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   59785篇
  免费   4834篇
  国内免费   2055篇
耳鼻咽喉   382篇
儿科学   1431篇
妇产科学   746篇
基础医学   8962篇
口腔科学   794篇
临床医学   4579篇
内科学   9296篇
皮肤病学   1171篇
神经病学   4811篇
特种医学   869篇
外国民族医学   11篇
外科学   4422篇
综合类   6470篇
现状与发展   10篇
预防医学   4762篇
眼科学   994篇
药学   10365篇
  8篇
中国医学   3073篇
肿瘤学   3518篇
  2023年   832篇
  2022年   979篇
  2021年   1761篇
  2020年   1804篇
  2019年   2403篇
  2018年   2346篇
  2017年   1991篇
  2016年   1922篇
  2015年   2100篇
  2014年   3334篇
  2013年   4073篇
  2012年   3454篇
  2011年   4081篇
  2010年   3422篇
  2009年   2849篇
  2008年   2690篇
  2007年   2517篇
  2006年   2140篇
  2005年   1860篇
  2004年   1660篇
  2003年   1541篇
  2002年   1268篇
  2001年   1097篇
  2000年   845篇
  1999年   826篇
  1998年   630篇
  1997年   582篇
  1996年   511篇
  1995年   496篇
  1994年   446篇
  1993年   411篇
  1992年   380篇
  1991年   361篇
  1990年   312篇
  1989年   256篇
  1988年   249篇
  1987年   186篇
  1985年   817篇
  1984年   1045篇
  1983年   824篇
  1982年   949篇
  1981年   891篇
  1980年   666篇
  1979年   624篇
  1978年   447篇
  1977年   358篇
  1976年   412篇
  1975年   313篇
  1974年   195篇
  1973年   197篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
Background: Corneal Dystrophy and Perceptive Deafness (CDPD) or Harboyan syndrome is an autosomal recessive rare disorder, characterized by congenital corneal opacities and progressive sensorineural hearing loss, which usually begins after the second decades of life. This study reports the ophthalmic, audiological and genetic features, in five CDPD affected patients from three Chilean families.

Materials and Methods: Five individuals affected with CDPD from three unrelated Chilean families were clinically and genetically examined. To evaluate a putative founder mutation 7 SNPs were analyzed in the three families, an Argentinian patient (carrier of the same mutation previously reported) and 87 Chilean controls.

Results: The ophthalmic symptoms in the five patients were bilateral and symmetric, starting before one year of age, and visual acuity varied from 0.1 to 0.3. In all cases, hearing loss began over 8 years old. The sequence of the 19 exons of SLC4A11 gene of all the affected patients exhibited homozygous eight nucleotide sequence duplication (c.2233_2240dup TATGACAC, p.(Ile748Metfs*5)) at the end of exon 16. All the affected patients of the three families were homozygous for a haplotype composed of five SNPs and covering 4,1 Mb. The same haplotype was present in one allele of the heterozygous Argentinean patient and has a frequency of 2.76% in Chilean population.

Conclusions: The five CDPD patients were homozygous for the same mutation in the SLC4A11 gene. Haplotype analysis of all the affected, including the case reported from Argentina was in accordance with a founder mutation.  相似文献   

52.
  1. Coumadin (R/S-warfarin) metabolism plays a critical role in patient response to anticoagulant therapy. Several cytochrome P450s oxidize warfarin into R/S-6-, 7-, 8-, 10, and 4′-hydroxywarfarin that can undergo subsequent glucuronidation by UDP-glucuronosyltransferases (UGTs); however, current studies on recombinant UGTs cannot be adequately extrapolated to microsomal glucuronidation capacities for the liver.

  2. Herein, we estimated the capacity of the average human liver to glucuronidate hydroxywarfarin and identified UGTs responsible for those metabolic reactions through inhibitor phenotyping. There was no observable activity toward R/S-warfarin, R/S-10-hydroxywarfarin or R/S-4′-hydroxywarfarin.

  3. The observed metabolic efficiencies (Vmax/Km) toward R/S-6-, 7-, and especially 8-hydroxywarfarin indicated a high glucuronidation capacity to metabolize these compounds.

  4. UGTs demonstrated strong regioselectivity toward the hydroxywarfarins. UGT1A6 and UGT1A1 played a major role in R/S-6- and 7-hydroxywarfarin glucuronidation, respectively, whereas UGT1A9 accounted for almost all of the generation of the R/S-8-hydroxywarfarin glucuronide.

  5. In summary, these studies expanded insights to glucuronidation of hydroxywarfarins by pooled human liver microsomes, novel roles for UGT1A6 and 1A9, and the overall degree of regioselectivity for the UGT reactions.

  相似文献   
53.
54.
55.
Objective: The study was undertaken to investigate the effects of polyethyleneimine (PEI)-mediated adenovirus 5 early region 1A (E1A) on radiosensitivity of human hepatic carcinoma cell in vitro and to disclosure the underlying mechanism. Materials and Methods: Human hepatic carcinoma SMMC-7721 cell line was transfected with E1A gene using PEI vector. Untransfected cells (SMMC-7721 group), cells transfected with blank-vector (SMMC-7721-vect group), and cells transfected with E1A gene (SMMC-7721-E1A group) were treated with 6 MV X-ray irradiation at doses of 0, 1, 2, 4, 8 and Gy, respectively. Radiosensitivity was determined by MTT assay and quantified by calculating the cell survival rate. Cell-cycle distribution and apotosis rate were monitored by flow cytometry. Results: The survival rate of SMMC-7721-E1A was significantly lower than that of SMMC-7721 cell. Apoptosis rate of SMMC-7721-E1A group was significantly higher than that of SMMC-7721group (P<0.01).The ratio of S stage in cell cycle of SMMC-7721-E1A was significantly lower than that in SMMC-7721 cell. The ratio of G2/M stage in cell cycle of SMMC-7721-E1A was significantly higher than that in SMMC-7721 cell (P<0.01). Conclusion: PEI could transfect E1A gene into hepatic carcinoma cells PEI-mediated E1A could effectively enhance radiosensitivity of hepatic carcinoma cells which may be related to its effects on apoptosis promoting leading to S phase suppression and G2/M phase arrest.  相似文献   
56.
Withaferin A (WA) is a naturally occurring steroidal lactone with proven cancer chemopreventive activity in preclinical models of different cancers including prostate adenocarcinoma. Previously we compared the RNA-seq data from control and WA-treated 22Rv1 human prostate cancer cells to identify mechanistic targets of this phytochemical. The Gene Ontology pathway analysis of the RNA-seq data revealed significant upregulation of genes associated with autophagy upon WA treatment in 22Rv1 cells. In this study, we extended these findings to investigate the mechanism underlying WA-induced autophagy. Initially, we confirmed autophagy induction by WA treatment by transmission electron microscopy using three prostate cancer cell lines (LNCaP, 22Rv1, and PC-3). Fourteen common genes altered by 8- and 16-hour exposure to WA were identified from human autophagy PCR array and these results were consistent with the RNA-seq data. Two key autophagy markers (LC3BII and SQSTM1) were robustly increased in WA-exposed LNCaP, 22Rv1, and PC-3 cells as determined by immunoblotting, and this effect was elevated in the presence of autophagy inhibitor bafilomycin A1 (BafA1). BafA1 treatment augmented WA's cytotoxicity and subsequently its proapoptotic potential. WA treatment induced GABARAPL1 (ATG8L) protein expression in all three cell lines and its knockdown by RNA interference attenuated WA-mediated apoptosis. WA-induced autophagy was not affected in the presence of an antioxidant (EUK134). Taken together, the present study reveals that WA-mediated autophagy is cytoprotective and mediated by GABARAPL1.  相似文献   
57.
目的:探讨内镜活检胃癌组织中黏蛋白3A(MUC3A)、黏蛋白13(MUC13)表达及与病理参数和预后的关系。方法:选取2013年1月至2014年12月南阳市中心医院肿瘤科收治的接受内镜活检的116例患者胃癌组织和癌旁正常组织进行分析,采用免疫组织化学法检测所有组织样本中MUC3A,MUC13表达,观察二者表达情况,并分析二者与临床病理参数及预后的关系。结果:胃癌患者组织MUC3A,MUC13阳性率分别为68.97%和66.38%,高于正常组织的32.76%和7.76%(P<0.05);胃癌组织中MUC3A,MUC13表达与年龄、性别、肿瘤大小无关(P>0.05),与组织分化、浸润深度、TNM分期、淋巴结转移有关(P<0.05);随访5年结果显示:胃癌组织中MUC3A阳性患者中位生存时间为(40.50±1.95)个月,低于阴性患者的(48.67±2.51)个月(P<0.05),MUC3A阳性患者预后5年生存率为32.50%,低于阴性患者的55.56%(P<0.05);MUC13阳性患者中位生存时间为(38.52±1.92)个月,低于阴性患者的(49.06±2.71)个月(P<0.05),MUC13阳性患者预后5年生存率为30.00%,低于阴性患者的61.11%(P<0.05);COX多因素回归分析显示:TNM分期,淋巴结转移,MUC3A,MUC13是影响胃癌预后的独立危险因素(P<0.05)。结论:MUC3A,MUC13在胃癌组织中呈高表达,且与临床病理参数及预后密切相关,二者均有望作为判定胃癌发生发展及预后评估的参考指标。  相似文献   
58.
Solution‐processable poly(dibenzalacetone) and poly(dibenzalcyclohexanone) are prepared by the condensation of 1,4‐dialkoxy‐bisbenzaldehyde and acetone/cyclohexanone using classic Claisen–Schmidt condensation. The prepared polymers are readily soluble in common organic solvents due to the presence of alkoxy chains present on the aromatic ring. The availability of α,β‐unsaturated ketone on the backbone is readily functionalized with hydrazine hydrate to obtain poly(pyrazoline acetate), a nonconjugated polymer on the backbone, which shows enhanced emission characteristics on comparison with the pristine polymer and small molecule analogues. The highest occupied molecular orbital–lowest unoccupied molecular orbital (HOMO–LUMO) of levels of poly(pyrazolines) has a band gap of 1.54 eV as calculated from cyclic voltammetry and UV–vis studies. Uniform thin film is obtained by spin casting as 1% solution on chlorobenzene and annealing under vacuum. Atomic force microscopy analysis shows fine morphology of the thin film. I–V characterization of the film shows low turn‐on voltage of 5.3 V. HOMO–LUMO is calculated by density functional theory and the result suggests that these molecules have great potential toward polymer organic light‐emitting diode applications.  相似文献   
59.
The innate immune response generated against influenza infection is critical for the inhibition of viral dissemination. The trachea contains different types of innate immune cells that protect the respiratory tract from pathogen invasion. Among them, γδ T cells have the ability to rapidly generate large amounts of pro-inflammatory cytokines to preserve mucosal barrier homeostasis during infection. However, little is known about their role during the early phase of influenza infection in the airways. In this study, we found that, early after infection, γδ T cells are recruited and activated in the trachea and outnumber αβ T cells during the course of the influenza infection that follows. We also showed that the majority of the recruited γδ T cells express the Vγ4 TCR chain and infiltrate in a process that involves the chemokine receptor CXCR3. In addition, we demonstrated that γδ T cells promote the recruitment of protective neutrophils and NK cells to the tracheal mucosa. Altogether, our results highlight the importance of the immune responses mediated by γδ T cells.  相似文献   
60.
AIM: To test our hypothesis that activation of protein kinase A(PKA) signal pathway by β-adrenergic agonist plays an important role in the protecting of cultured retinal pigment epithelial(RPE) cells against the hydroxychloroquine(HCQ) toxicity. METHODS: Cultured human RPE cells were treated with 1) HCQ, 2) HCQ with salbutamol(a β2-adrenergic receptor agonist), and 3) HCQ with salbutamol and a PKA inhibitor, and compared these to 4) untreated cells(controls). After treated for 24 h, cell vacuolation, cells viability, PKA and PKA kinase activity levels were determined by the measurement of the size of vacuoles using Image J software, the cell counting with a dye-exclusion testing, Western blot and PKA kinase detection, respectively. RESULTS: Cell vacuolation and cell death of cultured RPE cells were significantly increased by the treatment of HCQ. Salbutamol significantly elevated PKA and PKA activity levels and this was associated with the inhibition of the vacuolation and cell death. The PKA inhibitor significantly decreased the PKA levels and eliminated the protective effects of salbutamol on HCQ-treated RPE cells. CONCLUSION: The PKA pathway plays an important role in the protective effects of β2-adrenergic agonist on the RPE cells against HCQ toxicity. These findings reveal a novel potential strategy against HCQ retinopathy by treatment with PKA activating medications.  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