全文获取类型
收费全文 | 98261篇 |
免费 | 12072篇 |
国内免费 | 7895篇 |
专业分类
电工技术 | 10258篇 |
技术理论 | 4篇 |
综合类 | 10732篇 |
化学工业 | 7602篇 |
金属工艺 | 4453篇 |
机械仪表 | 8374篇 |
建筑科学 | 16672篇 |
矿业工程 | 3984篇 |
能源动力 | 3118篇 |
轻工业 | 3708篇 |
水利工程 | 4843篇 |
石油天然气 | 5225篇 |
武器工业 | 2261篇 |
无线电 | 7628篇 |
一般工业技术 | 9408篇 |
冶金工业 | 3072篇 |
原子能技术 | 829篇 |
自动化技术 | 16057篇 |
出版年
2024年 | 322篇 |
2023年 | 1369篇 |
2022年 | 2656篇 |
2021年 | 3144篇 |
2020年 | 3516篇 |
2019年 | 2784篇 |
2018年 | 2726篇 |
2017年 | 3525篇 |
2016年 | 4024篇 |
2015年 | 4252篇 |
2014年 | 6345篇 |
2013年 | 6016篇 |
2012年 | 7929篇 |
2011年 | 7984篇 |
2010年 | 6173篇 |
2009年 | 6131篇 |
2008年 | 5724篇 |
2007年 | 6889篇 |
2006年 | 6112篇 |
2005年 | 5227篇 |
2004年 | 4261篇 |
2003年 | 3525篇 |
2002年 | 2973篇 |
2001年 | 2607篇 |
2000年 | 2205篇 |
1999年 | 1764篇 |
1998年 | 1444篇 |
1997年 | 1179篇 |
1996年 | 1063篇 |
1995年 | 891篇 |
1994年 | 704篇 |
1993年 | 517篇 |
1992年 | 432篇 |
1991年 | 296篇 |
1990年 | 281篇 |
1989年 | 236篇 |
1988年 | 152篇 |
1987年 | 84篇 |
1986年 | 63篇 |
1985年 | 49篇 |
1984年 | 55篇 |
1983年 | 35篇 |
1981年 | 31篇 |
1980年 | 82篇 |
1979年 | 61篇 |
1965年 | 27篇 |
1964年 | 34篇 |
1959年 | 36篇 |
1956年 | 29篇 |
1955年 | 36篇 |
排序方式: 共有10000条查询结果,搜索用时 421 毫秒
31.
对射频电缆幅相稳定性进行了介绍,阐述了射频测试电缆相位和幅度变化的因素,并详细分析了射频电缆相位性能以及幅度性能的不同测试方法,最后通过实测数据的展示,总结说明了在日常测试中该如何正确使用测试电缆。 相似文献
32.
Journal of Computer Science and Technology - DOACROSS loops are significant parts in many important scientific and engineering applications, which are generally exploited pipeline/wave-front... 相似文献
33.
Miroslav Kárný Marko Ruman 《International Journal of Adaptive Control and Signal Processing》2021,35(5):660-675
Any knowledge extraction relies (possibly implicitly) on a hypothesis about the modelled-data dependence. The extracted knowledge ultimately serves to a decision-making (DM). DM always faces uncertainty and this makes probabilistic modelling adequate. The inspected black-box modeling deals with “universal” approximators of the relevant probabilistic model. Finite mixtures with components in the exponential family are often exploited. Their attractiveness stems from their flexibility, the cluster interpretability of components and the existence of algorithms for processing high-dimensional data streams. They are even used in dynamic cases with mutually dependent data records while regression and auto-regression mixture components serve to the dependence modeling. These dynamic models, however, mostly assume data-independent component weights, that is, memoryless transitions between dynamic mixture components. Such mixtures are not universal approximators of dynamic probabilistic models. Formally, this follows from the fact that the set of finite probabilistic mixtures is not closed with respect to the conditioning, which is the key estimation and predictive operation. The paper overcomes this drawback by using ratios of finite mixtures as universally approximating dynamic parametric models. The paper motivates them, elaborates their approximate Bayesian recursive estimation and reveals their application potential. 相似文献
34.
针对气藏型储气库注采井注采过程中储层物性参数影响因素不明确、注采能力不对称的问题。基于相国寺储气库井下连续油管试井测试结果,提出储气库注气期“温降效应”、“变表皮效应”的概念,分析了储气库注采过程中温降效应、变表皮效应以及储层应力敏感对注采的影响。通过气藏型储气库注气期试井分析技术,研究各因素在试井曲线上的响应特征以及对试井解释参数的影响。结果表明:①相对于采气期试井测试,注气期测试得到的储层物性参数具有同样的参考价值;②储气库温降效应对于试井解释结果的影响可忽略不计,而在不同注采运行周期内,变表皮效应以及应力敏感效应影响差异较大;③编制储气库注采运行方案时应充分考虑变表皮效应与应力敏感的影响,在不同注采运行周期内开展试井测试获取准确的储层参数值。研究成果为储气库试井测试与解释提供了重要的研究依据和理论指导。 相似文献
35.
仪器仪表产品的脉冲耐压试验是产品型式试验、例行试验中的基本内容。通过对GB4793.1标准的整理,归纳了仪器仪表产品的脉冲耐压试验要求。通过对试验方法和设备特性的梳理,总结了特性参数,并介绍了应对脉冲耐压试验可采取的保护器件的类别及选用方法。 相似文献
36.
37.
《Geotextiles and Geomembranes》2021,49(5):1256-1269
This study investigates the seismic performance of geosynthetic-reinforced modular block retaining walls backfilled with cohesive, fine grained clay-sand soil mixture. Shaking table tests were performed for three ½ scaled (wall height 190 cm) and ¼ scaled model walls to investigate the effects of backfill type, the influence of reinforcement length and reinforcement stiffness effects. The El Centro and Kobe earthquake records of varying amplitudes were used as base acceleration. Displacement of the front wall, accelerations at different locations, strains on the reinforcements, and the visual observations of the facing and the backfill surface were used to evaluate the seismic performance of model walls. The model walls were subjected to rigorous shaking and the walls did not exhibit any stability problems or signs of impending failure. The maximum deformations observed on the models with cohesive backfill was less than half of the deformation of the sand model. The load transfers between the geogrid and cohesive soil was comparable to that of sand and hence the needed reinforcement length was similar as well. As a result; the model walls with cohesive backfills performed within acceptable limits under seismic loading conditions when compared with granular backfilled counterparts. 相似文献
38.
Zhuang CHENG Jianfeng WANG Matthew Richard COOP Guanlin YE 《Frontiers of Structural and Civil Engineering》2020,14(2):357
The development of a miniature triaxial apparatus is presented. In conjunction with an X-ray micro-tomography (termed as X-ray μCT hereafter) facility and advanced image processing techniques, this apparatus can be used for in situ investigation of the micro-scale mechanical behavior of granular soils under shear. The apparatus allows for triaxial testing of a miniature dry sample with a size of (diameter height). In situ triaxial testing of a 0.4–0.8 mm Leighton Buzzard sand (LBS) under a constant confining pressure of 500 kPa is presented. The evolutions of local porosities (i.e., the porosities of regions associated with individual particles), particle kinematics (i.e., particle translation and particle rotation) of the sample during the shear are quantitatively studied using image processing and analysis techniques. Meanwhile, a novel method is presented to quantify the volumetric strain distribution of the sample based on the results of local porosities and particle tracking. It is found that the sample, with nearly homogenous initial local porosities, starts to exhibit obvious inhomogeneity of local porosities and localization of particle kinematics and volumetric strain around the peak of deviatoric stress. In the post-peak shear stage, large local porosities and volumetric dilation mainly occur in a localized band. The developed triaxial apparatus, in its combined use of X-ray μCT imaging techniques, is a powerful tool to investigate the micro-scale mechanical behavior of granular soils. 相似文献
39.
为提高飞机起落架载荷实测精度,以支柱式起落架结构为研究对象,探讨处理其载荷标定数据的工程方法。首先,对实际受载情况和单向加载工况标定数据的分析,挖掘出三向载荷、缓冲支柱压缩行程与应变码值间的数学关系,将预测的数学关系代入到多向工况的标定数据中,验证了它们的准确性;其次,根据两种标定数据回归方法,提出了对应使用的支柱式起落架载荷-应变标定方程的数学模型;最后,将两种标定方程代回到标定数据中,计算起落架三向载荷,所有反算载荷的误差均在可控范围内,表明标定方程满足精度要求。将标定方程代入实测数据中,实测曲线符合变化规律。该处理方法的应用能有力提高支柱式起落架的起飞-着陆载荷实测和载荷谱编制的准确度。 相似文献
40.
Mingchang Lin Yufei Zhang Guosong Chen Ming Jiang 《Small (Weinheim an der Bergstrasse, Germany)》2015,11(45):6065-6070
Glyco‐mimicking nanoparticles (glyco‐NPs) with Förster resonance energy transfer (FRET) donor and acceptor groups formed via dynamic covalent bond of benzoboroxole and sugar from two complementary polymers are prepared. The glyco‐NPs are proved to be quite stable under physiological conditions but sensitive to pH. So the glyco‐NPs can be internalized by dendritic cells with integrity and nontoxicity and then dissociate within the acidic organelles. This particle dissociation is directly observed and visualized in vitro, for the first time via the FRET measurements and fluorescent microscopy. This feature makes controlled release of drug or protein by glyco‐NPs possible, i.e., when model antigen Ovalbumin is loaded in the glyco‐NPs, the released Ovalbumin in dendritic cells stimulates T cells more efficiently than the free Ovalbumin itself as a result of the enhanced antigen processing and presentation. Thus, the results enlighten a bright future of the glyco‐NPs in immunotherapy. 相似文献