全文获取类型
收费全文 | 139180篇 |
免费 | 13670篇 |
国内免费 | 8620篇 |
专业分类
电工技术 | 10259篇 |
技术理论 | 6篇 |
综合类 | 10915篇 |
化学工业 | 20354篇 |
金属工艺 | 8613篇 |
机械仪表 | 9379篇 |
建筑科学 | 11102篇 |
矿业工程 | 4382篇 |
能源动力 | 4201篇 |
轻工业 | 9660篇 |
水利工程 | 3337篇 |
石油天然气 | 7156篇 |
武器工业 | 1652篇 |
无线电 | 16893篇 |
一般工业技术 | 14977篇 |
冶金工业 | 5586篇 |
原子能技术 | 1918篇 |
自动化技术 | 21080篇 |
出版年
2024年 | 667篇 |
2023年 | 2107篇 |
2022年 | 4144篇 |
2021年 | 5888篇 |
2020年 | 4365篇 |
2019年 | 3519篇 |
2018年 | 3924篇 |
2017年 | 4466篇 |
2016年 | 4031篇 |
2015年 | 5861篇 |
2014年 | 7518篇 |
2013年 | 8615篇 |
2012年 | 10138篇 |
2011年 | 11101篇 |
2010年 | 10292篇 |
2009年 | 9543篇 |
2008年 | 9747篇 |
2007年 | 9257篇 |
2006年 | 8706篇 |
2005年 | 7063篇 |
2004年 | 5083篇 |
2003年 | 4172篇 |
2002年 | 4059篇 |
2001年 | 3455篇 |
2000年 | 2881篇 |
1999年 | 2431篇 |
1998年 | 1627篇 |
1997年 | 1340篇 |
1996年 | 1165篇 |
1995年 | 967篇 |
1994年 | 778篇 |
1993年 | 560篇 |
1992年 | 435篇 |
1991年 | 333篇 |
1990年 | 244篇 |
1989年 | 211篇 |
1988年 | 149篇 |
1987年 | 108篇 |
1986年 | 99篇 |
1985年 | 57篇 |
1984年 | 50篇 |
1983年 | 54篇 |
1982年 | 39篇 |
1981年 | 41篇 |
1980年 | 36篇 |
1979年 | 20篇 |
1978年 | 15篇 |
1977年 | 19篇 |
1959年 | 19篇 |
1951年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
This paper is concerned with a traction-based Completed Adjoint Double Layer Boundary Element Method to solve for the surface traction of a system of rigid particles embedded in an elastic matrix. The main feature of the method is a single layer representation of the displacement field, which leads to a system of second-kind integral equations for the traction field, the extreme eigenvalue of which could be deflated, allowing iterative solution strategies to be effectively applied. The method is therefore most suitable for large-scale simulations of particulate solids. The method is benchmarked against some known analytic solutions, including the difficult stress singularity problems at sharp edges. The effectiveness of the method in dealing with a large number of inclusions is also demonstrated with an elongational deformation problem involving up to 25 inclusions.Research supported by the Australian Research Council (to NP-T and X-JF) and the National Natural Science Foundation of China (X-JF). 相似文献
72.
关于项目管理中施工进度控制的研究 总被引:5,自引:1,他引:4
阐述了项目管理中施工进度控制的地位与作用,分析了影响工程进度的因素,提出项目进度控制需做好的工作,以提高进度控制水平,确保合同工期的实现。 相似文献
73.
74.
75.
Follicular dendritic cell tumour of the liver is a recently recognized entity. To date, only two cases have been described, both in the pathology literature. Histologically, it resembles an inflammatory pseudotumour and immunohistochemical and ultrastructural studies are required for its diagnosis. The ultrasound, computed tomography and angiographic features of two cases of follicular dendritic cell tumour of the liver are described in detail. One of the patients had multiple recurrences of this tumour. The imaging features are very similar to those of hepatocellular carcinoma. As follicular dendritic cell tumour is considered to be of low-grade malignant potential, in contrast to the dismal prognosis for hepatocellular carcinoma, it is important to be able to accurately distinguish between the two types of tumour prior to initiating definitive therapy. 相似文献
76.
A new minimum zone method for evaluating flatness errors 总被引:1,自引:0,他引:1
A new minimum zone method for flatnes error analyis is proposed in this article. Based on the criteria for the minimum zone solution and strict rules for data exchange, a simple and rapid algorithm, called the control plane rotation scheme, is developed for the flatness analysis of a flat surface. Experimental work was performed, and some examples are given in terms of the minimum zone and least-squares solutions. 相似文献
77.
粘土作为高放废物处置回填材料的可行性研究 总被引:5,自引:0,他引:5
本文以西北粘土为对象,对其压实行为、热传导、膨胀特性,以及吸附和渗透性能进行了初步研究,借以探讨西北粘土在高放废物处置中用作回填材料的可行性。试验表明,以西北粘土为基材,经过适当的热改性和吸附改性,在初始含水量约为9%,于70MPa 下成型,用作高放废物处置中的回填材料是可行的。 相似文献
78.
钇铁石榴石薄膜材料的光吸收谱及Bi,Al掺入对谱的影响研究 总被引:2,自引:1,他引:1
采用单离子晶场跃迁模型,拟合出钇铁石榴石(YIG)薄膜材料的光吸收谱,与实验谱吻合得较好。从实验和理论上分析了(BIAI)YIG 薄膜材料的光吸收谱,结果表明,Al3+离子的作用如同稀释剂一样,减小了光吸收,Bi3+离子由于其强的自旋轨道耦合作用,增大了跃迁振子强度和跃迁线宽,从而增大了光吸收损耗,在此基础上所作的(BiAl)YIG的理论谱与实验谱符合得较好。 相似文献
79.
By using scanning polarization force microscopy,the deliquescence process and the atomic steps on the cleavage surface of CaCO3 in air were studied in situ.Under an exposure to medium umidity(-57%),the sloiw step movement has been observed. 相似文献
80.
Li Xi Zuoyan Peng Wei Fan Kui Guo Gu Jianmin Muyu Zhao Wu Guoqiang 《Materials Science and Engineering: B》1996,40(2-3):147-152
SrMgxTi1 - xO3 nanocrystals (x = 0.1–0.6) were synthesized by the stearic acid gel method. Powder samples were characterized by X-ray diffraction and X-ray photoelectron (XP) spectroscopy. The results showed that the lattice parameter a and the O 1s XP spectrum changed not only with the Mg content x but also with the grain size d of the samples. The conductivity of a thick film specimen fabricated on an aluminium oxide wafer was investigated in a nitrogen—oxygen atmosphere. 相似文献