首页 | 本学科首页   官方微博 | 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   403篇
  免费   19篇
电工技术   1篇
化学工业   93篇
金属工艺   10篇
机械仪表   5篇
建筑科学   32篇
矿业工程   1篇
能源动力   8篇
轻工业   73篇
水利工程   6篇
无线电   20篇
一般工业技术   63篇
冶金工业   45篇
原子能技术   3篇
自动化技术   62篇
  2024年   2篇
  2023年   9篇
  2022年   11篇
  2021年   21篇
  2020年   11篇
  2019年   14篇
  2018年   15篇
  2017年   12篇
  2016年   11篇
  2015年   11篇
  2014年   15篇
  2013年   29篇
  2012年   27篇
  2011年   36篇
  2010年   20篇
  2009年   8篇
  2008年   26篇
  2007年   20篇
  2006年   14篇
  2005年   20篇
  2004年   14篇
  2003年   17篇
  2002年   5篇
  2001年   9篇
  2000年   2篇
  1999年   4篇
  1998年   4篇
  1996年   6篇
  1995年   4篇
  1994年   1篇
  1993年   4篇
  1991年   2篇
  1990年   1篇
  1989年   4篇
  1988年   4篇
  1987年   3篇
  1985年   3篇
  1983年   1篇
  1982年   1篇
  1981年   1篇
排序方式: 共有422条查询结果,搜索用时 15 毫秒
21.
Although a substantial proportion of the western population is approaching retirement age, little is known about how they are preparing for the future. Much attention has been paid to the consumption of educational material and retirement wealth in the present literature, but the process of retirement planning has been ignored. S. L. Friedman and E. K. Scholnick's (1997) theoretical model provided the basis for a comprehensive measure of retirement planning. According to their process theory, individuals develop an understanding of the problem, set goals, make a decision to start preparing, and finally undertake the behaviors needed to fulfill their goals. Fifty-two items were developed to assess each stage of the planning process for financial, health, lifestyle, and psychosocial retirement planning. These were tested on a population sample of 1,449 New Zealanders aged 49–60. Confirmatory factor analysis, bivariate correlations, and hierarchical regression provided support for the valid use of the measure. Necessary antecedents, such as the tendency to look to the future, and locus of control were significantly related to the Process of Retirement Planning Scale (PRePS). The PRePS also outperformed retirement planning measures used in the Health and Retirement Study (F. T. Juster & R. Suzman, 1995) after controlling for socioeconomic and psychological variables. This measure will enable social policy makers to determine which stages of retirement planning require support and intervention. The PRePS will also help to determine which domains of retirement planning predict well-being in later life and the factors which differentiate those who are planning from those who are not. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
22.
The main objective of the study reported here was to examine the association between pregnancy loss (PL) and previous exposure to clinical or subclinical mastitis before breeding or during gestation in primiparous Holstein cows. A secondary objective was to estimate the cost of clinical mastitis during gestation, including that of PL attributable to mastitis in study cows. A total of 687 primiparous Holstein cows from 1 dairy farm were included in a matched case-control study. Study cows were declared pregnant via ultrasound on d 33 after timed artificial insemination (TAI). Case cows (n = 78) were those diagnosed as nonpregnant by rectal palpation on d 47 or 75 after TAI. Control cows were those confirmed as pregnant by rectal palpation on d 47 and 75 after TAI. Case cows were matched with eligible controls according to year of calving and calving-to-conception interval ±3 d. Cows were assigned to 1 of 3 groups: (1) cows not affected with clinical or subclinical mastitis; (2) cows affected with subclinical mastitis (Dairy Herd Improvement Association somatic cell score >4.5); and (3) cows affected with clinical mastitis during 2 exposure periods, 1 to 42 d before breeding or during gestation (1 to PL diagnosis day for case cows, and 1 to 75 d for control cows). Conditional logistic regression was used to model the odds of PL as a function of previous exposure to mastitis in study cows. Mastitis before breeding was not associated with PL. The odds of PL were 2.21 times greater in cows affected with clinical mastitis during gestation (95% confidence interval = 1.01, 4.83), compared with cows without mastitis, after controlling for breeding type and lameness. The cost of clinical mastitis during gestation was $149, which includes the cost ($27) of PL attributable to mastitis. In conclusion, this study provides evidence that clinical mastitis during gestation can cause PL in primiparous dairy cows leading to economic losses.  相似文献   
23.
Despite an increasing emphasis on the role of senior managementcognition in shaping organizational action, there have beenfew attempts to link top management mental models to strategicchoice in the face of discontinuous innovation. This paper uses23 years of data covering 15 major pharmaceutical firms to explorethe degree to which each firm's response to the revolution inbiotechnology was shaped by the senior team's recognition ofbiotechnology's importance. Controlling for a number of importantalternative explanations, we show that recognition may be animportant predictor of action, suggesting that cognition atthe most senior level can play a critical role in shaping establishedfirms' response to discontinuities.  相似文献   
24.
The utility of Al, Cu and In filters and collimators of different diameters in the X-ray fluorescence measurement of lead in the bone was investigated. The changes in Compton scattering and Pb K-series peaks were analyzed with different filters and collimators. Compton scattering and fractional dead time were significantly reduced with the use of filters. The FWHM values of Pb Kα1, Kβ1,3 peaks decrease in a nearly linear relation with the ratio of length of collimator to the diameter as the small diameter collimator with long length reduces divergence of spectra, thus improves resolution. The measurement precisions of Kα1 and Kβ1,3 peaks were improved by applying an indium filter. The ratio of signal-to-noise slightly increases when an indium filter was used.  相似文献   
25.
Shape recognition can be achieved through vision or touch, raising the issue of how this information is shared across modalities. Here we provide a short review of previous findings on cross-modal object recognition and we provide new empirical data on multisensory recognition of actively explored objects. It was previously shown that, similar to vision, haptic recognition of objects fixed in space is orientation specific and that cross-modal object recognition performance was relatively efficient when these views of the objects were matched across the sensory modalities (Newell, Ernst, Tjan, & Bülthoff, 2001). For actively explored (i.e., spatially unconstrained) objects, we now found a cost in cross-modal relative to within-modal recognition performance. At first, this may seem to be in contrast to findings by Newell et al. (2001). However, a detailed video analysis of the visual and haptic exploration behaviour during learning and recognition revealed that one view of the objects was predominantly explored relative to all others. Thus, active visual and haptic exploration is not balanced across object views. The cost in recognition performance across modalities for actively explored objects could be attributed to the fact that the predominantly learned object view was not appropriately matched between learning and recognition test in the cross-modal conditions. Thus, it seems that participants naturally adopt an exploration strategy during visual and haptic object learning that involves constraining the orientation of the objects. Although this strategy ensures good within-modal performance, it is not optimal for achieving the best recognition performance across modalities. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
26.
Objective: To investigate the attitudes of terminally ill individuals toward the legalization of euthanasia or physician-assisted suicide (PAS) and to identify those who would personally desire such a death. Design: In the Canadian National Palliative Care Survey, semistructured interviews were administered to 379 patients who were receiving palliative care for cancer. Patients who expressed a desire for physician-hastened death were followed prospectively. Main Outcome Measures: Attitudes toward the legalization of euthanasia or PAS were determined, as was the personal interest in receiving a hastened death. Demographic and clinical characteristics were also recorded, including a 22-item structured interview of symptoms and concerns. Results: There were 238 participants (62.8%) who believed that euthanasia and/or PAS should be legalized, and 151 (39.8%) who would consider making a future request for a physician-hastened death. However, only 22 (5.8%) reported that, if legally permissible, they would initiate such a request right away, in their current situations. This desire for hastened death was associated with lower religiosity (p = .010), reduced functional status (p = .024), a diagnosis of major depression (p  相似文献   
27.
28.
29.
Multifaith buildings have become common in Europe, North America, and much of the world, but they have yet to receive sufficient scholarly attention in the history of religious ideas, or in the theory of material religion. This paper begins to address this lacuna by the consideration of an early, but little known, multifaith chapel donated to Somerville College Oxford in the 1930s, which is unique within Oxford University. Its history, architecture, and artworks give valuable insights into the religious, intellectual, and cultural roots of what would subsequently become a global norm. The chapel can be seen as both a manifestation of the aspirations of liberal Christianity in the interwar years, including the advancement of women and ecumenism, and of the contestation of the role of religion in higher education among elites in the same period. Examining the case of Somerville chapel contributes to the theory of religion by considering how unbelief and multifaith ideas may be attempted to be materially expressed, and how this physical presence subsequently may impact on institutions and people through ongoing contestation, and negotiated use.  相似文献   
30.
The human bioaccessibility of lead (Pb) in Pb-contaminated soils from the Glasgow area was determined by the Unified Bioaccessibility Research Group of Europe (BARGE) Method (UBM), an in vitro physiologically based extraction scheme that mimics the chemical environment of the human gastrointestinal system and contains both stomach and intestine compartments. For 27 soils ranging in total Pb concentration from 126 to 2160 mg kg− 1 (median 539 mg kg− 1), bioaccessibility as determined by the ‘stomach’ simulation (pH ~ 1.5) was 46-1580 mg kg− 1, equivalent to 23-77% (mean 52%) of soil total Pb concentration. The corresponding bioaccessibility data for the ‘stomach + intestine’ simulation (pH ~ 6.3) were 6-623 mg kg− 1 and 2-42% (mean 22%) of soil Pb concentration. The soil 206Pb/207Pb ratios ranged from 1.057 to 1.175. Three-isotope plots of 208Pb/206Pb against 206Pb/207Pb demonstrated that 206Pb/207Pb ratios were intermediate between values for source end-member extremes of imported Australian Pb ore (1.04) - used in the manufacture of alkyl Pb compounds (1.06-1.10) formerly added to petrol - and indigenous Pb ores/coal (1.17-1.19). The 206Pb/207Pb ratios of the UBM ‘stomach’ extracts were similar (< 0.01 difference) to those of the soil for 26 of the 27 samples (r = 0.993, p < 0.001) and lower in 24 of them. A slight preference for lower 206Pb/207Pb ratio was discernible in the UBM. However, the source of Pb appeared to be less important in determining the extent of UBM-bioaccessible Pb than the overall soil total Pb concentration and the soil phases with which the Pb was associated. The significant phases identified in a subset of samples were carbonates, manganese oxides, iron-aluminium oxyhydroxides and clays.  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