全文获取类型
收费全文 | 328233篇 |
免费 | 11954篇 |
国内免费 | 623篇 |
专业分类
耳鼻咽喉 | 2855篇 |
儿科学 | 10391篇 |
妇产科学 | 5555篇 |
基础医学 | 36870篇 |
口腔科学 | 4882篇 |
临床医学 | 27355篇 |
内科学 | 63344篇 |
皮肤病学 | 3880篇 |
神经病学 | 30549篇 |
特种医学 | 15530篇 |
外国民族医学 | 14篇 |
外科学 | 53109篇 |
综合类 | 4246篇 |
一般理论 | 109篇 |
预防医学 | 29350篇 |
眼科学 | 5982篇 |
药学 | 19282篇 |
中国医学 | 861篇 |
肿瘤学 | 26646篇 |
出版年
2023年 | 885篇 |
2022年 | 1486篇 |
2021年 | 3374篇 |
2020年 | 2081篇 |
2019年 | 3127篇 |
2018年 | 25031篇 |
2017年 | 19732篇 |
2016年 | 22135篇 |
2015年 | 4438篇 |
2014年 | 5825篇 |
2013年 | 7550篇 |
2012年 | 17043篇 |
2011年 | 31337篇 |
2010年 | 24591篇 |
2009年 | 17142篇 |
2008年 | 28642篇 |
2007年 | 31240篇 |
2006年 | 10536篇 |
2005年 | 12152篇 |
2004年 | 12530篇 |
2003年 | 12763篇 |
2002年 | 10606篇 |
2001年 | 2390篇 |
2000年 | 2229篇 |
1999年 | 2273篇 |
1998年 | 2110篇 |
1997年 | 1741篇 |
1996年 | 1415篇 |
1995年 | 1343篇 |
1994年 | 1214篇 |
1993年 | 1070篇 |
1992年 | 1325篇 |
1991年 | 1267篇 |
1990年 | 1147篇 |
1989年 | 1045篇 |
1988年 | 958篇 |
1987年 | 921篇 |
1986年 | 903篇 |
1985年 | 893篇 |
1984年 | 942篇 |
1983年 | 815篇 |
1982年 | 983篇 |
1981年 | 860篇 |
1980年 | 767篇 |
1979年 | 656篇 |
1978年 | 654篇 |
1977年 | 536篇 |
1976年 | 522篇 |
1974年 | 530篇 |
1973年 | 450篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
Frédéric Janvier Deborah Delaune Thomas Poyot Eric Valade Audrey Mérens Pierre E. Rollin Vincent Foissaud 《Emerging infectious diseases》2016,22(2):292-294
We evaluated RNA stability of Ebola virus in EDTA blood and urine samples collected from infected patients and stored in West Africa’s environmental conditions. In blood, RNA was stable for at least 18 days when initial cycle threshold values were <30, but in urine, RNA degradation occurred more quickly. 相似文献
52.
53.
The specific role of postsynaptic activity for the generation of a functional magnetic resonance imaging (fMRI) response was determined by a simultaneous measurement of generated field excitatory postsynaptic potentials (fEPSPs) and blood oxygen level-dependent (BOLD) response in the rat hippocampal CA1 region during electrical stimulation of the contralateral CA3 region. The stimulation electrode was placed either in the left CA3a/b or CA3c, causing the preferentially basal or apical dendrites of the pyramidal cells in the right CA1 to be activated. Consecutive stimulations with low-intensity stimulation trains (i.e., 16 pulses for 8 seconds) resulted in clear postsynaptic responses of CA1 pyramidal cells, but in no significant BOLD responses. In contrast, consecutive high-intensity stimulation trains resulted in stronger postsynaptic responses that came along with minor (during stimulation of the left CA3a/b) or substantial (during stimulation of the left CA3c) spiking activity of the CA1 pyramidal cells, and resulted in the generation of significant BOLD responses in the left and right hippocampus. Correlating the electrophysiologic parameters of CA1 pyramidal cell activity (fEPSP and spiking activity) with the resultant BOLD response revealed no positive correlation. Consequently, postsynaptic activity of pyramidal cells, the most abundant neurons in the CA1, is not directly linked to the measured BOLD response. 相似文献
54.
55.
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
56.
57.
58.
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
59.
60.