全文获取类型
收费全文 | 2934篇 |
免费 | 201篇 |
国内免费 | 11篇 |
专业分类
电工技术 | 63篇 |
综合类 | 3篇 |
化学工业 | 610篇 |
金属工艺 | 102篇 |
机械仪表 | 209篇 |
建筑科学 | 62篇 |
矿业工程 | 3篇 |
能源动力 | 131篇 |
轻工业 | 223篇 |
水利工程 | 10篇 |
石油天然气 | 2篇 |
无线电 | 562篇 |
一般工业技术 | 594篇 |
冶金工业 | 221篇 |
原子能技术 | 34篇 |
自动化技术 | 317篇 |
出版年
2024年 | 4篇 |
2023年 | 40篇 |
2022年 | 44篇 |
2021年 | 83篇 |
2020年 | 77篇 |
2019年 | 76篇 |
2018年 | 97篇 |
2017年 | 100篇 |
2016年 | 103篇 |
2015年 | 90篇 |
2014年 | 138篇 |
2013年 | 147篇 |
2012年 | 188篇 |
2011年 | 219篇 |
2010年 | 181篇 |
2009年 | 192篇 |
2008年 | 144篇 |
2007年 | 150篇 |
2006年 | 116篇 |
2005年 | 113篇 |
2004年 | 97篇 |
2003年 | 83篇 |
2002年 | 80篇 |
2001年 | 65篇 |
2000年 | 66篇 |
1999年 | 57篇 |
1998年 | 99篇 |
1997年 | 78篇 |
1996年 | 34篇 |
1995年 | 36篇 |
1994年 | 16篇 |
1993年 | 24篇 |
1992年 | 18篇 |
1991年 | 17篇 |
1990年 | 13篇 |
1989年 | 14篇 |
1988年 | 11篇 |
1987年 | 5篇 |
1986年 | 5篇 |
1985年 | 7篇 |
1984年 | 1篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1975年 | 3篇 |
1973年 | 1篇 |
排序方式: 共有3146条查询结果,搜索用时 15 毫秒
141.
This study proposes a systematic approach for retrofitting a steam-injection gas turbine (SIGT) with a multi-effect thermal vapor compression (METVC) desalination system. The retrofitted unit's product cost of the fresh water (RUPC) was used as a performance criterion, which comprises the thermodynamic, economic, and environmental attributes when calculating the total annual cost of the SIGT–METVC system. For the feasibility study of retrofitting the SIGT plant with the METVC desalination system, the effects of two key parameters were analyzed using response surface methodology (RSM) based on a central composite design (CCD): the steam air ratio (SR) and the temperature difference between the effects of the METVC system (?TMETVC) on the fresh water production (Qfreshwater) and the net power generation (Wnet) of the SIGT–METVC system. Multi-objective optimization (MOO) which minimizes the modified total annual cost (MTAC) and maximizes the fresh water flow rate was performed to optimize the RUPC of the SIGT–METVC system. The best Pareto optimal solution showed that the SIGT–METVC system with five effects is the best one among the systems with 4–6 effects. This system under optimal operating conditions can save 21.07% and 9.54% of the RUPC, compared to the systems with four and six effects, respectively. 相似文献
142.
Ho-Sung Yoon Chul-Joo Kim Kyeong Woo Chung Su-Jeong Lee A-Ram Joe Yang-Ho Shin Se-Il Lee Seung-Joon Yoo Jin-Geol Kim 《Korean Journal of Chemical Engineering》2014,31(4):706-711
The leaching kinetics of neodymium in NdFeB permanent magnet powder was analyzed for the purpose of recovery of neodymium in sulfuric acid (H2SO4) from E-scrap (electric scrap) of NdFeB permanent magnet powder treated by oxidation roasting to form a reactant. The reaction was conducted with H2SO4 concentrations ranging from 2.5 to 3.5M, a pulp density of 110.8 g/L, an agitation speed of 750 rpm, and a temperature range of 30 to 70 °C. After 4 h of leaching, the neodymium content in the E-scrap powders was completely converted into a neodymium sulfate (Nd2(SO4)3) solution phase in H2SO4 in the condition of 70 °C and 3.0M H2SO4. Based on a shrinking core model with sphere shape, the leaching mechanism of neodymium was determined by the rate-determining step of the ash layer diffusion. Generally, the solubility of pure rare earth elements in H2SO4 is decreased with an increase in leaching temperatures. However, the leaching rate of the neodymium in E-scrap powders increased with the leaching temperatures in this study because the ash layer included in the E-scrap powder provided resistance against the leaching. Using the Arrhenius expression, the apparent activation energy values were determined to be 2.26 kJmol?1 in 2.5M H2SO4 and 2.77 kJmol?1 in 3.0 M H2SO4. 相似文献
143.
The objectives of this study were twofold. The first was to investigate the compressive and flexural behaviors of small‐sized concrete specimens strengthened with sprayed fiber reinforced polymer (SFRP), considering various fiber lengths, fiber volumes, and concrete strengths. The second was to evaluate the strengthening effects of SFRP on the flexural behaviors of large‐sized reinforced concrete beams. U‐shaped strips and shear keys were applied to the test specimens to improve the interfacial bond resistance between the concrete surface and SFRP. POLYM. COMPOS., 36:722–730, 2015. © 2014 Society of Plastics Engineers 相似文献
144.
Sung-Joon Lee Sang-Ho Yoo Myo-Jung Kim Jung-Wan Kim Ho-Moon Seok Kwan-Hwa Park 《Starch - St?rke》1995,47(4):127-134
A branched oligosaccharides (BOS) mixture was produced from liquefied starch solution using a maltogenic amylase of Bacillus licheniformis (BLMA). The BOS mixture was produced by both α-1,4-bond hydrolyzing and α-1,6-transglycosylation activities of BLMA, and it contained 58.3% of various branched oligosaccharides. Small branched oligosaccharides such as isomaltose, isopanose, and panose were identified in the mixture by various analyses including high performance ion-chromatography (HPIC). Major branched DP4 and DP5 molecules in the mixture were determined as 62-O-α-maltosylmaltose, 63-O-α-maltosyl-maltotriose and 62-O-α-maltotriosyl-maltose, respectively. Time course study of BOS production suggested that the hydrolysis and transglycosylation reactions catalyzed by BLMA were coupled. BLMA was likely to transfer a sugar moiety hydrolyzed from a non-reducing end of maltooligosaccharide, mainly maltose, to another moiety of sugar via the formation of α-1,6-linkage. Immobilization of BLMA was attempted as an effort to achieve a continuous process for BOS production. the immobilized enzyme showed improved thermal stability and slight loss of enzyme activity was observed during repeated usage. 相似文献
145.
ABSTRACT Governing the rate of heat transport by condenser tubes in the passive containment cooling system (PCCS), the steam condensation over a vertical cylinder in the presence of air was investigated experimentally. The main objective of this study was to explore if the condensation heat transfer coefficient relies on the tube dimension, which has been a variable missed in most condensation models or has been embraced without experimental demonstration under phase change environments. The mean heat transfer coefficient was measured in the condensation test facility named JERICHO (JNU Experimental Rig for Investigation of Condensation Heat transfer On tube). The outer diameter of the condenser tube used in this study was set to 21.5 mm. The measured heat transfer coefficients were compared to those obtained from the 40-mm-O.D. tube, and a multiplier to correct the variation of the heat transfer coefficient with the tube diameter was proposed for its application to Lee correlation. The proposed correlation was further validated against another set of experimental data obtained from a separate test facility housing the 31.8-mm-O.D. tube. 相似文献
146.
Diaaidden Alwadi Quentin Felty Deodutta Roy Changwon Yoo Alok Deoraj 《International journal of molecular sciences》2022,23(7)
Prostate cancer (PCa) is one of the leading malignant tumors in US men. The lack of understanding of the molecular pathology on the risk of food supply chain exposures of environmental phenol (EP) and paraben (PB) chemicals limits the prevention, diagnosis, and treatment options. This research aims to utilize a risk assessment approach to demonstrate the association of EP and PB exposures detected in the urine samples along with PCa in US men (NHANES data 2005–2015). Further, we employ integrated bioinformatics to examine how EP and PB exposure influences the molecular pathways associated with the progression of PCa. The odds ratio, multiple regression model, and Pearson coefficients were used to evaluate goodness-of-fit analyses. The results demonstrated associations of EPs, PBs, and their metabolites, qualitative and quantitative variables, with PCa. The genes responsive to EP and PB exposures were identified using the Comparative Toxicogenomic Database (CTD). DAVID.6.8, GO, and KEGG enrichment analyses were used to delineate their roles in prostate carcinogenesis. The plug-in CytoHubba and MCODE completed identification of the hub genes in Cytoscape software for their roles in the PCa prognosis. It was then validated by using the UALCAN database by evaluating the expression levels and predictive values of the identified hub genes in prostate cancer prognosis using TCGA data. We demonstrate a significant association of higher levels of EPs and PBs in the urine samples, categorical and numerical confounders, with self-reported PCa cases. The higher expression levels of the hub genes (BUB1B, TOP2A, UBE2C, RRM2, and CENPF) in the aggressive stages (Gleason score > 8) of PCa tissues indicate their potential role(s) in the carcinogenic pathways. Our results present an innovative approach to extrapolate and validate hub genes responsive to the EPs and PBs, which may contribute to the severity of the disease prognosis, especially in the older population of US men. 相似文献
147.
Seung-Won Jung Gi Hyun Park Eunjung Kim Kang Min Yoo Hea Won Kim Jin Soo Lee Min Youl Chang Kyong-Oh Shin Kyungho Park Eung Ho Choi 《International journal of molecular sciences》2022,23(7)
Stratum corneum (SC) pH regulates skin barrier functions and elevated SC pH is an important factor in various inflammatory skin diseases. Acidic topical formulas have emerged as treatments for impaired skin barriers. Sodium proton exchanger 1 (NHE1) is an important factor in SC acidification. We investigated whether topical applications containing an NHE1 activator could improve skin barrier functions. We screened plant extracts to identify NHE1 activators in vitro and found Melissa officinalis leaf extract. Rosmarinic acid, a component of Melissa officinalis leaf extract, significantly increased NHE1 mRNA expression levels and NHE1 production. Immunofluorescence staining of NHE1 in 3D-cultured skin revealed greater upregulation of NHE1 expression by NHE1 activator cream, compared to vehicle cream. Epidermal lipid analysis revealed that the ceramide level was significantly higher upon application of the NHE1 activator cream on 3D-cultured skin, compared to application of a vehicle cream. In a clinical study of 50–60-year-old adult females (n = 21), application of the NHE1 activator-containing cream significantly improved skin barrier functions by reducing skin surface pH and transepidermal water loss and increasing skin hydration, compared to patients who applied vehicle cream and those receiving no treatment. Thus, creams containing NHE1 activators, such as rosmarinic acid, could help maintain or recover skin barrier functions. 相似文献
148.
Seok Heo Geum Joo Yoo Ji Yeon Choi Hyoung Joon Park Sung-Kwan Park 《Food additives & contaminants. Part A, Chemistry, analysis, control, exposure & risk assessment》2016,33(11):1627-1636
A novel, stable, simple and specific ultra-performance liquid chromatography method with ultraviolet detection (205 nm) for the simultaneous analysis of 25 anti-hypertensive substances was developed. The method was validated according to the International Conference of Harmonisation guidelines with respect to linearity, accuracy, precision, limit of detection (LOD), limit of quantitation (LOQ) and stability. From the ultra-performance liquid chromatography results, we identified the LOD and LOQ of solid samples to be 0.20–1.00 and 0.60–3.00 μg ml?1, respectively, while those of liquid samples were 0.30–1.20 and 0.90–3.60 μg ml?1, respectively. The linearity exceeded 0.9999, and the intra- and inter-day precisions were 0.15–6.48% and 0.28–8.67%, respectively. The intra- and inter-day accuracies were 82.25–111.42% and 80.70–115.64%, respectively, and the stability was lower than 12.9% (relative standard deviation). This method was applied to the monitoring of 97 commercially available dietary supplements obtained in Korea, such as pills, soft capsules, hard capsules, liquids, powders and tablets. The proposed method is accurate, precise and of high quality, and can be used for the routine, reproducible analysis and control of 25 anti-hypertensive substances in various dietary supplements. The work presented herein may help to prevent incidents related to food adulteration and restrict the illegal food market. 相似文献
149.
Low molecular weight β-glucan stimulates doxorubicin-induced suppression of immune functions in mice
Nak-Yun Sung Eui-Baek Byun Du-Sup Song Young-Choon Yoo Jae-Kyung Kim Jong-Heum Park Beom-Seok Song Sang-Hyun Park Ju-Woon Lee Young-Beob Yu Jae-Hun Kim 《Food science and biotechnology》2012,21(3):645-651
The aim of this study was to evaluate the protective effect of low molecular weight β-glucan (LMG) against doxorubicin (DOX)-induced immune suppression of tumor-bearing mice. The tumor size and spleen cell functions such as spleen cell proliferation, cytokine production (interferon-γ and interleukin-2), and the population of CD4+ and CD8+ T cells were estimated. In the tumorbearing mice, the tumor size was significantly (p<0.05) decreased by DOX treatment. However, there was no significant difference between mice treated with high molecular weight β-glucan (HMG) and mice treated with LMG. Spleen cell proliferation and cytokine production were significantly (p<0.05) decreased in only DOX treated group, but increased in all β-glucan treated groups with DOX. Moreover, the populations of CD4+ and CD8+ T cells were also increased in the LMG-treated group. It appears that LMG effectively reduces the DOX-induced immune toxicity through activation of immune cells such as splenocytes. 相似文献
150.