全文获取类型
收费全文 | 2161篇 |
免费 | 250篇 |
国内免费 | 7篇 |
专业分类
耳鼻咽喉 | 17篇 |
儿科学 | 39篇 |
妇产科学 | 18篇 |
基础医学 | 268篇 |
口腔科学 | 46篇 |
临床医学 | 194篇 |
内科学 | 314篇 |
皮肤病学 | 45篇 |
神经病学 | 167篇 |
特种医学 | 68篇 |
外科学 | 292篇 |
综合类 | 59篇 |
预防医学 | 499篇 |
眼科学 | 95篇 |
药学 | 187篇 |
中国医学 | 18篇 |
肿瘤学 | 92篇 |
出版年
2022年 | 10篇 |
2021年 | 30篇 |
2020年 | 12篇 |
2019年 | 38篇 |
2018年 | 34篇 |
2017年 | 31篇 |
2016年 | 23篇 |
2015年 | 41篇 |
2014年 | 52篇 |
2013年 | 64篇 |
2012年 | 118篇 |
2011年 | 131篇 |
2010年 | 51篇 |
2009年 | 63篇 |
2008年 | 96篇 |
2007年 | 123篇 |
2006年 | 91篇 |
2005年 | 115篇 |
2004年 | 102篇 |
2003年 | 77篇 |
2002年 | 87篇 |
2001年 | 64篇 |
2000年 | 90篇 |
1999年 | 75篇 |
1998年 | 52篇 |
1997年 | 29篇 |
1996年 | 21篇 |
1995年 | 32篇 |
1994年 | 28篇 |
1993年 | 35篇 |
1992年 | 55篇 |
1991年 | 40篇 |
1990年 | 46篇 |
1989年 | 51篇 |
1988年 | 32篇 |
1987年 | 45篇 |
1986年 | 28篇 |
1985年 | 34篇 |
1984年 | 18篇 |
1983年 | 20篇 |
1982年 | 10篇 |
1981年 | 12篇 |
1980年 | 10篇 |
1979年 | 27篇 |
1978年 | 14篇 |
1974年 | 9篇 |
1973年 | 11篇 |
1972年 | 16篇 |
1971年 | 12篇 |
1969年 | 10篇 |
排序方式: 共有2418条查询结果,搜索用时 15 毫秒
91.
Changing mortality patterns in East and West Germany and Poland. II: short-term trends during transition and in the 1990s 总被引:1,自引:1,他引:0
OBJECTIVES: To examine trends in life expectancy at birth and age and cause specific patterns of mortality in the former German Democratic Republic (GDR) and Poland during political transition and throughout the 1990s in both parts of Germany and in Poland. METHODS: Decomposition of life expectancy by age and cause of death. Changes in life expectancy during transition by cause of death were examined using data for 1988/89 and 1990/91 for the former GDR and Poland; examination of life expectancy changes after transition were based on 1992-97 data for Germany and 1991-96 data for Poland. RESULTS: In both the former GDR and Poland male life expectancy at birth declined by almost one year during transition, mainly attributable to rising death rates from external causes and circulatory diseases. Female life expectancy in Poland deteriorated by 0.3 years, largely attributable to increasing circulatory mortality among the old, while in East German female rising death rates in children and young adults were nearly outbalanced by declining circulatory mortality among those over 70. Between 1991/92 and 1996/97, male life expectancy at birth increased by 2.4 years in the former GDR, 1.2 years in old Federal Republic, and 2.0 years in Poland (women: 2.3, 0.9, and 1.2 years). In East Germany and Poland, the overall improvement was largely attributable to falling mortality among men aged 40-64, while those over 65 contributed the largest proportion to life expectancy gains in women. The change in deaths among men aged 15-39 accounted for 0.4 of a year to life expectancy at birth in East Germany and Poland, attributable largely to greater decreases from external causes. Among those over 40, absolute contributions to changing life expectancy were greater in the former GDR than in the other two entities in both sexes, largely attributable to circulatory diseases. A persisting East-west life expectancy gap in Germany of 2.1 years in men in 1997 was largely attributable to external causes, diseases of the digestive system and circulatory diseases. Higher death rates from circulatory diseases among the elderly largely explain the female life expectancy gap of approximately one year. CONCLUSIONS: This study provides further insights into the health effects of political transition. Post-transition improvements in life expectancy and mortality have been much steeper in East Germany compared with Poland. Changes in dietary pattern and, in Germany, medical care may have been important factors in shaping post-transition mortality trends. 相似文献
92.
Byrick R Korley EK McKee M Schemitsch E Probe RA Kallina C 《Journal of orthopaedic trauma》2002,16(3):211-2; author reply 212
93.
Several studies (Vision Research 15 (1975) 583; Perception 9 (1980) 671) have shown that binocular fusion is limited by the disparity gradient (disparity/distance) separating image points, rather than by their absolute disparity values. Points separated by a gradient >1 appear diplopic. These results are sometimes interpreted as a constraint on human stereo matching, rather than a constraint on fusion. Here we have used psychophysical measurements on stereo transparency to show that human stereo matching is not constrained by a gradient of 1. We created transparent surfaces composed of many pairs of dots, in which each member of a pair was assigned a disparity equal and opposite to the disparity of the other member. For example, each pair could be composed of one dot with a crossed disparity of 6' and the other with uncrossed disparity of 6', vertically separated by a parametrically varied distance. When the vertical separation between the paired dots was small, the disparity gradient for each pair was very steep. Nevertheless, these opponent-disparity dot pairs produced a striking appearance of two transparent surfaces for disparity gradients ranging between 0.5 and 3. The apparent depth separating the two transparent planes was correctly matched to an equivalent disparity defined by two opaque surfaces. A test target presented between the two transparent planes was easily detected, indicating robust segregation of the disparities associated with the paired dots into two transparent surfaces with few mismatches in the target plane. Our simulations using the Tsai-Victor model show that the response profiles produced by scaled disparity-energy mechanisms can account for many of our results on the transparency generated by steep gradients. 相似文献
94.
Local disparity signals must interact in visual cortex to represent boundaries and surfaces of three-dimensional (3D) objects. We investigated how disparity signals interact in 3D contours and in 3D surfaces generated from the contours. We compared flat (single disparity) stimuli with curved (multi-disparity) stimuli. We found no consistent differences in sensitivity to contours vs. surfaces; for equivalent amounts of disparity, however, observers were more sensitive to flat stimuli than curved stimuli. Poor depth sensitivity for curved stimuli cannot be explained by the larger range of disparities present in the curved surface, nor by disparity averaging, nor by poor sensitivity to the largest disparity in the stimulus. Surprisingly, sensitivity to surfaces curved in depth was improved by removing portions of the surface and thus removing disparity information. Stimulus configuration had a profound effect on stereo thresholds that cannot be accounted for by disparity-energy models of V1 processing. We suggest that higher-level 3D contour or 3D shape mechanisms are involved. 相似文献
95.
96.
Researchers have suggested that educational attainment and occupational status--indicators of cognitive and/or neurologic "reserve"--can help persons compensate for clinical manifestations of Alzheimer's disease (AD), such as the rates of cognitive and functional decline. The effects of educational attainment on rates of decline could be "direct" independent of occupational status), "indirect" (working through occupational status), or both. We used multilevel analysis for repeated measures to study the effects of educational attainment and occupational status on rates of decline in cognition (Mini-Mental State Examination, MMSE) and function (Cleveland Scale for Activities of Daily Living). Subjects included persons with "probable" or "possible" AD, drawn from our Alzheimer's Disease Research Center registry (N = 482 in the analysis of cognitive decline, and N = 450 in the analysis of functional decline). When controlling for year of birth, gender, ethnicity, and duration of illness, we found that there was an inverse relationship between number of years of education and rate of decline in MMSE, but effects of occupational status were not significant. This implies a "direct" effect of education on decline in MMSE, but no "indirect" effect through occupational status. Neither educational attainment nor occupational status affected rate of decline in functional ability. We conclude that education slows the rate of cognitive decline in persons with AD, but not through its impact on occupational status. Thus, the protective effects of reserve may be established early in life, before people enter the workforce. 相似文献
97.
Chervyakov VV Shkolnikov VM Pridemore WA McKee M 《Social science & medicine (1982)》2002,55(10):1713-1724
The death rate from homicide in Russia increased rapidly during the 1990 s. It is now about 20 times higher than in western Europe and is among the highest recorded anywhere in the world. However, this issue has received little attention so far from public health researchers or policymakers.This paper describes the changing nature of homicide during the 1990 s in Russia as a whole and, in more detail, in the Udmurt Republic. The study uses data from three sources: routine mortality data for Russia from 1970 to 1999; statistics on criminal investigations and convictions in Russia between 1990 and 1997; and an in-depth study of homicide trial records in the Udmurt Republic in 1989-1991 and 1998.Deaths from homicide increased between 1970 and 1985, falling slightly during the 1985 anti-alcohol campaign and then resuming their increase until 1994. Another fall in the late 1990 s was arrested in 1998, with an increase in 1999. By 1999 the age standardised homicide death rate in Russia was 81% higher than in 1990, an increase almost twice that of all causes of death combined. Throughout the 1990 s about 10% of those convicted of homicide were female. Of those homicides leading to convictions in the Udmurt Republic, 71% of those killed by males were male, as were 76% of those killed by females. Killings of women by men often involved sexual assaults. In Russia as a whole, about 80% of those convicted of homicide were reported to be under the influence of alcohol at the time. In the Udmurt Republic, where data on both offender and victim were available, victims were also commonly intoxicated.The nature of homicide in Russia has changed considerably in less than a decade, with many more now involving aggravating circumstances, such as murder to conceal another crime, in association with robbery or rape, or by a group of people. Although still a small proportion of the total convicted, the number of murders by hired killers is also on the rise.The characteristics of those convicted of homicide have also changed during the 1990 s. They are now younger, less likely to have previous convictions, and to have a more diverse range of educational levels. The previous urban-rural gap, with higher levels in rural areas, has also narrowed. 相似文献
98.
Earlier findings have shown that after unification with the Federal Republic of Germany (FRG) in October 1990 the proportion of very-low-birthweight infants in the former German Democratic Republic (GDR) increased. This study seeks to explore this observation in more detail at the regional level. The analysis of aggregate data of live births in Germany between 1991 and 1997 shows an increasing proportion of very-low-birthweight infants as well as a general trend towards heavier babies in both east and west. The growing proportion of live born infants at very low birthweights in the east, however, seems to be due, in part, to increased registration, most likely reflecting the introduction of the more comprehensive (western) definition of a live birth with unification in October 1990. A fairly distinct east-west pattern in the birthweight distribution present in 1991 had almost disappeared by 1997 and given way to a north-south one. 相似文献
99.
Economic and demographic trends signal an impending physician shortage 总被引:11,自引:0,他引:11
It is widely believed that the United States is producing too many physicians. We have approached this issue by developing a new model for workforce planning based on assessments of the macrotrends that underlie the supply and use of physician services. These trends include economic expansion, population growth, physicians' work effort, and the provision of services by nonphysician clinicians. Contrary to earlier predictions, this model projects that the United States soon will have a shortage of physicians and that if the pace of medical education remains unchanged, the shortage will become more severe. A dialogue focused on that eventuality is imperative. 相似文献
100.