全文获取类型
收费全文 | 32424篇 |
免费 | 3955篇 |
国内免费 | 1672篇 |
专业分类
电工技术 | 6462篇 |
综合类 | 3002篇 |
化学工业 | 2529篇 |
金属工艺 | 590篇 |
机械仪表 | 1988篇 |
建筑科学 | 3210篇 |
矿业工程 | 521篇 |
能源动力 | 1090篇 |
轻工业 | 5922篇 |
水利工程 | 779篇 |
石油天然气 | 914篇 |
武器工业 | 333篇 |
无线电 | 2538篇 |
一般工业技术 | 3669篇 |
冶金工业 | 1342篇 |
原子能技术 | 500篇 |
自动化技术 | 2662篇 |
出版年
2024年 | 225篇 |
2023年 | 671篇 |
2022年 | 1407篇 |
2021年 | 1454篇 |
2020年 | 1479篇 |
2019年 | 1295篇 |
2018年 | 1220篇 |
2017年 | 1540篇 |
2016年 | 1594篇 |
2015年 | 1659篇 |
2014年 | 2028篇 |
2013年 | 2111篇 |
2012年 | 2621篇 |
2011年 | 2681篇 |
2010年 | 1812篇 |
2009年 | 1790篇 |
2008年 | 1620篇 |
2007年 | 1831篇 |
2006年 | 1580篇 |
2005年 | 1280篇 |
2004年 | 1003篇 |
2003年 | 834篇 |
2002年 | 645篇 |
2001年 | 583篇 |
2000年 | 466篇 |
1999年 | 411篇 |
1998年 | 334篇 |
1997年 | 262篇 |
1996年 | 233篇 |
1995年 | 222篇 |
1994年 | 174篇 |
1993年 | 148篇 |
1992年 | 132篇 |
1991年 | 90篇 |
1990年 | 89篇 |
1989年 | 70篇 |
1988年 | 52篇 |
1987年 | 44篇 |
1986年 | 29篇 |
1985年 | 32篇 |
1984年 | 27篇 |
1983年 | 13篇 |
1982年 | 23篇 |
1980年 | 25篇 |
1979年 | 22篇 |
1965年 | 15篇 |
1964年 | 19篇 |
1963年 | 15篇 |
1961年 | 13篇 |
1957年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
目的对超临界CO2萃取油基钻屑中油相工艺参数进行优化。 方法采用响应曲面法对影响超临界CO2萃取工艺的重要参数进行具体实验并根据实验结果进行数值模拟,通过模拟得出萃取时间、压力、温度和超临界CO2流量等参数的优化数据。 结果响应曲面分析了各变量之间对萃取效果的影响,基于萃取数据建立了二次多项式模型,能够较好地拟合实验结果,得出最佳萃取条件为萃取压力25 MPa、温度323.15 K、时间90 min和流量25.0 L/h。 结论通过具体实验数据结合响应曲面法得出了最佳萃取条件,在该条件下油类最大去除率为95.22%。利用气相色谱仪-质谱联用仪(GC-MS)分析萃取物前后性状未发生明显变化,该方法能够更好地实现固液分离和资源回收。 相似文献
92.
Yudi Liu Jinyu Yi Haokang Jia Yutong Miao Maolin Hou 《International journal of molecular sciences》2022,23(15)
The white-backed planthopper (WBPH), Sogatella furcifera, is one of the most important piercing-sucking pests of rice (Oryza sativa) in Asia. Mucin-like salivary protein (SFMLP) is highly expressed in the salivary glands of WBPH, which plays an important role in WBPH feeding. In this study, WBPH injected with dsSFMLP had difficulty in sucking phloem sap from rice plants, which significantly reduced their food intake, weight, and survival. In contrast, the knockdown of the SFMLP gene had only a marginal effect on the survival of WBPH fed an artificial diet. Further studies showed that silencing SFMLP resulted in the short and single-branched salivary sheaths secretion and less formation of salivary flanges in rice. These data suggest that SFMLP is involved in the formation of the salivary sheath and is essential for feeding in WBPH. Overexpression of the SFMLP gene in rice plants promoted the feeding of WBPH, whereas silencing the gene in rice plants significantly decreased WBPH performance. Additionally, it was found that overexpression of SFMLP in rice plants elicited the signalling pathway of SA (salicylic acid) while suppressing JA (jasmonic acid); in contrast, silencing of the SFMLP gene in rice plants showed the opposite results. This study clarified the function of SFMLP in WBPH feeding as well as mediating rice defences. 相似文献
93.
美国城市公共安全应急体系建设方法研究 总被引:2,自引:0,他引:2
全面紧急事态管理是美国公共安全管理中最基本的原则,包括全危险方法、综合紧急事态管理系统、紧急事态管理的生命周期、对各级政府及组织紧急救援资源的统一调配.美国国土安全部确定了了解、防止、保护、应对、恢复、服务和组织品质七大安全战略目标.美国联邦紧急事务管理局除制订全国防灾计划外,还制订可持续减灾计划和应急反应计划.社区应急反应小组是美国重要的市民组织队伍. 相似文献
94.
Gaojian Li Jinqi Shu Jing Jin Jianhong Shu Huapeng Feng Jian Chen Yulong He 《International journal of molecular sciences》2022,23(14)
Mycoplasma hyopneumoniae (Mhp), the primary pathogen causing Mycoplasma pneumonia of swine (MPS), brings massive economic losses worldwide. Genomic variability and post-translational protein modification can enhance the immune evasion of Mhp, which makes MPS prone to recurrent outbreaks on farms, even with vaccination or other treatments. The reverse vaccinology pipeline has been developed as an attractive potential method for vaccine development due to its high efficiency and applicability. In this study, a multi-epitope vaccine for Mhp was developed, and its immune responses were evaluated in mice and piglets. Genomic core proteins of Mhp were retrieved through pan-genome analysis, and four immunodominant antigens were screened by host homologous protein removal, membrane protein screening, and virulence factor identification. One immunodominant antigen, (membrane nuclease), was expressed by E. coli and named rMhp597. For epitope prioritization, 35 B-cell-derived epitopes were identified from the four immunodominant antigens, and 10 MHC-I and 6 MHC-II binding epitopes were further identified. The MHC-I/II binding epitopes were merged and combined to produce recombinant proteins MhpMEV and MhpMEVC6His, which were used for animal immunization and structural analysis, respectively. Immunization of mice and piglets demonstrated that MhpMEV could induce humoral and cellular immune responses. The mouse serum antibodies could detect all 11 synthetic epitopes, and the piglet antiserum suppressed the nuclease activity of rMhp597. Moreover, piglet serum antibodies could also detect cultured Mhp strain 168. In summary, this study provides immunoassay results for a multi-epitope vaccine derived from the reverse vaccinology pipeline, and offers an alternative vaccine for MPS. AAV27984.1相似文献
95.
一种新的TOC含量拟合方法研究与应用 总被引:2,自引:0,他引:2
由于取样的限制,通常在烃源岩评价中往往只能获得十分有限的实测烃源岩的TOC含量数据。但随着我国多数盆地精细勘探的深入,需要更加精细的烃源岩评价,因此,人们对测井数据拟合烃源岩的TOC含量变化越来越重视。目前该技术最先进的是人工神经网络拟合方法,但多种神经网络在拟合高成熟度碳酸盐岩烃源岩地层的TOC含量时相关性均不够高。针对研究区内烃源岩的特点,尝试了一种用图版分类-模糊排队-BP神经网络联合拟合TOC含量的新方法。利用该方法对鄂尔多斯盆地马家沟组的测井资料和实测总有机碳资料进行数据处理,将结果与ΔlogR方法、模糊神经网络方法的结果相比较,证实该方法的结果与实测值有更好的相关性,为系统了解鄂尔多斯盆地下古生界烃源岩发育提供了一定的科学依据。 相似文献
96.
97.
Mengyao Liu Nana Li Shan Shan Yudong Shi Yuanbing Zhu Weihong Lu 《International journal of molecular sciences》2022,23(9)
With the advancement of science and technology, humans are chronically exposed to ionizing radiation. It is crucial to look for efficient and low-toxic anti-radiation agents. Through preliminary screening, we found that Acanthopanax senticosus polysaccharide (ASPS) played a major role in regulating immune damage caused by radiation. The objective of this study was to apply the Caenorhabditis elegans—P. aeruginosa (PA14) infection model to illuminate the mechanism of ASPS increasing the pathogen resistance of radiation-damaged nematodes. Results indicated that ASPS (1 mg/mL) significantly enhanced the pathogen resistance of radiation-damaged nematodes by directly elevating the immune response of nematodes rather than by affecting the bacterial activity. Through further research on the p38 MAPK signaling pathway and related mutants, we found that ASPS functioned by the p38 MAPK pathway in the intestine, and SKN-1, ATF-7 as the downstream targets of PMK-1 participated the regulation of ASPS. In addition, ASPS markedly alleviated the stress status of damaged nematodes by regulating oxidative stress. Collectively, our findings suggest that ASPS enhances the pathogen resistance of radiation-damaged nematodes through the intestinal p38MAPK-SKN-1/ATF-7 pathway and stress response. 相似文献
98.
99.
100.