全文获取类型
收费全文 | 38169篇 |
免费 | 5599篇 |
国内免费 | 3832篇 |
专业分类
电工技术 | 3935篇 |
综合类 | 5614篇 |
化学工业 | 2593篇 |
金属工艺 | 960篇 |
机械仪表 | 2298篇 |
建筑科学 | 1933篇 |
矿业工程 | 805篇 |
能源动力 | 843篇 |
轻工业 | 1876篇 |
水利工程 | 1088篇 |
石油天然气 | 1183篇 |
武器工业 | 556篇 |
无线电 | 5613篇 |
一般工业技术 | 3988篇 |
冶金工业 | 954篇 |
原子能技术 | 302篇 |
自动化技术 | 13059篇 |
出版年
2024年 | 427篇 |
2023年 | 729篇 |
2022年 | 1170篇 |
2021年 | 1275篇 |
2020年 | 1417篇 |
2019年 | 1421篇 |
2018年 | 1272篇 |
2017年 | 1584篇 |
2016年 | 1729篇 |
2015年 | 1794篇 |
2014年 | 2346篇 |
2013年 | 3047篇 |
2012年 | 2880篇 |
2011年 | 2980篇 |
2010年 | 2273篇 |
2009年 | 2328篇 |
2008年 | 2325篇 |
2007年 | 2618篇 |
2006年 | 2099篇 |
2005年 | 1859篇 |
2004年 | 1555篇 |
2003年 | 1306篇 |
2002年 | 1136篇 |
2001年 | 996篇 |
2000年 | 847篇 |
1999年 | 703篇 |
1998年 | 521篇 |
1997年 | 518篇 |
1996年 | 397篇 |
1995年 | 360篇 |
1994年 | 291篇 |
1993年 | 236篇 |
1992年 | 200篇 |
1991年 | 186篇 |
1990年 | 163篇 |
1989年 | 121篇 |
1988年 | 83篇 |
1987年 | 64篇 |
1986年 | 40篇 |
1985年 | 32篇 |
1984年 | 45篇 |
1983年 | 44篇 |
1982年 | 32篇 |
1981年 | 31篇 |
1980年 | 26篇 |
1979年 | 11篇 |
1978年 | 11篇 |
1977年 | 14篇 |
1976年 | 7篇 |
1959年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
111.
为了更真实地仿真现实的网络世界和提高模型的适应性,研究一类具有双重时滞和非时滞耦合的复杂网络同步问题。不同于大多数研究中限定耦合矩阵满足耗散耦合条件,对耦合矩阵未添加任何限制。基于李雅普诺夫稳定性定理,结合线性矩阵不等式,利用广义模型中的等价转换和系数矩阵分解方法,引入自由矩阵,在驱动系统中设置非线性控制器,得到驱动系统与响应系统同步的充分条件。两个仿真例子选定了两个不同的拓扑结构,实验结果证明了定理的可行性和有效性。 相似文献
112.
简单介绍了带钢纵剪机组的用途及其工艺流程,描述了全数字式590P 4Q直流调速器直流系统功能,设计了590P 4Q直流调速器的供电系统和直流调速系统,利用PLC和590P 4Q调速器之间强大的通讯能力,实现了PLC和直流调速器的数字通讯,提高了纵剪机组的生产能力和效率,降低了生产成本。 相似文献
113.
Ilaria Saltarella Concetta Altamura Aurelia Lamanuzzi Benedetta Apollonio Angelo Vacca Maria Antonia Frassanito Jean-Franois Desaphy 《International journal of molecular sciences》2022,23(13)
Ion channels are pore-forming proteins that allow ions to flow across plasma membranes and intracellular organelles in both excitable and non-excitable cells. They are involved in the regulation of several biological processes (i.e., proliferation, cell volume and shape, differentiation, migration, and apoptosis). Recently, the aberrant expression of ion channels has emerged as an important step of malignant transformation, tumor progression, and drug resistance, leading to the idea of “onco-channelopathy”. Here, we review the contribution of ion channels and transporters in multiple myeloma (MM), a hematological neoplasia characterized by the expansion of tumor plasma cells (MM cells) in the bone marrow (BM). Deregulation of ion channels sustains MM progression by modulating intracellular pathways that promote MM cells’ survival, proliferation, and drug resistance. Finally, we focus on the promising role of ion channels as therapeutic targets for the treatment of MM patients in a combination strategy with currently used anti-MM drugs to improve their cytotoxic activity and reduce adverse effects. 相似文献
114.
Albena Momchilova Roumen Pankov Alexander Alexandrov Tania Markovska Stefan Pankov Plamen Krastev Galya Staneva Evgenia Vassileva Nikolai Krastev Adriana Pinkas 《International journal of molecular sciences》2022,23(14)
Multiple sclerosis (MS) is an autoimmune, inflammatory, degenerative disease of the central nervous system. Changes in lipid metabolism have been suggested to play important roles in MS pathophysiology and progression. In this work we analyzed the lipid composition and sphingolipid-catabolizing enzymes in erythrocytes and plasma from MS patients and healthy controls. We observed reduction of sphingomyelin (SM) and elevation of its products—ceramide (CER) and shingosine (SPH). These changes were supported by the detected up-regulation of the activity of acid sphingomyelinase (ASM) in MS plasma and alkaline ceramidase (ALCER) in erythrocytes from MS patients. In addition, Western blot analysis showed elevated expression of ASM, but not of ALCER. We also compared the ratios between saturated (SAT), unsaturated (UNSAT) and polyunsaturated fatty acids and suggest, based on the significant differences observed for this ratio, that the UNSAT/SAT values could serve as a marker distinguishing erythrocytes and plasma of MS from controls. In conclusion, the application of lipid analysis in the medical practice would contribute to definition of more precise diagnosis, analysis of disease progression, and evaluation of therapeutic strategies. Based on the molecular changes of blood lipids in neurodegenerative pathologies, including MS, clinical lipidomic analytical approaches could become a promising contemporary tool for personalized medicine. 相似文献
115.
本文介绍了一种基于多微处理器的主从式核物位监测系统的设计。简述了测量原理。从外部结构、硬件电路、通讯协议和软件编制几个方面详细介绍了系统设计。该系统目前在多个发电厂除尘系统得到应用,取得很好的效果。 相似文献
116.
117.
119.
This paper proposes a new object-based classification method for Polarimetric synthetic aperture radar (PolSAR) images, which considers scattering powers from an improved model-based polarimetric decomposition approach, as well as the spatial and textural features. With the decomposition, the scattering ambiguities between ori-ented buildings and vegetation are reduced. Furthermore, various contextual features are extracted from the ob ject and incorporated into the K-nearest neighbors (k-NN) based classification. To reduce the feature redundancy, a new Supervised locally linear embedding (S-LLE) dimen-sionality reduction method is introduced to map the high dimensional polarimetric signatures into the most compact low-dimensional structure for classification. Experimental results with Airborne synthetic aperture rada (AIRSAR) C-band PolSAR image demonstrate the superior perfor-mance to other methods. 相似文献
120.
双足型直线超声电机的实验研究 总被引:3,自引:0,他引:3
研制了一种新型直线超声电机,首先对其驱动机理进行了探讨,设计了电机的具体结构。其次对振子进行了频率响应实验,模态实验,实验表明电机可有效激励出所需振型。分别测定了电机的频率-速度关系、电压-速度关系、相位-速度关系。电机运行中正反两向运动灵活,工作状态稳定,速度基本与输入电压成正比,可采用调压调速;其最大无负载速度可达76 mm/s,最大输出推力2 N,达到了预期设计的目的。 相似文献