全文获取类型
收费全文 | 19778篇 |
免费 | 1887篇 |
国内免费 | 1077篇 |
专业分类
电工技术 | 562篇 |
综合类 | 1516篇 |
化学工业 | 4804篇 |
金属工艺 | 781篇 |
机械仪表 | 2106篇 |
建筑科学 | 857篇 |
矿业工程 | 399篇 |
能源动力 | 1177篇 |
轻工业 | 803篇 |
水利工程 | 389篇 |
石油天然气 | 601篇 |
武器工业 | 558篇 |
无线电 | 842篇 |
一般工业技术 | 3447篇 |
冶金工业 | 525篇 |
原子能技术 | 386篇 |
自动化技术 | 2989篇 |
出版年
2024年 | 81篇 |
2023年 | 402篇 |
2022年 | 588篇 |
2021年 | 875篇 |
2020年 | 762篇 |
2019年 | 669篇 |
2018年 | 579篇 |
2017年 | 780篇 |
2016年 | 823篇 |
2015年 | 793篇 |
2014年 | 1162篇 |
2013年 | 1399篇 |
2012年 | 1200篇 |
2011年 | 1562篇 |
2010年 | 976篇 |
2009年 | 1170篇 |
2008年 | 1081篇 |
2007年 | 1189篇 |
2006年 | 1054篇 |
2005年 | 822篇 |
2004年 | 747篇 |
2003年 | 630篇 |
2002年 | 513篇 |
2001年 | 420篇 |
2000年 | 381篇 |
1999年 | 351篇 |
1998年 | 293篇 |
1997年 | 254篇 |
1996年 | 201篇 |
1995年 | 165篇 |
1994年 | 139篇 |
1993年 | 124篇 |
1992年 | 93篇 |
1991年 | 96篇 |
1990年 | 63篇 |
1989年 | 91篇 |
1988年 | 54篇 |
1987年 | 26篇 |
1986年 | 19篇 |
1985年 | 16篇 |
1984年 | 21篇 |
1983年 | 13篇 |
1982年 | 11篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1959年 | 8篇 |
1956年 | 2篇 |
1955年 | 5篇 |
1951年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
71.
中国先进研究堆导流箱流场的数值模拟 总被引:1,自引:1,他引:0
采用目前国内普遍使用的计算流体力学 (CFD)软件PHOENICS 3 2对中国先进研究堆不同结构的导流箱的三维流场进行数值模拟计算。结果表明 :导流箱入口导流板和导流筒能显著改善导流箱入口冷却剂的流动状况 ,获得入口冷却剂沿周向均匀分流的效果 ,达到显著减缓入口冷却剂对垂直辐照孔道导管及安全棒导管直接的横向水力冲刷的设计目的 相似文献
72.
聚碳硅烷的分子量分布与可纺性研究 总被引:6,自引:1,他引:5
阐述了聚碳烷的合成及其分子量分布,讨论了高低分子含量对聚碳硅烷熔点及可纺性的影响,而且提出了分子量分布的控制标准与方法。 相似文献
73.
Directional solidification studies of gelatinized corn starch-water mixtures were undertaken in order to examine, in situ, the freezing behavior of this food model. The solidification rate was controlled by varying sample cell velocity as it moved from a 25°C hot stage to a -25°C cold stage. While freezing at cell velocities ≤7.5 μm/sec, starch granules were alternately pushed or entrapped by the advancing solid-liquid interface producing a segregated structure consisting of alternating high-starch and low-starch bands. At a cell velocity of 10 μm/sec, the frozen product was homogeneous. The relationship between the solid-liquid interface velocity and segregation behavior was quantified and compared to an existing model of particle-interface interactions. 相似文献
74.
The pumping performance of molecular drag pumps (MDP) has been investigated experimentally. The experimented MDPs are a disk-type
drag pump (DTDP), helical-type drag pump (HTDP) and compound drag pump (CDP), respectively. In the case of the DTDP, spiral
channels of a rotor are cut on both upper surface and lower surface of a rotating disk, and the corresponding stator is a
planar disk. In the case of the HTDP, the rotor has six rectangular grooves. The CDP consists with the DTDP, at lower part,
and with the HTDP, at upper part. The experiments are performed in the outlet pressure range of 0.2–533 Pa. The inlet pressure
and compression ratio are measured under the various conditions of outlet pressure and throughputs, and nitrogen is used for
the test gas. At the outlet pressure of 0.2 Pa, the ultimate pressure has been reached to 1.0 × 10−2 Pa for the HTDP, 1.3 × 10−4 Pa for the DTDP, and 3.6 × 10−5 Pa for the CDP. The maximum compression ratio of the CDP is much higher than those of the DTDP or HTDP. Consequently, the
ultimate pressure of the CDP is the lowest one. 相似文献
75.
W. Tang H.Z. Shi G. Xu B.S. Ong Z.D. Popovic J.C. Deng J. Zhao G.H. Rao 《Advanced materials (Deerfield Beach, Fla.)》2005,17(19):2307-2311
76.
前陆盆地前缘隆起是一重要油气聚集带,其特殊的构造部位及复杂的动力学演化过程决定了在该部位有多种圈闭形成和分布。塔里木盆地库车前陆盆地由三叠系、侏罗系烃源岩发育而成的成油体系中的前缘隆起——沙雅隆起区经历了海西期挤压形成雏形、印支—燕山早期挤压定型、燕山晚期—喜马拉雅中期拱张、喜马拉雅晚期挤压拗陷等构造活动阶段,圈闭形成与构造活动相关,成藏与烃源岩演化、幕式构造运动有关,因此各圈闭带的含油气性与圈闭形成期和油气运聚期的匹配有很大关系,由此划分出沙雅前缘隆起区的3级有利构造带。 相似文献
77.
Repetitive processes are a distinct class of 2D systems (i.e. information propagation in two independent directions) of both systems theoretic and applications interest. They cannot be controlled by direct extension of existing techniques from either standard (termed 1D here) or 2D systems theory. In this paper, we exploit their unique physical structure to show how two term, i.e. proportional plus integral (or PI) action, can be used to control these processes to produce desired behavior (as opposed to just stability). 相似文献
78.
G.O. Phillips S. Al-Assaf A. du Plessis 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2007,265(1):390-393
Using a mediating alkyne gas during the radiation treatment prevents the degradation of natural and synthetic polysaccharides and proteins. The product has higher viscosity and is more elastic than the original material and, therefore, gives enhanced functionality. Protein, within demineralised bone, too can be modified to give enhanced osteoinductive capacity after transplantation. Thus new functionalities can be achieved from the new products produced in food and medical products. 相似文献
79.
The distortion structure in nanocrystalline NiAl is studied using molecular dynamics simulation.The rounded grain boundaries in these nanograins are a direct source for the observed lattice distortion.The change of grain size affects directly the volume fraction of the distorted lattice in the nanograin. 相似文献
80.
《Drying Technology》2007,25(6):971-983
This article reviews developments in the simulations of spray dryer behavior, including the challenges in modeling the complex flow patterns inside the equipment, which are often highly transient and three-dimensional in nature. There appears to be considerable scope for using CFD simulations for investigating methods to reduce the rates of wall deposition and of thermal degradation for particles by modifying the air flow patterns in the chamber through small changes in the air inlet geometry. Challenges include building particle drying kinetics and reaction processes, as well as agglomeration behavior, into these simulations. The numerical simulations should be valuable supplements to pilot-scale testing, enabling more extensive and accurate optimization to be carried out than hitherto possible. New understanding of reaction processes and materials science, in combination with recent knowledge of the application of CFD to these problems, may enable new engineered powder products to be developed from the one-step spray-drying process. 相似文献