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971.
The experiments reported in the present study tested whether decreasing intertrial intervals (ITIs) intensifies the disruptive
effects of increasing retention intervals (RIs) in a delayed conditional discrimination by decreasing the animal’s trial tracking
accuracy (Cohen & Armstrong, 1996; Cohen & Roberts, 1996). Rats responded on a fixed ratio (FR) 1 or fixed interval (FI) 10-sec
reinforcement schedule at a second light or tone stimulus, S2, when the first light or tone stimulus, S1, had signaled an
FI 10-sec or FR 1 schedule, respectively. RIs between S1 and S2 were increased from 3 to 24 sec and never exceeded ITIs that
were reduced from 24 to 6 sec. For some rats, the trials were separated from each other by extending the lever at S1 and retracting
it at the end of S2 (ITI lever-retracted group). For other, control rats, the lever remained extended throughout the session
(lever-extended group, Experiment 1) or was extended and retracted with the onset and offset of each stimulus (RI/ITI lever-retracted
group, Experiment 2). The rats under all trial conditions learned to delay leverpressing on the FI 10-sec schedule. Latency
to begin leverpressing on the FI 10-sec schedule declined as RIs were increased, but this effect was attenuated in the ITI
lever-retracted groups in both experiments, as would be predicted by thetrial tracking hypothesis. Decreasing ITIs from 24 to 6 sec intensified the disruptive effects of increasing RIs from 3 to 6 sec in the
RI/ITI lever-retracted group (Experiment 2), as would be predicted by the trial tracking hypothesis. 相似文献
972.
S M Srivastava 《Resonance》2007,12(2):59-70
In 1931, the great Austrian mathematician Kurt Gödel proved “all consistent axiomatic formulations of number theory include undecidable propositions”. This discovery of Gödel and its proof had enormous repercussions in mathematics and computer science. The proof hinged upon the writing of a self-referential mathematical statement, in the same way as the liar’s paradox — I am lying — is a self-referential statement. In this three-part article, we describe Gödel’s discovery and his famous proof. 相似文献
973.
S. Selcen Guzey Elizabeth A. Ring-Whalen 《International Journal of Science Education》2018,40(7):723-741
Engineering has been slowly integrated into K-12 science classrooms in the United States as the result of recent science education reforms. Such changes in science teaching require that a science teacher is confident with and committed to content, practices, language, and cultures related to both science and engineering. However, from the perspective of the science teacher, this would require not only the development of knowledge and pedagogies associated with engineering, but also the construction of new identities operating within the reforms and within the context of their school. In this study, a middle school science teacher was observed and interviewed over a period of nine months to explore his experiences as he adopted new values, discourses, and practices and constructed his identity as a reform-minded science teacher. Our findings revealed that, as the teacher attempted to become a reform-minded science teacher, he constantly negotiated his professional identities – a dynamic process that created conflicts in his classroom practices. Several differences were observed between the teacher’s science and engineering instruction: hands-on activities, depth and detail of content, language use, and the way the teacher positioned himself and his students with respect to science and engineering. Implications for science teacher professional development are discussed. 相似文献
974.
Kersting S 《Journal of deaf studies and deaf education》1997,2(4):252-263
This qualitative study of the social aspects of mainstreaming from the perspective of deaf college students indicates that for some students, social adjustment to college is complicated by experiences of separation and alienation from both deaf and hearing peers. Data were collected through open-ended interviews with deaf students who had little or no previous experience with or exposure to deaf culture or language before their arrival at a mainstream college environment. Feelings of isolation, loneliness, and resentment were most intense during orientation and first year, when alienation from the deaf student community appeared to be caused by lack of sign language skills, unfamiliarity with norms and values of deaf culture, and perceived hostility from deaf peers. Simultaneous experiences of separation from hearing peers appeared to be caused by physical barriers inherent in the classroom, residence hall, and cafeteria environments, as well as by discrimination from hearing peers, who tended to stereotype deaf students. Findings suggest that those involved in the administration and delivery of postsecondary programs for the deaf should investigate the experiences of students who arrive on campus without knowledge of sign language or familiarity with deaf culture and evaluate currently existing programs and services designed to meet these students' needs. 相似文献
975.
Understanding Leadership in Major Sporting Events: The Case of the 2005 World Aquatics Championships
The purpose of this paper was to begin understanding leadership within a major sporting event. A case study of the 2005 Fédération Internationale de Natation (FINA) World Aquatics Championships was built by means of interviews and archival material, using a multi-stakeholder perspective. Findings highlighted that core elements of upper-management level leadership in events were best described by the multiple-linkage leadership theory, which includes task commitment, ability and role clarity, work organization, cooperation and mutual trust, resources and support, and external coordination as the six intervening variables. While charismatic and transformational leadership styles surfaced as contributing to the overall success of an event, the multiple-linkage leadership theory offered a more comprehensive understanding of leadership in major sporting events from a multi-stakeholder perspective. 相似文献
976.
V. B. Saputra S. K. Ong A. Y. C. Nee 《上海大学学报(英文版)》2014,(3):222-230
This paper presents a calibration method for parallel manipulators using a measurement system specially installed on an external fixed frame. The external fixed frame is important as an error reference for calibration in certain operations, such as in the configuration of a parallel manip- ulator functioning as a machine tool where the workpiece is fixed to a worktable. The pose of the end-effector is mea- sured using three digital indicators installed on the external fixed frame. To enable measurement, the end-effector is assumed to be a plane large enough that all digital indicators could touch. The error is defined as the difference between the theoretical and actual readings of the digital indicators. The geometric parameters of the parallel manipulator are optimized to minimize this error. This calibration method is low cost and feasible for compensating geometric parameter errors for a parallel manipulator. Optimal pose selection for the calibration is achieved using a swarm intelligence search algorithm. The method is implemented on a prototype of a six degrees-of-freedom (DOFs) Gough-Stewart platform constructed to function as a machine tool. 相似文献
977.
Homework: a cross-cultural examination 总被引:5,自引:1,他引:5
Cultural differences in the amount of time spent on homework and in beliefs and attitudes about homework were investigated through interviews with more than 3,500 elementary school children, their mothers, and their teachers. The children lived in 5 cities: Beijing, Chicago, Minneapolis, Sendai (Japan), and Taipei. Chinese children were assigned more homework and spent more time on homework than Japanese children, who in turn were assigned more and spent more time on homework than American children. Chinese children also received more help from family members with their homework than American and Japanese children. Chinese children were found to have more positive attitudes about homework than American children; Japanese children's attitudes were between those of the Chinese and American children. Relations between amount of time spent on homework by children, amount of time parents spent assisting their children with homework, and children's achievement were also explored. The views of both parents and teachers about the value of homework are discussed. 相似文献
978.
979.
Serum glycoproteins were evaluated in oral squamous cell carcinoma patients treated with radiotherapy and also the effect
of vitamin E was studied. Cell surface glycoconjugates are important parameters in the detection of malignancy. Thus, the
objective of the present study is to evaluate the efficacy of vitamin E on glycoproteins in oral cavity cancer patients treated
with radiotherapy. The study includes 26 age and sex matched normal healthy individuals and 26 patients with squamous cell
carcinoma of oral cavity. These patients were divided into two groups, one for radiotherapy alone (at a dosage of 6000 cGy
in five fractions per week for a period of six weeks) and the other for radiotherapy plus vitamin E supplementation (at a
dosage of 400 IU / day of vitamin E) for the entire period of radiotherapy. Levels of hexose, hexosamine, fucose and sialic
acid were increased in oral squamous cell carcinoma patients and a significant decrease was observed in radiation treated
patients when compared to control. The levels of glycoconjugates were significantly decreased in radiation treated patients
supplemented with vitamin E. This measurement may be useful in assessing disease progression and identifying patients resistant
to therapy and a possible role of vitamin E on reduction in glycoconjugate levels of radiation treated oral squamous cell
carcinoma patients. 相似文献
980.
S A Al-Abood K Davids S J Bennett D Ashford M Martinez Marin 《Journal of sports sciences》2001,19(7):507-520
In the visual perception perspective of observational learning, the manipulation of relative and absolute motion information in visual demonstrations optimally directs learners' search towards appropriate task solutions. We assessed the effect of emphasizing transformational information and removal of structural information using point-light kinematic displays in approximating the model's relative motion patterns. Participants viewed computer-simulated point-light demonstrations or normal video demonstrations before and intermittently throughout 100 acquisition trials with knowledge of results on an underarm modified-dart aiming task. On the next day, all participants performed 20 retention trials without demonstrations. The kinematics of spatial and temporal coordination and control variables were examined relative to the model's action, as well as performance scores. The results indicated that approximation of the model's spatial and temporal coordination and control patterns was achieved after observation of either type of demonstrations. No differences were found in movement outcomes. In a second experiment, the effects of manipulating absolute motion information by slow-motion demonstrations were examined relative to real-time demonstrations. Real-time demonstrations led to a closer approximation to the model's spatial and temporal coordination patterns and better outcome scores, contradicting predictions that slow-motion displays convey intact relative motion information. We speculate that the effect of visual demonstration speed on action perception and reproduction is a function of task constraints--that is, novelty or familiarity of relative motion of demonstrated activities. 相似文献