全文获取类型
收费全文 | 123059篇 |
免费 | 14120篇 |
国内免费 | 9453篇 |
专业分类
电工技术 | 9998篇 |
技术理论 | 1篇 |
综合类 | 12329篇 |
化学工业 | 16687篇 |
金属工艺 | 8016篇 |
机械仪表 | 9037篇 |
建筑科学 | 9310篇 |
矿业工程 | 4761篇 |
能源动力 | 3142篇 |
轻工业 | 13625篇 |
水利工程 | 3552篇 |
石油天然气 | 4581篇 |
武器工业 | 1762篇 |
无线电 | 13502篇 |
一般工业技术 | 11370篇 |
冶金工业 | 4709篇 |
原子能技术 | 1739篇 |
自动化技术 | 18511篇 |
出版年
2024年 | 582篇 |
2023年 | 2013篇 |
2022年 | 4591篇 |
2021年 | 6098篇 |
2020年 | 4288篇 |
2019年 | 3146篇 |
2018年 | 3452篇 |
2017年 | 3850篇 |
2016年 | 3525篇 |
2015年 | 5493篇 |
2014年 | 6871篇 |
2013年 | 8228篇 |
2012年 | 10190篇 |
2011年 | 10767篇 |
2010年 | 10048篇 |
2009年 | 9647篇 |
2008年 | 9681篇 |
2007年 | 9329篇 |
2006年 | 8148篇 |
2005年 | 6600篇 |
2004年 | 4727篇 |
2003年 | 3326篇 |
2002年 | 3157篇 |
2001年 | 2744篇 |
2000年 | 2231篇 |
1999年 | 1146篇 |
1998年 | 509篇 |
1997年 | 418篇 |
1996年 | 344篇 |
1995年 | 257篇 |
1994年 | 214篇 |
1993年 | 199篇 |
1992年 | 145篇 |
1991年 | 116篇 |
1990年 | 94篇 |
1989年 | 92篇 |
1988年 | 53篇 |
1987年 | 47篇 |
1986年 | 36篇 |
1985年 | 23篇 |
1984年 | 23篇 |
1983年 | 17篇 |
1982年 | 23篇 |
1981年 | 12篇 |
1980年 | 26篇 |
1979年 | 24篇 |
1977年 | 10篇 |
1976年 | 13篇 |
1959年 | 12篇 |
1951年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Sowoon Seo Yunjeong Song Sun Mi Gu Hyun Kyu Min Jin Tae Hong Hye Jin Cha Jaesuk Yun 《International journal of molecular sciences》2020,21(23)
Background: Epilepsy is a chronic neurological disorder characterized by the recurrence of seizures. One-third of patients with epilepsy may not respond to antiseizure drugs. Purpose: We aimed to examine whether D-limonene, a cyclic monoterpene, exhibited any antiseizure activity in the pentylenetetrazole (PTZ)-induced kindling mouse model and in vitro. Methods: PTZ kindling mouse model was established by administering PTZ (30 mg/kg) intraperitoneally to mice once every 48 h. We performed immunoblot blots, immunohistochemistry (IHC), and high-performance liquid chromatography (HPLC) analysis after the behavioral study. Results: An acute injection of PTZ (60 mg/kg) induced seizure in mice, while pretreatment with D-limonene inhibited PTZ-induced seizure. Repeated administration of PTZ (30 mg/kg) increased the seizure score gradually in mice, which was reduced in D-limonene (10 mg/kg)-pretreated group. In addition, D-limonene treatment increased glutamate decarboxylase-67 (GAD-67) expression in the hippocampus. Axonal sprouting of hippocampal neurons after kindling was inhibited by D-limonene pretreatment. Moreover, D-limonene reduced the expression levels of Neuronal PAS Domain Protein 4 (Npas4)-induced by PTZ. Furthermore, the adenosine A2A antagonist and ZM241385 inhibited anticonvulsant activity and gamma-aminobutyric acid (GABA)ergic neurotransmission-induced by D-limonene. Conclusion: These results suggest that D-limonene exhibits anticonvulsant activity through modulation of adenosine A2A receptors on GABAergic neuronal function. SCH58261相似文献
52.
紫砂壶以造型为基本的载体,通过形神兼备的造型表现出深厚的文化情感,它将自然万物融汇其中,将各种不同的生命、思想和个性呈现其上,使人观壶如同与人交流,产生深刻的情感、精神共鸣,感受到内心的平静,这十分有益于舒缓当代人的精神心理压力,让人们通过泡茶品茗这种生活方式来获得暂时的悠闲,并通过对紫砂壶的把玩来感悟其中的文化内蕴,从而获得自由淡泊的心态,更好地面对生活。本文以紫砂壶“知竹”为例,浅谈其文化意境。 相似文献
53.
在制导炸弹半实物仿真试验中经常发现,同一发制导炸弹多次仿真的俯仰角差别较大,同一批次制导炸弹投弹试验的遥测俯仰角与仿真俯仰角差别也较大,但是俯仰角的收敛趋势均一致,实测脱靶量与仿真脱靶量都合格,且具有一致性。为了分析出现上述现象的原因,基于协方差分析描述函数法(CADFT),建立了制导炸弹半实物仿真系统的误差传播理论,计算了仿真姿态角和姿态角速度的误差。分析了仿真姿态角和姿态角速度的误差对仿真结果的影响。结果表明,在仿真系统各种误差中,气动力和气动力矩误差是主要误差,是引起仿真俯仰角差别的重要原因; 姿态角的动态验模方法不适用于制导炸弹仿真模型,而脱靶量的静态验模方法适用于制导炸弹仿真模型。 相似文献
54.
WENXI GAO QIANQIAN MA CHENYU TANG YUELI ZHAN YINONG DUAN HUIHUA NI YUNZHAO XU 《Biocell》2020,44(4):597-605
Cervical cancer (CESC) is one of the most common cancers and affects the female genital tract. Consistent HPV
infection status has been determined to be a vital cause of tumorigenesis. HPV infection may induce changes to the
immune system and limit the host’s immune response. Immunotherapy is therefore essential to improving the overall
survival of both locally advanced and recurrent CESC patients. Using 304 relevant samples from TCGA, we assessed
immune cell function in CESC patients to better understand the status of both tumor micro-environment cells and
immune cells in CESC. Functional enrichment analysis, pathway enrichment analysis, and PPI network construction
were performed to explore the differentially expressed genes (DEGs). The analysis identified 425 DEGs, which
included 295 up-regulated genes and 130 down-regulated genes. We established that upregulation of CCL5 was
correlated with significantly better survival, meaning that CCL5 expression could serve as a novel prognostic
biomarker for CESC patients. We further focused on CCL5 as a hub gene in CESC, as it had significant correlations
with increased numbers of several types of immune cells. Cell-type fractions of M1 macrophages were significantly
higher in the high-immune-scores group, which was associated with better overall survival. Finally, we concluded that
CCL5 is a promising prognostic biomarker for CESC, as well as a novel chemotherapeutic target. 相似文献
55.
The effect of biochar substituted for anthracite as reductant on magnetizing-roasting pyrite cinder was investigated.The key of magnetizing-roasting is the gasification reaction between reductants and CO2.Since biochar could react with CO2 more rapidly at lower temperature,the reactivity of biochar is better than that of anthracite.The gasification of biochar could produce reducing condition ofφCO/(φCO+φCO2)about 10%-20% between 700-800 ℃,which is in accord with the atmosphere and temperature of Fe2O3 reduction.So it is beneficial to the reduction of iron mineral of pyrite cinder.Compared with anthracite,biochar could decrease the roasting temperature from825 to 750 ℃ and roasting time from 20 to 15min,which shows that a better effect of magnetization could be obtained in the condition of lower temperature and shorter time.Using biochar as reductant,iron concentrate extracted from pyrite cinder as about 64%iron grade could be produced,and the recovery is over 90% under the condition of above 90% grinding particle less than 0.045 mm and magnetic intensity of 0.124-0.194 T. 相似文献
56.
57.
58.
系统地论述了氧气底吹熔炼氧枪的结构、工作原理、设计计算方法、材质及蚀损机理.指出了延长氧枪使用寿命的措施。 相似文献
59.
60.