全文获取类型
收费全文 | 254742篇 |
免费 | 22724篇 |
国内免费 | 16078篇 |
专业分类
电工技术 | 16337篇 |
技术理论 | 8篇 |
综合类 | 18045篇 |
化学工业 | 60534篇 |
金属工艺 | 17998篇 |
机械仪表 | 13074篇 |
建筑科学 | 12418篇 |
矿业工程 | 5201篇 |
能源动力 | 9983篇 |
轻工业 | 17500篇 |
水利工程 | 2828篇 |
石油天然气 | 13307篇 |
武器工业 | 1982篇 |
无线电 | 28992篇 |
一般工业技术 | 29342篇 |
冶金工业 | 10714篇 |
原子能技术 | 3297篇 |
自动化技术 | 31984篇 |
出版年
2024年 | 899篇 |
2023年 | 3827篇 |
2022年 | 7099篇 |
2021年 | 8051篇 |
2020年 | 7164篇 |
2019年 | 6724篇 |
2018年 | 6313篇 |
2017年 | 7835篇 |
2016年 | 8734篇 |
2015年 | 8937篇 |
2014年 | 12812篇 |
2013年 | 14569篇 |
2012年 | 16554篇 |
2011年 | 19663篇 |
2010年 | 15302篇 |
2009年 | 16974篇 |
2008年 | 15492篇 |
2007年 | 17848篇 |
2006年 | 16597篇 |
2005年 | 13433篇 |
2004年 | 11403篇 |
2003年 | 10410篇 |
2002年 | 8469篇 |
2001年 | 6882篇 |
2000年 | 6042篇 |
1999年 | 4764篇 |
1998年 | 3522篇 |
1997年 | 2848篇 |
1996年 | 2579篇 |
1995年 | 2358篇 |
1994年 | 2125篇 |
1993年 | 1670篇 |
1992年 | 1315篇 |
1991年 | 934篇 |
1990年 | 707篇 |
1989年 | 601篇 |
1988年 | 394篇 |
1987年 | 273篇 |
1986年 | 257篇 |
1985年 | 206篇 |
1984年 | 171篇 |
1983年 | 113篇 |
1982年 | 119篇 |
1981年 | 121篇 |
1980年 | 91篇 |
1979年 | 61篇 |
1978年 | 41篇 |
1977年 | 37篇 |
1976年 | 40篇 |
1975年 | 38篇 |
排序方式: 共有10000条查询结果,搜索用时 16 毫秒
51.
52.
The slight-alkalization of generator internal cooling water (GICW) is widely used to inhibit the corrosion of hollow copper conductor and thereby ensure the safe operation of the generator. CO2 inleakage is increasingly identified as a potential security risk for GICW system. In this paper, the influence of CO2 inleakage on the slight-alkalization of GICW was theoretically discussed. Based on the equilibriums of the CO2-NaOH-H2O system, CO2 inleakage saturation was derived to quantify the amount of the dissolved CO2 in GICW. This parameter can be directly calculated with the measured conductivity and the [Na+] of GICW. The influence of CO2 inleakage on the slight-alkalization conditioning of GICW and the measurement of its water quality parameters were then analyzed. The more severe the inleakage, the narrower the water quality operation ranges of GICW, resulting in the more difficult the slight-alkalization conditioning of GICW. The temperature calibrations of the conductivity and the pH value of GICW show non-linear correlations with the amount of CO2 inleakage and the NaOH dosage. This study provides insights into the influence of CO2 inleakage on the slight-alkalization of GICW, which can serve as the theoretical basis for the actual slight-alkalization when CO2 inleakage occurs. 相似文献
53.
54.
Cheng-Chin Huang Ching-Yao Yang Chin-Chuan Su Kai-Min Fang Cheng-Chieh Yen Ching-Ting Lin Jui-Min Liu Kuan-I Lee Ya-Wen Chen Shing-Hwa Liu Chun-Fa Huang 《International journal of molecular sciences》2021,22(9)
4-methyl-2,4-bis(4-hydroxyphenyl)pent-1-ene (MBP), a major active metabolite of bisphenol A (BPA), is generated in the mammalian liver. Some studies have suggested that MBP exerts greater toxicity than BPA. However, the mechanism underlying MBP-induced pancreatic β-cell cytotoxicity remains largely unclear. This study demonstrated the cytotoxicity of MBP in pancreatic β-cells and elucidated the cellular mechanism involved in MBP-induced β-cell death. Our results showed that MBP exposure significantly reduced cell viability, caused insulin secretion dysfunction, and induced apoptotic events including increased caspase-3 activity and the expression of active forms of caspase-3/-7/-9 and PARP protein. In addition, MBP triggered endoplasmic reticulum (ER) stress, as indicated by the upregulation of GRP 78, CHOP, and cleaved caspase-12 proteins. Pretreatment with 4-phenylbutyric acid (4-PBA; a pharmacological inhibitor of ER stress) markedly reversed MBP-induced ER stress and apoptosis-related signals. Furthermore, exposure to MBP significantly induced the protein phosphorylation of JNK and AMP-activated protein kinase (AMPK)α. Pretreatment of β-cells with pharmacological inhibitors for JNK (SP600125) and AMPK (compound C), respectively, effectively abrogated the MBP-induced apoptosis-related signals. Both JNK and AMPK inhibitors also suppressed the MBP-induced activation of JNK and AMPKα and of each other. In conclusion, these findings suggest that MBP exposure exerts cytotoxicity on β-cells via the interdependent activation of JNK and AMPKα, which regulates the downstream apoptotic signaling pathway. 相似文献
55.
56.
Friederike Freiin von Hvel Ekaterini Kefalakes Claudia Grothe 《International journal of molecular sciences》2021,22(1)
Fibroblast growth factor 2 (FGF-2), ubiquitously expressed in humans and mice, is functionally involved in cell growth, migration and maturation in vitro and in vivo. Based on the same mRNA, an 18-kilo Dalton (kDa) FGF-2 isoform named FGF-2 low molecular weight (FGF-2LMW) isoform is translated in humans and rodents. Additionally, two larger isoforms weighing 21 and 22 kDa also exist, summarized as the FGF-2 high molecular weight (FGF-2HMW) isoform. Meanwhile, the human FGF-2HMW comprises a 22, 23, 24 and 34 kDa protein. Independent studies verified a specific intracellular localization, mode of action and tissue-specific spatiotemporal expression of the FGF-2 isoforms, increasing the complexity of their physiological and pathophysiological roles. In order to analyze their spectrum of effects, FGF-2LMW knock out (ko) and FGF-2HMWko mice have been generated, as well as mice specifically overexpressing either FGF-2LMW or FGF-2HMW. So far, the development and functionality of the cardiovascular system, bone formation and regeneration as well as their impact on the central nervous system including disease models of neurodegeneration, have been examined. This review provides a summary of the studies characterizing the in vivo effects modulated by the FGF-2 isoforms and, thus, offers a comprehensive overview of its actions in the aforementioned organ systems. 相似文献
57.
58.
The Fe/C/SiCN composite ceramics were synthesized by polymer-derived method to obtain the integration of structure and functions. The electromagnetic waves (EMW) absorption properties at X and Ku bands were investigated. The addition of nano-sized Fe particles improved the magnetic loss and impedance matching, and the carbon nanotubes generated by the iron in-situ catalysis increased the internal relaxation polarization and interfacial polarization, which together improved the EMW absorption properties significantly. In particular, the Fe/C/SiCN-9 showed the optimum reflection loss (RL) of ?31.06 dB at 10.03 GHz with an effective absorption bandwidth (EAB, RL < ?10 dB) of 3.03 GHz at 2.51 mm, indicating the excellent EMW absorption properties of Fe/C/SiCN composite ceramics. 相似文献
59.
The bacterial formulations, spinosad and spinetoram, were evaluated for their efficacy in suppressing development and mating success in Cadra cautella (Walk.) (Lepidoptera: Pyralidae), the almond moth. A dilution series of spinosad and spinetoram was sprayed on rice flour. Rice flour samples sprayed with water served as the control. Late instar C. cautella larvae were introduced onto spinosad-, spinetoram-, or water-treated rice flour. The first experiment tested the effects of spinosad and spinetoram on larval mortality, as well as emergence of adults and progeny at different insecticide concentrations. In the second experiment, the mating success of C. cautella adults that had emerged from larvae exposed to spinosad was tested inside a cubicle. Both spinosad and spinetoram increased larval mortality, whereas both compounds reduced adult emergence and progeny production. Natural mating was reduced in the presence of the synthetic sex pheromone (Z,E)-9,12-tetradecadienyl acetate. However, exposure of C. cautella larvae to spinosad did not alter mating in adult progeny. Spinosad was more effective than spinetoram at suppressing C. cautella development. The study concludes that both spinosad and spinetoram suppress the development of immatures of C. cautella to the adult stage as well as mating. Thus, the both compounds can be used to protect stored grains from infestation by C. cautella. 相似文献
60.