全文获取类型
收费全文 | 874篇 |
免费 | 59篇 |
国内免费 | 61篇 |
专业分类
耳鼻咽喉 | 1篇 |
儿科学 | 26篇 |
妇产科学 | 7篇 |
基础医学 | 135篇 |
口腔科学 | 19篇 |
临床医学 | 123篇 |
内科学 | 202篇 |
皮肤病学 | 23篇 |
神经病学 | 44篇 |
特种医学 | 96篇 |
外科学 | 69篇 |
综合类 | 31篇 |
预防医学 | 38篇 |
眼科学 | 6篇 |
药学 | 80篇 |
中国医学 | 1篇 |
肿瘤学 | 93篇 |
出版年
2021年 | 12篇 |
2020年 | 7篇 |
2019年 | 10篇 |
2018年 | 12篇 |
2017年 | 8篇 |
2016年 | 6篇 |
2015年 | 22篇 |
2014年 | 19篇 |
2013年 | 24篇 |
2012年 | 34篇 |
2011年 | 42篇 |
2010年 | 23篇 |
2009年 | 27篇 |
2008年 | 15篇 |
2007年 | 66篇 |
2006年 | 38篇 |
2005年 | 48篇 |
2004年 | 30篇 |
2003年 | 31篇 |
2002年 | 21篇 |
2001年 | 30篇 |
2000年 | 19篇 |
1999年 | 23篇 |
1998年 | 29篇 |
1997年 | 41篇 |
1996年 | 31篇 |
1995年 | 26篇 |
1994年 | 16篇 |
1993年 | 27篇 |
1992年 | 16篇 |
1991年 | 18篇 |
1990年 | 21篇 |
1989年 | 37篇 |
1988年 | 20篇 |
1987年 | 17篇 |
1986年 | 16篇 |
1985年 | 11篇 |
1984年 | 11篇 |
1983年 | 9篇 |
1982年 | 6篇 |
1981年 | 4篇 |
1980年 | 13篇 |
1979年 | 4篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1975年 | 5篇 |
1969年 | 4篇 |
1968年 | 3篇 |
1967年 | 5篇 |
1966年 | 6篇 |
排序方式: 共有994条查询结果,搜索用时 15 毫秒
1.
The initial management of bladder outflow obstruction typically related to benign prostatic hyperplasia (BPH) falls to a large extent within the remit of general practice. Referral onwards to secondary care typically arises following the failure to respond to conservative measures or when complications have supervened; the most significant of which is urinary retention. In the hospital setting, anaesthesia, constipation and immobility are the common precipitants. What follows is a practical guide to the management of these situations and provides an overview of the conservative, medical, minimally invasive and surgical treatments available. 相似文献
2.
3.
4.
5.
S Manam R D Storer S Prahalada K R Leander A R Kraynak B J Ledwith M J van Zwieten M O Bradley W W Nichols 《Cancer research》1992,52(12):3347-3352
We compared the profile of ras gene mutations in spontaneous CD-1 mouse liver tumors with that found in liver tumors that were induced by a single i.p. injection of either 7,12-dimethylbenz(a)anthracene (DMBA), 4-aminoazobenzene, N-hydroxy-2-acetylaminofluorene, or N-nitrosodiethylamine. By direct sequencing of polymerase chain reaction-amplified tumor DNA, the carcinogen-induced tumors were found to have much higher frequencies of ras gene activation than spontaneous tumors. Furthermore, each carcinogen caused specific types of ras mutations not detected in spontaneous tumors, including several novel mutations not previously associated with either the carcinogen or mouse hepatocarcinogenesis. For example, the model compound DMBA is known to cause predominantly A to T transversions in Ha-ras codon 61 in mouse skin and mammary tumors, consistent with the ability of DMBA to form bulky adducts with adenosine. Our results demonstrate that the predominant mutation caused by DMBA in mouse liver tumors is a G to C transversion in Ki-ras codon 13 (DMBA is also known to form guanosine adducts), illustrating the influence of both chemical- and tissue-specific factors in determining the type of ras gene mutations in a tumor. 4-Aminoazobenzene and N-hydroxy-2-acetylaminofluorene also caused the Ki-ras codon 13 mutation. In addition, we found that N-nitrosodiethylamine, 4-aminoazobenzene, and N-hydroxy-2-acetylaminofluorene all caused G to T transversions in the N-ras gene (codons 12 or 13). This is the first demonstration of N-ras mutations in mouse liver tumors, establishing a role for the N-ras gene in mouse liver carcinogenesis. Finally, comparison of the ras mutations detected in the direct tumor analysis with those detected after NIH3T3 cell transfection indicates that spontaneous ras mutations (in Ha-ras codon 61) are often present in only a small fraction of the tumor cells, raising the possibility that they may sometimes occur as a late event in CD-1 mouse hepatocarcinogenesis. 相似文献
6.
7.
Background
There is currently an unprecedented expressed need and demand for estimates of maternal mortality in developing countries. This has been stimulated in part by the creation of a Millennium Development Goal that will be judged partly on the basis of reductions in maternal mortality by 2015. 相似文献8.
9.
10.
Reddy MV Storer RD Laws GM Armstrong MJ Barnum JE Gara JP McKnight CG Skopek TR Sina JF DeLuca JG Galloway SM 《Environmental and molecular mutagenesis》2002,40(1):1-17
3-Methylindole (3MI), melatonin (Mel), serotonin (Ser), and tryptamine (Tryp) were evaluated in vitro for their potential to induce DNA adducts, DNA strand breaks, chromosomal aberrations (Abs), inhibition of DNA synthesis, and mutations. All compounds produced DNA adducts in calf thymus DNA in the presence of rat liver S9. In cultured rat hepatocytes, all produced DNA adducts but none induced DNA strand breaks. In Chinese hamster ovary cells, 3MI and Mel produced DNA adducts, Abs, and inhibition of DNA synthesis with and without S9, except that Mel without S9 did not form adducts. Ser formed DNA adducts, was an equivocal Abs inducer, and suppressed DNA synthesis. Tryp induced neither adducts nor Abs, but did suppress DNA synthesis with S9. Ser and Tryp were less cytotoxic than 3MI and Mel. Mel, Ser, and Tryp failed to induce mutations in Salmonella and E. coli strains with or without S9. 3MI and Mel produced DNA adducts but not mutations in Salmonella TA100 with S9. 3MI and its metabolite indole 3-carbinol also did not induce mutations in a shuttle vector system in human cells. The lack of correlation between DNA adducts and other genotoxicity endpoints for these indole compounds may be due to the higher sensitivity of the (32)P-postlabeling adduct assay or it may indicate that the indole-DNA adducts per se are not mutagenic and are not able to induce strand breaks or alkali-labile lesions. The indole-induced Abs may result from cytotoxicity and suppression of DNA synthesis with minimal if any contribution from DNA adducts. 相似文献