全文获取类型
收费全文 | 99562篇 |
免费 | 11982篇 |
国内免费 | 4999篇 |
专业分类
电工技术 | 5271篇 |
技术理论 | 9篇 |
综合类 | 8475篇 |
化学工业 | 16404篇 |
金属工艺 | 3355篇 |
机械仪表 | 5010篇 |
建筑科学 | 8049篇 |
矿业工程 | 2952篇 |
能源动力 | 2662篇 |
轻工业 | 7492篇 |
水利工程 | 2110篇 |
石油天然气 | 2753篇 |
武器工业 | 895篇 |
无线电 | 9194篇 |
一般工业技术 | 10740篇 |
冶金工业 | 4915篇 |
原子能技术 | 934篇 |
自动化技术 | 25323篇 |
出版年
2024年 | 196篇 |
2023年 | 1632篇 |
2022年 | 2898篇 |
2021年 | 4615篇 |
2020年 | 3054篇 |
2019年 | 2987篇 |
2018年 | 3166篇 |
2017年 | 3994篇 |
2016年 | 5266篇 |
2015年 | 5826篇 |
2014年 | 6931篇 |
2013年 | 7552篇 |
2012年 | 6010篇 |
2011年 | 5961篇 |
2010年 | 4717篇 |
2009年 | 5116篇 |
2008年 | 5179篇 |
2007年 | 6419篇 |
2006年 | 6325篇 |
2005年 | 5405篇 |
2004年 | 3996篇 |
2003年 | 3514篇 |
2002年 | 2730篇 |
2001年 | 1945篇 |
2000年 | 1508篇 |
1999年 | 1343篇 |
1998年 | 1017篇 |
1997年 | 901篇 |
1996年 | 799篇 |
1995年 | 706篇 |
1994年 | 649篇 |
1993年 | 511篇 |
1992年 | 452篇 |
1991年 | 349篇 |
1990年 | 326篇 |
1989年 | 309篇 |
1988年 | 244篇 |
1987年 | 156篇 |
1986年 | 170篇 |
1985年 | 180篇 |
1984年 | 203篇 |
1983年 | 136篇 |
1982年 | 128篇 |
1981年 | 113篇 |
1980年 | 121篇 |
1979年 | 83篇 |
1978年 | 55篇 |
1964年 | 65篇 |
1962年 | 71篇 |
1955年 | 57篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Amyloid precursor protein (APP) is a type 1 transmembrane glycoprotein, and its homologs amyloid precursor-like protein 1 (APLP1) and amyloid precursor-like protein 2 (APLP2) are highly conserved in mammals. APP and APLP are known to be intimately involved in the pathogenesis and progression of Alzheimer’s disease and to play important roles in neuronal homeostasis and development and neural transmission. APP and APLP are also expressed in non-neuronal tissues and are overexpressed in cancer cells. Furthermore, research indicates they are involved in several cancers. In this review, we examine the biological characteristics of APP-related family members and their roles in cancer. 相似文献
72.
目的 在传统器物的创新设计中,最重要的环节是了解消费者对所使用产品的不同感受与意向并转换为具体的设计要素.研究消费者心理的感性因素与传统器物设计元素之间的联系,确定设计要素,从而对产品进行创新设计,为提升传统器物附加值作出贡献.方法 以中国传统器物茶宠为例,首先对8位相关的茶宠专家进行访谈,通过魅力工学中的评价构造法整理并提取魅力因子,设计出问卷调查表;然后以访谈内容为依据,使用问卷调查法得到大众对茶宠的魅力评价,共回收84份有效问卷;最后应用数量化一类分析茶宠魅力因子影响权重.结果 得到了数量化一类统计表,选取了其中影响因素较大的魅力因子作为茶宠设计前的风格定调考量.结论 通过茶宠的研究案例证明了该理论的可行性,为未来传统器物的设计提供了更多元且新颖的设计依据. 相似文献
73.
74.
75.
76.
77.
Cell surface and secreted proteins provide essential functions for multicellular life. They enter the endoplasmic reticulum (ER) lumen co-translationally, where they mature and fold into their complex three-dimensional structures. The ER is populated with a host of molecular chaperones, associated co-factors, and enzymes that assist and stabilize folded states. Together, they ensure that nascent proteins mature properly or, if this process fails, target them for degradation. BiP, the ER HSP70 chaperone, interacts with unfolded client proteins in a nucleotide-dependent manner, which is tightly regulated by eight DnaJ-type proteins and two nucleotide exchange factors (NEFs), SIL1 and GRP170. Loss of SIL1′s function is the leading cause of Marinesco-Sjögren syndrome (MSS), an autosomal recessive, multisystem disorder. The development of animal models has provided insights into SIL1′s functions and MSS-associated pathologies. This review provides an in-depth update on the current understanding of the molecular mechanisms underlying SIL1′s NEF activity and its role in maintaining ER homeostasis and normal physiology. A precise understanding of the underlying molecular mechanisms associated with the loss of SIL1 may allow for the development of new pharmacological approaches to treat MSS. 相似文献
78.
Jinming Wang Meng Yang Guodong Zou Di Liu Qiuming Peng 《Advanced functional materials》2021,31(21):2101180
Lithium (Li) metal, as an appealing candidate for the next-generation of high-energy-density batteries, is plagued by its safety issue mainly caused by uncontrolled dendrite growth and infinite volume expansion. Developing new materials that can improve the performance of Li-metal anode is one of the urgent tasks. Herein, a new MXene derivative containing pure rutile TiO2 and N-doped carbon prepared by heat-treating MXene under a mixing gas, exhibiting high chemical activity in molten Li, is reported. The lithiation MXene derivative with a hybrid of LiTiO2-Li3N-C and Li offers outstanding electrochemical properties. The symmetrical cell assembling lithiation MXene derivative hybrid anode exhibits an ultra-long cycle lifespan of 2000 h with an overpotential of ≈30 mV at 1 mA cm−2, which overwhelms Li-based anodes reported so far. Additionally, long-term operations of 34, 350, and 500 h at 10 mA cm−2 can be achieved in symmetrical cells at temperatures of −10, 25, and 50 °C, respectively. Both experimental tests and density functional theory calculations confirm that the LiTiO2-Li3N-C skeleton serves as a promising host for Li infusion by alleviating volume variation. Simultaneously, the superlithiophilic interphase of Li3N guides Li deposition along the LiTiO2-Li3N-C skeleton to avoid dendrite growth. 相似文献
79.
Sorting-based reversible data hiding (RDH) methods like pixel-value-ordering (PVO) can predict pixel values accurately and achieve an extremely low distortion on the embedded image. However, the excellent performance of these methods was not well explained in previous works, and there are unexploited common points among them. In this paper, we propose a general multi-predictor (GMP) framework to summarize PVO-based RDH methods and explain their high prediction accuracy. Moreover, by utilizing the proposed GMP framework, a more efficient sorting-based RDH method is given as an example to show the generality and applicability of our framework. Comparing with other PVO-based methods, the proposed example method can achieve significant improvement in embedding performance. It is hopeful that more efficient sorting-based RDH algorithms can be designed according to our proposed framework by designing better predictors and their combination methods. 相似文献
80.