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   37660篇
  免费   2268篇
  国内免费   202篇
耳鼻咽喉   444篇
儿科学   1159篇
妇产科学   1021篇
基础医学   3757篇
口腔科学   1222篇
临床医学   3291篇
内科学   8112篇
皮肤病学   680篇
神经病学   2271篇
特种医学   1368篇
外国民族医学   4篇
外科学   6874篇
综合类   859篇
现状与发展   3篇
一般理论   27篇
预防医学   2581篇
眼科学   1385篇
药学   2892篇
  1篇
中国医学   283篇
肿瘤学   1896篇
  2024年   39篇
  2023年   416篇
  2022年   1059篇
  2021年   1660篇
  2020年   1005篇
  2019年   1285篇
  2018年   1588篇
  2017年   1155篇
  2016年   1247篇
  2015年   1347篇
  2014年   1709篇
  2013年   2070篇
  2012年   3133篇
  2011年   3037篇
  2010年   1723篇
  2009年   1481篇
  2008年   2250篇
  2007年   2326篇
  2006年   2039篇
  2005年   1805篇
  2004年   1633篇
  2003年   1372篇
  2002年   1194篇
  2001年   378篇
  2000年   327篇
  1999年   293篇
  1998年   203篇
  1997年   138篇
  1996年   146篇
  1995年   110篇
  1994年   100篇
  1993年   77篇
  1992年   152篇
  1991年   164篇
  1990年   134篇
  1989年   130篇
  1988年   110篇
  1987年   99篇
  1986年   94篇
  1985年   125篇
  1984年   85篇
  1983年   58篇
  1982年   54篇
  1981年   55篇
  1980年   45篇
  1979年   54篇
  1978年   46篇
  1976年   40篇
  1975年   40篇
  1974年   43篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Aim: To investigate the clinico‐pathological profile and stage of disease at presentation of patients with carcinoma of the gallbladder diagnosed during 1992–2006 in Iran. Methods: During this study period 34 consecutive patients with gallbladder carcinoma were identified using a pathology‐based tumor database. The data extracted for each study patient included their gender, age at diagnosis, signs and symptoms, presence of gallstones and histopathological pattern of the gallbladder carcinoma and the UICC/AJCC TNM staging system was used for labeling the stages of the disease. Results: The median age of the 34 patients studied was 69.50 with most between 61 and 70 years of age. The age range of the men was between 53 and 80 years with a median age of 71.50 years and that of the women was between 33 and 79 years with a median age of 68.50 years. The most common symptom was pain in the right hypochondrium. More women had gallstones (15/34) than men (3/10). Adenocarcinoma was the most common histopathological type (91.18%) with the commonest subtype being papillary (47.06%). Eighteen patients had stage IB and stage IIA (52.94%) carcinomas whereas stages IIB and III were observed in six (17.6%) and seven cases (20.6%), respectively. Only three cases (8.82%) were seen in stage IV. The follow up of gall bladder carcinoma (GBC) patients in this study ranged from 6 to 60 months. However, there was a progressive reduction of patients attending follow‐up oncology clinic, particularly by those who had stages III and IV of the disease. Conclusion: Most patients (52.94%) presented with early disease (stage IB and IIA) which carries a good prognosis. Early detection of GBC and a national consensus for the evidence‐based management of GBC in Iran should be the major components of a strategy aimed at improving therapeutic outcome.  相似文献   
52.
53.
54.
55.
56.
Background: The cardiotoxic mechanism of local anesthetics may include interruption of cardiac sympathetic reflexes. The authors undertook this investigation to determine if clinically relevant concentrations of bupivacaine and levobupivacaine interfere with exocytotic norepinephrine release from cardiac sympathetic nerve endings.

Methods: Rat atria were prepared for measurements of twitch contractile force and 3[H]-norepinephrine release. After nerve endings were loaded with 3[H]-norepinephrine, the tissue was electrically stimulated in 5-min episodes during 10 10-min sampling periods. After each period, a sample of bath fluid was analyzed for radioactivity and 3[H]-norepinephrine release was expressed as a fraction of tissue counts. Atria were exposed to buffer alone during sampling periods 1 and 2 (S1 and S2). Control atria received saline (100 [mu]l each, n = 6 atria) in S3-S10. Experimental groups (n = 6 per group) received either bupivacaine or levobupivacaine at concentrations (in [mu]M) of 5 (S3-S4), 10 (S5-S6), 30 (S7-S8), and 100 (S9-S10).

Results: Bupivacaine and levobupivacaine decreased stimulation-evoked fractional 3[H]-norepinephrine release with inhibitory concentration 50% values of 5.1 +/- 0.5 and 6.1 +/- 1.3 [mu]m. The inhibitory effect of both local anesthetics (~70%) approached that of tetrodotoxin. Local anesthetics abolished the twitch contractions of atria with inhibitory concentration 50% values of 12.6 +/- 5.0 [mu]m (bupivacaine) and 15.7 +/- 3.9 [mu]m (levobupivacaine). In separate experiments, tetrodotoxin inhibited twitch contractile force by only 30%.  相似文献   

57.
We hypothesized that increased ambient concentrations of metals, as a consequence of escalating urbanization and industrialization of the Gulf region will respond in increased contamination of edible fish species. In this study, we report concentrations of chromium, manganese, cobalt, copper, zinc, arsenic, cadmium, mercury and lead in meat and liver of wild Red-spot emperor (Lethrinus lentjan) from three sampling points at the UAE coast. Analysis was performed by the ICP-MS/microwave digestion. Our study has shown that meat and liver metal content was significantly higher in areas with higher industrial activity, although metal values did not exceed permitted levels of fish for human consumption.  相似文献   
58.
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   
59.
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   
60.
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