首页 | 官方网站   微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   687篇
  免费   35篇
  国内免费   3篇
工业技术   725篇
  2022年   10篇
  2021年   8篇
  2020年   7篇
  2019年   9篇
  2018年   11篇
  2017年   6篇
  2016年   15篇
  2015年   18篇
  2014年   15篇
  2013年   31篇
  2012年   27篇
  2011年   26篇
  2010年   20篇
  2009年   26篇
  2008年   27篇
  2007年   25篇
  2006年   15篇
  2005年   17篇
  2004年   20篇
  2003年   16篇
  2002年   12篇
  2001年   15篇
  2000年   7篇
  1999年   14篇
  1998年   21篇
  1997年   17篇
  1996年   14篇
  1995年   8篇
  1994年   11篇
  1993年   12篇
  1992年   12篇
  1991年   8篇
  1990年   11篇
  1989年   15篇
  1988年   13篇
  1987年   19篇
  1986年   13篇
  1985年   11篇
  1984年   16篇
  1983年   12篇
  1982年   9篇
  1981年   11篇
  1980年   4篇
  1978年   8篇
  1977年   5篇
  1976年   11篇
  1975年   7篇
  1974年   12篇
  1973年   7篇
  1971年   4篇
排序方式: 共有725条查询结果,搜索用时 15 毫秒
61.
Recursive causal evaluation is an iterative process in which the evaluation of a target cause, T, is based on the outcome of the evaluation of another cause, C, the evaluation of which itself depends on the evaluation of a 3rd cause, D. Retrospective revaluation consists of backward processing of information as indicated by the fact that the evaluation of T is influenced by subsequent information that is not concerned with T directly. Two experiments demonstrate recursive retrospective revaluation with contingency information presented in list format as well as with trial-by-trial acquisition. Existing associative models are unable to predict the results. The model of recursive causal disambiguation that conceptualizes the revaluation as a recursive process of disambiguation predicts the pattern of results correctly. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
62.
Systematic experiments with distribution games have shown that participants are strongly motivated by considerations of fairness and efficiency. This evidence, however, results mainly from experimental designs in which money is shared directly. Furthermore, fairness does not necessarily require equal payoffs, but may instead require equal allocations. We investigate experimentally the frame dependency of reaching equal (commodity or payoff) splits by systematically comparing net-trade proposals and payoff proposals for the same exchange economy with two traders, two commodities and multi-period negotiations. We can confirm the hypothesis that asking participants to allocate money directly, rather than more naturally via the allocation of commodities, is far from being harmless and likely overstates fairness and efficiency concerns. What is more, we try to apply the insights gained from our experiment to management problems. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
63.
Scale-down of chemical engineering pilot plant – what is attainable? The use of fully automated experimental laboratory-scale plantoffer interesting possibilities for assessment of the economic operation and technical feasibility of new or modified processes. An important condition for the success of this kind of experimental approach is the availability of miniaturized equipment, machines, and sensors. The goal of such experimental plant can be both the process engineering development of individual process steps and also integrated running to model complete processes. Moreover, questions of scale-up can be studied and typical quantities can be provided. The state of the art is reported with the aid of selected examples of equipment and mechanical components and measurement and control units.  相似文献   
64.
The processing parameters of finish rolling and cooling of three HSLA steels were varied in a wide range applying the plane strain hot compression simulation test on the hot deformation simulator (Wumsi). Evaluating the flow curves of the deformation steps, some metallurgical phenomena in austenite during hot deformation could be determined. The results of material testing after the simulation experiments exhibit a strong correlation between the finish rolling and cooling conditions and the final mechanical properties of the steels tested. As a way to increase strength, lowering finishing temperatures and/or accelerating cooling after finish rolling proved to be most effective. To improve notch toughness, on the other hand, a high total finishing strain should be applied as well as low finishing temperatures, however, above Ar3.  相似文献   
65.
We use a two-band k · p Hamiltonian to describe the subband structure in strained silicon thin films. The model describes the dependence of the transversal effective mass on strain and film thickness. However, it is found that the two-band k · p model is unable to describe recently observed large valley splitting. Therefore a generalization of the model is necessary. To go beyond the k · p theory, an auxiliary tight-binding model defined on a lattice of sites containing two localized orbitals is introduced in such a way that it reproduces the bulk dispersion obtained from the two-band k · p model. Corresponding dispersion relations including strain are obtained. We discuss an alternative mechanism to create and control the valley splitting by applying shear strain. The valley splitting increases with increased shear strain and decreasing film thickness and can be larger than the spin splitting. This makes silicon-based quantum devices promising for future applications in quantum computing.  相似文献   
66.
Composites with microstructures of interpenetrating networks were manufactured by gas pressure infiltration of Ni3Al into porous preforms of aluminum oxide. Composites with Ni3Al contents of between 15% and 30% by volume were made and evaluated mechanically at temperatures between room temperature and 1000°C. The fracture strength, the fracture toughness, Young's modulus, and the thermal expansion coefficient were measured for each composite and test condition and were correlated with the microstructures of the composites. Composites with low Ni3Al contents had strengths below 400 MPa, presumably due to microcracking along the interface between the Ni3Al and the Al2O3. The composite with the highest content of Ni3Al, 30 vol%, had a mean fracture strength of 675 ± 16 MPa, a Weibull modulus of 23.9, and a room-temperature toughness of 9.2 ± 0.5 MPa·m1/2.  相似文献   
67.
Summary The United States continues to depend heavily on science and technology for ensuring its defense needs, promoting human welfare, and enhancing its economic competitiveness. I hope that my comments have helped to reinforce the point that we, as a nation, must do a better job of leveraging the federal investment in R & D. I have used examples in materials science and engineering to illustrate how this can be done, because materials science and engineering are crucial to our security and competitiveness, as pointed out in the National Research Council’s report. I also took the liberty of telling you about the broad diversity of the materials program at Los Alamos by picking my examples from Los Alamos’ work. In closing, I recognize fully that what I have discussed today is only part of what is required to maintain national security and enhance competitiveness. I believe that, first and foremost, we must get United States industry back into the lead. And the United States government must address the macroeconomic issues and deal with the crisis in education as well. But I also believe that Los Alamos can help in leveraging the federal R & D investment.  相似文献   
68.
Epidemiological studies indicate a correlation of cruciferous vegetables consumption with reduced incidence of cancer. This study was designed to investigate molecular mechanisms, which may help to understand the beneficial effects of Brussels sprout consumption. In order to avoid the limitations of in vitro model systems, we performed a dietary intervention study with five participants. We investigated, whether sprout consumption affects the proteome profile of primary white blood cells. In order to achieve maximal sensitivity in detecting specific adaptive proteome alterations, we metabolically labelled freshly isolated cells in the presence of 35S‐methionine/cysteine and performed autoradiographic quantification of protein synthesis. Proteins were separated by 2‐DE and spots of interest were cut out, digested and identified by MS. After the intervention, we found a significant up‐regulation of the synthesis of manganese superoxide dismutase (1.56‐fold) and significant down‐regulation of the synthesis of heat shock 70 kDa protein (hsp70; 2.27‐fold). Both proteins play a role in malignant transformation of cells. Hsp‐70 is involved in the regulation of apoptosis, which leads to elimination of cancer cells, while SOD plays a key role in protection against reactive oxygen species mediated effects. Our findings indicate that the alteration of the synthesis of these proteins may be involved in the anticarcinogenic effects of cruciferous vegetables, which was observed in earlier laboratory studies with animals.  相似文献   
69.
We report on the fabrication and performance of vacuum-processed organic field effect transistors utilizing evaporated low-density polyethylene (LD-PE) as a dielectric layer. With C60 as the organic semiconductor, we demonstrate low operating voltage transistors with field effect mobilities in excess of 4 cm2/Vs. Devices with pentacene showed a mobility of 0.16 cm2/Vs. Devices using tyrian Purple as semiconductor show low-voltage ambipolar operation with equal electron and hole mobilities of ~0.3 cm2/Vs. These devices demonstrate low hysteresis and operational stability over at least several months. Grazing-angle infrared spectroscopy of evaporated thin films shows that the structure of the polyethylene is similar to solution-cast films. We report also on the morphological and dielectric properties of these films. Our experiments demonstrate that polyethylene is a stable dielectric supporting both hole and electron channels.  相似文献   
70.
Adsorbents are widely‐used in the area of cleaning as well as enrichment of gas components. For the regeneration of clinoptilolite loaded with ammonia, a packed‐bed reactor was developed on the basis of a dielectric barrier discharge. It was proved that adsorbed NH3 is released at relatively low temperature and low energy consumption. For the further optimization of the method the influence of the power and the pulse break ratio of sustaining voltage were tested. It was shown that with the chosen plasma method the absorber material was loaded repeatedly and subsequently regenerated.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司    京ICP备09084417号-23

京公网安备 11010802026262号