全文获取类型
收费全文 | 682篇 |
免费 | 8篇 |
专业分类
电工技术 | 5篇 |
化学工业 | 65篇 |
金属工艺 | 10篇 |
机械仪表 | 17篇 |
建筑科学 | 23篇 |
能源动力 | 10篇 |
轻工业 | 34篇 |
水利工程 | 16篇 |
石油天然气 | 9篇 |
无线电 | 68篇 |
一般工业技术 | 83篇 |
冶金工业 | 309篇 |
原子能技术 | 4篇 |
自动化技术 | 37篇 |
出版年
2022年 | 5篇 |
2021年 | 3篇 |
2020年 | 5篇 |
2019年 | 6篇 |
2018年 | 9篇 |
2017年 | 5篇 |
2016年 | 3篇 |
2015年 | 4篇 |
2014年 | 6篇 |
2013年 | 21篇 |
2012年 | 15篇 |
2011年 | 16篇 |
2010年 | 23篇 |
2009年 | 12篇 |
2008年 | 25篇 |
2007年 | 17篇 |
2006年 | 14篇 |
2005年 | 15篇 |
2004年 | 16篇 |
2003年 | 13篇 |
2002年 | 11篇 |
2001年 | 18篇 |
2000年 | 16篇 |
1999年 | 22篇 |
1998年 | 50篇 |
1997年 | 57篇 |
1996年 | 39篇 |
1995年 | 27篇 |
1994年 | 24篇 |
1993年 | 16篇 |
1992年 | 9篇 |
1991年 | 7篇 |
1990年 | 16篇 |
1989年 | 12篇 |
1988年 | 15篇 |
1987年 | 11篇 |
1986年 | 12篇 |
1985年 | 4篇 |
1984年 | 12篇 |
1983年 | 7篇 |
1982年 | 7篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1977年 | 11篇 |
1976年 | 19篇 |
1974年 | 3篇 |
1965年 | 3篇 |
1938年 | 2篇 |
1937年 | 2篇 |
排序方式: 共有690条查询结果,搜索用时 15 毫秒
1.
ABSTRACT Contact tracing is widely considered as an effective procedure in the fight against epidemic diseases. However, one of the challenges for technology based contact tracing is the high number of false positives, questioning its trust-worthiness and efficiency amongst the wider population for mass adoption. To this end, this paper proposes a novel, yet practical smartphone-based contact tracing approach, employing WiFi and acoustic sound for relative distance estimate, in addition to the air pressure and the magnetic field for ambient environment matching. We present a model combining six smartphone sensors, prioritising some of them when certain conditions are met. We empirically verified our approach in various realistic environments to demonstrate an achievement of up to 95% fewer false positives, and 62% more accurate than Bluetooth-only system. To the best of our knowledge, this paper was one of the first work to propose a combination of smartphone sensors for contact tracing. 相似文献
2.
This report compares the enterococci count on samples obtained with Azide NutriDisk (AND) (sterile, dehydrated culture medium) and Slanetz and Bartley (SB) medium when exposed to a variable in incubation time and temperature. Three experiments were performed to examine the recovery of enterococci on AND and SB media using membrane filtration with respect to: (a) incubation time; (b) incubation temperature; and (c) a combination of the two. Presumptive counts were observed at 37, 41, 46 and 47 degrees C and at 20, 24, 28 and 48 h. These were compared to AWWA standard method 9230 C (44 degrees C, 44 h). Samples were confirmed using Kanamycin Aesculin Azide (KAA) agar. Friedman's ANOVA and Students t-test analysis indicated higher enumeration of enterococci when grown on AND (p = 0.45) than SB (p = < 0.001) at all temperatures with a survival threshold at 47 degrees C. Significant results for AND medium were noted at 20 h (p = 0.021), 24 h (p = 0.278) and 28 h (p = 0.543). The study concluded that the accuracy of the AND medium at a greater time and temperature range provided flexibility in incubator technology making it an appropriate alternative to SB medium for monitoring drinking water using field testing kits in developing countries. 相似文献
3.
Reading Motivation: Multidimensional and Indeterminate. 总被引:1,自引:0,他引:1
The Motivations for Reading Questionnaire (MRQ) contains 54 items that are posited to tap 11 dimensions of reading motivation. The structural validity of the MRQ was investigated with 2 samples: (a) 328 students in Grades 3-5 from 2 suburban mid-Atlantic elementary schools and (b) 735 students in Grades 3-5 in 2 suburban southwestern elementary schools. With confirmatory factor analyses (CFAs), the theoretical 11-factor structure did not adequately fit the data in either sample. Subsequently, exploratory factor analyses found 8 factors for each sample with 6 factors defined by only 3 or 4 common items. However, a double CFA cross-validation found an inadequate fit for both samples. Given these results, the authors suggest that the MRQ be revised. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
4.
KJ Shon M Grilley R Jacobsen GE Cartier C Hopkins WR Gray M Watkins DR Hillyard J Rivier J Torres D Yoshikami BM Olivera 《Canadian Metallurgical Quarterly》1997,36(31):9581-9587
A paralytic peptide, psi-conotoxin Piiie has been purified and characterized from Conus purpurascens venom. Electrophysiological studies indicate that the peptide inhibits the nicotinic acetylcholine receptor (nAChR). However, the peptide does not block the binding of alpha-bungarotoxin, a competitive nAChR antagonist. Thus, psi-conotoxin Piiie appears to inhibit the receptor at a site other than the acetylcholine-binding site. As ascertained by sequence analysis, mass spectrometry, and chemical synthesis, the peptide has the following covalent structure: HOOCCLYGKCRRYOGCSSASCCQR* (O = 4-trans hydroxyproline; * indicates an amidated C-terminus). The disulfide connectivity of the toxin is unrelated to the alpha- or the alphaA-conotoxins, the Conus peptide families that are competitive inhibitors of the nAChR, but shows homology to the mu-conotoxins (which are Na+ channel blockers). 相似文献
5.
Comments on the proposal by L. H. Levy et al (see record 1984-27507-001) for a new charter for clinical psychology—human services psychology. Current trends suggest that both clinical and counseling psychology are becoming eclectic and health oriented. Clinical psychology appears to be becoming more involved in community psychology and to be tempering its remedial role with the preventive role. Counseling psychology appears to be becoming less involved in its vocational and preventive roles and more involved in the remedial role. It is concluded that clinical and counseling psychology have come to be increasingly similar and could be integrated into a human services psychology. (38 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
6.
LA Knapp E Lehmann L Hennes ME Eberle DI Watkins 《Canadian Metallurgical Quarterly》1997,50(2):170-177
Skeletal development of transgenic mice with a type II collagen mutation was analyzed and compared with wild-type littermates. The single base substitution in Col2a1 resulted in a glycine to serine mutation within the helical domain and corresponded to one previously identified in a patient with the lethal human chondrodysplasia, hypochondrogenesis (Horton et al. [1992] Proc. Natl. Acad. Sci. U.S.A. 89:4583-4587). Skeletal staining of embryos from 14.5 through 18.5 days of gestation demonstrated a dwarf phenotype in the transgenic embryos, most notably short limb bones and vertebral column that was first detected at 15.5 days post-coitus. In addition to the reduced length, the extent of ossification was less in the transgenic mice. The architecture of the long bone growth plate was abnormal in the transgenic tissue, in particular there was no discernible proliferative zone. There were few stacks of characteristically flattened cells and the overall length of the growth plate in the mutant embryos was reduced. At the ultrastructural level, there were fewer collagen fibrils present in the transgenic mouse cartilage compared to that of wild-type littermates. Ultrastructural localization of collagen types II, IX and XI revealed a similar pattern between the transgenic and wild-type pups, suggesting that the collagen fibrils present in the matrix of littermates with both phenotypes had a similar composition. Skeletal analysis and cartilage histochemistry indicated that effect of the type II collagen mutation was to reduce the density of the collagen fibrils within the cartilage matrix which was associated with delayed bone formation and resulted in a short-limbed phenotype. 相似文献
7.
8.
Capacitor voltage balancing in multilevel flying capacitor inverters by rule-based switching pattern selection 总被引:1,自引:0,他引:1
A rule-based scheme is investigated for capacitor voltage balancing in a multilevel flying capacitor inverter (MFCI). Without using voltage feedback, the scheme determines the best switching pattern for maintaining nil mean current in all capacitors, hence minimising the capacitor voltage fluctuation. The method is developed to work with the selective harmonic elimination (SHE) technique for sinusoidal voltage generation applied to control static VAR compensators. The method has been designed using a four-cell five-level MFCI as an example. The selected pattern has been shown to give superior performance in load-voltage total-harmonies distortion level and mean capacitor voltage fluctuation. The method is validated experimentally for this form of MFCI 相似文献
9.
10.
On-Chip Optical Technology in Future Bus-Based Multicore Designs 总被引:1,自引:0,他引:1
Kirman N. Kirman M. Dokania R.K. Martinez J.F. Apsel A.B. Watkins M.A. Albonesi D.H. 《Micro, IEEE》2007,27(1):56-66
This work investigates the integration of CMOS-compatible optical technology to on-chip coherent buses for future CMPs. The analysis results in a hierarchical optoelectrical bus that exploits the advantages of optical technology while abiding by projected limitations. This bus achieves significant performance improvement for high-bandwidth applications relative to a state-of-the-art fully electrical bus 相似文献