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   2408篇
  免费   172篇
  国内免费   1篇
电工技术   13篇
综合类   3篇
化学工业   980篇
金属工艺   36篇
机械仪表   45篇
建筑科学   66篇
矿业工程   6篇
能源动力   66篇
轻工业   474篇
水利工程   22篇
石油天然气   5篇
无线电   125篇
一般工业技术   329篇
冶金工业   128篇
原子能技术   7篇
自动化技术   276篇
  2024年   4篇
  2023年   48篇
  2022年   188篇
  2021年   230篇
  2020年   75篇
  2019年   102篇
  2018年   84篇
  2017年   82篇
  2016年   105篇
  2015年   92篇
  2014年   96篇
  2013年   170篇
  2012年   146篇
  2011年   186篇
  2010年   164篇
  2009年   120篇
  2008年   105篇
  2007年   90篇
  2006年   78篇
  2005年   57篇
  2004年   39篇
  2003年   43篇
  2002年   42篇
  2001年   22篇
  2000年   12篇
  1999年   23篇
  1998年   33篇
  1997年   18篇
  1996年   17篇
  1995年   11篇
  1994年   9篇
  1993年   11篇
  1992年   10篇
  1991年   6篇
  1990年   4篇
  1989年   5篇
  1988年   2篇
  1987年   8篇
  1986年   5篇
  1985年   7篇
  1984年   2篇
  1983年   3篇
  1982年   5篇
  1981年   6篇
  1980年   3篇
  1978年   5篇
  1976年   1篇
  1973年   1篇
  1970年   2篇
  1969年   2篇
排序方式: 共有2581条查询结果,搜索用时 15 毫秒
41.
The nature and extent of the modification of starch in quinoa, caused by various processes like cooking and autoclaving of the seeds, drum drying of the flour and extrusion of the grits was investigated by measuring the physico-chemical properties - the water absorption, water solubility, swelling power, viscosity and degree of gelatinisation - of the processed samples. Autoclaved samples showed the lowest degree of gelatinisation (32.5% by DSC) of the starch, while the degree of gelatinisation of the precooked/drum dried samples was found to be 97.4% by DSC method. Higher polymer degradation was observed in cooked samples than in autoclaved samples as seen in the gel chromatographic separation. The water solubility in cooked samples (5.44 to 15.58) and in autoclaved samples (7.02 to 9.64) increased with the process time. In the extrusion process, the moisture content as well as the compression ratio was found to affect the degree of starch modification significantly (p <0.01).  相似文献   
42.
Layered double hydroxide (LDH) containing different metal constituents (Zn, Co, and Ni) was intercalated with different organic anions and has been used as fillers in low-density polyethylene (LDPE), and its thermal and flammability behavior was evaluated. The best thermal stability (∆T0.5 = 21 °C) was obtained with the LDPE-Ni/Al-dodecyl sulfate (4 wt %) nanocomposite. Addition of hydrophobic LDHs systematically decreases the enthalpy of melting and crystallization compared to the neat polymer. In LDPE-Co/Al-dodecyl sulfate (2 wt %) nanocomposite, the melting and crystallization enthalpies declined by about 45 J/g, indicating a good interaction of the filler with the polymer matrix. A reduction of 20% of the flammability for the LDPE-Ni/Al-stearate (4 wt %) nanocomposite was obtained. On the other hand, Zn–Co LDH as filler in LDPE nanocomposite did not affect effectively the same property. In an innovative study, results indicate that different metal constituents and interlayer anion of LDH as filler can change thermal and flammability properties of the polymer nanocomposite. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48737.  相似文献   
43.
44.
Fetal stress is known to increase susceptibility to cardiometabolic diseases and hypertension in adult age in a process known as fetal programming. This study investigated the relationship between vascular RAS, oxidative damage and remodeling in fetal programming. Six-month old Sprague-Dawley offspring from mothers that were fed ad libitum (CONTROL) or with 50% intake during the second half of gestation (maternal undernutrition, MUN) were used. qPCR or immunohistochemistry were used to obtain the expression of receptors and enzymes. Plasma levels of carbonyls were measured by spectrophotometry. In mesenteric arteries from MUN rats we detected an upregulation of ACE, ACE2, AT1 receptors and NADPH oxidase, and lower expression of AT2, Mas and MrgD receptors compared to CONTROL. Systolic and diastolic blood pressure and plasma levels of carbonyls were higher in MUN than in CONTROL. Vascular morphology evidenced an increased media/lumen ratio and adventitia/lumen ratio, and more connective tissue in MUN compared to CONTROL. In conclusion, fetal undernutrition indices RAS alterations and oxidative damage which may contribute to the remodeling of mesenteric arteries, and increase the risk of adverse cardiovascular events and hypertension.  相似文献   
45.
Spray parameters play an important role on the microstructure and properties of plasma-sprayed coatings. Parameters such as spray distance, plasma gas flow and current, raster speed, and spray angle all can be varied. In this paper, an integrated study to investigate the effects and influences of spray angle on properties of yttria-stabilized zirconia coatings was carried out with spray angles of 60°, 75°, and 90° (to the substrate surface). In situ coating property sensor based on beam curvature measurements was used to measure the evolving stress and elastic moduli of the resultant coatings and combined with other characterization tools for thermo-physical property and microstructure analysis, such as laser flash and scanning electron microscopy. The results indicate that the coating with 60° spray angle had the lowest thermal conductivity and more compliant structure. This study seeks to understand the mechanism for this effect and will provide important insight into parametric sensitivities on complex spray parts.  相似文献   
46.
Thiols (sulfhydryl groups) are effective antioxidants that can preserve the correct structure of proteins, and can protect cells and tissues from damage induced by oxidative stress. Abnormal levels of thiols have been measured in the blood of patients with moderate-to-severe chronic kidney disease (CKD) compared to healthy subjects, as well as in end-stage renal disease (ESRD) patients on haemodialysis or peritoneal dialysis. The levels of protein thiols (a measure of the endogenous antioxidant capacity inversely related to protein oxidation) and S-thiolated proteins (mixed disulphides of protein thiols and low molecular mass thiols), and the protein thiolation index (the molar ratio of the S-thiolated proteins to free protein thiols in plasma) have been investigated in the plasma or red blood cells of CKD and ESRD patients as possible biomarkers of oxidative stress. This type of minimally invasive analysis provides valuable information on the redox status of the less-easily accessible tissues and organs, and of the whole organism. This review provides an overview of reversible modifications in protein thiols in the setting of CKD and renal replacement therapy. The evidence suggests that protein thiols, S-thiolated proteins, and the protein thiolation index are promising biomarkers of reversible oxidative stress that could be included in the routine monitoring of CKD and ESRD patients.  相似文献   
47.
In the clinical management of solid tumors, the possibility to successfully couple the regeneration of injured tissues with the elimination of residual tumor cells left after surgery could open doors to new therapeutic strategies. In this work, we present a composite hydrogel–electrospun nanofiber scaffold, showing a modular architecture for the delivery of two pharmaceutics with distinct release profiles, that is potentially suitable for local therapy and post-surgical treatment of solid soft tumors. The composite was obtained by coupling gelatin hydrogels to poly(ethylene oxide)/poly(butylene terephthalate) block copolymer nanofibers. Results of the scaffolds’ characterization, together with the analysis of gelatin and drug release kinetics, displayed the possibility to modulate the device architecture to control the release kinetics of the drugs, also providing evidence of their activity. In vitro analyses were also performed using a human epithelioid sarcoma cell line. Furthermore, publicly available expression datasets were interrogated. Confocal imaging showcased the nontoxicity of these devices in vitro. ELISA assays confirmed a modulation of IL-10 inflammation-related cytokine supporting the role of this device in tissue repair. In silico analysis confirmed the role of IL-10 in solid tumors including 262 patients affected by sarcoma as a negative prognostic marker for overall survival. In conclusion, the developed modular composite device may provide a key-enabling technology for the treatment of soft tissue sarcoma.  相似文献   
48.
In addition to CD4+ T lymphocytes, myeloid cells and, particularly, differentiated macrophages are targets of human immunodeficiency virus type-1 (HIV-1) infection via the interaction of gp120Env with CD4 and CCR5 or CXCR4. Both T cells and macrophages support virus replication, although with substantial differences. In contrast to activated CD4+ T lymphocytes, HIV-1 replication in macrophages occurs in nondividing cells and it is characterized by the virtual absence of cytopathicity both in vitro and in vivo. These general features should be considered in evaluating the role of cell-associated restriction factors aiming at preventing or curtailing virus replication in macrophages and T cells, particularly in the context of designing strategies to tackle the viral reservoir in infected individuals receiving combination antiretroviral therapy. In this regard, we will here also discuss a model of reversible HIV-1 latency in primary human macrophages and the role of host factors determining the restriction or reactivation of virus replication in these cells.  相似文献   
49.
50.
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