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   1565篇
  免费   238篇
  国内免费   443篇
  2024年   4篇
  2023年   27篇
  2022年   58篇
  2021年   73篇
  2020年   84篇
  2019年   55篇
  2018年   77篇
  2017年   92篇
  2016年   74篇
  2015年   68篇
  2014年   96篇
  2013年   130篇
  2012年   111篇
  2011年   158篇
  2010年   133篇
  2009年   110篇
  2008年   115篇
  2007年   151篇
  2006年   157篇
  2005年   129篇
  2004年   75篇
  2003年   62篇
  2002年   39篇
  2001年   21篇
  2000年   29篇
  1999年   20篇
  1998年   11篇
  1997年   13篇
  1996年   10篇
  1995年   9篇
  1994年   11篇
  1993年   6篇
  1992年   1篇
  1991年   3篇
  1990年   5篇
  1989年   6篇
  1988年   4篇
  1987年   3篇
  1986年   3篇
  1985年   5篇
  1984年   1篇
  1982年   2篇
  1981年   1篇
  1979年   1篇
  1976年   1篇
  1972年   1篇
  1971年   1篇
排序方式: 共有2246条查询结果,搜索用时 15 毫秒
111.
Besides the well-known cube-on-cube orientation relationship (OR) between M23C6 carbide and matrix, we have determined a new OR named as the twin-related OR in a long-term ageing Ni-based superalloy on the basis of the extensive and detailed electron diffraction analyses. Furthermore, by means of atomic-resolution high angle annular dark-field imaging technique which is implemented in the aberration-corrected scanning transmission electron microscope, we elucidated the interfacial characteristics between M23C6 and matrix for above two types of ORs. Taking into account of the interfacial characteristics, we propose that the twin-related OR possesses a higher total interfacial energy. Thus, its frequency of occurrence is lower than that of the cube-on-cube OR though both ORs are usually seen in the long-term ageing samples.  相似文献   
112.
The directional solidification process of ternary Ag42.4Cu21.6Sb36 eutectic alloy within a wide growth rate range from 2 to 60 μm/s was accomplished at a constant temperature gradient of 50 K/cm. As growth rate increases, the ternary (θ(Cu2Sb) + ε(Ag3Sb) + Sb) eutectic morphology evolves from “lamellar (θ + ε) plus fibrous (Sb)” structure into “(θ + Sb) fibres in continuous ε matrix” structure. The θ and (Sb) phase spacings decrease with the increase of growth rate according to power functions with exponent values of 0.55 and 0.56, respectively. It is also found that the microhardness of directionally solidified Ag42.4Cu21.6Sb36 alloy samples is enhanced with the increase of growth rate, and the decrease of θ and (Sb) phase spacings.  相似文献   
113.
Subjective career success has long been of interest to scholars because of its importance in the career area. However, the subjective career success literature suffers from the lack of measurement. To fill this void, after reviewing the limitations of the existing instruments, the current study developed a three‐dimensional scale of subjective career success based on the framework of Zhou et al. Three independent studies were conducted using three separate samples (N = 244; N = 411; N = 254) in China to examine the reliability and validity of the developmental scale. The results provided evidence of internal homogeneity, structural validity, convergent validity, discriminant validity, and incremental validity of the developed scale. To conclude the study, the limitations of the article and implications for future study were discussed.  相似文献   
114.
115.
116.
This paper demonstrates the usefulness and flexibility of the general structural equation modelling (SEM) approach to fitting direct covariance patterns or structures (as opposed to fitting implied covariance structures from functional relationships among variables). In particular, the MSTRUCT modelling language (or syntax) of the CALIS procedure (SAS/STAT version 9.22 or later: SAS Institute, 2010) is used to illustrate the SEM approach. The MSTRUCT modelling language supports a direct covariance pattern specification of each covariance element. It also supports the input of additional independent and dependent parameters. Model tests, fit statistics, estimates, and their standard errors are then produced under the general SEM framework. By using numerical and computational examples, the following tests of basic covariance patterns are illustrated: sphericity, compound symmetry, and multiple‐group covariance patterns. Specification and testing of two complex correlation structures, the circumplex pattern and the composite direct product models with or without composite errors and scales, are also illustrated by the MSTRUCT syntax. It is concluded that the SEM approach offers a general and flexible modelling of direct covariance and correlation patterns. In conjunction with the use of SAS macros, the MSTRUCT syntax provides an easy‐to‐use interface for specifying and fitting complex covariance and correlation structures, even when the number of variables or parameters becomes large.  相似文献   
117.
In a mental rotation task, participants must determine whether two stimuli match when one undergoes a rotation in 3-D space relative to the other. The key evidence for mental rotation is the finding of a linear increase in response times as objects are rotated farther apart. This signature increase in response times is also found in recognition of rotated objects, which has led many theorists to postulate mental rotation as a key transformational procedure in object recognition. We compared mental rotation and object recognition in tasks that used the same stimuli and presentation conditions and found that, whereas mental rotation costs increased relatively linearly with rotation, object recognition costs increased only over small rotations. Taken in conjunction with a recent brain imaging study, this dissociation in behavioral performance suggests that object recognition is based on matching of image features rather than on 3-D mental transformations.  相似文献   
118.
华西圣教书会于1899年初成立于重庆,存续40余年,于1941年关闭,是基督教在华西地区最重要的文字机构之一①.本文以清末民初为时限,考察华西圣教书会成立过程及其出版、发行状况,并分析基督教文字事业对华西社会变迁所起到的重大作用.  相似文献   
119.
Four studies were conducted to develop and validate the Coping With Discrimination Scale (CDS). In Study 1, an exploratory factor analysis (N = 328) identified 5 factors: Education/Advocacy, Internalization, Drug and Alcohol Use, Resistance, and Detachment, with internal consistency reliability estimates ranging from .72 to .90. In Study 2, a confirmatory factor analysis (N = 328) provided cross-validation of the 5-factor model as well as evidence for validity of the scale. The validity evidence was similar across racial groups and for males and females. In Study 3, the estimated 2-week test-retest reliabilities (N = 53) were between .48 and .85 for the 5 factors. Education/Advocacy, Internalization, Drug and Alcohol Use, and Detachment were positively associated with active coping, self-blame, substance use, and behavioral disengagement, respectively, providing further support for validity of the CDS. Finally, incremental validity evidence was obtained in Study 4 (N = 220), where it was shown that the CDS explained variance in outcome variables (i.e., depression, life satisfaction, self-esteem, and ethnic identity) that could not be explained by general coping strategies.  相似文献   
120.
This paper studies changes of standard errors (SE) of the normal-distribution-based maximum likelihood estimates (MLE) for confirmatory factor models as model parameters vary. Using logical analysis, simplified formulas and numerical verification, monotonic relationships between SEs and factor loadings as well as unique variances are found. Conditions under which monotonic relationships do not exist are also identified. Such functional relationships allow researchers to better understand the problem when significant factor loading estimates are expected but not obtained, and vice versa. What will affect the likelihood for Heywood cases (negative unique variance estimates) is also explicit through these relationships. Empirical findings in the literature are discussed using the obtained results.  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