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   502篇
  免费   14篇
  国内免费   2篇
电工技术   2篇
化学工业   79篇
金属工艺   8篇
机械仪表   5篇
建筑科学   20篇
矿业工程   3篇
能源动力   12篇
轻工业   54篇
水利工程   6篇
石油天然气   10篇
无线电   36篇
一般工业技术   67篇
冶金工业   141篇
原子能技术   2篇
自动化技术   73篇
  2023年   1篇
  2022年   7篇
  2021年   5篇
  2020年   5篇
  2019年   10篇
  2018年   4篇
  2017年   9篇
  2016年   12篇
  2015年   4篇
  2014年   12篇
  2013年   22篇
  2012年   20篇
  2011年   40篇
  2010年   20篇
  2009年   11篇
  2008年   33篇
  2007年   35篇
  2006年   21篇
  2005年   22篇
  2004年   16篇
  2003年   17篇
  2002年   20篇
  2001年   7篇
  2000年   5篇
  1999年   11篇
  1998年   9篇
  1997年   5篇
  1996年   8篇
  1995年   15篇
  1994年   9篇
  1993年   14篇
  1992年   6篇
  1991年   3篇
  1990年   12篇
  1989年   5篇
  1988年   8篇
  1987年   5篇
  1986年   8篇
  1985年   8篇
  1984年   9篇
  1983年   6篇
  1982年   3篇
  1981年   6篇
  1980年   3篇
  1979年   2篇
  1977年   1篇
  1976年   1篇
  1973年   3篇
排序方式: 共有518条查询结果,搜索用时 15 毫秒
101.
102.
Water can be a scarce resource, particularly in certain places at certain times. Understanding both water use and conservation efforts can help ensure that limited supplies can meet the demands of a growing population and economy. This paper examines water use and recirculation in the U.S. manufacturing sector, using newly recovered microdata from the Survey of Water Use in Manufacturing, merged with establishment-level data from the Annual Survey of Manufactures and the Census of Manufactures. Results suggest that water use per unit of output is largest for larger establishments, in part because larger establishments use water for more purposes. Larger establishments are also found to recirculate water more — satisfying demand (water use) without necessarily increasing water intake. Various costs also appear to play a role in water recirculation. In particular, the water circulation rate is found to be higher when water is purchased from a utility. Relatively low (internal) prices for self-supplied water could suppress the incentive to invest in recirculation. Meanwhile, establishments with higher per-gallon intake treatment costs also recirculate more, as might be expected. The cost associated with water discharge – due to regulation or otherwise – also increases circulation rates. The aridity of a locale is found to have little effect on circulation rates.  相似文献   
103.
The personal computer has started a revolution in the way data is collected and stored by bringing computer capabilities within the economic reach of even the smallest company. Computer data acquisition and manipulation expands the usefulness of the already valuable torque rheometer as a tool for both rheological studies and routine quality control testing. Analysis of more fundamental rheological properties than just the traditional torque vs. time curve is possible without the time consuming manual data manipulation. Data storage and recall of routine or Q.C. testing for accurate comparisons of results is made easier. Torque rheometer uses made easier by the use of a computer are reviewed. Also given are details of how to hook up a personal computer to an existing torque rheometer.  相似文献   
104.
Dynamic oscillatory shear tests are common in rheology and have been used to investigate a wide range of soft matter and complex fluids including polymer melts and solutions, block copolymers, biological macromolecules, polyelectrolytes, surfactants, suspensions, emulsions and beyond. More specifically, small amplitude oscillatory shear (SAOS) tests have become the canonical method for probing the linear viscoelastic properties of these complex fluids because of the firm theoretical background [1], [2], [3] and [4] and the ease of implementing suitable test protocols. However, in most processing operations the deformations can be large and rapid: it is therefore the nonlinear material properties that control the system response. A full sample characterization thus requires well-defined nonlinear test protocols. Consequently there has been a recent renewal of interest in exploiting large amplitude oscillatory shear (LAOS) tests to investigate and quantify the nonlinear viscoelastic behavior of complex fluids. In terms of the experimental input, both LAOS and SAOS require the user to select appropriate ranges of strain amplitude (γ0) and frequency (ω). However, there is a distinct difference in the analysis of experimental output, i.e. the material response. At sufficiently large strain amplitude, the material response will become nonlinear in LAOS tests and the familiar material functions used to quantify the linear behavior in SAOS tests are no longer sufficient. For example, the definitions of the linear viscoelastic moduli G′(ω) and G″(ω) are based inherently on the assumption that the stress response is purely sinusoidal (linear). However, a nonlinear stress response is not a perfect sinusoid and therefore the viscoelastic moduli are not uniquely defined; other methods are needed for quantifying the nonlinear material response under LAOS deformation. In the present review article, we first summarize the typical nonlinear responses observed with complex fluids under LAOS deformations. We then introduce and critically compare several methods that quantify the nonlinear oscillatory stress response. We illustrate the utility and sensitivity of these protocols by investigating the nonlinear response of various complex fluids over a wide range of frequency and amplitude of deformation, and show that LAOS characterization is a rigorous test for rheological models and advanced quality control.  相似文献   
105.
Understanding and characterizing the radiolytic degradation of solvents used for treatment of used nuclear fuel is an ongoing topic of research. In the work presented here, degradation constants for the radiolysis of tributyl phosphate (TBP) as a function of various process variables, such as the inclusion of nitric acid and uranyl ions on the TBP, were determined. Degradation constants were determined for both high linear energy transfer (LET) and low LET (gamma) radiation exposure. Results indicate that susceptibility to gamma radiolysis is roughly twice that of high LET and that acid uptake by TBP has little effect on the overall degradation for both high and low LET irradiations. The inclusion of a metal ion affects the degradation of TBP by forming complexes that absorb a portion of the energy deposited by radiation. These TBP–metal complexes break down during irradiation, and the degradation constants for the complex were found to be higher compared to free TBP, for both high and low LET radiations suggesting that the TBP–uranyl complex is more susceptible to radiation than free TBP.  相似文献   
106.
By adopting Nb2O5, HNO3 and coordination agents EDTA as raw materials, pyrochlore‐free 0.64Pb(Ni1/3Nb2/3)O3–0.36PbTiO3(0.64PNN–0.36PT) powders were successfully synthesized via a combustion route. Free of pyrochlore phase was realized by the chelation formation of EDTA‐metal ions which isolate niobium and lead oxides and then prevent the formation of pyrochlore phases, therein generate the desired perovskite phases. Comparing the results with similar samples synthesized by the Columbite method, the new 0.64PNN–0.36PT ceramics here shown much better dielectric and ferroelectric performances: a maximum dielectric constant of 22 856 at 1 kHz and a remnant polarization of 21.6 μC/cm2 at 40 kV/cm.  相似文献   
107.
108.
Assessed whether the Bem Sex-Role Inventory (BSRI) and the Personality Research Form (PRF) ANDRO scale developed by J. I. Berzins et al (see record 1978-30742-001) are appropriate for investigations of gender schema theory, as outlined by S. L. Bem (see record 1981-25685-001). On the basis of the propositions of gender schema theory, several predictions were made about the psychometric properties that should be exhibited by a valid measure of this construct. Responses of 223 male and 338 female undergraduates to the PRF ANDRO and the BSRI were factor analyzed separately for sex-typed and non-sex-typed groups. Results show consistent and theoretically predictable differences in the factor solutions of these 2 groups. The sex-typed or gender-schematic group obtained bipolar factors, with masculine items loading with one sign, whereas feminine items loaded with the other sign on each factor. Also, sex of S loaded highly on almost every factor for this group. The non-sex-typed group, however, obtained few such distinctly dichotomous factors, and sex of S loaded only on the weaker factors. Results support the construct validity of the BSRI and the PRF ANDRO for use in researching the implications of the gender schema approach. (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
109.
Exploring process data with the use of robust outlier detection algorithms   总被引:3,自引:0,他引:3  
To implement on-line process monitoring techniques such as principal component analysis (PCA) or partial least squares (PLS), it is necessary to extract data associated with the normal operating conditions from the plant historical database for calibrating the models. One way to do this is to use robust outlier detection algorithms such as resampling by half-means (RHM), smallest half volume (SHV), or ellipsoidal multivariate trimming (MVT) in the off-line model building phase. While RHM and SHV are conceptually clear and statistically sound, the computational requirements are heavy. Closest distance to center (CDC) is proposed in this paper as an alternative for outlier detection. The use of Mahalanobis distance in the initial step of MVT for detecting outliers is known to be ineffective. To improve MVT, CDC is incorporated with MVT. The performance was evaluated relative to the goal of finding the best half of a data set. Data sets were derived from the Tennessee Eastman process (TEP) simulator. Comparable results were obtained for RHM, SHV, and CDC. Better performance was obtained when CDC is incorporated with MVT, compared to using CDC and MVT alone. All robust outlier detection algorithms outperformed the standard PCA algorithm. The effect of auto scaling, robust scaling and a new scaling approach called modified scaling were investigated. With the presence of multiple outliers, auto scaling was found to degrade the performance of all the robust techniques. Reasonable results were obtained with the use of robust scaling and modified scaling.  相似文献   
110.
Working memory (WM) was studied in 82 healthy volunteers, 43 schizophrenia patients, and 81 bipolar patients. Schizophrenia patients were impaired on verbal and figural WM tasks that possessed similar test discriminating power. Bipolar patients performed similarly to healthy volunteers. A mathematical model of WM performance revealed a primary role for reduced WM span in accounting for the impaired verbal WM of schizophrenia patients and a primary role for diminished attention in accounting for impaired figural WM. Although WM impairment in schizophrenia is due neither to the general effects of severe mental illness nor to the specific type of material studied, the microarchitecture of abnormal WM in schizophrenia may depend on the stimulus material presented. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  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