全文获取类型
收费全文 | 1125篇 |
免费 | 77篇 |
国内免费 | 45篇 |
专业分类
电工技术 | 36篇 |
综合类 | 45篇 |
化学工业 | 168篇 |
金属工艺 | 10篇 |
机械仪表 | 32篇 |
建筑科学 | 110篇 |
矿业工程 | 9篇 |
能源动力 | 7篇 |
轻工业 | 165篇 |
水利工程 | 13篇 |
石油天然气 | 39篇 |
武器工业 | 10篇 |
无线电 | 76篇 |
一般工业技术 | 87篇 |
冶金工业 | 198篇 |
原子能技术 | 2篇 |
自动化技术 | 240篇 |
出版年
2024年 | 5篇 |
2023年 | 12篇 |
2022年 | 70篇 |
2021年 | 77篇 |
2020年 | 35篇 |
2019年 | 44篇 |
2018年 | 52篇 |
2017年 | 29篇 |
2016年 | 43篇 |
2015年 | 23篇 |
2014年 | 76篇 |
2013年 | 84篇 |
2012年 | 68篇 |
2011年 | 78篇 |
2010年 | 49篇 |
2009年 | 49篇 |
2008年 | 53篇 |
2007年 | 64篇 |
2006年 | 45篇 |
2005年 | 37篇 |
2004年 | 36篇 |
2003年 | 28篇 |
2002年 | 33篇 |
2001年 | 14篇 |
2000年 | 16篇 |
1999年 | 10篇 |
1997年 | 8篇 |
1996年 | 5篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1986年 | 2篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1968年 | 2篇 |
1966年 | 2篇 |
1965年 | 5篇 |
1964年 | 8篇 |
1963年 | 5篇 |
1962年 | 3篇 |
1961年 | 5篇 |
1960年 | 10篇 |
1959年 | 5篇 |
1958年 | 3篇 |
1957年 | 3篇 |
1956年 | 9篇 |
1955年 | 4篇 |
1954年 | 4篇 |
排序方式: 共有1247条查询结果,搜索用时 9 毫秒
21.
针对高速铁路LTE-R越区切换中,A3事件下的越区切换算法容易出现乒乓效应(PPE)和无线链路连接失败(WLF)的问题,提出了粒子群优化(PSO)灰狼算法改进的RBF神经网络(IGWO-RBF)的越区切换优化算法。该算法采集大量列车以不同速度(0~100 m/s)运行在特定环境中时切换成功率高的切换迟滞门限[(Hys)]和触发延迟时间[(TTT)]参数集,送入改进的RBF神经网络,训练完成后得到不同速度下的[Hys]和[TTT]的拟合曲线。根据列车接收到的参考信号接收质量(RSRQ),加入自矫正项对[Hys]和[TTT]进行二次优化调整。在matlab上进行仿真实验,结果表明提出的算法减小了掉话率和乒乓切换率,提高了列车在高速环境下的切换成功率及鲁棒性。 相似文献
22.
In collaborative crowdsourcing communities for open innovation, users generate and submit ideas as idea co‐creators. Firms then select and implement valuable ideas for new product development. Despite the popularity and success of these open innovation communities, relatively little is known about the factors that determine the implementation of the user‐generated ideas. Based on research on individual creativity, we propose a conceptual model integrating users' previous experience, idea presentation characteristics and feedback valence to explain the likelihood of idea implementation. We validate our research model with a panel data analysis of 43 550 ideas submitted by 16 360 users in the MIUI new product development community hosted by Xiaomi, a large electronics manufacturing company in China. We find an inverted U‐shaped relationship between users' past successful experience and idea implementation. Furthermore, the length of ideas is positively associated with the likelihood of idea implementation. There is also an inverted U‐shaped relationship between supporting evidence and idea implementation. Finally, we demonstrate the negative effect of positive feedback and the positive effect of negative feedback on idea implementation. These findings offer rich insights to understand the phenomenon of open innovation better. Theoretical and practical implications are discussed. 相似文献
23.
24.
25.
Jorge Lopez-Tello Maria Angeles Jimenez-Martinez Esteban Salazar-Petres Ritik Patel Amy L. George Richard G. Kay Amanda N. Sferruzzi-Perri 《International journal of molecular sciences》2022,23(11)
Pregnancy is characterized by adaptations in the function of several maternal body systems that ensure the development of the fetus whilst maintaining health of the mother. The renal system is responsible for water and electrolyte balance, as well as waste removal. Thus, it is imperative that structural and functional changes occur in the kidney during pregnancy. However, our knowledge of the precise morphological and molecular mechanisms occurring in the kidney during pregnancy is still very limited. Here, we investigated the changes occurring in the mouse kidney during pregnancy by performing an integrated analysis involving histology, gene and protein expression assays, mass spectrometry profiling and bioinformatics. Data from non-pregnant and pregnant mice were used to identify critical signalling pathways mediating changes in the maternal kidneys. We observed an expansion of renal medulla due to proliferation and infiltration of interstitial cellular constituents, as well as alterations in the activity of key cellular signalling pathways (e.g., AKT, AMPK and MAPKs) and genes involved in cell growth/metabolism (e.g., Cdc6, Foxm1 and Rb1) in the kidneys during pregnancy. We also generated plasma and urine proteomic profiles, identifying unique proteins in pregnancy. These proteins could be used to monitor and study potential mechanisms of renal adaptations during pregnancy and disease. 相似文献
26.
Junya Kojima Masanori Ono Naoaki Kuji Hirotaka Nishi 《International journal of molecular sciences》2022,23(14)
In humans, the placenta provides the only fetomaternal connection and is essential for establishing a pregnancy as well as fetal well-being. Additionally, it allows maternal physiological adaptation and embryonic immunological acceptance, support, and nutrition. The placenta is derived from extra-embryonic tissues that develop rapidly and dynamically in the first weeks of pregnancy. It is primarily composed of trophoblasts that differentiate into villi, stromal cells, macrophages, and fetal endothelial cells (FEC). Placental differentiation may be closely related to perinatal diseases, including fetal growth retardation (FGR) and hypertensive disorders of pregnancy (HDP), and miscarriage. There are limited findings regarding human chorionic villous differentiation and placental development because conducting in vivo studies is extremely difficult. Placental tissue varies widely among species. Thus, experimental animal findings are difficult to apply to humans. Early villous differentiation is difficult to study due to the small tissue size; however, a detailed analysis can potentially elucidate perinatal disease causes or help develop novel therapies. Artificial induction of early villous differentiation using human embryonic stem (ES) cells/induced pluripotent stem (iPS) cells was attempted, producing normally differentiated villi that can be used for interventional/invasive research. Here, we summarized and correlated early villous differentiation findings and discussed clinical diseases. 相似文献
27.
28.
Projects are inherently uncertain and face unexpected events, from small changes in scope to unforeseen client’s bankruptcy. This paper studies how project managers respond to such events and how successful and unsuccessful responses differ from the perspective of the practitioner. We analysed 44 unexpected events faced by 22 experienced project managers in defence and defence-related organisations. The project managers compared two unexpected events that they faced, one that they considered the response successful and the other unsuccessful. We identified three pillars supporting successful responses to unexpected events: (1) responsive and functioning structure at the organisational level, (2) good interpersonal relationship at the group level and (3) competent people at the individual level. The events and respective responses analysed suggest that improvement in project management can be achieved by better managing these three pillars, allowing project and programme managers to “create their own luck”. 相似文献
29.
Milica Jovanovi Krivokua Aleksandra Viloti Mirjana Nacka-Aleksi Andrea Pirkovi Danica uji Janko Legner Dragana Dekanski
anka Boji-Trbojevi 《International journal of molecular sciences》2022,23(1)
Galectins are a family of conserved soluble proteins defined by an affinity for β-galactoside structures present on various glycoconjugates. Over the past few decades, galectins have been recognized as important factors for successful implantation and maintenance of pregnancy. An increasing number of studies have demonstrated their involvement in trophoblast cell function and placental development. In addition, several lines of evidence suggest their important roles in feto-maternal immune tolerance regulation and angiogenesis. Changed or dysregulated galectin expression is also described in pregnancy-related disorders. Although the data regarding galectins’ clinical relevance are still at an early stage, evidence suggests that some galectin family members are promising candidates for better understanding pregnancy-related pathologies, as well as predicting biomarkers. In this review, we aim to summarize current knowledge of galectins in early pregnancy as well as in pregnancy-related pathologies. 相似文献
30.
Sophie Perrier dHauterive Romann Close Virginie Gridelet Marie Mawet Michelle Nisolle Vincent Geenen 《International journal of molecular sciences》2022,23(3)
Human chorionic gonadotropin (hCG) has four major isoforms: classical hCG, hyperglycosylated hCG, free β subunit, and sulphated hCG. Classical hCG is the first molecule synthesized by the embryo. Its RNA is transcribed as early as the eight-cell stage and the blastocyst produces the protein before its implantation. This review synthetizes everything currently known on this multi-effect hormone: hCG levels, angiogenetic activity, immunological actions, and effects on miscarriages and thyroid function. 相似文献