全文获取类型
收费全文 | 16146篇 |
免费 | 942篇 |
国内免费 | 29篇 |
专业分类
电工技术 | 174篇 |
综合类 | 43篇 |
化学工业 | 3428篇 |
金属工艺 | 326篇 |
机械仪表 | 324篇 |
建筑科学 | 706篇 |
矿业工程 | 45篇 |
能源动力 | 517篇 |
轻工业 | 1305篇 |
水利工程 | 135篇 |
石油天然气 | 81篇 |
无线电 | 1196篇 |
一般工业技术 | 3058篇 |
冶金工业 | 2488篇 |
原子能技术 | 128篇 |
自动化技术 | 3163篇 |
出版年
2023年 | 167篇 |
2022年 | 366篇 |
2021年 | 579篇 |
2020年 | 383篇 |
2019年 | 388篇 |
2018年 | 504篇 |
2017年 | 466篇 |
2016年 | 543篇 |
2015年 | 474篇 |
2014年 | 601篇 |
2013年 | 1091篇 |
2012年 | 984篇 |
2011年 | 1175篇 |
2010年 | 812篇 |
2009年 | 763篇 |
2008年 | 801篇 |
2007年 | 789篇 |
2006年 | 606篇 |
2005年 | 525篇 |
2004年 | 390篇 |
2003年 | 399篇 |
2002年 | 348篇 |
2001年 | 224篇 |
2000年 | 191篇 |
1999年 | 227篇 |
1998年 | 282篇 |
1997年 | 229篇 |
1996年 | 215篇 |
1995年 | 207篇 |
1994年 | 187篇 |
1993年 | 162篇 |
1992年 | 140篇 |
1991年 | 94篇 |
1990年 | 137篇 |
1989年 | 135篇 |
1988年 | 93篇 |
1987年 | 104篇 |
1986年 | 108篇 |
1985年 | 113篇 |
1984年 | 95篇 |
1983年 | 81篇 |
1982年 | 103篇 |
1981年 | 94篇 |
1980年 | 76篇 |
1979年 | 75篇 |
1978年 | 63篇 |
1977年 | 82篇 |
1976年 | 74篇 |
1975年 | 48篇 |
1974年 | 49篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
Oliwia Metryka Daniel Wasilkowski Anna Nowak Magorzata Adamczyk-Habrajska Agnieszka Mrozik 《International journal of molecular sciences》2020,21(23)
Due to the systematic increase in the production of nanomaterials (NMs) and their applications in many areas of life, issues associated with their toxicity are inevitable. In particular, the performance of heterogeneous NMs, such as nanocomposites (NCs), is unpredictable as they may inherit the properties of their individual components. Therefore, the purpose of this work was to assess the biological activity of newly synthesized Cu/TiO2-NC and the parent nanoparticle substrates Cu-NPs and TiO2-NPs on the bacterial viability, antioxidant potential and fatty acid composition of the reference Escherichia coli and Bacillus subtilis strains. Based on the toxicological parameters, it was found that B. subtilis was more sensitive to NMs than E. coli. Furthermore, Cu/TiO2-NC and Cu-NPs had an opposite effect on both strains, while TiO2-NPs had a comparable mode of action. Simultaneously, the tested strains exhibited varied responses of the antioxidant enzymes after exposure to the NMs, with Cu-NPs having the strongest impact on their activity. The most considerable alternations in the fatty acid profiles were found after the bacteria were exposed to Cu/TiO2-NC and Cu-NPs. Microscopic images indicated distinct interactions of the NMs with the bacterial outer layers, especially in regard to B. subtilis. Cu/TiO2-NC generally proved to have less distinctive antimicrobial properties on B. subtilis than E. coli compared to its parent components. Presumably, the biocidal effects of the tested NMs can be attributed to the induction of oxidative stress, the release of metal ions and specific electrochemical interactions with the bacterial cells. 相似文献
33.
34.
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
35.
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
36.
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
37.
Design of 5.9 ghz dsrc-based vehicular safety communication 总被引:3,自引:0,他引:3
Daniel Jiang Vikas Taliwal Andreas Meier Wieland Holfelder Ralf Herrtwich 《Wireless Communications, IEEE》2006,13(5):36-43
The automotive industry is moving aggressively in the direction of advanced active safety. Dedicated short-range communication (DSRC) is a key enabling technology for the next generation of communication-based safety applications. One aspect of vehicular safety communication is the routine broadcast of messages among all equipped vehicles. Therefore, channel congestion control and broadcast performance improvement are of particular concern and need to be addressed in the overall protocol design. Furthermore, the explicit multichannel nature of DSRC necessitates a concurrent multichannel operational scheme for safety and non-safety applications. This article provides an overview of DSRC based vehicular safety communications and proposes a coherent set of protocols to address these requirements 相似文献
38.
39.
We report new measurements of the effective thermal conductivity Keff and relaxation time τ in dilute mixtures of3He in superfluid4He, with molar concentrationsX≤10−3. The temperature range extended fromT≈1.4 K toT
λ. Both Kcff and τ are found to agree with theoretical predictions, in contrast to previous experiments where significant differences
were observed. A new thermal conductivity cell design was used which almost completely eliminates extraneous volumes and surfaces,
and the earlier results are explained in relation to these design changes. 相似文献
40.
John C. Hart Gordon W. Lescinsky Daniel J. Sandin Thomas A. DeFanti Louis H. Kauffman 《The Visual computer》1993,9(7):346-355
The pipelined architecture and parallel organization of the AT&T Pixel Machine image computer are described and demonstrated with applications for the visualization of multidimensional fractals, particularly linear fractals and quaternion/ stacked Julia sets. Techniques for pushing the Pixel Machine to its peak abilities are described and apply to more recent parallel image computers as well. 相似文献