全文获取类型
收费全文 | 1856篇 |
免费 | 6篇 |
专业分类
电工技术 | 12篇 |
综合类 | 1篇 |
化学工业 | 89篇 |
金属工艺 | 17篇 |
机械仪表 | 8篇 |
建筑科学 | 20篇 |
能源动力 | 6篇 |
轻工业 | 39篇 |
无线电 | 142篇 |
一般工业技术 | 87篇 |
冶金工业 | 1359篇 |
原子能技术 | 10篇 |
自动化技术 | 72篇 |
出版年
2021年 | 4篇 |
2020年 | 8篇 |
2019年 | 5篇 |
2018年 | 6篇 |
2017年 | 7篇 |
2016年 | 7篇 |
2014年 | 4篇 |
2013年 | 19篇 |
2012年 | 12篇 |
2011年 | 12篇 |
2010年 | 19篇 |
2009年 | 10篇 |
2008年 | 17篇 |
2007年 | 13篇 |
2006年 | 23篇 |
2005年 | 24篇 |
2004年 | 14篇 |
2003年 | 8篇 |
2002年 | 10篇 |
2001年 | 11篇 |
2000年 | 6篇 |
1999年 | 47篇 |
1998年 | 399篇 |
1997年 | 219篇 |
1996年 | 150篇 |
1995年 | 88篇 |
1994年 | 85篇 |
1993年 | 89篇 |
1992年 | 31篇 |
1991年 | 25篇 |
1990年 | 29篇 |
1989年 | 38篇 |
1988年 | 33篇 |
1987年 | 29篇 |
1986年 | 26篇 |
1985年 | 28篇 |
1984年 | 10篇 |
1983年 | 5篇 |
1982年 | 15篇 |
1981年 | 16篇 |
1980年 | 21篇 |
1979年 | 11篇 |
1978年 | 8篇 |
1977年 | 45篇 |
1976年 | 116篇 |
1975年 | 12篇 |
1974年 | 6篇 |
1973年 | 9篇 |
1970年 | 3篇 |
1955年 | 3篇 |
排序方式: 共有1862条查询结果,搜索用时 15 毫秒
51.
Layout symmetry is an important and desired feature in graph drawing. While there is a substantial body of work in computer vision around the detection and measurement of symmetry in images, there has been little effort to define and validate meaningful measures of the symmetry of graph drawings. In this paper, we evaluate two algorithms that have been proposed for measuring graph drawing symmetry, comparing their judgments to those of human subjects, and investigating the use of stress as an alternative measure of symmetry. We discuss advantages and disadvantages of these measures, possible ways to improve them, and implications for the design of algorithms that optimize the symmetry in the layout. 相似文献
52.
Detailed Real-Time Urban 3D Reconstruction from Video 总被引:2,自引:0,他引:2
M. Pollefeys D. Nistér J.-M. Frahm A. Akbarzadeh P. Mordohai B. Clipp C. Engels D. Gallup S.-J. Kim P. Merrell C. Salmi S. Sinha B. Talton L. Wang Q. Yang H. Stewénius R. Yang G. Welch H. Towles 《International Journal of Computer Vision》2008,78(2-3):143-167
The paper presents a system for automatic, geo-registered, real-time 3D reconstruction from video of urban scenes. The system
collects video streams, as well as GPS and inertia measurements in order to place the reconstructed models in geo-registered
coordinates. It is designed using current state of the art real-time modules for all processing steps. It employs commodity
graphics hardware and standard CPU’s to achieve real-time performance. We present the main considerations in designing the
system and the steps of the processing pipeline. Our system extends existing algorithms to meet the robustness and variability
necessary to operate out of the lab. To account for the large dynamic range of outdoor videos the processing pipeline estimates
global camera gain changes in the feature tracking stage and efficiently compensates for these in stereo estimation without
impacting the real-time performance. The required accuracy for many applications is achieved with a two-step stereo reconstruction
process exploiting the redundancy across frames. We show results on real video sequences comprising hundreds of thousands
of frames. 相似文献
53.
Brick masons and mason tenders report a high prevalence of work-related musculoskeletal disorders (WMSDs), many of which can be prevented with changes in materials, work equipment or work practices. To explore the use of "best practices" in the masonry industry, NIOSH organized a 2-day meeting of masonry stakeholders. Attendees included 30 industry representatives, 5 health and safety researchers, 4 health/safety specialists, 2 ergonomic consultants, and 2 representatives of state workers' compensation programs. Small groups discussed ergonomic interventions currently utilized in the masonry industry, including factors affecting intervention implementation and ways to promote diffusion of interventions. Meeting participants also identified various barriers to intervention implementation, including business considerations, quality concerns, design issues, supply problems, jobsite conditions and management practices that can slow or limit intervention diffusion. To be successful, future diffusion efforts must not only raise awareness of available solutions but also address these practical concerns. 相似文献
54.
D. O. Welch C. S. Pande R. Caton R. Viswanathan 《Journal of Low Temperature Physics》1983,52(3-4):289-300
The available data on the effect of neutron and α-particle irradiation on the superconducting properties and the low-temperature specific heat capacity of single- and polycrystalline V3Si were analyzed in a unified manner. It was found that the electron-phonon renormalization parameter λ does not vary simply proportionally to the bare density of electron states at the Fermi level as had been earlier conjectured by Dynes and Varma, nor does it vary in exactly the same manner as found by Fradin and Williamson to hold for a variety of vanadium-based A15 structure compounds and pseudobinary alloys. When the behavior of V3Si is compared with that of Nb3Sn, Nb3Al, and Nb3Ge, it is seen that the response to disorder of parameters of importance in the superconductivity of these compounds does not follow any simple, universal behavior. 相似文献
55.
Srikanth Sastry Tsvetomira Radeva Jianer Chen Jennifer L. Welch 《Pervasive and Mobile Computing》2013,9(2):311-323
Wireless sensor networks (WSNs) deployed in hostile environments suffer from a high rate of node failure. We investigate the effect of such failure rate on network connectivity. We provide a formal analysis that establishes the relationship between node density, network size, failure probability, and network connectivity. We show that large networks can maintain connectivity despite a significantly high probability of node failure. We derive mathematical functions that provide lower bounds on network connectivity in WSNs. We compute these functions for some realistic values of node reliability, area covered by the network, and node density, to show that, for instance, networks with over a million nodes can maintain connectivity with a probability exceeding 95% despite node failure probability exceeding 53%. 相似文献
56.
Lin YY Evans RD Welch E Hsu BN Madison AC Fair RB 《Sensors and actuators. B, Chemical》2010,150(1):465-470
A low voltage, two-level-metal, and multi-layer insulator electrowetting-on-dielectric (EWD) platform is presented. Dispensing 300pl droplets from 140nl closed on-chip reservoirs was accomplished with as little as 11.4V solely through EWD forces, and the actuation threshold voltage was 7.2V with a 1Hz voltage switching rate between electrodes. EWD devices were fabricated with a multilayer insulator consisting of 135nm sputtered tantalum pentoxide (Ta(2)O(5)) and 180nm parylene C coated with 70nm of CYTOP. Furthermore, the minimum actuation threshold voltage followed a previously published scaling model for the threshold voltage, V(T), which is proportional to (t/ε(r))(1/2), where t and ε(r) are the insulator thickness and dielectric constant respectively. Device threshold voltages are compared for several insulator thicknesses (200nm, 500nm, and 1μm), different dielectric materials (parylene C and tantalum pentoxide), and homogeneous versus heterogeneous compositions. Additionally, we used a two-level-metal fabrication process, which enables the fabrication of smaller and denser electrodes with high interconnect routing flexibility. We also have achieved low dispensing and actuation voltages for scaled devices with 30pl droplets. 相似文献
57.
HN Nguyen D Frank S Handt HC Rieband N Maurin HG Sieberth S Matern 《Canadian Metallurgical Quarterly》1999,94(1):232-235
Intense immunosuppressive therapy is used frequently for treatment of systemic vasculitides, collagenoses, rapidly progressive glomerulonephritis, and after organ transplantation. Numerous serious treatment-related side effects include localized or disseminated opportunistic infections, and require careful monitoring of immunosuppressed patients. Gastrointestinal infections with Mycobacterium avium complex (MAC) or other nontuberculous mycobacteria have been previously identified in HIV seropositive patients only. We now report the first case of an HIV seronegative patient who received immunosuppressive therapy for rapidly progressive glomerulonephritis. The patient presented with severe lower gastrointestinal bleeding and was diagnosed to have ulcerative colitis due to infection with MAC. The patient recovered promptly after administration of antimycobacterial therapy. MAC infection should be included in the differential diagnosis of gastrointestinal bleeding in all immunodeficient patients. The significance of repeated colonoscopy to obtain multiple biopsy specimens with histological examination for foam cells and specific staining for acid-fast organisms is emphasized. 相似文献
58.
59.
60.
Mary Welch Baillargeon 《Lipids》1990,25(12):841-848
A crude, commercialGeotrichum candidum lipase (EC 3.1.1.3) preparation (Amano GC-20) was purified by hydrophobic interaction chromatography on Octyl Sepharose.
The purified enzyme is a microheterogeneous glycoprotein containing isozymes varying in molecular weight, pI and specificity.
It consists of 64, 62 and 59 kDa species as determined by denaturing polyacrylamide gel electrophoresis. Five isozymes (pI
4.40, 4.47, 4.58, 4.67 and 4.72) are detected by isoelectric focusing using both silver and activity stains. Chromatofocusing
was used to separate the isozymes according to pI. Although all the isozymes are specific for oleatevs stearate esters, one isozyme (pI 4.72) is also specific for oleatevs palmitate. The number of isozymes is reduced to two (pI 4.67 and 4.72) after carbohydrate removal using endoglycosidase F/N-glycosidase.
These isozymes may be products of two lipase genes.
Presented in part at the Annual Meeting of the American Oil Chemists' Society, Baltimore, MD, April 22–25, 1990 相似文献