首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1362篇
  免费   85篇
  国内免费   4篇
耳鼻咽喉   29篇
儿科学   38篇
妇产科学   12篇
基础医学   167篇
口腔科学   45篇
临床医学   67篇
内科学   267篇
皮肤病学   220篇
神经病学   67篇
特种医学   63篇
外科学   219篇
综合类   15篇
一般理论   1篇
预防医学   35篇
眼科学   39篇
药学   95篇
中国医学   6篇
肿瘤学   66篇
  2023年   12篇
  2022年   22篇
  2021年   35篇
  2020年   22篇
  2019年   22篇
  2018年   32篇
  2017年   32篇
  2016年   34篇
  2015年   46篇
  2014年   56篇
  2013年   50篇
  2012年   61篇
  2011年   82篇
  2010年   50篇
  2009年   40篇
  2008年   53篇
  2007年   53篇
  2006年   45篇
  2005年   55篇
  2004年   58篇
  2003年   37篇
  2002年   57篇
  2001年   44篇
  2000年   29篇
  1999年   22篇
  1998年   13篇
  1997年   8篇
  1996年   10篇
  1995年   7篇
  1994年   13篇
  1992年   19篇
  1991年   14篇
  1990年   22篇
  1989年   24篇
  1988年   19篇
  1987年   19篇
  1986年   18篇
  1985年   27篇
  1984年   17篇
  1983年   16篇
  1982年   12篇
  1981年   8篇
  1979年   21篇
  1978年   13篇
  1977年   9篇
  1975年   9篇
  1974年   9篇
  1973年   15篇
  1972年   12篇
  1967年   8篇
排序方式: 共有1451条查询结果,搜索用时 171 毫秒
41.
42.
43.
An efficient and versatile synthesis method has been postulated for hydroxymethylated rac - and meso-cyclohexanoid derivatives. The synthesis of these stereoisomers was achieved easily with traditional methods using hexahydroisobenzofuran 6 , prepared from commercially available cis-hydrophthalic anhydride. The study, involving diastereoselective epoxidation and cis-hydroxylation, was conducted to obtain epoxy-, cis-, and trans-diol-furans 7, 8 , and 9 . After sulfamic acid-catalyzed ring-opening reaction of the epoxide and furan rings, rac- and meso-tetraacetates 14, 15 , and 16 were afforded. Hydrolysis of acetate groups with ammonia in absolute methanol yielded the desired tetrols rac -17 , meso -18 , and meso -19 . All structures, after purification by chromatographic methods and elucidation by spectral techniques, were screened against α- and β-glucosidases. Compounds 7, 8, 10, 17, 18 , and 19 were also evaluated for their antibacterial and antifungal activity against some selected synthesized compounds with varying degrees of inhibitory effects on the growth of different pathogenic microorganisms by the well-diffusion method. In addition, Saccharomyces cerevisiae α-glucosidase molecular modeling studies were performed for all rac- and meso-compounds 7, 8, 10, 17, 18 , and 19 .  相似文献   
44.
Discovery of novel DNA gyrase B inhibitors remains an attractive field in the search for new antibacterial drugs to overcome the known bacterial resistance mechanisms. In the present study, we designed and synthesized novel ethylurea derivatives of 4,5,6,7‐tetrahydrobenzo[1,2‐d]thiazole‐2,6‐diamine, 2‐(2‐aminothiazol‐4‐yl)acetic acid, and benzo[1,2‐d]thiazole‐2,6‐diamine and evaluated their Escherichia coli DNA gyrase inhibition. The most potent DNA gyrase inhibitors in the prepared library of compounds were benzo[1,2‐d]thiazoles 32–34 , 36 , and 37 with IC50 values in the low micromolar range. The most promising inhibitors identified were evaluated against selected Gram‐positive and Gram‐negative bacterial strains. Compound 33 showed a MIC of 50 μM against an E. coli efflux pump‐defective strain, which suggests that efflux decreases the on‐target concentrations of these compounds.  相似文献   
45.
International Urology and Nephrology - To evaluate the effects of aging on the success rate of retrograde intrarenal surgery (RIRS) and the development of medical and surgical complications by...  相似文献   
46.
Objective:Bi-allelic mutations in the wolframin gene (WFS1) cause Wolfram syndrome 1 (WS1 or DIDMOAD) characterized by non-autoimmune diabetes mellitus, optic atrophy, diabetes insipidus, sensorineural deafness, urinary tract abnormalities, and neuropsychiatric disorders. Patients presenting with an incomplete phenotype of WS1 were evaluated using homozygosity mapping and subsequent whole-exome sequencing.Methods:Four unrelated consanguineous Turkish families, including seven affected children, and their unaffected parents and siblings were evaluated. Homozygosity mapping was performed, followed by whole-exome sequencing of WFS1. Mutations were classified according to results of “in silico” analyses, protein prediction, and functional consequences.Results:Homozygosity mapping confirmed shared homozygous regions on chromosome 4 (chr4p16.1) between the affected individuals, that was absent in their unaffected siblings. Exome sequencing identified three novel (c.1215T>A, c.554G>A, c.1525_1540dup) and one known (c.1522_1523delTA) mutations in WFS1. All mutations were predicted to cause stop codon leading to early termination of protein synthesis and complete loss-of-function. All patients were found to be homozygous for the change, with parents and other unaffected siblings being carriers.Conclusion:Our study expands the mutation spectrum of WSF1 mutations with three novel mutations. Homozygosity mapping may provide enrichment for molecular genetic analysis and early diagnosis of WS1 patients with incomplete phenotype, particularly in consanguineous pedigrees.  相似文献   
47.
Odontology - The aim of the present study was to compare the effect of chitosan nanoparticle, QMix, and 17% EDTA on the penetrability of a calcium silicate-based sealer into dentinal tubules using...  相似文献   
48.
49.
The objective of the present work was to study the phytoremediation capacity of Callitriche cophocarpa concerning water contaminated with thallium (Tl), cadmium (Cd), zinc (Zn), and lead (Pb) derived from the natural environment. We found that after a 10-day incubation period, shoots of C. cophocarpa effectively biofiltrated the water so that it met (for Cd, Zn, and Pb) appropriate quality standards. The order of accumulation of the investigated elements by shoots (mg kg?1 dry weight) were as follows: Zn (1120) < Tl (251) < Cd (71) < Pb (35). The order of bioconcentration factors were as follows: Cd (1177) < Tl (1043) < Zn (718) < Pb (597). According to Microtox bioassay, C. cophocarpa significantly eradicated polluted water toxicity. During the experiment, the physiological status of plants was monitored by taking measurements of photosystem II activity (maximum efficiency of PSII, photochemical fluorescence quenching, nonphotochemical fluorescence quenching, and quantum efficiency of PSII), photosynthetic pigment contents, and shoot morphology. Plants exposed to metallic pollution did not exhibit significant changes in their physiological status compared with the control. This work is potentially applicable to the future use of C. cophocarpa in the phytoremediation of polluted, natural watercourses.  相似文献   
50.
The aim of this clinical study was to test the efficacy of a light‐emitting diode (LED) light and a diode laser, when bleaching with sodium perborate. Thirty volunteers were selected to participate in the study. The patients were randomly divided into two groups. The initial colour of each tooth to be bleached was quantified with a spectrophotometer. In group A, sodium perborate and distilled water were mixed and placed into the pulp chamber, and the LED light was source applied. In group B, the same mixture was used, and the 810 nm diode laser was applied. The final colour of each tooth was quantified with the same spectrophotometer. Initial and final spectrophotometer values were recorded. Mann–Whitney U‐test and Wicoxon tests were used to test differences between both groups. Both devices successfully whitened the teeth. No statistical difference was found between the efficacy of the LED light and the diode laser.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号