全文获取类型
收费全文 | 22978篇 |
免费 | 2163篇 |
国内免费 | 1687篇 |
专业分类
26828篇 |
出版年
2024年 | 46篇 |
2023年 | 412篇 |
2022年 | 383篇 |
2021年 | 520篇 |
2020年 | 918篇 |
2019年 | 987篇 |
2018年 | 856篇 |
2017年 | 1065篇 |
2016年 | 1056篇 |
2015年 | 665篇 |
2014年 | 885篇 |
2013年 | 2735篇 |
2012年 | 572篇 |
2011年 | 752篇 |
2010年 | 563篇 |
2009年 | 859篇 |
2008年 | 1083篇 |
2007年 | 1076篇 |
2006年 | 1018篇 |
2005年 | 919篇 |
2004年 | 755篇 |
2003年 | 667篇 |
2002年 | 614篇 |
2001年 | 400篇 |
2000年 | 369篇 |
1999年 | 318篇 |
1998年 | 241篇 |
1997年 | 202篇 |
1996年 | 172篇 |
1995年 | 162篇 |
1994年 | 150篇 |
1993年 | 117篇 |
1992年 | 87篇 |
1991年 | 74篇 |
1990年 | 66篇 |
1989年 | 46篇 |
1988年 | 55篇 |
1985年 | 381篇 |
1984年 | 430篇 |
1983年 | 352篇 |
1982年 | 460篇 |
1981年 | 451篇 |
1980年 | 453篇 |
1979年 | 403篇 |
1978年 | 457篇 |
1977年 | 362篇 |
1976年 | 361篇 |
1975年 | 273篇 |
1974年 | 278篇 |
1973年 | 236篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
Genetic counselors have participated in the Michigan Newborn Screening Program on a contractual basis since 1988. Their role includes newborn screening education and training, newborn nursery site visits, and monitoring newborn screening in hospitals. Their impact has been to improve the quality of newborn screening services by reducing errors and increasing completion of data fields on newborn screening cards, improving hospital nursery cooperation and problem solving, and enhancing health department response to specific problems. 相似文献
32.
A new method for determining the minimum number of observations per subject needed to achieve a specific generalizability coefficient is presented. This method, which consists of a branch-and-bound algorithm, allows for the employment of constraints specified by the investigator. 相似文献
33.
We propose a method for detecting influential observations in iterative principal factor analysis. For this purpose we derive the influence functionsI(x; LL
T
) andI(x; ) for the common variance matrixT =LL
T
and the unique variance matrix , respectively, in the common factor decomposition =LL
T
+ . A numerical example is given for illustration.The authors are grateful to Tomoyuki Tarumi and Atsuhiro Hayashi for their kind permission to use their software Seto/B for drawing Figures 1 and 2 and to anonymous reviewers for comments on the paper. 相似文献
34.
Bengt O. Muthén 《Psychometrika》1989,54(3):385-396
The problem of detecting instructional sensitivity (item basis) in test items is considered. An illustration is given which shows that for tests with many biased items, traditional item bias detection schemes give a very poor assessment of bias. A new method is proposed instead. This method extends item response theory (IRT) by including item-specific auxiliary measurement information related to opportunity-to-learn. Item-specific variation in measurement relations across students with varying opportunity-to-learn is allowed for.This paper was presented at the 1987 AERA meeting in Washington, DC. This research was supported by grant OERI-G-86-003 from the Office of Educational Research and Improvement, Department of Education. The author thanks Michael Hollis and Chih-fen Kao for valuable research assistance, and appreciates valuable comments made by an anonymous reviewer. 相似文献
35.
Hwe Ik Zhang 《Zygon》1989,24(4):447-456
Abstract. The position and role of humanity in the world of life is examined in the light of the ontological structure of life itself. This problem is approached by considering the possible units of life representing various modes of life phenomena. I argue that the only meaningful unit of life without interposing some special external conditions is "global life" framed in a star-planet system. Any other possible unit of life exhibited by various kinds of individuals is conditional in the sense that it would leave out an essential part as "co-life." The relationship between human being and the global life should be understood in this general scheme of individual and global life. It is emphasized, however, that human being occupies a unique position in global life in the sense that humanity can promote either a cancerous situation or a healthy higher-order enhancement of the global life. 相似文献
36.
Philip Clayton 《Zygon》1989,24(3):315-334
Abstract. Imre Lakatos's philosophy of science can provide helpful leads for theological methodology, but only when mediated by the disciplines that lie between the natural sciences and theology. The questions of relativism and truth are used as indices for comparing disciplines, and Lakatos's theory of natural science is taken as the starting point. Major modifications of Lakatos's work are demanded as one moves from the natural sciences, through economics, the interpretive social sciences, literary theory, and into theology. Although theology may consist of Lakatosian research programs, it also includes programs of interpretation and programs for living. This conclusion must influence our definition of theological truth and our assessment of theological relativism. 相似文献
37.
38.
Visually guided catching and tracking skills in pigeons: A preliminary analysis 总被引:2,自引:1,他引:1 下载免费PDF全文
Research on reaching, tracking, and catching in the pigeon has been hampered by limitations of technology. A new system was developed in which the target was a small rectangle presented on a video display terminal and the pecking response was detected with touch technology. The target moved up and down vertically with sinusoidal velocity. A coincidence between the location of the pigeon's beak and the cursor produced reinforcement. The pigeon pecked ahead and behind the target, but most pecks occurred behind the target so the dominant tracking strategy was lagging. The pigeon was adept at “catching” the target at many locations throughout the trajectory. Transfer of motor learning was tested on probe trials during which the trajectory changed from vertical to horizontal. On transfer trials the pigeons' dominant pattern of pecking immediately shifted from vertical to horizontal. The motor skill displayed by the pigeons was flexible and adaptive, suggesting that the pigeons had learned to track the cursor. 相似文献
39.
In this study, we investigated the conditions that contribute to observational learning of generalized language in children with severe mental retardation. Matrix-training strategies were used to teach 6 children with mental retardation to combine known words into two- or three-word utterances consistent with syntactic rules. Subsequently, the children learned two or more unknown words concurrently, inducing word-referent relations consistent with these word order rules. Generalized learning of responses not taught directly was shown to be under experimental control using a multiple baseline design across submatrices. Expressive modeling of only four or five responses was sufficient to promote recombinative generalization in the expressive and receptive modalities. Thus, 95% to 98% of subjects' learning was attributed to generalization processes. This study demonstrates how the efficiency of language training with children with mental retardation might be enhanced by coupling observational learning and matrix-training strategies. 相似文献
40.
David M Schweiger Carl R Anderson Edwin A Locke 《Organizational behavior and human decision processes》1985,36(2):245-272
Two studies using a computer-simulated, strategy-formulation game and business students were conducted using simultaneous verbal protocols. It was found that a number of information-processing and information-evaluation thought processes were significantly related to game performance. Consistent with what is known about individual decision making, the present results suggest that, for the task used in this study, individuals who engage in causal analysis perform better than those who do not. But those who focus on negative emotions, blindly repeat previously successful decisions, and engage in illogical through processes perform more poorly than those who do not. Causal replication using real managers within organizational settings, however, is needed before firm conclusions can be drawn from this research. 相似文献