全文获取类型
收费全文 | 322789篇 |
免费 | 10885篇 |
国内免费 | 771篇 |
专业分类
耳鼻咽喉 | 2504篇 |
儿科学 | 10372篇 |
妇产科学 | 5699篇 |
基础医学 | 36461篇 |
口腔科学 | 4946篇 |
临床医学 | 26510篇 |
内科学 | 62645篇 |
皮肤病学 | 3516篇 |
神经病学 | 30695篇 |
特种医学 | 14730篇 |
外国民族医学 | 6篇 |
外科学 | 50853篇 |
综合类 | 4200篇 |
现状与发展 | 2篇 |
一般理论 | 139篇 |
预防医学 | 28558篇 |
眼科学 | 5839篇 |
药学 | 19647篇 |
2篇 | |
中国医学 | 868篇 |
肿瘤学 | 26253篇 |
出版年
2023年 | 818篇 |
2022年 | 1239篇 |
2021年 | 2829篇 |
2020年 | 1958篇 |
2019年 | 2826篇 |
2018年 | 24865篇 |
2017年 | 19652篇 |
2016年 | 22058篇 |
2015年 | 4370篇 |
2014年 | 5770篇 |
2013年 | 7503篇 |
2012年 | 17220篇 |
2011年 | 31499篇 |
2010年 | 24575篇 |
2009年 | 17177篇 |
2008年 | 28994篇 |
2007年 | 31822篇 |
2006年 | 10786篇 |
2005年 | 12621篇 |
2004年 | 13218篇 |
2003年 | 13624篇 |
2002年 | 11234篇 |
2001年 | 1730篇 |
2000年 | 1500篇 |
1999年 | 1744篇 |
1998年 | 2291篇 |
1997年 | 1832篇 |
1996年 | 1501篇 |
1995年 | 1386篇 |
1994年 | 1231篇 |
1993年 | 1168篇 |
1992年 | 809篇 |
1991年 | 864篇 |
1990年 | 728篇 |
1989年 | 666篇 |
1988年 | 607篇 |
1987年 | 608篇 |
1986年 | 527篇 |
1985年 | 562篇 |
1984年 | 655篇 |
1983年 | 584篇 |
1982年 | 782篇 |
1981年 | 701篇 |
1980年 | 641篇 |
1979年 | 366篇 |
1978年 | 383篇 |
1977年 | 406篇 |
1976年 | 350篇 |
1975年 | 298篇 |
1974年 | 267篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
21.
22.
23.
24.
25.
Konrad Matyja Anna Małachowska-Jutsz Anna K. Mazur Kazimierz Grabas 《Ecotoxicology (London, England)》2016,25(5):924-939
Dehydrogenase activity is frequently used to assess the general condition of microorganisms in soil and activated sludge. Many studies have investigated the inhibition of dehydrogenase activity by various compounds, including heavy metal ions. However, the time after which the measurements are carried out is often chosen arbitrarily. Thus, it can be difficult to estimate how the toxic effects of compounds vary during the reaction and when the maximum of the effect would be reached. Hence, the aim of this study was to create simple and useful mathematical model describing changes in dehydrogenase activity during exposure to substances that inactivate enzymes. Our model is based on the Lagergrens pseudo-first-order equation, the rate of chemical reactions, enzyme activity, and inactivation and was created to describe short-term changes in dehydrogenase activity. The main assumption of our model is that toxic substances cause irreversible inactivation of enzyme units. The model is able to predict the maximum direct toxic effect (MDTE) and the time to reach this maximum (TMDTE). In order to validate our model, we present two examples: inactivation of dehydrogenase in microorganisms in soil and activated sludge. The model was applied successfully for cadmium and copper ions. Our results indicate that the predicted MDTE and TMDTE are more appropriate than EC50 and IC50 for toxicity assessments, except for long exposure times. 相似文献
26.
27.
28.
Tobias Kisch Julia Maria Klemens Katharina Hofmann Eirini Liodaki Matthias Gierloff Dirk Moellmeier Felix Stang Peter Mailaender Jens Habermann Matthias Brandenburger 《Medicine》2015,94(41)
The regrowth of amputated digit tips represents a unique regenerative healing in mammals with subcutaneous volume regrowth, restoration of dactylogram, and suppression of scar formation. Although factor analysis in amphibians and even in mice is easy to obtain, safety of harvesting biomaterial from human digit tip amputations for analysis has not yet been described.The aim of this study was to evaluate if recovering wound exudate does hamper clinical outcome or influence microbiologic or inflammation status.A predefined cohort of 18 patients with fresh digit tip amputations was randomly assigned to receive standard therapy (debridement, occlusive dressing) with (n = 9) or without (n = 9) collection of the whole wound exudate in every dressing change. Primary endpoint (lengthening) and secondary endpoints (regeneration of dactylogram, nail bed and bone healing, time to complete wound closure, scar formation, 2-point discrimination, microbiologic analysis, inflammatory factors interleukin (IL)-1α, tumor necrosis factor-α, IL-4, and IL-6) were determined by an independent, blinded observer.Patients’ characteristics showed no significant differences between the groups. All patients completed the study to the end of 3 months follow-up. Exudate collection did not influence primary and secondary endpoints. Furthermore, positive microbiologic findings as well as pus- and necrosis-like appearance neither impaired tissue restoration nor influenced inflammatory factor release.Here, the authors developed an easy and safe protocol for harvesting wound exudate from human digit tip amputations. For the first time, it was shown that harvesting does not impair regenerative healing. Using this method, further studies can be conducted to analyze regeneration associated factors in the human digit tip.DRKS.de Identifier: DRKS00006882 (UTN: U1111-1166-5723). 相似文献
29.
Contraceptive use is an important strategy for the prevention of unwanted pregnancy and avoidance of induced abortion. Of all the contraception methods, emergency contraceptive (EC) offers the last chance to achieve this. However, few studies have documented the use of EC among young people in Ghana. This study explored knowledge and usage of EC as well as the factors associated with it among University of Cape Coast students. Data were obtained on the knowledge and usage of ECs among University of Cape Coast students in 2013. Logistic regression analysis was used to investigate the association between students’ socio-demographic characteristics and EC knowledge and use. More male students (72 %) than females (59 %) were sexually active. Fifty-seven percent of the respondents had ever heard of EC and 36 % had ever used EC. Although males were more likely to be sexually active, females were more likely to have knowledge of EC use compared to males. The study underscores the need to increase awareness regarding EC among University students in order to offer them the opportunity that EC provides if other forms of contraceptives are missed. 相似文献
30.