全文获取类型
收费全文 | 2771篇 |
免费 | 169篇 |
国内免费 | 68篇 |
专业分类
耳鼻咽喉 | 8篇 |
儿科学 | 121篇 |
妇产科学 | 57篇 |
基础医学 | 370篇 |
口腔科学 | 84篇 |
临床医学 | 305篇 |
内科学 | 548篇 |
皮肤病学 | 98篇 |
神经病学 | 130篇 |
特种医学 | 360篇 |
外科学 | 341篇 |
综合类 | 36篇 |
预防医学 | 192篇 |
眼科学 | 35篇 |
药学 | 159篇 |
中国医学 | 2篇 |
肿瘤学 | 162篇 |
出版年
2021年 | 25篇 |
2020年 | 19篇 |
2019年 | 24篇 |
2018年 | 31篇 |
2017年 | 18篇 |
2016年 | 21篇 |
2015年 | 47篇 |
2014年 | 46篇 |
2013年 | 90篇 |
2012年 | 84篇 |
2011年 | 79篇 |
2010年 | 79篇 |
2009年 | 108篇 |
2008年 | 110篇 |
2007年 | 118篇 |
2006年 | 92篇 |
2005年 | 103篇 |
2004年 | 66篇 |
2003年 | 77篇 |
2002年 | 75篇 |
2001年 | 70篇 |
2000年 | 78篇 |
1999年 | 85篇 |
1998年 | 89篇 |
1997年 | 95篇 |
1996年 | 115篇 |
1995年 | 77篇 |
1994年 | 63篇 |
1993年 | 65篇 |
1992年 | 55篇 |
1991年 | 42篇 |
1990年 | 41篇 |
1989年 | 64篇 |
1988年 | 66篇 |
1987年 | 55篇 |
1986年 | 64篇 |
1985年 | 64篇 |
1984年 | 23篇 |
1983年 | 29篇 |
1982年 | 20篇 |
1981年 | 28篇 |
1980年 | 29篇 |
1979年 | 27篇 |
1978年 | 36篇 |
1977年 | 23篇 |
1976年 | 24篇 |
1975年 | 31篇 |
1974年 | 24篇 |
1973年 | 18篇 |
1971年 | 14篇 |
排序方式: 共有3008条查询结果,搜索用时 15 毫秒
1.
2.
Nutrition labels in bar graph format deemed most useful for consumer purchase decisions using adaptive conjoint analysis 总被引:1,自引:1,他引:0
C J Geiger B W Wyse C R Parent R G Hansen 《Journal of the American Dietetic Association》1991,91(7):800-807
This study estimated the effects of changing multiple levels and combinations of nutrition information format, load, expression, and order on consumers' perceptions of label usefulness in purchase decisions using adaptive conjoint analysis. A shopping mall intercept survey, which was administered by a marketing research firm, assessed consumer preferences for 12 label alternatives produced on Campbell's soup cans to portray nutrition information realistically; 252 of 258 respondents completed the computer interactive interview. Consumers significantly preferred the bar graph format to the bar graph/nutrient density and traditional label formats. Consumers considered the bar graph/nutrient density format to be as useful as the traditional label format. There was a highly significant difference among the three levels of information load; the most information load was preferred regardless of nutrient importance. Consumers significantly preferred nutrition information stated in absolute numbers and percentages vs in absolute numbers only in traditional, or in percentages only expressions. There was a significant difference between consumer preferences for the two types of information order. The findings indicate that consumers clearly preferred the nutrition label that displayed all nutrient values using a bar graph format, offered the most information load, and expressed nutrient values using both absolute numbers and percentages. Consumers also preferred nutrition information rearranged in an order that grouped nutrients that should be consumed in adequate amounts on the top, calories in the middle, and nutrients that should be consumed in lesser amounts on the bottom of the label. 相似文献
3.
4.
Armin W. Geiger M.D. F.I.C.A. Alexander M. Zarubin Ph.D. Marc Hertel Anke Fahrenkamp M.D. Gert von Bally Hans H. Scheld M.D. F.I.C.A. 《The International journal of angiology》1995,4(1):46-50
Dysfunction of heart valve prostheses—mechanical as well as biological—is a common problem in cardiac surgery. The reasons for the valve failures are still not well understood. Biological valves especially have an unsatisfactory durability; degeneration and calcification very often lead to the failure of the valves. In our opinion, hidden defects present in the valve material prior to implantation of the valves is a plausible explanation for the dysfunction. Hitherto there has been no technique to detect these defects without destructing the specimen. Holographic interferometry proved to be applicable forin vitro evaluation of mechanical heart valve prostheses. In the present paper we describe application of this method to biological valves. Nine porcine bioprostheses and four fresh porcine aortic valves were investigated by means of holographic interferometry. In eight of nine bioprostheses, the results showed irregularities of the leaflet structure which depend on anomalies of the connective tissue of the leaflets of the valves. To make sure that these findings are not due to normal variations of the morphology, the investigations were carried out with fresh and unfixated porcine aortic valves. In the latter, no such anomalies of the structure were detected. The results obtained confirm the above hypothesis on the origin of the later valve dysfunction. Thus, holographic interferometry tests of bioprostheses prior to their implantation prevent the use of potentially dysfunctional valves.Presented at the 35th World Congress, International College of Angiology, Copenhagen, Denmark, July 1993 相似文献
5.
6.
7.
Leonidas JC; Berdon WE; Valderrama E; Neveling U; Schuval S; Weiss SJ; Hilfer C; Godine L 《Radiology》1996,198(2):377
8.
Effects of mycophenolic acid on IL-6 expression of human renal proximal and distal tubular cells in vitro. 总被引:1,自引:0,他引:1
BACKGROUND: Interleukin-6 (IL-6) is a multifunctional cytokine which regulates immune responses and host defence mechanisms. IL-6 has been found to be increased in certain inflammatory conditions of the kidney, in which tubular epithelial cells play a pivotal role. Human renal tubular cells express IL-6. Until now no data about the effect of the immunosuppressant drug mycophenolic acid (MPA) on IL-6 expression were available. METHODS: Proximal and distal tubular epithelial cells (PTC/DTC) have been isolated immunomagnetically. Confluent monolayers were stimulated with interleukin-1beta (IL-1beta; 25 U/ml), IL-1beta+ MPA (0.25-50 micro M) or MPA alone for 48 h. Release of IL-6 protein into the supernatant was evaluated with an enzyme immunoassay, IL-6 mRNA expression was evaluated using the Quantikine mRNA kit. RESULTS: After IL-1beta stimulation, a highly significant 2.6- (PTC) and 3.8-fold (DTC) upregulation of IL-6 expression was detectable. IL-6 mRNA was upregulated by IL-1beta [1.57- (PTC) and 2.03-fold (DTC)]. MPA inhibited this cytokine-induced IL-6 expression in a dose-dependent manner. Incubation with the lowest MPA concentration had no effect on the stimulated upregulation, whereas all higher doses significantly decreased IL-6 expression. Dexamethasone significantly inhibited the cytokine-induced IL-6 protein release in PTC, but not in DTC. CONCLUSIONS: In this study we demonstrated for the first time an inhibitory effect of MPA on the stimulated IL-6 expression of renal tubular epithelial cells. In contrast to older data, which showed a synergistic upregulation of the expression of a CC-chemokine by a combination of cytokines and MPA, in the present study we could demonstrate an immunosuppressive effect of MPA on the expression of an important cytokine. 相似文献
9.
Summary. Originally discovered in 1994 by Folkman and coworkers, angiostatin was identified through its antitumor effects in mice and later shown to be a potent inhibitor of angiogenesis. An internal fragment of plasminogen, angiostatin consists of kringle domains that are known to be lysine-binding. The crystal structure of angiostatin was the first multikringle domain-containing structure to be published. This review will focus on what is known about the structure of angiostatin and its implications in function from the current literature. 相似文献
10.
JC Sitek† M Loeb‡ JR Ronnevig¶ 《Journal of the European Academy of Dermatology and Venereology》2007,21(7):891-896
BACKGROUND: Since 1997, a number of trials have shown promising results in treating generalized vitiligo with narrowband ultraviolet B (UVB) both in adults and children. However, there is little knowledge concerning the duration and permanency of the treatment-induced repigmentation. OBJECTIVE: Our main objective was to perform a follow-up trial of successfully treated patients receiving narrowband UVB for generalized vitiligo. METHODS: We have investigated to what degree the treatment-induced repigmentation remains stable for up to 2 years post-treatment. We performed an initial open trial including 31 patients with generalized vitiligo. They received narrowband UVB thrice weekly for up to 12 months. Patients experiencing > 75% repigmentation were defined responders and were included in the follow-up trial. Responders were followed every 6 months for up to 2 years after cessation of treatment. We observed the pigmentation status and registered any changes indicating loss of pigmentation and relapse. RESULTS: Eleven of the 31 treated patients were included in the follow-up trial. Six patients had relapse and five patients had stable response 24 months after cessation of treatment. Four out of six relapses were within 6 months post-treatment. CONCLUSION: In our study population of 31 patients with generalized vitiligo, five patients (16%) experienced > 75% stable repigmentation 2 years after cessation of a treatment programme of up to 1 years narrowband UVB therapy. 相似文献