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   142篇
  免费   7篇
  国内免费   7篇
化学   123篇
综合类   8篇
数学   7篇
物理学   18篇
  2023年   2篇
  2022年   25篇
  2021年   12篇
  2020年   10篇
  2019年   3篇
  2018年   2篇
  2017年   5篇
  2016年   7篇
  2015年   7篇
  2014年   6篇
  2013年   8篇
  2012年   4篇
  2011年   9篇
  2010年   2篇
  2009年   7篇
  2008年   5篇
  2007年   6篇
  2006年   3篇
  2004年   2篇
  2003年   3篇
  2001年   4篇
  2000年   5篇
  1999年   3篇
  1998年   3篇
  1997年   4篇
  1996年   1篇
  1995年   3篇
  1994年   2篇
  1991年   1篇
  1990年   1篇
  1988年   1篇
排序方式: 共有156条查询结果,搜索用时 723 毫秒
71.
为观察多甙颗粒剂对复发性阿弗他溃疡患者治疗前后红细胞免疫功能和血清中CR1免疫调节因子活性的调节作用,采用红细胞-酵母免疫黏附法测定了235例复发性阿弗他溃疡患者RBC-c3bRR及血清中CR1免疫调节因子。结果表明,红细胞RBC-c3b受体花环率与对照组比较,组1有显著差异(P<0.01),组1与组2 RBC-c3b受体花环率对比有显著差异(P<0.01),红细胞免疫复合物花环率与对照组相比,两组均显著增高(P<0.01),CR1免疫黏附促进因子活性与对照组相比,组1组2均显著降低(P<0.01),CR1免疫黏附抑制因子活性与对照组相比,两组均增高(P<0.01)。提示复发性阿弗他溃疡患者存在红细胞免疫功能受损,多甙颗粒剂对复发性阿弗他溃疡患者的红细胞免疫功能有调节作用。  相似文献   
72.
In vitro studies can help reveal the biochemical pathways underlying the origin of volatile indicators of numerous diseases. The key objective of this study is to identify the potential biomarkers of gastric cancer. For this purpose, the volatilomic signatures of two human gastric cancer cell lines, AGS (human gastric adenocarcinoma) and SNU-1 (human gastric carcinoma), and one normal gastric mucosa cell line (GES-1) were investigated. More specifically, gas chromatography mass spectrometry has been applied to pinpoint changes in cell metabolism triggered by cancer. In total, ten volatiles were found to be metabolized, and thirty-five were produced by cells under study. The volatiles consumed were mainly six aldehydes and two heterocyclics, whereas the volatiles released embraced twelve ketones, eight alcohols, six hydrocarbons, three esters, three ethers, and three aromatic compounds. The SNU-1 cell line was found to have significantly altered metabolism in comparison to normal GES-1 cells. This was manifested by the decreased production of alcohols and ketones and the upregulated emission of esters. The AGS cells exhibited the increased production of methyl ketones containing an odd number of carbons, namely 2-tridecanone, 2-pentadecanone, and 2-heptadecanone. This study provides evidence that the cancer state modifies the volatilome of human cells.  相似文献   
73.
HIF means hypoxia-inducible factor gene family, and it could regulate various biological processes, including tumor development. In 2021, the FDA approved the new drug Welireg for targeting HIF-2a, and it is mainly used to treat von Hippel-Lindau syndrome, which demonstrated its good prospects in tumor therapy. As the fourth deadliest cancer worldwide, gastric cancer endangers the health of people all across the world. Currently, there are various treatment methods for patients with gastric cancer, but the five-year survival rate of patients with advanced gastric cancer is still not high. Therefore, here we reviewed the regulatory role and target role of HIF in gastric cancer, and provided some references for the treatment of gastric cancer.  相似文献   
74.
采用离子交换高效液相色谱-氢化物发生-原子荧光光度法(HPLC—HG—AFS)测定雄黄在水、人工胃液、人工肠液中可溶性As(Ⅲ)的含量.结果发现雄黄在人工胃液及人工肠液中As(Ⅱ)的溶出量均高于在水中As(Ⅲ)的溶出量,从而增加了雄黄对机体的毒性.还研究了色谱分离条件如HCl和KBH4的浓度和流速等,并对检测器参数等实验条件进行了优化,使不同价态无机砷在10min内达到良好的基线分离.  相似文献   
75.
The kinetics of the adsorption of human gastric lipase (HGL) and human pancreatic lipase (HPL) were studied by recording the changes in the surface pressure with time in the absence and presence of an egg phosphatidylcholine (PC) monomolecular film spread at the air/water interface. In the presence of PC film, the tensioactivtty of HGL increased considerably compared with its behaviour at the air/water interface, whereas HPL exhibited a comparable degree of tensioactivity whether or not a phospholipid monolayer was present at the interface. This difference in surface behaviour is consistent with the higher penetration capacity attributed to HGL. Procolipase considerably increased both the initial adsorption rate and the final surface pressure reached by HPL compared with its adsorption without colipase.

The kinetics of the hydrolysis of 1,2-didecanoyl-sn-glycerol (dicaprin) monolayers by HGL and HPL were measured using a “zero-order” trough. The large differences between the calculated characteristic adsorption times and the measured lag times indicate that the partition of the lipase molecules between the subsurface and the interface was probably limited by an energy barrier. The amplitude of this energy barrier can be partly attributed to the drastic conformational change in the enzyme, associated with the interfacial activation.

The area per dicaprin molecule (56 Å2) corresponding to the maximal activity of HPL was compared with the dimension of the hydrophobic cleft surrounding the serine (Ser 152) of the catalytic triad of HPL, as recently demonstrated by H. Van Tilbeurgh and co-workers (Nature, 359 (1992) 159; 362 (1993) 814) in their studies on the “open” and “closed” forms of the respective three-dimensional crystalline structures. The catalytic triad was not accessible to a sphere 8.4 Å in diameter, mimicking the van der Waals envelope of the dicaprin molecule, due to the steric hindrance of the side chains of aromatic and cyclic residues F 215, F 77, Y 114 and H 263. It can be concluded that the substrate molecule must also undergo some conformational changes at the contact of the enzyme to be accommodated in the active site.  相似文献   

76.
血清锌,体液及细胞免疫与复发性口腔溃疡的实验观察   总被引:2,自引:0,他引:2  
为了解缺锌是否导致体液及细胞免疫功能失调,诱发口腔溃疡的发生,采用吡啶偶氮萘酚比色法测定了血清中的锌,用免疫荧光法外周血T淋巴细胞亚群,用免疫比浊法测定血清免疫球蛋白。通过各50例实验观察表明,口腔溃疡组血清锌偏低,且T淋巴细胞亚群比值失调,与健康对照组比较,有显著性差异。  相似文献   
77.
An analytical method was developed for determination of valsartan in commercial drug and sewage sludge samples by HPLC–UV using a single wavelength (250 nm). The effect of different environmental storage conditions on the stability of valsartan was examined for a period of 85 days, after which no degradation was observed. The post oral administration stability of the valsartan was also investigated by testing valsartan under simulated gastric conditions. Results obtained showed that the structure of valsartan was conserved over 3.5-h period. The calibration plot of the study was linear over a wide concentration range with a correlation coefficient of 0.9999. The limit of detection and limit of quantitation were found to be 0.014 and 0.046 µ g mL?1, respectively. The percentage recovery of valsartan from sewage sludge was found to be 99.8%.  相似文献   
78.
目的对应用血清CEA、CA19-9联合检测方式对患有胃癌疾病的老年患者的病情实施诊断的临床价值进行研究。方法选择广丰县中医院收治的患有胃癌疾病和胃部良性疾病的老年患者各60例,再抽取同期接受健康体检的健康老年人资料60例,分别将其定义为研究1组、研究2组、对照组。采用化学发光法对三组研究对象的血清CEA、CA19-9水平进行测定,对比分析检测结果和两项指标的阳性率。结果研究1组的血清CEA、CA19-9水平明显高于对照组和研究2组,组间数据比较差异显著(P0.05);研究2组的血清CEA、CA19-9水平明显高于对照组,组间数据比较差异显著(P0.05)。研究1组的CEA、CA19-9水平检测阳性人数明显多于对照组和研究2组,组间数据比较差异显著(P0.05);研究2组的CEA、CA19-9水平检测阳性人数明显多于对照组,组间数据比较差异显著(P0.05)。结论患有胃癌疾病的老年患者的血清CEA、CA19-9水平会异常升高,临床上可以将其作为老年胃癌疾病诊断的重要依据。  相似文献   
79.
80.
The 6‐O‐ sulfate ester of morphine (M6S) has previously been shown to be an analgesic with greater potency and fewer side effects than morphine. However, being a sulfate ester derivative of morphine, the question exists as to whether this compound is stable in biological fluids and tissues with regard to pH‐ and esterase‐mediated degradation. To date, no studies have focused on the stability profile of M6S across the physiologically relevant pH range of 1.2–7.4. In addition, the stability of M6S is not known in rat plasma and rat brain homogenate, or in simulated rat gastric and intestinal fluids. This study determines the stability profile of M6S (utilized as the sodium salt) and demonstrates that M6S is highly stable and resilient to either enzymatic‐ or pH‐dependent hydrolysis in vitro .  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