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   3384篇
  免费   299篇
  国内免费   238篇
耳鼻咽喉   50篇
儿科学   23篇
妇产科学   27篇
基础医学   375篇
口腔科学   18篇
临床医学   416篇
内科学   498篇
皮肤病学   23篇
神经病学   280篇
特种医学   185篇
外国民族医学   7篇
外科学   331篇
综合类   579篇
现状与发展   1篇
预防医学   191篇
眼科学   49篇
药学   334篇
  1篇
中国医学   192篇
肿瘤学   341篇
  2024年   9篇
  2023年   42篇
  2022年   122篇
  2021年   158篇
  2020年   128篇
  2019年   99篇
  2018年   103篇
  2017年   94篇
  2016年   105篇
  2015年   131篇
  2014年   193篇
  2013年   166篇
  2012年   215篇
  2011年   249篇
  2010年   167篇
  2009年   134篇
  2008年   186篇
  2007年   160篇
  2006年   160篇
  2005年   125篇
  2004年   106篇
  2003年   107篇
  2002年   93篇
  2001年   85篇
  2000年   81篇
  1999年   122篇
  1998年   64篇
  1997年   89篇
  1996年   56篇
  1995年   65篇
  1994年   40篇
  1993年   24篇
  1992年   37篇
  1991年   22篇
  1990年   37篇
  1989年   29篇
  1988年   23篇
  1987年   14篇
  1986年   18篇
  1985年   17篇
  1984年   4篇
  1983年   2篇
  1982年   5篇
  1981年   8篇
  1980年   6篇
  1979年   8篇
  1978年   2篇
  1975年   2篇
  1974年   2篇
  1966年   2篇
排序方式: 共有3921条查询结果,搜索用时 15 毫秒
81.
82.
Acute liver injury is a common pathological basis for a variety of acute liver diseases in the clinic, which can eventually lead to liver fibrosis and even liver failure. In this study, we found that T cell Ig and mucin domain protein 3 (Tim-3) and TLR4 receptors play important roles in CCl4-induced acute liver injury. Tim-3 is a negative regulator that is expressed by T cells and macrophages. Using antibodies against Tim-3 (anti-Tim-3 Ab), we studied the Tim-3 signal in an animal model of acute liver injury and found that a large number of inflammatory factors were upregulated. In vitro experimental data shown that anti-Tim-3 Ab treatment increased interferon-ɣ production by concanavalin A (ConA)-stimulated spleen T cells, and we found that the expression level of interleukin (IL)-6 was increased in a macrophage/spleen T cell coculture system, while administration of galectin-9 (Gal-9, a Tim-3 ligand) reduced the IL-6 production. This indicates the importance of the Tim-3/Gal-9 signalling pathway in maintaining hepatic homeostasis. The Tim-3 signalling pathway inhibits TLR4-mediated NF-κB activity, and an anti-Tim-3 Ab does not affect the liver injury in TLR4-deficient mice. Regulation between Tim-3 and TLR4 determines the severity of liver damage. The negative regulation of Tim-3 reflects the protective mechanisms of patients with impaired liver function, and these results provide important information about innate and adaptive responses in the regulation of liver damage. This finding is potentially important for the study of early liver injury.  相似文献   
83.
In this work, sepiolite mineral nanofibers are facilely prepared by a microwave-hydrogen peroxide method, and the bulk densities of the samples are adopted to evaluate the defibering effect. The samples are systematically characterized through X-ray diffraction, scanning electron microscopy, specific surface area measurement and zeta potential determination, and the adsorptive performance for heavy metal ions in aqueous solution is studied using cadmium ions as the representative. It is found that the specific surface area and cumulative pore volume increase respectively up to 109.21 m2 g−1 and 0.234 cm3 g−1 under the microwave power of 400 W, while the zeta potential reaches a maximum when the pH is 5.0. The adsorption efficiency of sepiolite mineral nanofibers for cadmium ions can reach 68.6% as the optimal value. The as-fabricated sepiolite nanofibers can be regarded as a low-cost and environmentally friendly material which is a promising candidate for heavy metal ion removal from industrial wastewater.

In this work, sepiolite mineral nanofibers are facilely prepared by a microwave-hydrogen peroxide method, and the bulk densities of the samples are adopted to evaluate the defibering effect.  相似文献   
84.
This study investigated the cellular and molecular changes which occur in cartilage from adults with femoral neck fracture (FNF) and osteoarthritis (OA), and explored the similarities in hip cartilage obtained from elderly patients and patients with early OA. Femoral heads were retrieved from 23 female patients undergoing total hip arthroplasty (THA). This group included 7 healthy patients with FNF (hFNF), 8 elderly adults with FNF (eFNF), and 8 elderly patients with hip OA (OA). After high-field MRI T2 mapping, osteochondral plugs were harvested from the weight-bearing area of femoral heads for subsequent macroscopic, histologic, and immunochemical evaluation. Additionally, the contents of cartilage matrix were analyzed, and gene expression was detected. The surface of cartilage from hFNF and eFNF patients appeared smooth, regular, and elastic, whereas it showed irregularities, thinning, and defects in OA patients. Elevated T2 values and decreased accumulation of glycosaminoglycans (GAGs) were detected in cartilage from eFNF patients. Furthermore, type I collagen accumulation was slightly increased and type X collagen concentration was obviously elevated in eFNF patients; however, type II collagen distribution and the contents and anisotropy of collagen fibrils in eFNF patients showed no significant changes. Consistent with histology and immunohistochemical results, aggrecan was downregulated and type X collagen was upregulated, while collagens types I and II showed no significant changes in eFNF patients. The cellular and molecular characteristics of hip cartilage in eFNF patients who showed no symptoms of OA were similar to those in patients with mild OA. Thus, eFNF cartilage can serve as a comparative specimen for use in studies investigating early OA.  相似文献   
85.
利福平外用致原位肝移植术后患者过敏反应1例   总被引:1,自引:0,他引:1  
肝炎后肝硬化患者,原发性肝癌行原位肝移植术,于术后7 d皮肤破溃处涂利福平胶囊粉后出现过敏反应.利福平为临床常用的广谱抗菌素,外用后快速导致过敏反应未见报道, 该病例既往无过敏史,特殊之处在于为原位肝移植术后患者,移植术后用药有很多特殊之处,可供参考的资料不多.抗过敏治疗上以尽快纠正低氧血症对移植肝功能的恢复至关重要.  相似文献   
86.
目的:探讨了脑梗死患者治疗前后血清GM—CSF和血小板α-颗粒膜蛋白(PGMP)水平的变化及意义。方法:应用放射免疫分析对36例脑梗死患者进行了血清GM—CSF和PGMP水平测定,并以30例正常健康人作比较。结果:在治疗前血清GM—CSF和PGMP水平均非常显著地高于正常人组(P〈0.01),经治疗后6个月与正常人比较仍有显著差异(P〈0.05)。结论:脑梗死的发生、发展与血清GM—CSF和PGMP水平密切相关。  相似文献   
87.
Background: The new Family-Community-Hospital (FCH) three-level comprehensive management aimed to improve the efficiency and scale of peritoneal dialysis (PD) to meet the increased population of end-stage renal disease (ESRD). Our study focused on the clinical outcomes, quality of life, and costs evaluation of this model in a multi-center and prospective cohort study.Methods: A total of 190 ESRD patients who commenced PD at Shanghai Songjiang District were enrolled. According to different PD management models, patients were divided into the Family-Community-Hospital three-level management model (n = 90) and the conventional all-course central hospital management model (n = 100). The primary outcome was clinical outcomes of PD. The secondary outcomes were health-related quality of life (HRQOL) and medical costs evaluation.Results: Compared to conventional management, community-based FCH management achieved a similar dialysis therapeutic effect, including dropout rate (p = 0.366), peritonitis rate (p = 0.965), patient survival (p = 0.441), and technique survival (p = 0.589). Follow-up data showed that similar levels of the renal and peritoneal functions, serum albumin, cholesterol and triglyceride, PTH, serum calcium, and phosphorus between the two groups (all p > 0.05). HRQOL survey showed that the FCH management model helped to improve the psychological status of PD patients, including social functioning (p = 0.006), role-emotional (p = 0.032), and mental health (p = 0.036). FCH management also reduced the hospitalization (p = 0.009) and outpatient visits (p = 0.001) and saved annual hospitalization costs (p = 0.005), outpatient costs (p = 0.026), and transport costs (p = 0.006).Conclusions: Compared with conventional management, community-based FCH management achieved similar outcomes, improved psychological health, reduced medical budgets, and thus had a good social prospect.  相似文献   
88.
Copper is widely present in the natural environment and inevitably poses a risk to both human health and the natural environment. Biochar is an inexpensive, clean and sustainable sorbent material that can be used as a resource for copper removal, and there is interest in new ways to chemically treat biochar to tune its unique properties and modify its atomic structure. In this study, biochar was oxidized, and then polyethyleneimine (PEI) modified chitosan and carboxylated biochar were economically compounded through a multicomponent Ugi reaction to effectively remove Cu(ii). PEI enhances the adsorption of Cu(ii) within an optimum solution pH range of 3.5–5.5. The adsorption process follows a pseudo-second-order kinetic model. When the dosage of BC-NH2 was 4 g L−1 and the temperature was 303 K, the maximum adsorption capacity calculated by the Langmuir model was 26.67 mg g−1. The adsorption process of Cu(ii) on BC-NH2 was heat-trapping and spontaneous. BC-NH2 showed good selectivity for K+ and Mg2+, and BC-NH2 desorbed by NaOH showed better adsorption performance than H2SO4 in the adsorption–desorption cycle. Characterization by SEM, EDS, BET, FTIR, TGA and XPS showed successful coupling and that the amide group of BC-NH2 had chelated with Cu(ii). This atomically economical multicomponent Ugi reaction provides a new option for preparing composite materials that effectively remove heavy metals.

Polyethyleneimine-modified chitosan and carboxylated biochar were economically compounded by a multicomponent Ugi reaction to produce products rich in amide functional groups.  相似文献   
89.
In this work, an electrochemical sensor was designed for trace monitoring of bisphenol A (BPA) by decorating a hybrid bilayer molecularly imprinted membrane (MIM) on a multi-walled carbon nanotube-modified glassy carbon electrode. When BPA in the MIM was eluted, a composite molecularly imprinted electrochemical sensor was constructed. Under optimal conditions, the developed sensor showed two linear relationships between ΔIp and BPA concentration in the range of 0.04 μM to 8 μM, as well as good selectivity and stability, and was also applied to detect BPA in water samples with desirable recoveries ranging from 92.0% to 107.0%.

A hybrid bilayer molecularly imprinted membrane-dependent electrochemical sensor was developed for bisphenol A assay based on 4-pentenoyl-isoleucyl-chitosan oligosaccharide and acrylamide functional monomers.  相似文献   
90.
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