全文获取类型
收费全文 | 5734篇 |
免费 | 122篇 |
国内免费 | 8篇 |
专业分类
电工技术 | 35篇 |
综合类 | 4篇 |
化学工业 | 921篇 |
金属工艺 | 100篇 |
机械仪表 | 94篇 |
建筑科学 | 182篇 |
矿业工程 | 12篇 |
能源动力 | 182篇 |
轻工业 | 420篇 |
水利工程 | 33篇 |
石油天然气 | 30篇 |
无线电 | 208篇 |
一般工业技术 | 741篇 |
冶金工业 | 2228篇 |
原子能技术 | 46篇 |
自动化技术 | 628篇 |
出版年
2023年 | 22篇 |
2022年 | 63篇 |
2021年 | 71篇 |
2020年 | 60篇 |
2019年 | 58篇 |
2018年 | 80篇 |
2017年 | 112篇 |
2016年 | 114篇 |
2015年 | 68篇 |
2014年 | 213篇 |
2013年 | 277篇 |
2012年 | 155篇 |
2011年 | 209篇 |
2010年 | 166篇 |
2009年 | 177篇 |
2008年 | 171篇 |
2007年 | 156篇 |
2006年 | 169篇 |
2005年 | 141篇 |
2004年 | 150篇 |
2003年 | 124篇 |
2002年 | 100篇 |
2001年 | 86篇 |
2000年 | 92篇 |
1999年 | 103篇 |
1998年 | 719篇 |
1997年 | 399篇 |
1996年 | 287篇 |
1995年 | 192篇 |
1994年 | 134篇 |
1993年 | 151篇 |
1992年 | 49篇 |
1991年 | 57篇 |
1990年 | 48篇 |
1989年 | 45篇 |
1988年 | 49篇 |
1987年 | 29篇 |
1986年 | 28篇 |
1985年 | 68篇 |
1984年 | 36篇 |
1983年 | 26篇 |
1982年 | 30篇 |
1981年 | 40篇 |
1980年 | 37篇 |
1979年 | 25篇 |
1978年 | 19篇 |
1977年 | 63篇 |
1976年 | 103篇 |
1975年 | 17篇 |
1974年 | 18篇 |
排序方式: 共有5864条查询结果,搜索用时 15 毫秒
31.
Hannes Holm Markus Buschle Robert Lagerström Mathias Ekstedt 《Software and Systems Modeling》2014,13(2):825-841
Enterprise Architecture (EA) is an approach used to provide decision support based on organization-wide models. The creation of such models is, however, cumbersome as multiple aspects of an organization need to be considered, making manual efforts time-consuming, and error prone. Thus, the EA approach would be significantly more promising if the data used when creating the models could be collected automatically—a topic not yet properly addressed by either academia or industry. This paper proposes network scanning for automatic data collection and uses an existing software tool for generating EA models (ArchiMate is employed as an example) based on the IT infrastructure of enterprises. While some manual effort is required to make the models fully useful to many practical scenarios (e.g., to detail the actual services provided by IT components), empirical results show that the methodology is accurate and (in its default state) require little effort to carry out. 相似文献
32.
Thorsteinn Astradsson Felix Sellberg Ylva Tiblom Ehrsson Karl Sandstrm Gran Laurell 《International journal of molecular sciences》2022,23(11)
In this real-world study, the aims were to prospectively evaluate the expression of inflammatory proteins in serum collected from head and neck cancer patients before and after treatment, and to assess whether there were differences in expression associated with treatment modalities. The mixed study cohort consisted of 180 patients with head and neck cancer. The most common tumor sites were the oropharynx (n = 81), the oral cavity (n = 53), and the larynx (n = 22). Blood tests for proteomics analysis were carried out before treatment, 7 weeks after the start of treatment, and 3 and 12 months after the termination of treatment. Sera were analyzed for 83 proteins using an immuno-oncology biomarker panel (Olink, Uppsala, Sweden). Patients were divided into four treatment groups: surgery alone (Surg group, n = 24), radiotherapy with or without surgery (RT group, n = 94), radiotherapy with concomitant cisplatin (CRT group, n = 47), and radiotherapy with concomitant targeted therapy (RT Cetux group, n = 15). For the overall cohort, the expression levels of 15 of the 83 proteins changed significantly between the pretreatment sample and the sample taken 7 weeks after the start of treatment. At 7 weeks after the start of treatment, 13 proteins showed lower expression in the CRT group compared to the RT group. The majority of the inflammatory proteins had returned to their pretreatment levels after 12 months. It was clearly demonstrated that cisplatin-based chemoradiation has immunological effects in patients with head and neck cancer. This analysis draws attention to several inflammatory proteins that are of interest for further studies. 相似文献
33.
34.
We study the problem of computing Nash equilibria in a two-player normal form (bimatrix) game from the perspective of parameterized complexity. Recent results proved hardness for a number of variants, when parameterized by the support size. We complement those results, by identifying three cases in which the problem becomes fixed-parameter tractable. Our results are based on a graph-theoretic representation of a bimatrix game, and on applying graph-theoretic tools on this representation. 相似文献
35.
The enhanced energy absorption characteristics of fibre-reinforced concrete, compared to plain concrete, has in experimentally studies been shown to improve the projectile resistance and motivate its increased usage in protective structures. However, the high cost of undertaking experiments and the high parameter variation and dependency of the experimental setups and results, respectively, make it difficult to draw generic conclusions of how the addition and increased amount of fibres affects the local damage caused by projectile impact, which motivates the use of numerical simulations to study this. The numerical hydrocode AUTODYN was used in a qualitative study of how the addition of different amounts of fibres, modelled as different post-crack relations, influence the depth of penetration and crater formation on the front and rear face of a concrete target. Fibres added to the concrete mix had a minor influence on the depth of penetration while the crater size on both front and rear faces of the target decreases. The crack propagation beyond the crater on the front face was also reduced when fibres were added to the concrete. An increased amount of fibres in the concrete showed no effect on the size of the front-face crater, but led to further decreased size of the crater on the rear face of the concrete cylinder. It is concluded that the scabbing crater can be reduced in size and prevented by usage of fibre-reinforced concrete even if the depth of penetration is only slightly less than to penetration depth in plain concrete. 相似文献
36.
Pedro Santarém Andrade António Almeida Saraiva 《Bulletin of Engineering Geology and the Environment》2010,69(2):207-214
This work defines the physical and mechanical characteristics of phyllites and metagreywackes belonging to a schist–greywacke complex in central Portugal. The index properties, point load strength, uniaxial compressive strength, slake durability and Schmidt rebound hardness were determined. In general, the metagreywackes gave a higher strength than phyllites with the same weathering degree. Possible correlations and estimation models were established and compared with the equations obtained by different researchers. 相似文献
37.
Tine Missiaen Martin Söderström Paula Vanninen 《The Science of the total environment》2010,408(17):3536-914
This paper discusses the results of geophysical and chemical investigations carried out in a chemical munition dumpsite in the southern Baltic Sea, east of the island of Bornholm. After WW2 over 32,000 tons of chemical war material was dumped here including shells and bombs as well as small drums and containers. The geophysical investigations combined very-high-resolution seismics and gradiometric measurements. The results indicate the presence of a large number of objects buried just below the seafloor. The size of the objects and their distribution, with a marked increase in density towards the center of the dumpsite, suggests that we are dealing with dumped war material. Sediment and near-bottom water samples, taken within the dumpsite and in the surrounding area, were analysed for the presence of various chemical warfare agents (CWA) including Adamsite, Clark, sulphur mustard, tabun, chlorobenzene and arsine oil. The results indicate a widespread contamination that reaches far beyond the dumpsite boundary. CWA degradation products were found in most of the sediment samples. The contamination was mostly related to arsenic containing compounds; only one sample indicated the presence of sulfur mustard. Although the correlation between detected objects and CWA concentrations is not always straightforward, the overall results suggest that a lot of the dumped war material is leaking and that over the years the contamination has reached the seafloor sediments. 相似文献
38.
北电网络提供的Contivity解决方案不仅可以使用户建立各种类型的VPN,而且还可以把这些VPN集成到未来的融合话音和数据的网络中。该方案已实现了安全路由选择;可通过多种技术支持鉴权功能,从而实现安全接入;允许用户使用其各自的安全性配置文件设置;其设计中没有“后门”,重点介绍了Contivity 2700网关的主要特征及其优势。 相似文献
39.
T. Sderstrm F.‐J. Haug X. Niquille C. Ballif 《Progress in Photovoltaics: Research and Applications》2009,17(3):165-176
Substrate configuration allows for the deposition of thin film silicon (Si) solar cells on non‐transparent substrates such as plastic sheets or metallic foils. In this work, we develop processes compatible with low Tg plastics. The amorphous Si (a‐Si:H) and microcrystalline Si (µc‐Si:H) films are deposited by plasma enhanced chemical vapour deposition, at very high excitation frequencies (VHF‐PECVD). We investigate the optical behaviour of single and triple junction devices prepared with different back and front contacts. The back contact consists either of a 2D periodic grid with moderate slope, or of low pressure CVD (LP‐CVD) ZnO with random pyramids of various sizes. The front contacts are either a 70 nm thick, nominally flat ITO or a rough 2 µm thick LP‐CVD ZnO. We observe that, for a‐Si:H, the cell performance depends critically on the combination of thin flat or thick rough front TCOs and the back contact. Indeed, for a‐Si:H, a thick LP‐CVD ZnO front contact provides more light trapping on the 2D periodic substrate. Then, we investigate the influence of the thick and thin TCOs in conjunction with thick absorbers (µc‐Si:H). Because of the different nature of the optical systems (thick against thin absorber layer), the antireflection effect of ITO becomes more effective and the structure with the flat TCO provides as much light trapping as the rough LP‐CVD ZnO. Finally, the conformality of the layers is investigated and guidelines are given to understand the effectiveness of the light trapping in devices deposited on periodic gratings. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
40.
Nils Lundberg Mikael Östling Carl-Mikael Zetterling Per Tägtström Ulf Jansson 《Journal of Electronic Materials》2000,29(3):372-375
In this study, tungsten carbide, with its hardness, chemical inertness, thermal stability and low resistivity (25 μΩ cm)1 is shown as a reliable contact material to n- and p-type 6H-SiC for very high temperature applications. WC films with thicknesses
of 100–150 nm were deposited by chemical vapor deposition (CVD) from a WF6/C3H8/H2 mixture at 1173 K. A method to pattern CVD-tungsten carbide is suggested. TEM analysis of as deposited samples displayed
a clear and unreacted interface. The electrical investigations of the p-type 6H-SiC Schottky contacts revealed a high rectification
ratio and a low reverse current density (6.1 × 10−5 A cm−2, −10 V) up to 773 K. On n-type, a low barrier (ΦBn=0.79 eV) at room temperature was observed. The low ΦBn value suggests WC to be promising as an ohmic contact material on highly doped n-type epi-layers. We will show a temperature
dependence for the barrier height of tungsten carbide contacts that can be related to the simultaneous change in the energy
bandgap, which should be considered when designing SiC devices intended for high temperature operation. 相似文献