全文获取类型
收费全文 | 21656篇 |
免费 | 2176篇 |
国内免费 | 870篇 |
专业分类
电工技术 | 522篇 |
综合类 | 2964篇 |
化学工业 | 1672篇 |
金属工艺 | 1261篇 |
机械仪表 | 1218篇 |
建筑科学 | 6187篇 |
矿业工程 | 1093篇 |
能源动力 | 359篇 |
轻工业 | 979篇 |
水利工程 | 1058篇 |
石油天然气 | 862篇 |
武器工业 | 260篇 |
无线电 | 630篇 |
一般工业技术 | 2487篇 |
冶金工业 | 2042篇 |
原子能技术 | 91篇 |
自动化技术 | 1017篇 |
出版年
2024年 | 76篇 |
2023年 | 219篇 |
2022年 | 508篇 |
2021年 | 576篇 |
2020年 | 611篇 |
2019年 | 520篇 |
2018年 | 505篇 |
2017年 | 643篇 |
2016年 | 701篇 |
2015年 | 784篇 |
2014年 | 1282篇 |
2013年 | 1067篇 |
2012年 | 1478篇 |
2011年 | 1697篇 |
2010年 | 1355篇 |
2009年 | 1345篇 |
2008年 | 1283篇 |
2007年 | 1526篇 |
2006年 | 1456篇 |
2005年 | 1183篇 |
2004年 | 1006篇 |
2003年 | 884篇 |
2002年 | 765篇 |
2001年 | 619篇 |
2000年 | 545篇 |
1999年 | 412篇 |
1998年 | 288篇 |
1997年 | 254篇 |
1996年 | 216篇 |
1995年 | 187篇 |
1994年 | 153篇 |
1993年 | 116篇 |
1992年 | 111篇 |
1991年 | 76篇 |
1990年 | 50篇 |
1989年 | 51篇 |
1988年 | 32篇 |
1987年 | 30篇 |
1986年 | 12篇 |
1985年 | 4篇 |
1984年 | 12篇 |
1983年 | 11篇 |
1982年 | 7篇 |
1981年 | 3篇 |
1980年 | 11篇 |
1979年 | 4篇 |
1964年 | 7篇 |
1960年 | 4篇 |
1959年 | 2篇 |
1957年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
本文描述了醋酸纤维素-纤维素大孔增强超滤膜的结构特征一分离性能之间的关系。详细论述了膜材料含量和粘连剂含量及其分子量对膜结构和性能的影响。论述了不同配方铸膜液的膜,其孔径,水通量和截留率随操作压力的变化规律。实验证明这种高强度的CAC膜经多次重复使用后,其结构性能保持完好。 相似文献
82.
本文基于弹塑性分叉理论研究单向纤维增强复合材料的压缩破坏模式和压缩强度对缺陷的敏感性问题。对于常见复合材料,所得结论是:无缺陷或者小缺陷情况的破坏模式为倾斜破坏带;大缺陷情况的破坏模式为水平破坏带;形成水平破坏带的压力值小于形成倾斜破坏带的压力。 相似文献
83.
随着内窥镜检查及胸部手术的广泛开展、气管切开后金属插管的较长期使用,气管支气管肉芽肿以及良恶性肿瘤等已为常见疾病。激光治疗气管、支气管疾病在临床上已证明有效,但激光对气道粘膜的作用究竟如何尚鲜见报道。本实验应用机械刺激原理,置异物于大道某一部位,造成持续性刺激而促使该部位生长出炎性肉芽肿,然后以YAG:Nd激光照射汽化之,观察治疗后局部大体及镜下病理变化,旨在为临床激光治疗气道内阻塞性病变提供理论参考。 相似文献
84.
水环境的恶化,使水工钢闸门腐蚀加重,传统的防腐工艺保护效果下降。聚酯玻璃钢复合防腐层的水工钢闸门防腐工艺具有使用设备少,工艺简单、防腐效果好、成本低等优点,适用于在各种水环境中作各种形式的水工钢闸门防腐,效果良好。该文结合江苏省淮海农场工程施工经验,提出了水工钢闸门聚酯玻璃钢复合防腐层结构设计、施工工艺及质量标难,为今后的推广应用提供了一定的参考依据。 相似文献
85.
No authorship indicated 《Canadian Metallurgical Quarterly》2004,59(8):787
Provides the biography of Cortney S. Warren and announces that she has received the APA Psi Chi/APA Edwin B. Newman Graduate Research Award (2004) for an outstanding research paper whose findings examine the potential for ethnicity to protect against body image disturbance by moderating the relationships between awareness and internalization of a thin physical ideal and body dissatisfaction. A selected bibliography is also provided. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
86.
Unidirectional (UD) and multidirectional (MD) flax/polypropylene composites were studied. Flax with varying retting degree and boiled flax was used as reinforcement for the UD composites and unmodified and maleic acid anhydride modified polypropylene (MAA-PP) was used as matrix. Multidirectional flax/polypropylene composites were manufactured on laboratory scale and on pilot scale. They were made from needle-punched hybrid flax/PP non-wovens. Normally retted flax as well as boiled flax was used. For the specimens made on pilot scale, a third kind of flax, namely bleached flax was also studied. The influence of different process times and temperatures on the mechanical properties of the composites was analysed. Generally, the composites have adequate good mechanical properties. The unidirectional composites of boiled flax combined with MAA-PP show the best mechanical properties. Contrary to the UD composites, flax treatment did not lead to the expected property improvements for MD composites. 相似文献
87.
Service Load Effective Compression Flange Width in Fiber Reinforced Polymer Deck Systems Acting Compositely with Steel Stringers 总被引:1,自引:0,他引:1
This paper reports on the field study of a steel stringer-fiber reinforced polymer (FRP) deck composite bridge in Pennsylvania. The objective of the study is to assess the effective compression flange width in the FRP deck and floor systems when they act compositely with underlying steel girders at service conditions. The research results reported herein support the notion of employing a design approach, for both interior and exterior girders of a composite floor system, that is philosophically consistent with current practice related to steel girders acting compositely with concrete decking. It appears from the results presented herein that FRP decks and floors acting compositely with underlying steel girders exhibit an effective width that is close to the actual girder spacing for interior beams, and approximately one-half this value for exterior beams. 相似文献
88.
The paper reports the experimental investigation data for the effect that nonparallel faces of bars under impact exert on
the parameters of longitudinal and bending strain waves generated in the bars. The changes in stress magnitudes in the bar
under impact with growing angle of the impact faces offset are described.
__________
Translated from Fiziko-Tekhnicheskie Problemy Razrabotki Poleznykh Iskopaemykh, No. 6, pp. 73–78, November–December, 2006. 相似文献
89.
The local bond mechanics of glass-fiber reinforced polymer (GFRP) bars in normal strength concrete was investigated through experimental testing and analytical modeling. The experimental program was comprised of 30 direct tension pullout specimens with short anchorages. A novel test setup, specially designed so as to minimize the spurious influence of testing conditions on measured bond properties was adopted in the study. Parameters considered were the bar roughness and diameter, the size effect expressed by the constant cover to bar diameter ratio, and the external confining pressure exerted over the anchorage length by transverse externally bonded FRP sheets. Results of the study were summarized in the form of local bond-slip curves, whereby performance limit states were quantified by the amount of loaded end slip and bond strength. An analytical model of the bond stress-slip response of a GFRP bar was derived from first principles and calibrated against the test data of the present investigation. Using the calibrated model, design values for bond and slip were estimated with reference to the code limit state model for bond. 相似文献
90.
运用文献[1]所介绍的分析原理与方法,编制了强震作用下钢筋混凝土框架-剪力墙结构非线性地震反应时程分析的程序。本文介绍该程序的功能、框图,以及利用该程序计算所得到的几栋钢筋混凝土结构的非线性地震反应分析结果。算例表明,本程序计算结果可靠,能很好地用于解释震害和预测地震时结构可能发生的破坏。 相似文献