全文获取类型
收费全文 | 45998篇 |
免费 | 908篇 |
国内免费 | 9篇 |
专业分类
46915篇 |
出版年
2020年 | 511篇 |
2019年 | 605篇 |
2018年 | 830篇 |
2017年 | 780篇 |
2016年 | 893篇 |
2015年 | 617篇 |
2014年 | 767篇 |
2013年 | 3407篇 |
2012年 | 1440篇 |
2011年 | 1386篇 |
2010年 | 884篇 |
2009年 | 905篇 |
2008年 | 1195篇 |
2007年 | 1230篇 |
2006年 | 1093篇 |
2005年 | 980篇 |
2004年 | 931篇 |
2003年 | 834篇 |
2002年 | 880篇 |
2001年 | 1586篇 |
2000年 | 1591篇 |
1999年 | 1157篇 |
1998年 | 474篇 |
1997年 | 453篇 |
1995年 | 435篇 |
1992年 | 931篇 |
1991年 | 878篇 |
1990年 | 879篇 |
1989年 | 802篇 |
1988年 | 779篇 |
1987年 | 725篇 |
1986年 | 702篇 |
1985年 | 749篇 |
1984年 | 638篇 |
1983年 | 580篇 |
1982年 | 451篇 |
1979年 | 665篇 |
1978年 | 479篇 |
1977年 | 439篇 |
1976年 | 438篇 |
1975年 | 530篇 |
1974年 | 645篇 |
1973年 | 674篇 |
1972年 | 554篇 |
1971年 | 506篇 |
1970年 | 454篇 |
1969年 | 493篇 |
1968年 | 599篇 |
1967年 | 532篇 |
1966年 | 490篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
921.
Confidentiality: a survey in a research hospital 总被引:1,自引:0,他引:1
Despite the many justifications for protecting patient confidentiality, we recognize that confidentiality cannot be absolute. Our world of automated information and easy access and storage poses many threats to confidentiality. This paper has described a survey conducted at the NIH Clinical Center to assess the knowledge, attitudes, and behaviors of clinical physicians and nurses about confidentiality of patient information. The survey findings demonstrate the need for reminders and increased awareness about confidentiality in our setting. Most of the survey respondents had a good knowledge of what was expected of them, and they believed that confidentiality was important and maintaining it was their responsibility. Of interest was that in several simulated clinical situations, there was a discrepancy between what respondents indicated they should do and what they thought they would do. The biggest discrepancies appeared in situations that involved overhearing a patient conversation on the elevator, approaching an unfamiliar person who is reading a medical record in the nurses' station, and answering a patient's inquiry about the status of another patient. The findings support the speculation that this difference may be attributed to discomfort or decreased awareness, and not necessarily to lack of knowledge. Results indicate that policies and administrative expectations should be frequently communicated and enforced, and that educational programs that address issues of confidentiality should be provided. The results of this survey have been influential in guiding educational strategies and administrative activities at the clinical center. The clinical center initiated a confidentiality awareness campaign, displaying a new poster every three months in strategic locations and distributing other tangible reminders (such as pens, magnets, and buttons) containing the same confidentiality message.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
922.
923.
Chidester TR Helmreich RL Gregorich SE Geis CE 《The International journal of aviation psychology》1991,1(1):25-44
The performance of pilots can be construed as a product of skill, attitude, and personality factors. Although a great deal of effort within the aviation community has been focused on ensuring technical expertise, and new efforts highlight attitudes associated with crew coordination, personality factors have been relatively unexplored. Further, it is argued that past failures to find linkages between personality and performance were due to a combination of inadequate statistical modeling, premature performance evaluation, and/or the reliance on data gathered in contrived as opposed to realistic situations. The goal of the research presented in this article is to isolate subgroups of pilots along performance-related personality dimensions and to document limits on the impact of crew coordination training between the groups. Two samples of military pilots were surveyed in the context of training in crew coordination. Three different profiles were identified through cluster analysis of personality scales. These clusters replicated across samples and predicted attitude change following training in crew coordination. 相似文献
924.
925.
William P. Hetrick Robert C. Isenhart Derek V. Taylor Curt A. Sandman 《Behavior research methods》1991,23(1):66-71
A software program written to collect real-time, observational data is described. The flexible program allows customized behavior codes and observational durations and simultaneously records both timed and counted events. The data are collected by means of single keystrokes, automatically stored to disk with 100th of a second resolution and summarized for each observational session. The program’s database files are dBASE III PLUS compatible and may be browsed, edited, or converted to ASCII files from the program’s main menu. Field testing demonstrated the efficiency and interobserver reliability of the program (for frequency,r=0.81; for durational behaviors,rs=0.89 and 0.96). The software operates on IBM XT/AT/PS 2s and most clones with PC/MS DOS version 2.0 or greater. 相似文献
926.
927.
The second offspring of General Process Learning Theory: Overt behavior as the ambassador of the mind 总被引:2,自引:2,他引:0
下载免费PDF全文

Malone JC 《Journal of the experimental analysis of behavior》1982,38(2):205-209
Wasserman suggested in a recent book review that the study of intervening cognitive processes represents a current focus of interest in animal learning and that this has led to a revitalization of comparative psychology. An examination of the volume reviewed suggests that he may have overstated the case. Most of the authors to whom he refers expressed dissatisfaction with traditional stimulus-response associationism but few argued for the extreme (information processing) sort of cognitive approach described by Wasserman. 相似文献
928.
Performance of humans in concurrent avoidance/positive-reinforcement schedules 总被引:1,自引:1,他引:0
下载免费PDF全文

Ruddle HV Bradshaw CM Szabadi E Foster TM 《Journal of the experimental analysis of behavior》1982,38(1):51-61
Performance maintained under concurrent schedules consisting of a variable-interval avoidance component and a variable-interval positive-reinforcement component was studied in three human subjects using points exchangeable for money as the reinforcer. The rate of responding in the avoidance component increased, and the rate of responding in the positive-reinforcement component declined, as a function of the frequency of point-losses avoided in the avoidance component. The performance of all three subjects conformed to equations proposed by Herrnstein to describe behavior in concurrent schedules. The logarithms of the ratios of the response rates in the two components, and the logarithms of the ratios of the times spent in the two components, were linearly related to the logarithms of the ratios of the frequency of loss avoidance in the avoidance component to the frequency of reinforcement in the positive-reinforcement component. When a changeover delay of 5.0 sec was imposed, the slopes of the linear functions were close to 1.0 in the case of two subjects, whereas the third subject exhibited significant undermatching. For two subjects the changeover delay was then reduced to 2.0 sec; in both cases the slopes of the linear functions were lower than under the 5.0-sec condition. One subject participated in a third phase, in which no changeover delay was imposed; there was a further reduction in the slopes of the linear functions. 相似文献
929.
Pigeons were exposed to multiple schedules in which an irregular repeating sequence of five stimulus components was correlated with the same reinforcement schedule throughout. Stable, idiosyncratic, response-rate differences developed across components. Components were rank-ordered by response rate; an approximately linear relation was found between rank order and the deviation of mean response rate from the overall mean rate. Nonzero slopes of this line were found for multiple fixed-interval and variable-time schedules and for multiple variable-interval schedules both when number of reinforcements was the same in all components and when it varied. The steepest function slopes were found in the variable schedules with relatively long interfood intervals and relatively short component durations. When just one stimulus was correlated with all components of a multiple variable-interval schedule, the slope of the line was close to zero. The results suggest that food-rate differences may be induced initially by different reactions to the stimuli and subsequently maintained by food. 相似文献
930.
J A Dinsmoor K L Mueller L T Martin C A Bowe 《Journal of the experimental analysis of behavior》1982,38(3):249-263
Pigeons were exposed to stimuli correlated with the presence or absence of a variable-interval 60-second schedule of reinforcement only while they depressed a crossbar or "perch." In the first experiment, the stimuli were different tilts of a line displayed on the key. When the difference in brightness between the line and the background (salience) was maximal, seven of eight birds acquired the discrimination, but when the difference was reduced by 50%, only one succeeded. In the second experiment, wavelength of chamber illumination served as the relevant dimension. Neither experiment showed a large effect attributable to the magnitude of the difference (disparity) between the positive and the negative stimulus. Individual differences in time spent observing were positively correlated with level of discrimination in the presence of the stimuli. All birds produced the positive stimulus for a greater proportion of the available time than they did the negative stimulus. This may be the mechanism that provides selective reinforcement of observing. Finally, the formation of a discrimination was analyzed in terms of changes in the proportion of time spent in contact with the discriminative stimuli. 相似文献