全文获取类型
收费全文 | 577篇 |
免费 | 37篇 |
国内免费 | 22篇 |
专业分类
耳鼻咽喉 | 1篇 |
儿科学 | 37篇 |
妇产科学 | 3篇 |
基础医学 | 32篇 |
口腔科学 | 26篇 |
临床医学 | 47篇 |
内科学 | 71篇 |
皮肤病学 | 10篇 |
神经病学 | 23篇 |
特种医学 | 122篇 |
外科学 | 58篇 |
综合类 | 31篇 |
预防医学 | 36篇 |
眼科学 | 31篇 |
药学 | 75篇 |
肿瘤学 | 33篇 |
出版年
2023年 | 5篇 |
2021年 | 3篇 |
2020年 | 6篇 |
2019年 | 11篇 |
2018年 | 12篇 |
2017年 | 2篇 |
2016年 | 5篇 |
2015年 | 9篇 |
2014年 | 9篇 |
2013年 | 13篇 |
2012年 | 10篇 |
2011年 | 14篇 |
2010年 | 11篇 |
2009年 | 14篇 |
2008年 | 21篇 |
2007年 | 37篇 |
2006年 | 38篇 |
2005年 | 14篇 |
2004年 | 13篇 |
2003年 | 5篇 |
2002年 | 11篇 |
2001年 | 21篇 |
2000年 | 15篇 |
1999年 | 18篇 |
1998年 | 36篇 |
1997年 | 21篇 |
1996年 | 27篇 |
1995年 | 28篇 |
1994年 | 21篇 |
1993年 | 26篇 |
1992年 | 12篇 |
1991年 | 9篇 |
1990年 | 15篇 |
1989年 | 6篇 |
1988年 | 11篇 |
1987年 | 9篇 |
1986年 | 20篇 |
1985年 | 14篇 |
1984年 | 10篇 |
1983年 | 7篇 |
1982年 | 8篇 |
1981年 | 7篇 |
1980年 | 15篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1975年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有636条查询结果,搜索用时 484 毫秒
91.
92.
Donald F. Smee Patricia A. McKernan Hassan A. Alaghamandan Karl B. Frank Kandasamy Ramasamy Ganapathi R. Revankar Roland K. Robins 《Antiviral research》1988,10(6):263-277
Eight sugar-modified pyrrolopyrimidine nucleoside analogs related to the antibiotic sangivamycin were evaluated in cell culture against herpes simplex types 1 (HSV-1) and 2 (HSV-2), cytomegalovirus (CMV), adenovirus, and visna virus. Five of the compounds were highly active against most of the viruses with 50% inhibition (ED50) values of 1–10 μM. The selectivity of the agents was low, with inhibition of uninfected cell proliferation occurring within 5-fold that of the virus ED50 for most of the viruses. The compounds did not possess RNA virus-inhibitory activity when evaluated against certain myxo-, paramyxo-, picorna-, reo-, rhabdo-, and togaviruses. Two of the nucleosides were tested further in a cell line persistently infected with Friend leukemia virus where they were inhibitory to both virus yield and cell proliferation at 4–5 μM. Several of the sangivamycin analogs were tested in animal models using a twice-a-day treatment regimen. They proved to be inactive against HSV-1, murine CMV and/or Friend leukemia virus infections in mice. 相似文献
93.
94.
Atack JR Bayley PJ Seabrook GR Wafford KA McKernan RM Dawson GR 《Neuropharmacology》2006,51(6):1023-1029
The in vitro and in vivo properties of L-655,708, a compound with higher affinity for GABA(A) receptors containing an alpha5 compared to an alpha1, alpha2 or alpha3 subunit have been examined further. This compound has weak partial inverse agonist efficacy at each of the four subtypes but, and consistent with the binding data, has higher functional affinity for the alpha5 subtype. In a mouse hippocampal slice model, L-655,708 was able to enhance the long-term potentiation produced by a theta burst stimulation, consistent with a potential role for the alpha5 subtype in processes involving synaptic plasticity, such as learning and memory. When administered in a formulation specifically designed to achieve relatively constant plasma drug concentrations, and therefore maintain selective occupancy of alpha5- compared to alpha1-, alpha2- and alpha3-containing receptors (75+/-4% versus 22+/-10%, respectively), L-655,708 did not alter the dose of pentylenetetrazole required to induce seizures, indicating that the inverse agonist effects of L-655,708 at the alpha5 subtype are not associated with a proconvulsant liability. In the Morris water maze, L-655,708 enhanced performance not only during acquisition but also in a probe trial, demonstrating that this compound has cognition enhancing effects. These data further support the potential of alpha5-containing GABA(A) receptors as a target for novel cognition enhancing drugs. 相似文献
95.
96.
97.
98.
Radiographic mottle and patient exposure in mammography 总被引:1,自引:0,他引:1
99.
C R Petrie H B Cottam P A McKernan R K Robins G R Revankar 《Journal of medicinal chemistry》1985,28(8):1010-1016
Several 3,4,6-trisubstituted pyrazolo[3,4-d]pyrimidine ribonucleosides were prepared and tested for their biological activity. High-temperature glycosylation of 3,6-dibromoallopurinol with 1-O-acetyl-2,3,5-tri-O-benzoyl-D-ribofuranose in the presence of BF3 X OEt2, followed by ammonolysis, provided 6-amino-3-bromo-1-beta-D-ribofuranosylpyrazolo-[3,4-d]pyrimidin-4(5H)-on e. Similar glycosylation of either 3-bromo-4(5H)-oxopyrazolo [3,4-d]pyrimidin-6-yl methyl sulfoxide or 6-amino-3-bromopyrazolo [3,4-d]pyrimidin-4(5H)-one, and subsequent ammonolysis, also gave 7a. The structural assignment of 7a was on the basis of spectral studies, as well as its conversion to the reported guanosine analogue 1d. Application of this glycosylation procedure to 6-(methylthio)-4(5H)-oxopyrazolo[3,4-d]pyrimidine-3-carboxamide gave the corresponding N-1 glycosyl derivative. Dethiation and debenzoylation of 16a provided an alternate route to the recently reported 3-carbamoylallopurinol ribonucleoside thus confirming the structural assignment of 16a and the nucleosides derived therefrom. Oxidation of 16a and subsequent ammonolysis afforded 6-amino-1-beta-D-ribofuranosyl-4(5H)-oxopyrazolo[3, 4-d]pyrimidine-3-carboxamide. Alkaline treatment of 15a gave 6-azacadeguomycin. Acetylation of 15a, followed by dehydration with phosgene, provided the versatile intermediate 6-amino-1-(2,3,5-tri-O-acetyl-beta-D-ribofuranosyl)-4(5H)-oxopyrazolo [3, 4-d]pyrimidine-3-carbonitrile. Deacetylation of 19 gave 6-amino-1-beta-D-ribofuranosyl-4(5H)-oxopyrazolo[3, 4-d]pyrimidine-3-carbonitrile. Reaction of 19 with H2S gave 6-amino-1-beta-D-ribofuranosyl-4(5H)-oxopyrazolo[3, 4-d]pyrimidine-3-thiocarboxamide. All of these compounds were tested in vitro against certain viruses and tumor cells. Among these compounds, the guanosine analogues 7a and 20a showed significant activity against measles in vitro and were found to exhibit moderate antitumor activity in vitro against L1210 and P388 leukemia. 6-Azacadeguomycin and all other compounds were inactive against the viruses and tumor cells tested in vitro. 相似文献
100.