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   63185篇
  免费   5487篇
  国内免费   2606篇
耳鼻咽喉   693篇
儿科学   1569篇
妇产科学   1143篇
基础医学   6372篇
口腔科学   1180篇
临床医学   5923篇
内科学   5814篇
皮肤病学   789篇
神经病学   2154篇
特种医学   3476篇
外国民族医学   52篇
外科学   7799篇
综合类   10602篇
现状与发展   19篇
预防医学   1868篇
眼科学   608篇
药学   4922篇
  48篇
中国医学   1937篇
肿瘤学   14310篇
  2024年   170篇
  2023年   993篇
  2022年   2107篇
  2021年   2767篇
  2020年   2201篇
  2019年   2001篇
  2018年   1869篇
  2017年   2101篇
  2016年   2348篇
  2015年   2528篇
  2014年   3857篇
  2013年   3929篇
  2012年   3475篇
  2011年   3892篇
  2010年   3140篇
  2009年   3192篇
  2008年   3196篇
  2007年   3438篇
  2006年   3065篇
  2005年   2731篇
  2004年   2362篇
  2003年   1986篇
  2002年   1837篇
  2001年   1650篇
  2000年   1358篇
  1999年   1230篇
  1998年   1054篇
  1997年   975篇
  1996年   852篇
  1995年   761篇
  1994年   646篇
  1993年   508篇
  1992年   414篇
  1991年   347篇
  1990年   271篇
  1989年   263篇
  1988年   257篇
  1987年   216篇
  1986年   159篇
  1985年   207篇
  1984年   188篇
  1983年   114篇
  1982年   148篇
  1981年   125篇
  1980年   84篇
  1979年   86篇
  1978年   60篇
  1977年   43篇
  1976年   37篇
  1975年   15篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Summary We report a case of a third ventricular neuroblastoma (neurocytoma) in a 66 year old man. A stereotactic needly biopsy was performed to obtain a tissue diagnosis and was followed by total resection. We elected not to give radiation or chemotherapy and to follow the patient closely with serial CT scans. Presently, 48 months postoperatively, the patient is free of tumor by head CT scan and able to live independently. We reviewed the literature of primary cerebral neuroblastomas/neurocytomas occurring in adults (15 years of age) and found 32 cases. Our patient is the oldest of this group with a mean age of 32 ± 14 years (S.D.). The location of the 33 neoplasms was intraventricular in 17 cases (52%) and intraparenchymal in 16 cases. The male to female ratio was 2: 1. Of the 17 patients having a minimal follow-up period of 5 months (mean 51 months), five developed recurrences after 5 to 144 months (mean 50 months) compared to 12 patients without recurrence after a 6- to 72-month follow-up period (mean 52 months). Recurrences occurred statistically significantly more often in parenchymal neuroblastomas/neurocytomas than in intraventricular tumor locations.  相似文献   
92.
Summary Up-to-date unsatisfactory results obtained in multimodality treatments of malignant glioma have prompted the research of new therapeutic modalities with unconventional modes of action. Lonidamine (LND) is a drug which reduces aerobic glycolytic activity in both human and experimental tumors. This effect mainly depends on the inhibition of mitochondrially-bound hexokinase (HK) which is present in large amounts in malignant cells. A Phase II study was conducted on patients with recurrent glioma; 12 patients were admitted to the study. Clinical side effects were moderate, necessitating a reduction of the dosage in only 1 case. The objective results were evaluated according to the indications of Levin. 2 responders and 3 cases of stable disease were observed out of 10 evaluable patients. The potential value of this new drug is discussed.  相似文献   
93.
To determine the value of the usually given urgent palliative radiotherapy in paraplegic patients with epidural compression from metastatic tumor, 20 consecutive cases treated between 1981 and 1986 were retrospectively analyzed. Bronchogenic and prostatic carcinoma were the more common extraspinal sources of metastasis. Epidural metastasis involved the thoracic spine in most cases. The onset of neurological symptomatology was frequently within two weeks prior to hospitalization. The majority of the subjects received at least 3000 cGy given in 10 to 15 fractions. Symptomatic (pain relief) response rate was 78 (7/9) percent. The observed period of survival averaged 2.5 months after treatment. This study reaffirmed the little chance for recovery of lost limb(s) motor function. None of the patients (most of whom were paraplegic from two to 90 days pre-irradiation) became ambulatory including the two in whom irradiation was administered within 24 hours from the onset of paraplegia.  相似文献   
94.
Insulin-dependent diabetes mellitus (IDDM) and Graves' disease (GD) are autoimmune endocrinopathies and associated with distinct HLA-DR and -DQ alleles as well as several tumor necrosis factor a (TNF-α) and β (TNF-β) alleles. TNF-α and TNF-β interact with TNF receptor (TNF-R), of which two subtypes have been described: TNF-R1 and TNF-R2. We investigated TNF-R2 alleles in 90 patients with IDDM, 101 with GD and 70 healthy controls. Genomic DNA was amplified with specific flanking primers for the untranslated 3 region of TNF-R2. SSCP analysis revealed two alleles by different fragment patterns: TNF-R2*1 and TNF-R2*2. Patients with IDDM or Graves' disease and controls did not differ significantly: TNF-R2*1/*1:IDDM(8%)/GD(2%)/KO(4%); TNF-R2*2/*2:IDDM(34%)/GD(48%)/KO(42%), heterozygosity TNF-R2*1/*2:IDDM(58%)/GD(50%)/KO(54%) (IDDM vs KO: P =0.46, χ2=1.57; GD vs KO: P =0.59, χ2=1.05). In conclusion, the studied polymorphism of TNF-R2 was associated with neither IDDM nor GD in a German population.  相似文献   
95.
The current knowledge of the distribution of the mouse mammary tumor virus (MMTV) proviral genomes and the mechanism of mammary tumorigenesis by MMTV in mice, with the main emphasis on Asian feral mice, is reviewed. The relevant earlier discoveries on the mode of MMTV transmission are summarized to provide an outline of the biology of MMTV. Finally, the viral etiology of human breast cancer will be discussed.  相似文献   
96.
Summary: Solid tumor therapy with chemotherapeutics greatly depends on the efficiency with which drugs are delivered to tumor cells. The typical characteristics of the tumor physiology promote but also appose accumulation of blood-borne agents. The leaky tumor vasculature allows easy passage of drugs. However, the disorganized vasculature causes heterogeneous blood flow, and together with the often-elevated interstitial fluid pressure, this state results in poor intratumoral drug levels and failure of treatment. Manipulation of the tumor vasculature could overcome these barriers and promote drug delivery. Targeting the vasculature has several advantages. The endothelial lining is readily accessible and the first to be encountered after systemic injection. Second, endothelial cells tend to be more stable than tumor cells and thus less likely to develop resistance to therapy. Third, targeting the tumor vasculature can have dual effects: (i) manipulation of the vasculature can enhance concomitant chemotherapy, and (ii) subsequent destruction of the vasculature can help to kill the tumor. In particular, tumor necrosis factor α is studied. Its action on solid tumors, both directly through tumor cell killing and destruction of the tumor vasculature and indirectly through manipulation of the tumor physiology, is complex. Understanding the mechanism of TNF and agents with comparable action on solid tumors is an important focus to further develop combination immunotherapy strategies.  相似文献   
97.
甲酰肽受体家族受体与恶性肿瘤   总被引:1,自引:0,他引:1  
甲酰肽受体家族受体包括甲酰肽受体(FPR)、类甲酰肽受体1和类甲酰肽受体2是主要表达在吞噬细胞表面的一类七次跨膜、G蛋白偶联受体。这些受体被相应的激动剂激活后,能活化吞噬细胞,引起细胞的趋化移动和炎症介质的释放等生物学效应,从而在天然免疫和炎症反应中发挥重要作用。近年来,人们发现甲酰肽受体家族受体也高表达于某些恶性肿瘤细胞的表面,且与这些肿瘤的发生、发展、转移以及治疗有着密切的关系,这无疑揭示了甲酰肽受体家族受体一个新的重要作用,值得深入研究和探讨。  相似文献   
98.
The pattern of Ca2+ accumulation by tumor mitochondria (MC) was investigated under various experimental conditions. In the absence of penetrating anions tumor MC were shown to take up Ca2+ in only one fifth the amount taken up by liver MC. In the presence of acetate this difference was greater still. Inorganic phosphate (Pin) abolished the observed defects of Ca2+ transport and increased the Ca2+ capacity of the tumor MC considerably. By contrast with liver MC, Pin also had a stabilizing effect on membrane permeability of the tumor MC; this may be the cause of the increasee Ca2+ capacity of these MC.Department of Bioenergetics, Institute of Biological Physics, Academy of Sciences of the USSR, Pushchino-on-Oka. (Presented by Academician of the Academy of Medical Sciences of the USSR S. E. Severin.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 84, No. 8, pp. 202–205, August, 1977.  相似文献   
99.
We have previously shown that tumor necrosis factor-α (TNF-α), which is an important angiogenesis-related factor, was over-secreted in male BALB/c mice under social isolation stress as compared with the control, and closely associated with a remarkable elevation of tumor invasion and metastasis of colon 26-L5 carcinoma cells. In the present study, we explored the effect of isolation stress on the angiogenesis caused by colon 26-L5 carcinoma cells in vivo and in vitro. Social isolation lead to the enhancement of tumor growth after intrahepatic implantation with a fragment of colon 26-L5 tumor. Angiogenic response (number of vessels oriented towards tumor mass) and tumor growth (size) were significantly increased in the socially isolated mouse relative to that in the group-housed mice. Furthermore, higher protein level of hepatic TNF-α was found in the stressed mice than that in the control. Expression of mRNA for vascular endothelial growth factor (VEGF) and hepatocyte growth factor (HGF) were also elevated in the tumor regions and liver tissues of the stressed mice in comparison with that in group-housed mice. On the other hand, hepatic sinusoidal endothelial (HSE) cells treated with TNF-α exhibited a marked promotion of the migration, invasion, expression of mRNA for matrix metalloproteinase (MMP)-9, and tube-like formation, but no cytotoxicity against the cells in vitro. The above data suggest that the social isolation stress augmented the tumor-induced angiogenesis probably by up-regulating the angiogenesis-related factors, including TNF-α, VEGF and HGF, and consequently mediating the functions of endothelial cells such as migration, invasion, and tube-like formation.  相似文献   
100.
Abstract: Recently, an independent association between tumor necrosis factor (TNF) gene polymorphism and ceiiac disease was observed in the Irish population. We tested this association in Finnish patients with celiac disease. The TNF microsatellite alleles a2 and b3 were strongly associated (Pcorr<0.0001 for both) with celiac disease when the patients were compared to the random population. However, when the comparison was made with the DQ2-matched controls, no association could be found. We therefore conclude that in Finland the TNFa2 and b3 alleles are associated with DQ2-positive haplotypes rather than celiac disease.  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