全文获取类型
收费全文 | 1475656篇 |
免费 | 99197篇 |
国内免费 | 2005篇 |
专业分类
耳鼻咽喉 | 19791篇 |
儿科学 | 51563篇 |
妇产科学 | 38601篇 |
基础医学 | 203198篇 |
口腔科学 | 35243篇 |
临床医学 | 125711篇 |
内科学 | 292694篇 |
皮肤病学 | 28893篇 |
神经病学 | 118155篇 |
特种医学 | 60774篇 |
外国民族医学 | 660篇 |
外科学 | 229245篇 |
综合类 | 29746篇 |
现状与发展 | 1篇 |
一般理论 | 405篇 |
预防医学 | 115360篇 |
眼科学 | 30789篇 |
药学 | 105380篇 |
2篇 | |
中国医学 | 3053篇 |
肿瘤学 | 87594篇 |
出版年
2018年 | 35905篇 |
2017年 | 28103篇 |
2016年 | 32097篇 |
2015年 | 13510篇 |
2014年 | 18197篇 |
2013年 | 27404篇 |
2012年 | 43380篇 |
2011年 | 60133篇 |
2010年 | 41985篇 |
2009年 | 34028篇 |
2008年 | 58090篇 |
2007年 | 63906篇 |
2006年 | 40533篇 |
2005年 | 41746篇 |
2004年 | 42431篇 |
2003年 | 42848篇 |
2002年 | 39976篇 |
2001年 | 64460篇 |
2000年 | 67240篇 |
1999年 | 56728篇 |
1998年 | 15483篇 |
1997年 | 14169篇 |
1996年 | 14405篇 |
1995年 | 13678篇 |
1994年 | 12995篇 |
1993年 | 11982篇 |
1992年 | 44703篇 |
1991年 | 43652篇 |
1990年 | 42415篇 |
1989年 | 40256篇 |
1988年 | 37019篇 |
1987年 | 36373篇 |
1986年 | 33727篇 |
1985年 | 32397篇 |
1984年 | 24222篇 |
1983年 | 20350篇 |
1982年 | 11843篇 |
1981年 | 10723篇 |
1980年 | 9636篇 |
1979年 | 21434篇 |
1978年 | 14890篇 |
1977年 | 12551篇 |
1976年 | 11760篇 |
1975年 | 12631篇 |
1974年 | 14699篇 |
1973年 | 14126篇 |
1972年 | 12944篇 |
1971年 | 11729篇 |
1970年 | 11080篇 |
1969年 | 10061篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Worsening pneumonitis due to a pharmacokinetic drug–drug interaction between everolimus and voriconazole in a renal transplant patient 下载免费PDF全文
62.
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
63.
64.
65.
HIV risk in vulnerable groups such as itinerant male street labourers is often examined via a focus on individual determinants. This study provides a test of a modified Information-Motivation-Behavioral Skills (IMB) model to predict condom use behaviour among male street workers in urban Vietnam. In a cross-sectional survey using a social mapping technique, 450 male street labourers from 13 districts of Hanoi, Vietnam were recruited and interviewed. Collected data were first examined for completeness; structural equation modelling was then employed to test the model fit. Condoms were used inconsistently by many of these men, and usage varied in relation to a number of factors. A modified IMB model had a better fit than the original IMB model in predicting condom use behaviour. This modified model accounted for 49% of the variance, versus 10% by the original version. In the modified model, the influence of psychosocial factors was moderately high, whilst the influence of HIV prevention information, motivation and perceived behavioural skills was moderately low, explaining in part the limited level of condom use behaviour. This study provides insights into social factors that should be taken into account in public health planning to promote safer sexual behaviour among Asian male street labourers. 相似文献
66.
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
67.
D. Panigrahy P. K. Sahu 《Australasian physical & engineering sciences in medicine / supported by the Australasian College of Physical Scientists in Medicine and the Australasian Association of Physical Sciences in Medicine》2016,39(3):783-795
Electrocardiogram (ECG) signal gives a lot of information on the physiology of heart. In reality, noise from various sources interfere with the ECG signal. To get the correct information on physiology of the heart, noise cancellation of the ECG signal is required. In this paper, the effectiveness of extended Kalman smoother (EKS) with the differential evolution (DE) technique for noise cancellation of the ECG signal is investigated. DE is used as an automatic parameter selection method for the selection of ten optimized components of the ECG signal, and those are used to create the ECG signal according to the real ECG signal. These parameters are used by the EKS for the development of the state equation and also for initialization of the parameters of EKS. EKS framework is used for denoising the ECG signal from the single channel. The effectiveness of proposed noise cancellation technique has been evaluated by adding white, colored Gaussian noise and real muscle artifact noise at different SNR to some visually clean ECG signals from the MIT-BIH arrhythmia database. The proposed noise cancellation technique of ECG signal shows better signal to noise ratio (SNR) improvement, lesser mean square error (MSE) and percent of distortion (PRD) compared to other well-known methods. 相似文献
68.
69.
70.
Gastroesophageal reflux is the most common benign disorder of the esophagus and laparoscopic Nissen fundoplication has become the standard surgical treatment for its treatment. In our area, where the use of bougie calibration is debatable, postoperative dysphagia is encountered often after this surgery although it is usually not permanent. The aim of this study was to investigate the effect of using a soft silicone tube 39 F in diameter for esophageal calibration during laparoscopic Nissen fundoplication on the incidence of postoperative dysphagia. We divided cases scheduled to undergo laparoscopic Nissen fundoplication between January 2009 and November 2010 into two groups, each consisting 25 patients. Esophageal calibration with a 39 F silicone orogastric tube was used for the first group while there was no operative calibration in the second group. The surgical duration was recorded; the presence and severity of the postoperative dysphagia was calculated by using a dysphagia severity scoring system during the 1-year postoperative follow-up. The dysphagia severity scores were significantly lower in group 1 than group 2 on the postoperative second day and at the end of the first week and first month. We did not find a significant difference at the end of the 6-month and first year. There was also no significant difference regarding surgery duration. The use of a soft orogastric tube 39 F in diameter for esophagus calibration during laparoscopic Nissen fundoplication has significantly decreased the incidence of postoperative transient dysphagia without affecting the duration of surgery. Although dysphagia gradually resolves in the majority of patients, a safe and easy calibration method for its prevention is worth developing, and we believe that the use of our method in larger series could be beneficial. 相似文献