全文获取类型
收费全文 | 7338篇 |
免费 | 339篇 |
国内免费 | 51篇 |
专业分类
耳鼻咽喉 | 41篇 |
儿科学 | 242篇 |
妇产科学 | 154篇 |
基础医学 | 1474篇 |
口腔科学 | 122篇 |
临床医学 | 676篇 |
内科学 | 1310篇 |
皮肤病学 | 123篇 |
神经病学 | 641篇 |
特种医学 | 397篇 |
外科学 | 1137篇 |
综合类 | 32篇 |
一般理论 | 1篇 |
预防医学 | 405篇 |
眼科学 | 88篇 |
药学 | 499篇 |
中国医学 | 4篇 |
肿瘤学 | 382篇 |
出版年
2022年 | 57篇 |
2021年 | 100篇 |
2020年 | 74篇 |
2019年 | 95篇 |
2018年 | 118篇 |
2017年 | 99篇 |
2016年 | 114篇 |
2015年 | 157篇 |
2014年 | 180篇 |
2013年 | 232篇 |
2012年 | 356篇 |
2011年 | 337篇 |
2010年 | 207篇 |
2009年 | 216篇 |
2008年 | 357篇 |
2007年 | 368篇 |
2006年 | 405篇 |
2005年 | 357篇 |
2004年 | 348篇 |
2003年 | 329篇 |
2002年 | 335篇 |
2001年 | 224篇 |
2000年 | 201篇 |
1999年 | 198篇 |
1998年 | 90篇 |
1997年 | 64篇 |
1996年 | 55篇 |
1995年 | 61篇 |
1994年 | 49篇 |
1993年 | 37篇 |
1992年 | 93篇 |
1991年 | 73篇 |
1990年 | 81篇 |
1989年 | 90篇 |
1988年 | 63篇 |
1987年 | 71篇 |
1986年 | 68篇 |
1985年 | 67篇 |
1984年 | 47篇 |
1981年 | 34篇 |
1979年 | 44篇 |
1978年 | 39篇 |
1976年 | 36篇 |
1974年 | 34篇 |
1934年 | 36篇 |
1933年 | 34篇 |
1925年 | 35篇 |
1924年 | 36篇 |
1923年 | 39篇 |
1922年 | 50篇 |
排序方式: 共有7728条查询结果,搜索用时 15 毫秒
41.
New monomers with sterically hindered free or blocked phenolic hydroxyl groups were used as starting compounds for the preparation of stable oxygen polyradicals. In this paper the synthesis of these monomers is described: 2,6-Di-(tert-butyl)-4-vinylphenol was obtained by decarboxylation of 3-[3,5-di-(tert-butyl)-4-hydroxyphenyl]acrylic acid in yields of 80–;90%. 2,6-Di-(tert-butyl)-4-isopropenylphenol was prepared from 3,5-di-(tert-butyl)-4-hydroxyphenyl methyl ketone and methyl iodide by a GRIGNARD reaction followed by the dehydration of 2-[3,5-di-(tert-butyl)-4-hydroxyphenyl]-2-propanol. 2,6-Di-(tert-butyl)-4-isopropenylphenyl methyl ether was obtained with 64% yield from 3,5-di-(tert-butyl)-4-methoxybenzonitrile by two consecutive GRIGNARD reactions with methyl iodide via the unknown compounds 3,5-di-(tert-butyl)-4-methoxyphenyl methyl ketone and 2-[3,5-di-(tert-butyl)-4-methoxyphenyl]-2-propanol, followed by dehydration of the tertiary alcohol with 89% phosphoric acid. 相似文献
42.
Dietrich Mack Mathias Pulz Jürgen Heesemann 《Medical microbiology and immunology》1991,180(4):205-211
The structural relation of YOP-1 of european and american Yersinia enterocolitica serotypes O3, O9, O5, 27, and O8 and O20, respectively, and Y. pseudotuberculosis serotypes I, II, and III was compared by sodium dodecyl sulfate polyacrylamide gel electrophoresis and peptide mapping using Staphylococcus aureus protease V8. Apparent molecular weights of YOP-1 ranged from 206,000 (O3) to approx. 180,000 (O8). According to their respective peptide maps YOP-1 of the european and american Y. enterocolitica serotypes and Y. pseudotuberculosis serotypes could be assigned to three different groups. Evaluation of several isolates of Y. enterocolitica serotypes O3, O9, and O8 by peptide mapping indicated that YOP-1 is conserved within a serotype. However, one serotype O8 isolate differed from the consensus peptide pattern of the other serotype O8 and O20 isolates. The similarity of the peptide patterns of Yersinia serotypes which predominate in certain geographical locations, i. e., european and american Y. enterocolitica serotypes, suggest common evolution of YOP-1 of these serotypes independent of the evolution of the other serotypes. 相似文献
43.
44.
45.
Melikian Assieh A.; Leszczynska Joanna M.; Hecht Stephen S.; Hoffmann Dietrich 《Carcinogenesis》1986,7(1):9-15
We have studied the effects of the co-carcinogen catechol (1,2-dihydroxybenzene)on the metabolic activation of [3H] benzo[a]pyrene (BaP) inmouse skin, in vivo and on the binding of BaP metabolites toDNA and protein at intervals from 0.524 h. Upon topicalapplication of 0.015 mg [3H]BaP and 0.25 or 0.5 mg catecholper mouse, catechol had little effect on the total amount of[3H]BaP metabolized in mouse skin, but it affected the relativeproportions of [3H]BaP metabolites. Catechol (0.5 mg/mouse)decreased the proportion of watersoluble [3H]BaP metabolites,ethyl acetate-soluble polar metabolites and quinones, but doubledthe levels of unconjugated 3-hydroxy-BaP at all measured intervalsafter treatment. Catechol also caused a small increase in thelevels of trans-7,8-dihydroxy-7,8-dihydroBaP and trans-9,10-dihydroxy-9,10-dihydroBaP0.5 h after treatment. Two hours after treatment, the levelsof these metabolites subsided to those of the controls. Catecholdid not affect the levels of glutathione conjugates of BaP.However, it caused a decrease in glucuronide and sulphate conjugateformation from BaP. Catechol caused an 2-fold increase in theformation of anti-7, 8-dihydroxy-9, 10-epoxy-7, 8, 9, 10-tetrahydroBaP(BPDE) DNA adducts and elevated the ratio of anti-syn-BPDE-DNAadducts 1.6 to 2.9-fold. Catechol treatment increased the radioactivityassociated with epidermal proteins after [3H]BaP application.Because catechol increased levels of 3-hydroxyBaP, we consideredthe possibility that 3-hy-droxyBaP might enhance the tumor initiatingactivities of BaP or BPDE in mouse skin; a bioassay demonstratedthat this was not the case. The results of this study indicatethat one important effect of catechol related to its co-carcinogenicityis its ability to enhance formation of anti-BPDE-DNA adductsin mouse skin. 相似文献
46.
This is a review of changes in the practice of treating polytrauma managemtent within the years prior to 2020. It focuses on five different topics, 1. The development of an evidence based definition of Polytrauma, 2. Resuscitation Associated Coagulopathy (RAC), 3. neutrophil guided initial resuscitation, 4. perioperative Scoring to evaluate patients at risk, and 5. evolution of fracture fixation strategies according to protocols1,2 (Early total care, ETC, damage control orthopedics, DCO, early appropriate care, EAC, safe definitive surgery, SDS). 相似文献
47.
Burkhard Tönshoff Helio Tedesco-Silva Robert Ettenger Martin Christian Anna Bjerre Luca Dello Strologo Stephen D. Marks Lars Pape Udaykiran Veldandi Patricia Lopez Marc Cousin Priti Pandey Matthias Meier 《American journal of transplantation》2021,21(1):123-137
CRADLE was a 36-month multicenter study in pediatric (≥1 to <18 years) kidney transplant recipients randomized at 4 to 6 weeks posttransplant to receive everolimus + reduced-exposure tacrolimus (EVR + rTAC; n = 52) with corticosteroid withdrawal at 6-month posttransplant or continue mycophenolate mofetil + standard-exposure TAC (MMF + sTAC; n = 54) with corticosteroids. The incidence of composite efficacy failure (biopsy-proven acute rejection [BPAR], graft loss, or death) at month 36 was 9.8% vs 9.6% (difference: 0.2%; 80% confidence interval: −7.3 to 7.7) for EVR + rTAC and MMF + sTAC, respectively, which was driven by BPARs. Graft loss was low (2.1% vs 3.8%) with no deaths. Mean estimated glomerular filtration rate at month 36 was comparable between groups (68.1 vs 67.3 mL/min/1.73 m2). Mean changes (z-score) in height (0.72 vs 0.39; P = .158) and weight (0.61 vs 0.82; P = .453) from randomization to month 36 were comparable, whereas growth in prepubertal patients on EVR + rTAC was better (P = .050) vs MMF + sTAC. The overall incidence of adverse events (AEs) and serious AEs was comparable between groups. Rejection was the leading AE for study drug discontinuation in the EVR + rTAC group. In conclusion, though AE-related study drug discontinuation was higher, an EVR + rTAC regimen represents an alternative treatment option that enables withdrawal of steroids as well as reduction of CNIs for pediatric kidney transplant recipients. ClinicalTrials.gov: NCT01544491. 相似文献
48.
49.
50.
Pb2+ modulates the NMDA-receptor-channel complex 总被引:1,自引:1,他引:0
Vladimir Uteshev Dietrich Büsselberg Helmut L. Haas 《Naunyn-Schmiedeberg's archives of pharmacology》1993,347(2):209-213
Summary The actions of Pb2+ on NMDA channel currents of acutely dissociated hippocampal CA1- and CA3-neurones from adult rats activated by aspartate plus glycine (asp/gly) were examined. A fast reversible and a slow irreversible response to Pb2+ were found. Pb2+ applied simultaneously with asp/gly decreased an inward current. The threshold concentration was below 2 M, the current was reduced > 90% at concentrations over 100 M, The decrease of the asp/gly activated current showed no voltage dependence. Opening of NMDA channels was not necessary for Pb2+-action, as preincubation in 50 M Pb2+-containing external solution for several seconds dramatically reduced the response to asp/gly/Pb2+. This effect was reversed within 2 to 5 s of wash. Presence of Pb2+ or asp/Pb2+ or glycine/Pb2+ in the external solution did not prevent recovery of the NMDA receptor/channel complex from desensitization. Prolonged perfusion of a cell with the asp/gly/Pb2+-containing external solution resulted in an irreversible decrease of the asp/gly current, whereas the amplitude of the asp/gly/Pb2+ response did not change over the duration of an experiment. We conclude that Pb2+ modulates NMDA channel activity via interaction with the NMDA/glycine receptor: as a result the channel current decreases.Abbreviations NMDA
N-methyl-D-aspartate
- LTP
long-term potentiation
- AP5
2-amino-5-phosphonovalerate
- EGTA
ethylene glycol bis(-aminoethylether)-N,N,N,N-tetraacetic acid
- HEPES
4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid
Correspondence to H. L. Haas at the above address 相似文献