全文获取类型
收费全文 | 1851篇 |
免费 | 119篇 |
国内免费 | 59篇 |
专业分类
电工技术 | 44篇 |
综合类 | 191篇 |
化学工业 | 289篇 |
金属工艺 | 128篇 |
机械仪表 | 223篇 |
建筑科学 | 250篇 |
矿业工程 | 40篇 |
能源动力 | 42篇 |
轻工业 | 46篇 |
水利工程 | 68篇 |
石油天然气 | 34篇 |
武器工业 | 47篇 |
无线电 | 70篇 |
一般工业技术 | 303篇 |
冶金工业 | 85篇 |
原子能技术 | 9篇 |
自动化技术 | 160篇 |
出版年
2024年 | 3篇 |
2023年 | 32篇 |
2022年 | 21篇 |
2021年 | 38篇 |
2020年 | 45篇 |
2019年 | 46篇 |
2018年 | 45篇 |
2017年 | 45篇 |
2016年 | 48篇 |
2015年 | 56篇 |
2014年 | 81篇 |
2013年 | 132篇 |
2012年 | 100篇 |
2011年 | 108篇 |
2010年 | 86篇 |
2009年 | 90篇 |
2008年 | 107篇 |
2007年 | 135篇 |
2006年 | 111篇 |
2005年 | 98篇 |
2004年 | 95篇 |
2003年 | 85篇 |
2002年 | 82篇 |
2001年 | 38篇 |
2000年 | 45篇 |
1999年 | 27篇 |
1998年 | 31篇 |
1997年 | 32篇 |
1996年 | 27篇 |
1995年 | 17篇 |
1994年 | 18篇 |
1993年 | 12篇 |
1992年 | 8篇 |
1991年 | 6篇 |
1990年 | 19篇 |
1989年 | 18篇 |
1988年 | 9篇 |
1987年 | 6篇 |
1986年 | 3篇 |
1985年 | 8篇 |
1983年 | 5篇 |
1982年 | 2篇 |
1980年 | 3篇 |
1978年 | 1篇 |
1960年 | 1篇 |
1958年 | 1篇 |
1954年 | 1篇 |
1951年 | 2篇 |
排序方式: 共有2029条查询结果,搜索用时 15 毫秒
21.
边坡稳定安全系数求解格式的分类统一 总被引:5,自引:5,他引:5
根据极限平衡条分法所满足的平衡条件,将现行13种极限平衡条分法分为4大类:M类(仅考虑对选定求矩中心的力矩平衡)、VM类(考虑垂直方向力的平衡和对选定求矩中心的力矩平衡)、HV类(考虑水平方向力的平衡和垂直方向力的平衡)和HVM类(考虑所有平衡条件)。其中,M类(瑞典法)有显式解,VM类(简化Bishop法)有隐式的安全系数表达式,迭代并不困难。将现有极限平衡条分法对条问力的假定表示成统一形式,根据力和力矩的平衡,推导出十分简明的条间力递推方程和条问力矩递推方程。根据条问力递推方程,建立了传统意义上(保持原有方法所满足的平衡条件、对条间力的假定和未知量小变)基于力平衡(HV类)的安全系数统一求解格式。根据条间力递推方程和条问力矩递推方程,通过Newton-Raphson法建立了传统意义上基于严格半衡(HVM类)的安全系数统一求解格式。不但便于程序的编写,而且有利于不同方法优缺点的比较和理解。 相似文献
22.
Creep behaviour of geosynthetics 总被引:9,自引:0,他引:9
Empirical results dealing with rheological properties of some geosynthetics are presented. Creep tests performed on some Polish-made geotextiles are described and discussed within the framework of the standard linear solid (SLS) model. It is shown that the SLS model described by three parameters can serve as a useful low resolution approximation for a range of geosynthetics, for low stress levels which exclude secondary and tertiary creep. The parameters of the SLS model were determined by curve fitting for three types of Polish geotextiles as well as for some other geosynthetics. The problems of creep under increasing load and creep after partial unloading are discussed. Two modified rheological models of geotextiles, which take into account the plastic strains, are proposed. 相似文献
23.
24.
硬岩掘进机盘型滚刀回转破岩仿真研究 总被引:2,自引:0,他引:2
硬岩掘进机上盘形滚刀在实际破岩过程中既随刀盘公转,又绕自身轴线自转,是一个复杂的运动过程。滚刀在破岩过程中受到的作用力的计算是进行刀盘设计和推进系统设计的重要依据。针对硬岩掘进机盘型滚刀破岩过程分析和计算的复杂性,应用ABAQUS软件中多体动力学原理建立滚刀组合回转破岩的有限元模型,模型中采用无限元网格施加无反射边界条件,消除模型大小对仿真结果的影响。通过分析计算滚刀破岩中所受的作用力,研究了滚刀回转破岩的刀间距及相位差。仿真结果表明,对于所选用的岩石类型,其最优刀间距为60mm,此时滚刀受到的滚动力最小,破岩质量最大,破岩比能最小;相邻滚刀的最佳相位差为120°,破岩质量最大,比能最小。研究为硬岩掘进机上刀盘刀具的布局研究奠定了基础。 相似文献
25.
26.
Anupam Aich Weichun Pan Peter G. Vekilov 《American Institute of Chemical Engineers》2015,61(9):2861-2870
For insights into the mechanisms of heme action on the rate of sickle cell hemoglobin polymerization, we determine the erythrocytic concentration of free heme using a novel method based on enzymatic catalysis and luminescence. We find in sickle cell patients 44 ± 10 µM, in sickle trait individuals, 33 ± 4 µM, and in healthy adults, 21 ± 2 µM. We test the applicability of two mechanisms of heme action: a kinetic one, whereby heme aggregates serve as heterogeneous nucleation centers, and a thermodynamic pathway, in which free heme enhances the attraction between sickle hemoglobin (HbS) molecules in solution. We show that the latter mechanism exclusively operates. The enhanced attraction leads to increase of the total volume of a population of dense liquid clusters by about two orders of magnitude. As the dense liquid clusters serve as locations and precursors to the formation of the HbS polymer nuclei, their increased volume directly leads to faster polymer nucleation. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2861–2870, 2015 相似文献
27.
Examination of the Causes of Instability of Soy Protein Isolate During Storage Through Probing of the Heat‐Induced Aggregation 下载免费PDF全文
Feng‐Xian Guo Youling L. Xiong Fang Qin Hua‐Jun Jian Xiao‐Lin Huang Jie Chen 《Journal of the American Oil Chemists' Society》2015,92(8):1075-1084
This study investigated the mechanism of instability of soy protein isolate (SPI) as influenced by thermal aggregation during SPI preparation. Samples with different degrees of aggregation but similar protein solubility were prepared by heating native SPI (5 % w/v) at 80 or 90 °C for different times before spray‐drying. The samples were then stored at 37 °C for up to 12 weeks and analyzed periodically by atomic force microscopy, gel permeation chromatography, and SDS–PAGE. All SPI samples underwent remarkable protein solubility decreases during the first 8 weeks of storage. The rates of solubility loss were positively correlated with the amounts and/or sizes of soluble aggregates contained in the initial samples (time zero), suggesting their nucleation and activation effects. Solubility tests in SDS–urea solutions and disulfide analysis indicated that non‐covalent interactions were the main driving forces for protein storage instability. Conversely, disulfide bonds and protein carbonyls were abundant in soluble aggregates, and their content increased markedly during storage. This effect suggested that covalent linkages acted as blockers for hydrophobic aggregation. 相似文献
28.
Yuefei Wang Renliang Huang Wei Qi Yanyan Xie Mengfan Wang Rongxin Su Zhimin He 《Small (Weinheim an der Bergstrasse, Germany)》2015,11(24):2893-2902
The wetting and drying of drops on flexible fibers occurs ubiquitously in nature, and the capillary force underlying this phenomenon has motivated our great interest in learning how to direct supramolecular self‐assembly. Here, the hierarchical co‐assembly of two aromatic peptides, diphenylalanine (FF) and ferrocene‐diphenylalanine (Fc‐FF), is reported via sequential, combinatorial assembly. The resulting dandelion‐like microstructures have highly complex architectures, where FF microtube arrays serve as the scapes and the Fc‐FF nanofibers serve as the flower heads. Homogeneous FF microtubes with diameters tailored between 1 and 9 μm and wall thickness ranging from 70 to 950 nm are initially formed by controlling the degree of supersaturation of the FF and the water content. Once the FF microtubes are formed, the growth of the dandelion‐like microstructures is then driven by the capillary force, derived from the wetting and drying of the Fc‐FF solution on the FF microtubes. This simple and ingenious strategy offers many opportunities to develop new and creative methods for controlling the hierarchical self‐assembly of peptides and thus building highly complex nano and microstructures. 相似文献
29.
随着城市地铁规模不断扩大,地铁隧道临近区域经常会发生地面堆载的现象。地面堆载会引起隧道发生一定的纵向和横向变形,当地面堆载过大时甚至会导致地铁隧道衬砌管片发生破坏、管片之间接口处缝隙增大、连接管片之间的螺栓发生失效等现象。根据现有研究成果,到目前为止学者们关于地面堆载对隧道影响的内容可以总结成以下四个部分:纵向受力和变形,横向受力和变形,安全性评估,加固方法与效果研究。文中将关于地面堆载对临近地铁隧道的研究成果按照研究内容进行分类,并提出了现有研究的不足之处和需要进一步深入研究的方向。 相似文献
30.
A. L. Eberle B. H. Dickerson P. G. Reinhall T. L. Daniel 《Journal of the Royal Society Interface》2015,12(104)
Insects perform fast rotational manoeuvres during flight. While two insect orders use flapping halteres (specialized organs evolved from wings) to detect body dynamics, it is unknown how other insects detect rotational motions. Like halteres, insect wings experience gyroscopic forces when they are flapped and rotated and recent evidence suggests that wings might indeed mediate reflexes to body rotations. But, can gyroscopic forces be detected using only changes in the structural dynamics of a flapping, flexing insect wing? We built computational and robotic models to rotate a flapping wing about an axis orthogonal to flapping. We recorded high-speed video of the model wing, which had a flexural stiffness similar to the wing of the Manduca sexta hawkmoth, while flapping it at the wingbeat frequency of Manduca (25 Hz). We compared the three-dimensional structural dynamics of the wing with and without a 3 Hz, 10° rotation about the yaw axis. Our computational model revealed that body rotation induces a new dynamic mode: torsion. We verified our result by measuring wing tip displacement, shear strain and normal strain of the robotic wing. The strains we observed could stimulate an insect''s mechanoreceptors and trigger reflexive responses to body rotations. 相似文献