全文获取类型
收费全文 | 142039篇 |
免费 | 13901篇 |
国内免费 | 10856篇 |
专业分类
耳鼻咽喉 | 1425篇 |
儿科学 | 1384篇 |
妇产科学 | 1315篇 |
基础医学 | 16109篇 |
口腔科学 | 2357篇 |
临床医学 | 18967篇 |
内科学 | 20227篇 |
皮肤病学 | 1682篇 |
神经病学 | 7263篇 |
特种医学 | 5330篇 |
外国民族医学 | 84篇 |
外科学 | 14275篇 |
综合类 | 26613篇 |
现状与发展 | 51篇 |
一般理论 | 7篇 |
预防医学 | 10033篇 |
眼科学 | 3886篇 |
药学 | 15103篇 |
137篇 | |
中国医学 | 9136篇 |
肿瘤学 | 11412篇 |
出版年
2024年 | 485篇 |
2023年 | 2169篇 |
2022年 | 6010篇 |
2021年 | 7746篇 |
2020年 | 5915篇 |
2019年 | 4838篇 |
2018年 | 5143篇 |
2017年 | 4708篇 |
2016年 | 4377篇 |
2015年 | 6746篇 |
2014年 | 8326篇 |
2013年 | 7631篇 |
2012年 | 10828篇 |
2011年 | 11909篇 |
2010年 | 7795篇 |
2009年 | 6264篇 |
2008年 | 7690篇 |
2007年 | 7494篇 |
2006年 | 7119篇 |
2005年 | 6926篇 |
2004年 | 4556篇 |
2003年 | 4210篇 |
2002年 | 3503篇 |
2001年 | 3044篇 |
2000年 | 3117篇 |
1999年 | 3184篇 |
1998年 | 2098篇 |
1997年 | 2116篇 |
1996年 | 1640篇 |
1995年 | 1553篇 |
1994年 | 1330篇 |
1993年 | 823篇 |
1992年 | 1032篇 |
1991年 | 834篇 |
1990年 | 689篇 |
1989年 | 661篇 |
1988年 | 545篇 |
1987年 | 473篇 |
1986年 | 421篇 |
1985年 | 317篇 |
1984年 | 156篇 |
1983年 | 119篇 |
1982年 | 69篇 |
1981年 | 78篇 |
1980年 | 48篇 |
1979年 | 57篇 |
1978年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1965年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
无症状性脑梗死患者的心理功能测评 总被引:6,自引:0,他引:6
随着高敏度的脑成像技术如CT、MRI在临床的广泛应用 ,发现了许多临床上无明显症状、体征或症状、体征与既往卒中史不相关的梗死灶 ,称之为无症状性脑梗死 (asymptomaticinfarct)或静止性脑梗死(silentcerebralinfarction ,SCI)。虽然这些病人经传统的神经系统检查未发现明显的异常 ,但有学者认为他们存在明显的认知功能障碍、精细运动障碍及情感障碍等。本文对 38例SCI及 30例对照组进行了认知功能、记忆、精细运动、感知觉及情感等方面的评价 ,有利于SCI以及血管性痴呆的早期防… 相似文献
992.
为了建立莱姆病人工宿主模型进行实验传播研究,用从我国全沟硬蜱分离的莱姆病螺旋体Borrelia garinii CHNM4人工感染4种实验动物.结果表明,以0.1×106条/mL的剂量皮下注射3日龄昆明小鼠是比较理想的方案.由此建立的动物模型既能用作全沟硬蜱的血源动物,又能在15天内保持所感染螺旋体对全沟硬蜱的感染力,可作为人工宿主动物模型. 相似文献
993.
The effect of residual stress on the dissolution of hydroxyapatite (HA) coatings was investigated. The examined coatings of 80-, 110-, and 200-microm thickness were prepared by a plasma-spraying technique under identical conditions. Residual stresses in the coatings were measured with a hole-drilling method. Dissolution of the coatings was monitored along with an examination of the phase composition. The results showed that both tensile residual stress and amorphous HA existed throughout the entire depth of the coatings and tended to increase from the surface to the interface of the coating and substrate. The thicker the coatings were, the higher the maximum residual stress was. Correspondingly, the pH value and calcium concentration of the solutions tended to increase with the coating thickness. On the basis of these phenomena and a thermodynamic analysis of the dissolution of the HA subjected to stresses, we concluded that besides structural effects, residual stress was also an important intrinsic factor influencing dissolution of HA coatings, and the dissolution can be delayed or even restrained by compressive residual stress. 相似文献
994.
NaoXinQing (NXQ) is a patented and approved drug of Traditional Chinese Medicine that has been used for years for the treatment of syndrome of apoplexy, but the underlying mechanism remains unclear. The present study is designed to investigate the effects of NXQ on hydrogen peroxide (H(2)O(2))-induced cell damage in NG108-15 cells. Exposure to H(2)O(2) induces apoptosis-like cell injury. Preincubation of cells with NXQ alleviated H(2)O(2)-induced cell injury and apoptosis. This herb medicine also improves redox imbalance in cells under the exposure of H(2)O(2) as indicated by the attenuation in the reduction of activities of intracellular endogenous antioxidants, glutathione and glutathione peroxidase as well as catalase, and by the decrease in the leak of lactate dehydrogenase and the accumulation of malondialdehyde. These results indicate that NXQ significantly protects NG108-15 cells against H(2)O(2) challenge by improving redox imbalance and inhibiting apoptosis, which might represent mechanisms underlying its potential usage in the prevention and treatment of syndrome of apoplexy. 相似文献
995.
检测切应力作用下肾近端小管上皮细胞纤溶酶原激活物tPA和uPA mRNA表达的变化,探讨糖尿病肾病早期小管间质细胞外基质重塑的可能机制.用5 dyn/cm2和10 dyn/cm2的切应力处理肾近端小管上皮细胞(NRK-52E),作用时间分别为1、3和6 h,用RT-PCR法检测tPA及uPA mRNA的表达.结果表明:切应力呈大小和时间依赖性下调肾小管上皮细胞tPA及uPA mRNA的表达.在糖尿病肾病早期,高滤过引起的切应力增加可抑制肾近端小管上皮细胞tPA和uPA mRNA表达,导致肾小管间质纤维蛋白溶解活性降低,参与小管间质细胞外基质的重塑. 相似文献
996.
以腓动脉终末穿支为蒂的皮瓣应用解剖 总被引:27,自引:7,他引:27
徐胜 《中国临床解剖学杂志》1990,8(2):88-91
在33侧成人标本上,观察了以腓动脉的终末穿支为蒂的外踝上皮瓣血供。腓动脉终末穿支在外踝上方5.9cm 处,穿出骨间膜,外径为1.7mm,本干长为0.7cm,分为升支和降支、有91%的个体,以穿动脉的升支为蒂,设计为外踝上皮瓣:以穿动脉的降支为蒂,设计为足外侧皮瓣。在9%的个体中,腓动脉穿支细小,不能作为皮瓣的血管蒂,只能改用外踝前动脉升支为蒂的外踝上皮瓣. 相似文献
997.
998.
建立毛细管电泳分离分析多巴胺和 5一羟色胺的方法。采用自由区带电泳法 (CZE) ,4 0mmol/L硼砂缓冲液 2 0PSI气压进样 5s ,定电流 75 μA分离 10min ,二极管阵列PDA检测器检测 ,应用 2 0 0nm检测波长 ,结果显示两种物质完全分离。 相似文献
999.
Jingqi Liu Ligang Chen Jinshui Pan Meiya Chen Jingping Zhou Fei Zhou Peizhong Chen Yang Song 《Archives of Medical Science》2021,17(1):142
IntroductionHepatocellular carcinoma (HCC) is one of the most common cancers worldwide. Despite the therapeutic advances in HCC in the past few decades, the mortality rate of HCC is still high. Hepatitis C (HCV) infection is one of the major etiological risk factors of HCCs. However, the underlying mechanisms of HCV-induced hepatocarcinogenesis remain largely unclear.Material and methodsOur study represented the comprehensive analysis of differentially expressed lncRNAs in HCV-positive HCC for the first time by analyzing the public dataset . Co-expression network and gene ontology (GO) analysis revealed the functions of those differentially expressed lncRNAs.ResultsWe identified 256 upregulated lncRNAs and 198 downregulated lncRNAs in HCV- positive HCC compared to the normal liver tissues. Co-expression network and GO analysis showed that these lncRNAs were involved in regulating metabolism, energy pathways, proliferation and the immune response. Seven lncRNAs (LOC341056, CCT6P1, PTTG3P, LOC643387, LOC100133920, C3P1 and C22orf45) were identified as key lncRNAs and co-expressed with more than 100 differentially expressed genes (DEGs) in HCV-related HCC. Kaplan-Meier analysis showed that higher expression levels of LOC643387, PTTG3P, LOC341056, CCT6P1 and lower expression levels of C3P1 and C22orf45 were associated with shorter survival time in the TCGA dataset.ConclusionsWe believe that this study can provide novel potential therapeutic and prognostic biomarkers for HCV-positive HCC. GSE17856相似文献
1000.
Hengxing Lu Jun Liu Tao Feng Zihang Guo Yunjun Yin Fei Gao Gengsheng Cao Xuguang Du Sen Wu 《Genome research》2021,31(5):900
Targeted mutagenesis in model organisms is key for gene functional annotation and biomedical research. Despite technological advances in gene editing by the CRISPR-Cas9 systems, rapid and efficient introduction of site-directed mutations remains a challenge in large animal models. Here, we developed a robust and flexible insertional mutagenesis strategy, homology-independent targeted trapping (HIT-trapping), which is generic and can efficiently target-trap an endogenous gene of interest independent of homology arm and embryonic stem cells. Further optimization and equipping the HIT-trap donor with a site-specific DNA inversion mechanism enabled one-step generation of reversible and conditional alleles in a single experiment. As a proof of concept, we successfully created mutant alleles for 21 disease-related genes in primary porcine fibroblasts with an average knock-in frequency of 53.2%, a great improvement over previous approaches. The versatile HIT-trapping strategy presented here is expected to simplify the targeted generation of mutant alleles and facilitate large-scale mutagenesis in large mammals such as pigs.Following the completion of animal genome sequencing projects, rapid and efficient mutagenesis strategies are needed for analyzing gene function and for creating human disease models. Gene trapping is a high-throughput mutagenesis strategy whereby random vector insertion can be achieved across the mouse genome. A typical gene-trap vector contains a promoter-less reporter/selection gene flanked by an upstream splice acceptor (SA) and a downstream poly(A) signal. Upon insertion into an intron of a gene, the vector both inactivates the trapped gene and enables the gene-specific expression of a reporter gene (Gossler et al. 1989; Stanford et al. 2001). To date, gene-trapping approaches have been successfully applied toward large-scale mutagenesis in mouse embryonic stem cells (mESCs) and generation of gene knockout mice (Skarnes et al. 2004). The main drawback of random gene trapping is that gene-trap alleles are not specifically engineered to target genes of interest in advance. Therefore, methods to streamline the introduction of predesigned, site-specific modifications into the genome by homologous recombination would represent a significant technological advance. Previously, a hybrid approach combining gene targeting and gene trapping (targeted trapping) enabled mutation of expressed genes in mESCs with high efficiency, using a gene-trap construct flanked by homologous sequences of the target locus (Friedel et al. 2005). Also, homologous recombination is commonly used for creating conditional alleles, which is essential to avoid embryonic lethality and to study the stage- and tissue-specific functions of genes (Branda and Dymecki 2004). However, both standard gene trapping and targeted trapping are only suitable for genes expressed in embryonic stem (ES) cells. Furthermore, construction of targeting donor vectors with homology arms is labor intensive and costly, and the low efficiency of homologous recombination is also a rate-limiting step for gene targeting in mammalian genomes.Recently, by taking advantage of precise genomic double-strand breaks (DSBs) created by the clustered regularly interspaced short palindromic repeats (CRISPR)-associated protein 9 (Cas9) system (Ran et al. 2013; Doudna and Charpentier 2014; Hsu et al. 2014), homology-directed repair (HDR) efficiency was substantially enhanced (Porteus and Carroll 2005), and even donors with short homology arms (Orlando et al. 2010) or single-stranded DNA oligonucleotides (Chen et al. 2011; Quadros et al. 2017) were found to be compatible with site-specific integration. However, each targeting donor for HDR still needs to be customized with gene-specific homology sequences. Because of the lack of ES cells for certain animals such as pigs, sheep, and cattle, the genome must be edited either in a zygote embryo or in a somatic cell for somatic cell nuclear transfer (SCNT) (Reddy et al. 2020). It is still not feasible to achieve large-scale insertional mutagenesis including conditional knockouts in these important species with random gene trapping or HDR-based methods. Also, the problem of genetic mosaicism in embryo editing remains unresolved (Mehravar et al. 2019), prompting a need for technological advances to accelerate genetic modification in somatic cells.Alternatively, the generally more efficient nonhomologous end joining (NHEJ) pathway has been exploited for site-specific insertion of exogenous DNA by simultaneous cleavage of both donor plasmid and genome using programmable nucleases (Cristea et al. 2013; Maresca et al. 2013; Brown et al. 2016; Suzuki et al. 2016; Sawatsubashi et al. 2018). In contrast to HDR-based strategies, NHEJ-mediated insertions do not require gene-specific homology arms, enabling diverse sites to be targeted with a universal donor vector. Therefore, we speculated that a gene-trap cassette could be inserted into a specific locus easily through this mechanism in any cell type.Here, by combining NHEJ-mediated knock-in and gene trapping, we developed a strategy for targeted mutagenesis, especially in somatic cells with low HDR activity, referred to as HIT-trapping. By using a universal donor, this strategy allows us to (1) create null alleles, (2) produce a fluorescent reporter signal that could potentially allow cells with null alleles to be identified very quickly, and (3) produce reversible and conditional alleles that would be very helpful to have in most animal models but are often cumbersome to create. 相似文献