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   89622篇
  免费   1720篇
  国内免费   7篇
  91349篇
  2020年   985篇
  2019年   1152篇
  2018年   1585篇
  2017年   1620篇
  2016年   1728篇
  2015年   1278篇
  2014年   1509篇
  2013年   7008篇
  2012年   2818篇
  2011年   2812篇
  2010年   1746篇
  2009年   1711篇
  2008年   2445篇
  2007年   2405篇
  2006年   2153篇
  2005年   1885篇
  2004年   1889篇
  2003年   1784篇
  2002年   1751篇
  2001年   2804篇
  2000年   2646篇
  1999年   1996篇
  1998年   944篇
  1997年   826篇
  1996年   878篇
  1993年   809篇
  1992年   1742篇
  1991年   1632篇
  1990年   1630篇
  1989年   1516篇
  1988年   1478篇
  1987年   1372篇
  1986年   1421篇
  1985年   1537篇
  1984年   1199篇
  1983年   1098篇
  1979年   1303篇
  1978年   904篇
  1977年   809篇
  1976年   814篇
  1975年   1080篇
  1974年   1240篇
  1973年   1285篇
  1972年   1122篇
  1971年   1035篇
  1970年   963篇
  1969年   956篇
  1968年   1244篇
  1967年   1107篇
  1966年   1011篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
221.
The purpose of this research was to examine the relationship between parents' perceptions of marital satisfaction and family stress and their third grade children's classroom behavior. Twenty-one married couples completed questionnaires during home visits. Behavior observations were made from videotapes of children recorded in their classroom during lunch and group academic periods on each of three days. Frequencies of peer interactions, solitary behaviors, and teacher interactions were coded. Regression analyses showed that mothers' level of marital satisfaction (but not fathers') predicted their children's frequency of peer interactions during lunch. Fathers' level of perceived family stress (but not mothers') predicted their children's frequency of peer interactions during lunch. Neither measure for either parent was related to the frequency of peer interactions, solitary behaviors, or teacher interactions observed during the academic sessions. These findings highlight the importance of assessing the potential differential relation of parent variables to children's trans-situational behaviors, and the examination of these variables in relation to different social-environmental contexts in which children participate outside the home.  相似文献   
222.
...Instead of and certainly before advising the school or S.A. to go into court, I would urge them to try to resolve the question where it arises -- in the classroom, not the courtroom. And I would ask school officials to try to place themselves in S.A.'s shoes, and to imagine how she feels about her situation; and to ask themselves how they will feel if they administer CPR against her and her parents' wishes. Is there no way that they can do more than nothing, but less than CPR? Which image would we prefer to attach to S.A.'s case, that of some lawyers giving a press conference on the courthouse steps or of a story about a school that made it possible for one of its students to spend her precious time with her friends, classmates, and teachers, as they learn together that death does not need to separate the living from the dying?  相似文献   
223.
The authors explored the relationship between family support and adjustment for adult men in a detention center, as measured by a staff rating scale completed by the appropriate counselor.  相似文献   
224.
We examined two systems of assessing family interactions that are in common usage: a home based observation of free parent-child interaction and a clinic based observation of a structured mother-child problem solving discussion. Participants were 18 depressed, 27 conduct disordered and 16 comparison children and their mothers. Results indicated that: 1) these observations may yield very different data about child, and to a lesser extent, parent behavior, 2) parental affect in the clinic was related to their level of aversive behaviour in the home, 3) levels of both aversive and positive behavior for children and their mothers were correlated within each setting, 4) accuracy of diagnostic classifications made on the basis of the observational data were highest for comparison and conduct disordered children, but lowest for depressed children observed in the clinic, and 5) the inclusion of data on mothers' behavior increased classification accuracy for conduct disordered children only.  相似文献   
225.
A tether system has been developed for continuous monitoring of blood pressure in the micropig. The micropig is a suitable model for blood-pressure research because of the similarity of its cardiovascular system to that of humans and because of its sensitivity to high sodium intake. The system consists of a metal boom, attached via a universal joint to a wall 6 ft above floor level, that extends horizontally to the center of the enclosure. A fluid and electronic swivel affixed to the boom is connected to a flexible, hollow, metal tether that descends to a vest worn by the micropig. The vest contains a pressure transducer to which an indwelling arterial catheter is connected via a stopcock. The transducer cable and an infusion line ascend through the interior of the tether to the swivel. The system remains in equilibrium through a system of pulleys and counterweights. Continuous, 24-h recording shows a diurnal variation characterized by higher heart rate but lower blood pressure during the day than at night. The system has been found to be effective for continuous studies over intervals of a month or more.  相似文献   
226.
Two experiments are described that measured lexical decision latencies and errors to five-letter French words with a single higher frequency orthographic neighbor and control words with no higher frequency neighbors. The higher frequency neighbor differed from the stimulus word by either the second letter (e.g.,astre-autre) or the fourth letter (chope-chose). Neighborhood frequency effects were found to interact with this factor, and significant interference was observed only tochope-type words. The effects of neighborhood frequency were also found to interact with the position of initial fixation in the stimulus word (either the second letter or the fourth letter). Interference was greatly reduced when the initial fixation was on the critical disambiguating letter (i.e., the letterp inchope). Moreover, word recognition was improved when subjects initially fixated the second letter relative to when they initially fixated the fourth letter of a five-letter word, but this second-letter advantage practically disappeared when the stimulus differed from a more frequent word by its fourth letter. The results are interpreted in terms of the interaction between visual and lexical factors in visual word recognition.  相似文献   
227.
Outside of the laboratory, listening conditions are often less than ideal, and when attending to sounds from a particular source, portions are often obliterated by extraneous noises. However, listeners possess rather elegant reconstructive mechanisms. Restoration can be complete, so that missing segments are indistinguishable from those actually present and the listener is unaware that the signal is fragmented. This phenomenon, called temporal induction (TI), has been studied extensively with nonverbal signals and to a lesser extent with speech. Earlier studies have demonstrated that TI can produce illusory continuity spanning gaps of a few hundred milliseconds when portions of a signal are replaced by a louder sound capable of masking the signal were it actually present. The present study employed various types of speech signals with periodic gaps and measured the effects upon intelligibility produced by filling these gaps with noises. Enhancement of intelligibility through multiple phonemic restoration occurred when the acoustic requirements for TI were met and when sufficient contextual information was available in the remaining speech fragments. It appears that phonemic restoration is a specialized form of TI that uses linguistic skills for the reconstruction of obliterated speech.  相似文献   
228.
Working in the fragment of Martin-Löfs extensional type theory [12] which has products (but not sums) of dependent types, we consider two additional assumptions: firstly, that there are (strong) equality types; and secondly, that there is a type which is universal in the sense that terms of that type name all types, up to isomorphism. For such a type theory, we give a version of Russell's paradox showing that each type possesses a closed term and (hence) that all terms of each type are provably equal. We consider the kind of category theoretic structure which corresponds to this kind of type theory and obtain a categorical version of the paradox. A special case of this result is the degeneracy of a locally cartesian closed category with a morphism which is generic in the sense that every other morphism in the category can be obtained from it via pullback.The financial support of the Royal Society in London is gratefully acknowledged.  相似文献   
229.
We tested the validity of the egotism model of human helplessness. In contrast to the original theoretical approach of Seligman and his associates, which points to response-outcome noncontingency as the main source of helplessness, the egotism alternative proposes that repeated failure itself is the critical determinant of helplessness symptoms. Repeated failure threatens the self-esteem of the subject, who supposedly engages in a least-effort strategy during the test phase of a typical learned helplessness study, which results in performance impairment. To examine the egotism explanation, we gave subjects noncontingent-feedback training with or without repeated failure on five consecutive discrimination problems. In two experiments, noncontingent-feedback preexposure produced helplessness deficits in performance on avoidance learning, whereas repeated failure appeared irrelevant to helplessness. This and our other findings from research are inconsistent with the egotism explanation and support instead Seligman's original proposal, in which helplessness is attributed to prolonged experience with noncontingency.  相似文献   
230.
Freyd, Pantzer, and Cheng (1988) provided considerable evidence for the proposition that people can represent underlying forces within static scenes. However, they explicitly assumed that their observed memory shifts were the result of perceptually modular information processing. For several reasons, I suggest herein that this assumption of cognitive impenetrability is a dubious one. The assumption is challenged by recent empirical findings, some theoretical considerations, and calculations that show that the observed effects are minute when compared with those expected by means of physical forces. Three explanations for the evidence are proposed, including the alternative hypothesis that although people do represent static physical forces, these representations can be almost completely overridden by the conscious intention to remember an object's precise location.  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