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   178627篇
  免费   14646篇
  国内免费   7663篇
耳鼻咽喉   1167篇
儿科学   4940篇
妇产科学   3966篇
基础医学   24823篇
口腔科学   3819篇
临床医学   14384篇
内科学   27592篇
皮肤病学   2662篇
神经病学   18472篇
特种医学   2986篇
外国民族医学   47篇
外科学   13553篇
综合类   25803篇
现状与发展   25篇
预防医学   10892篇
眼科学   3845篇
药学   22636篇
  39篇
中国医学   5364篇
肿瘤学   13921篇
  2024年   250篇
  2023年   2010篇
  2022年   3404篇
  2021年   5809篇
  2020年   5093篇
  2019年   4822篇
  2018年   4848篇
  2017年   5351篇
  2016年   5723篇
  2015年   6094篇
  2014年   10352篇
  2013年   12686篇
  2012年   10557篇
  2011年   11918篇
  2010年   9954篇
  2009年   9777篇
  2008年   10292篇
  2007年   10100篇
  2006年   8954篇
  2005年   7962篇
  2004年   6919篇
  2003年   6166篇
  2002年   5103篇
  2001年   4440篇
  2000年   3914篇
  1999年   3358篇
  1998年   3228篇
  1997年   2914篇
  1996年   2660篇
  1995年   2293篇
  1994年   1982篇
  1993年   1697篇
  1992年   1404篇
  1991年   1222篇
  1990年   1045篇
  1989年   849篇
  1988年   674篇
  1987年   614篇
  1986年   583篇
  1985年   770篇
  1984年   629篇
  1983年   405篇
  1982年   558篇
  1981年   385篇
  1980年   314篇
  1979年   201篇
  1978年   158篇
  1977年   128篇
  1976年   113篇
  1975年   85篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
81.
《Clinical therapeutics》2019,41(5):836-847
PurposeA role for the immune system in causing myalgic encephalopathy/chronic fatigue syndrome (ME/CFS) is long suspected, but few studies have looked for specific autoantibodies that might contribute to the symptoms. Our aim was to look for evidence of antibodies to neuronal proteins in patients with ME/CSF.MethodsSera samples from 50 patients and 50 healthy individuals were sent coded to the Neuroimmunology Laboratory in Oxford. Screening for antibody binding to neuronal tissue was performed on brain tissue and neuronal cultures. Specific serum antibodies were assessed by antigen-specific cell-based assays and radioimmunoassays. After antibody testing, the associations between seropositive status and clinical data were investigated.FindingsOverall, 8 patients and 11 participants were found to have some serum immunoreactivity toward neuronal or neuromuscular junction proteins, but only 1 patient and 2 participants had specific serum antibodies. Nevertheless, seropositive status in patients with ME was associated with shorter duration since onset and a more severe disease.ImplicationsThe results indicate no overall increased frequency of antibodies to neuronal proteins in ME/CSF and no evidence of a specific antibody that might be causative or contribute to clinical features in patients. However, the association of seropositive status with shorter duration of disease and more severe symptoms suggests a possible role of antibodies at onset in some patients and should be the focus of future studies.  相似文献   
82.
Background: Guidelines recommend primary prophylactic use of colony-stimulating factor (PP-CSF) when risk of febrile neutropenia (FN) – based on chemotherapy and patient risk factors – is high. Whether and how PP-CSF use may have changed over time (e.g. due to guideline revisions, increasing use of myelosuppressive regimens, controversy regarding inappropriate CSF use), and whether there has been a concomitant change in the incidence of FN, is unknown.

Methods: A retrospective cohort design and data from two US healthcare claims repositories were employed. The study population included patients who had non-metastatic cancer of the breast, colon/rectum, lung or ovaries, or non-Hodgkin’s lymphoma (NHL), and who received myelosuppressive chemotherapy regimens with an intermediate/high risk for FN. For each patient, the first cycle of the first course was characterized in terms of PP-CSF use and FN episodes. Crude incidence proportions for PP-CSF and FN during the first cycle were estimated by calendar quarter (2010–2016); multivariable logistic regression models were used to estimate quarter-specific adjusted mean probabilities of FN by PP-CSF use.

Results: The study population totaled 142,730 patients with breast cancer (61%), colorectal cancer (14%), NHL (11%), ovarian cancer (10%) or lung cancer (5%). PP-CSF use increased from 52% in 1Q2010 to 58% in 4Q2016; pegfilgrastim was the most commonly used agent (>96% across quarters). PP-CSF administration on the same day as chemotherapy ranged from 8 to 11% until 1Q2015, and increased to 64% by 4Q2016. Adjusted incidence proportions for FN in the first chemotherapy cycle ranged from 2.7% (95% CI: 2.3–3.0) to 3.7% (95% CI: 3.1–4.3) among those who did not receive PP-CSF, and was 2.6% (95% CI: 2.5–2.7) across quarters among those who received PP-CSF.

Conclusions: Although the use of PP-CSF is commonplace in current US clinical practice, underutilization in cancer patients receiving chemotherapy regimens with an intermediate/high risk for FN may still be an issue. Use of same-day PP-CSF increased markedly from the end of 2015, although this finding reflects (at least in part) increased uptake of pegfilgrastim delivered via an on-body injector as well as the recent change in clinical practice guidelines. Overall, patients receiving PP-CSF appear to have a lower risk of FN during the first cycle of chemotherapy.  相似文献   

83.
84.
目的:对白鲜皮粗多糖(DDP)进行分离纯化,并研究其抗银屑病作用。方法:DDP经膜分离技术截留相对分子质量小于10 k Da的组分(DDP-UF),采用DEAE-52纤维素柱分离纯化得到4种组分(DDP-UF-1,DDP-UF-2,DDP-UF-3,DDPUF-4);并通过红外光谱法,高效凝胶渗透色谱法(HPGPC),高效液相色谱法(HPLC),扫描电镜(SEM)测定其理化性质及结构特征。选用咪喹莫特乳膏诱导银屑病小鼠模型,己烯雌酚诱导雌鼠阴道上皮细胞增殖,酶联免疫吸附测定法(ELISA)检测各组小鼠血清白细胞介素(IL)-17与IL-23含量,苏木精-伊红(HE)染色法观察小鼠背部皮肤组织病理变化、阴道上皮细胞有丝分裂指数变化。结果:DDP-UF-1~4均具有多糖特征吸收峰,DDP-UF-1~4相对分子质量分别为10 948,40 148,32 222,19 943 Da;单糖组成及摩尔比分别为甘露糖-葡萄糖-半乳糖(32. 45∶11. 35∶8. 69),甘露糖-鼠李糖-葡萄糖醛酸-葡萄糖-木糖(25. 68∶23. 44∶21. 62∶18. 86∶3. 68),甘露糖-鼠李糖-葡萄糖醛酸-半乳糖醛酸-木糖-半乳糖(18. 68∶4. 61∶3. 89∶1. 65∶5. 36∶6. 21),葡萄糖醛酸-半乳糖醛酸-葡萄糖-木糖-半乳糖(11. 63∶15. 26∶5. 32∶2. 08∶3. 46);扫描电镜(SEM)显示DDP-UF-1~4形态结构为片状或海绵状结构。DDP-UF-1与DDP-UF-3可改善银屑病小鼠背部皮损状态、抑制雌鼠阴道上皮细胞有丝分裂、明显降低血清IL-17,IL-23含量(P 0. 05,P 0. 01)。结论:DDP-UF-1与DDP-UF-3均具有良好的抗银屑病作用,其作用可能与抑制IL-23/IL-17信号通路有关。  相似文献   
85.
胆碱能抗炎通路是一条神经免疫通路,主要依靠乙酰胆碱与巨噬细胞及其他细胞表面上的α7nAchR相结合抑制促炎因子的合成与释放,从而防止组织损伤。α7nAchR是胆碱能递质的主要受体,在胆碱能抗炎通路中起关键作用。针刺治疗有明确的抗炎作用,其作用机制可能与调控α7nAchR激活胆碱能抗炎通路有关。近年来虽然国内外学者对针刺抗炎机制进行了大量研究,然而针刺抗炎的作用机制目前仍不明确。该文从胆碱能抗炎通路概述、α7nAchR结构及功能、α7nAchR的分布、α7nAchR在胆碱能抗炎通路的作用、针刺调控α7nAchR激活胆碱能抗炎通路的机制等方面对针刺调控α7nAchR激活胆碱能抗炎通路进行分析总结,为今后探究针刺抗炎作用机制提供借鉴思路和科学依据。  相似文献   
86.
《药学学报(英文版)》2020,10(7):1294-1308
A great challenge in multi-targeting drug discovery is to identify drug-like lead compounds with therapeutic advantages over single target inhibitors and drug combinations. Inspired by our previous efforts in designing antitumor evodiamine derivatives, herein selective histone deacetylase 1 (HDAC1) and topoisomerase 2 (TOP2) dual inhibitors were successfully identified, which showed potent in vitro and in vivo antitumor potency. Particularly, compound 30a was orally active and possessed excellent in vivo antitumor activity in the HCT116 xenograft model (TGI = 75.2%, 150 mg/kg, p.o.) without significant toxicity, which was more potent than HDAC inhibitor vorinostat, TOP inhibitor evodiamine and their combination. Taken together, this study highlights the therapeutic advantages of evodiamine-based HDAC1/TOP2 dual inhibitors and provides valuable leads for the development of novel multi-targeting antitumor agents.  相似文献   
87.
Platelet α-granules release growth factors (GFs) that promote healing and tissue regeneration. Platelet-rich plasma (PRP) is shown to be beneficial in treating alopecia, and however, clinical response can be inconsistent. Due to several fold enrichment of platelets secreting large quantities of GFs following PRP injections, heterogeneity in amounts of GFs secreted by platelets may contribute to inconsistent clinical responses. Herein, we evaluated factors that could potentially contribute to heterogeneous secretion of GFs by platelets. We measured platelet secretion of transforming growth factor beta1 (TGFβ1), platelet-derived growth factor (PDGF-BB), epidermal growth factor (EGF), vascular endothelial growth factor (VEGF) and fibroblast growth factor (FGF2) in aliquots of de-identified PRP samples from female patients undergoing therapy in the hair disease clinic. Although secretion of GFs by platelets was comparable in PRP samples of patients with non-cicatricial and cicatricial alopecia, a Shapiro-Wilk test for normal distribution indicated significant variability across all patient samples. The amount of GF secreted by platelets was comparable when PRP prepared from two FDA-cleared devices with distinct techniques were compared. We provide evidence of platelets secreting heterogeneous amounts of GFs within each sample as high and low secretion of random factors could be simultaneously detected. These results suggest inherent heterogeneity in secretion of GFs by platelets in patient samples that are not influenced by the device used to prepare PRP. Since some GFs could have antagonistic effects on hair growth, a balance between amounts of growth promoting and inhibiting factors may be crucial in determining clinical response to PRP therapy.  相似文献   
88.
Von Willebrand Disease is a common cause of excessive bruising and bleeding in children. This short article gives advice on diagnosis and management for paediatricians. Given its prevalence and presenting symptoms, VWD should always be considered in the assessment of children suspected of non-accidental injury. Its diagnosis can be challenging, not only because of the various subtypes of the disorder but because of the considerable overlap between VWD and normal individuals. Laboratory diagnosis requires a range of quantitative and qualitative tests of the VWF protein, with targeted gene analysis increasingly used to confirm the diagnosis of type 2 and type 3 VWD. Bleeding Assessment Tools may be helpful in directed laboratory testing but are often less so in young children who have had limited haemostatic challenges. Treatment for VWD includes the use of antifibrinolytic drugs, vasopressin or VWF-containing clotting factor concentrates. Treatment is often on-demand for individual bleeding episodes but there are specific indications for the use of prophylactic treatment in children.  相似文献   
89.
90.
《Cancer cell》2021,39(11):1497-1518.e11
  1. Download : Download high-res image (282KB)
  2. Download : Download full-size image
  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