全文获取类型
收费全文 | 8099篇 |
免费 | 113篇 |
专业分类
管理学 | 1200篇 |
民族学 | 29篇 |
人口学 | 778篇 |
丛书文集 | 27篇 |
理论方法论 | 606篇 |
综合类 | 107篇 |
社会学 | 3462篇 |
统计学 | 2003篇 |
出版年
2020年 | 118篇 |
2019年 | 157篇 |
2018年 | 220篇 |
2017年 | 277篇 |
2016年 | 195篇 |
2015年 | 135篇 |
2014年 | 192篇 |
2013年 | 1341篇 |
2012年 | 260篇 |
2011年 | 247篇 |
2010年 | 183篇 |
2009年 | 173篇 |
2008年 | 148篇 |
2007年 | 186篇 |
2006年 | 166篇 |
2005年 | 168篇 |
2004年 | 153篇 |
2003年 | 149篇 |
2002年 | 157篇 |
2001年 | 199篇 |
2000年 | 195篇 |
1999年 | 175篇 |
1998年 | 131篇 |
1997年 | 130篇 |
1996年 | 126篇 |
1995年 | 106篇 |
1994年 | 104篇 |
1993年 | 98篇 |
1992年 | 140篇 |
1991年 | 121篇 |
1990年 | 117篇 |
1989年 | 112篇 |
1988年 | 97篇 |
1987年 | 91篇 |
1986年 | 96篇 |
1985年 | 107篇 |
1984年 | 112篇 |
1983年 | 126篇 |
1982年 | 98篇 |
1981年 | 91篇 |
1980年 | 86篇 |
1979年 | 95篇 |
1978年 | 92篇 |
1977年 | 80篇 |
1976年 | 68篇 |
1975年 | 67篇 |
1974年 | 59篇 |
1973年 | 58篇 |
1972年 | 41篇 |
1971年 | 49篇 |
排序方式: 共有8212条查询结果,搜索用时 15 毫秒
81.
LetX1,X2, ..., be real-valued random variables forming a strictly stationary sequence, and satisfying the basic requirement of being either pairwise positively quadrant dependent or pairwise negatively quadrant dependent. LetF^ be the marginal distribution function of theXips, which is estimated by the empirical distribution functionFn and also by a smooth kernel-type estimateFn, by means of the segmentX1, ...,Xn. These estimates are compared on the basis of their mean squared errors (MSE). The main results of this paper are the following. Under certain regularity conditions, the optimal bandwidth (in the MSE sense) is determined, and is found to be the same as that in the independent identically distributed case. It is also shown thatn MSE(Fn(t)) andnMSE (F^n(t)) tend to the same constant, asn→∞ so that one can not discriminate be tween the two estimates on the basis of the MSE. Next, ifi(n) = min {k∈{1, 2, ...}; MSE (Fk(t)) ≤ MSE (Fn(t))}, then it is proved thati(n)/n tends to 1, asn→∞. Thus, once again, one can not choose one estimate over the other in terms of their asymptotic relative efficiency. If, however, the squared bias ofF^n(t) tends to 0 sufficiently fast, or equivalently, the bandwidthhn satisfies the requirement thatnh3n→ 0, asn→∞, it is shown that, for a suitable choice of the kernel, (i(n) ?n)/(nhn) tends to a positive number, asn→∞ It follows that the deficiency ofFn(t) with respect toF^n(t),i(n) ?n, is substantial, and, actually, tends to ∞, asn→∞. In terms of deficiency, the smooth estimateF^n(t) is preferable to the empirical distribution functionFn(t) 相似文献
82.
Robert Aslett Robert J. Buck Steven G. Duvall Jerome Sacks & William J. Welch 《Journal of the Royal Statistical Society. Series C, Applied statistics》1998,47(1):31-48
In electrical engineering, circuit designs are now often optimized via circuit simulation computer models. Typically, many response variables characterize the circuit's performance. Each response is a function of many input variables, including factors that can be set in the engineering design and noise factors representing manufacturing conditions. We describe a modelling approach which is appropriate for the simulator's deterministic input–output relationships. Non-linearities and interactions are identified without explicit assumptions about the functional form. These models lead to predictors to guide the reduction of the ranges of the designable factors in a sequence of experiments. Ultimately, the predictors are used to optimize the engineering design. We also show how a visualization of the fitted relationships facilitates an understanding of the engineering trade-offs between responses. The example used to demonstrate these methods, the design of a buffer circuit, has multiple targets for the responses, representing different trade-offs between the key performance measures. 相似文献
83.
BRUCE G. LINSTER 《Economic inquiry》1998,36(1):98-107
We explore how natural selection acts upon genes for cooperation, altruism and selfishness in an prisoner's dilemma played by family members. A key parameter determining behavior is that parents and children have different expectations of future offspring. Examining asexual and sexually reproducing populations we show that which strategy of cooperation and defection proves be stable depends on the relative reproduction potential of the players and what proportion of the population is young. "Rotten kids" with altruistic parents can be a stable outcome where reproductive success is the goal, and natural selection may lead individuals to care about their unborn progeny. (JEL D10, H31) 相似文献
84.
This study examines the impact of mandatory seat belt laws on fatal and incapacitating injury rates in the states. Annual data for all 50 states for the period 1975-1991 are used. Pooled time series analysis is employed. The general conclusion that emerges from this analysis is that seat belt laws significantly impact state fatal injury rates. Primary enforcement and all-seat coverage provisions appear to be particularly effective in reducing fatality rates. 相似文献
85.
The need for long-term care is driven both by the growth of the elderly population and changes in the age relations of morbidity, disability, and mortality. Data show these relations changed in the U.S. elderly population from 1982 to 1989. Chronic disability prevalence declined between the 1982 and 1989 U.S. National Long Term Care Surveys. Among those impaired, many persons using personal assistance to meet their needs shifted to the use of assisted housing and special equipment. The relation of these trends to other changes--such as the increasing educational level of the elderly population--is examined to estimate how future changes in disability and morbidity may affect the demand for long-term care. Disabilities at specific times as well as their transition rates were examined to determine how long individuals need long-term care. The analyses suggest that, while the amount of long-term care services needed will increase rapidly, the types and amounts of services used by the U.S. elderly population will undergo significant change. 相似文献
86.
SupposeL(X) is the law of a positive random variableX, andZ is positive and independent ofX. Admissible solution pairs (L(X),L(Z)) are sought for the in-law equation $\hat X \cong X o Z$ °Z, where $L\left( {\hat X} \right)$ is a weighted law constructed fromL(X), and ° is a binary operation which in some sense is increasing. The class of weights includes length biasing of arbitrary order. When ° is addition and the weighting is ordinary length biasing, the class of admissibleL(X) comprises the positive infinitely divisible laws. Examples are given subsuming all known specific cases. Some extensions for general order of length-biasing are discussed. 相似文献
87.
Assimilation and its discontents: between rhetoric and reality 总被引:2,自引:0,他引:2
Rumbaut RG 《The International migration review》1997,31(4):923-960
"It is in [the] conceptual interstices between theory, rhetoric, and reality that paradoxes (or at least what may appear as paradoxes) emerge. By focusing on paradoxes--on evidence that contradicts orthodox expectations and points instead to assimilation's discontents--the aim of this article is to test empirically the conception of assimilation as a linear process leading to improvements in immigrant outcomes over time and generation in the United States, to unmask underlying pre-theoretical ethnocentric pretensions, and to identify areas in need of conceptual, analytical and theoretical refinement. It is precisely through the examination of paradoxical cases--in effect, deviant case analyses--that fruitful reformulations can be stimulated, considered, and advanced." 相似文献
88.
89.
"In this paper, we use simulation models to demonstrate the complexity of the relationship between the marriage selection process and the resulting RMRs [relative mortality ratios]. In particular, we show that marriage selection alone can produce a relative mortality ratio which remains large and relatively constant at ages far beyond the marriage span....Our general objective...is to determine the range of age patterns of relative mortality which could, in theory, result from marriage selection on the basis of health characteristics. We also evaluate the effects of variations in the marriage selection mechanisms on the resulting mortality patterns....We develop and apply several simple mathematical models of the marriage selection process. In order to distinguish the potential consequences of marriage selection from marriage protection, we consider hypothetical populations in which causal effects are absent....We begin by considering an extremely simple marriage selection process and subsequently explore a more realistic selection model based on recent death and marriage rates for Japan." 相似文献
90.
Many clients who participate in family therapy have experienced trauma such as physical and sexual abuse in their families of origin. Extensive literature suggests that abusive experiences can result in post-traumatic stress disorders, depression, anxiety, personality disorders, and other long-term effects. Without recognition of the effects that abuse can have on individuals, it is possible to misdiagnose clients or fail to provide them with adequate assistance. This study is an attempt to compare the symptomology of nonabused clients with physically and sexually abused clients using an empirically sound measure. The results demonstrate that the majority of clients who experienced physical and/or sexual abuse in their backgrounds scored in the clinical range on scales from the Millon Clinical Multiaxial Instrument (MCMI) (Millon, 1984). In contrast, clients who did not report abuse had significantly lower scores than the abused clients, and the majority of the nonabused clients scored in the nonclinical range on the scales of the MCMI. Treatment and theoretical implications surrounding the issues of abuse are discussed, and recommendations for marriage and family therapists are provided. 相似文献