全文获取类型
收费全文 | 80037篇 |
免费 | 7603篇 |
国内免费 | 4220篇 |
专业分类
电工技术 | 5241篇 |
技术理论 | 4篇 |
综合类 | 5598篇 |
化学工业 | 12682篇 |
金属工艺 | 4303篇 |
机械仪表 | 4487篇 |
建筑科学 | 5709篇 |
矿业工程 | 1956篇 |
能源动力 | 2225篇 |
轻工业 | 8683篇 |
水利工程 | 1725篇 |
石油天然气 | 2915篇 |
武器工业 | 779篇 |
无线电 | 8304篇 |
一般工业技术 | 9272篇 |
冶金工业 | 4740篇 |
原子能技术 | 844篇 |
自动化技术 | 12393篇 |
出版年
2024年 | 357篇 |
2023年 | 1222篇 |
2022年 | 2567篇 |
2021年 | 3384篇 |
2020年 | 2546篇 |
2019年 | 2050篇 |
2018年 | 2429篇 |
2017年 | 2634篇 |
2016年 | 2536篇 |
2015年 | 3448篇 |
2014年 | 4224篇 |
2013年 | 5370篇 |
2012年 | 6108篇 |
2011年 | 6666篇 |
2010年 | 5797篇 |
2009年 | 5483篇 |
2008年 | 5625篇 |
2007年 | 5191篇 |
2006年 | 4480篇 |
2005年 | 3626篇 |
2004年 | 2629篇 |
2003年 | 2245篇 |
2002年 | 2125篇 |
2001年 | 1731篇 |
2000年 | 1255篇 |
1999年 | 967篇 |
1998年 | 696篇 |
1997年 | 592篇 |
1996年 | 484篇 |
1995年 | 444篇 |
1994年 | 338篇 |
1993年 | 293篇 |
1992年 | 213篇 |
1991年 | 174篇 |
1990年 | 201篇 |
1989年 | 159篇 |
1988年 | 107篇 |
1987年 | 115篇 |
1986年 | 127篇 |
1985年 | 110篇 |
1984年 | 99篇 |
1983年 | 83篇 |
1982年 | 103篇 |
1981年 | 106篇 |
1980年 | 97篇 |
1979年 | 78篇 |
1978年 | 65篇 |
1977年 | 78篇 |
1976年 | 68篇 |
1975年 | 47篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
刘家山排土场为民采排弃形成,已经出现大规模滑坡。为了保证上下游生产生活设施的安全,依据现场实际情况,结合现场调查,提出了削坡处理的方案。经过治理后,刘家山排土场平稳地渡过了雨季,目前处于稳定状态,达到了治理目的。 相似文献
62.
The Caputo and Caputo–Fabrizio derivative are applied to study a second‐grade nanofluid over a vertical plate. A comparative analysis is presented to study the unsteady free convection of a second‐grade nanofluid with a new time–space fractional heat conduction. The governing equations with mixed time–space fractional derivatives are non‐dimensionalized and solved numerically, and a comparison between the Caputo and the Caputo–Fabrizio models is made. It is found that the temperature is higher for the Caputo–Fabrizio fractional model than the Caputo model, but the higher velocity only exists near the vertical plate for the Caputo–Fabrizio model than the Caputo model. Moreover, the velocity for the Caputo model will exceed the Caputo–Fabrizio model as y evolves. 相似文献
63.
Daniel H. Stones Anne-Marie Krachler 《International journal of molecular sciences》2015,16(2):2626-2640
The ability of bacterial species to colonize and infect host organisms is critically dependent upon their capacity to adhere to cellular surfaces of the host. Adherence to cell surfaces is known to be essential for the activation and delivery of certain virulence factors, but can also directly affect host cell signaling to aid bacterial spread and survival. In this review we will discuss the recent advances in the field of bacterial adhesion, how we are beginning to unravel the effects adhesins have on host cell signaling, and how these changes aid the bacteria in terms of their survival and evasion of immune responses. Finally, we will highlight how the exploitation of bacterial adhesins may provide new therapeutic avenues for the treatment of a wide range of bacterial infections. 相似文献
64.
Role stress has received a lot of research attention in psychological, sociological, and organizational studies over the last several decades. Based on a literature review of about 300 journal articles, this article examines prominent consequences of role stress. Specific focus is on researching differences in relationships between facets of role stress (i.e., role ambiguity, role conflict, and role overload) and frequently cited consequences using techniques of meta-analysis. Findings indicate that each role stress facet has a different relationship with the eight consequences studied. Role stress research can benefit from looking at each facet individually in addition to role stress generally. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
65.
The applicability of the identical elements (IE) model of arithmetic fact retrieval (T. C. Rickard, A. F. Healy, & L. E. Bourne, 1994) to cued recall from episodic (image and sentence) memory was explored in 3 transfer experiments. In agreement with results from arithmetic, speedup following even minimal practice recalling a missing word from an episodically bound word triplet did not transfer positively to other cued recall items involving the same triplet. The shape of the learning curve further supported a shift from episode-based to IE-based recall, extending some models of skill learning to cued recall practice. In contrast with previous findings, these results indicate that a form of representation that is independent of the original episodic memory underlies cued-recall performance following minimal practice. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
66.
Xue‐Yong Liu Xiao‐Bin Ding Zhao‐Hui Zheng Yu‐Xing Peng Albert S
C Chan C
W Yip Xin‐Ping Long 《Polymer International》2003,52(2):235-240
Amphiphilic magnetic microspheres ranging in diameter from 5 to 100 µm were prepared by dispersion copolymerization of styrene and poly(ethylene oxide) vinylbenzyl (PEO‐VB) macromonomer (MPEO) in the presence of Fe3O4 magnetic fluid. The effects of various polymerization parameters on the average particle size were systematically investigated. The average particle size was found to increase with increasing styrene concentration and initiator concentration. It also increased with decreasing stabilizer concentration and molecular weight of MPEO. The content of the hydroxyl groups localized in the microspheres ranged from 0.01 to 0.2 mmol g?1. © 2003 Society of Chemical Industry 相似文献
67.
W. Shieh R. Hui X. Yi 《Photonics Technology Letters, IEEE》2006,18(10):1122-1124
We perform a systematic measurement of the degree-of-polarization (DOP) and eye-closure penalty for optical signals with orthogonal polarizations. We find that the symmetry of DOP is maintained for the orthogonal polarizations under both first and higher order polarization-mode dispersion (PMD), whereas the symmetry of eye-closure penalty is broken under second-order PMD. An orthogonal polarization pair can have large disparity of eye-closure penalty despite an identical DOP. We also demonstrate a novel approach to estimate the maximum eye-closure penalty asymmetry with three orthogonal polarizations on the Poincare/spl acute/ sphere. 相似文献
68.
The current Internet and wireless networks are harsh environments for transporting high-bandwidth multimedia data. We examine the technical issues involved, and describe an end-to-end solution to support a Web-based learn-on-demand system that operates in a wireless campus environment. 相似文献
69.
介绍如何利用AutoCAD开发适合电气专业使用的CAD系统,通过编制电气CAD的功能菜单,构造电气元件库,增强CAD的专业性能。编制电气CAD可以有效地统一本单位电气制图标准,方便电气工程师使用CAD进行专业设计。 相似文献
70.