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   3265篇
  免费   151篇
  国内免费   16篇
耳鼻咽喉   59篇
儿科学   70篇
妇产科学   16篇
基础医学   284篇
口腔科学   85篇
临床医学   186篇
内科学   829篇
皮肤病学   86篇
神经病学   153篇
特种医学   226篇
外科学   715篇
综合类   16篇
预防医学   80篇
眼科学   74篇
药学   167篇
中国医学   4篇
肿瘤学   382篇
  2023年   23篇
  2022年   38篇
  2021年   57篇
  2020年   36篇
  2019年   62篇
  2018年   77篇
  2017年   57篇
  2016年   64篇
  2015年   55篇
  2014年   68篇
  2013年   92篇
  2012年   144篇
  2011年   159篇
  2010年   94篇
  2009年   86篇
  2008年   155篇
  2007年   159篇
  2006年   153篇
  2005年   184篇
  2004年   186篇
  2003年   149篇
  2002年   159篇
  2001年   113篇
  2000年   115篇
  1999年   112篇
  1998年   37篇
  1997年   35篇
  1996年   38篇
  1995年   36篇
  1994年   21篇
  1993年   23篇
  1992年   71篇
  1991年   51篇
  1990年   52篇
  1989年   55篇
  1988年   70篇
  1987年   48篇
  1986年   51篇
  1985年   37篇
  1984年   28篇
  1983年   17篇
  1982年   11篇
  1981年   14篇
  1979年   19篇
  1978年   15篇
  1977年   17篇
  1976年   10篇
  1974年   12篇
  1972年   11篇
  1967年   7篇
排序方式: 共有3432条查询结果,搜索用时 15 毫秒
101.
102.
BACKGROUND: The prognostic significance of the leukocyte subsets in peripheral blood has not yet been investigated in hepatocellular carcinoma patients. We sought to clarify the prognostic value of preoperative peripheral blood leukocyte subset counts, especially the absolute monocyte count, in HCC patients who have undergone hepatic resection. METHODS: We retrospectively examined the relation between the preoperative absolute number of peripheral monocytes and clinicopathologic factors or long-term prognosis in 198 patients with hepatocellular carcinoma who underwent curative resection. RESULTS: Univariate analysis indicated a significantly worse 5-year disease-free survival rate in patients with a peripheral blood monocyte count > 300/mm(3) (14.8%) than in patients with a count < or = 300/mm(3) (29.2%). There were no significant differences between patients in disease-free survival based on the lymphocyte or neutrophil count. According to multivariate analysis, preoperative peripheral blood monocyte count > 300/mm(3), alpha-fetoprotein level > 100 ng/mL, aspartate aminotransferase level > 100 IU/mL, and presence of microvascular invasion were independent risk factors for disease-free survival of less than 5 years. The peripheral blood monocyte count was higher in patients of male sex or those with a noncirrhotic liver, microvascular invasion, major hepatic resection, older age (>65 years), large tumor (> or =50 mm), or increased platelet count (>100,000/mm(3)) than in patients without these characteristics. CONCLUSIONS: Our findings indicate that the preoperative absolute count (>300/mm(3)) of peripheral blood monocytes may be related to tumor progression and that it is an independent risk factor for recurrence of hepatocellular carcinoma after resection. Postoperative adjuvant chemotherapy might be necessary in patients with elevation of the preoperative absolute count of peripheral blood monocytes.  相似文献   
103.
104.
We experienced general anesthesia of two patients with cerebral palsy presupposed to have difficulties in tracheal intubation by reason of scoliosis. Case 1 is a 26-year-old woman. Chest X-ray photography and respiratory sounds in both pulmonary areas indicated neither airway stricture nor respiratory distress, but severe scoliosis presupposed difficult tracheal intubation. However, under the impression of possible intubation obtained by preoperative laryngoscopy, orotracheal intubation was tried with rapid induction. Epiglottis deviation to the left noted upon developing larynx made the glottis direct invisible, but some compression of cricoid from outside barely succeeded in intubation. The fixation of the endotracheal tube found much difficulties in its proper positioning so as to make stethoscopy uniform in both pulmonary areas, but trial rotations of the tube both in various directions and at various depths barely managed to find a position of uniform stethoscopy in both pulmonary areas, in which position the tube was fixed as proper positioning. Anesthesia was performed by nitrous oxide.oxygen.halothane; peroperative hemodynamics remained stable and arterial blood gas analysis presented no problems. Case II is a 16-year-old man. Resting respiration presented stridor and chest X-ray photography indicated scoliosis and laryngeal stricture. Patient's lack in the degree of cooperation made laryngoscopy impossible. Thus, in view of a high possibility of difficult tracheal intubation, orotracheal intubation was tried under the control of spontaneous respiration. While the intubation was being carried out by means of a stylet without developing larynx, severe bronchostriction was palpable at the point when the tube barely passed through the glottis, making the intubation impossible. However, the tube barely managed to be inserted while rotating with the stylet being extracted. Anesthesia was carried out by nitrous oxide.oxygen.halothane; peroperative hemodynamics underwent no remarkable change and arterial blood gas analysis presented no problems.  相似文献   
105.
106.
107.
The Shumiya cataract rat (SCR) is a hereditary cataractous strain. It is thought that the continuous occurrence of poorly differentiated epithelial cells at the bow area of the lens forms the pathophysiological basis for cataract formation in SCRs. In this study, we attempted to identify the genes associated with cataract formation in SCRs by positional cloning. Genetic linkage analysis revealed the presence of a major cataract locus on chromosome 20 as well as a locus on chromosome 15 that partially suppressed cataract onset. Hypomorphic mutations were identified in genes for lanosterol synthase (Lss) on chromosome 20 and farnesyl diphosphate farnesyl transferase 1 (Fdft1) on chromosome 15, both of which function in the cholesterol biosynthesis pathway. A null mutation for Lss was also identified. Cataract onset was associated with the specific combination of Lss and Fdft1 mutant alleles that decreased cholesterol levels in cataractous lenses to about 57% of normal. Thus, cholesterol insufficiency may underlie the deficient proliferation of lens epithelial cells in SCRs, which results in the loss of homeostatic epithelial cell control of the underlying fiber cells and eventually leads to cataractogenesis. These findings may have some relevance to other types of cataracts, inborn defects of cholesterol synthesis, and the effects of cholesterol-lowering medication.  相似文献   
108.
109.
Phenotypic characteristics of vascular endothelial cells of the colonic mucosa in patients with ulcerative colitis and healthy controls were studied with immunoperoxidase staining by light and electron microscopy. The cells could be classified into two groups according to their phenotypes; one was positive for von Willebrand factor and the other had an antigen detected by a monoclonal antibody, OKM5. The endothelial cells positive for von Willebrand factor were usually in relatively large blood vessels, and OKM5-positive cells were mostly located in small capillaries along the glandular epithelium. OKM5-positive endothelial cells also expressed HLA-DR and interleukin-1 (IL-1). In patients with ulcerative colitis, OKM5-positive endothelial cells and spindle-shaped cells that might be precursors of endothelial cells were more numerous in the lamina propria than in the other subjects. Thus, OKM5-positive endothelial cells may be important as antigen-presenting cells and immunoregulatory cells in the intramucosal immune system. Furthermore, colonic epithelial cells in patients with ulcerative colitis synthesized HLA-DR and IL-1, and may have a close relation to immune responses, such as antigen processing and presentation to immunocompetent cells. It was suggested that these cells have a close relation to the pathogenesis of the impaired immune responses in situ in ulcerative colitis.  相似文献   
110.

Objective

This study measured the modulation of conditioned (femoral nerve, paired-stimuli) and unconditioned soleus H-reflexes in young and elderly subjects when changing weight-bearing (WB) requirements and body position.

Methods

Conditioned and unconditioned H-reflexes were examined in 14 elderly subjects and 11 young subjects during six different WB conditions: (1) lying supine with no WB, (2) supine position inclined by 30° with 50% WB, (3) standing with 50%, (4) 75%, (5) 100% and (6) 125% WB.

Results

The elderly subjects had consistently higher background soleus EMG activity across the WB conditions compared to the young. Femoral nerve conditioning caused facilitation of the H-reflex that changed across WB conditions in the young subjects, but not in the elderly subjects. Finally, elderly subjects had less depression with paired-stimulation (PRD) across WB conditions, which was not observed in the young subjects.

Conclusions

The elderly may have more direct activation of motoneurons from descending pathways, coupled with less segmental spinal control of inhibitory interneurons, as evidenced by the increased background soleus activity, H/M-max ratios and the lack of modulatory control observed when conditioning the H-reflex.

Significance

There was an age-specific response from descending and segmental pathways during conditions that involved either different WB requirements or changes in body position.  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