全文获取类型
收费全文 | 60933篇 |
免费 | 6621篇 |
国内免费 | 4865篇 |
专业分类
电工技术 | 5914篇 |
技术理论 | 1篇 |
综合类 | 5863篇 |
化学工业 | 3478篇 |
金属工艺 | 4438篇 |
机械仪表 | 8872篇 |
建筑科学 | 2321篇 |
矿业工程 | 2494篇 |
能源动力 | 972篇 |
轻工业 | 3517篇 |
水利工程 | 824篇 |
石油天然气 | 1090篇 |
武器工业 | 509篇 |
无线电 | 6613篇 |
一般工业技术 | 5435篇 |
冶金工业 | 2027篇 |
原子能技术 | 303篇 |
自动化技术 | 17748篇 |
出版年
2024年 | 229篇 |
2023年 | 1127篇 |
2022年 | 1791篇 |
2021年 | 2071篇 |
2020年 | 2234篇 |
2019年 | 1760篇 |
2018年 | 1603篇 |
2017年 | 2018篇 |
2016年 | 2281篇 |
2015年 | 2547篇 |
2014年 | 3923篇 |
2013年 | 3789篇 |
2012年 | 4648篇 |
2011年 | 4658篇 |
2010年 | 3425篇 |
2009年 | 3564篇 |
2008年 | 3490篇 |
2007年 | 4273篇 |
2006年 | 3986篇 |
2005年 | 3415篇 |
2004年 | 2742篇 |
2003年 | 2353篇 |
2002年 | 1937篇 |
2001年 | 1754篇 |
2000年 | 1384篇 |
1999年 | 1045篇 |
1998年 | 810篇 |
1997年 | 674篇 |
1996年 | 539篇 |
1995年 | 500篇 |
1994年 | 431篇 |
1993年 | 294篇 |
1992年 | 236篇 |
1991年 | 184篇 |
1990年 | 151篇 |
1989年 | 146篇 |
1988年 | 109篇 |
1987年 | 46篇 |
1986年 | 41篇 |
1985年 | 36篇 |
1984年 | 29篇 |
1983年 | 23篇 |
1982年 | 14篇 |
1981年 | 14篇 |
1980年 | 13篇 |
1979年 | 15篇 |
1978年 | 7篇 |
1976年 | 8篇 |
1974年 | 6篇 |
1959年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
为探索生物活性未知的双对苯醌(2,7-dihydroxy-3,6,9-trimethyl-9H-xanthene-1,4,5,8-tetraone,DTXT)的抗氧化活性,并提高其发酵产量,考察DTXT的还原力以及对超氧阴离子自由基、羟自由基、1,1-二苯基-2-三硝基苯肼(1,1-diphenyl-2-picrylhydrazyl,DPPH)自由基的清除效果,在单因素试验基础上,采用响应面法优化了DTXT产生菌瓶生顶孢霉(Acremonium cavaraeanum)CA022菌株的固体发酵培养基。结果表明:在200 μg/mL质量浓度下,DTXT的还原力与芦丁差异不显著,高于VE和2,6-二叔丁基-4甲基苯酚,对超氧阴离子自由基清除率达到67.00%,对羟自由基清除率达到78.83%,对DPPH自由基清除率达到76.53%。通过响应面试验,得到最佳培养基配方为葡萄糖0.773%、硝酸钠0.185%、H3BO3 0.032%、VB1 100 μg/100 g,在此条件下实际获得的DTXT产量为4 150.8 mg/kg,是优化前产量的(2 864.83 mg/kg)1.45 倍。 相似文献
2.
3.
边坡位移的时间序列曲线存在复杂的非线性特性,传统的预测模型精度不足以满足预测要求。为此提出了基于变分模态分解的鸟群优化-核极限学习机的预测模型,并用于河北省某水泥厂的边坡位移预测。该方法首先采用VMD把边坡位移序列分解为一系列的有限带宽的子序列,再对各子序列分别采用相空间重构并用核极限学习机预测,采用鸟群算法优化相空间重构的嵌入维度和KELM中惩罚系数和核参数三个数值,以取得最优预测模型。最后将各个子序列预测值叠加,得到边坡位移的最终预测值。结果表明:和KELM、BSA-KELM、EEMD-BSA-KELM模型相比,基于VMD的BSA-KELM预测精度更高,为边坡位移的预测提供一种有效的方法。 相似文献
4.
在传统的轮胎表面缺陷依靠人工检测,存在劳动强度高、受人的主观影响大以及效率低下的问题。针对这一现象,研究了一种基于机器视觉的轮胎表面缺陷3D检测系统。该系统依靠机器视觉系统获取检测轮胎的表面图像,然后创建3D模型、判定缺陷类型,最终实现实时自动预警,为轮胎生产商提供一种自动化检测方案。系统集成了先进的技术、软件和工具,配套的信息管控系统可以对轮胎型号和生产数据进行采集、存储、分析,以便在生产过程中实现更高效、更可靠的质量控制,具有较高的实际应用推广价值。 相似文献
5.
Corey Andrews Yiting Xu Michael Kirberger Jenny J. Yang 《International journal of molecular sciences》2021,22(1)
Calmodulin (CaM) is an important intracellular protein that binds Ca2+ and functions as a critical second messenger involved in numerous biological activities through extensive interactions with proteins and peptides. CaM’s ability to adapt to binding targets with different structures is related to the flexible central helix separating the N- and C-terminal lobes, which allows for conformational changes between extended and collapsed forms of the protein. CaM-binding targets are most often identified using prediction algorithms that utilize sequence and structural data to predict regions of peptides and proteins that can interact with CaM. In this review, we provide an overview of different CaM-binding proteins, the motifs through which they interact with CaM, and shared properties that make them good binding partners for CaM. Additionally, we discuss the historical and current methods for predicting CaM binding, and the similarities and differences between these methods and their relative success at prediction. As new CaM-binding proteins are identified and classified, we will gain a broader understanding of the biological processes regulated through changes in Ca2+ concentration through interactions with CaM. 相似文献
6.
7.
Against the background of smart manufacturing and Industry 4.0, how to achieve real-time scheduling has become a problem to be solved. In this regard, automatic design for shop scheduling based on hyper-heuristics has been widely studied, and a number of reviews and scheduling algorithms have been presented. Few studies, however, have specifically discussed the technical points involved in algorithm development. This study, therefore, constructs a general framework for automatic design for shop scheduling strategies based on hyper-heuristics, and various state-of-the-art technical points in the development process are summarized. First, we summarize the existing types of shop scheduling strategies and classify them using a new classification method. Second, we summarize an automatic design algorithm for shop scheduling. Then, we investigate surrogate-assisted methods that are popular in the current algorithm field. Finally, current problems and challenges are discussed, and potential directions for future research are proposed. 相似文献
8.
Effects of Winding Attachment Positions on Output Characteristics of Flux‐Modulating Synchronous Machines 下载免费PDF全文
Hirofumi Aoki Tadashi Fukami Kazuo Shima Toshihiro Tsuda Mitsuhiro Kawamura 《Electrical Engineering in Japan》2015,191(3):40-49
The flux‐modulating synchronous machine (FMSM) is a new type of multipole SM with nonoverlapping concentrated armature and field windings on the stator. This paper compares the output characteristics of two FMSMs through finite element analysis (FEA) and experiments. In both of the FMSMs, the attachment positions of the armature and field windings are swapped. To determine the reason for the discrepancies in their output characteristics, unsaturated inductances were calculated using a d‐‐q equivalent circuit. In addition, the calculated results of the inductances were confirmed through a visualization of the leakage fluxes using FEA. The results of the study show that the synchronous inductance can be reduced by attaching the armature winding to the air‐gap side of the stator teeth and that the reduction leads to an increase in output power. 相似文献
9.
This paper considers the scheduling problem of minimizing earliness–tardiness (E/T) on a single batch processing machine with a common due date. The problem is extended to the environment of non-identical job sizes. First, a mathematical model is formulated, which is tested effectively under IBM ILOG CPLEX using the constraint programming solver. Then several optimal properties are given to schedule batches effectively, and by introducing the concept of ARB (Attribute Ratio of Batch), it is proven that the ARB of each batch should be made as small as possible in order to minimize the objective, designed as the heuristic information for assigning jobs into batches. Based on these properties, a heuristic algorithm MARB (Minimum Attribute Ratio of Batch) for batch forming is proposed, and a hybrid genetic algorithm is developed for the problem under study by combining GA (genetic algorithm) with MARB. Experimental results demonstrate that the proposed algorithm outperforms other algorithms in the literature, both for small and large problem instances. 相似文献
10.
Jie-Long He An-Te Chen Jyong-Huei Lee Shih-Kang Fan 《International journal of molecular sciences》2015,16(9):22319-22332
The basic structural and functional unit of a living organism is a single cell. To understand the variability and to improve the biomedical requirement of a single cell, its analysis has become a key technique in biological and biomedical research. With a physical boundary of microchannels and microstructures, single cells are efficiently captured and analyzed, whereas electric forces sort and position single cells. Various microfluidic techniques have been exploited to manipulate single cells through hydrodynamic and electric forces. Digital microfluidics (DMF), the manipulation of individual droplets holding minute reagents and cells of interest by electric forces, has received more attention recently. Because of ease of fabrication, compactness and prospective automation, DMF has become a powerful approach for biological application. We review recent developments of various microfluidic chips for analysis of a single cell and for efficient genetic screening. In addition, perspectives to develop analysis of single cells based on DMF and emerging functionality with high throughput are discussed. 相似文献