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   2318篇
  免费   165篇
  国内免费   46篇
耳鼻咽喉   30篇
儿科学   80篇
妇产科学   10篇
基础医学   267篇
口腔科学   40篇
临床医学   278篇
内科学   304篇
皮肤病学   79篇
神经病学   152篇
特种医学   255篇
外国民族医学   1篇
外科学   216篇
综合类   248篇
预防医学   185篇
眼科学   32篇
药学   166篇
中国医学   78篇
肿瘤学   108篇
  2023年   11篇
  2022年   21篇
  2021年   41篇
  2020年   32篇
  2019年   19篇
  2018年   25篇
  2017年   46篇
  2016年   33篇
  2015年   55篇
  2014年   83篇
  2013年   93篇
  2012年   119篇
  2011年   144篇
  2010年   109篇
  2009年   95篇
  2008年   143篇
  2007年   108篇
  2006年   104篇
  2005年   83篇
  2004年   77篇
  2003年   80篇
  2002年   80篇
  2001年   74篇
  2000年   71篇
  1999年   47篇
  1998年   37篇
  1997年   35篇
  1996年   34篇
  1995年   26篇
  1994年   15篇
  1993年   24篇
  1992年   28篇
  1991年   41篇
  1990年   47篇
  1989年   40篇
  1988年   38篇
  1987年   30篇
  1986年   35篇
  1985年   34篇
  1984年   29篇
  1983年   20篇
  1982年   19篇
  1981年   21篇
  1980年   15篇
  1979年   17篇
  1978年   13篇
  1977年   13篇
  1975年   14篇
  1914年   13篇
  1912年   12篇
排序方式: 共有2529条查询结果,搜索用时 15 毫秒
71.
Mammalian retinas comprise a variety of interneurons, among which amacrine cells represent the largest group, with more than 30 different cell types each exhibiting a rather distinctive morphology and carrying out a unique function in retinal processing. However, many amacrine types have not been studied systematically because, in particular, amacrine cells with large dendritic fields, i.e. wide‐field amacrine cells, have a low abundance and are therefore difficult to target. Here, we used a transgenic mouse line expressing the coding sequence of enhanced green fluorescent protein under the promoter for choline acetyltransferase (ChAT‐EGFP mouse) and characterized a single wide‐field amacrine cell population monostratifying in layer 2/3 of the inner plexiform layer (WA‐S2/3 cell). Somata of WA‐S2/3 cells are located either in the inner nuclear layer or are displaced to the ganglion cell layer and exhibit a low cell density. Using immunohistochemistry, we show that WA‐S2/3 cells are presumably GABAergic but may also release acetylcholine as their somata are weakly positive for ChAT. Two‐photon‐guided patch‐clamp recordings from intact retinas revealed WA‐S2/3 cells to be ON‐OFF cells with a homogenous receptive field even larger than the dendritic field. The large spatial extent of the receptive field is most likely due to the extensive homologous and heterologous coupling among WA‐S2/3 cells and to other amacrine cells, respectively, as indicated by tracer injections. In summary, we have characterized a novel type of GABAergic ON‐OFF wide‐field amacrine cell which is ideally suited to providing long‐range inhibition to ganglion cells due to its strong coupling.  相似文献   
72.
目的了解鞍山市铁东区公共场所使用化妆品卫生问题,保障使用者身体健康。方法对2013年度鞍山市铁东区卫生防疫站辖区内监管的公共场所随机抽检化妆品,对公共场所使用化妆品单位数及比例,化妆品标签标识卫生问题等进行描述。结果住宿业化妆品使用情况为56%,其他三种场所100%使用。化妆品标签标识检查住宿业合格率最低,仅为50%。国产特殊用途化妆品持有效证件率仅为65%,普通的仅为62%。标签标识问题突出,进货渠道复杂。化妆品抽检合格率低。结论公共场所的化妆品卫生质量令人担忧。  相似文献   
73.
笔者作为基层卫生监督工作人员经过十多年的公共场所卫生监督工作,通过对鞍山市铁东区公共场所卫生监督情况进行分析。发现当前存在许多公共场所卫生监督执法困难和难题,主要表现为卫生监督队伍薄弱,新兴公共场所剧增,公共场所执法依据不确定性(无法可依)等问题。笔者提出相应的解决建议,应转变卫生监督观念,提高监督管理质量。  相似文献   
74.
75.
目的:建立不同程度大鼠铅中毒模型。方法:Wistar大鼠分别自由饮用不同浓度的醋酸铅1、3、6个月,以原子吸收法测定全血和脑匀浆液的铅水平。结果:实验组全血和脑匀浆中的铅水平均明显高于对照组(P〈0.01),且二者的铅水平随染铅时问的延长、浓度的增加均明显升高(P〈0.05)。结论:以不同时间、不同浓度染铅均成功地建立了大鼠铅中毒模型。  相似文献   
76.
77.
Methylprednisolone sodium succinate limited the ability of zymosan or lipopolysaccharide to activate complement in normal serum by the alternative amplification pathways. Methylprednisolone limited B consumption in a reaction mixture which contained purified C3b, D, and B, indicating that soluble steroid directly inhibited the amplification pathway. The ability of soluble steroid to inhibit events in the alternative and amplification pathways of complement may provide a partial explanation for the effectiveness of steroids in treating gram negative septic shock.  相似文献   
78.
Using PET with (15)O water, we characterized the time course of functional brain changes following the acute administration of a first- and a second-generation antipsychotic. Volunteers with schizophrenia were scanned while drug-free (baseline) and after single dose administration of haloperidol (n=6) or olanzapine (n=6) during a time course adapted to their plasma kinetics. To obtain brain location information, we contrasted each post-drug scan to baseline-acquired scans. We plotted the regional cerebral blood flow (rCBF) extracted in these locations and calculated the kinetic characteristics of the curves. Further, we compared and contrasted the rCBF changes induced by the drugs over the first 4 h post-drug administration. Dorsal and ventral striatum, thalamus and anterior cingulate cortex were activated with haloperidol, while frontal, temporal and cerebellum regions evidenced reduced flow. With olanzapine, ventral striatum, anterior cingulate and temporal cortices evidenced increases, and thalamus and lingual cortex decreases, in rCBF. Both drugs activated the caudate nucleus. Haloperidol induced greater activation of the dorsal striatum than did olanzapine. These data reveal important differences in patterns of brain activation between the drugs. Differences in the involvement in basal ganglia parallel known differences between the drugs in the emergence of acute EPS upon emergency administration.  相似文献   
79.
Elevated plasma levels of fibrinogen are associated with the presence of cardiovascular disease, but it is controversial whether elevated fibrinogen causally imparts an increased risk, and as such is a true modifier of cardiovascular disease, or is merely associated with disease. By investigating a transgenic mouse model of hyperfibrinogenemia, we show that elevated plasma fibrinogen concentration (1) elicits augmented fibrin deposition in specific organs, (2) interacts with an independent modifier of hemostatic activity to regulate fibrin turnover/deposition, (3) exacerbates neointimal hyperplasia in an experimental model of stasis-induced vascular remodeling, yet (4) may suppress thrombin generation in response to a procoagulant challenge. These findings provide direct experimental evidence that hyperfibrinogenemia is more than a by-product of cardiovascular disease and may function independently or interactively to modulate the severity and/or progression of vascular disease.  相似文献   
80.
BACKGROUND: There are limited studies of large cohorts of patients with specific polysaccharide antibody deficiency (SPAD) syndrome. OBJECTIVE: To study the clinical and laboratory characteristics of patients with specific polysaccharide antibody deficiency syndrome. METHODS: We retrospectively studied 75 patients with total IgG levels of at least 500 mg/dL and fewer than 9 of 12 responses to vaccination with pneumococcal vaccine polyvalent. Exclusion criteria included an IgG level less than 500 mg/dL, established immunodeficiency syndrome, and secondary immunodeficiency. RESULTS: The most common clinical presentation was frequent infections (n = 69; 92%), including sinusitis (n = 53; 77%), pneumonia (n = 29; 42%), ear infections (n = 18; 26%), and bronchitis (n = 19; 28%). Other presentations were systemic infections (n = 5; 7%), autoimmune or rheumatic diseases (n = 6; 8%), and chronic diarrhea (n = 4; 5%). The median IgG2 level of patients with no response to pneumococcal vaccine polyvalent tended to be lower than that of patients with at least 1 response (150 vs 193 mg/dL, respectively; P = .06). There was no association between total IgG level (categorized as 500-600 or > or = 600 mg/dL) and frequency of infection (P = .43). Patients with fewer responses to pneumococcal vaccine polyvalent and a higher frequency of infections were more likely to receive intravenous immunoglobulin (IVIG) therapy (P = .01 and .003, respectively). Treatment with IVIG significantly reduced the number of infections (P < .001). CONCLUSION: Patients with no response to pneumococcal vaccine polyvalent tended to have lower IgG2 levels; those with fewer responses were more likely to receive IVIG therapy.  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