全文获取类型
收费全文 | 621篇 |
免费 | 32篇 |
国内免费 | 25篇 |
出版年
2023年 | 13篇 |
2022年 | 4篇 |
2021年 | 11篇 |
2020年 | 10篇 |
2019年 | 16篇 |
2018年 | 19篇 |
2017年 | 20篇 |
2016年 | 15篇 |
2015年 | 15篇 |
2014年 | 15篇 |
2013年 | 123篇 |
2012年 | 31篇 |
2011年 | 32篇 |
2010年 | 25篇 |
2009年 | 16篇 |
2008年 | 28篇 |
2007年 | 29篇 |
2006年 | 10篇 |
2005年 | 17篇 |
2004年 | 15篇 |
2003年 | 13篇 |
2002年 | 12篇 |
2001年 | 24篇 |
2000年 | 26篇 |
1999年 | 7篇 |
1998年 | 7篇 |
1997年 | 6篇 |
1996年 | 5篇 |
1995年 | 5篇 |
1994年 | 4篇 |
1992年 | 7篇 |
1991年 | 7篇 |
1990年 | 8篇 |
1989年 | 4篇 |
1987年 | 3篇 |
1986年 | 4篇 |
1985年 | 5篇 |
1983年 | 3篇 |
1980年 | 2篇 |
1979年 | 6篇 |
1978年 | 2篇 |
1976年 | 5篇 |
1975年 | 4篇 |
1974年 | 7篇 |
1973年 | 3篇 |
1972年 | 8篇 |
1971年 | 2篇 |
1969年 | 4篇 |
1966年 | 3篇 |
1959年 | 2篇 |
排序方式: 共有678条查询结果,搜索用时 15 毫秒
601.
Visual word recognition of a profoundly deaf girl (AH) with developmental reading disorders was explored using an experimental technique that measures performance as a function of eye fixation within a word. AH's fixation-dependent word recognition profile revealed that she was inferring the identity of words using a "logographic" reading strategy (i. e., using salient visual features). Following this observation a special training program that enhances the understanding of grapheme-phoneme relations was applied. After few months of training, AH's reading skills improved, while her fixation-dependent performance changed to become like that of normal readers. We discuss the impact of our technique for the early diagnosis of reading impairments. 相似文献
602.
Elderly suicide in China 总被引:1,自引:0,他引:1
The rise in suicide rate among elderly people in China in recent years is noteworthy and may be associated with the increasing poverty of elderly people and the lack of social resources allocated to providing them with needed services to ensure their health and mental well-being. 相似文献
603.
Ye X Mitchell M Newman K Batshaw ML 《Mental retardation and developmental disabilities research reviews》2001,7(1):65-72
Advances in understanding the genetics and pathogenesis of disease and in prenatal diagnosis have lead to an exploration of ways to intervene earlier and earlier in the disease process. The possibility of prenatal gene therapy for severe genetic and developmental disorders has sparked new research and debate as to its feasibility, reliability, and ethics as a therapeutic option. Recent animal studies have demonstrated the feasibility of introducing a vector into the developing fetus. The optimal timing and best mode of delivery, however, have yet to be defined. Whether or not this research should be pursued also has been the subject of recent bioethical debates. There is additional concern with the possibility of in utero gene transfer inducing mutagenesis and subsequent tumor formation. This review will provide a summary of the current state of knowledge in the field of prenatal gene therapy and possible directions for the future research. 相似文献
604.
In this study (N = 210), participants were sampled through the Mechanical Turk system to assess the validity and structural properties of the Dark Triad Dirty Dozen (i.e., narcissism, psychopathy, and Machiavellianism). First, the correlations of the Dirty Dozen and long-form Dark Triad measures with sociosexual behaviors, attitudes, and desires, were generally consistent. Second, the scales of the Dirty Dozen measure modestly correlated with other measures of the same constructs as would be expected given the reduction in content-breadth. Third, the scales tap different dimensions (e.g., primary psychopathy, entitlement) of the older measures despite the loss of content. Fourth, a series of factor analyses revealed that the three dimensional structure replicates, but the data were best explained by a bifactor model. Despite traditional objections to short measures, if the short measure is up to the task of measuring its constructs and has good structural properties, it is a useful tool. Whereas the Dirty Dozen appears to provide conservative estimates of correlations it does appear to be a valid and psychometrically sound measure of the Dark Triad. 相似文献
605.
The nature of shear flow lines in equal-channel angular-pressed (ECAPed) metals has been investigated experimentally and theoretically. Experimental results indicate that, for metals pressed in a right-angle die, the shear flow lines often have an angle of ~27° with respect to the extrusion direction. It is suggested that the shear flow lines are composed of a group of elongated grains with an elongation direction that deviates slightly from that of the shear flow lines. 相似文献
606.
Dislocation microstructures induced by room-temperature microhardness tests have been investigated in silicon nitride. Surface analysis of the residual indent by atomic force microscopy reveals intragranular slip bands and demonstrates that room-temperature plastic deformation involves dislocation motion as well as cross-slip events. Cross-slip events have been found to occur between {1010} prismatic planes. Transmission electron microscopy shows that dislocations have a Burgers vector b = [0001] and are located along the screw direction. Based on these observations, specific dislocation core configurations are discussed. 相似文献
607.
The surface tension of undercooled liquid cobalt has been measured by the oscillating-drop technique combined with electromagnetic levitation. The accuracy of the method was verified by measurements of the surface tension of liquid nickel. The liquid cobalt was undercooled by up to 231K (0.13T m), and its surface tension determined to be σCo =1875 0.348(T-T m)mNm-1. From this result, the viscosity, self-diffusion coefficient, density and thermal diffusivity of undercooled liquid cobalt were derived. Using these thermophysical parameters, the growth velocity of cobalt dendrite is calculated and shown to agree well with experimental results. Furthermore, the Marangoni number and the Rayleigh number are calculated; these increase slowly with increasing degree of undercooling. 相似文献
608.
Localised shear deformation of a material is usually identified as a particular feature of deformation inhomogeneity. Here, we show two different types of shear deformation-behaviour that occurred in Au–Cu multilayers subjected to microindentation load, namely, a cooperative-layer-buckling-induced shear banding in a nanoscale multilayer and a direct localised shearing across a layer interface along a shear plane in a submicron-scale multilayer. Theoretical analysis indicates that the formation of the two different types of shear deformation in the multilayers depends on a competition between the dislocation-pile-up-induced stress concentration at the layer interface and the barrier strength of the layer interface for glissile dislocation transmission. 相似文献
609.
Using high-resolution electron microscopy, we investigated the initial stages of high-pressure-torsion-induced crystalline-to-amorphous transformation of TiNi. It is found that the deformation-induced amorphization initiated from dislocation core regions in the interior of grains and from grain boundaries. It is believed that both the energy stored in the dislocations and the energy stored in the grain boundaries contribute significantly to driving the crystalline-to-amorphous transformation. 相似文献
610.
Nanometre-sized kinks and cracks formed in 6H SiC under ball milling (BM) at room temperature have been observed and characterized on the atomic scale using high-resolution electron microscopy (HREM). Observations of the kinks show that numerous positive and negative partials are aligned at either of the kink boundaries, and the stacking sequences in the kink band are considerably different from those in the other areas. It was also observed that the (0001) lattice planes in the kink band are kinked, indicating that microplasticity occurs in the normally brittle material SiC under BM even at room temperature. HREM observations of cracks show that cracks previously observed by transmision electron microscopy are not completely open but are at the initiation stage of fracture. Inside a crack, one residual kink region can be clearly observed, which indicates a correlation between kink and crack, that is a crack evolves from a kink. 相似文献