全文获取类型
收费全文 | 91篇 |
免费 | 3篇 |
专业分类
电工技术 | 2篇 |
综合类 | 1篇 |
化学工业 | 13篇 |
金属工艺 | 2篇 |
机械仪表 | 1篇 |
能源动力 | 4篇 |
轻工业 | 8篇 |
无线电 | 22篇 |
一般工业技术 | 15篇 |
冶金工业 | 18篇 |
原子能技术 | 1篇 |
自动化技术 | 7篇 |
出版年
2024年 | 1篇 |
2023年 | 1篇 |
2022年 | 2篇 |
2021年 | 4篇 |
2020年 | 1篇 |
2017年 | 4篇 |
2016年 | 2篇 |
2015年 | 4篇 |
2013年 | 2篇 |
2012年 | 4篇 |
2011年 | 1篇 |
2010年 | 2篇 |
2009年 | 6篇 |
2008年 | 3篇 |
2007年 | 3篇 |
2006年 | 3篇 |
2005年 | 1篇 |
2004年 | 6篇 |
2003年 | 3篇 |
2002年 | 1篇 |
2001年 | 1篇 |
1999年 | 2篇 |
1998年 | 8篇 |
1997年 | 4篇 |
1996年 | 2篇 |
1995年 | 3篇 |
1994年 | 1篇 |
1992年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1972年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有94条查询结果,搜索用时 15 毫秒
81.
Angiotensin II (AngII), a circulating vasoactive peptide, interacts with specific membrane-bound receptors on the target tissues (vessels, kidneys and adrenal gland). Using new pharmacological tools and molecular cloning, these receptors have been classified in two types, called AT1 et AT2, whereas two subtypes, called AT1A et AT1B, have been identified for the rodent AT1 receptors, but not in humans. All these receptors present a seven hydrophobic transmembrane domain structure, which is classical for G protein coupled receptors. The interspecies molecular homology of these AngII receptors is high (> 90 per cent identity) within the same type of receptor, but is rather low (approximately 35 per cent identity) between the two types of receptors. The AT1 receptors are responsible for most of the AngII physiological actions and are coupled to a Gq protein, which activates a phospholipase C producing second messengers which activate protein kinases C and mobilize calcium intracellular stores. More recently, a strong interaction of this receptor has been demonstrated with the signalling pathways of the tyrosine kinases. The molecular mechanisms and the physiological importance of these interactions remain to be elucidated. The intracellular signalling (Gi coupling and tyrosine phosphatase activation) and the physiological actions (cellular differentiation, apoptosis) of the AT2 receptors are more controversial. 相似文献
82.
83.
JA Gomes MR Dana HS Dua MB Goren PR Laibson EJ Cohen 《Canadian Metallurgical Quarterly》1995,14(5):457-462
A 3-year retrospective study on the risk factors of positive donor rim cultures in penetrating keratoplasty was performed. One thousand and ninety-seven consecutive donor rim cultures were reviewed from the period between June 1990 and October 1993 to determine the rate of culture positivity. The sex, age, diabetes status, use of respirator at time of death, cause of death, harvesting technique, storage time, and corneal storage medium utilized for the donors with positive donor rim culture were compared to those for 100 randomly selected culture negative donor controls. Logistic analysis was performed to eliminate confounding effects. Forty-six of the 1,097 (4.19%) donor rim cultures were positive. We found an association between the in situ technique for donor harvesting and culture negativity (p = 0.03). None of the other donor characteristics was associated with culture positivity. None of the 46 recipients who received the positive culture corneas developed endophthalmitis. In situ cornea harvesting promotes less contamination than enucleation and enriched gentamicin and streptomycin storage medium may further decrease donor rim culture positivity. 相似文献
84.
85.
86.
Dua D. Dambhare S. Gajbhiye R.K. Soman S.A. 《Power Delivery, IEEE Transactions on》2008,23(4):1812-1820
This paper addresses various aspects of optimal phasor measurement unit (PMU) placement problem. We propose a procedure for multistaging of PMU placement in a given time horizon using an integer linear programming (ILP) framework. Hitherto, modeling of zero injection constraints had been a challenge due to the intrinsic nonlinearity associated with it. We show that zero injection constraints can also be modeled as linear constraints in an ILP framework. Minimum PMU placement problem has multiple solutions. We propose two indices, viz, BOI and SORI, to further rank these multiple solutions, where BOI is bus observability index giving a measure of number of PMUs observing a given bus and SORI is system observability redundancy index giving sum of all BOI for a system. Results on IEEE 118 bus system have been presented. Results indicate that: (1) optimal phasing of PMUs can be computed efficiently; (2) proposed method of modeling zero injection constraints improve computational performance; and (3) BOI and SORI help in improving the quality of PMU placement. 相似文献
87.
Dua R Beetner DG Stoecker WV Wunsch DC 《IEEE transactions on bio-medical engineering》2004,51(1):66-71
Variations in electrical impedance over frequency might be used to distinguish basal cell carcinoma (BCC) from benign skin lesions, although the patterns that separate the two are nonobvious. Artificial neural networks (ANNs) may be good pattern classifiers for this application. A preliminary study to show the potential of neural networks to distinguish benign from malignant skin lesions using electrical impedance is presented. Electrical impedance was measured in vivo from 1 kHz to 1 MHz at five virtual depths on 18 BCC and 16 benign or premalignant lesions. A feed-forward neural network was trained using back propagation to classify these lesions. Two methods of preprocessing were used to account for the impedance of normal skin and the size of the lesion, one based on estimating the impedance of the lesion relative to adjacent normal skin and one based on estimating the impedance of the lesion independent of size or surrounding normal skin. Neural networks were able to classify measurements in a test set with 100% accuracy for the first preprocessing technique and 85% accuracy for the second. These results indicate electrical impedance may be a promising clinical diagnostic tool for basal cell carcinoma or other forms of skin cancer. 相似文献
88.
Singh MK Titus E Tyagi PK Palnitkar U Misra DS Roy M Dua AK Cojocaru CS Le Normand F 《Journal of nanoscience and nanotechnology》2003,3(1-2):165-170
Multiwalled carbon nanotubes are grown by microwave plasma chemical vapor deposition with CH4 and H2 as precursor gases. Ni and Ni/Pt electroplated layers are used as catalysts for the synthesis of the tubes. We observe that a very efficient filling of the tubes takes place with Ni. In some cases Ni/Pt filling is also observed inside the tubes. High-resolution transmission electron microscopy (HRTEM) studies, coupled with energy-dispersive X-ray analyses of the tubes, indicate Ni nanorods with a highly symmetrical cylindrical structure. The diameter of the cylindrical nanorods is on the order of 40 nm, and their length is 660 nm. The nano area diffraction pattern of the nanorods reveals the cubic structure of nickel, and electron diffraction spots corresponding to (111), (200), (220) planes are evident. The lattice constant of Ni measured from the diffraction spots was found to be 0.347 +/- 0.0013 nm. This should be compared with 0.352 nm, the value of "a" in bulk Ni. The decrease in the lattice constant may be due to the strain experienced inside the tubes. Raman spectroscopy shows the typical signature of the tangential breathing mode present in the tubes at 1580 cm-1 that shifts to a new position when the C12 is replaced by 13C. The shift, however, is too small and is difficult to explain on the basis of mass difference. HRTEM experiments indicate the presence of Ni3C in the samples dominantly in the interfacial region. 相似文献
89.
VA Bondarenko M Desai S Dua M Yamazaki RH Amin KK Yousif T Kinumi M Ohashi N Komori H Matsumoto KW Jackson F Hayashi J Usukura VM Lipkin A Yamazaki 《Canadian Metallurgical Quarterly》1997,272(25):15856-15864
Interaction between the gamma subunit (Pgamma) of cGMP phosphodiesterase and the alpha subunit (Talpha) of transducin is a key step for the regulation of cGMP phosphodiesterase in retinal rod outer segments. Here we have utilized a combination of specific modification by an endogenous enzyme and site-directed mutagenesis of the Pgamma polycationic region to identify residues required for the interaction with Talpha. Pgamma, free or complexed with the alphabeta subunit (Palphabeta) of cGMP phosphodiesterase, was specifically radiolabeled by prewashed rod membranes in the presence of [adenylate-32P]NAD. Identification of ADP-ribose in the radiolabeled Pgamma and radiolabeling of arginine-replaced mutant forms of Pgamma indicate that both arginine 33 and arginine 36 are similarly ADP-ribosylated by endogenous ADP-ribosyltransferase, but only one arginine is modified at a time. Pgamma complexed with Talpha (both GTP- and GDP-bound forms) was not ADP-ribosylated; however, agmatine, which cannot interact with Talpha, was ADP-ribosylated in the presence of Talpha, suggesting that a Pgamma domain containing these arginines is masked by Talpha. A Pgamma mutant (R33,36K), as well as wild type Pgamma, inhibited both GTP hydrolysis of Talpha and GTP binding to Talpha. Moreover, GTP-bound Talpha activated Palphabeta that had been inhibited by R33,36K. However, another Pgamma mutant (R33,36L) could not inhibit these Talpha functions. In addition, GTP-bound Talpha could not activate Palphabeta inhibited by R33,36L. These results indicate that a Pgamma domain containing these arginines is required for its interaction with Talpha, but not with Palphabeta, and that positive charges in these arginines are crucial for the interaction. 相似文献
90.
Next-generation cellular wireless communication networks aim to provide a variety of quality-of-service (QoS)-sensitive packet-based services to downlink users. Included among these are real-time multimedia services, which have stringent delay requirements. Downlink packet scheduling at the base station plays a key role in efficiently allocating system resources to meet the desired level of QoS for various users. In this paper, we employ dynamic programming (DP) to study the design of a downlink packet scheduler capable of supporting real-time multimedia applications. Under well-justified modeling reductions, we extensively characterize structural properties of the optimal control associated with the DP problem. We leverage intuition gained from these properties to propose a heuristic scheduling policy, namely, Channel-Aware Earliest Due Date (CA-EDD), which is based on a "quasi- static" approach to scheduling. The per-time-slot implementation complexity of CA-EDD is only O(K) for a system with K downlink users. Experimental results show that CA-EDD delivers up to 50 percent of performance gains over benchmark schedulers. CA-EDD achieves these performance gains by using channel and deadline information in conjunction with application layer information (relative importance of packets) in a systematic and unified way for scheduling. 相似文献