全文获取类型
收费全文 | 5737篇 |
免费 | 741篇 |
国内免费 | 721篇 |
专业分类
7199篇 |
出版年
2024年 | 16篇 |
2023年 | 141篇 |
2022年 | 130篇 |
2021年 | 198篇 |
2020年 | 347篇 |
2019年 | 311篇 |
2018年 | 266篇 |
2017年 | 362篇 |
2016年 | 362篇 |
2015年 | 221篇 |
2014年 | 293篇 |
2013年 | 912篇 |
2012年 | 198篇 |
2011年 | 227篇 |
2010年 | 203篇 |
2009年 | 270篇 |
2008年 | 325篇 |
2007年 | 282篇 |
2006年 | 291篇 |
2005年 | 258篇 |
2004年 | 227篇 |
2003年 | 197篇 |
2002年 | 182篇 |
2001年 | 135篇 |
2000年 | 122篇 |
1999年 | 106篇 |
1998年 | 74篇 |
1997年 | 75篇 |
1996年 | 52篇 |
1995年 | 56篇 |
1994年 | 53篇 |
1993年 | 32篇 |
1992年 | 22篇 |
1991年 | 33篇 |
1990年 | 26篇 |
1989年 | 21篇 |
1988年 | 22篇 |
1987年 | 17篇 |
1986年 | 13篇 |
1985年 | 16篇 |
1984年 | 20篇 |
1983年 | 8篇 |
1982年 | 7篇 |
1981年 | 8篇 |
1980年 | 13篇 |
1979年 | 8篇 |
1978年 | 12篇 |
1977年 | 12篇 |
1976年 | 7篇 |
1975年 | 8篇 |
排序方式: 共有7199条查询结果,搜索用时 0 毫秒
811.
ENRIQUE BALLESTERO 《Journal of Multi-Criteria Decision Analysis》1997,6(1):11-16
Nowadays, utility theory and compromise programming (CP) are considered very different paradigms and methodologies to measure preferences as well as to determine decision maker's optima on an efficient frontier. In this paper, however, we show that a utility function with separate variables (presented in the form of a Taylor series around the ideal point) is reducible to a weighted sum of CP distances. This linkage between utility and compromise (based on a main assumption in which the usual utility functions hold) leads to (i) a method for specification and optimization of usual utility functions by operational technique and (ii) a reformulation of standard CP with the advantage of determining the best CP solution from a utility perspective. © 1997 John Wiley & Sons, Ltd. 相似文献
812.
In polymorphic ants, such as Cataglyphis niger, sterile individual workers from the same nest show some degree of variation in size and/or morphology. We studied whether worker size and size difference between opponents had an effect on aggression during conspecific encounters. Although the capacity to recognize nestmates was shared by all individuals, some patterns of agonistic behaviors were size related. Escape was mostly displayed by the small workers, and threat, associated with ritualized fights, by the large workers. As game theory predicted, ants of C. niger adjusted their level of aggression as a function of the size of the opponent. However, only large individuals used such assessment strategies, responding with escalation of aggression towards small workers and reduction of aggression towards large ones. On the contrary, small individuals behaved in the same manner whatever the opponent's size. Differences between both morphological castes were discussed with reference to the resource holding assessment models. Aggr. Behav. 25:369–379, 1999. © 1999 Wiley‐Liss, Inc. 相似文献
813.
814.
Kenneth F. Schaffner 《Theoretical medicine and bioethics》1992,13(2):191-216
This two-part article examines the competition between the clonal selection theory and the instructive theory of the immune response from 1957–1967. In Part I the concept of a temporally extended theory is introduced, which requires attention to the hitherto largely ignored issue of theory individuation. Factors which influence the acceptability of such an extended theory at different temporal points are also embedded in a Bayesian framework, which is shown to provide a rational account of belief change in science. In Part II these factors, as elaborated in the Bayesian framework, are applied to the case of the success of the clonal selection theory and the failure of the instructive theory. 相似文献
815.
PETER LAM HERBERT MOSKOWITZ THOMAS EPPEL JEN TANG 《Journal of Multi-Criteria Decision Analysis》1997,6(1):25-40
Traditionally, parameters of multiattribute utility models, representing a decision maker's preference judgements, are treated deterministically. This may be unrealistic, because assessment of such parameters is potentially fraught with imprecisions and errors. We thus treat such parameters as stochastic and investigate how their associated imprecision/errors are propagated in an additive multiattribute utility function in terms of the aggregate variance. Both a no information and a rank order case regarding the attribute weights are considered, assuming a uniform distribution over the feasible region of attribute weights constrained by the respective information assumption. In general, as the number of attributes increases, the variance of the aggregate utility in both cases decreases and approaches the same limit, which depends only on the variances as well as the correlations among the single-attribute utilities. However, the marginal change in aggregate utility variance decreases rather rapidly and hence decomposition as a variance reduction mechanism is generally useful but becomes relatively ineffective if the number of attributes exceed about 10. Moreover, it was found that utilities which are positively correlated increase the aggregate utility variance, hence every effort should be made to avoid positive correlations between the single-attribute utilities. We also provide guidelines for determining under what condition and to what extent a decision maker should decompose to obtain an aggregate utility variance that is smaller than that of holistic assessments. Extensions of the current model and empirical research to support some of our behavioural assumptions are discussed. © 1997 John Wiley & Sons, Ltd. 相似文献
816.
正确认识马克思的道德理论在其思想体系中的地位,关系到对整个马克思思想及其贡献的理解。针对中外学界对这一问题的种种不同看法和误解,本文认为,伦理道德是马克思一生学术实践所关注的,是马克思思想体系的灵魂,自由与解放则是马克思道德研究及其整个思想体系的主旨。 相似文献
817.
计划行为模型在HIV性风险行为领域的应用与发展* 总被引:2,自引:0,他引:2
整理和回顾了计划行为模型在HIV性风险行为领域的应用与进展。该模型在不同文化背景、不同样本中,对于HIV性风险行为呈现良好的解释力,但是其整体预测力及内部变量的显著程度仍不时波动。21世纪以来,通过核心变量操作化、新变量引入和结构关系调整,模型获得了较大的扩展和完善。但在模型效度再检验、纳入社会性别视角、克服个体行为模型缺陷,以及强化模型的干预适用性方面仍有较大的发展空间 相似文献
818.
近几年诸多研究者认为阅读障碍是由于视觉系统巨细胞功能缺陷引起的。他们从对比度敏感性研究、巨细胞抑制功能研究与视觉运动知觉功能的研究结果中得到了支持证据。就这个问题的研究进行综述,表明不论是巨细胞功能缺陷理论的支持者还是反对者,都从巨细胞的对比度敏感性、视觉运动知觉与巨细胞抑制功能上得到了一些研究结果的支持。巨细胞功能缺陷理论的支持者还从阅读障碍的神经生理学研究和阅读的脑功能研究中得到了一些支持性的证据。新的研究结果揭示了巨细胞系统缺陷理论与阅读之间的关系以及巨细胞系统缺陷理论的应用价值。在巨细胞系统缺陷理论的进一步研究中,还需要统一实验方法与实验标准以获得更多的证据,同时需要有新的方法来有效区分小细胞系统与巨细胞系统 相似文献
819.
Expectation-based syntactic comprehension 总被引:2,自引:0,他引:2
Levy R 《Cognition》2008,106(3):1126-1177
This paper investigates the role of resource allocation as a source of processing difficulty in human sentence comprehension. The paper proposes a simple information-theoretic characterization of processing difficulty as the work incurred by resource reallocation during parallel, incremental, probabilistic disambiguation in sentence comprehension, and demonstrates its equivalence to the theory of Hale [Hale, J. (2001). A probabilistic Earley parser as a psycholinguistic model. In Proceedings of NAACL (Vol. 2, pp. 159-166)], in which the difficulty of a word is proportional to its surprisal (its negative log-probability) in the context within which it appears. This proposal subsumes and clarifies findings that high-constraint contexts can facilitate lexical processing, and connects these findings to well-known models of parallel constraint-based comprehension. In addition, the theory leads to a number of specific predictions about the role of expectation in syntactic comprehension, including the reversal of locality-based difficulty patterns in syntactically constrained contexts, and conditions under which increased ambiguity facilitates processing. The paper examines a range of established results bearing on these predictions, and shows that they are largely consistent with the surprisal theory. 相似文献
820.
Reactive and proactive aggression: Similarities and differences 总被引:2,自引:1,他引:2
The purpose of the current study was to elaborate the nomological net surrounding the constructs of reactive (RA) and proactive aggression (PA). Typically examined in the context of children, the current study utilized a sample of 211 young adults to examine the relations between reactive and proactive aggression and measures of general personality and social information processing, as well as maladaptive behavioral correlates such as crime, substance use, and riskier sex. Both raw and residualized scores were examined. Using raw scores, the primary differences between RA and PA were related to Neuroticism (i.e., RA more strongly related) and externalizing behaviors (i.e., PA more strongly). The authors comment on the similarity of findings when using raw scores and the divergence of findings using residualized scores and argue for a cautious interpretation of differences based on residualized scores. The authors conclude that the role of Neuroticism warrants further exploration as a means for understanding the heterogeneity of aggressive behavior. 相似文献