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   31190篇
  免费   1440篇
  国内免费   21篇
  2020年   389篇
  2019年   401篇
  2018年   608篇
  2017年   579篇
  2016年   623篇
  2015年   475篇
  2014年   557篇
  2013年   2344篇
  2012年   1019篇
  2011年   1049篇
  2010年   654篇
  2009年   611篇
  2008年   842篇
  2007年   842篇
  2006年   731篇
  2005年   678篇
  2004年   634篇
  2003年   583篇
  2002年   612篇
  2001年   1274篇
  2000年   1264篇
  1999年   870篇
  1998年   338篇
  1997年   326篇
  1996年   293篇
  1995年   263篇
  1992年   693篇
  1991年   630篇
  1990年   666篇
  1989年   601篇
  1988年   581篇
  1987年   543篇
  1986年   549篇
  1985年   529篇
  1984年   454篇
  1983年   389篇
  1982年   273篇
  1979年   396篇
  1978年   328篇
  1977年   272篇
  1975年   362篇
  1974年   448篇
  1973年   414篇
  1972年   372篇
  1971年   333篇
  1970年   295篇
  1969年   358篇
  1968年   401篇
  1967年   340篇
  1966年   329篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
911.
In this article the perspective shifts to the “upstream” end of the agricultural knowledge and information system (AKIS). Because knowledge policy and strategic decision-making are not the prerogative of the public sector, organizations such as cooperative unions and multinational companies are included. After considering the influence of the changing environment on the nature of the AKIS, the role of knowledge management and policy in the emerging knowledge and information market is examined. Special attention is given to public and private R&D. The article then looks where information technology (IT) fits in and what considerations determine strategic investment in IT projects and sustained services. Some of the European experiences with this strategic investment are evaluated.  相似文献   
912.
The Revised UCLA Loneliness Scale (R-UCLA) is described and used as a unidimensional measure of loneliness; conceptualizing and assessing loneliness as a unitary, global experience. The present study suggests that the R-UCLA is a multidimensional measure of loneliness that assesses more than one construct of the loneliness experience. Results of principal axis factor analysis suggest that the R-UCLA measures three dimensions of loneliness: loneliness related to (a) “intimate others,” (b) “social others,” and (c) the “affiliative environment.” These findings may affect the utilization of the R-UCLA in future assessment, research, and intervention. These implications are discussed. This article is based on the author’s master’s thesis, submitted for the Master of Counseling degree at Arizona State University.  相似文献   
913.
914.
In matters of discontinuation of life-sustaining treatment, traditional role of the family to speak on behalf of the incompetent patient is questionable. We explore the reasons why physicians perceive patient autonomy to be transferrable to family members. Principle of patient autonomy may not suffice when futile treatment is demanded and may serve to erode the ethical integrity of medical profession. An enhanced role for bioethics committees is proposed when physicians propose to discontinue life-sustaining treatment against the wishes of the patient or their families.  相似文献   
915.
916.
In this paper, we describe software that turns a Macintosh computer into an off-the-shelf tool for experiments on visual search. Our design goals included portability (between members of the Macintosh computer family and between various research settings), user-friendliness (equivalent to Macintosh programming standards), flexibility (to allow replication and extension of important experiments on visual search), and adaptability (very short design-to-data and data-to-analysis turnaround times). We describe how the software meets these goals in three major phases of an experiment: stimulus construction, experimental control, and statistical analysis. We then list several landmark studies of visual search that can be easily designed and extended with the software. Finally, we outline plans for expanding the experimental variations that will be supported in future versions of the software.  相似文献   
917.
Phonetic segments are coarticulated in speech. Accordingly, the articulatory and acoustic properties of the speech signal during the time frame traditionally identified with a given phoneme are highly context-sensitive. For example, due to carryover coarticulation, the front tongue-tip position for HI results in more fronted tongue-body contact for a /g/ preceded by /l/ than for a /g/ preceded by /r/. Perception by mature listeners shows a complementary sensitivity—when a synthetic /da/-/ga/ continuum is preceded by either /al/ or /ar/, adults hear more /g/s following HI rather than Irl. That is, some of the fronting information in the temporal domain of the stop is perceptually attributed to /l/ (Mann, 1980). We replicated this finding and extended it to a signaldetection test of discrimination with adults, using triads of disyllables. Three equidistant items from a /da/-/ga/ continuum were used preceded by /al/ and /ar/. In the identification test, adults had identified item ga5 as “ga”, and dal as “da”, following both /al/ and /ar/, whereas they identified the crucial item d/ga3 predominantly as “ga” after /al/ but as “da” after /ar/. In the discrimination test, they discriminated d/ga3 from dal preceded by /al/ but not /ar/; compatibly, they discriminated d/ga3 readily from ga5 preceded by /ar/ but poorly preceded by /al/. We obtained similar results with 4-month-old infants. Following habituation to either ald/ga3 or ard/ga3, infants heard either the corresponding ga5 or dal disyllable. As predicted, the infants discrimi-nated d/ga3 from dal following /al/ but not /ar/; conversely, they discriminated d/ga3 from ga5 following /ar/ but not /al/. The results suggest that prelinguistic infants disentangle consonant-consonant coarticulatory influences in speech in an adult-like fashion.  相似文献   
918.
IN PREVIOUS WORKS the author has proposed the conception of an affect-behavioral system as the neuropsychological basis of fundamental emotions and drives. It consists of ten subsystems (SS) integrated with relations of reciprocal induction and facilitation. The SSs are: (1) SS of flight, (2) SS of aggression, (3) SS of socially channeled attack, (4) SS of mutual aid, (5) SS of autoaggression, (6) SS of food taking, (7) SS of inhibition of food taking, (8) SS of vomiting, (9) SS of sexual contacts, and (10) SS of inhibition of sexual contacts. To the activity of the different SSs correspond fundamental emotions and drives. Thus, to the activity of the SS of flight corresponds fear; to the activity of the SS of aggression, socially uncultivated anger; to the activity of the SS of sexual contacts, sexual drive; and so forth. In the paper, appropriate observations are analyzed. They reveal that the activity of the SSs of flight and vomiting can inhibit reciprocally the sexual drive; whereas, the activity of the SSs of socially channeled attack, of mutual help, and of aggression can facilitate it. The activity of the SS of autoaggression is two-sided: According to the personality structure and the situation, it can inhibit or facilitate the sexual drive.  相似文献   
919.
Considerable evidence has accumulated in support of the hypothesis that subclinical depression may inhibit role performance in important ways. However, interpersonal stress and marital discord often precede the development of depressive symptomatology and may independently predict deficits in family role functioning. In addition, cognitive theories suggest that persons with subclinical depression may report poor role functioning even in the absence of any real performance deficits. The current research examines the possibility (1) that the effect of depression on the fulfillment of important family roles is attributable to previously unmeasured contextual variables of ongoing interpersonal stress and/or relationship dissatisfaction or, alternatively, (2) that this relationship is the result of depressive distortion associated with self-report of symptoms and performance. Multiple regression analyses of interview data collected from 495 community-dwelling adults found, however, that depression is related to role functioning beyond any spurious effects attributable to interpersonal stress, spousal stress, or marital satisfaction. In addition, the effect of depression persists when collateral reports of role functioning utilized. Accordingly, it appears that subclinical depression is related to decrements in role performance, and this effect is not entirely due to contextual elements or shared method variance between self-report measures.The authors acknowledge research support from Research Grants R01-AA-07250 and R01-AA-07218 from the National Institute on Alcohol Abuse and Alcoholism, Research Grant R01-DA-07417 from the National Institute on Drug Abuse, and National Institutes of Mental Health Grant A-41487-07.  相似文献   
920.
Briefly stated my point is that the well-being of each person in a community conceived abstractly may be all too easily sacrificed for the sake of the abstraction. Physicians may offer critically ill patients places in programs of experimental treatment, but there is commonly a catch to the offer. To take part in a program of clinical experiment a patient must not only risk a possible failure of a fresh drug and the chance of destructive side effects from the drug, but the patients must risk only getting the traditional treatment along with a placebo rather than the experimental drug. Placebo control, double blind critical protocols for testing effects of fresh drugs on critically ill patients are a commonplace. I question the scientific objectivity of the protocols and the underlying ethic, and suggest use of alternate protocols. Experimental tests in the treatment gram-negative bacteria blood infections, muscular dystrophy, and AIDS and AIDS-related diseases are examples.  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