全文获取类型
收费全文 | 6460篇 |
免费 | 864篇 |
国内免费 | 535篇 |
专业分类
电工技术 | 457篇 |
技术理论 | 1篇 |
综合类 | 893篇 |
化学工业 | 359篇 |
金属工艺 | 242篇 |
机械仪表 | 550篇 |
建筑科学 | 535篇 |
矿业工程 | 189篇 |
能源动力 | 158篇 |
轻工业 | 173篇 |
水利工程 | 689篇 |
石油天然气 | 259篇 |
武器工业 | 227篇 |
无线电 | 839篇 |
一般工业技术 | 572篇 |
冶金工业 | 207篇 |
原子能技术 | 64篇 |
自动化技术 | 1445篇 |
出版年
2024年 | 32篇 |
2023年 | 71篇 |
2022年 | 191篇 |
2021年 | 208篇 |
2020年 | 216篇 |
2019年 | 163篇 |
2018年 | 157篇 |
2017年 | 200篇 |
2016年 | 244篇 |
2015年 | 281篇 |
2014年 | 428篇 |
2013年 | 380篇 |
2012年 | 573篇 |
2011年 | 559篇 |
2010年 | 450篇 |
2009年 | 371篇 |
2008年 | 369篇 |
2007年 | 436篇 |
2006年 | 394篇 |
2005年 | 354篇 |
2004年 | 272篇 |
2003年 | 259篇 |
2002年 | 213篇 |
2001年 | 197篇 |
2000年 | 158篇 |
1999年 | 128篇 |
1998年 | 115篇 |
1997年 | 91篇 |
1996年 | 74篇 |
1995年 | 62篇 |
1994年 | 50篇 |
1993年 | 26篇 |
1992年 | 24篇 |
1991年 | 25篇 |
1990年 | 17篇 |
1989年 | 12篇 |
1988年 | 16篇 |
1987年 | 8篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1983年 | 4篇 |
1982年 | 6篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1972年 | 2篇 |
1959年 | 1篇 |
1957年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有7859条查询结果,搜索用时 93 毫秒
1.
Madhab Chandra Tripathy Debasmita Mondal Karabi Biswas Siddhartha Sen 《International Journal of Circuit Theory and Applications》2015,43(6):776-792
The present work reports the realization of an analog fractional‐order phase‐locked loop (FPLL) using a fractional capacitor. The expressions for bandwidth, capture range, and lock range of the FPLL have been derived analytically and then compared with the experimental observations using LM565 IC. It has been observed that bandwidth and capture range can be extended by using FPLL. It has also been found that FPLL can provide faster response and lower phase error at the time of switching compared to its integer‐order counterpart. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
2.
ULK1 (unc-51 like autophagy activating kinase 1), a mammalian serine/threonine kinase, is a key component of
autophagy initiation complex and helps to induce all types of autophagy. Canonical autophagy is a process in which,
through the interactions of a series of autophagy-related proteins, damaged organelles or misfolded proteins are
engulfed by autophagosomes and then merged with lysosomes to be degraded. Thus, canonical autophagy is an
important constituent part of the cellular “quality control.” Besides, accumulating evidence indicates that ULK1 exerts
autophagy-independent effects in a cell-specific manner. For example, ULK1 facilitates neurite elongation through the
regulation of endoplasmic reticulum (ER)–Golgi trafficking in neurons, stimulates phosphopentose pathway to help
NADPH (nicotinamide adenine dinucleotide phosphate hydrogen) production, and acts as a duplex regulator in type
I IFN (type I interferon) induced innate immune response. Considering the importance and diversity of ULK1 in
various biological processes, this review aims to present a comprehensive overview of autophagy and non-autophagy
related functions of ULK1 in a variety of human physiological, pathological, and disease processes. 相似文献
3.
Sebastian Sjoqvist Kentaro Otake Yoshihiko Hirozane 《International journal of molecular sciences》2020,21(24)
There is a lack of reliable biomarkers for disorders of the central nervous system (CNS), and diagnostics still heavily rely on symptoms that are both subjective and difficult to quantify. The cerebrospinal fluid (CSF) is a promising source of biomarkers due to its close connection to the CNS. Extracellular vesicles are actively secreted by cells, and proteomic analysis of CSF extracellular vesicles (EVs) and their molecular composition likely reflects changes in the CNS to a higher extent compared with total CSF, especially in the case of neuroinflammation, which could increase blood–brain barrier permeability and cause an influx of plasma proteins into the CSF. We used proximity extension assay for proteomic analysis due to its high sensitivity. We believe that this methodology could be useful for de novo biomarker discovery for several CNS diseases. We compared four commercially available kits for EV isolation: MagCapture and ExoIntact (based on magnetic beads), EVSecond L70 (size-exclusion chromatography), and exoEasy (membrane affinity). The isolated EVs were characterized by nanoparticle tracking analysis, ELISA (CD63, CD81 and albumin), and proximity extension assay (PEA) using two different panels, each consisting of 92 markers. The exoEasy samples did not pass the built-in quality controls and were excluded from downstream analysis. The number of detectable proteins in the ExoIntact samples was considerably higher (~150% for the cardiovascular III panel and ~320% for the cell regulation panel) compared with other groups. ExoIntact also showed the highest intersample correlation with an average Pearson’s correlation coefficient of 0.991 compared with 0.985 and 0.927 for MagCapture and EVSecond, respectively. The median coefficient of variation was 5%, 8%, and 22% for ExoIntact, MagCapture, and EVSecond, respectively. Comparing total CSF and ExoIntact samples revealed 70 differentially expressed proteins in the cardiovascular III panel and 17 in the cell regulation panel. To our knowledge, this is the first time that CSF EVs were analyzed by PEA. In conclusion, analysis of CSF EVs by PEA is feasible, and different isolation kits give distinct results, with ExoIntact showing the highest number of identified proteins with the lowest variability. 相似文献
4.
5.
6.
继第二、三期的专题连载(一)和(二)之后,这次介绍门票系统的扩展和系统的优势,并且给出了各种门票的对比表。 相似文献
7.
介绍了当前国际上流行的用半导体可饱和吸收镜来对固体激光器、光纤激光器和半导体激光器进行被动锁模的方法,阐述了半导体可饱和吸收镜用来作为被动锁模吸收体的原理,并介绍了如何利用金属有机气相淀积(MOCVD)技术生长各种波长激光器所需要的半导体可饱和吸收镜. 相似文献
8.
9.
Overview of ship-design expert systems 总被引:1,自引:0,他引:1
Expert systems constitute a branch of artificial intelligence, and their unique characteristics enable computer systems to perform at the level of a human expert by the use of algorithms that can capture domain-specific knowledge. Through an extensive survey of research about ship-design expert systems, we conclude that although development and implementation of expert systems for ship design offer substantial barriers, the shipbuilding industry needs them nonetheless. We examine the major reasons that use of expert systems in this industry has lagged behind. These include the problems of integration with existing computer-aided design systems, problems of knowledge representation and sizable development costs. We discuss in detail some key factors that can lead to the solution of these problems. 相似文献
10.