全文获取类型
收费全文 | 10509篇 |
免费 | 432篇 |
国内免费 | 1篇 |
专业分类
10942篇 |
出版年
2021年 | 68篇 |
2020年 | 148篇 |
2019年 | 198篇 |
2018年 | 233篇 |
2017年 | 255篇 |
2016年 | 310篇 |
2015年 | 219篇 |
2014年 | 273篇 |
2013年 | 1139篇 |
2012年 | 422篇 |
2011年 | 437篇 |
2010年 | 309篇 |
2009年 | 297篇 |
2008年 | 455篇 |
2007年 | 417篇 |
2006年 | 382篇 |
2005年 | 349篇 |
2004年 | 357篇 |
2003年 | 347篇 |
2002年 | 366篇 |
2001年 | 124篇 |
2000年 | 139篇 |
1999年 | 155篇 |
1998年 | 164篇 |
1997年 | 142篇 |
1996年 | 132篇 |
1995年 | 148篇 |
1994年 | 121篇 |
1993年 | 119篇 |
1992年 | 115篇 |
1991年 | 107篇 |
1990年 | 101篇 |
1989年 | 90篇 |
1988年 | 72篇 |
1987年 | 71篇 |
1986年 | 75篇 |
1985年 | 93篇 |
1984年 | 120篇 |
1983年 | 131篇 |
1982年 | 121篇 |
1981年 | 149篇 |
1980年 | 116篇 |
1979年 | 126篇 |
1978年 | 131篇 |
1977年 | 122篇 |
1976年 | 112篇 |
1975年 | 109篇 |
1974年 | 109篇 |
1973年 | 71篇 |
1972年 | 66篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
While many studies have attempted to produce hypertension through the use of various environmental Stressors, few have succeeded in producing chronic elevations in blood pressure beyond levels considered to be borderline hypertensive (140–160 mm Hg systolic). The problem with most studies stems from the use of genetically normotensive animals and the selection of Stressors to which animals readily adapt. A new approach is suggested, which recognizes the role of genetics in human essential hypertension. Animals with one hypertensive parent do not develop spontaneous hypertension but show a more sensitive cardiovascular response to environmental Stressors than animals with normotensive parents. Preliminary studies revealed that animals with a mixed genetic history of hypertension develop spontaneous borderline hypertension. When subjected to shock-shock conflict, these borderline hypertensive rats (BHR) developed permanent hypertension that failed to abate even after a ten-week, shock-free recovery period. The hypertension was accompanied by elevated heart weight to body weight ratios and by significant cardiac pathology. Subsequent work has demonstrated that these animals also become hypertensive when fed a high-sodium diet. Finally, in a series of exercise studies, we found that BHRs subjected to a shock stressor were protected against stress-induced hypertension if they exercised daily. The potential of this model for studies of the mechanisms by which environmental variables produce permanent hypertension is discussed. 相似文献
52.
E. James Kehoe Constantine X. Poulos I. Gormezano 《Integrative psychological & behavioral science》1985,20(1):29-38
Two experiments examined appetitive differential conditioning of the rabbit’s jaw movement response (JMR) in a two-phase procedure. The first phase entailed reinforced training with one conditioned stimulus (CS+), and the second phase involved intermixed presentations of CS+ and an unreinforced stimulus (CS?). In Experiment 1, CS+ was a 600-Hz tone, and CS-was either a 660-,1,000-, or 2,100-Hz tone. In Experiment 2, the magnitude of the water unconditioned stimulus (US) paired with CS+ was either 1, 3, or 9 ml. The experiments revealed that 1) the level of responding to CS-rose for several days and then declined over the remainder of training; 2) the physical similarity between CS+ and CS?directly affected the level of responding to CS?but had no discernable effect on the level of responding to CS+ ; and 3) US magnitude positively affected the level of responding to CS + and, to a lesser extent, CS?. The results are discussed in terms of their implications for Spence’s gradient interaction theory and Pavlov’s external inhibition hypothesis. 相似文献
53.
54.
55.
C. M. Mitchell William S. Davidson II Robin Redner Craig Blakely James G. Emshoff 《American journal of community psychology》1985,13(2):203-220
This study examined two issues related to the use of nonprofessional counselors (n = 159) within the context of a diversion program for juvenile offenders. First, the relationship of the nonprofessionals' personality traits and general attitudes to client outcome was examined. No statistically significant correlations were observed. Second, the differential impact of various training and supervision factors was examined in terms of nonprofessional satisfaction, attitudes, and locus of control. Results suggested that training intensity, training content, and supervision setting may influence nonprofessionals' attitudes towards various social groups and their satisfaction with the nonprofessional experience. 相似文献
56.
Since both speech and color have perceptual ramifications in language, the present study was developed to study speech perception through color perception. With the recent advances in perception generally and color perception specifically, this nontraditional approach to studying speech perception appeared reasonable. The 12 consonants utilized in this study generated 144 pairs of nonsense CV-syllables. The consonant ensemble was selected because it accommodated a maximum number of phonological features with a minimum number of phonemes. The 46 subjects, who were in junior high school with an age range of 11 through 14 years, responded to each of the stimulus pairs by assigning (associating) to it one of the six primary colors. Because of the perceptual orderliness associated with subjects' judgments, the results indicated that color can be used to study speech perception. Specific findings included the retrieval of sameness, fronting (or place), and voicing.This study is based on a master's thesis presented to the Graduate School, Tennessee State University in Nashville. The authors gratefully acknowledge the cooperation and assistance of the Speech and Hearing Institute at the University of Texas Health Science Center-Houston. 相似文献
57.
Eric J. Oritt Stephen C. Paul Jay A. Behrman 《American journal of community psychology》1985,13(5):565-582
The development and psychometric investigation of the Perceived Support Network Inventory (PSNI), a measure of perceived social support, is described. A group of 146 introductory psychology students participated in a test-retest study design that collected reliability, internal consistency, and construct, convergent, and discriminant validity data on the scale. In addition, a contrast group of 28 Counseling Center clients was administered the PSNI. Test-retest reliability of the PSNI total score and subscale scores ranged from .72 to .88. Internal consistency for the PSNI was .77. Construct validity estimates ranged from .21 to .57. Convergent validity estimates varied from -.25 to .20. Discriminant validity estimates varied from -.11 to .19. Sample differences between introductory psychology student mean PSNI total and subscale scores and Counseling Center client mean PSNI total and subscale scores proved significant. Recommendations for subsequent research and future application are offered. 相似文献
58.
In the context of an annual fundraising drive for the American Society, two field experiments were conducted to test the relative effectiveness of suggesting either small or large contributions. In experiment 1, as part of a door-to-door campaign 300 people were randomly assigned to: (a) a standard request for contributions (control); (b) the standard request plus the words, “even a penny will help”; or (c) the standard request plus the words, “a generous contribution would really help.” As hypothesized, asking for a generous contribution significantly decreased the percentage of people who donated and failed to increase the average size of contribution by those who gave. Inconsistent with previous findings, the even-a-penny condition did not increase donating. In the second experiment conceptually similar requests were made in a mail-out campaign: 6,000 requests were made—2,000 suggested relatively small amounts (options beginning at $5); 2,000 suggested large amounts (options beginning at $5); and 2,000 were unspecified with regard to recommended amount (control). As expected, compared to the control condition, asking for small amounts increased the proportion of donors to nondonors without decreasing the average size of contributions, while asking for large amounts decreased the proportion of donors to nondonors without increasing the size of contributions. It is suggested that the findings have important implications for charitable fundraising. 相似文献
59.
60.