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   53752篇
  免费   2063篇
  国内免费   34篇
  2020年   544篇
  2019年   635篇
  2018年   845篇
  2017年   865篇
  2016年   985篇
  2015年   690篇
  2014年   813篇
  2013年   4054篇
  2012年   1541篇
  2011年   1570篇
  2010年   948篇
  2009年   1021篇
  2008年   1378篇
  2007年   1330篇
  2006年   1193篇
  2005年   1074篇
  2004年   1031篇
  2003年   982篇
  2002年   1027篇
  2001年   1611篇
  2000年   1597篇
  1999年   1165篇
  1998年   543篇
  1997年   508篇
  1992年   1027篇
  1991年   979篇
  1990年   955篇
  1989年   935篇
  1988年   891篇
  1987年   846篇
  1986年   879篇
  1985年   957篇
  1984年   792篇
  1983年   731篇
  1982年   546篇
  1981年   548篇
  1979年   855篇
  1978年   618篇
  1977年   560篇
  1976年   566篇
  1975年   729篇
  1974年   848篇
  1973年   896篇
  1972年   759篇
  1971年   713篇
  1970年   650篇
  1969年   695篇
  1968年   849篇
  1967年   782篇
  1966年   746篇
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
991.
When presented with a behavioral problem or symptom expression that involves two systems, such as a serious school-related problem, the therapist needs to design an approach that will intervene effectively and expeditiously in both systems. This paper offers a guide to stages of problem escalation and therapeutic intervention that is intended to aid the problem-solver's thinking processes in approaching a troubled situation that involves two systems, the school and the home.  相似文献   
992.
There has been interest in recent years in the relationship between marital distress and psychopathology. It has been rare, however, for investigators to follow patients after their release from the hospital and observe the course of their marital relationships. The present study included patients meeting criteria for three DSM III DISORDERS (MAjor depressive, bipolar, and schizophrenic) and a normal control sample, all of whom are participants in an ongoing longitudinal study of children at risk for psychopathology (Stony Brook High-Risk Project; Weintraub & Neale, 1984). Marital Adjustment Test (MAT; Locke & Wallace, 1959) scores were collected on patients at entry into the project (Phase I) and at a three year follow-up (Phase II). Course of marriage was defined as negative if the couple's marital adjustment was rated as poor at Phase II or resulted in divorce or separation at Phase II. It was found that only the depressed group differed from the normal group in having significantly worse course of marital relationship; 84% of the depressive couples showed a “negative” course of marital change over time. However, all three patient groups had significantly higher rates of divorce by Phase II. MAT scores at Phase I successfully predicted course of marital relationship for all diagnostic groups. Implications for aftercare of psychiatric inpatients are discussed.  相似文献   
993.
The problem of ethics in medical care as seen from the bioengineering results from the almost incredible technological achievements based on scientific research: On the one hand there is inadequate handling of technology and fear on the part of the patient; on the other hand there is admiration on the part of the physicians and the nursing staff. This article will survey the points of criticism concerning ethical behavior and will present and evaluate general problems of mechanization in medical care. General phenomena of human interaction, and especially problems related to medical care, will be discussed. It will be necessary to develop clinical medical technology, aiming primarily at ‘realizing the patient's concern’. After analyzing these concerns, it is necessary for the clinical medical engineer to develop an ‘invisible’ technology. Criteria for such an ‘invisible’ technology (function, design, automatic control, methods of implantation, whether chronic application is necessary) are being demonstrated by particular devices (artifical heart, functional electro-stimulation, diaphragmatic pace-maker).  相似文献   
994.
Two experiments showed the influence of perceptual set on the perception of subjective contours. In the first, the perceived shape of a subjective-contour figure (a minimal version of the Ehrenstein configuration) was varied by altering the observer’s viewing set. The second experiment showed that apparent depth emerged in subjective-contour figures when observers were set to perceive the illusory contours.  相似文献   
995.
Alternate monocular and binocular exposure to complementary stimulation can yield opposite but coexisting aftereffects that are contingent on whether the test display is viewed with one eye or two eyes. The motion aftereffect was studied by adapting each eye separately to a contracting spiral and both eyes together to an expanding spiral. The stationary test spiral subsequently appeared to be expanding when viewed monocularly, but to be contracting when it was seen with both eyes open. With respect to the McCollough effect, after monocular exposure to red-vertical and green-horizontal gratings and binocular exposure to red-horizontal and green-vertical gratings, the appearance of the color of the test gratings when viewed with one eye was different from that when viewed with both eyes. Opposite, coexisting aftereffects induced by complementary stimulation can be interpreted as evidence that there are unique binocular aspects to visual function.  相似文献   
996.
It is well established that human observers respond more quickly to visual targets that appear in expected locations than they do to ones in unexpected locations. These variations in simple reaction time have been attributed to a covert alignment of an attentional mechanism to the expected target location. The present experiments investigated the influence of strength of signal and strength of subject’s positional expectancy on the magnitude of this attentional effect. In the first experiment, target luminance was varied over a range of three log units, and it was found that the effects of luminance were essentially additive with the effect of the positional expectancy (i.e., the attention effect). The second experiment found that the magnitude of visual attention interacts with the information value of the precue used to create the spatial expectancy, although, once again, luminance had additive effects. The resuls are interpreted as indicating that, rather than influencing early visual processing, the act of attending to a spatial location operates fairly late in the detection process.  相似文献   
997.
This study investigates the separate activation versus coactivation issue for redundant targets in a simple letter-detection paradigm with latency as the dependent variable. The results of a one-response visual-search task are reported. Since, on single-target trials, only the target was presented and no accompanying noise element, no “distraction decrement” caused by irrelevant noise elements (Grice et al., 1984) was to be expected. The data obtained showed a clear redundantsignal effect. Subsequent detailed analysis of the latency data using Miller’s (1982) procedure indicated that the results were consistent with a separate activation model and failed to provide convincing evidence in favor of coactivation models. A further analysis of the data indicated that, in the present study, the separate channels were negatively correlated for a range of fast RTs and positively correlated for intermediate and larger RTs. No evidence in favor of Grice et al.’s (1984) distraction-decrement hypothesis was found. The conclusions of this study are that (1) a separate activation model summarizes the essential features of information processing in this simple visual search task, and (2) no convincing evidence in favor of coactivation in visual search tasks has been reported in the literature up to now.  相似文献   
998.
Six tasks administered on a MINC-11 minicomputer were used in studying the effects of long, continuous work periods and fatigue on physical and cognitive task performance. Submaximal physiological workload measurement was done during one of these tasks for a subject walking on a treadmill. The MINC-11 system is described, as are the six tasks programs. Four of these tasks measured various types of reaction times, another involved complex information processing, and one appraised moods, physical symptoms, fatigue, and the physiological status of subjects.  相似文献   
999.
The recent Supreme Court decision upholding Roe v. Wade and in particular, the dissent by Justice Sandra Day O'Connor, sheds new light on the issue of abortion. Let us consider any stage of a pregnancy when abortion is medically safe for the mother. If at that stage it is also medically viable to save the fetus, is an abortion performed at that stage of pregnancy morally justifiable? For example, if it is, or becomes, medically safe to perform abortions after first trimester of pregnancy and at the same time saving a fetus is, or becomes, medically viable or not unusual during some stage of the second trimester, can abortions during and after that stage of pregnancy be justified? With a number of qualifications I shall argue the thesis that as a general rule, but not an absolute rule, abortion in these instances is not usually justifiable. For if it is, then one will also have to grant the moral justification for a number of other highly questionable medical practices. This thesis is not to be identified with the stronger claim that abortions of viable fetuses can never be performed. There are surely exceptions such as when the life or health of the mother is in danger. But, I shall argue, the justification for making such exceptions is on different grounds than is sometimes claimed because one must weigh the health of the mother against the life of another human being.  相似文献   
1000.
Prior surgical implantation of a venous catheter sensitized rats to coldimmobilization stress. Three of six catheterized females succumbed during the stress. The remaining rats fell into two groups in terms of their core temperature at the end of the stress period: Male uncatheterized rats had higher temperatures than rats in the other three groups. No relation was found between catheter patency and magnitude of hypothermia. Degree of gastric disease paralleled the core temperature findings in that the male uncatheterized rats had significantly fewer gastric erosions than the rats in the other three groups. Additionally, a robust effect of gender was found with uncatheterized females showing more hypothermia and more gastric disease than uncatheterized males. A subsequent experiment was conducted to evaluate whether anesthesia or wearing the protective spring was responsible in part for the sensitization seen. Here, the gender difference was less although females consistently averaged lower core temperatures after stress than did males. Despite similar core temperatures after stress, females that were prepared with the protective spring apparatus developed more gastric disease than female controls or similarly treated males. Thus, the additional sensitization exhibited by females in the first experiment may relate to the fact that both catheterization and the taping procedure were sensitizers while only catheterization was a sensitizer for males.  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