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   37801篇
  免费   2170篇
  国内免费   201篇
耳鼻咽喉   427篇
儿科学   1186篇
妇产科学   1004篇
基础医学   3805篇
口腔科学   1214篇
临床医学   3323篇
内科学   8148篇
皮肤病学   686篇
神经病学   2247篇
特种医学   1341篇
外国民族医学   4篇
外科学   6919篇
综合类   864篇
现状与发展   3篇
一般理论   27篇
预防医学   2538篇
眼科学   1364篇
药学   2907篇
  1篇
中国医学   269篇
肿瘤学   1895篇
  2024年   39篇
  2023年   417篇
  2022年   1070篇
  2021年   1670篇
  2020年   1004篇
  2019年   1275篇
  2018年   1591篇
  2017年   1153篇
  2016年   1256篇
  2015年   1357篇
  2014年   1710篇
  2013年   2077篇
  2012年   3159篇
  2011年   3038篇
  2010年   1730篇
  2009年   1474篇
  2008年   2267篇
  2007年   2333篇
  2006年   2060篇
  2005年   1819篇
  2004年   1656篇
  2003年   1382篇
  2002年   1201篇
  2001年   382篇
  2000年   317篇
  1999年   288篇
  1998年   200篇
  1997年   133篇
  1996年   143篇
  1995年   110篇
  1994年   96篇
  1993年   77篇
  1992年   151篇
  1991年   162篇
  1990年   130篇
  1989年   127篇
  1988年   105篇
  1987年   102篇
  1986年   93篇
  1985年   118篇
  1984年   81篇
  1983年   52篇
  1982年   54篇
  1981年   56篇
  1980年   42篇
  1979年   53篇
  1978年   42篇
  1975年   36篇
  1974年   37篇
  1973年   37篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
Adult male Fisher 344 rats (8-10 wk old) were dosed ip with 1.75 mg/kg body weight of triethyllead chloride (TEL) for 5 consecutive days. Rats were sacrificed 1, 7, or 21 d after the last injection. The rate of lipid peroxidation was significantly elevated in frontal cortex at all three time points assayed (1, 7, or 21 d). However, hippocampal and cerebellar membranes showed no changes in peroxidative capacity at these time points. In order to determine whether cortical membrane damage was reflected in alteration of a restricted protein population, a series of high-affinity receptor binding sites was determined in cortical membranes derived from treated rats 7 d after the last injection of triethyllead. The rate of lipid peroxidation was significantly increased in the frontal cortex of triethyllead treated rats; however, no changes in the binding of [3H]spiroperidol, [3H]quinuclidinyl benzilate, and [3H]benzodiazepine were seen in animals exposed to triethyllead. The cortical wet weight, protein content, and cell number were also unchanged by TEL treatment, reflecting an absence of gross damage.  相似文献   
22.
BACKGROUND: Optimal feeding practice in the first year of life is crucial for the survival and health of infants, and has long-term consequences in later life. However, non-optimal feeding practices exist widely. The present study aims to explore various constraints to optimal feeding practices in the first year of life of infants in urban areas of Beijing, China. METHODS: A cross-sectional study was conducted in urban areas of Beijing from 4 July to 20 August, 1998. Two hundred and fifty-one mothers of infants aged 6-12 months were chosen from six child health centers in three different urban districts in Beijing. A self-administered structured questionnaire was used to collect data regarding feeding practices and potentially related factors. RESULTS: Feeding practice for most of the infants was in accordance with the national and international recommendations. However, the rate of incidence of exclusive breast-feeding at 3 months of age was lower than that recommended by the World Health Organisation (WHO) (55.8%), and the introduction of solid/semisolid food before 4 months of age was found in approximately 19.3% of the infants. Cow's milk was given to 21.2% of infants from 6 months of age as the sole source of milk or as a supplement. Maternal education level (OR = 2.44, 95% CI: 1.42-4.19, P < 0.05), employment (OR = 2.05, 95% CI: 1.13-3.74, P < 0.05) and antenatal nonexclusive breast-feeding plans (OR = 4.10, 95% CI: 2.24-7.50, P < 0.001) were found to be correlated to inappropriate feeding practices. CONCLUSIONS: The feeding practices for most of the urban infants was found to be in accordance with the Chinese government and WHO recommendations; however, non-optimal feeding practices presenting as the early cessation of breast-feeding and the introduction of solid/semisolid foods existed. Information regarding optimal feeding practices should be disseminated to mothers and medical professionals in China, to ensure optimal infant health.  相似文献   
23.
24.
AIM: To evaluate the effects of oral continuous 17beta-estradiol plus norethisterone acetate (E2/NETA) replacement therapy on abdominal subcutaneous fat, serum leptin level (SLL) and body composition in postmenopausal women. MATERIALS AND METHODS: A 6-month, prospective, randomized, double-blind and placebo-controlled study was conducted. Forty-three healthy naturally postmenopausal women aged 43-65 years were randomly assigned to receive E2/NETA (2 mg E2 plus 1 mg NETA, n = 22) or placebo (n = 21). Fasting SLL by enzyme-linked immunosorbent assay, subcutaneous abdominal fat thickness (STh) by ultrasound and the anthropometric indices of body weight (BW), body mass index (BMI), waist and hip circumference (WC, HC) and waist-to-hip ratio (WHR) were recorded at the beginning and the end of the study. RESULTS: After 6 months of therapy, BW and SLL increased in the placebo group (p = 0.043 and 0.033, respectively). WC, HC and STh decreased significantly in the E2/NETA group (p = 0.002, 0.006 and 0.000, respectively) and they were also significantly lower in women receiving E2/NETA than in women taking placebo (p = 0.000, 0.034 and 0.000, respectively). At baseline, SLL and STh were positively correlated with all anthropometric indices except WHR. CONCLUSION: Oral continuous combined regimen of E2/NETA significantly reduced central fat accumulation as assessed by WC and STh, and attenuated the increase in SLL. The observed changes in SLL were highly and positively related to changes in STh. The oral continuous combined E2/NETA regimen appears to have protective effects on cardiovascular function and probably on metabolic diseases by its slimming effect upon WC in postmenopausal women.  相似文献   
25.
26.
The effects and the mechanism of natural honey on absolute ethanol-induced gastric lesions were studied in rats. Drugs and/or honey were administered subcutaneously or orally to 48-h fasted animals at different time intervals before oral administration of ethanol (0.5 ml/100 g). Mucosal damage and pH were measured 1 h later. Honey afforded protection against gastric damage and reversed the changes in pH induced by ethanol. The effects of honey were dose- and time-dependent. Thus, pretreatment with honey (1.25 g/kg) 30 min before ethanol provided more than 80% protection. On the other hand, administration of honey simultaneously with or 5 min after ethanol failed to offer protection. The cyclooxygenase inhibitor indomethacin (IND) did not alter the protective effects when given before or after honey. The protective effects of honey could be reversed by treatment with the sulfhydryl (SH) blocker N-ethylmaleimide (NEM). Combined IND and NEM treatment caused greater reduction of the protective effects, but the values were not significantly different from those obtained with NEM alone. Thus, the gastroprotective effects of honey appeared to be mediated through SH-sensitive processes. Furthermore, the protective effects were supported by both macroscopic and microscopic findings. It is suggested that honey may be used clinically in preventing/reducing ethanol-induced gastric lesions in humans.  相似文献   
27.
1. The effects of graded doses of the α2-adrenoceptor agonists clonidine, tizanidine and BHT-920, and the α2-adrenoceptor antagonists yohimbine and idazoxan, on gastrointestinal transit were investigated in mice using the charcoal meal test. 2. The agonists produced significant and dose-dependent decreases in gastrointestinal transit, and the antagonists produced the opposite effect. In affecting the gastrointestinal transit, clonidine (1 mg/kg) was as effective as tizanidine (12 mg/kg) and BHT-920 (40 mg/kg), while yohimbine (2 mg/kg) was as effective as idazoxan (1 mg/kg). 3. Morphine (2, 4 and 8 mg/kg) significantly inhibited gastrointestinal transit. This effect was significantly reversed by the co-administration of yohimbine (2 mg/kg) and idazoxan (1 mg/kg). 4. The acute administration of glucose (5.04 g/kg, i.p.) potentiated the inhibition of gastrointestinal transit produced by clonidine (1 mg/kg) and BHT-920 (40 mg/kg). Glucose treatment, however, had no significant effect on the increase in gastrointestinal transit induced by yohimbine (2 mg/kg) or idazoxan (1 mg/kg). 5. Castor oil (0.25 mL/mouse, orally) induced diarrhoea in saline-treated animals within about 45 min. Clonidine (1 mg/kg), tizanidine (12 mg/kg) and BHT-920 (40 mg/kg) delayed the occurrence of diarrhoea to 2.1, 1.2 and 1.4 h, respectively.  相似文献   
28.
The authors present the results of a transmission electron-microscopic study performed on a tissue sample obtained by an intraocular fine-needle aspiration biopsy in a case of retinoma. The ultrastructural study showed that the tumor was composed mainly of granular osmiophilic material which contained some tumor cells. These cells showed peculiar ultrastructural characteristics, which demonstrated their neural character, and appeared in different degenerative stages. Apparently, this is the first case in whom ultrastructural technique have been applied to study an intraocular tumor sample obtained by intraocular fine-needle aspiration biopsy, and the first case of retinoma studied by such a diagnostic approach.  相似文献   
29.
Duodenogastric reflux (DGR) has been implicated in several disease processes. The present study was carried out to document the incidence and evaluate the clinical significance of DGR after choledochoduodenostomy (CDD). A total of 13 patients who had undergone cholecystectomy with a standard side-to-side CDD for choledocholithiasis or chronic pancreatitis were studied by symptom evaluation, scintigraphy, endoscopy, and gastric mucosal histology at least 6 months after surgery. The scintigraphic findings were then compared with those of 10 patients who had undergone cholecystectomy alone. Only two patients (15%) had mild dyspeptic symptoms. The incidence of DGR after CDD was 69% compared to 20% in the cholecystectomy alone group (P < 0.05). In the majority of patients the DGR was only mild to moderate and the severity correlated well with the degree of endoscopic gastritis, but not with the clinical symptoms or histological findings. These results indicate that while CDD is associated with a high incidence of DGR, its occurrence does not produce significant clinical symptoms.  相似文献   
30.
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