全文获取类型
收费全文 | 30599篇 |
免费 | 1116篇 |
国内免费 | 14篇 |
专业分类
31729篇 |
出版年
2020年 | 334篇 |
2019年 | 373篇 |
2018年 | 504篇 |
2017年 | 554篇 |
2016年 | 583篇 |
2015年 | 440篇 |
2014年 | 499篇 |
2013年 | 2396篇 |
2012年 | 930篇 |
2011年 | 943篇 |
2010年 | 567篇 |
2009年 | 601篇 |
2008年 | 850篇 |
2007年 | 803篇 |
2006年 | 678篇 |
2005年 | 672篇 |
2004年 | 635篇 |
2003年 | 618篇 |
2002年 | 620篇 |
2001年 | 750篇 |
2000年 | 742篇 |
1999年 | 540篇 |
1998年 | 304篇 |
1997年 | 280篇 |
1992年 | 495篇 |
1991年 | 480篇 |
1990年 | 479篇 |
1989年 | 480篇 |
1988年 | 424篇 |
1987年 | 446篇 |
1986年 | 462篇 |
1985年 | 503篇 |
1984年 | 426篇 |
1983年 | 389篇 |
1982年 | 283篇 |
1981年 | 327篇 |
1979年 | 459篇 |
1978年 | 328篇 |
1977年 | 294篇 |
1976年 | 286篇 |
1975年 | 417篇 |
1974年 | 469篇 |
1973年 | 498篇 |
1972年 | 417篇 |
1971年 | 418篇 |
1970年 | 382篇 |
1969年 | 410篇 |
1968年 | 504篇 |
1967年 | 486篇 |
1966年 | 463篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
We obtain in this paper a representation of the formulae of extensions ofL
by generalized quantifiers through functors between categories of first-order structures and partial isomorphisms. The main tool in the proofs is the back-and-forth technique. As a corollary we obtain the Caicedo's version of Fraïssés theorem characterizing elementary equivalence for such languages. We also discuss informally some geometrical interpretations of our results. 相似文献
82.
83.
M H Kelly J K Bock 《Journal of experimental psychology. Human perception and performance》1988,14(3):389-403
The goals of this research were to determine whether speakers adjust the stress patterns of words within sentences to create an alternation between strong and weak beats and to explore whether this rhythmic alternation contributes to the characteristics stress differences between two major lexical categories of English. Two experiments suggested that speakers do alter lexical stress in accordance with rhythmic biases. When speakers produced disyllabic pseudowords in sentence contexts, they were more likely to place stress on the first syllable when the pseudoword was preceded by a weak stress and followed by a strong one than when the strong stress preceded and the weak followed. This occurred both when the pseudowords served as nouns and when they served as verbs. Text analyses further revealed that weakly stressed elements precede nouns more often than verbs, whereas such elements follow verbs more often than nouns. Thus, disyllabic nouns are more likely than disyllabic verbs to occupy contexts biased toward trochaic rhythm, a finding consistent with leftward dominant stress in disyllabic English nouns. The history of stress changes in English nouns and verbs also conforms with the view that rhythmic context may have contributed to the evolution of stress differences. Together, the findings suggest that the citation stress patterns of words may to some degree reflect adaptations of lexical knowledge to conditions of language performance. 相似文献
84.
Fighting pairs of isolated DBA/2 mice showed a significant increase in tail-flick response latencies independent of whether opponents were losing or winning the combat. The effect lasted less than 10 min in both animals. Elevated pain thresholds were also found in isolates that attacked a nonaggressive conspecific, and were prevented by naltrexone (0.2 mg/kg), while a larger dose (1.0 mg/kg) inhibited the attack behavior. A small increase in pain threshold was observed after exposure of isolates to the test box alone, while isolation per se had no effect on baseline tail-flick latencies. The data demonstrate that endogenous pain suppressing systems are activated during attack and suggest that this opioid-mediated antinociception is a correlate of the isolation syndrome, reflecting enhanced arousal of the attacking animal. 相似文献
85.
The influence of affect on causal attributions for success and failure was examined in this experiment. A positive, neurtral, or negative mood was induced in subjects who then learned they had either succeeded or failed an aptitude test taken previously. Relative to neutral mood control conditions, subjects in both positive and negative mood conditions showed a pronounced self-serving bias, particularly following success. The finding is interpreted as self-regulation of affective state. Specifically, causal attribution of success to internal factors can sustain or enhance positive affect; attribution of failure to external factors can diminish negative affect. Ancillary analyses corroborated this interpretation. 相似文献
86.
Previous research on the effect of lecture handouts on student learning indicates that students who are given skeletal handouts usually perform better in course examinations than students who take all their own notes. The present study investigates whether the amount of detail in the handout is a critical factor in this. A randomized groups experiment was conducted in the context of a course on dental surgery. Four lecture handout conditions (headings and full text; headings and key points; headings only; no supplementary materials) were compared on tests 2 days and 2 weeks after the lecture. The significant differences between conditions were: ‘headings only’ better than ‘headings and key points’ on the first test; ‘headings only’ better than ‘no supplementary materials’ on the second test; and ‘headings and full text’ better than ‘no supplementary materials’ on the second test. These results indicate that the amount of detail is a critical factor in handout effectiveness. 相似文献
87.
88.
89.
LAWRENCE H. GERSTEIN GREGORY A. BAYER 《Journal of counseling and development : JCD》1988,66(6):294-297
Braun, A.L., & Novak, D.E. (1986, November/December). A study of EAP non-utilization. EAP Digest, pp. 52–55. O'Connell, V. (1987, March/April). A strategy for overcoming supervisors' resistance. EAP Digest, pp. 63–66. Penzer, W.N. (1987, March/April). Toward sustaining quality mental health services. EAP Digest, pp. 35–40. 相似文献
90.