首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   6293篇
  免费   317篇
  国内免费   4篇
  2024年   11篇
  2023年   67篇
  2022年   101篇
  2021年   122篇
  2020年   171篇
  2019年   173篇
  2018年   338篇
  2017年   326篇
  2016年   284篇
  2015年   170篇
  2014年   193篇
  2013年   817篇
  2012年   447篇
  2011年   453篇
  2010年   296篇
  2009年   194篇
  2008年   363篇
  2007年   310篇
  2006年   265篇
  2005年   250篇
  2004年   153篇
  2003年   156篇
  2002年   145篇
  2001年   71篇
  2000年   86篇
  1999年   62篇
  1998年   32篇
  1997年   29篇
  1996年   29篇
  1995年   21篇
  1994年   22篇
  1993年   19篇
  1992年   37篇
  1991年   25篇
  1990年   27篇
  1989年   29篇
  1988年   27篇
  1987年   20篇
  1986年   11篇
  1985年   18篇
  1984年   17篇
  1983年   14篇
  1981年   12篇
  1979年   15篇
  1978年   11篇
  1976年   16篇
  1974年   15篇
  1972年   11篇
  1968年   12篇
  1965年   10篇
排序方式: 共有6614条查询结果,搜索用时 15 毫秒
241.
242.
With each proposition P we associate a set of proposition (a hyperproposition) which determines the order in which one may retreat from accepting P, if one cannot fully hold on to P. We first describe the structure of hyperpropositions. Then we describe two operations on propositions, subtraction and merge, which can be modelled in terms of hyperpropositions. Subtraction is an operation that takes away part of the content of a proposition. Merge is an operation that determines the maximal consistent content of two propositions considered jointly. The merge operation gives rise to an inference relation which is, in a certain sense, optimally paraconsistent.  相似文献   
243.
The purpose of this study was to determine whether an association exists between neuropsychological deficits and conduct disorder (CD) with and without concurrent attention-deficit–hyperactivity disorder (ADHD). In addition, we explored the differential neuropsychological performance of aggressive and nonaggressive CD adolescents and the combined effect of this behavioral status and ADHD on performance. Fifty-nine adolescents (mean age of 15.4 years) who met the criteria for CD were compared with 29 controls comparable in age, gender, and socioeconomic status. A neuropsychological battery of current tests measuring executive functions and a battery of language tests were used in the study. Multivariate analyses showed that, compared with controls, CD adolescents had significantly lower verbal skills but did not differ on executive function measures. However, the lower verbal performance of CD adolescents is not explained by the existence of a CD subgroup with concomitant ADHD or aggressiveness. The study confirms with a sample of CD adolescents the association between verbal deficits and antisocial behavior when socioeconomic status is controlled. Our results also demonstrate that CD per se can be a sufficient condition for such deficits.  相似文献   
244.
245.
The acetylcholinesterase reversible inhibitorN-octyl-1,2,3,4-tetrahydro-9-aminoacridine (THA-C8) is a new synthesized derivative of tacrine (THA) characterized by an alkyl chain in the molecular structure which ameliorates the penetrability of the compound into the central nervous system. THA-C8 (0.1–5 mg/kg) significantly reduced spontaneous locomotor activity in CD1 mice at a dose of 3 mg/kg. Moreover, THA-C8 (0.2–2 mg/kg) significantly improved shuttle-box avoidance acquisition at doses (0.25, 0.3, 1 mg/kg) not affecting locomotion and that are much lower than the doses reported to be effective for THA in animal models. From the data reported it seems that the new compound could be interesting for therapeutic purposes.  相似文献   
246.
247.
Ratings of familiarity and pronounceability were obtained from a random sample of 199 surnames (selected from over 80,000 entries in the Purdue University phone book) and 199 nouns (from the Ku?era-Francis, 1967, word database). The distributions of ratings for nouns versus names are substantially different: Nouns were rated as more familiar and easier to pronounce than surnames. Frequency and familiarity were more closely related in the proper name pool than the word pool, although both correlations were modest. Ratings of familiarity and pronounceability were highly related for both groups. A production experiment showed that rated pronounceability was highly related to the time taken to produce a name. These data confirm the common belief that there are differences in the statistical and distributional properties of words as compared to proper names. The value of using frequency and the ratings of familiarity and pronounceability for predicting variations in actual pronunciations of words and names are discussed.  相似文献   
248.
Laraudogoitia  Jon Pérez 《Synthese》1999,119(3):313-323
In Pérez Laraudogoitia (1996), I introduced a simple example of a supertask that involved the possibility of spontaneous self-excitation and, therefore, of a particularly interesting form of indeterminism in classical dynamics. Alper and Bridger (1998) criticised (among other things) this result. In the present article, I answer their criticisms. In what follows I assume familiarity both with Pérez Laraudogoitia (1996) and Alper and Bridger’s subsequent article. This revised version was published online in June 2006 with corrections to the Cover Date.  相似文献   
249.
Demri  Stéphane  Orłowska  Ewa 《Studia Logica》1999,62(2):177-200
In this paper a unified framework for dealing with a broad family of propositional multimodal logics is developed. The key tools for presentation of the logics are the notions of closure relation operation and monotonous relation operation. The two classes of logics: FiRe-logics (finitely reducible logics) and LaFiRe-logics (FiRe-logics with local agreement of accessibility relations) are introduced within the proposed framework. Further classes of logics can be handled indirectly by means of suitable translations. It is shown that the logics from these classes have the finite model property with respect to the class of -formulae, i.e. each -formula has a -model iff it has a finite -model. Roughly speaking, a -formula is logically equivalent to a formula in negative normal form without occurrences of modal operators with necessity force. In the proof we introduce a substantial modification of Claudio Cerrato's filtration technique that has been originally designed for graded modal logics. The main core of the proof consists in building adequate restrictions of models while preserving the semantics of the operators used to build terms indexing the modal operators.  相似文献   
250.
Many studies have shown the importance of personality traits as factors related to alcohol use and misuse. The relationship between personality traits and alcohol consumption was studied in a sample of 149 non-alcoholic women using the Karolinska Scales of Personality (KSP) and the Eysenck Personality Questionnaire-Revised (EPQ-R). The results showed positive correlations between alcohol consumption and disinhibitory personality traits (sensation seeking, impulsivity, psychopathy, nonconformity) and dimensions (psychoticism and extraversion). Sensation seeking combined with impulsivity were the strongest predictors of alcohol consumption. Anxiety-related traits and neuroticism were not related to alcohol frequency/amount of alcohol use.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号