全文获取类型
收费全文 | 13656篇 |
免费 | 851篇 |
国内免费 | 111篇 |
专业分类
电工技术 | 205篇 |
综合类 | 61篇 |
化学工业 | 3533篇 |
金属工艺 | 347篇 |
机械仪表 | 489篇 |
建筑科学 | 515篇 |
矿业工程 | 21篇 |
能源动力 | 952篇 |
轻工业 | 1277篇 |
水利工程 | 188篇 |
石油天然气 | 224篇 |
武器工业 | 4篇 |
无线电 | 1378篇 |
一般工业技术 | 2527篇 |
冶金工业 | 490篇 |
原子能技术 | 95篇 |
自动化技术 | 2312篇 |
出版年
2024年 | 70篇 |
2023年 | 268篇 |
2022年 | 587篇 |
2021年 | 892篇 |
2020年 | 751篇 |
2019年 | 812篇 |
2018年 | 911篇 |
2017年 | 828篇 |
2016年 | 807篇 |
2015年 | 474篇 |
2014年 | 748篇 |
2013年 | 1366篇 |
2012年 | 902篇 |
2011年 | 947篇 |
2010年 | 663篇 |
2009年 | 594篇 |
2008年 | 418篇 |
2007年 | 355篇 |
2006年 | 302篇 |
2005年 | 192篇 |
2004年 | 174篇 |
2003年 | 152篇 |
2002年 | 119篇 |
2001年 | 91篇 |
2000年 | 90篇 |
1999年 | 81篇 |
1998年 | 137篇 |
1997年 | 115篇 |
1996年 | 96篇 |
1995年 | 68篇 |
1994年 | 51篇 |
1993年 | 59篇 |
1992年 | 46篇 |
1991年 | 39篇 |
1990年 | 40篇 |
1989年 | 32篇 |
1988年 | 25篇 |
1987年 | 24篇 |
1986年 | 34篇 |
1985年 | 27篇 |
1984年 | 27篇 |
1983年 | 25篇 |
1982年 | 21篇 |
1981年 | 19篇 |
1980年 | 19篇 |
1979年 | 16篇 |
1978年 | 18篇 |
1977年 | 18篇 |
1976年 | 24篇 |
1975年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 14 毫秒
31.
Rosanne Hertzberger Ali May Gertjan Kramer Isabelle van Vondelen Douwe Molenaar Remco Kort 《International journal of molecular sciences》2022,23(10)
Glycogen in the female lower reproductive tract is a major carbon source for colonization and acidification by common vaginal Lactobacillus species, such as Lactobacillus crispatus. Previously, we identified the amylopullulanase encoding gene pulA of Lactobacillus crispatus to correlate with the ability to autonomously utilize glycogen for growth. Here, we further characterize genetic variation and differential regulation of pulA affecting the presence of its gene product on the outer surface layer. We show that alpha-glucan degrading activity dissipates when Lactobacillus crispatus is grown on glucose, maltose and maltotriose, in agreement with carbon catabolite repression elements flanking the pulA gene. Proteome analysis of the S-layer confirmed that the amylopullulanase protein is highly abundant in an S-layer enriched fraction, but not in a strain with a defective amylopullulanase variant or in an amylopullulanase-sufficient strain grown on glucose. In addition, we provide evidence that Lactobacillus crispatus pulA mutants are relevant in vivo, as they are commonly observed in metagenome datasets of human vaginal microbial communities. Analysis of the largest publicly available dataset of 1507 human vaginal metagenomes indicates that among the 270 samples that contain a Lactobacillus crispatus pulA gene, 62 samples (23%) had a defective variant of this gene. Taken together, these results demonstrate that both environmental, as well as genetic factors explain the variation of Lactobacillus crispatus alpha-glucosidases in the vaginal environment. 相似文献
32.
33.
Experimental verification of the mathematical surface roughness model for sputtered silicon was performed. The beam shape and its significant level of intensity were determined first by measuring the topography of craters sputtered by focused ion beam (FIB). Then the beam function was generated for various combinations of beam parameters. The material function was developed both by theoretical and experimental analysis. These two functions were then used in the model to calculate the theoretical surface roughness. Microsurface analysis was formed by FIB sputtering of a (100) silicon wafer. The surface roughness at the bottom of the sputtered features was then measured using an atomic force microscope. The theoretical surface roughness was found to be within ±1 and ±5 nm of the measured surface roughness with the measurement uncertainty (standard deviation) of about ±0.36 and ±0.85 nm for Ra and Rt, respectively. 相似文献
34.
Raghu Ramanathan Ahmad Hassan Ali Jamal A. Ibdah 《International journal of molecular sciences》2022,23(13)
Nonalcoholic fatty liver disease (NAFLD) is a global pandemic that affects one-quarter of the world’s population. NAFLD includes a spectrum of progressive liver disease from steatosis to nonalcoholic steatohepatitis (NASH), fibrosis, and cirrhosis and can be complicated by hepatocellular carcinoma. It is strongly associated with metabolic syndromes, obesity, and type 2 diabetes, and it has been shown that metabolic dysregulation is central to its pathogenesis. Recently, it has been suggested that metabolic- (dysfunction) associated fatty liver disease (MAFLD) is a more appropriate term to describe the disease than NAFLD, which puts increased emphasis on the important role of metabolic dysfunction in its pathogenesis. There is strong evidence that mitochondrial dysfunction plays a significant role in the development and progression of NAFLD. Impaired mitochondrial fatty acid oxidation and, more recently, a reduction in mitochondrial quality, have been suggested to play a major role in NAFLD development and progression. In this review, we provide an overview of our current understanding of NAFLD and highlight how mitochondrial dysfunction contributes to its pathogenesis in both animal models and human subjects. Further we discuss evidence that the modification of mitochondrial function modulates NAFLD and that targeting mitochondria is a promising new avenue for drug development to treat NAFLD/NASH. 相似文献
35.
36.
37.
In this paper an approach based on an evolutionary algorithm to design synchronous sequential logic circuits with minimum number of logic gates is suggested. The proposed method consists of four main stages. The first stage is concerned with the use of genetic algorithms (GA) for the state assignment problem to compute optimal binary codes for each symbolic state and construct the state transition table of finite state machine (FSM). The second stage defines the subcircuits required to achieve the desired functionality. The third stage evaluates the subcircuits using extrinsic Evolvable Hardware (EHW). During the fourth stage, the final circuit is assembled. The obtained results compare favourably against those produced by manual methods and other methods based on heuristic techniques. 相似文献
38.
Arshad Ali Samarasinghe Supun Akeel F. A. M. Urbahs Aleksandrs 《Journal of Mechanical Science and Technology》2020,34(6):2455-2468
Journal of Mechanical Science and Technology - This study aims to develop a simplified approach for the design of high-speed wind tunnels, operating within the range of Mach 1-4. The study is... 相似文献
39.
Trabelsi Ali Rezgui Mohamed Ali 《The International Journal of Advanced Manufacturing Technology》2020,106(7):2829-2841
The International Journal of Advanced Manufacturing Technology - The paper discusses a generic procedure for the parameter design of product and process development using planned and non-planned... 相似文献
40.
Xuejiao Liu Zhixin Xu Asma Iqbal Ming Chen Nazakat Ali CheeTongJohn Low Rongrong Qi Jiantao Zai Xuefeng Qian 《纳微快报(英文)》2021,(3):197-208
Huge volume changes of Si during lithiation/delithiation lead to regeneration of solid-electrolyte interphase(SEI)and consume electrolyte.In this article,γ-glycidoxypropyl trimethoxysilane(GOPS)was incorporated in Si/PEDOT:PSS electrodes to construct a flexible and conductive artificial SEI,effectively suppressing the consumption of electrolyte.The optimized electrode can maintain 1000 mAh g^−1 for nearly 800 cycles under limited electrolyte compared with 40 cycles of the electrodes without GOPS.Also,the optimized electrode exhibits excellent rate capability.The use of GOPS greatly improves the interface compatibility between Si and PEDOT:PSS.XPS Ar+etching depth analysis proved that the addition of GOPS is conducive to forming a more stable SEI.A full battery assembled with NCM 523 cathode delivers a high energy density of 520 Wh kg^−1,offering good stability. 相似文献