全文获取类型
收费全文 | 868538篇 |
免费 | 60196篇 |
国内免费 | 1666篇 |
专业分类
耳鼻咽喉 | 10815篇 |
儿科学 | 27321篇 |
妇产科学 | 20688篇 |
基础医学 | 134313篇 |
口腔科学 | 23715篇 |
临床医学 | 77961篇 |
内科学 | 168918篇 |
皮肤病学 | 18628篇 |
神经病学 | 65310篇 |
特种医学 | 32270篇 |
外国民族医学 | 85篇 |
外科学 | 126426篇 |
综合类 | 15850篇 |
现状与发展 | 3篇 |
一般理论 | 326篇 |
预防医学 | 68063篇 |
眼科学 | 19018篇 |
药学 | 63630篇 |
3篇 | |
中国医学 | 2623篇 |
肿瘤学 | 54434篇 |
出版年
2021年 | 8508篇 |
2019年 | 8479篇 |
2018年 | 11640篇 |
2017年 | 9096篇 |
2016年 | 10032篇 |
2015年 | 11256篇 |
2014年 | 15499篇 |
2013年 | 21958篇 |
2012年 | 31102篇 |
2011年 | 32164篇 |
2010年 | 18451篇 |
2009年 | 17557篇 |
2008年 | 29421篇 |
2007年 | 31256篇 |
2006年 | 31277篇 |
2005年 | 29531篇 |
2004年 | 27872篇 |
2003年 | 26340篇 |
2002年 | 25139篇 |
2001年 | 40482篇 |
2000年 | 40929篇 |
1999年 | 34114篇 |
1998年 | 9758篇 |
1997年 | 8247篇 |
1996年 | 8540篇 |
1995年 | 7928篇 |
1994年 | 7275篇 |
1993年 | 6692篇 |
1992年 | 25543篇 |
1991年 | 25235篇 |
1990年 | 24492篇 |
1989年 | 24102篇 |
1988年 | 21889篇 |
1987年 | 21043篇 |
1986年 | 20032篇 |
1985年 | 18848篇 |
1984年 | 13825篇 |
1983年 | 11719篇 |
1982年 | 6522篇 |
1979年 | 12368篇 |
1978年 | 8666篇 |
1977年 | 7292篇 |
1976年 | 6944篇 |
1975年 | 7627篇 |
1974年 | 8923篇 |
1973年 | 8556篇 |
1972年 | 8016篇 |
1971年 | 7479篇 |
1970年 | 7147篇 |
1969年 | 6565篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
993.
In order to investigate the possibility that the theory of two-stage carcinogenesis can be applied to neurogenic carcinogenesis, we analyzed the promoting effect of 12-O-tetradecanoylphorbol-13-acetate (TPA) on the in vitro malignant transformation of fetal rat brain cells exposed in utero to ethylnitrosourea (ENU). Rat brain cells were transferred to a cultured system at 72 h after a single pulse of ENU (50 mg/kg body weight) to pregnant SD-JCL rats on the 18th day of gestation. The positive findings of glial fibrillary acidic protein and S-100 protein in primary cultured cells by the analysis of immunohistochemistry revealed the neuroglial origin of transformed cells. These cells were divided into 12 groups and were treated twice per week with or without TPA at concentrations from 0.1 to 50.0 ng/ml. From the results of cellular morphology, Concanavalin A agglutinability, colony forming capacity in semisolid soft agar, and tumorigenicity in vivo, malignant transformation of fetal rat brain cells appeared earlier in the ENU group treated with TPA than in the untreated ENU group. On the basis of these observations, it is suggested that TPA might be effective as a tumor promoter on ENU-induced neurogenic carcinogenesis. 相似文献
994.
N. E. McCarthy H. A. Jones N. A. Marks R. J. Shiner P. W. Ind H. O. Al-Hassi N. R. English C. M. Murray J. R. Lambert S. C. Knight A. J. Stagg 《Clinical and experimental allergy》2007,37(1):72-82
Background Dendritic cells (DC) mediate inflammation in rodent models of allergic airway disease, but the role played by human respiratory‐tract DC (hRTDC) in atopic asthma remains poorly defined. Recent data suggest that CD1 antigen presentation by hRTDC may contribute to asthma pathogenesis. Objective To investigate the influence of hRTDC on the balance between atopy and allergic asthma in human subjects and to determine whether CD1 expression by hRTDC is modulated during asthmatic inflammation. Methods Sputum cells were induced from steroid‐naïve, allergen‐challenged and allergen‐naïve subjects (atopic asthmatics, atopic non‐asthmatics and non‐atopic controls). hRTDC were identified using monoclonal antibody labelling and analysis by flow cytometry. Results hRTDC stained HLA‐DR+ (negative for markers of other cell lineages) were predominantly myeloid and comprised ∼0.5% of viable sputum cells. Sputum cells were potent stimulators of allogeneic CD4+ naïve T cells and enrichment/depletion experiments correlated stimulatory potency with DC numbers. Sputum contained cells that exhibited typical dendritic morphology when analysed by electron microscopy. Myeloid hRTDC were endocytically active, but uptake of FITC‐dextran was enhanced in cells from asthmatics (P<0.001). Despite their increased endocytic capacity, asthmatic myeloid hRTDC appeared mature and expressed increased levels of maturation markers (P<0.05–P<0.001), CD1c, CD1d and langerin (P<0.05). CD1c expression by asthmatic myeloid hRTDC was enhanced upon in vivo allergen challenge (three to ninefold within 24 h; P<0.05). CD11c−CD123high hRTDC were only detected in asthmatic sputum and were increased in number following allergen challenge. Conclusion Despite limited cell numbers, it proved possible to analyse human RTDC in induced sputum, providing evidence that increased antigen uptake and enhanced CD1 presentation by activated hRTDC may contribute to allergic airway disease. CD1 presentation by hRTDC in atopic asthma may therefore constitute a novel target for future intervention strategies. 相似文献
995.
A case of lymphocytic adenohypophysitis in a postpartum woman who became symptomatic during her 8th month of pregnancy is presented. The clinical presentation, endocrine findings, pathological findings, and operative management are discussed. Transient hypopituitarism is documented. Unlike most previously published cases, this woman had complete recovery of anterior pituitary function. 相似文献
996.
997.
Localization of proopiomelanocortin mRNA in functional subsets of neurons defined by their axonal projections 总被引:5,自引:0,他引:5
J N Wilcox J L Roberts B M Chronwall J F Bishop T O'Donohue 《Journal of neuroscience research》1986,16(1):89-96
In situ cDNA:mRNA hybridization is a technique that has been developed for the visualization of cDNA:mRNA hybrids in individual cells. To use this technique to answer questions of regulation in heterogeneous populations of cells in the brain, it must be combined with other procedures allowing for the identification of functional subgroups of neurons. We report here a procedure by which in situ cDNA:mRNA hybridization may be combined with retrograde axonal tracing using the fluorescent tracer fast blue. Using this technique, it now becomes possible to measure mRNA regulation in functional subsets of cells defined by their axonal projections. 相似文献
998.
999.
B W Brown E N Atkinson J R Thompson E D Montague 《Journal of the National Cancer Institute》1987,78(3):425-435
The degree of concordance of growth rates of primary tumors with corresponding recurrences was investigated by using data from 184 patients with breast cancer with measurable recurrences. For conduction of this examination, the detection processes of both the primary tumor and the recurrence were explored. The probability of detection of a recurrence per unit time was found to be nearly proportional to the tumor's diameter. Approximately 60,000 cells initiated the recurrence, and the distribution of doubling times of the recurrences was exponential, with a mean of 2.1 months. The probability of detection of the primary tumor per unit time was approximately proportional to its volume. The distribution of doubling times of primary tumors was nearly exponential; from other evidence, we inferred that the mean doubling time was also close to 2.1 months. Several techniques to measure growth rate agreement between the primary and recurrent tumors within individuals were developed, and all of them yielded the result that the growth rates are nearly unrelated. 相似文献
1000.