全文获取类型
收费全文 | 4915篇 |
免费 | 381篇 |
国内免费 | 6篇 |
专业分类
耳鼻咽喉 | 63篇 |
儿科学 | 170篇 |
妇产科学 | 93篇 |
基础医学 | 699篇 |
口腔科学 | 93篇 |
临床医学 | 886篇 |
内科学 | 829篇 |
皮肤病学 | 27篇 |
神经病学 | 518篇 |
特种医学 | 86篇 |
外科学 | 399篇 |
综合类 | 79篇 |
一般理论 | 1篇 |
预防医学 | 645篇 |
眼科学 | 76篇 |
药学 | 305篇 |
中国医学 | 17篇 |
肿瘤学 | 316篇 |
出版年
2023年 | 28篇 |
2022年 | 64篇 |
2021年 | 79篇 |
2020年 | 73篇 |
2019年 | 89篇 |
2018年 | 116篇 |
2017年 | 81篇 |
2016年 | 79篇 |
2015年 | 82篇 |
2014年 | 120篇 |
2013年 | 222篇 |
2012年 | 275篇 |
2011年 | 310篇 |
2010年 | 167篇 |
2009年 | 128篇 |
2008年 | 268篇 |
2007年 | 316篇 |
2006年 | 297篇 |
2005年 | 304篇 |
2004年 | 265篇 |
2003年 | 279篇 |
2002年 | 273篇 |
2001年 | 74篇 |
2000年 | 65篇 |
1999年 | 67篇 |
1998年 | 62篇 |
1997年 | 61篇 |
1996年 | 35篇 |
1995年 | 47篇 |
1994年 | 50篇 |
1993年 | 35篇 |
1992年 | 44篇 |
1991年 | 35篇 |
1990年 | 41篇 |
1989年 | 33篇 |
1986年 | 37篇 |
1985年 | 46篇 |
1984年 | 41篇 |
1983年 | 30篇 |
1982年 | 52篇 |
1981年 | 44篇 |
1980年 | 47篇 |
1979年 | 26篇 |
1978年 | 27篇 |
1977年 | 30篇 |
1976年 | 37篇 |
1975年 | 31篇 |
1974年 | 28篇 |
1973年 | 26篇 |
1971年 | 28篇 |
排序方式: 共有5302条查询结果,搜索用时 15 毫秒
1.
2.
Robert H. EckelAuthor Vitae Penny Kris-EthertonAuthor Vitae Alice H. LichtensteinAuthor Vitae Judith Wylie-RosettAuthor Vitae Allison Groom Author Vitae Kimberly F. StitzelAuthor Vitae Shirley Yin-PiazzaAuthor Vitae 《Journal of the American Dietetic Association》2009,109(2):288-296
In recent years, epidemiologic and clinical studies, public and regulatory policy activity, and media coverage have focused on issues related to trans fats. To help increase awareness and understanding of trans fats and other fats, the American Heart Association (AHA) launched the “Face the Fats” national consumer education campaign in April 2007. The AHA commissioned a quantitative tracking survey between 2006 and 2007 to measure changes in consumer awareness, knowledge, and behaviors related fats and oils and their perceived impact on heart disease. The survey was conducted by Cogent Research. Data were collected during March 2006 and May 2007. At both time points, the survey included a representative sample of the American population age 18 to 65 years (n=1,000). The sampling plan for the survey was designed based on the 2000 and 2003 US Census. The margin of error was ±3.10 percentage points. Awareness of trans fats increased during the 1-year study period. In 2007, 92% of respondents were aware of trans fats, an increase from 84% in 2006 (P<0.05). The 2007 level was similar to the awareness of saturated fats (93%). Perceptions that certain fats and oils heighten the risk of heart disease increased for trans fats (73% in 2007 vs 63% in 2006; P<0.05), saturated fats (77% in 2007 vs 73% in 2006; P<0.05), and partially hydrogenated oils (56% in 2007 vs 49% in 2006; P<0.05). Knowledge about food sources of different fats remained low. On an unaided basis, 21% could name three food sources of trans fats in 2007, up from 17% in 2006 (P<0.05). Knowledge of food sources of saturated fat remained unchanged at 30% in 2007. Significantly more respondents in 2007 reported behavioral changes related to trans fat information, such as buying food products because they show “zero trans fat” on labels or packages (37% in 2007 vs. 32% in 2006; P<0.05). Between 2006 and 2007, consumer awareness about trans fats increased and attained awareness levels similar to saturated fats. The increased awareness is associated with improved self-reported behaviors in grocery shopping. Nonetheless, overall knowledge, especially regarding food sources of saturated and trans fats, remains relatively low, underscoring the need for heightened consumer education activities. The positive change in consumer awareness about trans fats is likely attributable to the wide range of messages available to them, including the AHA “Face the Fats” national consumer education campaign. 相似文献
3.
Thomas L. Patterson Shirley J. Semple Lydia R. Temoshok J. Hampton Atkinson J. Allen McCutchan Kristy A. Straits-Trster James L. Chandler Igor Grant 《Journal of Applied Biobehavioral Research》1993,1(1):64-87
The significance of life stress, coping, and social support was examined in relation to depressive symptomatology in a sample of 160 asymptomatic and mildly symptomatic HIV-antibody-positive (HIV+) men. The participants (mean age = 32 years) were interviewed about the life stress that they had experienced in the previous 6 相似文献
4.
Shirley L. Jones RNC MS 《Journal of obstetric, gynecologic, and neonatal nursing : JOGNN / NAACOG》1996,25(9):777-783
Advances in human genetics are rapidly changing the scope of information and care that can be provided to health care consumers. By the year 2005 it is expected that the entire human genome will be mapped and all 70,000–100,000 genes will be identified. Currently, there are more than 5,000 known single-gene disorders. With the movement of specialized health services into the primary care setting, nurses increasingly will need to be knowledgeable about genetic disorders, screening/diagnostic tests, and implications for health care. In addition, the management of genetic information raises issues of informed consent, privacy and confidentiality, truth telling and disclosure, and nondiscrimination. 相似文献
5.
6.
Benyam Asefa Paul Kauler Denis Cournoyer Shirley Lehnert T. Y.-K. Chow 《Current genetics》1998,34(5):360-367
The deoxyribonucleases (DNases) have been shown genetically to be important in the vital processes of DNA repair and recombination.
The NUD1 gene, which codes for an endo-exonuclease of Saccharomyces cerevisiae, was analyzed for its role in the DNA double-strand break (DSB) repair processes. While the nud1 strain is only slightly sensitive to ionizing radiation, expression of the HO-endonuclease to introduce a DSB at the MAT locus in that strain results in cell death. Cell survival is inversely proportional to the duration of HO-endonuclease expression.
Analysis of the surviving colonies from the nud1 strain indicated that many of the survivors are sterile and that the proportion of these sterile survivors increases with
the time of HO-endonuclease expression. On the other hand, the surviving colonies from the isogenic NUD1 strain are mating-proficient. Interestingly, double mutants of nud1 rad52 are more resistant to ionizing irradiation than the rad52 strain and have a cell-survival fraction of 32% for rad52-1 nud1 and 9% for rad52::URA3 nud1 following prolonged HO-endonuclease expression, indicating that nud1 has a suppressor effect on the DSB-induced lethality in rad52. Polymerase chain reaction analysis showed that many of the nud1 survivors contained small alterations within the MAT locus, suggesting that the survivors arose through the process of non-homologous end-joining. These results suggest that
the endo-exonuclease acts at a DSB to promote DNA repair via the homologous recombination pathway.
Received: 20 July / 20 September 1998 相似文献
7.
8.
The relationship of perceived control over daily uplifts and hassles to depression and restraint was examined in a sample of 140 middle-class sixth graders. Results indicated that greater control over uplifts was associated with better functioning and lower control over hassles with poorer functioning, even after partialing out the respective number of uplifts and hassles reported. Moreover, when directly compared, control over uplifts showed more powerful associations with adaptational outcomes than did control over hassles. In a separate analysis, the number of uplifts over which children reported high control showed opposite relationships to adaptational outcomes than did the number of uplifts over which children reported low control. A different pattern appeared for hassles. Although the number of hassles with low control was associated with poorer functioning, the number of hassles over which children had high control was unrelated to adaptational outcomes. The possibility that control operates somewhat differently for positive and negative events is discussed.This research was supported by a grant to the second author from the Stanford Center for the Study of Families, Children and Youth. The authors are grateful to Rachelle Hacket for data analysis, Tom Gehring for data collection, and Susan Nolen-Hoeksema for critical comments. 相似文献
9.
Pelvic ultrasound is a widely used diagnostic tool and accessto this investigation is not universally available to all generalpractitioners (GPs). The aim of this study was to assess ifGPs working in the United Arab Emirates (UAE) were using pelvicultrasound appropriately by determining the rates of diagnosticyield and referral after the investigation. It was then ascertainedif these results were affected by the post-graduate trainingor gender of the doctor. The subjects were adult females whohad had a pelvic ultrasound ordered by a GP over a 2-month period.A chart review determined the presenting complaint, the completenessof the request form, the result of the ultrasound and subsequentmanagement of the patient. Diagnostic yields and referral rateswere similar to those found in other studies and were unaffectedby the post graduate training or gender of the doctor or theamount of information contained in the request form. This studysupports the premise that GPs can use pelvic ultrasound appropriatelyand should be allowed free access to this investigation. 相似文献
10.
The random amplification of polymorphic DNA (RAPD method), was used to derive fragments of DNA of the coccidial parasiteEimeria tenella for use both as genetic markers and as an aid for the discrimination of different wild-type and attenuated populations. Of
41 arbitrarily chosen 9-to 27-mer primers, 24 yielded useful arrays of fragments following low-stringency annealing conditions
and the resultant profiles were generally very reproducible. One non-variant fragment of 2 kb hybridised to a single chromosome
(number 12) and four variant fragments were identified. These results strongly suggest that the RAPD method may be an extremely
useful tool for studies on various aspects of the genetic organisation of coccidial parasites. 相似文献