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   207篇
  免费   34篇
  国内免费   21篇
化学   124篇
晶体学   1篇
力学   6篇
综合类   3篇
数学   39篇
物理学   89篇
  2024年   1篇
  2023年   7篇
  2022年   9篇
  2021年   14篇
  2020年   13篇
  2019年   13篇
  2018年   12篇
  2017年   3篇
  2016年   6篇
  2015年   3篇
  2014年   22篇
  2013年   13篇
  2012年   23篇
  2011年   18篇
  2010年   6篇
  2009年   10篇
  2008年   9篇
  2007年   6篇
  2006年   7篇
  2005年   4篇
  2004年   6篇
  2003年   4篇
  2002年   4篇
  2001年   5篇
  2000年   1篇
  1999年   6篇
  1998年   5篇
  1997年   8篇
  1996年   3篇
  1995年   3篇
  1994年   1篇
  1993年   3篇
  1992年   1篇
  1991年   2篇
  1990年   2篇
  1989年   3篇
  1988年   4篇
  1987年   1篇
  1983年   1篇
排序方式: 共有262条查询结果,搜索用时 31 毫秒
1.
The main mission the HL-2A tokamak is of the experiments on to explore the divertor physics and to investigate the plasma confinement, transport and instabilities with high power auxiliary heating and advanced fuelling, it is necessary to develop more new diagnostics and increase the spatial and temporal resolutions of the measurements for exist system. Up to now, about 30 diagnostic systems have been moved from HL-1M to HL-2A tokamak. Other 10 diagnostic systems are being designed and installed on the device. In developed in last 2 years, will be presented.  相似文献   
2.
Dexmedetomidine (DEX) is an anesthetic that is widely used in the clinic, and it has been reported to exhibit paradoxical effects in the progression of multiple solid tumors. In this study, we sought to explore the mechanism by which DEX regulates hepatocellular carcinoma (HCC) progression underlying liver fibrosis. We determined the effects of DEX on tumor progression in an orthotopic HCC mouse model of fibrotic liver. A coculture system and a subcutaneous xenograft model involving coimplantation of mouse hepatoma cells (H22) and primary activated hepatic stellate cells (aHSCs) were used to study the effects of DEX on HCC progression. We found that in the preclinical mouse model of liver fibrosis, DEX treatment significantly shortened median survival time and promoted tumor growth, intrahepatic metastasis and pulmonary metastasis. The DEX receptor (ADRA2A) was mainly expressed in aHSCs but was barely detected in HCC cells. DEX dramatically reinforced HCC malignant behaviors in the presence of aHSCs in both the coculture system and the coimplantation mouse model, but DEX alone exerted no significant effects on the malignancy of HCC. Mechanistically, DEX induced IL-6 secretion from aHSCs and promoted HCC progression via STAT3 activation. Our findings provide evidence that the clinical application of DEX may cause undesirable side effects in HCC patients with liver fibrosis.Subject terms: Cancer microenvironment, Cell growth  相似文献   
3.
化工工人体内微量元素积累与健康的关系   总被引:1,自引:0,他引:1  
论述了化工作业工人长期接触有害元素会引起体内有害元素积蓄,微量元素平衡失调,产生潜在的职业危害,建议定期对临床尚未发现中毒现象的作业工人进行体内微量元素情况监控,以预防职业中毒。并提出采用适当补充某些必需元素的方法,可预防这种危害。  相似文献   
4.
董文玉 《分析化学》1997,25(11):1285-1289
  相似文献   
5.
从微量元素的角度,论述了食物间的相互作用,主要有:转化作用、协同作用和抗作用。  相似文献   
6.
A new type of bismaleimide resin (EPBMI), containing epoxy unit and phosphorus in the main chain, was synthesized. The structure of the new resin was confirmed by infrared spectroscopy (IR), 1H NMR and 13C NMR spectroscopies. In addition, the compositions of the new synthesized bismaleimide with two reactants, 4,4′-diaminodiphenylsulfone (DDS) and 4,4′-diaminodiphenylether (DDE), was used to compare its reactivity and thermal properties with conventional bismaleimide (EBMI). Reactivity was measured by differential scanning calorimetry. Thermogravimetric analysis revealed that the polymers, obtained through the reactions between bismaleimides and diamine agents, also demonstrated excellent thermal properties and high char yield.  相似文献   
7.
Tm3+ and In3+ co-doped LaAlO3 phosphors were prepared by a Pechini sol–gel method and characterized by X-ray diffraction, scanning electron microscope, and cathodoluminescence spectrum. The phosphor is composed of slightly aggregated particles with approximately spherical shape and a narrow size range of 1.0–1.5 μm. Under voltage electron beam excitation, the phosphor shows the characteristic emissions of Tm3+. All the color purity, radiant efficiency, luminous efficiency, and stability of the optimum LaAlO3:0.01Tm3+, 0.04In3+ phosphor are superior to these of commercial ZnS:Ag,Cl phosphor. These tests suggest that it could be a potential candidate as a blue phosphor for field emission displays.  相似文献   
8.
The diffusion of 125I? in compacted Gaomiaozi (GMZ) bentonite was investigated by capillary in-diffusion method. Apparent and effective diffusion coefficients and accessible porosity of iodide in GMZ bentonite were obtained, and the effect of ionic strength on diffusion parameters was studied. The apparent diffusion coefficients of iodide in compacted GMZ bentonite are in the range of 1.0–6.0 × 10?10 m2 s?1 under the conditions of dry bulk density 1,500 kg m?3 and temperature 298 K, and increase with increasing ionic strength. This effect was explained through the analysis of microscopic structure of compacted bentonite. The iodide can only diffuse in unbound interparticle pore solution of compacted bentonite. The apparent diffusion coefficient is a function of accessible porosity which is decided by the thickness of diffusion double layer, and the thickness is in turn controlled by ionic strength.  相似文献   
9.
Six parts of lotus (seeds, leaves, plumule, stamens, receptacles and rhizome nodes) are herbal medicines that are listed in the Chinese Pharmacopoeia. Their indications and functions have been confirmed by a long history of clinical practice. To fully understand the material basis of clinical applications, UPLC-QToF-MS combined with the UNIFI platform and multivariate statistical analysis was used in this study. As a result, a total of 171 compounds were detected and characterized from the six parts, and 23 robust biomarkers were discovered. The method can be used as a standard protocol for the direct identification and prediction of the six parts of lotus. Meanwhile, these discoveries are valuable for improving the quality control method of herbal medicines. Most importantly, this was the first time that alkaloids were detected in the stamen, and terpenoids were detected in the cored seed. The stamen is a noteworthy part because it contains the greatest diversity of flavonoids and terpenoids, but research on the stamen is rather limited.  相似文献   
10.
Stromal cell-derived factor 1α (SDF-1α) or CXCL12 is a small pro-inflammatory chemoattractant cytokine and a substrate of dipeptidyl peptidase IV (DPP-IV). Proteolytic cleavage by DPP-IV inactivates SDF-1α and attenuates its interaction with CXCR4, its cell surface receptor. To enable investigation of suppression of such inactivation with pharmacologic inhibition of DPP-IV, we developed quantitative mass spectrometric methods that differentiate intact SDF-1α from its inactive form. Using top-down strategy in quantification, we demonstrated the unique advantage of keeping SDF-1α’s two disulfide bridges intact in the analysis. To achieve the optimal sensitivity required for quantification of intact and truncated SDF-1α at endogenous levels in blood, we coupled nano-flow tandem mass spectrometry with antibody-based affinity enrichment. The assay has a quantitative range of 20 pmol/L to 20 nmol/L in human plasma as well as in rhesus monkey plasma. With only slight modification, the same assay can be used to quantify SDF-1α in mice. Using two in vivo animal studies as examples, we demonstrated that it was critical to differentiate intact SDF-1α from its truncated form in the analysis of biomarkers for pharmacologic inhibition of DPP-IV activity. These novel methods enable translational research on suppression of SDF-1 inactivation with DPP-IV inhibition and can be applied to relevant clinical samples in the future to yield new insights on change of SDF-1α levels in disease settings and in response to therapeutic interventions.
Figure
?  相似文献   
1 [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] 下一页 » 末  页»
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