全文获取类型
收费全文 | 1742篇 |
免费 | 293篇 |
国内免费 | 39篇 |
专业分类
耳鼻咽喉 | 13篇 |
儿科学 | 122篇 |
妇产科学 | 20篇 |
基础医学 | 97篇 |
口腔科学 | 26篇 |
临床医学 | 282篇 |
内科学 | 580篇 |
皮肤病学 | 60篇 |
神经病学 | 184篇 |
特种医学 | 280篇 |
外科学 | 187篇 |
综合类 | 31篇 |
预防医学 | 61篇 |
眼科学 | 16篇 |
药学 | 59篇 |
中国医学 | 1篇 |
肿瘤学 | 55篇 |
出版年
2023年 | 52篇 |
2022年 | 12篇 |
2021年 | 27篇 |
2020年 | 91篇 |
2019年 | 13篇 |
2018年 | 88篇 |
2017年 | 69篇 |
2016年 | 71篇 |
2015年 | 61篇 |
2014年 | 95篇 |
2013年 | 111篇 |
2012年 | 49篇 |
2011年 | 40篇 |
2010年 | 77篇 |
2009年 | 109篇 |
2008年 | 43篇 |
2007年 | 50篇 |
2006年 | 46篇 |
2005年 | 34篇 |
2004年 | 17篇 |
2003年 | 14篇 |
2002年 | 16篇 |
2001年 | 30篇 |
2000年 | 13篇 |
1999年 | 27篇 |
1998年 | 83篇 |
1997年 | 95篇 |
1996年 | 78篇 |
1995年 | 68篇 |
1994年 | 49篇 |
1993年 | 52篇 |
1992年 | 27篇 |
1991年 | 16篇 |
1990年 | 25篇 |
1989年 | 53篇 |
1988年 | 42篇 |
1987年 | 26篇 |
1986年 | 20篇 |
1985年 | 20篇 |
1984年 | 16篇 |
1983年 | 9篇 |
1982年 | 14篇 |
1981年 | 14篇 |
1980年 | 14篇 |
1979年 | 8篇 |
1978年 | 8篇 |
1977年 | 9篇 |
1976年 | 10篇 |
1975年 | 7篇 |
1971年 | 8篇 |
排序方式: 共有2074条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
5.
Eugenia Cordelli Anna Maria Fresegna Alessia D'Alessio Patrizia Eleuteri Marcello Spanò Francesca Pacchierotti Paola Villani 《Toxicological sciences》2007,99(2):545-552
The increasing request of chemical safety assessment demands for the validation of alternative methods to reduce the resort to animal experimentation. Methods that evaluate reproductive toxicity are among those requiring the largest use of animals. Presently, no validated in vitro alternative exists for the assessment of reproductive toxicity. Mammalian sperm are sensitive targets of DNA-reactive chemicals, which form premutagenic adducts. Here, we propose a new method based on comet assay to detect DNA damage induced by potential germ cell mutagens in bull sperm available from assisted reproduction practices. In somatic cells, chemical-induced adducts can be revealed by comet assay that detects DNA breaks produced during adduct repair. Mature sperm, however, are devoid of repair enzymes, and adducts are processed only after fertilization. For this reason, comet assay is not sensitive to detect DNA lesions induced in sperm by most chemicals. To overcome such limitation, we developed a modified comet assay based on the addition of a protein extract from HeLa cells to agarose-embedded sperm on microscopic slides. To test the method, sperm were treated in vitro with methyl methanesulfonate (MMS) or melphalan (MLP) and comet assay was conducted both with and without protein supplementation. No effect of MMS or MLP was detected without protein supplementation; on the contrary, a clear-cut dose-dependent effect was measured after addition of the cell extract. These results represent a proof of concept of a novel in vitro mutagenicity test on sperm that could offer a promising approach to complement previously validated in vivo germ cell genotoxicity assays. 相似文献
6.
7.
8.
9.
筛检对肝癌死亡率影响的研究 总被引:5,自引:0,他引:5
5581名HBsAg阳性的男性随机分入周期性筛检组(A组,3712人)及对照组(B组,1869人)。A组(19155.4人年)共发生肝癌257例,B组(9785.5人年)为117例,两组的肝癌发生率分别为1342/10万与1196/10万;两组肝癌死亡分别为218与109例,肝癌死亡率分别为1138/10万与1114/10万。两组中Ⅰ期肝癌病例分别为29.6%与6.0%,差异有非常显著性意义。1、3、5年相对生存率A组为23.7%、7.0%、4.0%,B组为9.7%、4.0%、4.1%。用Poisson回归模型拟合显示,在调正年龄、初筛AFP及入列年份后,筛检对于肝癌的相对危险度为0.83,95%CI为0.68~1.03,有较弱的“保护”作用,Cox回归模型拟合结果显示当临床分期未引入模型时,筛检对于肝癌有显著的“保护”作用:危险率为0.6617,95%CI为0.5234~0.8365;而模型经调整后,危险率即接近“1”,95%CI为0.74~1.26。 相似文献
10.
Ralls PW; Johnson MB; Kanel G; Dobalian DM; Colletti PM; Boswell WD Jr; Radin DR; Halls JM 《Radiology》1986,161(2):451-454
FM sonography - a signal-processing technique that uses frequency and phase information as well as amplitude data - shows promise in evaluation of patients with diffuse liver disease. In a prospective blinded review of 37 patients with biopsy-proved liver disease and 42 healthy volunteers, FM sonography was clearly superior to traditional amplitude-based (AM) sonography in distinguishing healthy from diseased subjects. Statistically significant differences were seen in accuracy (FM, 98.7%; AM, 84.8%), sensitivity (FM, 97.3%; AM, 70.3%), and negative predictive value (FM, 97.7%; AM, 78.8%). Our data also suggest that current FM sonographic techniques cannot differentiate among histologic findings associated with different hepatic parenchymal abnormalities. It is unclear, therefore, whether FM imaging can reduce the numbers of patients who require biopsy for diagnosis or the frequency of biopsy procedures in patients with known disease. 相似文献