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   13829篇
  免费   751篇
  国内免费   97篇
耳鼻咽喉   154篇
儿科学   330篇
妇产科学   377篇
基础医学   1871篇
口腔科学   333篇
临床医学   1368篇
内科学   2838篇
皮肤病学   524篇
神经病学   842篇
特种医学   716篇
外科学   2212篇
综合类   157篇
现状与发展   1篇
一般理论   2篇
预防医学   587篇
眼科学   274篇
药学   1062篇
中国医学   150篇
肿瘤学   879篇
  2023年   90篇
  2022年   248篇
  2021年   419篇
  2020年   197篇
  2019年   269篇
  2018年   414篇
  2017年   298篇
  2016年   345篇
  2015年   436篇
  2014年   639篇
  2013年   653篇
  2012年   1039篇
  2011年   1012篇
  2010年   605篇
  2009年   484篇
  2008年   804篇
  2007年   786篇
  2006年   741篇
  2005年   738篇
  2004年   643篇
  2003年   522篇
  2002年   492篇
  2001年   420篇
  2000年   395篇
  1999年   307篇
  1998年   126篇
  1997年   102篇
  1996年   100篇
  1995年   79篇
  1994年   72篇
  1993年   48篇
  1992年   125篇
  1991年   112篇
  1990年   107篇
  1989年   75篇
  1988年   67篇
  1987年   72篇
  1986年   54篇
  1985年   57篇
  1984年   32篇
  1983年   26篇
  1980年   25篇
  1979年   31篇
  1977年   30篇
  1976年   29篇
  1975年   26篇
  1974年   28篇
  1973年   26篇
  1972年   30篇
  1970年   23篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Aggregation inhibitory activity of minor acetophenones from Paeonia species   总被引:4,自引:0,他引:4  
Lin HC  Ding HY  Ko FN  Teng CM  Wu YC 《Planta medica》1999,65(7):595-599
Two minor acetophenones, 2,5-dihydroxy-4-methoxy-acetophenone (2) and 2,5-dihydroxy-4-methylacetophenone (7) from Paeonia species were found to selectively inhibit the aggregation of rabbit platelets induced by arachidonic acid. They were more potent than the major compound, paeonol (1), and 7 also inhibited the formation of TXA2 and PGD2 from arachidonic acid.  相似文献   
82.
Bioassay-guided fractionation of an H2O extract of the barks of Fraxinus rhynchophylla has furnished two inducible nitric oxide synthase (iNOS) inhibitory compounds, ferulaldehyde (1) and scopoletin (3) together with a coumarin, fraxidin (2). Compounds 1 and 3 showed inhibition of nitric oxide (NO) synthesis in a dose-dependent manner by murine macrophage-like RAW 264.7 cells stimulated with interferon-gamma (IFN-gamma) plus lipopolysaccharide (LPS). The inhibition of NO synthesis of 1 was reflected in the decreased amount of iNOS protein, as determined by Western blotting.  相似文献   
83.
In many Western developed countries, the incidence of stomach cancer has declined dramatically. This decrease was an extraordinary, "unplanned triumph", especially when compared to other cancers. Stomach cancer is still the most prevalent malignant tumor in Korea. Most Koreans carry Helicobacter pylori in their stomach. Thus, a new hypothesis, based on the relationship between the host and Helicobacter pylori, is presented as the carcinogenesis of human stomach cancer. The reasons for why the N-nitrosamide hypothesis should be dismissed as the etiology of stomach cancer, and why the contemporarily available principles and practice of intervention strategies to rapidly decrease the surprisingly high prevalence rate of Helicobacter pylori infection are impractical at this moment, are explained. In order to introduce an alternative provisional strategy of the "planned triumph" for the population vulnerable to stomach cancer, vitamin C is defined as an anti-inflammatory agent on the basis of the pathogenesis of Helicobacter pylori infection.  相似文献   
84.
Doppler velocimetry of the umbilical and intraplacental fetal arteries was studied by color flow mapping in 39 normal pregnancies. The systolic-diastolic ratio (S/D) and pulsatility index of the intraplacental fetal artery downstream to the umbilical artery decreased significantly with advancing gestational age, and its S/Ds were persistently lower than those of the umbilical artery. The difference in the S/D between the umbilical artery and its intraplacental downstream branches decreased with advancing gestational age and approached zero as the pregnancy progressed to term. We conclude that intraplacental fetal arteries, possibly fetal arteries in main stem villi, can be imaged by color flow mapping and that there is a significant "resistance gradient" between the intraplacental fetal artery and the umbilical artery. Intraplacental fetal artery velocimetry using color flow mapping may give further insights into the umbilical-placental circulation.  相似文献   
85.
Samples of pustules taken from 37 patients with acne (a. vulgaris, a. papulopustulosa, a. conglobata) were examined using different culture mediums for the growth of anaerobic to microaerophilic coryneforms. We identified 46 isolates of Propionibacteria which were tested according to their morphological, biochemical, serological, and phagelysotopic reactions. Three types of Propionibacteria were found: P. acnes (33), P. granulosum (11) and P. avidum (2). Nine samples showed P. acnes combined with P. avidum, four samples from patients with acne conglobata showed P. granulosum or P. avidum only. Tests from 37 patients are too limited to reach definite conclusions. We are not able to suggest any correlation between type and degree of clinical acne, and the isolated Propionibacteria. These data indicate that pustules from patients with acne of all clinical degrees can contain P. acnes as well as other anaerobic coryneforms. Therefore, other species of anaerobic bacteria, particularly those of the "propionibacteria type", should be included in any discussion about the aetiological factors of acne.  相似文献   
86.
A 71-year-old man was transferred to our institution with suspected of impending rupture of the abdominal aorta. The clinical manifestations included abdominal pain, pulsatile mass, and abdominal bruit. We made on early diagnosis of aortocaval fistula based on enhanced computed tomography and color Doppler flow imaging. Surgical repair was performed 24 hours after the onset of symptoms. At the introduction of anesthesia, cardiac arrest with high central venous pressure occurred. After resuscitation and rapid clamping of the proximal aorta, surgical closure of the fistula with graft replacement was performed successfully.  相似文献   
87.
We examined the effects of the phenothiazine derivative, chlorpromazine on thoracic aortic endothelial cell histology (14 h after LPS challenge) in a model of endotoxic shock in rats. Since excessive formation of tumor necrosis factor-alpha (TNF-alpha) and oxygen-derived free radicals contribute to endothelial injury in endotoxemia, we also evaluated the effect of the drug on the activities of antioxidant enzymes superoxide dismutase (SOD) and catalase in liver tissue in this model and tried to find out whether this possible effect was associated with a change in serum TNF-alpha levels (measured 90 min after chlorpromazine administration). Endotoxemia was induced by a single i.p. injection of lipopolysaccharide (LPS) (5 mg kg(-1) in 1.5 ml of saline; LPS from Escherichia coli serotype 055:B5, L-2880, Sigma Chemical Company). Electron microscopic evaluation of the aortas revealed that chlorpromazine (administered 30 min prior to LPS challenge), in smaller doses (3 mg kg(-1)) ameliorated the endothelial cell injury caused by LPS, whereas it caused deterioration of endothelial cell morphology in higher doses (10 and 25 mg kg(-1)). Chlorpromazine administration caused a significant reduction in serum TNF-alpha levels, which was correlated well with an increase in SOD activity in all drug doses (3, 10 and 25 mg kg(-1)). Catalase activity was increased only in the 25 mg kg(-1) chlorpromazine group.  相似文献   
88.
Seventy-eight patients (85 affected hips and 71 unaffected hips) with Legg-Calvé-Perthes disease were included in this study to evaluate the metaphyseal change in radiographs and magnetic resonance imaging (MRI) and to define the type of the metaphyseal cyst according to presence or absence of the epiphyseal involvement. The content of the metaphyseal cyst was evaluated by using T1,T2, proton, and gadolinium-enhanced T1-weighted MRI scans. Among 85 hips, there were no changes in 32 hips, marrow edema in 13 hips, false cyst with epiphyseal involvement in 28 hips, and true cyst without epiphyseal involvement in 12 hips. Granulation tissue was found in the false cysts and water-rich fibrotic tissue was found in the true cysts based on the MRI scans. The metaphyseal change in MRI scans was shown in 71% of groups 3 and 4 and in 35% of groups 1 and 2 according to the Catterall classification, and 52% of group A, 56% of group B, and 86% of group C according to the Herring classification. Of the 30 hips at the avascular stage, 33% showed metaphyseal cyst in MRI scans. Of the 53 hips at the fragmentation stage, 60% showed the metaphyseal cyst.  相似文献   
89.
To correct crooked nail deformity, which results from the partial loss of the distal phalanx, soft-tissue restoration alone is usually not enough to restore the length and shape of the nail structure. The authors treated 10 crooked nail fingertips by modified osteoplastic reconstruction, which included the elevation of the dorsally based volar skin flap and an iliac bone graft covered by an adequate skin flap. During the postoperative follow-up, the nail straightened, although not to the preinjury extent, along the restored distal phalanx with bony support. The authors' osteoplastic reconstruction, which involves the enhancement of the fingertips with composite tissues, presents a practical method for the correction of crooked nail deformity.  相似文献   
90.
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