首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1527篇
  免费   93篇
  国内免费   10篇
耳鼻咽喉   8篇
儿科学   37篇
妇产科学   30篇
基础医学   199篇
口腔科学   10篇
临床医学   162篇
内科学   304篇
皮肤病学   25篇
神经病学   92篇
特种医学   31篇
外科学   281篇
综合类   23篇
预防医学   169篇
眼科学   23篇
药学   127篇
中国医学   7篇
肿瘤学   102篇
  2024年   2篇
  2023年   11篇
  2022年   30篇
  2021年   47篇
  2020年   37篇
  2019年   37篇
  2018年   46篇
  2017年   39篇
  2016年   42篇
  2015年   60篇
  2014年   51篇
  2013年   82篇
  2012年   144篇
  2011年   143篇
  2010年   64篇
  2009年   67篇
  2008年   98篇
  2007年   84篇
  2006年   87篇
  2005年   72篇
  2004年   77篇
  2003年   65篇
  2002年   62篇
  2001年   24篇
  2000年   17篇
  1999年   15篇
  1998年   11篇
  1997年   6篇
  1996年   5篇
  1995年   4篇
  1993年   4篇
  1992年   5篇
  1991年   5篇
  1990年   8篇
  1989年   7篇
  1988年   8篇
  1987年   6篇
  1986年   10篇
  1984年   6篇
  1983年   3篇
  1982年   2篇
  1981年   2篇
  1979年   2篇
  1978年   4篇
  1977年   5篇
  1975年   4篇
  1973年   2篇
  1971年   3篇
  1970年   7篇
  1965年   2篇
排序方式: 共有1630条查询结果,搜索用时 15 毫秒
91.
At the western Mediterranean coast of Morocco, the cockle (Acanthocardia tuberculatum) contained persistent high levels of paralytic shellfish toxins for several years, while other bivalve molluscs such as sweet clam (Callista chione) from the same vicinity were contaminated seasonally to a much lesser extent. In order to understand the causes of this prolonged contamination, a comparative study on PSP decontamination between sweet clam and cockle was conducted from November 2001 until June 2002. PSP toxicity was analysed by automated pre-column oxidation (Prechromatographic oxidation and LC-FD) in several organs of both species, namely digestive gland, foot, gill, mantle, muscle and siphon for sweet clams. The results showed that cockle sequester PSP toxins preferably in non-visceral organs (Foot, gill and mantle) contrary to sweet clam that sequester them in visceral tissues (digestive gland). The toxin profile of cockle organs indicated dominance of dcSTX, whereas sweet clam tissues contained especially C-toxins. Substantial differences in toxin profile between cockle and sweet clam, from the same area as well as from the composition of PSP toxin producer, Gymnodinium catenatum, confirm the bioconversion of PSP toxins in cockle.  相似文献   
92.
The present study was designed to investigate the adverse reproductive effects of acetamiprid, besides the possible protective role of Nigella sativa oil (NSO), as a potential antioxidant agent. Thirty-two male Wistar rats were allocated into four equal groups of eight, control (CRL), acetamiprid (ACMP, 27?mg/kg), Nigella sativa oil (NSO, 0.5?ml/kg) and in combination (ACMP?+?NSO). The experimental animals were dosed by gavage (5?days per week) for 45 consecutive days. Body weight gain, reproductive organs weights, sperm characteristics, testosterone, and thiobarbutiric acid-reactive substances (TBARS) levels were investigated. The obtained results showed that ACMP decreased significantly (p?p?p?p?相似文献   
93.
This study presents the relationships between ambient air pollutants and morbidity and emergency department visits among children and adults performed in Great Casablanca, the most populated and economic region in Morocco. This research was analyzed using conditional Poisson model for the period 2011–2013. In the period of study, the daily average concentrations of SO2, NO2, O3 and PM10 in Casablanca were 209.4 µg/m3, 61 µg/m3, 113.2 µg/m3 and 75.1 µg/m3, respectively. In children less than 5 years old, risk of asthma could be increased until 12% per 10 µg/m3 increase in NO2, PM10, SO2 and O3. In children over 5 years and adults, an increase of 10 µg/m3 air pollutant can cause an increase until 3% and 4% in respiratory consultations and acute respiratory infection, respectively. Similarly, impact on emergency department visits due to respiratory and cardiac illness was established. Our results suggest a not negligible impact on morbidity of outdoor air pollution by NO2, SO2, O3, and PM10.  相似文献   
94.
The treatment of metastatic lesions in the brain represents a serious unmet medical need in the field of neuro-oncology. Even though many effective compounds have demonstrated success in treating peripheral (non-CNS) tumors with targeted agents, one aspect of this lack of success in the brain may be related to poor delivery of otherwise effective compounds. Many factors can influence the brain delivery of these agents, but one key barrier is a heterogeneously “leaky” BBB that expresses efflux transporters that limit the BBB permeability for many targeted agents. Future success in therapeutics for brain metastases must take into account the adequate delivery of “active, free drug” to the target, and may include combinations of targeted drugs that are appropriate to address each individual patient’s tumor type. This review discusses some issues that are pertinent to precision medicine for brain metastases, using specific examples of tumor types that have a high incidence of brain metastases.  相似文献   
95.
Scorpion venoms are very complex mixtures of molecules, most of which are peptides displaying different kinds of biological activity. Indeed, these peptides specifically bind to a variety of pharmacological targets, in particular ionic channels located in prey tissues, resulting in neurotoxic effects. Toxins modulating Na+, K+, Ca2+ and Cl(-) currents have been described in scorpion venoms. In this work, we have used several specific antibodies raised against the most lethal scorpion toxins already described to screen the Moroccan scorpion Androctonus mauretanicus mauretanicus venom in order to characterize new compounds. This immunological screening was also implemented by toxicity tests in mice and with mass spectrometry study, providing new informations on the molecular composition of this venom. In fine, we were able to determine the molecular masses of 70-80 different compounds. According to the immunological data obtained, many toxins cross-react with three sera raised against the most lethal alpha-toxins found in North African scorpion venoms, but not at all with those raised against the main beta-toxins from South and North American venoms. Some of the previously described toxins from Androctonus mauretanicus mauretanicus venom could thus be detected by combining immunological tests, toxicity in mice and molecular masses. Among these toxins, one of them, which showed a mild cross-reaction with the serum raised against AaH I (a highly potent toxin from the venom of Androctonus australis), was identified as Amm III and fully sequenced.  相似文献   
96.
Hepatitis E has emerged as a major transfusion-transmitted infectious risk. Two recipients of plasma from 2 lots (A and B) of pooled solvent/detergent–treated plasma were found to be infected by hepatitis E virus (HEV) that was determined to have been transmitted by the solvent/detergent–treated plasma. HEV RNA viral loads were 433 IU in lot A and 55 IU in lot B. Retrospective studies found that 100% (13/13) of evaluable lot A recipients versus 18% (3/17) of evaluable lot B recipients had been infected by HEV (p<0.001), albeit not necessarily at time of transfusion. Among evaluable recipients, 86% with a transfused HEV RNA load >50,000 IU were infected, most likely by the HEV-containing solvent/detergent–treated plasma, versus only 7% with a transfused HEV RNA load <50,000 IU (p<0.001). Overall, solvent/detergent–treated plasma might harbor HEV. Such an occurrence might result in a dose-dependent risk for transfusion-transmitted hepatitis E.  相似文献   
97.
Organophosphate insecticides are increasingly used as substitutes for organochlorine and carbamate insecticides because of their high efficacity and lower persistence in the environment. Chlorpyrifos (CPF) (O,O-diethyl O-3,5,6-trichloro-2-pyridyl phosphorothioate), an organophosphate considered as one of the most widely used insecticides in agriculture worldwide. The aim of this work is to analyze oxidative stress after a chronic exposure per Os to two doses of CPF (375 ppm,750 ppm) and the effect on mitochondrial swelling and respiration and cytoplasmic Cyt c amount. Our results showed a little increase in the activity of mitochondrial GST, level of MDA and a decrease in GPx and CAT activity confirmed by the lack of O2 (respiration inhibition), GSH level in mitochondria. we found an increase in mitochondrial swelling with a significant decrease in respiratory level. The amount of escaped Cytochrome c from mitochondria was significantly increased in treated groups according to the control in doses-dependent manner. Finally, our study showed that Chlorpyrifos caused general mitochondrial dysfunction accompanied with elevated oxidative stress amount in rabbit’s liver.  相似文献   
98.
Three cases of atypical pneumonia in individuals working at a poultry slaughterhouse prompted an epidemiological survey in 10 poultry farms that had supplied birds. Using a Chlamydiaceae-specific real-time PCR assay, chlamydial agents were detected in 14 of 25 investigated flocks. Rather unexpectedly, Chlamydophila psittaci was identified only in one of the positive flocks, whereas ArrayTube DNA microarray testing indicated the presence of a new, so far unclassified member of the genus Chlamydophila.For further characterization of the agent involved, positive cloacal swabs were used to inoculate embryonated chicken eggs and isolates were obtained from 6 different flocks. Sequencing of 16S rRNA genes revealed nearly identical sequences of all samples. Alignment with representative sequences of Chlamydiaceae showed the separate position of the present strains outside the currently recognized species of Chlamydophila, but clearly within this genus. In contrast, partial ompA gene sequences displayed considerable diversity among the isolates, which had already been observed in restriction enzyme analysis of ompA PCR products. These data suggest that each farm had been infected with a different strain of this new chlamydial agent, the zoonotic potential and the exact taxonomic status of which have yet to be defined.  相似文献   
99.
The sudden death in athletes is, in the vast majority of cases, related to ventricular fibrillation, often in a subject with unknown cardiovascular abnormality; this dramatic event has a significant impact on society and the medical profession. We conducted through a literature review an analysis of data on sudden cardiac death of rhythmic origin in athletes; sudden death may be cardiovascular in 95.3% of cases and related to ventricular arrhythmia in 88% cases. The main causes are: hypertrophic cardiomyopathy, congenital anomalies of coronary arteries, and arhythmogenic right ventricular dysplasia for athletes under 35 years, and atherosclerosis beyond 35 years. Prevention is based on three main areas: the medical assessment and screening for cardiovascular disease; the chain of survival; the education of the athlete and the public. All these measures should improve significantly the survival prognosis of patients suffering from these accidents.  相似文献   
100.
Three hundred and twelve patients with severe aortic valve disease underwent a pre-operative haemodynamic study including coronary arteriography either as routine (age more than 50 years) or because of chest pains, previous myocardial infarction or for patients with risk factors of coronary atherosclerosis. Significant coronary artery disease was present in 9% of all cases. Coronary artery disease was more frequent in patients with angina and in patients with previous myocardial infarction but none of these factors was specific. We conclude that except young patients < 40 years old, with no chest pain and no coronary risk factors, coronary arteriography is recommended in patients with severe aortic valve disease before aortic valve replacement.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号