全文获取类型
收费全文 | 8527篇 |
免费 | 517篇 |
国内免费 | 127篇 |
出版年
2024年 | 18篇 |
2023年 | 123篇 |
2022年 | 133篇 |
2021年 | 189篇 |
2020年 | 254篇 |
2019年 | 279篇 |
2018年 | 453篇 |
2017年 | 477篇 |
2016年 | 419篇 |
2015年 | 278篇 |
2014年 | 300篇 |
2013年 | 1043篇 |
2012年 | 584篇 |
2011年 | 570篇 |
2010年 | 366篇 |
2009年 | 247篇 |
2008年 | 494篇 |
2007年 | 414篇 |
2006年 | 360篇 |
2005年 | 293篇 |
2004年 | 250篇 |
2003年 | 230篇 |
2002年 | 171篇 |
2001年 | 107篇 |
2000年 | 126篇 |
1999年 | 94篇 |
1998年 | 60篇 |
1997年 | 53篇 |
1996年 | 41篇 |
1995年 | 35篇 |
1994年 | 32篇 |
1993年 | 38篇 |
1992年 | 41篇 |
1991年 | 50篇 |
1990年 | 52篇 |
1989年 | 35篇 |
1988年 | 41篇 |
1987年 | 35篇 |
1986年 | 33篇 |
1985年 | 38篇 |
1984年 | 33篇 |
1983年 | 23篇 |
1981年 | 19篇 |
1979年 | 19篇 |
1978年 | 16篇 |
1977年 | 16篇 |
1974年 | 16篇 |
1968年 | 17篇 |
1966年 | 17篇 |
1965年 | 14篇 |
排序方式: 共有9171条查询结果,搜索用时 15 毫秒
71.
72.
G. A. Nesvetailov’s 《Knowledge, Technology, and Policy》1993,6(1):38-51
In this paper a method is outlined for measuring the diversity of the results of applied R&D with the use of IPC (International
Patent Classification). The method has been tested in the contexts of the academic physical, engineering, and chemical institutes.
The trend of applied research at a given institute increases both at the level of classes and subclasses, and at the IPC level.
Inventions developed within specializations at each institute have a greater efficiency than other forms of inventive activity.
The objective was to seek the optimal extent of diversification of applied R&D, which would simultaneously ensure the preservation
of the scientific specialization of an institute, the high level of scientific research associated with developing innovations,
and the high overall efficiency of each institute. 相似文献
73.
Marja Alestalo’s 《Knowledge, Technology, and Policy》1993,6(1):52-66
Finland has followed the Scandinavian model of the welfare state in which the level of state activism is high, the economic
pressures on the scientific activities are strong, and the left-wing parties and the Center Party have formulated the main
ideas. In the 1970s welfare ideology was adopted in science policy by emphasizing the promotion of socially relevant scientific
activities and the expansion of the university system as a means of effecting equal opportunity. Currently, the trend is toward
a mixed welfare economy. Programs have been prepared in spite of the radical cut in government expenditure, and without a
consideration of the long-term consequences. 相似文献
74.
Sjoerd C. de Vries Astrid M. L. Kappers Jan J. Koenderink 《Attention, perception & psychophysics》1993,53(1):71-80
We used quadratic shapes in several psychophysical shape-from-stereo tasks. The shapes were elegantly represented in a 2-D parameter space by the scale-independentshape index and the scale-dependentcurvedness. Using random-dot stereograms to depict the surfaces, we found that the shape of hyperbolic surfaces is slightly more difficult to recognize than the shape of elliptic surfaces. We found that curvedness (and indirectly, scale) has little or no influence on shape recognition. 相似文献
75.
When an observer views a moving scene binocularly, both motion parallax and binocular disparity provide depth information. In Experiments lA-1C, we measured sensitivity to surface curvature when these depth cues were available either individually or simultaneously. When the depth cues yielded comparable sensitivity to surface curvature, we found that curvature detection was easier with the cues present simultaneously, rather than individually. For 2 of the 6 subjects, this effect was stronger when the component of frontal translation of the surface was vertical, rather than horizontal. No such anisotropy was found for the 4 other subjects. If a moving object is observed binocularly, the patterns of optic flow are different on the left and right retinae. We have suggested elsewhere (Cornilleau-Pérès & Droulez, in press) that this motion disparity might be used as avisual cue for the perception of a 3-D structure. Our model consisted in deriving binocular disparity from the left and right distributions of vertical velocities, rather than from luminous intensities, as has been done in classical studies on stereoscopic vision. The model led to some predictions concerning the detection of surface curvature from motion disparity in the presence or absence of intensity-based disparity (classically termedbinocular disparity). In a second set of experiments, we attempted to test these predictions, and we failed to validate our theoretical scheme from a physiological point of view. 相似文献
76.
Manuel Ruiz Ruiz Ph.D. M.D. Patricia Fernández-Baca M.D. Gloria Busby M.A. 《Journal of Contemporary Psychotherapy》1993,23(1):61-67
Paradigmatic complexes in family psychotherapy have been indicating a revolutionary change and the creation of new paradigms for the past thirty years. Starting with the application of the general systems theory and the development of those concepts that have been emerging regarding psychosomatic illnesses we discuss the epistemological confusion created, the methodological problems and the dissociation between theory and practice. We suggest a double process of investigation of the family structure using a knowledge of the basic attitudes and the development of a psychotherapy programme within the family of the psychosomatic patient. 相似文献
77.
Job Satisfaction Among Ethnic Minorities in The Netherlands 总被引:1,自引:0,他引:1
78.
Escape and avoidance that are disproportional to the danger of the pertinent stimulus are important clinical problems that are often related to inaccurate (catastrophic) expectations. One possible source of such expectations is a prior, underestimated aversive experience. In the present experiment the hypotheses that underestimated pain leads to escape and that it leads to avoidance were tested. In order to control for the effect of the intensity of the pain stimulus, a control group that received 20 pain stimuli of high intensity was formed. Subjects in the experimental condition received 17 pain stimuli of low intensity and 3 of (unexpectedly) high intensity (experimentally induced underprediction). Underprediction of the high intensity stimulus was significantly related to escape, but not to avoidance. The results suggest that the way in which avoidance was operationalized accounts for this. The strong support of the hypothesized relationship between underpredicted pain and escape is an important finding, however. 相似文献
79.
The Priestley duality for Wajsberg algebras 总被引:1,自引:1,他引:0
N. G. Martínez 《Studia Logica》1990,49(1):31-46
The Priestley duality for Wajsberg algebras is developed. The Wajsberg space is a De Morgan space endowed with a family of functions that are obtained in rather natural way.As a first application of this duality, a theorem about unicity of the structure is given. 相似文献
80.
This case study concerns an 18-year-old bilingual girl who suffered a radiation lesion in the left (dominant) thalamic and temporal region when she was 4 years old. Language and memory assessment revealed deficits in auditory short-term memory, auditory word comprehension, nonword repetition, syntactic processing, word fluency, and confrontation naming tasks. Both languages (English and Dutch) were found to be affected in a similar manner, despite the fact that one language (English) was acquired before and the other (Dutch) after the period of lesion onset. Most of the deficits appear to be related to verbal (short-term) memory dysfunction. Several hypotheses of subcortical involvement in memory processes are discussed with reference to existing theories in this area. 相似文献