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   1427篇
  免费   67篇
  国内免费   14篇
耳鼻咽喉   1篇
儿科学   16篇
妇产科学   10篇
基础医学   160篇
口腔科学   7篇
临床医学   89篇
内科学   380篇
皮肤病学   15篇
神经病学   200篇
特种医学   45篇
外科学   201篇
综合类   10篇
一般理论   1篇
预防医学   42篇
眼科学   26篇
药学   148篇
中国医学   9篇
肿瘤学   148篇
  2023年   11篇
  2022年   19篇
  2021年   48篇
  2020年   30篇
  2019年   29篇
  2018年   30篇
  2017年   24篇
  2016年   19篇
  2015年   24篇
  2014年   48篇
  2013年   55篇
  2012年   75篇
  2011年   61篇
  2010年   35篇
  2009年   33篇
  2008年   74篇
  2007年   73篇
  2006年   89篇
  2005年   62篇
  2004年   54篇
  2003年   77篇
  2002年   72篇
  2001年   33篇
  2000年   32篇
  1999年   38篇
  1998年   10篇
  1997年   18篇
  1996年   9篇
  1995年   14篇
  1994年   10篇
  1993年   8篇
  1992年   20篇
  1991年   29篇
  1990年   17篇
  1989年   12篇
  1988年   36篇
  1987年   22篇
  1986年   20篇
  1985年   33篇
  1984年   15篇
  1983年   8篇
  1982年   5篇
  1980年   6篇
  1978年   7篇
  1977年   9篇
  1974年   5篇
  1973年   5篇
  1971年   6篇
  1970年   6篇
  1968年   7篇
排序方式: 共有1508条查询结果,搜索用时 15 毫秒
1.
2.
METHODS: Data were obtained from a longitudinal study sample of 754 adoptees and categorized based on review of the available adoption agency, medical, and psychiatric records of the biological parents. Categorical data were analyzed using chi2 or Fisher's exact tests, as appropriate. Logistic regression analyses were used to assess the relative contribution of variables. RESULTS: There was not a statistically significant difference in the frequency or type of self-reported adult disruptive behavior, arrests, jail stays, felony arrests, or frequency of conduct disorder (CD) when inattentiveness, impulsivity, and hyperactivity were analyzed individually. The contributions of attention deficit hyperactivity disorder (ADHD) were independent and no additional increased risk for future illegal behavior was conferred by the combination of the disorders. While the effect of CD on illegal behavior was correlated with substance abuse and dependence, ADHD continued to be a significant contributor after controlling for substance abuse and dependence. CONCLUSIONS: Data indicated that ADHD and CD are related but different disorders conferring risk for adult illegal behavior or arrest. In this sample, inattention was the most common domain impaired among those with ADHD, followed closely by hyperactivity, with impulsivity reported least often among those endorsing symptoms of ADHD.  相似文献   
3.
4.
Histopathologic changes in lymph nodes were examined from ten patients with mild lymphadenopathy, a few atypical lymphocytes in their peripheral blood, skin lesions, and proviral DNA of human T-cell leukemia virus type I (HTLV-I) in their nodes. The proviral DNA of HTLV-I was detected by southern blot analysis, in situ hybridization, and/or polymerase chain reaction techniques. The lymph nodes showed preserved nodal architecture with diffuse infiltration of small to intermediate-sized lymphocytes in association with scattered transformed lymphocytes and a few immunoblast-like cells in the enlarged paracortex. The infiltrating lymphocytes were positive for CD4, but neither rearrangement nor deletion of T-cell receptors and immunoglobulin heavy chain genes was detected. Eight of ten patients received no therapy, and all patients were alive and healthy more than 5 months after the biopsies. The histologic findings resembled those of a viral infection and could be distinguished from HTLV-I associated lymphomas.  相似文献   
5.
Effects of a protein-free diet on the rat stomach   总被引:1,自引:0,他引:1  
The effects of a protein-free diet containing a mixture of free amino acids on the stomach were studied using male Wistar strain rats. In the forestomach, thickening of mucosa and hyperkeratosis appeared and papillomas frequently developed, but they did not occur in the control rats fed a semipurified diet. Mucous neck cells increased and parietal cells and chief cells decreased in the fundus. Goblet cells occurred in the antral glands, and intestinal metaplastic glands developed in the late stage of the experiment. The number of deoxyribonucleic acid-synthesizing cells in the glandular stomach was significantly higher than that of the control. Moreover, in the antrum, somatostatin-producing cells increased in the early stage and gastrin-producing cells decreased in the late stage. These results suggest that dietary protein might play a crucial role in the differentiation of gastric epithelium and the development of intestinal metaplasia in the stomach.  相似文献   
6.
Effects of suramin, a polysulfonated naphthylurea compound, on metastatic ability, proliferation, and production of plasminogen activators and plasminogen activator inhibitors were studied using the highly metastatic human renal cell carcinoma cell line, SN12C-PM6. After renal subscapular implantation of tumor cells in nude mice, suramin significantly inhibited metastasis of tumor cells to the lungs and liver. In vitro growth of tumour cells was inhibited by suramin in a dose-dependent manner, at relatively low doses (ID50 = 105 µg/ml). Plasminogen activator inhibitor type 2 (PAI-2) production by tumor cells was enhanced by suramin (100 µg/ml), whereas urokinase-type plasminogen activator (uPA) production was suppressed. Thus, the increase in PAI-2 and the decrease in uPA production correlated with the inhibitory effects on tumour growth and metastasis by suramin. Therefore suramin may be beneficial for the treatment of patients with an early stage of renal cancer with potential risk of metastasis.  相似文献   
7.
The cytokine interleukin-15 (IL-15) has been demonstrated to have anabolic effects in cell culture systems. We tested the hypothesis that IL-15 is predominantly expressed by type 2 skeletal muscle fibres, and that resistance exercise regulates IL-15 expression in muscle. Triceps brachii, vastus lateralis quadriceps and soleus muscle biopsies were obtained from normally physically active, healthy, young male volunteers ( n = 14), because these muscles are characterized by having different fibre-type compositions. In addition, healthy, normally physically active male subjects ( n = 8) not involved in any kind of resistance exercise underwent a heavy resistance exercise protocol that stimulated the vastus lateralis muscle and biopsies were obtained from this muscle pre-exercise as well as 6, 24 and 48 h post-exercise. IL-15 mRNA levels were twofold higher in the triceps (type 2 fibre dominance) compared with the soleus muscle (type 1 fibre dominance), but Western blotting and immunohistochemistry revealed that muscle IL-15 protein content did not differ between triceps brachii, quadriceps and soleus muscles. Following resistance exercise, IL-15 mRNA levels were up-regulated twofold at 24 h of recovery without any changes in muscle IL-15 protein content or plasma IL-15 at any of the investigated time points. In conclusion, IL-15 mRNA level is enhanced in skeletal muscles dominated by type 2 fibres and resistance exercise induces increased muscular IL-15 mRNA levels. IL-15 mRNA levels in skeletal muscle were not paralleled by similar changes in muscular IL-15 protein expression suggesting that muscle IL-15 may exist in a translationally inactive pool.  相似文献   
8.
This report describes the autopsy findings in a 62-year-old woman who died of pneumonia and disseminated necrotizing encephalopathy following intrathecal methotrexate (MTX) therapy for meningeal infiltration of lymphoma cells. Radiation therapy was not given. An interesting pathological finding was exudation of fibrin around the small vessels in the demyelinated foci, suggesting increased vascular permeability. This observation and analysis of previous reports of similar cases suggest that primary vascular injury, probably due to the direct effect of MTX, may be involved in the pathogenesis of MTX-related disseminated necrotizing encephalopathy.  相似文献   
9.
Complementary DNAs to the 5 proximal region of the dengue virus type 3 RNA were cloned into bacterial plasmids and the nucleotide sequence of 3,000 bases from the 5 terminus of the genome were determined by DNA and RNA sequencing methods using dideoxy chain-termination reactions. Comparison of the nucleotide sequence thus obtained with those of other flavivirus genomes revealed significant homology existing in nucleotide sequence of the flavivirus genomes. When we compared amino acid sequence deduced from the nucleotide sequence with those of other flaviviruses, this genome region was found to include sequences encoding three viral structural proteins C, M, and E and a part of the viral nonstructural protein NS1 in this order in addition to the 5-noncoding sequence. The characteristics and functions of these proteins were discussed based on the deduced amino acid sequences and their hydrophobic profiles. The genetic relationship of flaviviruses was also discussed based on the genetic variation observed in their genomes.  相似文献   
10.
Summary TheERG10 gene specific toS. uvarum, a brewing yeast, has been cloned by complementation of anS. cerevisiae erg10 mutant.S. uvarum contains two differentERG10 genes. One of these is similar to theS. cerevisiae ERG10 gene; they are structurally different, but functionally homologous. The clonedERG10 gene has been located on chromosome XVI, and we have shown that it is allelic to the previously isolatedtsm0115 mutants. Northern blot and sequence analysis indicate that theERG10 gene is highly expressed, and biochemical and genetic evidence show that it encodes the cytoplasmic acetoacetyl CoA thiolase.  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