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   424967篇
  免费   39183篇
  国内免费   28628篇
耳鼻咽喉   3267篇
儿科学   5611篇
妇产科学   5088篇
基础医学   46678篇
口腔科学   7023篇
临床医学   58630篇
内科学   58628篇
皮肤病学   4732篇
神经病学   20499篇
特种医学   15844篇
外国民族医学   247篇
外科学   39258篇
综合类   77443篇
现状与发展   97篇
一般理论   47篇
预防医学   30927篇
眼科学   11933篇
药学   46062篇
  482篇
中国医学   27008篇
肿瘤学   33274篇
  2024年   1409篇
  2023年   6062篇
  2022年   15876篇
  2021年   20347篇
  2020年   15904篇
  2019年   13142篇
  2018年   13727篇
  2017年   13099篇
  2016年   12146篇
  2015年   18655篇
  2014年   23334篇
  2013年   21602篇
  2012年   31969篇
  2011年   35668篇
  2010年   24001篇
  2009年   19600篇
  2008年   24221篇
  2007年   24076篇
  2006年   22899篇
  2005年   21738篇
  2004年   14769篇
  2003年   14156篇
  2002年   11774篇
  2001年   10023篇
  2000年   9744篇
  1999年   9676篇
  1998年   5995篇
  1997年   5755篇
  1996年   4496篇
  1995年   4185篇
  1994年   3542篇
  1993年   2298篇
  1992年   2884篇
  1991年   2505篇
  1990年   2137篇
  1989年   1876篇
  1988年   1539篇
  1987年   1426篇
  1986年   1139篇
  1985年   824篇
  1984年   478篇
  1983年   352篇
  1982年   199篇
  1981年   236篇
  1980年   153篇
  1979年   214篇
  1978年   110篇
  1977年   80篇
  1974年   78篇
  1972年   78篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
为了观察一般剂量补钙对缺氧缺血性脑病(HIE)脑细胞和红细胞内外钙变化的影响,以探讨HIE时补钙是否增加脑细胞钙超载,用HIE新生动物模型进行了实验研究,结果表明:(1)缺氧缺血时红细胞、脑细胞及脑组织出现钙积聚;(2)补钙后,血浆总钙浓度明显升高,而脑细胞、脑组织及红细胞钙积聚并未加重;(3)血浆总钙浓度与脑细胞或红细胞胞浆游离钙离子浓度无相关关系。提示:(1)HIE时钙内流可能是全身性的;(2)对HIE并低钙血症患儿吸氧后一般剂量补钙可能是安全的。  相似文献   
12.
Positron emission tomography (PET) with fluorodeoxyglucose (FDG), magnetic resonance imaging (MRI), and CT were carried out in a patient with Alzheimer's disease 16 months before he died. At autopsy, the gross appearance of the brain correlated with MRI and CT, which showed some regional atrophy. These were much less revealing than PET, which correlated with microscopic findings of neuronal loss and proliferation of glia. In areas of moderately impaired local cerebral metabolic rate of glucose, as revealed by reduced FDG uptake, there was some gliosis, primarily around the numerous senile plaques. In areas of severe metabolic impairment, there was a profound loss of neurons, extensive gliosis, and a diminished appearance of plaques. PET-FDG is a better measure of the severity of Alzheimer's disease than MRI or CT, because it reflects the degree of neuronal pathology.  相似文献   
13.
J S Li 《中华外科杂志》1989,27(10):629-33, 640
Serum aminogram changes were prospectively studied in 95 patients with enteric fistula and intraabdominal infection who was under total parenteral nutrition (TPN) therapy with Anfuming 14s. In patients with sepsis and starvation, the aminogram showed remarkably low total free amino acids before TPN therapy. In 81 survivors, free amino acids increased gradually to normal in 2 weeks after use of TPN and in 14 dead cases increased rapidly to a significantly higher peak at terminal stage. Both in survivors and nonsurvivors, phenylalanine level remained high during the study. In response to infection, proline was also elevated but to a lesser degree; the ratio of branched chain amino acid (BCAA) to aromatic amino acid (AAA) was lower than normal and the decrease of arginine was parallel to the severity of infection. We conclude that the ideal amino acids preparation for the starvated and septic patients should be high in BCAA and arginine but low in phenylalanine, administration of inappropriate exogenous amino acids in decompensated metabolic septic patients may bring about more harm than benefit, and in septic patients that the levels of serum phenylalanine and proline are elevated persistently along with the decrease of arginine level is a useful prognostic indication.  相似文献   
14.
15.
The neuroprotective effects of dizocilipine maleate (MK-801), a noncompetitive antagonist of the N-methyl-D-aspartate (NMDA) receptor/channel, were tested in the 4-vessel occlusion rat model of forebrain ischemia. Adult Wistar rats, treated intraperitoneally with MK-801 or saline using several different treatment paradigms were subjected to 5 (n = 208) or 15 (n = 62) min of severe, transient forebrain ischemia. In saline-treated animals, 15 min of ischemia (n = 13) produced extensive and consistent loss of pyramidal neurons in the CA1 zone of hippocampus. The degree and distribution of cell loss were not reduced by single dose preischemic administration of MK-801 at 1 (n = 7), 2.5 (n = 4), or 5 mg/kg (n = 8). In other animals subjected to 15 min of forebrain ischemia, multiple doses of MK-801 (5, 2.5, and 2.5 mg/kg) given immediately and at approximately 8 and 20 hr after cerebral reperfusion (n = 5) did not alter CA1 injury compared to saline-treated controls (n = 5). Five minutes of forebrain ischemia in saline-treated animals, (n = 82) resulted in significantly fewer (p less than 0.001) dead CA1 pyramidal cells and a greater variance compared to animals subjected to 15 min of ischemia. Power analysis of the preliminary saline-treated animals subjected to 5 min of ischemia (n = 22) indicated that 60 animals per group were necessary to detect a 15% difference between MK-801 and vehicle-treated groups. Multidose treatment with MK-801 (1 mg/kg) given 1 hr prior to 5 min of ischemia (n = 60) and again at approximately 8 and 16 hr after recirculation failed to attenuate hippocampal injury.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
16.
Intravenous administration of human bone marrow stromal cells (hMSCs) after middle cerebral artery occlusion (MCAo) in rats provides functional benefit. We tested the hypothesis that these functional benefits are derived in part from hMSC production of growth and trophic factors. Quantitative sandwich enzyme‐linked immunosorbent assay (ELISA) of hMSCs cultured with normal and MCAo brain extracts were performed. hMSCs cultured in supernatant derived from ischemic brain extracts increased production of brain‐derived neurotrophic factor (BDNF), nerve growth factor (NGF), vascular endothelial growth factor (VEGF) and hepatocyte growth factor (HGF). These neurotrophins and angiogenic growth factors increased in a post‐ischemia time‐dependent manner. The hMSC capacity to increase expression of growth and trophic factors may be the key to the benefit provided by transplanted hMSCs in the ischemic brain.  相似文献   
17.
We used the perfused hemicorpus preparation to measure individual rates of protein synthesis and degradation. Using fed animals, perfused either with or without insulin, muscle protein synthesis and hemicorpus protein degradation rates were similar, but myofibrillar protein degradation was clearly increased in the uremic preparations. When the animals were fasted, differences in the rates of skeletal muscle protein turnover were apparent. Uremic rats lost more wt at both 24 and 48 hr of fasting when compared to either ad libitum fed or pair-fed controls who started fasting at body wts equivalent to our uremic rats. The accelerated wt loss was accompanied by lower rates of protein synthesis, higher degradation rates, and greater net protein catabolism in our uremic rats. Alterations in body lipid content were present in uremia and correlated with the rate of protein degradation in both control and uremic rats. These data demonstrated that even in the fed state, uremia is associated with subtle alterations in skeletal muscle protein turnover. When stressed, these alterations become more pronounced. Insufficient stores of body lipids, either due to inadequate nutrition or altered metabolism, may contribute to the alterations in muscle protein turnover seen in chronic renal insufficiency.  相似文献   
18.
OBJECTIVE: To investigate the characteristics of the early stage treponema pallidum infected tissue in ear, nose, oropharynx and larynx and to raise relevance ratio of syphilis in nose and oropharynx and enhance doctor's self-protection awareness. METHODS: The histopathologic characteristics were studied by using HE staining, Warthin-Starry (W-S) staining was adopted to examine the treponema pallidum(TP) in lesion issue and its exudates smear for 12 cases biopsy tissues of suspicious syphilis. The diagnosis was confirmed by venereal disease research laboratory (VDRL), rapid plasma reagin circle test(RPR), treponema pallidum hemagglutination test(TPHA) and fluorescent treponemal antibody-absorption test (FTA-ABS). Treat with curing syphilis methods which published by nation. RESULTS: In the 12 cases mucous membrane specimen, the squamous epithelium proliferated, neutrophilic granulocyte infiltrated, within inherent membrane generous plasmacyte and lymphocyte infiltrated. W-S staining: plenty of treponema pallidum were found inside mucous membrane epithelium and exudate smear. Serology examination: 11 cases VDRL(++++), 7 cases RPR (+), 11 cases TPHA(+), 1 case FTA-ABS(+). After systemic treatment, 11 cases are clinically recovered. All patients serology become negative. CONCLUSION: W-S staining method can directly demonstrate histopathologic characteristics in early syphilis, in intrinsic membrane numerous plasmacyte infiltration. Combining with specific syphilis serology examination could increase diagnosis rate of syphilis in nose and oropharynx.  相似文献   
19.
小儿呼吸道感染是小儿科最常见的疾病,以咽炎、扁桃体炎、气管炎和肺炎多见。病原体以病毒感染为主。未经治疗有诱发心肌炎、脑炎的可能,应积极进行有效治疗。我们自2004年6月至12月应用注射用穿琥宁冻干粉剂雾化吸入治疗小儿呼吸道病毒感染58例,取得满意效果,现总结报告如下:  相似文献   
20.
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