全文获取类型
收费全文 | 1311篇 |
免费 | 18篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 35篇 |
化学工业 | 80篇 |
金属工艺 | 11篇 |
机械仪表 | 6篇 |
建筑科学 | 24篇 |
能源动力 | 5篇 |
轻工业 | 40篇 |
水利工程 | 1篇 |
无线电 | 35篇 |
一般工业技术 | 83篇 |
冶金工业 | 971篇 |
自动化技术 | 39篇 |
出版年
2023年 | 8篇 |
2022年 | 7篇 |
2021年 | 6篇 |
2020年 | 3篇 |
2017年 | 6篇 |
2016年 | 12篇 |
2015年 | 14篇 |
2014年 | 9篇 |
2013年 | 18篇 |
2012年 | 12篇 |
2011年 | 16篇 |
2010年 | 16篇 |
2009年 | 15篇 |
2008年 | 7篇 |
2007年 | 11篇 |
2006年 | 8篇 |
2005年 | 6篇 |
2004年 | 16篇 |
2003年 | 11篇 |
2002年 | 12篇 |
2001年 | 5篇 |
2000年 | 23篇 |
1999年 | 38篇 |
1998年 | 331篇 |
1997年 | 175篇 |
1996年 | 115篇 |
1995年 | 53篇 |
1994年 | 52篇 |
1993年 | 55篇 |
1992年 | 15篇 |
1991年 | 14篇 |
1990年 | 17篇 |
1989年 | 13篇 |
1988年 | 14篇 |
1987年 | 15篇 |
1986年 | 7篇 |
1985年 | 14篇 |
1984年 | 4篇 |
1983年 | 7篇 |
1982年 | 11篇 |
1981年 | 5篇 |
1980年 | 13篇 |
1978年 | 5篇 |
1977年 | 26篇 |
1976年 | 65篇 |
1975年 | 2篇 |
1973年 | 2篇 |
1972年 | 4篇 |
1969年 | 2篇 |
1955年 | 2篇 |
排序方式: 共有1330条查询结果,搜索用时 15 毫秒
41.
T. Meissner S. K. Goh J. Haase B. Meier D. Rybicki P. L. Alireza 《Journal of Low Temperature Physics》2010,159(1-2):284-287
A novel approach that uses radio-frequency microcoils in the high-pressure region of anvil cells with Nuclear Magnetic Resonance (NMR) experiments is described. High-sensitivity Al NMR data at 70 kbar for Al metal are presented for the first time. An expected decrease in the Al Knight shift at 70 kbar is observed, as well as an unexpected change in the local charge symmetry at the Al nucleus. The latter is not predicted by chemical structure analysis under high pressure. 相似文献
42.
43.
Intestinal epithelial cells respond to Salmonella typhimurium by internalizing this pathogen and secreting, in a polarized manner, an array of chemokines which direct polymorphonuclear leukocyte (PMN) movement. Notably, interleukin-8 (IL-8) is secreted basolaterally and directs PMN through the lamina propria, whereas pathogen-elicited epithelial chemoattractant (PEEC) is secreted apically and directs PMN migration across the epithelial monolayer to the intestinal lumen. While most studies of S. typhimurium pathogenicity have focused on the mechanism by which this bacterium invades its host, the enteritis characteristically associated with salmonellosis appears to be more directly attributable to the PMN movement that occurs in response to this pathogen. Therefore, we sought to better understand the relationship between S. typhimurium invasion and epithelial promotion of PMN movement. First, we investigated whether S. typhimurium becoming intracellular was necessary or sufficient to induce epithelial promotion of PMN movement. Blocking S. typhimurium invasion by preventing, with cytochalasin D, the epithelial cytoskeletal rearrangements which mediate internalization did not reduce the epithelial promotion of PMN movement. Conversely, bacterial attainment of an intracellular position was not sufficient to induce model epithelia to direct PMN transmigration, since neither basolateral invasion by S. typhimurium nor apical internalization of an invasion-deficient mutant (achieved by inducing membrane ruffling with epidermal growth factor) induced this epithelial cell response. These results indicate that specific interactions between the apical surface of epithelial cells and S. typhimurium, rather than simply bacterial invasion, mediate the epithelial direction of PMN transmigration. To further investigate the means by which S. typhimurium induces epithelia to direct PMN movement, we investigated whether the same signaling pathways regulate secretion of IL-8 and PEEC. IL-8 secretion, but not PEEC secretion, was activated by phorbol myristate acetate and blocked by an inhibitor (mg-132) of the proteosome which mediates NF-kappabeta activation. Further, secretion of IL-8, but not PEEC, was activated by an entry-deficient (HilDelta) S. typhimurium mutant or by basolateral invasion of a wild-type strain. Together, these results indicate that distinct signaling pathways mediate S. typhimurium invasion, induction of IL-8 secretion, and induction of PEEC secretion in model intestinal epithelia. 相似文献
44.
Expertise-based peer selection in Peer-to-Peer networks 总被引:1,自引:0,他引:1
45.
L Zhang MJ Dresser AT Gray SC Yost S Terashita KM Giacomini 《Canadian Metallurgical Quarterly》1997,51(6):913-921
OBJECTIVE: The triglyceride-lowering effects of omega-3 fats and HDL cholesterol-raising effects of exercise may be appropriate management for dyslipidemia in NIDDM. However, fish oil may impair glycemic control in NIDDM. The present study examined the effects of moderate aerobic exercise and the incorporation of fish into a low-fat (30% total energy) diet on serum lipids and glycemic control in dyslipidemic NIDDM patients. RESEARCH DESIGN AND METHODS: In a controlled, 8-week intervention, 55 sedentary NIDDM subjects with serum triglycerides > 1.8 mmol/l and/or HDL cholesterol < 1.0 mmol/l were randomly assigned to a low-fat diet (30% daily energy intake) with or without one fish meal daily (3.6 g omega-3/day) and further randomized to a moderate (55-65% VO2max) or light (heart rate < 100 bpm) exercise program. An oral glucose tolerance test (75 g), fasting serum glucose, insulin, lipids, and GHb were measured before and after intervention. Self-monitoring of blood glucose was performed throughout. RESULTS: In the 49 subjects who completed the study, moderate exercise improved aerobic fitness (VO2max) by 12% (from 1.87 to 2.07 l/min, P = 0.0001). Fish consumption reduced triglycerides (0.80 mmol/l, P = 0.03) and HDL3 cholesterol (0.05 mmol/l, P = 0.02) and increased HDL2 cholesterol (0.06 mmol/l, P = 0.01). After adjustment for age, sex, and changes in body weight, fish diets were associated with increases in GHb (0.50%, P = 0.05) and self-monitored glucose (0.57 mmol/l, P = 0.0002), which were prevented by moderate exercise. CONCLUSIONS: A reduced fat diet incorporating one daily fish meal reduces serum triglycerides and increases HDL2 cholesterol in dyslipidemic NIDDM patients. Associated deterioration in glycemic control can be prevented by a concomitant program of moderate exercise. 相似文献
46.
As we reflect on the concept of critical thinking in perioperative nursing practice, we should ask ourselves whether we think critically. If not, we must learn the principles of critical thinking and apply them in our clinical practice settings. Our perioperative nurse managers and directors must demonstrate critical thinking in leading other nurses in the delivery of quality, cost-effective, service-oriented patient care. They also must identify peers who use critical thinking skills to support and sustain them in their quest. 相似文献
47.
48.
The use of piezo actuators in machine tools is a current topic. There are many research works which show the advantages of
this kind of actuators in various fields around machining. In this paper an active work piece holder is presented, which is
designed for reducing the dynamic displacement between the tool and the work piece relatively. The paper shows the design
process for the fixture, the finite element analysis of the mechanical parts and the actuators. Also a specially designed
power amplifier is presented which fits best to the needs of voltage and frequency range of the active work piece holder.
First experimental results are shown. 相似文献
49.
50.
The permeation behaviour of different types of adhesives (urea-formaldehyde resin, dispersion glue (PVA) and Polyurethane) was investigated by light microscopy, scanning electron microscopy and neutron radiography. Clear differences in the permeation behaviour of the adhesives could be determined. Urea resin showed under the chosen conditions the strongest permeation of wood. The glue allocation was quantified and the permeation visualised by means of neutron radiography. By this a differentiation between wood and the glue joint was possible. The penetration depth of the glue was conspicuously different between spring wood and late wood areas. 相似文献