全文获取类型
收费全文 | 1191篇 |
免费 | 52篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 14篇 |
综合类 | 2篇 |
化学工业 | 242篇 |
金属工艺 | 17篇 |
机械仪表 | 72篇 |
建筑科学 | 20篇 |
能源动力 | 34篇 |
轻工业 | 64篇 |
水利工程 | 8篇 |
无线电 | 156篇 |
一般工业技术 | 215篇 |
冶金工业 | 314篇 |
原子能技术 | 4篇 |
自动化技术 | 83篇 |
出版年
2024年 | 1篇 |
2023年 | 13篇 |
2022年 | 26篇 |
2021年 | 39篇 |
2020年 | 18篇 |
2019年 | 31篇 |
2018年 | 23篇 |
2017年 | 26篇 |
2016年 | 40篇 |
2015年 | 25篇 |
2014年 | 31篇 |
2013年 | 61篇 |
2012年 | 66篇 |
2011年 | 74篇 |
2010年 | 70篇 |
2009年 | 65篇 |
2008年 | 52篇 |
2007年 | 36篇 |
2006年 | 36篇 |
2005年 | 30篇 |
2004年 | 31篇 |
2003年 | 8篇 |
2002年 | 19篇 |
2001年 | 24篇 |
2000年 | 25篇 |
1999年 | 23篇 |
1998年 | 98篇 |
1997年 | 52篇 |
1996年 | 38篇 |
1995年 | 32篇 |
1994年 | 17篇 |
1993年 | 17篇 |
1992年 | 3篇 |
1991年 | 10篇 |
1990年 | 9篇 |
1989年 | 8篇 |
1988年 | 7篇 |
1987年 | 8篇 |
1986年 | 8篇 |
1985年 | 4篇 |
1983年 | 2篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1977年 | 5篇 |
1976年 | 27篇 |
1975年 | 2篇 |
1973年 | 1篇 |
1955年 | 2篇 |
排序方式: 共有1245条查询结果,搜索用时 15 毫秒
21.
Indicating that CBMC does not satisfy the monotonic property in terms of the number of interactions, Xu and Zhou proposed an augmented definition of CBMC by adopting cut set instead of glue methods. The augmented CBMC clearly satisfies the monotonic property. However, CBMC is designed to overcome the problem with respect to the number of interactions and, therefore, focuses on the interaction pattern, especially, member connectivity. Consequently, it does not make sense to mention the monotonic property of CBMC with respect to interaction number. Moreover, the notion of glue methods allows several interpretations on the design quality of a class. However, that meaningful interpretation is not possible for the augmented definition due to the removal of the notion of glue methods. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
22.
Considering the robustness, stability and reduced volume of data, researchers have focused on using edge information in various
video processing applications including moving object detection, tracking and target recognition. Though the edge information
is more robust compared to intensity, it also exhibits variations in different frames due to illumination change and noise.
In addition to this, the amount of variation varies from edge to edge. Thus, without making use of this variability information,
it is difficult to obtain an optimal performance during edge matching. However, traditional edge pixel-based methods do not
keep structural information of edges and thus they are not suitable to extract and hold this variability information. To achieve
this, we represent edges as segments that make use of the structural and relational information of edges to allow extraction
of this variability information. During edge matching, existing algorithms do not handle the size, positional and rotational
variations to deal with edges of arbitrary shapes. In this paper, we propose a knowledge-based flexible edge matching algorithm
where knowledge is obtained from the statistics on the environmental dynamics, and flexibility is to deal with the arbitrary
shape and the geometric variations of edges by making use of this knowledge. In this paper, we detailed the effectiveness
of the proposed matching algorithm in moving object detection and also indicated its suitability in other applications like
target detection and tracking. 相似文献
23.
JR Bearder VM Frydman P Gaskin IK Hatton WE Harvey J McMillan BO Phinney 《Canadian Metallurgical Quarterly》1976,39(2):178-183
Angiotensin II (A II) and analogues were tested for their ability to restore electrical and mechanical activity to cardiac muscle preparations in which the fast Na+ channels had been inactivated by partial depolarization (22-27 mM K+) or by tetrodotoxin (TTX). The partially depolarized or TTX-blocked preparations were chosen because under these conditions electrical and mechanical responses are primarily Ca2+ -dependent. In depolarized rabbit right atria, A II restored spontaneous mechanical and electrical activity (measured by both intracellular and extracellular recording techniques). The frequency of action potential discharge was concentration-dependent; the threshold concentration of A II was 10(-10) M, the ED50 was 8 X 10(-9) M, and the maximum effect was observed at 5 X 10(-8) M. In contrast, depolarized guinea pig atria were insensitive to A II, Sar1-angiotensin II, and des-Asp1-angiotensin II, even at concentrations as high as 10(-5) M. Rabbit papillary muscle (TTX-blocked), embryonic (18-day) chick heart (partially depolarized) and chick heart reaggregates (TTX-blocked) responded similarly to rabbit atria in that A II (9.6 X 10(-7) M) restored both electrical and mechanical activity. We found that in these preparations the action of A II was unaffected by propranolol (5.0 X 10(-6) M to 5.0 X 10(-5) M) but was blocked by Mn2+ (10(-3) M), D-600 (1 X 10(-7) g/ml) and the specific A II antagonists Sar1-Ala8-angiotensin II (P-113) (5.0 X 10(-5) M) and Sar1-Ile8-angiotensin II (5.28 X 10(-5) M). We conclude that the positive inotropic effect of A II on the myocardium is due to its ability to increase transmembrane ion movements in or through the cell membrane. The ability of Mn2+ and D-600 to block this effect suggests that this ion movement is via the so-called "slow channels." 相似文献
24.
This paper reports a high-sensitivity low-noise capacitive accelerometer system with one micro-g//spl radic/Hz resolution. The accelerometer and interface electronics together operate as a second-order electromechanical sigma-delta modulator. A detailed noise analysis of electromechanical sigma-delta capacitive accelerometers with a final goal of achieving sub-/spl mu/g resolution is also presented. The analysis and test results have shown that amplifier thermal and sensor charging reference voltage noises are dominant in open-loop mode of operation. For closed-loop mode of operation, mass-residual motion is the dominant noise source at low sampling frequencies. By increasing the sampling frequency, both open-loop and closed-loop overall noise can be reduced significantly. The interface circuit has more than 120 dB dynamic range and can resolve better than 10 aF. The complete module operates from a single 5-V supply and has a measured sensitivity of 960 mV/g with a noise floor of 1.08 /spl mu/g//spl radic/Hz in open-loop. This system can resolve better than 10 /spl mu/g//spl radic/Hz in closed-loop. 相似文献
25.
26.
Despite the remarkable progress in cancer treatment up to now, we are still far from conquering the disease. The most substantial change after the malignant transformation of normal cells into cancer cells is the alteration in their metabolism. Cancer cells reprogram their metabolism to support the elevated energy demand as well as the acquisition and maintenance of their malignancy, even in nutrient-poor environments. The metabolic alterations, even under aerobic conditions, such as the upregulation of the glucose uptake and glycolysis (the Warburg effect), increase the ROS (reactive oxygen species) and glutamine dependence, which are the prominent features of cancer metabolism. Among these metabolic alterations, high glutamine dependency has attracted serious attention in the cancer research community. In addition, the oncogenic signaling pathways of the well-known important genetic mutations play important regulatory roles, either directly or indirectly, in the central carbon metabolism. The identification of the convergent metabolic phenotypes is crucial to the targeting of cancer cells. In this review, we investigate the relationship between cancer metabolism and the signal transduction pathways, and we highlight the recent developments in anti-cancer therapy that target metabolism. 相似文献
27.
A total of 165 Staphylococcus aureus strains, isolated from different food samples between 2003 and 2006, were tested for antimicrobial susceptibility. The mecA-positive methicillin-resistant S. aureus (MRSA) strains were further characterized by testing for various virulence genes and by molecular typing with multilocus sequence typing and pulsed-field gel electrophoresis. Of the 165 S. aureus isolates, 150 strains (90.9%) were resistant to at least one antibiotic while no strain was resistant to vancomycin. Four strains were resistant to both oxacillin and cefoxitin and were mecA positive. The mecA-positive MRSA strains were isolated from raw meat and fish samples (two beef samples and two fish samples) and were resistant to β-lactam antibiotics. Based on multilocus sequence typing analysis, the isolates were assigned to sequence type 1 (ST1), ST72, and an undetermined ST (ST72 slv). All four MRSA isolates were shown to be enterotoxigenic. The ST1 MRSA isolate harbored the sea-seh gene combination and the ST72 and ST72 slv MRSA strains harbored the seg-sei and the sea-seg-sei gene combinations, respectively. However, none of the MRSA isolates had the genes for Panton-Valentine leukocidin, toxic shock syndrome toxin 1, and exfoliative toxins. The pulsed-field gel electrophoresis patterns of the ST72 isolates in our study were highly similar, even though they were isolated from food samples in different years and from different regions of Korea. 相似文献
28.
Eun-Sil Kang Da Won Chae Baekjin Kim Young Gyu Kim 《Journal of Industrial and Engineering Chemistry》2012,18(1):174-177
2,5-Dihydroxymethylfuran (DHMF) and 5-hydroxymethylfuranoic acid (HMFA) are the versatile intermediate chemicals of high industrial potential. An efficient preparation of both DHMF and HMFA is reported from biomass-derived HMF via a Cannizzaro reaction using ionic liquids as a reusable reaction solvent under the water-free conditions. The operationally simple and environment-friendly process produces both DHMF and HMFA from HMF consistently in good to high yields up to five runs with the recycled ionic liquid. 相似文献
29.
30.
Wonghil Chang GeumHee Chae So Ra Jang Jihye Shin Byoung Joon Ahn 《Journal of Industrial and Engineering Chemistry》2012,18(2):581-585
Palladium catalysts, Pd/MCM-41 and Pd/SBA-15 were prepared by impregnation of an aqueous solution of [Pd(NH3)4]Cl2 on MCM-41 and SBA-15. Palladium contents of Pd/MCM-41 and Pd/SBA-15 are 8.4% and 8.7%, respectively. It has been shown that these catalysts are very suitable to microwave-assisted Suzuki reactions under solvent-free condition. It is also found that the base additives for this reaction are K2CO3, Cs2CO3 or CsF. Thus, phenylboronic acid and phenyl iodide with Pd/MCM-41 produce biphenyl by microwave irradiation for 10 min in 97.4% yield. Phenyl bromide, instead of phenyl iodide, also proceeds the reaction with phenylboronic acid using Pd/MCM-41 or Pd/SBA-15 yielding biphenyl by microwave irradiation for 10 min in excellent yield. Whereas the reaction of phenyl chloride with phenylboronic acid gives poor yield in same condition. Various aryl iodides and aryl bromides are tested. In this paper our recent results of microwave-assisted Suzuki reaction using Pd/MCM-41 and Pd/SBA-15 under solvent-free condition are described. 相似文献