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   4508篇
  免费   383篇
  国内免费   14篇
耳鼻咽喉   35篇
儿科学   176篇
妇产科学   95篇
基础医学   605篇
口腔科学   97篇
临床医学   559篇
内科学   914篇
皮肤病学   55篇
神经病学   480篇
特种医学   239篇
外科学   552篇
综合类   120篇
一般理论   1篇
预防医学   357篇
眼科学   103篇
药学   302篇
中国医学   18篇
肿瘤学   197篇
  2023年   18篇
  2022年   28篇
  2021年   54篇
  2020年   39篇
  2019年   61篇
  2018年   80篇
  2017年   47篇
  2016年   81篇
  2015年   84篇
  2014年   136篇
  2013年   187篇
  2012年   240篇
  2011年   218篇
  2010年   160篇
  2009年   143篇
  2008年   227篇
  2007年   221篇
  2006年   207篇
  2005年   194篇
  2004年   181篇
  2003年   197篇
  2002年   182篇
  2001年   167篇
  2000年   159篇
  1999年   120篇
  1998年   79篇
  1997年   76篇
  1996年   75篇
  1995年   66篇
  1994年   42篇
  1993年   60篇
  1992年   76篇
  1991年   80篇
  1990年   92篇
  1989年   99篇
  1988年   84篇
  1987年   74篇
  1986年   78篇
  1985年   68篇
  1984年   43篇
  1983年   50篇
  1981年   36篇
  1980年   22篇
  1979年   31篇
  1978年   27篇
  1977年   18篇
  1976年   31篇
  1974年   17篇
  1973年   23篇
  1971年   17篇
排序方式: 共有4905条查询结果,搜索用时 15 毫秒
1.
2.
Affinity peptide and protein‐ (APP) based radiotracers are an increasingly popular class of radiotracer in positron emission tomography (PET), which was once dominated by the use of small molecule radiotracers. Radiolabelled monoclonal antibodies (mAbs) are important examples of APPs, yet a preference for smaller APPs, which exhibit fast pharmacokinetics and permit rapid PET aided diagnosis, has become apparent. 18F exhibits favourable physical characteristics for APP radiolabelling and has been described as an ideal PET radionuclide. Notwithstanding, 18F radiolabelling of APP is challenging, and this is echoed in the literature where a number of diverse approaches have been adopted. This review seeks to assess and compare the approaches taken to 18F APP radiolabelling with the intention of highlighting trends within this expanding field. Generic themes have emerged in the literature, namely the use of mild radiolabelling conditions, a preference of site‐specific methodologies with an impetus for short, automated procedures which produce high‐yielding [18F]APPs.  相似文献   
3.
OBJECTIVE: To explore the impact of timing and type of ultrasound, particularly three-dimensional (3D), exposure on maternal-fetal attachment and maternal health behavior during pregnancy. METHODS: Subjects were 68 women aged 18 years or older expecting their first child who presented for a routine ultrasound scan at around either 12 or 18 weeks' gestation in Nepean Hospital, Western Sydney. Women completed questionnaires assessing maternal-fetal attachment and health behavior, and were then allocated arbitrarily to either two-dimensional (2D) or 3D ultrasound examination. Repeat questionnaires were completed 1 week later. RESULTS: Maternal-fetal attachment increased after both 2D and 3D ultrasound exposure, and the effect was moderated by the timing of exposure, with women receiving their first ultrasound examination at around 12 weeks showing the greatest change. Alcohol consumption was the only behavior to show significant change following ultrasound exposure, with a reduction in the reported average number of drinks per week. There was no significant difference in the pattern of change for 2D compared with 3D ultrasound exposure, and no effect of ultrasound exposure on maternal perception of the fetus. CONCLUSIONS: Ultrasound has a positive impact on maternal-fetal attachment, particularly in the first trimester. 3D ultrasound did not offer enhanced benefits. Associations between ultrasound exposure and alcohol consumption warrant further investigation. Larger samples are needed to clarify the moderating effects of gestational age and type of ultrasound exposure.  相似文献   
4.
5.
A 43-year-old alcoholic presented in coma with ketoacidosis, after three days of nausea and feeling generally unwell, which had been preceded by a prolonged three-week period of heavy alcohol consumption with poor dietary intake. The acidosis responded rapidly to intravenous dextrose. This is the first Scottish report of a case of alcoholic ketoacidosis.  相似文献   
6.
Esophageal perforation is associated with a significant risk of morbidity and mortality. We report herein a case of lye-induced esophageal perforation managed successfully by employing endoscopic T-tube placement with a successful outcome.  相似文献   
7.
Instillation of human neutrophil elastase (HNE) into hamster lungs produces milder emphysema but more pulmonary hemorrhage than an equivalent amount of porcine pancreatic elastase (PPE), whether equivalence is determined by elastolytic units or moles. We undertook a study of the mechanisms of these differences. 125I-HNE or 3H-PPE were instilled intratracheally into hamsters. The partitioning of radioactivity between bronchoalveolar lavage fluid (BAL) and lung tissue was similar for HNE and PPE as were the half-lives, 45 and 51 min, respectively, for uncomplexed, enzymatically active HNE and PPE. In BAL there was preferential binding and inactivation of HNE by the hamsters' alpha-1-protease inhibitor (a-1-PI) whereas PPE was preferentially bound by alpha-2-macroglobulin (a-2-M). This was also observed in vitro when HNE and PPE were incubated with plasma from untreated hamsters. Nevertheless, when the sum of the elastase binding capacity of a-1-PI and a-2-M was considered, hamster plasma had similar binding capacities for HNE and PPE. It is known that the enzymatic activity of elastases is inhibited by formation of a stable complex with a-1-PI. On the other hand, elastases bound to a-2-M are protected against a-1-PI inhibition but can free themselves by proteolysis and exhibit elastolytic activity. Preferential inactivation of HNE by a-1-PI may be one mechanism that accounts for the lesser emphysema-inducing potency of HNE than of PPE.  相似文献   
8.
9.
The BTE Work Simulator is used in strengthening and endurance programs providing objective information concerning a patient's progress from such programs. This study establishes normative data for grip and wrist flexion strength employing a BTE Work Simulator. For each part of this study, the right hand of 200 normal men between the ages of 30 and 40 years were tested. This study has established benchmark or reference values for the BTE Work Simulator. Normative values provide both objective data, for comparison of the patient to the general population, and long-term goals for which to strive during the rehabilitation process.  相似文献   
10.
Benzene disposition and metabolism were examined as a function of age in male C57BL/6N mice aged 3 and 18 months. Mice received a single oral dose of either 10 or 200 mg/kg 14C-benzene (approximately 25 microCi/kg). Excretion of 14C-derived benzene radioactivity (RA) was monitored in urine, feces, and as exhaled 14CO2 from 0 to 72 hr, and as exhaled unmetabolized benzene from 0 to 6 hr. At 10 mg/kg 14C-benzene, urinary elimination was the major route of excretion in both 3- and 18-month mice. Urinary excretion of 14C-derived benzene RA was significantly decreased in 18- vs. 3-month mice at 4, 6, 24, and 48 hr, while fecal excretion was significantly increased at 72 hr. Elimination of 14C-benzene as 14CO2 and unmetabolized 14C-benzene was also increased in 18- vs. 3-month mice at this dose. Hydroquinone glucuronide (HQG), phenylsulfate (PS), and muconic acid (MUC) were the major urinary metabolites at 10 mg/kg 14C-benzene in both 3- and 18-month mice, representing approximately 40, 28, and 15% of an administered dose of 14C-benzene. Smaller amounts of phenyl glucuronide (4.0%), pre-phenyl mercapturic acid (1.2%), and catechol glucuronide (0.5%) were also detected. No significant differences were found with age in the percentage of an administered dose of benzene excreted as the various metabolites at 10 mg/kg. At 200 mg/kg 14C-benzene, the total percentage of 14C-derived benzene RA eliminated in urine within 72 hr was not significantly different with age, but elimination at early time points (4, 6, and 8 hr) was significantly decreased in 18- vs. 3-month mice.(ABSTRACT TRUNCATED AT 250 WORDS)  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