全文获取类型
收费全文 | 16595篇 |
免费 | 1007篇 |
国内免费 | 30篇 |
专业分类
电工技术 | 175篇 |
综合类 | 44篇 |
化学工业 | 3617篇 |
金属工艺 | 339篇 |
机械仪表 | 332篇 |
建筑科学 | 742篇 |
矿业工程 | 47篇 |
能源动力 | 542篇 |
轻工业 | 1300篇 |
水利工程 | 128篇 |
石油天然气 | 52篇 |
无线电 | 1173篇 |
一般工业技术 | 3244篇 |
冶金工业 | 2453篇 |
原子能技术 | 122篇 |
自动化技术 | 3322篇 |
出版年
2023年 | 199篇 |
2022年 | 398篇 |
2021年 | 625篇 |
2020年 | 416篇 |
2019年 | 421篇 |
2018年 | 547篇 |
2017年 | 509篇 |
2016年 | 569篇 |
2015年 | 498篇 |
2014年 | 631篇 |
2013年 | 1137篇 |
2012年 | 1033篇 |
2011年 | 1211篇 |
2010年 | 858篇 |
2009年 | 803篇 |
2008年 | 847篇 |
2007年 | 812篇 |
2006年 | 622篇 |
2005年 | 528篇 |
2004年 | 395篇 |
2003年 | 404篇 |
2002年 | 359篇 |
2001年 | 224篇 |
2000年 | 202篇 |
1999年 | 213篇 |
1998年 | 265篇 |
1997年 | 217篇 |
1996年 | 217篇 |
1995年 | 191篇 |
1994年 | 163篇 |
1993年 | 162篇 |
1992年 | 136篇 |
1991年 | 78篇 |
1990年 | 124篇 |
1989年 | 123篇 |
1988年 | 86篇 |
1987年 | 98篇 |
1986年 | 101篇 |
1985年 | 104篇 |
1984年 | 93篇 |
1983年 | 80篇 |
1982年 | 100篇 |
1981年 | 96篇 |
1980年 | 74篇 |
1979年 | 76篇 |
1978年 | 67篇 |
1977年 | 77篇 |
1976年 | 73篇 |
1975年 | 46篇 |
1974年 | 44篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
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
42.
Control law design for rotorcraft fly-by-wire systems normally attempts to decouple the angular responses using fixed-gain crossfeeds. This approach can lead to poor decoupling over the frequency range of pilot inputs and increase the load on the feedback loops. In order to improve the decoupling performance, dynamic crossfeeds should be adopted. Moreover, because of the large changes that occur in the aircraft dynamics due to small changes about the nominal design condition, especially for near-hovering flight, the crossfeed design must be ‘robust’. A new low-order matching method is presented here to design robust crossfeed compensators for multi-input, multi-output (MIMO) systems. The technique minimizes cross-coupling given an anticipated set of parameter variations for the range of flight conditions of concern. Results are presented in this paper of an analysis of the pitch/roll coupling of the UH-60 Black Hawk helicopter in near-hovering flight. A robust crossfeed is designed that shows significant improvement in decoupling perfomance and robustness over the fixed-gain or single point dynamic compensators. The design method and results are presented in an easily used graphical format that lends significant physical insight to the design procedure. This plant precompensation technique is an appropriate preliminary step to the design of robust feedback control laws for rotorcraft. 相似文献
43.
Industries in the US continue to lose ground in international competition. If IS is to help change that trend, it will have to become more creative. Creativity improvement programs are being introduced in other areas of the company— now is the time for IS organizations to follow suit. 相似文献
44.
MA Steller KJ Gurski M Murakami RW Daniel KV Shah E Celis A Sette EL Trimble RC Park FM Marincola 《Canadian Metallurgical Quarterly》1998,4(9):2103-2109
Human papillomavirus (HPV) infection has been causally associated with cervical cancer. We tested the effectiveness of an HLA-A*0201-restricted, HPV-16 E7 lipopeptide vaccine in eliciting cellular immune responses in vivo in women with refractory cervical cancer. In a nonrandomized Phase I clinical trial, 12 women expressing the HLA-A2 allele with refractory cervical or vaginal cancer were vaccinated with four E786-93 lipopeptide inoculations at 3-week intervals. HLA-A2 subtyping was also performed, and HPV typing was assessed on tumor specimens. Induction of epitope-specific CD8+ T-lymphocyte (CTL) responses was analyzed using peripheral blood leukapheresis specimens obtained before and after vaccination. CTL specificity was measured by IFN-gamma release assay using HLA-A*0201 matched target cells. Clinical responses were assessed by physical examination and radiographic images. All HLA-A*0201 patients were able to mount a cellular immune response to a control peptide. E786-93-specific CTLs were elicited in 4 of 10 evaluable HLA-A*0201 subjects before vaccination, 5 of 7 evaluable HLA-A*0201 patients after two vaccinations, and 2 of 3 evaluable HLA-A*0201 cultures after all four inoculations. Two of three evaluable patients' CTLs converted from unreactive to reactive after administration of all four inoculations. There were no clinical responses or treatment toxicities. The ability to generate specific cellular immune responses is retained in patients with advanced cervical cancer. Vaccination with a lipidated HPV peptide epitope appears capable of safely augmenting CTL reactivity. Although enhancements of cellular immune responses are needed to achieve therapeutic utility in advanced cervical cancer, this approach might prove useful in treating preinvasive disease. 相似文献
45.
Daniel Walgraef Elias C. Aifantis 《International Journal of Engineering Science》1985,23(12):1351-1358
By distinguishing among mobile and immobile dislocations and operating within the framework of continuum mechanics it is possible to derive a set of partial differential equations of the diffusion-reaction type for the evolution of dislocation species. On examining the competition between gradient dependent terms modelling the motion of dislocations and nonlinear terms modelling their interactions, it is shown that stable solutions are possible. The wavelength turns out to be a material property in agreement with observations. The discussion is limited to one dimension, that is to glide of straight dislocations in the slip direction, and the model corresponds physically to the ladder-like structure of persistent slip bands. 相似文献
46.
47.
48.
Daniel X. Gouveia Odair P. Ferreira Antonio G. Souza Filho M. G. da Silva J. A. C. de Paiva Oswaldo L. Alves Josué Mendes Filho 《Journal of Materials Science》2007,42(2):534-538
The thermal decomposition properties of Mg–Fe hydrotalcites were studied through in situ 57Fe Mössbauer spectroscopy and in situ X-ray diffraction. Abrupt changes in the quadrupolar splitting measured in the Mössbauer spectra revealed a phase transition from the starting lamellar structure to a new crystalline arrangement. By analyzing the Mössbauer parameters we show that the material is highly disordered in the 300–400 °C temperature range. This hypothesis is confirmed by the X-ray results whose diffractograms indicated the collapse of the lamellar structure and the formation of a solid solution. 相似文献
49.
Atmospheric corrosion of reference metals in Antarctic sites 总被引:1,自引:0,他引:1
Manuel Morcillo Beln Chico Daniel de la Fuente Elisabete Almeida Günter Joseph Susana Rivero Blanca Rosales 《Cold Regions Science and Technology》2004,40(3):165-178
This paper presents the results obtained at three Antarctic test sites participating in the “Ibero-American Map of Atmospheric Corrosiveness” (MICAT), a project on atmospheric corrosion carried out during the period 1988–1994 at some 70 sites distributed across 12 countries of the Latin-American region, Spain and Portugal. The three Antarctic sites are located near the coastline.The singular climatic characteristics of Antarctic regions are related with the purity of the air, the absence of rainfall and the formation of ice on the metallic surface during an important part of the exposure time. However, electrochemical activity is possible below ice layers. This situation affects the structure and morphology of corrosion product films and the resulting corrosion rates of metallic surfaces. 相似文献
50.
A probabilistic model for cleavage fracture with a length scale--parameter estimation and predictions of stationary crack experiments 总被引:1,自引:0,他引:1
This study presents a large experimental investigation in the transition temperature region on a modified A508 steel. Tests were carried out on single-edge-notch-bend specimens with three different crack depth over specimen width ratios to capture the strong constraint effect on fracture toughness. Three test temperatures were considered, covering a range of 85 °C. All specimens failed by cleavage fracture prior to ductile tearing. A recently proposed probabilistic model for the cumulative failure by cleavage was applied to the comprehensive sets of experimental data. This modified weakest link model incorporates a length scale, which together with a threshold stress reduce the scatter in predicted toughness distributions as well as introduces a fracture toughness threshold value. Model parameters were estimated by a robust procedure, which is crucial in applications of probabilistic models to real structures. The conformity between predicted and experimental toughness distributions, respectively, were notable at all the test temperatures. 相似文献