全文获取类型
收费全文 | 3731篇 |
免费 | 223篇 |
国内免费 | 100篇 |
专业分类
耳鼻咽喉 | 110篇 |
儿科学 | 54篇 |
妇产科学 | 47篇 |
基础医学 | 692篇 |
口腔科学 | 71篇 |
临床医学 | 387篇 |
内科学 | 920篇 |
皮肤病学 | 90篇 |
神经病学 | 252篇 |
特种医学 | 250篇 |
外科学 | 296篇 |
综合类 | 29篇 |
现状与发展 | 1篇 |
预防医学 | 133篇 |
眼科学 | 44篇 |
药学 | 364篇 |
中国医学 | 54篇 |
肿瘤学 | 260篇 |
出版年
2023年 | 11篇 |
2022年 | 80篇 |
2021年 | 120篇 |
2020年 | 55篇 |
2019年 | 80篇 |
2018年 | 113篇 |
2017年 | 68篇 |
2016年 | 100篇 |
2015年 | 140篇 |
2014年 | 155篇 |
2013年 | 204篇 |
2012年 | 308篇 |
2011年 | 303篇 |
2010年 | 223篇 |
2009年 | 172篇 |
2008年 | 237篇 |
2007年 | 220篇 |
2006年 | 174篇 |
2005年 | 160篇 |
2004年 | 137篇 |
2003年 | 124篇 |
2002年 | 102篇 |
2001年 | 100篇 |
2000年 | 76篇 |
1999年 | 58篇 |
1998年 | 59篇 |
1997年 | 45篇 |
1996年 | 44篇 |
1995年 | 28篇 |
1994年 | 26篇 |
1993年 | 24篇 |
1992年 | 21篇 |
1991年 | 20篇 |
1990年 | 27篇 |
1989年 | 36篇 |
1988年 | 41篇 |
1987年 | 28篇 |
1986年 | 23篇 |
1985年 | 19篇 |
1984年 | 9篇 |
1983年 | 11篇 |
1982年 | 9篇 |
1981年 | 7篇 |
1980年 | 7篇 |
1978年 | 6篇 |
1977年 | 12篇 |
1976年 | 6篇 |
1975年 | 5篇 |
1973年 | 7篇 |
1968年 | 4篇 |
排序方式: 共有4054条查询结果,搜索用时 15 毫秒
31.
We report a case of papillary carcinoma arising in a thyroglossal duct cyst, presenting with an anterior neck mass of a 31-year-old woman. The tumor was judged to be a primary lesion on the basis of intraoperative examination of the thyroid and pathologic findings of the mass. One year later, a small nodular mass in the left thyroid gland and lymph node enlargement of the right cervical lymph node were noted by follow-up imaging studies. Total thyroidectomy, right modified radical neck dissection and central neck dissection were performed. The thyroid gland revealed nodular hyperplasia without evidence of malignancy. On the other hand, the dissected neck lymph nodes revealed metastatic papillary carcinoma. Taken together, these findings suggested the tumor was a primary papillary carcinoma arising in the thyroglossal duct cyst. 相似文献
32.
Ae Kyung Park Il-Hwan Kim Junyoung Kim Jeong-Min Kim Heui Man Kim Chae young Lee Myung-Guk Han Gi-Eun Rhie Donghyok Kwon Jeong-Gu Nam Young-Joon Park Jin Gwack Nam-Joo Lee SangHee Woo Jin Sun No Jaehee Lee Jeemin Ha JeeEun Rhee Cheon-Kwon Yoo Eun-Jin Kim 《Osong Public Health and Research Perspectives》2021,12(1):37
Since a novel beta-coronavirus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was first reported in December 2019, there has been a rapid global spread of the virus. Genomic surveillance was conducted on samples isolated from infected individuals to monitor the spread of genetic variants of SARS-CoV-2 in Korea. The Korea Disease Control and Prevention Agency performed whole genome sequencing of SARS-CoV-2 in Korea for 1 year (January 2020 to January 2021). A total of 2,488 SARS-CoV-2 cases were sequenced (including 648 cases from abroad). Initially, the prevalent clades of SARS-CoV-2 were the S and V clades, however, by March 2020, GH clade was the most dominant. Only international travelers were identified as having G or GR clades, and since the first variant 501Y.V1 was identified (from a traveler from the United Kingdom on December 22nd, 2020), a total of 27 variants of 501Y.V1, 501Y.V2, and 484K.V2 have been classified (as of January 25th, 2021). The results in this study indicated that quarantining of travelers entering Korea successfully prevented dissemination of the SARS-CoV-2 variants in Korea. 相似文献
33.
34.
Chae HJ Kim HR Lee WG Kwak YK Kim WH Hong ST Cho GH Kim JS Chae SW 《Immunopharmacology and immunotoxicology》2005,27(2):211-232
Combined radiotherapy and chemotherapy have represented major advance in the therapeutic management of cancer therapy. Anthracycline antineoplastic agents are limited by a high incidence of severe and usually irreversible cardiac toxicity, the cause of which remains controversial. When the primary cardiomyocytes isolated from neonatal rats were preirradiated by γ-ray, the cells were highly resistant to adriamycin-induced apoptosis. This study shows that irradiation inhibited apoptosis by enhancing Bcl-2, attenuating Bax induction, and preventing collapse of mitochondrial membrane potential (ΔΨ), cytochrome c release into cytoplasm and caspase-3, -6 and -9 activations.
In addition, the preirradiation stimulated the activity of manganese-superoxide dismutase (Mn-SOD) and the expression of Mn-SOD mRNA and protein. Adriamycin decreased Mn-SOD activity but did not change the activity of copper/zinc (Cu/Zn)-SOD under either pre- or nonirradiated condition. Phosphothioate-linked antisense against Mn-SOD, which specifically knocked down the activity of Mn-SOD but not that of Cu/Zn-SOD, reversed irradiation-induced protective effect in adriamycin-exposed cardiomyocytes. These data suggest that the irradiation-induced expression of Mn-SOD plays an important role in irradiation-mediated protection in adriamycin-exposed rat ventricular cardiomyocytes. 相似文献
In addition, the preirradiation stimulated the activity of manganese-superoxide dismutase (Mn-SOD) and the expression of Mn-SOD mRNA and protein. Adriamycin decreased Mn-SOD activity but did not change the activity of copper/zinc (Cu/Zn)-SOD under either pre- or nonirradiated condition. Phosphothioate-linked antisense against Mn-SOD, which specifically knocked down the activity of Mn-SOD but not that of Cu/Zn-SOD, reversed irradiation-induced protective effect in adriamycin-exposed cardiomyocytes. These data suggest that the irradiation-induced expression of Mn-SOD plays an important role in irradiation-mediated protection in adriamycin-exposed rat ventricular cardiomyocytes. 相似文献
35.
As shown earlier p-XSC inhibits DMBA-induced mammary cancer in female CD rats. This inhibition is due, in part, to inhibition of DMBA-DNA adduct formation in the target organ. We have now utilized the DMBA-DNA binding assay to evaluate the chemopreventive potential of positional isomers of XSC (o-, m- and p-XSC) applied at selenium doses of 5 and 15 ppm; p-XTC, the sulfur analog of p-XSC, was used at an equimolar dose to determine whether selenium is required for the observed inhibitory effect. Selenium and sulfur compounds were administered in a semipurified high-fat diet (23.5% corn oil). Rats were fed for 1 week prior to oral administration of a single dose of [H-3]DMBA (5 mg/rat); animals were sacrificed 24 h later, DNA was isolated from mammary fat pads and levels of total binding were determined. All agents produced a dose-dependent inhibition of DMBA-DNA binding in the mammary tissues. The inhibition at 5, respectively 15 ppm Se in the form of XSC isomers and at 30 mu M, respectively 90 mu M in the form of p-XTC was: o-XSC (27%, 42%); m-XSC (32%, 47%); p-XSC (22%, 29%); and p-XTC (10%, 20%); only inhibition by dietary o-XSC and m-XSC at 15 ppm Se reached statistical significance (p<0.05). Thus, o-XSC and m-XSC equally inhibit DMBA-DNA binding and both are better inhibitors than p-XSC; the latter appears to be slightly more effective than its sulfur analog p-XTC. Clearly, the structure of the selenium-containing compound is a critical factor in determining the extent of inhibition of DMBA-DNA binding. The described short-term in vivo assay may constitute the basis for future selection of chemopreventive agents in the rat mammary tumor model system. 相似文献
36.
Yamazaki Hiroshi; Mimura Mayumi; Oda Yoshimitsu; Gonzalez Frank J.; El-Bayoumy Karam; Chae Young-Heum; Guengerich F.Peter; Shimada Tsutomu 《Carcinogenesis》1994,15(3):465-470
In order to address the hypothesis that 6-aminochrysene (6-AC)is converted to genotoxic products by cytochrome P450 enzymesvia two activation pathways (N-hydroxylation and epoxidation),the activation of 6-AC and trans-l,2-dihydro-l,2-dihydroxy-6-aminochrysene(6-AC-diol) to genotoxic metabolites was examined in rat andhuman liver microsomal cytochrome P450 enzymes using Salmonellatyphimurium TA1535/pSK1002 and TA1535/pSK1002/pNM12 (NM2009)as tester strains. The latter bacteria, an O-acetyl-transferase-overexpressingstrain, was highly sensitive to metabolites derived from activationof 6-AC, but not those from 6-AC-diol, using liver microsomesfrom phenobarbital-treated rats or a reconstituted monooxygenasesystem containing P4502B1 or -2B2, thus suggesting the rolesof P450 and acetyltransferase systems in the activation process.6-AC-diol, on the other hand, was activated very efficientlyby liver microsomes prepared from ß-naphthoflavone-treatedrats or a reconstituted system containing P4501A1 or -1A2; theactivation reaction is considered to proceed through diol-epoxideformation. The contribution of rat P4501A enzymes towards activationof 6-AC-diol was confirmed by the inhibitory effects on theactivation process of -naphthoflavone, a specific inhibitorof P4501 A-related activities, and antibodies raised againstpurified P4501A1 and -1A2. In humans, P4501A2 was found to bethe major enzyme involved in the activation of 6-AC-diol togenotoxic metabolites while the parent compound 6-AC was activatedmainly by P4503A4. Experiments using recombinant P450 proteinsexpressed in human lymphoblastoid cells lines showed that humanP4501A1 could also activate 6-AC-diol to reactive metabolitesat almost the same rate measured with P4501A2. In addition,P4502B6 was found to efficiently catalyze the activation of6-AC to genotoxic metabolites, and P4503A4 was active in theactivation of 6-AC-diol as well as 6-AC. Addition of purifiedrat epoxide hydrolase to the incubation mixture containing purifiedrat P4501A1 or microsomes expressing human P4501A1 caused inhibitionof activation of 6-AC-diol. These results suggest the existenceof different enzymatic activation pathways for 6-AC and 6-AC-diol.The former carcinogen may be N-hydroxylated principally by P4502Benzymes in rats and P4503A4 and -2B6 in humans and activationto its ultimate metabolites may proceed through esterificationof the N-hydroxy metabolites by an N-acetyltransferase. The6-AC-diol is metabolized to its ultimate diolepoxide productby P4501A enzymes in rat and human liver microsomes. P4503A4(humans) and P4503A2 (rats) may also contribute to some extentin the activation of 6-AC-diol, albeit at lower rates than thoseof P4501A enzymes. 相似文献
37.
Expression of the active urease of the enterobacterium, Klebsiella aerogenes, requires the presence of the accessory genes (ureD, ureE, ureF, and ureG) in addition to the three structural genes (ureA, ureB, and ureC). These accessory genes are involved in functional assembly of the nickel-metallocenter for the enzyme. Characterization of ureF gene has been hindered, however, since the UreF protein is produced in only minute amount compared to other urease gene products. In order to overexpress the ureF gene, a recombinant pMAL-UreF plasmid was constructed from which the UreF was produced as a fusion with maltose-binding protein. The MBP-UreF fusion protein was purified by using an amylose-affinity column chromatography followed by an anion exchange column chromatography. Polyclonal antibodies raised against the fusion protein were purified and shown to specifically recognize both MBP and UreF peptides. The UreF protein was shown to be unstable when separated from MBP by digestion with factor Xa. 相似文献
38.
Yoon KH Ha HK Kim CG Roh BS Yun KJ Chae KM Lim JH Auh YH 《AJR. American journal of roentgenology》2000,175(4):1135-1139
OBJECTIVE. We describe the CT and pathologic features of malignant papillary neoplasms of the intrahepatic bile ducts in 15 patients. CONCLUSION. CT is a useful technique for revealing intraductal lesions, although the findings are nonspecific and variable. When intraductal masses or nodules are seen with localized dilatation of the intrahepatic bile ducts on CT scans, malignant papillary neoplasms of the intrahepatic bile ducts should be included in the differential diagnosis. 相似文献
39.
Chae YB Lee JS Park HJ Park IH Kim MM Park YH Kim DS Lee JH 《Environmental toxicology and pharmacology》2012,34(2):263-271
Advanced adipose-derived stem cell protein extracts (AAPE) were used instead of live stem cells to investigate their effect on oxidative stress and matrix metalloproteinases (MMPs) related to tissue repair in human dermal fibroblasts (HDFs). In this study, it was observed that AAPE at 2μg/ml specifically exhibited scavenging activity of hydrogen peroxide and reducing power. The inhibitory effect of AAPE at 2μg/ml on MMP-2 activity was increased in the presence of phorbol myristate acetate (PMA). In the absence of PMA, AAPE significantly enhanced activities of MMP-1 and MMP-2 in HDFs, respectively. However, the level of MMP-1 expression was decreased in a dose dependent manner by AAPE. In addition, while the level of extracellular signal-regulated kinases 1 (ERK1) activation was reduced in the presence of AAPE compared to blank, the level that of ERK2 activation was not changed. The expression level of c-Fos, a part of activator protein-1 (AP-1), was increased in nucleus of HDFs. These results reveal that activation of MMPs in the presence of AAPE was increased via AP-1 in HDFs, suggesting that AAPE can be a potential candidate for tissue repair. 相似文献
40.