全文获取类型
收费全文 | 228812篇 |
免费 | 17451篇 |
国内免费 | 9134篇 |
专业分类
电工技术 | 12453篇 |
技术理论 | 24篇 |
综合类 | 14144篇 |
化学工业 | 38778篇 |
金属工艺 | 13142篇 |
机械仪表 | 14516篇 |
建筑科学 | 17561篇 |
矿业工程 | 7499篇 |
能源动力 | 6421篇 |
轻工业 | 13441篇 |
水利工程 | 3585篇 |
石油天然气 | 16616篇 |
武器工业 | 1647篇 |
无线电 | 25121篇 |
一般工业技术 | 27330篇 |
冶金工业 | 12803篇 |
原子能技术 | 2247篇 |
自动化技术 | 28069篇 |
出版年
2024年 | 993篇 |
2023年 | 3800篇 |
2022年 | 6479篇 |
2021年 | 9101篇 |
2020年 | 7077篇 |
2019年 | 6009篇 |
2018年 | 6729篇 |
2017年 | 7534篇 |
2016年 | 6746篇 |
2015年 | 8855篇 |
2014年 | 11243篇 |
2013年 | 13268篇 |
2012年 | 14205篇 |
2011年 | 15445篇 |
2010年 | 13416篇 |
2009年 | 12679篇 |
2008年 | 12342篇 |
2007年 | 11844篇 |
2006年 | 12337篇 |
2005年 | 10745篇 |
2004年 | 7258篇 |
2003年 | 6223篇 |
2002年 | 5460篇 |
2001年 | 4884篇 |
2000年 | 5431篇 |
1999年 | 6435篇 |
1998年 | 5433篇 |
1997年 | 4451篇 |
1996年 | 4187篇 |
1995年 | 3498篇 |
1994年 | 2811篇 |
1993年 | 1964篇 |
1992年 | 1536篇 |
1991年 | 1226篇 |
1990年 | 933篇 |
1989年 | 740篇 |
1988年 | 537篇 |
1987年 | 336篇 |
1986年 | 278篇 |
1985年 | 196篇 |
1984年 | 139篇 |
1983年 | 114篇 |
1982年 | 124篇 |
1981年 | 98篇 |
1980年 | 70篇 |
1979年 | 36篇 |
1978年 | 26篇 |
1977年 | 20篇 |
1976年 | 35篇 |
1973年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
热浸镀铝护栏的生产通过除油→除锈→烘干→热浸镀→精整等过程完成,最佳热浸镀温度为730~750℃,保温时间3~8min,护栏提升速度1m/s 相似文献
62.
We studied 722 reexcision scars of benign and malignant lesions (except melanocytic lesions) excised over a 24-month period. The formalin-fixed, paraffin-embedded tissue sections were examined histologically and immunohistochemically. The histological features of melanocytic hyperplasia were present in 59 cases (8%), 56 from the sun-exposed skin of the face and neck and three from the trunk [p < 0.00001]. The most common sites were the nose and lower eyelids, but the forehead was also frequently involved. Of the 59 patients, 41 were women (p < 0.0001). Basal cell carcinoma was the most frequent original lesion in both sexes (80%). No melanocytic hyperplasia was found in 663 cases (298 on the trunk and extremities and 365 on the head and neck). We have seen this reaction pattern following reexcision of melanocytic lesions as well. Thus, interpreting reexcision margins when lentigo maligna or similar lesions are reexcised may be fraught with difficulty. It is important for pathologists and dermatopathologists to recognize this phenomenon because histologically the presence of increased numbers of large melanocytes could be misinterpreted as melanoma in situ. 相似文献
63.
基于i860的存储器子系统设计 总被引:1,自引:0,他引:1
微处理机系统中的存储器子系统设计对整个系统性能的高低有重要的影响,尤其当微处理器的主频越来越高时。本文结合实际例子,给出了一个基于i860处理器(40MHz)的主存设计方案,讨论了实际中需仔细考虑的因素。该设计可为其它高性能RISC系统设计提供参考。 相似文献
64.
天津钢管公司DRC直接还原厂将采用英国戴维国际工程公司的DRC煤基直接还原技术,以铁矿石、煤、石灰石为原燃料,用回转窑来生产直接还原铁(DRI)。该厂将由两条回转窑生产线组成,每条生产线的生产能力为15万tDRI/年,回转窑规格为φ5.0m×80m。工厂生产主线将采用计算机集散控制系统(DCS)以实现对生产过程的自动控制。 相似文献
65.
在语音时域挑选剩余可懂度低的可用置换集合,置换集合是语音TDS系统中不可缺少的重要环节,本文给出了可用置换选取的条件、客观评价标准和方法。 相似文献
66.
Porous silica glass was prepared by sol-gel process from tetraethoxysilane (TEOS). The effects of solvents (water, ethanol), drying condition, heat treatment temperature on specific surface area and pore size distribution of porous silica were investigated. Gelation process accelerates with an increase of H2O content, while retards with the increase of ethanol amount. Structure changes during heat treatment were studied by means of DTA, XRD. TEM micrographs show that the gel particles shrink after heated at 500°C, thus the average pore size decreases. 相似文献
67.
A finite element formulation and the solution of a set of nonlinear coupled heat and mass transfer equations for a two-phase system with a moving evaporation interface is presented. The interface condition takes into account the moisture transfer balance at the moving boundary. The finite element results were compared with existing results for a single phase system for model validation. In the two-phase system, the movement of evaporation front has an appreciable effect on the temperature and moisture distribution inside the porous medium during drying. The effect of the nondimensional heat of vapourization parameter γ on the evaporation front, temperature and moisture distribution in porous medium was studied. The higher the value of γ, the slower is the movement of the evaporation front. The temperature decreased and the moisture content increased as the nondimensional vapourization parameter γ increased. This model has potential applications in studying the heat and mass transfer characteristics in food and biomaterials. 相似文献
68.
S. K. Liu L. Yang D. G. Zhu J. Zhang 《Metallurgical and Materials Transactions A》1994,25(9):1991-2000
A series of Fe-C-X and Fe-C-X1-X2 alloys in which X, X1 and X2 either raise or depress the activity of C iny were investigated by autodilatometer, optical microscopy, and transmission electron microscopy (TEM) to reveal the relations
among the chemical composition, transformation kinetics, and morphology of ferrite plates. The incubation time of austenite
decomposition at the nose temperature in the time-temperature-transformation (TTT) diagrams, the concentration of C in y in
contact with theα/gg boundary, and the growth rate of ferrite were evaluated to estimate the magnitude of the solute drag-like
effect (SDLE) for the different alloying elements used. All the results are consistent qualitatively with the SDLE hypothesis.
This article is based on a presentation made at the Pacific Rim Conference on the “Roles of Shear and Diffusion in the Formation
of Plate-Shaped Transformation Products,” held December 18-22, 1992, in Kona, Hawaii, under the auspices of ASM INTERNATIONAL’S
Phase Transformations Committee. 相似文献
69.
Wireless ATM networks require efficient mobility management to cope with frequent mobile handoff and rerouting of connections. Although much attention has been given in the literature to network architecture design to support wide-area mobility in public ATM networks, little has been done to the important issue of user mobility estimation and prediction to improve the connection reliability and bandwidth efficiency of the underlying system architecture. This paper treats the problem by developing a hierarchical user mobility model that closely represents the movement behavior of a mobile user, and that, when used with appropriate pattern matching and Kalman filtering techniques, yields an accurate location prediction algorithm, HLP, or hierarchical location prediction, which provides necessary information for advance resource reservation and advance optimal route establishment in wireless ATM networks 相似文献
70.
The feasibility of the anodic protection of titanium evaporators in Al2(SO4)3 solution was studied by the measurement of polarization curves, weight loss, solubility of passive film and AC impedance. The protection parameters and efficiency were determined. In addition, the practical technology of anodic protection was studied by screening reference electrodes and auxiliary cathodes. Throwing power was also measured. Four rows of tube-type evaporators of titanium have been anodically protected in situ. Field tests lasting more than one year show satisfactory results. 相似文献