全文获取类型
收费全文 | 21194篇 |
免费 | 21篇 |
国内免费 | 1篇 |
出版年
2018年 | 3485篇 |
2017年 | 2822篇 |
2016年 | 2252篇 |
2015年 | 191篇 |
2014年 | 83篇 |
2013年 | 150篇 |
2012年 | 581篇 |
2011年 | 2395篇 |
2010年 | 2519篇 |
2009年 | 1475篇 |
2008年 | 1714篇 |
2007年 | 2180篇 |
2006年 | 41篇 |
2005年 | 227篇 |
2004年 | 174篇 |
2003年 | 133篇 |
2002年 | 85篇 |
2001年 | 49篇 |
2000年 | 66篇 |
1999年 | 28篇 |
1998年 | 29篇 |
1997年 | 28篇 |
1996年 | 11篇 |
1995年 | 10篇 |
1994年 | 10篇 |
1993年 | 10篇 |
1992年 | 12篇 |
1990年 | 23篇 |
1989年 | 11篇 |
1987年 | 11篇 |
1985年 | 12篇 |
1984年 | 15篇 |
1983年 | 10篇 |
1982年 | 10篇 |
1981年 | 13篇 |
1980年 | 14篇 |
1978年 | 16篇 |
1976年 | 9篇 |
1975年 | 10篇 |
1974年 | 9篇 |
1973年 | 16篇 |
1972年 | 13篇 |
1969年 | 11篇 |
1966年 | 15篇 |
1964年 | 12篇 |
1963年 | 10篇 |
1961年 | 10篇 |
1958年 | 10篇 |
1956年 | 11篇 |
1953年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
191.
Ecological valence theory (EVT; Palmer & Schloss, Proceedings of the National Academy of Sciences 107:8877–8882, 2010) proposes that color preferences are due to affective responses to color-associated objects: That is, people generally like
colors to the degree that they like the objects associated with those colors. Palmer and Schloss found that the average valence
of objects associated with a color, when weighted by how well the objects matched the color (weighted affective valence estimates:
WAVE) explained 80% of the variation in preference across colors. Here, we replicated and extended Palmer and Schloss’s investigation
to establish whether color–object associations can account for sex differences in color preference and whether the relationship
between associated objects and color preference is equally strong for males and females. We found some degree of sex specificity
to the WAVEs, but the relationship between WAVE and color preference was significantly stronger for males than for females
(74% shared variance for males, 45% for females). Furthermore, analyses identified a significant inverse relationship between
the number of objects associated with a color and preference for the color. Participants generally liked colors associated
with few objects and disliked colors associated with many objects. For the sample overall and for females alone, this association
was not significantly weaker than the association of the WAVE and preference. The success of the WAVE at capturing color preference
was partly due to the relationship between the number of associated objects and color preference. The findings identify constraints
of EVT in its current form, but they also provide general support for the link between color preference and color–object associations. 相似文献
192.
The objective of the study is to assess views of age related changes in sexual behavior among married Thai adults age 53–57.
Results are viewed in the context of life course theory. In-depth interviews were conducted with 44 Thai adults in Bangkok
and the four regions of Thailand. Topics covered include changing sexual behavior with age, adjustment to this change, gender
differences in behavior, attitudes toward commercial sex and other non-marital sexual partners, and condom use. Most respondents
were aware of this change and saw a decrease in sexual activity and desire more often among women compared to men. At the
same time, many respondents viewed sexuality as important to a marriage. Some respondents accepted the decrease in sexual
activity and focused more on work, family and temple activities. Thai Buddhism was seen as an important resource for people
who were dealing with changes due to aging. Other persons turned to other partners including both commercial and non-commercial
partners. The influence of the HIV epidemic that began in the 1990s was seen in concerns about disease transmission with extramarital
partners and consequent attitudes toward condom use. The acceptability of extramarital partners in the family and community
ranged from acceptance to strong disapproval of extramarital relationships. 相似文献
193.
The recent trend in the feminization of the HIV epidemic poses great risk to women, especially to the wives of men who have
sex with men (MSM). The objective of the present study was to explore wives’ responses to their husbands’ sexual orientation
as well as the factors that influence their sexual health in India. For this research, 15 wives who were aware of their husbands’
sexual orientation and their husbands were interviewed separately using semi-structured in-depth interviews and focus groups.
The study explored the social and cultural structures that create gender inequality, which put women married to MSM at sexual
health risk. These factors need to be addressed carefully through existing MSM targeted interventions, without breaching the
confidentiality of either partner. 相似文献
194.
Between 1998 and 2006, twenty-seven states amended their constitutions to prohibit same sex marriage. The 2008 elections again
saw three states with ballot measures aimed at banning gay marriage. This study examines the determinants of support for those
measures in California and Florida, and includes a similar measure placed on the primary election ballot in California in
2000. Support is measured as the county-wide vote in favor of each gay marriage ban. A number of hypotheses are explored that
examine the urban/rural nature of each county, as well as the political and demographic characteristics of county residents.
It is suggested that states may be best viewed as relatively independent groupings of diverse subcultures, rather than as
homogenous populations with a single political culture. The findings reported here indicate that a host of demographic, political
and religious differences within each state influence residents’ votes on gay marriage bans. 相似文献
195.
Polder-Verkiel SE 《Science and engineering ethics》2012,18(1):117-141
In 2008 a young man committed suicide while his webcam was running. 1,500 people apparently watched as the young man lay dying:
when people finally made an effort to call the police, it was too late. This closely resembles the case of Kitty Genovese
in 1964, where 39 neighbours supposedly watched an attacker assault and did not call until it was too late. This paper examines
the role of internet mediation in cases where people may or may not have been good Samaritans and what their responsibilities
were. The method is an intuitive one: intuitions on the various potentially morally relevant differences when it comes to
responsibility between offline and online situations are examined. The number of onlookers, their physical nearness and their
anonymity have no moral relevance when it comes to holding them responsible. Their perceived reality of the situation and
ability to act do have an effect on whether we can hold people responsible, but this doesn’t seem to be unique to internet
mediation. However the way in which those factors are intrinsically connected to internet mediation does seem to have a diminishing
effect on responsibility in online situations. 相似文献
196.
197.
The Bengalese finch (Lonchura striata var. domestica) is a species of songbird. Males sing courtship songs with complex note-to-note transition rules, while females discriminate
these songs when choosing their mate. The present study uses serial reaction time (RT) to examine the characteristics of the
Bengalese finches’ sequential behaviours beyond song production. The birds were trained to produce the sequence with an “A–B–A”
structure. After the RT to each key position was determined to be stable, we tested the acquisition of the trained sequential
response by presenting novel and random three-term sequences (random test). We also examined whether they could abstract the
embedded rule in the trained sequence and apply it to the novel test sequence (abstract test). Additionally, we examined rule
abstraction through example training by increasing the number of examples in baseline training from 1 to 5. When considered
as (gender) groups, training with 5 examples resulted in no statistically significant differences in the abstract tests, while
statistically significant differences were observed in the random tests, suggesting that the male birds learned the trained
sequences and transferred the abstract structure they had learned during the training trials. Individual data indicated that
males, as opposed to females, were likely to learn the motor pattern of the sequence. The results are consistent with observations
that males learn to produce songs with complex sequential rules, whereas females do not. 相似文献
198.
Non-human primates possess species-specific repertoires of acoustically distinct call types that can be found in adults in
predictable ways. Evidence for vocal flexibility is generally rare and typically restricted to acoustic variants within the
main call types or sequential production of multiple calls. So far, evidence for context-specific call sequences has been
mainly in relation to external disturbances, particularly predation. In this study, we investigated extensively the vocal
behaviour of free-ranging and individually identified Diana monkeys in non-predatory contexts. We found that adult females
produced four vocal structures alone (‘H’, ‘L’, ‘R’ and ‘A’ calls, the latter consisting of two subtypes) or combined in non-random
ways (‘HA’, ‘LA’ and ‘RA’ call combinations) in relation to ongoing behaviour or external events. Specifically, the concatenation
of an introductory call with the most frequently emitted and contextually neutral ‘A’ call seems to function as a contextual
refiner of this potential individual identifier. Our results demonstrate that some non-human primates are able to increase
the effective size of their small vocal repertoire not only by varying the acoustic structure of basic call types but also
by combining them into more complex structures. We have demonstrated this phenomenon for a category of vocalisations with
a purely social function and discuss the implications of these findings for evolutionary theories of primate vocal communication. 相似文献
199.
It has been speculated that cage mesh exerts a shaping influence on reaching behavior by captive apes, which is then misconstrued
as pointing by human observers. Although this notion is clearly falsified by the pointing of captive language-trained apes—who
point in the absence of intervening cage mesh—nevertheless, the degree to which cage mesh might influence pointing hand shapes
by captive great apes in other housing environments remains relatively unexplored. We examined 259 pointing gestures displayed
in archival footage from over 18 h of observation by three nonlanguage-trained chimpanzees housed at a biomedical research
center. We coded points in relation to how close to the boundaries of the diamond-shaped cage mesh their points were displayed.
We found that points with the whole hand were significantly more likely to be displayed away from the mesh boundaries, relative
to points with the index finger or other single-digit points. However, points of each hand shape were displayed at each location,
demonstrating that these physical parameters do not fully account for the number of fingers extended while pointing by chimpanzees. 相似文献
200.
Although rats are able to build complex spatial representations of their surroundings during exploration, the nature of the
encoded information is still a matter for debate. In particular, it is not well established if rats can process the topological
structure of the environment in such a way that they are aware of the connections existing between remote places. Here, rats
were first exposed for four 5-min trials to a complex environment divided into several sectors that were separated by doors
allowing either unrestricted or restricted access to other sectors. In the fifth test trial, we measured the behavior of the
animals while they explored the same environment in which, however, they faced changes that either altered or did not alter
the topological structure of the environment. In experiment 1, closing previously opened doors prevented the rat from having
direct access between corresponding sectors. In experiment 2, opening previously closed doors allowed direct access between
sectors that had not been directly accessible. In each experiment, control doors allowed us to discard the mere influence
of door manipulation. We compared the rats’ exploratory behavior in response to door manipulations that either strongly altered
or did not alter the ability to commute between sectors and found evidence that the animals displayed differential reactions
to the two types of door manipulations. This implies that during exploration rats build a precise map of the connectivity
of space that can be flexibly updated and used for efficient navigation. 相似文献