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   513篇
  免费   36篇
  2023年   13篇
  2022年   16篇
  2021年   19篇
  2020年   24篇
  2019年   26篇
  2018年   38篇
  2017年   31篇
  2016年   35篇
  2015年   16篇
  2014年   16篇
  2013年   44篇
  2012年   12篇
  2011年   19篇
  2010年   9篇
  2009年   6篇
  2008年   6篇
  2007年   11篇
  2006年   8篇
  2005年   4篇
  2004年   5篇
  2003年   4篇
  2002年   5篇
  2001年   6篇
  1999年   4篇
  1997年   6篇
  1995年   5篇
  1994年   5篇
  1990年   5篇
  1989年   4篇
  1987年   3篇
  1986年   6篇
  1984年   3篇
  1983年   6篇
  1982年   6篇
  1981年   5篇
  1977年   3篇
  1975年   4篇
  1974年   5篇
  1973年   8篇
  1972年   3篇
  1971年   8篇
  1969年   10篇
  1968年   6篇
  1967年   5篇
  1964年   4篇
  1961年   5篇
  1960年   4篇
  1958年   12篇
  1955年   6篇
  1953年   6篇
排序方式: 共有549条查询结果,搜索用时 31 毫秒
121.
Hostility online has not been evaluated by an empirical investigation. This study aims to evaluate (a) the difference between hostility in the real world and that online and (b) whether the difference is associated with Internet addiction, depression, or online activities. A total of 2,348 college students (1,124 males and 1,224 females) were recruited and completed the Chen Internet Addiction Scale, the Center for Epidemiological Studies' Depression Scale, and the questionnaire for online activity. Further, the Buss-Durkee Hostility Inventory-Chinese version-short form was utilized to evaluate hostility in both real and virtual worlds. The results demonstrated that the levels of all four dimensions of hostility were lower when getting online than those in the real world. Subjects with Internet addiction had higher hostility both in the real world and online as do subjects with depression. Further, college students with Internet addiction had increased expressive hostility behavior and those with depression had decreased hostility cognition, hostility affection, and suppressive hostility behavior when getting online. Lastly, the buffering effect of the Internet on hostility was attenuated among subjects paying the most online time in chatting, and those using the Internet mainly for online gaming had higher expressive hostility behavior not only in the real world but also online. These results suggest that attention should be paid to interventions concerning aggressive behavior among subjects with Internet addiction or online gaming and chatting. On the other hand, depressed college students would be less hostile after entering the Internet. It is suggested that the Internet would be one possible interactive media to provide intervention for depression.  相似文献   
122.
123.
Streszczenie Prototetyka St. Len'ewskiego jest uogólnieniem dwuwartociowego rachunku zda. Wystpuj w niej obok terminów tego rachunku funktory (zarówno stae jak i zmienne) tych wszystkich kategorii semantycznych, jakie mog by zdefiniowane, gdy punktem wyjcia jest kategor a zda.W pracy zreferowane s trzy systemy prototetyki. Terminem pierwotnym dwu z nich jest implikacja, terminem pierwotnym systemu trzeciego jest równowano. Systemy o terminie pierwotnym implikacji róni s. reguami wnioskowania. W jednym z nich obowizuje regua weryfikacji, w drugim regua ekstensjonalnoci. Pierwsza z tych regu jest uogólnieniem nastpujcej reguy rachunku zda, wzbogaconego o terminy 0 i 1:Wyraenie jest tez systemu, gdy tezami systemu s oba wyraenia powstae z przez podstawienie za pewn jego zmienn symboli 0 i 1.W myl reguy ekstensjonalnoci tezami systemu s prawa ekstensjonalnoci, sformuowane dla funktorów dowolnych kategorii semantycznych wac-wych prototetyce.W pracy podaj dowody równowanoci trzech systemów prototetyki i dowód ich zupenoci.Znaczna cz wyników Leniewskiego, zreferowanych w pracy, nie bya dotd opublikowana. Opracowujc te wyniki opieraem si na notatkach z wykadów Leniewskiego, spisanych przez jego uczniów. Oryginalne notatki Leniewskiego ulegy zniszczeniu w czasie powstania warszawskiego.  相似文献   
124.
125.
An increasing number of drugs removed from the market because of unacceptable toxicity raises concerns regarding preapproval testing of drug safety. In the present paper it is postulated that the non-inferiority type of trial should be abandoned in favor of the superiority trial with active controls and less stringent (p<0.1, both for efficacy and toxicity) statistics. This approach will increase sensitivity of detection of drug-induced adverse effects at the expense of increasing false positive results regarding the difference in efficacy between the tested and reference drug. Such a move will increase the protection of future patients. In addition, the proposed design is far more acceptable from the clinical (e.g. no need to specify the statistically expected “unimportant” number of deaths) and ethical points of view, as well as being favored by the strong incentive of involved parties. In the second part of this paper arguments are presented in favor of the hypothesis that placebo (still used in some superiority trials) does not induce adverse effects. The assertion that placebo may induce adverse effects is probably biased by the nature of the clinical experiment. Such a conclusion is supported by studies indicating that placebo-induced adverse effects are disease — and treatment — specific. The modification of clinical trials according to the proposed changes may increase the trials’ sensitivity at detecting adverse effects of drugs. A lecture on the subject of this paper was presented at the 6th International Bioethics Conference on the subject of ‘The Responsible Conduct of Basic and Clinical Research’, held in Warsaw, Poland, 3–4 June 2005.  相似文献   
126.
The Florida Department of Transportation used a series of changeable-message signs that functioned as freeway guide signs to divert traffic to Universal Theme Park via one of two eastbound exits based on traffic congestion at the first of the two exits. An examination of crashes along the entire route indicated a statistically significant increase in crashes at the first eastbound exit following the actuation of the system. Furthermore, all of the crashes occurred in close proximity to the exit gore (the crosshatched area at exits that drivers are not supposed to enter or traverse) at the first exit. In Experiment 1, behavioral data were collected using an alternating treatments design. These data revealed that reassigning the exit signs was effective in producing a change in the percentage of drivers using each of the two exits. These data also showed that the reassignment of the theme park exit was associated with an increase in the percentage of motor vehicle conflicts that consisted of vehicles cutting across the exit gore. An analysis revealed that the method used for switching the designated or active theme park exit on the series of changeable-message signs led to the presentation of conflicting messages to some motorists, thus resulting in erratic driving behavior (cutting across the exit gore). In Experiment 2, the treatment evaluated the use of a phased method of switching the designated theme park exit to eliminate the delivery of conflicting messages. The new method for switching the designated theme park exit was not associated with an increase in motorists cutting across the exit gore.  相似文献   
127.
The authors investigated whether compensatory postural coordination patterns are organized according to the same dynamical principles as are nonequilibrium phase transitions. Eight participants were asked to maintain upright balance on a moving platform that was sinusoidally translated in the anterior-posterior direction and was systematically increased and decreased 0.19 Hz as a step function every 10 platform cycles through the frequency range 0.19-1.46 Hz. At low platform frequencies, all participants exhibited small joint angular motions with high variability, and the relative phase between the joint motions exhibited drifting patterns and large fluctuations. As platform frequency increased, the amplitude of joint motion increased systematically and joint-specific oscillatory patterns emerged. The findings provided no evidence for a Hopf bifurcation or hysteresis in the transitions of postural coordination modes, however, or, more generally, a basis for distinguishing the relevance of linear versus nonlinear models of postural control.  相似文献   
128.
In this article I subject to criticism Field's argument, according to which field theory takes space‐time to be à substance since it ascribes field properties to space‐time points. There is petitio principii error made in this reasoning because Field does not give any justification for his controversial assumption that fields are properties of space‐time points. What is more, I suggest, Field's interpretation of field theory is incompatible with the way this theory is understood and utilized by its users, namely scientists. My criticism is based on the assumption that one cannot propose an ontology of a given scientific theory, at the same time imposing on it an interpretation which clashes with the interpretation current among its users. I also suggest that in order to establish the ontology of a scientific theory one should also take into account the way it has been constructed. According to this criterion, field theory does indeed take space‐time to be a substance.  相似文献   
129.
Summary The paper is a sketch of a conception of approximative truth (or verisimilitude). The concepts of relative error, and degree of inadequacy are introduced. By means of them the concept of truth-content of quantitative facts-statements, laws and theories is defined. Laws and theories accepted in science have a high truth-content, i.e. they are approximately true.  相似文献   
130.
First, we prove that the lattice of all structural strengthenings of a given strongly finite consequence operation is both atomic and coatomic, it has finitely many atoms and coatoms, each coatom is strongly finite but atoms are not of this kind — we settle this by constructing a suitable counterexample. Second, we deal with the notions of hereditary: algebraicness, strong finitisticity and finite approximability of a strongly finite consequence operation. Third, we formulate some conditions which tell us when the lattice of all structural strengthenings of a given strongly finite consequence operation is finite, and subsequently we give some applications of them.This paper was read at the Third Autumn School on Strongly Finite Sentential Calculi organized by the Section of Logic, Polish Academy of Sciences, Institute of Philosophy and Sociology, in Ustronie (Poland), November 1979.  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