全文获取类型
收费全文 | 47596篇 |
免费 | 3104篇 |
国内免费 | 1354篇 |
专业分类
电工技术 | 1739篇 |
技术理论 | 1篇 |
综合类 | 2037篇 |
化学工业 | 8694篇 |
金属工艺 | 1909篇 |
机械仪表 | 2194篇 |
建筑科学 | 3957篇 |
矿业工程 | 696篇 |
能源动力 | 1434篇 |
轻工业 | 3128篇 |
水利工程 | 677篇 |
石油天然气 | 1940篇 |
武器工业 | 214篇 |
无线电 | 5063篇 |
一般工业技术 | 6870篇 |
冶金工业 | 4456篇 |
原子能技术 | 498篇 |
自动化技术 | 6547篇 |
出版年
2024年 | 113篇 |
2023年 | 522篇 |
2022年 | 903篇 |
2021年 | 1399篇 |
2020年 | 1051篇 |
2019年 | 939篇 |
2018年 | 1096篇 |
2017年 | 1186篇 |
2016年 | 1225篇 |
2015年 | 1417篇 |
2014年 | 1912篇 |
2013年 | 2779篇 |
2012年 | 2704篇 |
2011年 | 3130篇 |
2010年 | 2549篇 |
2009年 | 2496篇 |
2008年 | 2570篇 |
2007年 | 2526篇 |
2006年 | 2427篇 |
2005年 | 2216篇 |
2004年 | 1652篇 |
2003年 | 1430篇 |
2002年 | 1477篇 |
2001年 | 1143篇 |
2000年 | 1211篇 |
1999年 | 1249篇 |
1998年 | 1251篇 |
1997年 | 1025篇 |
1996年 | 994篇 |
1995年 | 893篇 |
1994年 | 711篇 |
1993年 | 657篇 |
1992年 | 476篇 |
1991年 | 310篇 |
1990年 | 373篇 |
1989年 | 290篇 |
1988年 | 244篇 |
1987年 | 211篇 |
1986年 | 162篇 |
1985年 | 191篇 |
1984年 | 175篇 |
1983年 | 117篇 |
1982年 | 100篇 |
1981年 | 84篇 |
1980年 | 65篇 |
1979年 | 65篇 |
1978年 | 48篇 |
1977年 | 38篇 |
1976年 | 49篇 |
1974年 | 31篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
161.
详细介绍了进口的VPSA制氧装置的流程特点、工艺参数及主要设备的配置。实际运转证明 ,该制氧装置具有运行可靠、启动时间短、部分负荷性能优越、负荷转换速度快等优点 ,能满足金隆铜业有限公司的实际生产要求。 相似文献
162.
Mark O'brien 《Information & Communications Technology Law》2006,15(3):259-273
Internet pornography, especially child pornography, has been a significant concern in British society for several years. This article seeks to examine the prevalence and impact of such material, the way public concern has developed, and media and legislative reactions to this concern. It suggests that a more rational debate of the actual and likely dangers in this sphere is necessary in order both to protect and serve the interests of justice. 相似文献
163.
Dandeneau Stéphane D.; Baldwin Mark W.; Baccus Jodene R.; Sakellaropoulo Maya; Pruessner Jens C. 《Canadian Metallurgical Quarterly》2007,93(4):651
Personality processes relating to social perception have been shown to play a significant role in the experience of stress. In 5 studies, the authors demonstrate that early stage attentional processes influence the perception of social threat and modify the human stress response. The authors first show that cortisol release in response to a stressful situation correlates with selective attention toward social threat. Second, the authors show in 2 laboratory studies that this attentional pattern, most evident among individuals with low self-esteem, can be modified with a repetitive training task. Next, in a field study, students trained to modify their attentional pattern to reduce vigilance for social threat showed lower self-reported stress related to their final exam. In a final field study with telemarketers, the attentional training task led to increased self-esteem, decreased cortisol and perceived stress responses, higher confidence, and greater work performance. Taken together, these results demonstrate the impact of antecedent-focused strategies on the late-stage consequences of social stress. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
164.
165.
This article presents a detailed investigation on the influence of the phosphorus element upon the laser sintering of a multicomponent
Cu-based metal powder system consisting of Cu, Cu-10Sn, and Cu-8.4P. Powder systems containing 0, 10, 15, and 20 wt pct CuP
were sintered in atmosphere at room temperature using the following optimal processing parameters: laser power of 350 W, scan
speed of 0.04 m/s, scan line spacing of 0.15 mm, and layer thickness of 0.25 mm. It was found that the relative density of
the sintered sample with 15 wt pct CuP increased by 24,4 pct as compared with the sample without phosphorus addition. A further
increase in the CuP content (≥20 wt pct), however, resulted in a poor densification with a serious delamination. The exact
metallurgical roles of the phosphorus element in the laser sintering process were addressed as follows. First, the phosphorus
could prevent the sintering system from oxidation by forming CuPO3, thereby improving the wetting characteristics and the sintering kinetics. Second, the phosphorus could decrease the surface
tension of molten materials, leading to a successive transition from highly discontinuous sintered tracks to fairly coherent
ones with increasing the phosphorus content. Third, the phosphorus could lower the melt viscosity, thereby improving the microstructural
homogeneity of the laser-sintered samples. 相似文献
166.
Two experiments involving 99 undergraduate participants sought to examine the influence of mood states on encoding speed within lexical decision and pronunciation tasks. Mood states were measured naturalistically in Experiment 1 and manipulated in Experiment 2. Stimuli consisted of nouns representing useful (e.g., food) and nonuseful (e.g., lint) objects. Mood states had no implications for initial encoding speed. However, when the same words were presented a 2nd time (i.e., repeated), happy individuals displayed a tendency to encode useful words faster than nonuseful ones. Thus, mood states influenced repetition priming on the basis of stimulus valence. The authors propose that happiness sensitizes individuals to useful or rewarding objects, which in turn creates a stronger memory trace for such stimuli in the future. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
167.
168.
Effect of Cerium on Expression and Activity of MMP-9 from Human Carcinoma of Bladder Cell Line 总被引:1,自引:0,他引:1
Rareearthshaveledtowidespreadinterestsinlifescience ,whilethescientistsdoresearchesdeeplyinmedicalandbiochemicalfields .Rareearthsplaypotentialrolesininhibitingcancer ,andalargenum berofscientistsdedicatethemselvestoit[1] .Thema trixmetalloproteinases (MMPs)areafamilyofatleast1 7humanzinc dependentendopeptidasesthatareca pableofdegradingalmostallextracellularmatrix(ECM)components .Theyareessentialinmanyphys iologicalprocessesandseveralpathologicalconditions ,suchastumorprogression .MMPsare… 相似文献
169.
Mark S. MACGREGOR Sue J. CARR 《Hemodialysis international. International Symposium on Home Hemodialysis》2007,11(Z2):S1-S4
Hemodialysis was a neglected aspect of nephrology in the UK. At the request of the Renal Association, the first UK Haemodialysis Masterclass was organized in 2007. The articles in this supplement arose from that meeting. Here, an overview of UK hemodialysis services and nephrology training is presented as background. Government‐funded dialysis should be provided to all UK citizens who require it. In 2005, there were 17,645 patients receiving hemodialysis, 5057 on peritoneal dialysis and 19,074 with kidney transplants, looked after by 359 nephrologists working in 73 National Health Service renal units. Renal replacement therapy incidence and prevalence remain comparatively low, at 108 and 694 per million population, respectively. Whether this represents inadequate provision or genuinely lower need remains unclear. The Renal Association sets clinical practice guidelines for dialysis, and audits performance via the UK Renal Registry. Postgraduate medical education is undergoing radical change in the UK. This is driven by the reduction in trainee doctors' working hours to 48 hr/week (mandated by the European Working Time Directive), and the governments' wish to reduce the duration of training, but also by a desire to formalize training, Our challenge is to continue to produce talented clinical nephrologists educated in breadth and depth, despite the reduced emphasis on clinical experience and omission of period of scientific research. The future for hemodialysis services in the UK is, however, promising with an expansion in the number of specialists and dialysis centers, and a growing interest in dialysis practice and research. 相似文献
170.
Mark S. MACGREGOR 《Hemodialysis international. International Symposium on Home Hemodialysis》2007,11(Z2):S10-S16
Survival of patients on hemodialysis remains poor, but the benefits of increasing urea clearance have probably been maximized within our current treatment schedules. Long dialysis sessions (8 hr) produce impressive outcomes, with mortality 53% to 55% lower than conventional schedules. Even increasing from 4 to 5 hr may improve survival. Increased frequency of dialysis (6 times weekly) produces impressive reductions in left ventricular mass and could conceivably be implemented in‐center. Preliminary data suggest a 61% reduction in mortality with increased frequency. Nightly dialysis combines longer sessions with increased frequency and has produced remarkable clinical gains in blood pressure, left ventricular mass, serum phosphate, and sleep apnea. However, the data are mainly from case series and impact on mortality remains unknown. Expansion of home hemodialysis would be necessary for this modality to grow. Convective therapies remove middle molecules more effectively, and observational data suggest hemodiafiltration has the potential to improve mortality by 35% to 36%. Hemodiafiltration has the advantage of being relatively easy to implement. The uremic milieu is complex and further investigation of the underlying pathophysiology is needed to inform future dialysis interventions. The survival data above are from observational studies, and hence benefits are likely to be exaggerated. Randomized trials of dialysis interventions are desperately needed. They remain difficult to perform, because of the complexity of both the patient population and the interventions, and because of limited available funding. 相似文献