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   232749篇
  免费   20891篇
  国内免费   10770篇
耳鼻咽喉   2474篇
儿科学   5039篇
妇产科学   2689篇
基础医学   41367篇
口腔科学   6071篇
临床医学   18183篇
内科学   37953篇
皮肤病学   5402篇
神经病学   12094篇
特种医学   4973篇
外国民族医学   124篇
外科学   18359篇
综合类   35784篇
现状与发展   65篇
预防医学   10048篇
眼科学   3939篇
药学   21014篇
  44篇
中国医学   8408篇
肿瘤学   30380篇
  2024年   334篇
  2023年   2973篇
  2022年   4668篇
  2021年   8062篇
  2020年   7237篇
  2019年   7343篇
  2018年   7421篇
  2017年   7706篇
  2016年   8326篇
  2015年   9379篇
  2014年   14179篇
  2013年   15392篇
  2012年   13900篇
  2011年   15370篇
  2010年   12711篇
  2009年   12178篇
  2008年   12549篇
  2007年   12711篇
  2006年   11563篇
  2005年   10411篇
  2004年   9070篇
  2003年   7826篇
  2002年   6437篇
  2001年   5559篇
  2000年   4526篇
  1999年   4047篇
  1998年   3758篇
  1997年   3376篇
  1996年   2966篇
  1995年   2671篇
  1994年   2357篇
  1993年   1943篇
  1992年   1636篇
  1991年   1480篇
  1990年   1194篇
  1989年   1100篇
  1988年   1036篇
  1987年   826篇
  1986年   755篇
  1985年   1197篇
  1984年   1131篇
  1983年   847篇
  1982年   874篇
  1981年   710篇
  1980年   629篇
  1979年   518篇
  1978年   377篇
  1977年   293篇
  1976年   281篇
  1975年   194篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Controlling cellular alignment is critical in engineering intestines with desired structure and function. Although previous studies have examined the directional alignment of cells on the surface (x–y plane) of parallel fibers, quantitative analysis of the cellular alignment inside implanted scaffolds with oriented fibers has not been reported. This study examined the cellular alignment in the x–z and y–z planes of scaffolds made with two layers of orthogonally oriented fibers. The cellular orientation inside implanted scaffolds was evaluated with immunofluorescence. Quantitative analysis of coherency between cell orientation and fiber direction confirmed that cells aligned along the fibers not only on the surface (x–y plane) but also inside the scaffolds (x–z & y–z planes). Our study demonstrated that two layers of orthogonally aligned scaffolds can generate the histological organization of cells similar to that of intestinal circular and longitudinal smooth muscle.  相似文献   
52.
53.
背景与目的:CD44分子是众多肿瘤细胞的标志分子,其表达水平与肿瘤细胞的恶性程度有关。该研究探讨CD44基因中的单核苷酸多态性(single nucleotide polymorphism,SNP)位点与云南汉族人群宫颈癌和非小细胞肺癌(nonsmall cell lung cancer,NSCLC)易感性的相关性。方法:选取了CD44基因中的两个SNP位点rs13347和rs8193,采用TagMan基因分型的方法,分析这两个多态性位点在497例宫颈癌患者和500例健康对照个体以及483例NSCLC患者和471例健康对照个体中的分布特征,并分析CD44基因中的多态性位点与云南汉族人群宫颈癌和NSCLC的相关性。结果:rs13347和rs8193位点等位基因和基因型在宫颈癌组和对照组中的分布频率的差异无统计学意义(P>0.05)。而在NSCLC组和对照组的比较中:rs13347和rs8193位点等位基因在NSCLC组和对照组中的分布频率的差异有统计学意义(P=0.020和P=0.004);这两个位点基因型在NSCLC组和对照组中分布频率的差异有统计学意义(P=0.027和P=0.020);其中rs13347位点等位基因C在NSCLC组中的分布频率显著高于对照组,可能是NSCLC发生的风险因素(OR=1.250,95% CI:1.035~1.509),rs8193位点等位基因C在对照组中的分布频率显著高于NSCLC组,可能是NSCLC发生的保护性因素(OR=0.768,95%CI:0.641~0.921)。单倍型分析结果显示,rs13347C-rs8193T和rs13347T-rs8193C在NSCLC组和对照组中的分布频率差异有统计学意义(P=0.003和0.022);该结果说明单倍型rs13347C-rs8193T可能是云南汉族人群NSCLC发生的风险性因素(OR=1.316,95%CI:1.096~1.579)。结论:CD44基因中的两个SNP位点rs13347和rs8193可能与云南汉族人群宫颈癌发病风险无关,而可能与云南汉族人群NSCLC具有相关性。  相似文献   
54.

Background

Refractory acute myeloid leukemia (AML) includes AML includes failure of disease to respond to standard induction chemotherapy, relapse within 6 months after first CR, and 2 or more relapses. The outcome of these patients is usually very poor; only a small proportion can be rescued by allogenic hematopoietic stem-cell transplantation (allo-HSCT). The aim of this study was to evaluate the efficacy and feasibility of allo-HSCT in patients with refractory AML.

Patients and Methods

We retrospectively analyzed the clinical outcome of 91 patients who were diagnosed with treatment-refractory AML at Hacettepe University Hospital between January 2002 and June 2018. Patients' disease status included refractory AML, defined as failure to respond to standard induction chemotherapy and relapse within 6 months after first complete remission.

Results

The median follow-up was 12 months (range, 0.5-184 months) for the entire group. Kaplan-Meier estimates of the 3-year overall survival for patients who underwent allo-HSCT and patients who received only salvage chemotherapy were 67% and 12%, respectively. Additionally, the Kaplan-Meier estimates of 5-year overall survival for patients who underwent allo-HSCT and patients who received only salvage chemotherapy were 44% and 4%, respectively (P < .001). Complete remission was obtained in 25 patients (83.3%) who underwent allo-HSCT; however, the disease of only 3 patients (3.8%) exhibited complete response after salvage chemotherapy.

Conclusion

Allo-HSCT is still the best-known treatment option with curative potential in patients with treatment-refractory AML. Therefore, all efforts should be made in an attempt to find a suitable matched donor in order to perform allo-HSCT.  相似文献   
55.
目的观察叶酸和维生素B12对绝经后骨质疏松症妇女的骨代谢及同型半胱氨酸水平的影响。方法 80例绝经后骨质疏松症妇女参加研究。所有参与者随机接受叶酸和维生素B12(n=40)或安慰剂(n=40)治疗。在干预前的基线及干预后3个月和6个月,测量两组患者血清同型半胱氨酸、维生素B12和骨代谢标志物的水平。结果治疗前,两组患者血清同型半胱氨酸、维生素B12和骨代谢标志物水平比较差异无统计学意义(P0.05)。治疗后,两组患者同型半胱氨酸均下降,但比较差异无统计学意义(P0.05)。6个月后各组间血清维生素B12、骨钙素、CTX的变化均有显著改变且差异有统计学意义(P0.05)。结论绝经后骨质疏松症妇女补充叶酸和维生素B12可以一定程度改善同型半胱氨酸及骨代谢指标水平。  相似文献   
56.
《Vaccine》2020,38(50):7916-7927
Respiratory syncytial virus (RSV) is the major cause of acute lower respiratory illness in children of less than 5 years of age which usually results in hospitalization or even in death. Vaccine development is hampered in consequence of a failed vaccine trial with fatalities in the 1960s. Even though research has been more focused on the RSV fusion protein in its pre-fusion conformation, maternal vaccination with post-fusion protein (post F) was considered as a promising vaccine strategy for passive immunization of babies, because post F preserves very potent neutralizing epitopes. We extensively analyzed post F-binding B cell receptor (BCR) repertoires of three vaccinees who received a post F-subunit vaccine in the context of a first-in-human, Phase 1, randomized, observer-blind, placebo-controlled clinical trial (ClinicalTrials.gov Identifier: NCT02298179). In order to compare the vaccine-induced BCR repertoires with BCR repertoires induced by natural infection, we also analyzed pre F- and post F-binding BCRs isolated from a healthy blood donor with relatively high F-binding memory B cell (MBC) frequencies. Analysis of the vaccine-induced repertoires revealed that preferentially VH4-encoded BCRs were expanded in response to vaccination. Estimation of antigen-driven selection further demonstrated that expanded BCRs accumulated positively selected replacement mutations which substantiated the hypothesis that post F-vaccination induces diversification of VH4-encoded BCRs in germinal centers. Comparison of the vaccine-induced BCR repertoires with clonally related pre and post F-binding BCRs of the healthy blood donor suggested that the vaccine expanded pre/post F cross-reactive MBCs. Interestingly, several vaccine-induced BCRs shared stereotypic VDJ gene junctions with known neutralizing Abs. Once expressed for functional characterization, the selected monoclonal Abs demonstrated the predicted neutralization activities in plaque reduction neutralization assays indicating that the post F-vaccine induced expansion of neutralizing BCRs.  相似文献   
57.
58.
摘要〓目的〓研究四腔水箱在腹外科腔镜电凝线擦拭法清洗消毒中的应用效果。方法〓通过目测法和ATP生物荧光法,对本研究的四腔水箱用于腹外科腔镜电凝线的清洗效果进行评价。结果〓传统治疗碗清洗的206件腔镜电凝线清洗质量合格率为86.4%,四腔水箱清洗的206件腹腔镜电凝线清洗质量合格率为94.6%,差异有统计学意义(P<0.01)。用四腔水箱清洗腔镜电凝线擦拭过程中的护理人员满意度较高。结论〓四腔水箱可提高腹外科腔镜电凝线清洗质量和护理人员满意度。  相似文献   
59.
Nanocrystalline platinum with different morphologies is synthesized via electrochemical deposition technique. The nucleation mechanism and its structural effect over the electrodeposited Pt on carbon electrodes have been systematically studied. Powder X-ray diffraction, X-ray photoelectron spectroscopy, and field-emission scanning electron microscopy are employed to study nucleation, oxidation states, and Pt structure growth on a carbon electrode. This study reports significant development of Pt metal nanoparticles with different morphologies such as a sphere, flower, core-flower, and rod-like structure directly fabricated on carbon electrode while tuning the deposition parameters such as current density, time, temperature, pH during the deposition process. The proposed electrochemical route represents a superior fabrication procedure for large-scale electrode fabrication compared to a conventional method for preparing membrane electrode assemblies for fuel cell stacks.  相似文献   
60.
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