20:4n-6) levels were significantly lower (P = 0.045) in the fish oil group (mean 0.55%, SD 0.12%) compared with the control group (mean 0.61%, SD 0.14%). Breast milk IgA was positively correlated with DHA (P = 0.046) and 22:5n-3 (P = 0.003), but inversely correlated with linoleic acid (LA; 18:2n-6) (P=0.034). Levels of sCD14 were also positively correlated with 22:5n-3 (P=0.009). Cytokines involved in IgA synthesis (IL-10 and IL-6) were also significantly correlated with both IgA and n-3 PUFA levels, although there were no differences in the levels of breast milk IgA, sCD14 or cytokines between study groups. CONCLUSION: Supplementation with fish oil during pregnancy significantly alters early post-partum breast milk fatty acid composition. omega-3 PUFA levels were positively associated with IgA and sCD14 levels, suggesting a relationship between fatty acid status and mucosal immune function.  相似文献   
52.
The present study investigated the phototoxic effect of bergamot oil and its photosensitive component, bergapten, on sunburn cell (SBC) production in guinea pig skin. The back skin was pretreated with bergamot oil or bergapten and exposed to monochromatic light under various conditions. After irradiation, skin specimens were excised, and histological sections were prepared. The number of sunburn cells in the interfollicular epidermis was counted. The SBC formation by bergamot oil or bergapten plus UVB radiation was the same as that without pretreatment with any photosensitizer. In contrast, a significant number of SBCs were induced by bergamot oil or bergapten plus UVA radiation, but no SBCs were found after the treatment with UVA alone. The result indicates that bergamot oil or bergapten was photosensitized by UVA irradiation. The SBCs were linearly increased in a UV-dose dependent manner. On the basis of the regression lines, an action spectrum and spectral peak for the photosensitizers plus UVA were obtained. The action spectrum for bergamot oil- and bergapten-induced SBC formation was in the ranges of 325–365 nm and 325–350 nm, and their spectral peaks were at 335–345 nm and 335–350 nm, respectively. The data are in good accordance with those estimated from skin erythema reactions. Therefore, counting SBCs is a very useful parameter for quantitative evaluation of phototoxicity.  相似文献   
53.
The objective of this pilot study was to determine if three common anesthetic drugs have differing effects on the measurement of defibrillation thresholds (DFT) in dogs. The drugs compared were pentobarbital, isoflurane, and halothane. We used six dogs, which were surgically instrumented, in a chronic study design. Each dog had two internal defibrillation patches placed on its heart, which were used to deliver the defibrillation energy. DFT was determined while each dog was anesthetized under each of the listed drugs in a crossover design. This pilot study suggests that differences in DFT due to the anesthetic drugs is not significant in studies with low numbers of animals (halothane 14.5 ± 1.0, isoflurane 14.2 ± 1.0, pentobarbital 12.8 ± 1.0;P = NS; mean ± SE). Tbe variation in DFT between individual animals is much larger than the difference in DFT due to the drugs.  相似文献   
54.
Muscle fiber typing and in vitro contracture tests were performed in 59 patients investigated for susceptibility to malignant hyperthermia (MH). Eighteen patients were found to be susceptible to MH. There was no difference in age or fiber type distribution between MH susceptible and non-susceptible patients. No correlation was found between age and fiber type distribution. Separate analyses for each diagnostic group revealed no relationship between age or fiber type distribution and response to halothane or caffeine. When all caffeine results were pooled, however, there was a significant effect of age on the caffeine specific concentration (the concentration eliciting a contracture of 1 g), but not on the caffeine threshold concentration (the minimal concentration eliciting an increase in tension). It is concluded that age and fiber type distribution have no influence on MH diagnosis, if the protocol of the European MH Group for evaluation of susceptibility to MH is followed.  相似文献   
55.
The antibacterial activity of the volatile oil of Nigella sativa seeds was studied against 37 isolates of Shigella dysenteriae 1, Shigella flexneri, Shigella sonnei and Shigella boydii and 10 strains of Vibrio cholerae and Escherichia coli. Most of the strains were clinically resistant to ampicillin, co-trimoxazole and tetracycline. All the strains tested showed promising sensitivity to the volatile oil. The minimum inhibitory concentration (MIC) of the volatile oil for Shigella, Vibrio and Escherichia strains tested was between 50–400 μg/mL.  相似文献   
56.
57.
栝楼子挥发油的成分分析及其生物活性的初步研究   总被引:4,自引:3,他引:1       下载免费PDF全文
目的:分析栝楼子挥发油成分并检测其生物活性。方法:采用水蒸汽蒸馏法提取,气相色谱-质谱联用法进行成分分析,并分别用测A值和MTT法检测其抑菌和细胞毒生物活性。结果∶从分离的挥发油化合物中,鉴定出42个化合物,占挥发油总相对含量的79.434%。挥发油对金黄色葡萄球菌、大肠杆菌有较好的抑制作用;对真菌红酵母有显著的抑制作用,在800μg·mL-1时抑制率达到90.91%;对肿瘤胃癌细胞株SGC-7901细胞也有显著的细胞毒活性,浓度为50μg·mL-1时,抑制率高达86.13%。结论:首次从挥发油的角度来研究栝楼的药理作用,其挥发油有抑菌活性和对胃癌细胞株SGC-7901细胞有很好的细胞毒活性。  相似文献   
58.
目的探讨不同方法治疗压疮的临床效果。方法将65例患者计Ⅱ~Ⅲ度溃疡84处按基本条件相当原则随机分成A、B、C三组,A组21例28处,伤口采用清创冲洗后,给予康惠尔水胶体敷料;B组23例30处,伤口采用湿润烧伤膏;C组21例26处,清创冲洗后,给予自制凡士林油纱敷料外敷溃疡面处。结果B组愈合率最高,且平均显效时间和愈合时间均较A、C两组明显缩短,且A、B组明显高于C组。结论采用清创冲洗后用湿润烧伤膏是治疗压疮较好的方法之一。  相似文献   
59.
研究了不同预处理条件及油炸温度、真空度、时间对胡萝卜脆片品质的影响.通过响应面分析可知:油炸温度、真空度及油炸时间显著地影响胡萝卜脆片中水分与脂肪质量分数、脆度,其最佳油炸工艺条件为温度100~110℃,真空度0.08~0.09MPa,时间15min.  相似文献   
60.
目的 研究芜菁根挥发油化学成分.方法 采用同时蒸馏萃取(SDE)法提取挥发油,以气相色谱- 质谱联用(GC -MC)技术结合计算机检索对其化学成分进行分离和鉴定,用色谱峰面积归一化法计算各组分的相对含量.结果 从芜菁根挥发油中共鉴定出60种化合物,其含量占挥发油总量的98.36%.其中主要成分为丙酸异丙酯(30.04%)、辛烷(9.95%)、2-甲基庚烷(5.49%)、正壬烷(4.73%)、二甲基三硫醚(2.84%)、3-甲基庚烷(2.55%)、二甲基二硫醚(2.36%)等.结论 研究结果为进一步研究和开发利用芜菁奠定基础.  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