全文获取类型
收费全文 | 354744篇 |
免费 | 42259篇 |
国内免费 | 30210篇 |
专业分类
电工技术 | 32572篇 |
综合类 | 39667篇 |
化学工业 | 42329篇 |
金属工艺 | 25574篇 |
机械仪表 | 25181篇 |
建筑科学 | 26409篇 |
矿业工程 | 16103篇 |
能源动力 | 9133篇 |
轻工业 | 41664篇 |
水利工程 | 12257篇 |
石油天然气 | 12418篇 |
武器工业 | 5501篇 |
无线电 | 36321篇 |
一般工业技术 | 27921篇 |
冶金工业 | 15596篇 |
原子能技术 | 6249篇 |
自动化技术 | 52318篇 |
出版年
2024年 | 2328篇 |
2023年 | 6120篇 |
2022年 | 14442篇 |
2021年 | 18464篇 |
2020年 | 12982篇 |
2019年 | 8910篇 |
2018年 | 9521篇 |
2017年 | 11373篇 |
2016年 | 9966篇 |
2015年 | 16086篇 |
2014年 | 20205篇 |
2013年 | 23787篇 |
2012年 | 29961篇 |
2011年 | 31457篇 |
2010年 | 29679篇 |
2009年 | 28173篇 |
2008年 | 29504篇 |
2007年 | 28599篇 |
2006年 | 24522篇 |
2005年 | 20149篇 |
2004年 | 14293篇 |
2003年 | 9244篇 |
2002年 | 8470篇 |
2001年 | 7584篇 |
2000年 | 6061篇 |
1999年 | 2136篇 |
1998年 | 507篇 |
1997年 | 383篇 |
1996年 | 344篇 |
1995年 | 234篇 |
1994年 | 178篇 |
1993年 | 199篇 |
1992年 | 180篇 |
1991年 | 133篇 |
1990年 | 144篇 |
1989年 | 136篇 |
1988年 | 81篇 |
1987年 | 67篇 |
1986年 | 53篇 |
1985年 | 36篇 |
1984年 | 32篇 |
1983年 | 38篇 |
1982年 | 41篇 |
1981年 | 63篇 |
1980年 | 102篇 |
1979年 | 68篇 |
1965年 | 8篇 |
1959年 | 70篇 |
1957年 | 5篇 |
1951年 | 74篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Basins with various mineral resources coexisting and enriching often occupy an important strategic position. The exploration of various mineral resources is repetitive at present due to unshared data and imperfect management mechanism. This situation greatly increases the cost of energy exploitation in the country. Traditional data-sharing mode has several disadvantages, such as high cost, difficulty in confirming the right of data, and lack of incentive mechanism, which make achieving real data sharing difficult. In this paper, we propose a data-sharing mechanism based on blockchain and provide implementation suggestions and technical key points. Compared with traditional data-sharing methods, the proposed data-sharing mechanism can realize data sharing, ensure data quality, and protect intellectual property. Moreover, key points in the construction are stated in the case study section to verify the feasibility of the data-sharing system based on blockchain proposed in this paper. 相似文献
22.
23.
刘潜 《江汉石油职工大学学报》2015,28(1):102-103
本文介绍了江汉油田员工考勤管理工作的基本情况,梳理和分析了当前员工考勤管理中存在的问题及原因,提出了要进一步细化和完善管理制度,强化过程监督和责任落实,逐步推进考勤公示制度化等措施。 相似文献
24.
煤电平均供电煤耗作为评价能源系统效率的指标已在行业内广泛应用。但该项指标无法很好地反映一个国家、地区的用电结构与用电能耗水平。为此,参照行业内普遍采用的火电厂发电煤耗和供电煤耗指标,定义“综合用电煤耗”,即用户每用1 kW?h电“消耗”的标准煤量(单位:g/(kW?h))。在此基础上,提出“综合发电煤耗”与“综合供电煤耗”的概念,形成完整的指标评价体系。对近年典型省份指标值的研究表明,该指标体系能够很好地反映供给侧国家、省区或企业的发电结构与电能生产能耗水平。这一指标体系能够为正确理解和计算用电、输电与电能替代项目的化石能源消耗量及其排放量提供依据。 相似文献
25.
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
26.
27.
We propose an analytical model to evaluate the lightpath blocking performance for a single ROADM node with intra-node add/drop contention,in which the number of lightpaths that can be added/dropped with the same wavelength is limited by the add/drop contention factor.Different models of traffic load per nodal degree are considered to validate the effectiveness of the analytical model.The simulation results show that the proposed analytical model is effective in predicting the performance for different values of add/drop contention factor C and for variable offered loads at the node.The add/drop contention factor shows an important impact on the lightpath blocking performance and properly raising the contention factor can significantly improve the lightpath blocking performance.When the add/drop contention factor C exceeds a certain level,the performance of a ROADM with intra-node contention is close to that of a contentionless ROADM. 相似文献
28.
In this work,the ionospheric variability is analyzed by applying the wavelet decomposition technique to the noontime fo F2,F10.7,interplanetary magnetic field(IMF)Bz,Ap,and lower thermospheric temperature at pressure of 10?4 h Pa in 2002.Results show that the variance of periodic oscillations in the ionosphere is largest in the 2–4-day period and declines with the increase of the period.The maximum variance of the periodic oscillations in solar irradiation is in the 16–32-day period.For geomagnetic activities,most of the variance is about equally distributed on intervals of periods shorter than 32 days.Variance distributions of IMF Bz and lower thermospheric temperature are similar to those of the ionosphere.They show the maximum in the 2–4-day period and decline with the increase of the period.By analyzing the distributions of the variances,the potential connections between the ionosphere and the external sources are discussed. 相似文献
29.
In the early design stage, automotive modeling should both meet the requirements of aesthetics and engineering. Therefore, a vehicle CAD (computer aided design) model that can be easily adjusted by feedbacks is necessary. Based on CE-Bézier surface, this paper presents a set of algorithms for parametric segmentation and fairing surface generation in a car model. This model is defined by a simplified automotive template and relevant control points, shape parameters and segmentation parameters, which can be modified to alter the car form efficiently. With this model and the corresponding adjustment method, more than fifty various vehicle models are established in this research according to different parameters. And two methods for calculating similarity index between car models are constructed, which are suitable for brand design trend analysis and modelling design decisionmaking. 相似文献
30.
目的: 探讨自身免疫性溶血性贫血(AIHA)患者外周血中调节性B细胞(Bregs)的表达及其在该病发病中的意义。方法:选择16例自身免疫性溶血性贫血患者和14例健康志愿者为研究对象,用流式细胞术分析外周血CD19+IL-10+调节性B细胞及CD19+CD24hiCD27+调节性B细胞的表达;ELISA方法检测培养上清液中IL-10的水平。结果:自身免疫性溶血性贫血患者外周血中CD19+IL-10+调节性B细胞、CD19+CD24hiCD27+调节性B细胞的表达分别为(1.27±0.39)%、(9.85±2.18)%,健康志愿者组分别为(2.92±0.71)%、(26.47±4.31)%,两组比较差异有统计学意义(P<0.05);自身免疫性溶血性贫血患者细胞培养上清中IL-10的水平低于健康志愿者组(P<0.05)。结论:自身免疫性溶血性贫血患者外周血中CD19+IL-10+调节性B细胞及CD19+CD24hiCD27+调节性B细胞比例降低,提示调节性B细胞可能参与自身免疫性溶血性贫血的发病过程。 相似文献