全文获取类型
收费全文 | 1795篇 |
免费 | 123篇 |
国内免费 | 40篇 |
专业分类
耳鼻咽喉 | 6篇 |
儿科学 | 1篇 |
妇产科学 | 3篇 |
基础医学 | 80篇 |
口腔科学 | 1083篇 |
临床医学 | 24篇 |
内科学 | 223篇 |
皮肤病学 | 1篇 |
神经病学 | 41篇 |
特种医学 | 17篇 |
外科学 | 51篇 |
综合类 | 144篇 |
预防医学 | 20篇 |
眼科学 | 2篇 |
药学 | 233篇 |
中国医学 | 25篇 |
肿瘤学 | 4篇 |
出版年
2024年 | 5篇 |
2023年 | 29篇 |
2022年 | 92篇 |
2021年 | 123篇 |
2020年 | 60篇 |
2019年 | 53篇 |
2018年 | 46篇 |
2017年 | 46篇 |
2016年 | 68篇 |
2015年 | 77篇 |
2014年 | 131篇 |
2013年 | 146篇 |
2012年 | 108篇 |
2011年 | 146篇 |
2010年 | 111篇 |
2009年 | 86篇 |
2008年 | 74篇 |
2007年 | 79篇 |
2006年 | 55篇 |
2005年 | 64篇 |
2004年 | 42篇 |
2003年 | 38篇 |
2002年 | 29篇 |
2001年 | 29篇 |
2000年 | 15篇 |
1999年 | 20篇 |
1998年 | 18篇 |
1997年 | 14篇 |
1996年 | 16篇 |
1995年 | 12篇 |
1994年 | 17篇 |
1993年 | 13篇 |
1992年 | 14篇 |
1991年 | 9篇 |
1990年 | 4篇 |
1989年 | 8篇 |
1988年 | 5篇 |
1987年 | 4篇 |
1986年 | 11篇 |
1985年 | 8篇 |
1984年 | 9篇 |
1983年 | 2篇 |
1982年 | 6篇 |
1981年 | 5篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1976年 | 1篇 |
排序方式: 共有1958条查询结果,搜索用时 15 毫秒
121.
Cacciatore I Caccuri AM Di Stefano A Luisi G Nalli M Pinnen F Ricci G Sozio P 《Il Farmaco; edizione pratica》2003,58(9):787-793
The new GSH analogues H-Glo(-Ser-Gly-OH)-OH (5), its O-benzyl derivative 4, and H-Glo(-Asp-Gly-OH)-OH (9), characterized by the replacement of central cysteine with either serine or aspartic acid, and containing an urethanic fragment as isosteric substitution of the scissile gamma-glutamylic junction, have been synthesized and characterized. Their ability to inhibit human GST P1-1 (hGST P1-1) in comparison with H-Glu(-Ser-Gly-OH)-OH and H-Glu(-Asp-Gly-OH)-OH, which are potent competitive inhibitors of rat GST 3-3 and 4-4, has been evaluated. In order to further investigate the effect of the isosteric substitution on the binding abilities of the new GSH analogues 4, 5 and 9, the previously reported cysteinyl-containing analogue H-Glo(-Cys-Gly-OH)-OH has been also evaluated as a co-substrate for hGSTP1-1. 相似文献
122.
This study evaluated the influence of irradiation on dentin bond strength. Sixty irradiated and 60 non-irradiated human third molars were used. The irradiation dose of 60 Gy was fractionally applied over 6 weeks (2 Gy day(-1), 5 days week(-1). All teeth were prepared in a special manner allowing the simulation of intra-pulpal pressure and dentin perfusion. Dentin specimens with a thickness of 2.0 mm were obtained under standardized conditions. The specimens were randomly assigned to four experimental groups. Tensile bond strength of four different dentin bonding agents (Scotchbond 1, Solobond Plus, Prime&Bond 2.1 and Syntac) was evaluated using an Instron Universal testing machine. Pairwise comparison did not show any significant differences between the irradiated and non-irradiated groups. The influence of the different dentin adhesives was significant (P=0.0001; ANOVA). Compared with Solobond Plus and Prime&Bond 2.1, the use of Scotchbond 1 resulted in a significantly higher tensile bond strength in non-irradiated specimen (P< 0.05; closed test procedure based on Kruskal-Wallis test). Within the limitations of an in vitro study, it can be concluded that adhesive restoration procedures can be successfully used in patients irradiated for cancer of the head and neck. 相似文献
123.
目的:通过对粘结桥的粘结面不同处理的粘结强度测试,为临床应用提供理论依据。方法:选用钴铬合金,铸造成一定规格的(10mm×10mm×1mm)板,随机分成5组,以电蚀、喷砂方法处理,用高真空喷镀仪及万能金相显微镜观察,抗剪粘结强度测试,并作统计分析。结果:抗剪粘结强度由强到弱依次为:单纯电蚀;喷砂后电蚀;单纯喷砂;电蚀后喷砂;磨光。结论:对制作钴铬合金舌侧翼板粘结桥的粘结面以电蚀处理为首选;而单纯喷砂处理亦可提高粘结强度,为临床应用提供了方便、易操作的方法。 相似文献
124.
Kerstin Bitter Ani Hambarayan Konrad Neumann Uwe Blunck Guido Sterzenbach 《European journal of oral sciences》2013,121(4):349-354
Irrigation after post space preparation and its effects on the bond strength of different adhesive strategies are still an issue of interest. The aim of the present study was to investigate the effects of various irrigation protocols (IPs) on the push‐out bond strengths of fiber posts. One‐hundred and fifty extracted human anterior teeth were divided into three groups (n = 50 each) and endodontically treated. The post space was irrigated before post placement using the following five IPs in each group: IP1 (control): 5 ml of distilled water; IP2: 5.25% sodium hypochlorite (NaOCl) applied with passive ultrasonic irrigation (PUI); IP3: 1% NaOCl applied with PUI; IP4: 18% ethylenediaminetetracetic acid (EDTA) followed by 5.25% NaOCl; and IP5: 2% chlorhexidine (CHX). Fiber posts placement in each group was performed using three different adhesive strategies. A self‐etch adhesive system revealed higher bond strength (16.2 ± 6.9 MPa) compared with an etch‐and‐rinse adhesive (8.5 ± 4.2 MPa) and a self‐adhesive resin cement (9.2 ± 4.7 MPa). The use of 18% EDTA/5.25% NaOCl increased the bond strength of the self‐adhesive resin cement. Conversely, this IP decreased the bond strength for the etch‐and‐rinse adhesive system, whilst 1% NaOCl enhanced the bond strength for the same system. Consequently, each adhesive strategy may need to be adapted to a specific IP. 相似文献
125.
《Acta odontologica Scandinavica》2013,71(5):380-386
AbstractObjective. Intra-canal post systems are commonly used to restore root-filled teeth. Bond strengths of the posts can be affected by various surface treatments of the post or the dentin. The aim of this study was to evaluate the effects of dentin surface treatments including erbium-chromium; yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser irradiation with different intensities on the push-out bond strength of the glass fiber posts to root dentin. Materials and methods. Forty single-rooted human maxillary incisors were filled and post spaces were prepared. After these procedures, the specimens were divided randomly into four groups according to the dentin surface treatments, as follows: (i) untreated surface (control), (ii) 1W Er,Cr:YSGG laser application, (iii) 2W Er,Cr:YSGG laser application and (iv) 3W Er,Cr:YSGG laser application. Then the posts were cemented into the root canals using dual-cured resin cement. Bonded specimens were cut into 1-mm-thick slices and push-out tests were performed using a universal testing device. All specimens were loaded until fracture and the failure modes were evaluated with a stereomicroscope at 32× magnification. Representative specimens were analyzed by scanning electron microscopy. Data were analyzed using a one-way ANOVA, Tukey and Wilcoxon tests. Results. The bond strength values ranged from 3.22–4.68 MPa. There were no statistically significant differences among the groups, regardless of the different levels. The coronal and middle levels of the post space had significantly higher bond strength values compared with the apical level (p < 0.05). Conclusion. Er,Cr:YSGG laser irradiation with different intensities did not increase the bond strength of the fiber posts to the root canal dentin walls. 相似文献
126.
以水作溶剂,N-乙烯基-2-吡咯烷酮辐射聚合得到了聚N-乙烯基-2-吡咯烷酮水凝胶。以乙醇或丙酮作为溶剂时,前者情况下的聚合速度大于后者。这些现象,可用水、乙醇能与N-乙烯基-2-吡咯烷酮形成氢键来解释。聚合反应终止动力学,不受溶剂性质的影响,都属于双分子终止反应。 相似文献
127.
ISABELLA L. KARLE 《Chemical biology & drug design》1986,28(1):6-14
Crystals of [Phe4 Val6] antamanide (cyclic[ValProProPhePhe]2) grown from dioxane/H2O, with space group P21212 and cell parameters a= 15.099(4), b = 22.008(5) and c = 11.024(3) Å, are almost identical to crystals grown from H2O/acetone, the structure of which was determined a number of years ago. Perpeptide molecule there are the equivalent of 12 water molecules occupying 16 sites in both crystals; however, in the new investigation a number of water molecules present at one-half occupancy have been found in different positions than in the earlier analysis. The interpretation of the hydrogen bonding between peptide/water and between water/water is much more satisfactory. Pentagonal water assemblies are present in the solvent channel. There is a distinct indication of the occurrence of a bifurcated bond between two water molecules, as well as the presence of three-center hydrogen bonds joining three water molecules. This may be the first experimental example of a bifurcated bond between two water molecules. 相似文献
128.
129.
The purpose of this study was to determine the effects of a phosphoric acid gel and solution, and saliva contamination of etched enamel on the tensile bond strength (TBS) of a posterior composite resin to etched enamel. Ninety-six extracted human permanent maxillary canines were used in this study. The test system developed by Kemper and Kilian was used to determine the TBS of a posterior composite resin (P-10) to enamel. The ground enamel surfaces were etched with 37% H3PO4 gel for 60 sec and washed for 15 sec or 30 sec, and with 37% H3PO4 solution for 60 sec and washed for 15 sec or 30 sec, respectively. The ground enamel surfaces were also etched with H3PO4 gel for 60 sec, washed for 15 sec and rewashed for 15 sec after saliva contamination of the etched enamel for 15 sec, 60 sec and 60 min, respectively. Etched enamel surfaces contaminated with saliva for 15 sec were re-etched for 15 sec and washed for 15 sec. The test specimens were mounted in an Instron machine and subjected to a tensile load at 0.02 inch. min−1. The force required to break a test specimen was recorded, and the bond strengths were calculated and expressed in MN.m−2. The data were analyzed by ANOVA and Duncan's multiple range test at the 5% level of significance. The H3PO4 composition (gel vs solution) and wash times had no significantly different effect on TBS. Only a 60 min saliva contamination significantly reduced TBS. In this study the TBS was determined 24 h after specimen preparation. It is possible that salivary contamination of etched enamel may have an adverse effect on bond strength only after prolonged immersion of the test specimens prior to testing. 相似文献
130.
对玻璃钢(FRP)复合增强聚氯乙烯进行了研究,结果发现,不同的PVC表面处理技术及粘合剂品种,不仅对粘合性能,而且在工艺方法上差异极大。选用C-3化学处理剂及M型、EJ型粘合剂,FRP-PVC的粘合强度达10MPa,且化学处理、粘合、玻璃钢成型及固化一步完成。FRP-PVC复合界面,经水煮试验、冷热交替及声发射测试,表明粘合状态良好。φ100mm的PVC管,FRP增强层厚为2mm,复合管的承压达18MPa以上。 相似文献