全文获取类型
收费全文 | 4115篇 |
免费 | 42篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 31篇 |
综合类 | 1篇 |
化学工业 | 259篇 |
金属工艺 | 38篇 |
机械仪表 | 13篇 |
建筑科学 | 51篇 |
矿业工程 | 2篇 |
能源动力 | 36篇 |
轻工业 | 114篇 |
水利工程 | 12篇 |
石油天然气 | 4篇 |
无线电 | 148篇 |
一般工业技术 | 219篇 |
冶金工业 | 3051篇 |
原子能技术 | 9篇 |
自动化技术 | 173篇 |
出版年
2023年 | 14篇 |
2022年 | 25篇 |
2021年 | 38篇 |
2020年 | 29篇 |
2019年 | 33篇 |
2018年 | 34篇 |
2017年 | 38篇 |
2016年 | 29篇 |
2015年 | 18篇 |
2014年 | 35篇 |
2013年 | 81篇 |
2012年 | 58篇 |
2011年 | 57篇 |
2010年 | 44篇 |
2009年 | 44篇 |
2008年 | 62篇 |
2007年 | 44篇 |
2006年 | 27篇 |
2005年 | 33篇 |
2004年 | 31篇 |
2003年 | 32篇 |
2002年 | 20篇 |
2001年 | 24篇 |
2000年 | 19篇 |
1999年 | 109篇 |
1998年 | 900篇 |
1997年 | 534篇 |
1996年 | 337篇 |
1995年 | 198篇 |
1994年 | 157篇 |
1993年 | 197篇 |
1992年 | 41篇 |
1991年 | 57篇 |
1990年 | 42篇 |
1989年 | 43篇 |
1988年 | 56篇 |
1987年 | 48篇 |
1986年 | 40篇 |
1985年 | 33篇 |
1984年 | 14篇 |
1983年 | 16篇 |
1982年 | 23篇 |
1981年 | 31篇 |
1980年 | 35篇 |
1979年 | 12篇 |
1978年 | 18篇 |
1977年 | 66篇 |
1976年 | 180篇 |
1975年 | 18篇 |
1974年 | 13篇 |
排序方式: 共有4161条查询结果,搜索用时 15 毫秒
81.
Doctors read literature to keep abreast of medical advances. A recommendation from the 1993 World Summit for Medical Education is that medical schools should teach medical students to critically appraise scientific reports. The Department of Community Health Sciences of Aga Khan University Medical College teaches basic research methods to medical students. This is now supplemented with "Critical Reading". Critical reading was first taught to 67 third year students between October, 1993 and May, 1994. A "validity check-list for critical readers" was introduced in a two week orientation consisting of three one-hour classroom sessions and four one-hour small group sessions. Thereafter, small groups met monthly to critique clinical epidemiological reports relevant to current organ system teaching. The students reading attitudes and critical appraisal skills were assessed through continuous assessment and a written final examination with questionnaire. All but three students passed the final examination (mean score (74%, standard deviation 12%). Sixty-four of 67 (96%) completed questionnaires. All (73% strongly) agreed that critical reading skills were essential, but only 30% strongly agreed that they had, indeed, mastered the skills. Ninety-seven percent (56% strongly) disagreed that year three was too early to start critical reading. Clinical teaching staff expressed interest in learning these skills. Students benefited from and enjoyed this first critical reading course. It strengthened ties between clinical and community health sciences teaching staff. The critical reading skills of the clinical teaching staff is being addressed in seminars to strengthen institutional research capacity. 相似文献
82.
A Doan G Thinakaran DR Borchelt HH Slunt T Ratovitsky M Podlisny DJ Selkoe M Seeger SE Gandy DL Price SS Sisodia 《Canadian Metallurgical Quarterly》1996,17(5):1023-1030
Mutations in a gene encoding a multitransmembrane protein, termed presenilin 1 (PS1), are causative in the majority of early-onset cases of AD. To determine the topology of PS1, we utilized two strategies: first, we tested whether putative transmembranes are sufficient to export a protease-sensitive substrate across a lipid bilayer; and second, we examined the binding of antibodies to specific PS1 epitopes in cultured cells selectively permeabilized with the pore-forming toxin, streptolysin-O. We document that the "loop," N-terminal, and C-terminal domains of PS1 are oriented toward the cytoplasm. 相似文献
83.
Paul Martinsen Johannes Blaschke Robert Jordan 《Computer Physics Communications》2009,180(10):1983-1989
Modern graphics cards, commonly used in desktop computers, have evolved beyond a simple interface between processor and display to incorporate sophisticated calculation engines that can be applied to general purpose computing. The Monte Carlo algorithm for modelling photon transport in turbid media has been implemented on an NVIDIA® 8800gt graphics card using the CUDA toolkit. The Monte Carlo method relies on following the trajectory of millions of photons through the sample, often taking hours or days to complete. The graphics-processor implementation, processing roughly 110 million scattering events per second, was found to run more than 70 times faster than a similar, single-threaded implementation on a 2.67 GHz desktop computer.
Program summary
Program title: Phoogle-C/Phoogle-GCatalogue identifier: AEEB_v1_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEEB_v1_0.htmlProgram obtainable from: CPC Program Library, Queen's University, Belfast, N. IrelandLicensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.htmlNo. of lines in distributed program, including test data, etc.: 51 264No. of bytes in distributed program, including test data, etc.: 2 238 805Distribution format: tar.gzProgramming language: C++Computer: Designed for Intel PCs. Phoogle-G requires a NVIDIA graphics card with support for CUDA 1.1Operating system: Windows XPHas the code been vectorised or parallelized?: Phoogle-G is written for SIMD architecturesRAM: 1 GBClassification: 21.1External routines: Charles Karney Random number library. Microsoft Foundation Class library. NVIDA CUDA library [1].Nature of problem: The Monte Carlo technique is an effective algorithm for exploring the propagation of light in turbid media. However, accurate results require tracing the path of many photons within the media. The independence of photons naturally lends the Monte Carlo technique to implementation on parallel architectures. Generally, parallel computing can be expensive, but recent advances in consumer grade graphics cards have opened the possibility of high-performance desktop parallel-computing.Solution method: In this pair of programmes we have implemented the Monte Carlo algorithm described by Prahl et al. [2] for photon transport in infinite scattering media to compare the performance of two readily accessible architectures: a standard desktop PC and a consumer grade graphics card from NVIDIA.Restrictions: The graphics card implementation uses single precision floating point numbers for all calculations. Only photon transport from an isotropic point-source is supported. The graphics-card version has no user interface. The simulation parameters must be set in the source code. The desktop version has a simple user interface; however some properties can only be accessed through an ActiveX client (such as Matlab).Additional comments: The random number library used has a LGPL (http://www.gnu.org/copyleft/lesser.html) licence.Running time: Runtime can range from minutes to months depending on the number of photons simulated and the optical properties of the medium.References:- [1]
- http://www.nvidia.com/object/cuda_home.html.
- [2]
- S. Prahl, M. Keijzer, Sl. Jacques, A. Welch, SPIE Institute Series 5 (1989) 102.
84.
Jordan Navarro Elsa Yousfi Jonathan Deniel Christophe Jallais Mercedes Bueno Alexandra Fort 《Ergonomics》2016,59(12):1553-1564
In the past, lane departure warnings (LDWs) were demonstrated to improve driving behaviours during lane departures but little is known about the effects of unreliable warnings. This experiment focused on the influence of false warnings alone or in combination with missed warnings and warning onset on assistance effectiveness and acceptance. Two assistance unreliability levels (33 and 17%) and two warning onsets (partial and full lane departure) were manipulated in order to investigate interaction. Results showed that assistance, regardless unreliability levels and warning onsets, improved driving behaviours during lane departure episodes and outside of these episodes by favouring better lane-keeping performances. Full lane departure and highly unreliable warnings, however, reduced assistance efficiency. Drivers’ assistance acceptance was better for the most reliable warnings and for the subsequent warnings. The data indicate that imperfect LDWs (false warnings or false and missed warnings) further improve driving behaviours compared to no assistance.
Practitioner Summary: This study revealed that imperfect lane departure warnings are able to significantly improve driving performances and that warning onset is a key element for assistance effectiveness and acceptance. The conclusion may be of particular interest for lane departure warning designers. 相似文献
85.
Synchronization of signal packets is required in networks in order to route the packets. Due to changes in the interarrival times of the packets the inputs to the routing circuits may exhibit oscillatory metastability. Oscillatory metastability can be eliminated in optical circuits by the addition of logic signal stretch. This can be done because the propagation time of optics can be precisely controlled. An algorithm for inserting logic signal stretch to eliminate oscillatory metastability is presented herein. 相似文献
86.
Minds and Machines - This article addresses a classical question: Can a machine use language meaningfully and if so, how can this be achieved? The first part of the paper is mainly philosophical.... 相似文献
87.
RJ Jaszczak DR Gilland MW Hanson S Jang KL Greer RE Coleman 《Canadian Metallurgical Quarterly》1993,34(9):1577-1586
We describe a technique using a line source and a rotatable air-copper-lead assembly to acquire gamma transmission computed tomographic (TCT) data for determining attenuation maps to compensate SPECT emission scans. The technique minimizes problems associated with discriminating 99mTc transmission and 201Tl emission photons and requires only a modest increase in total study time. A 99mTc line source and a stacked foil ("multislat") collimator are placed near the focal line of a fan-beam collimator (114 cm focal length) mounted on one detector of a triple-camera SPECT system. We acquired TCT data of plastic rod and anthropomorphic thorax phantoms to investigate the capability of the line source and rotatable air-copper-lead attenuators to determine attenuation maps. The data were acquired with and without 5.4 MBq (145 microCi) of 201Tl placed in the myocardial chamber of the thorax phantom. Phantoms also were scanned using a curved transmission slab source mounted to a parallel-hole collimator. Fan-beam TCT images have improved resolution compared with parallel-beam TCT images. Two patient scans also were performed to evaluate the clinical usefulness of fan-beam TCT. The rotatable air-copper-lead attenuator method eliminates contamination of emission data by transmission photons and reduces spill-over of emission data into the transmission energy window for some cases. Results show the feasibility of using fast, sequential or interlaced transmission scans of a line source within a rotatable air-copper-lead attenuator assembly to obtain accurate attenuation maps for SPECT attenuation compensation. 相似文献
88.
MA Bloomberg HS Jordan KO Angel MH Bailit KJ Goonan J Straus 《Canadian Metallurgical Quarterly》1993,19(12):586-595
This article describes a collaborative effort between a major health care purchaser, three area health maintenance organizations, and a state Medicaid agency to develop clinical indicators as the basis for a comparison database. Some of the difficulties in developing a "common yardstick" of quality and value are candidly discussed. 相似文献
89.
90.
2D Materials: Re Doping in 2D Transition Metal Dichalcogenides as a New Route to Tailor Structural Phases and Induced Magnetism (Adv. Mater. 43/2017) 下载免费PDF全文