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   4589篇
  免费   563篇
  国内免费   72篇
耳鼻咽喉   31篇
儿科学   85篇
妇产科学   87篇
基础医学   727篇
口腔科学   131篇
临床医学   587篇
内科学   438篇
皮肤病学   53篇
神经病学   239篇
特种医学   84篇
外科学   516篇
综合类   518篇
预防医学   681篇
眼科学   40篇
药学   538篇
  17篇
中国医学   270篇
肿瘤学   182篇
  2024年   16篇
  2023年   73篇
  2022年   188篇
  2021年   202篇
  2020年   189篇
  2019年   183篇
  2018年   223篇
  2017年   217篇
  2016年   170篇
  2015年   162篇
  2014年   295篇
  2013年   359篇
  2012年   245篇
  2011年   258篇
  2010年   209篇
  2009年   181篇
  2008年   169篇
  2007年   188篇
  2006年   174篇
  2005年   164篇
  2004年   127篇
  2003年   123篇
  2002年   108篇
  2001年   74篇
  2000年   53篇
  1999年   48篇
  1998年   45篇
  1997年   59篇
  1996年   46篇
  1995年   54篇
  1994年   52篇
  1993年   44篇
  1992年   44篇
  1991年   40篇
  1990年   39篇
  1989年   23篇
  1988年   23篇
  1987年   25篇
  1986年   28篇
  1985年   53篇
  1984年   55篇
  1983年   39篇
  1982年   44篇
  1981年   46篇
  1980年   25篇
  1979年   14篇
  1978年   10篇
  1977年   7篇
  1976年   7篇
  1975年   2篇
排序方式: 共有5224条查询结果,搜索用时 0 毫秒
11.
 Rhabdomyosarcoma (RMS) is occasionally found in the female genital tract, and mostly appears as one of the heterologous mesenchymal components in uterine carcinosarcoma designated as malignant mixed müllerian tumour (MMMT). We examined the biological properties of a pure rhabdomyosarcoma (RMS) cell line designated FU-MMT-3, which was newly established from a surgical specimen taken from a patient with uterine MMMT. We also evaluated c-myc and MYCN gene amplification in three RMS cell lines (including FU-MMT-3) derived from three MMMTs by Southern blot analysis. FU-MMT-3 cells were propagated continuously for 57 serial passages over a 2-year period in vitro. FU-MMT-3 was able to produce tumours demonstrating pure RMS in athymic nude mice. Cytogenetically, FU-MMT-3 showed a triploidy pattern, with complex karyotypic abnormalities including trisomy of chromosome 8. All three RMS cell lines, including FU-MMT-3, showed amplification of the c-myc gene (approximately fourfold to eightfold), while no cell lines demonstrated MYCN gene amplification. FU-MMT-3 is considered to provide a useful system for the study of the biological behaviour of RMS in MMMTs. Extra copies of chromosome 8 and c-myc gene amplification may be associated with the rhabdomyoblastic differentiation in MMMT. Received: 7 January 1997 / Accepted: 2 May 1997  相似文献   
12.
We report a patient with graft versus host disease (GVHD) with mixed chimerism (MC). The patient had chronic myelogenous leukemia and received bone marrow transplantation (BMT) from his elder sister. Eighty days after BMT, erythematous lesions appeared on his chest. Histological examination from the skin lesion revealed lymphocytic infiltration into the upper dermis. Eosinophilic necrotic keratinocytes were scattered through the epidermis. Liquefaction degeneration was also recognized. Sicca syndrome appeared from 110 days after BMT. Detection of host origin Y-chromosome-specific DNA by polymerase chain reaction (PCR) method in bone marrow and peripheral blood showed that all bone marrow samples obtained 6 months from BMT were positive for Y-specific DNA, while peripheral blood became positive in the 60th month after BMT. The host origin normal karyotype (46,XY) in the bone marrow samples was identified for the first time in the 60th month after BMT. These results indicate that host-origin hematopoietic cells survived after BMT.  相似文献   
13.
目的:观察美宝湿润烧伤膏在血栓性外痔和陈旧性肛裂切除术后治疗中的疗效。方法:术毕用MEBO纱布条填塞伤口,术后24小时取出纱布条,以后用MEBO涂于伤口内,每日2次,直至痊愈。结果:48例患者无术后伤口疼痛、出血、感染及肛门狭窄。伤口愈合时间短,治愈率高。结论:美宝湿润烧伤膏是血栓性外痔、陈旧性肛裂切除术后良好的局部治疗药物。  相似文献   
14.
Primary malignant mesodermal ovarian sarcomas   总被引:1,自引:0,他引:1  
Primary malignant mesodermal ovarian sarcomas are rare tumors and have a poor prognosis. The disease is usually diagnosed at a late stage and 5-year survivals are uncommon. Most patients are treated with debulking surgery followed by adjuvant chemotherapy. We report ten patients treated at a single institution. All patients underwent surgery and 90% received adjuvant chemotherapy. The median survival was 20 months, and only one patient survived beyond 5 years. Newer treatment strategies are urgently needed in the management of this disease.  相似文献   
15.
16.
目的:总结了痔患者的辨证施护体会,为临床护理工作提供参考。方法:回顾分析了自2001年以来收治的40例痔患者的临床资料。护理诊断及相应措施。结果:本组40例患者,痊愈者28例,好转者10例,病情稳定出院者2例。结论:树立以病人为中心的整体观。实施相应的辨证护理,贯彻以预防为主的方针,可提高痔的治愈率。  相似文献   
17.
N-Alkoxycarbonylaminodicarboxylic acids were reacted in dichloromethane with N-ethyl-N′-(dimethylaminopropyl)carbodiimide hydrochloride, and with methyl chloroformate in the presence of N-methylmorpholine. Removal of secondary products by washing the mixtures with aqueous solutions gave good yields of the pure crystalline internal anhydrides. Anhydrides of N-benzyloxycarbonyl- (Z) and N-9-fluorenylmethoxycarbonyl-(Fmoc) L-glutamic and L-aspartic acids and of N-tert.-butoxycarbonyl-L-aspartic acid were prepared in this way. The compounds were shown to be amenable to normal phase high-performance liquid chromatography (NP-HPLC) on a CN-column using tert.-butanol-hexane as solvent. The products of the reactions of Z- and Fmoc-glutamic acid with hot acetic anhydride were examined by nuclear magnetic resonance and NP-HPLC before and after methanolysis in an attempt to establish if any of the corresponding pyroglutamates were formed. The reaction of Fmoc-chloride with Fmoc-glutamate was examined for the same reason. It is concluded that the side product generated during the reaction of Fmoc-chloride with glutamic acid which is used for analysis of the latter is the N-protected internal anhydride and not the pyroglutamate as reported in the literature.  相似文献   
18.
Analysis of count data from clinical trials using mixed effect analysis has recently become widely used. However, algorithms available for the parameter estimation, including LAPLACE and Gaussian quadrature (GQ), are associated with certain limitations, including bias in parameter estimates and the long analysis runtime. The stochastic approximation expectation maximization (SAEM) algorithm has proven to be a very efficient and powerful tool in the analysis of continuous data. The aim of this study was to implement and investigate the performance of a new SAEM algorithm for application to count data. A new SAEM algorithm was implemented in MATLAB for estimation of both, parameters and the Fisher information matrix. Stochastic Monte Carlo simulations followed by re-estimation were performed according to scenarios used in previous studies (part I) to investigate properties of alternative algorithms (Plan et al., 2008, Abstr 1372 []). A single scenario was used to explore six probability distribution models. For parameter estimation, the relative bias was less than 0.92% and 4.13% for fixed and random effects, for all models studied including ones accounting for over- or under-dispersion. Empirical and estimated relative standard errors were similar, with distance between them being <1.7% for all explored scenarios. The longest CPU time was 95 s for parameter estimation and 56 s for SE estimation. The SAEM algorithm was extended for analysis of count data. It provides accurate estimates of both, parameters and standard errors. The estimation is significantly faster compared to LAPLACE and GQ. The algorithm is implemented in Monolix 3.1, (beta-version available in July 2009).  相似文献   
19.
目的比较从人外周血单核细胞及脐血CD34+细胞诱导树突细胞(DC)的方法及其特性.方法用淋巴细胞分离液分离外周血单个核细胞,贴壁法获得单核细胞;经GM-CSF及IL-4诱导获得DC.磁性活化细胞分选系统(MACS)分选脐血CD34+细胞,以GM-CSF、IL-4、TNF-α、SCF、FL、TPO等细胞因子诱导获得DC.用电镜、普通显微镜观察DC形态;流式细胞仪分析DC表型;同种混合淋巴细胞反应(allo-MLR)观察DC刺激T淋巴细胞增殖的能力.结果外周血单核细胞在因子GM-CSF、IL-4、TNF-α,脐血CD34+细胞在GM-CSF、IL-4、TNF-α、SCF、FL、TPO等因子作用下,可生成DC,并表达相应的DC分化抗原CD14、CD80、CD83、CD86、HLA-DR.脐血CD34+细胞具有较强的扩增能力,经2周诱导,体系细胞数可增加173.8士26.7倍,两种来源的DC均能刺激同种异体淋巴细胞的增殖反应.结论外周血单核细胞与脐血CD34+细胞,在体外均可诱导成DC,并具有相应的DC分化抗原和功能.  相似文献   
20.
Bedu-Addo  Frank K.  Tang  P.  Xu  Y.  Huang  Leaf 《Pharmaceutical research》1996,13(5):710-717
Purpose. The purpose of this study was to investigate polyethyleneglycol(PEG)-phosphatidylethanolamine(PE) conjugate interaction with phospholipid bilayers, in an attempt to explain the dependence of liposome circulation time on formulation. Methods. Differential scanning calorimetry, electron microscopy, dynamic light scattering and NMR were the major methods used in the study. Results. Mixtures of PEG-phospholipid conjugates and phosphatidylcholine existed in three different physical states: a lamellar phase with components exhibiting some miscibility, a lamellar phase with components phase separated, and mixed micelles. Beyond 7 mol% of PEG(l,000–3,000)-dipalmitoyl phosphatidylethanolamine (DPPE), and 11 mol% PEG(5,000)-DPPE in dipalmitoyl phosphatidylcholine (DPPC), a strong tendency towards mixed micelle formation was observed. All concentrations of PEG(12,000)-DPPE and PEG(5,000)-DPPE beyond 8 mol% formed phase separated lamellae with phosphatidylcholine. Decreasing the acyl chain length from C16:0 to C14:0 caused a decrease in tendency towards micelle formation and phase separation. These tendencies increased upon increasing acyl chain length to C18:0. Phase separation was at least partly due to PEG chain-chain interaction. This was supported by an increased fraction of PEG chains exhibiting a fast NMR transverse relaxation in DPPC/PEG(5,000)-DPPE mixtures as compared to that in distearoyl phosphatidylcholine (DSPC)/PEG(5,000)-dioleoyl-PE (DOPE). Conclusions. These phenomena are discussed in relation to both bilayer and steric stabilization of liposomes, and the lack of prolonged circulation with certain formulations is discussed.  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