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   165828篇
  免费   16388篇
  国内免费   10364篇
耳鼻咽喉   1554篇
儿科学   2575篇
妇产科学   2126篇
基础医学   17438篇
口腔科学   2724篇
临床医学   22901篇
内科学   21471篇
皮肤病学   1890篇
神经病学   7443篇
特种医学   5695篇
外国民族医学   69篇
外科学   14132篇
综合类   30114篇
现状与发展   43篇
一般理论   25篇
预防医学   13898篇
眼科学   4977篇
药学   18746篇
  218篇
中国医学   11793篇
肿瘤学   12748篇
  2024年   2042篇
  2023年   2614篇
  2022年   6381篇
  2021年   8155篇
  2020年   6515篇
  2019年   5376篇
  2018年   5489篇
  2017年   5345篇
  2016年   5110篇
  2015年   7545篇
  2014年   9414篇
  2013年   9470篇
  2012年   13613篇
  2011年   14399篇
  2010年   10157篇
  2009年   8282篇
  2008年   10019篇
  2007年   9640篇
  2006年   9186篇
  2005年   8118篇
  2004年   5617篇
  2003年   5057篇
  2002年   4095篇
  2001年   3323篇
  2000年   2959篇
  1999年   2853篇
  1998年   1689篇
  1997年   1661篇
  1996年   1281篇
  1995年   1168篇
  1994年   1026篇
  1993年   634篇
  1992年   699篇
  1991年   599篇
  1990年   563篇
  1989年   488篇
  1988年   437篇
  1987年   352篇
  1986年   285篇
  1985年   240篇
  1984年   147篇
  1983年   91篇
  1982年   49篇
  1981年   65篇
  1980年   33篇
  1979年   68篇
  1978年   24篇
  1974年   32篇
  1973年   21篇
  1969年   20篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
"Trichohyalin" is a 220-kD protein found in trichohyalin granules that are present as major differentiation products in the medulla and inner root sheath cells of human hair follicles. It was unclear whether this protein served as an intermediate filament precursor in the inner root sheath or as an intermediate-filament-associated (matrix) protein. We have produced a panel of monoclonal antibodies (AE15-17) to this protein and used them to trace its fate during inner root sheath differentiation. These studies have allowed us to define three immunologically distinct forms of this trichohyalin protein. They are 1) the AE15-positive form, which is found throughout all trichohyalin granules; 2) the AE16-positive form, which is localized as discrete punctae on the surface of trichohyalin granules; and 3) the AE17-positive, intermediate-filament-bound form, which associates with the inner root sheath filaments with a regular, 400-nm periodicity. From these results we suggest that the 220-kD trichohyalin protein is an intermediate-filament-associated protein that may play a role in the lateral aggregation, precise alignment, and stabilization of inner root sheath filament bundles.  相似文献   
102.
A patient presented at the Department of Orthodontics, Medunsa Dental Hospital, complaining of "crooked teeth". On clinical examination it was evident that several teeth were unerupted. The absence of a normal eruption pattern of certain teeth as well as delayed eruption of others, resulted in a malocclusion.  相似文献   
103.
Tumor-induced osteomalacia and rickets   总被引:4,自引:0,他引:4  
Tumor-induced osteomalacia is a clinicopathological entity in which vitamin D-resistant osteomalacia or rickets occurs in association with a tumor. A total of 72 cases (three current, 69 from review of literature) has been reported to date. Men and women are equally affected. The majority are adults over 30 years old who exhibit progressive lower leg and back pain. Forty bone and 31 soft-tissue tumors were responsible for this syndrome; two-thirds occurred in the extremities. Chemical findings are typical: low serum phosphorus, normal serum calcium, and elevated alkaline phosphatase. Serum levels of 1,25-dihydroxyvitamin D were low or undetectable. Histologically, more than a third were classified as vascular tumors, and half of these cases were hemangiopericytomas that were distributed equally between bone and soft tissues. Other common diagnoses included nonossifying fibromas, "mesenchymal" and giant-cell tumor variants. Features common to all tumors were prominent vascularity, and giant and primitive stromal cells. Only 10 were histologically malignant. Ultrastructural studies have not shown any secretory granules suggestive of a hormone-secreting tumor. It is clear, however, that the tumor is responsible for the osteomalacia because the complete removal generally results in a dramatic reversal of all symptoms and signs.  相似文献   
104.
105.
肌萎灵注射液对大鼠原代培养运动神经元生长的影响   总被引:2,自引:0,他引:2  
为了观察中药制剂肌萎灵注射液对大鼠原代培养脊髓运动神经元生长的影响,本研究采用MTT方法观察神经元活力,并通过免疫组织化学技术进行NF 200染色后图像分析测定突起长度。结果表明:浓度为0. 5% ~5%的肌萎灵注射液能增加培养神经元活力,浓度为0. 5% ~1%的肌萎灵能促进神经元突起生长。本研究结果提示:肌萎灵注射液对培养的大鼠脊髓运动神经元生长有促进作用。  相似文献   
106.
An undulation pump is a special rotary blood pump in which rotation of a brushless DC motor is transformed to an undulating motion by a disc in the pump housing attached by means of a special link mechanism. In the blood pump, a closed line between the disc and housing moves from the inlet to the outlet by this undulating disc motion, which sucks and pushes the blood from the inlet to the outlet. Because the same phenomena occurs at both sides of the disc, a continuous flow is obtained when the motor rotational speed is constant. The pump flow pattern can be easily changed from continuous flow to pulsatile flow by controlling the motor drive current pattern. A seal membrane made of segmented polyurethane protects the blood from invading the link mechanism as well as the motor. UPTAH is fabricated with two undulation pumps and two brushless DC motors. Its size is 75 mm in diameter and 80 mm long, and it has one of the great advantage of no compliance chamber required in the system. UPTAHs were implanted under cardiopulmonary bypass (CPB) into the chest cavities of 16 goats, each weighing between 41 and 72 kg. No anticoagulant and antiplatelet agent was used after the surgery. The left atrial pressure was automatically controlled to prevent its elevation and sucking of the atrial wall into the atrial cuff. The following results were obtained: (1) UPTAHs fit well into all the goats; (2) the longest survival was 19.8 days, the cause of death was bleeding from the aortic anastomosis; (3) No thrombus was observed in the blood pump despite no anticoagulant use. Hemolysis depended upon the length of CPB during surgery. When CPB time was within 2 hours, hemolysis level returned to baseline within a few days of the surgery. UPTAH is a promising implantable TAH, because of its small size and easy controllability.  相似文献   
107.
In addition to their well-characterized role in allergic inflammation, recent data confirm that mast cells play a more extensive role in a variety of viral infections. The contribution of mast cells to Newcastle disease pathogenesis has not been investigated. We evaluated mast cell activity after Newcastle disease virus (NDV) infection in specific pathogen free chickens using cytochemical and immunocytochemical analyses. The results were as follows. Severe tissue damage was observed in the proventriculus, duodenum, jejunum and caecal tonsil, and NDV antigens were detected and presented extensively in these tissues. Second, in the NDV-infected group, the mast cell population was increased markedly in the proventriculus, duodenum, jejunum and caecal tonsil at 24, 48, 72 and 96 h after infection (P<0.01). However, very few mast cells were observed in those same tissues in the control. More intriguingly, the greatest number of mast cells was found in the proventriculus, which also showed the greatest level of NDV antigens. Third, the content of tryptase was significantly higher (P<0.01) in the NDV-infected group compared with the control from 24 to 96 h post infection). Furthermore, as an important protease released by mast cells, tryptase had a positive correlation with mast cell distribution. These data indicated that mast cells were involved in the response to NDV. Our results also suggested that the broad range of mast cell mediators might have a role in the pathology of Newcastle disease.  相似文献   
108.
Cytokines produced by macrophages in the periprosthetic membranes surrounding joint replacements have been implicated as causal agents in osteolysis and prosthetic loosening. The present study characterizes the response of human peripheral blood monocytes to titanium particles. Monocytes were obtained from donated blood and were cultured in the presence of different-sized titanium particles. Exposure to titanium-aluminum-vanadium particles significantly changed the release of tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), and interleukin-1 (IL-1), whereas there was no significant effect on the release of prostaglandin E(2) (PGE(2)). When monocytes were cultured with particles, the titanium alloy particles induced significantly more release of TNF-alpha and less IL-1 secretion. Ciprofloxacin inhibited production of TNF-alpha, IL-6, IL-1, and PGE(2) in human monocytes exposed to titanium particles. In contrast to ciprofloxacin, indomethacin was not a potent inhibitor of TNF-alpha production but potentiated IL-6 production in titanium-stimulated monocytes. Indomethacin had no effect on the production of IL-1 and was a potent inhibitor of PGE(2) production in titanium-stimulated monocytes. Pentoxifylline had an inhibitor effect on TNF-alpha production in titanium-stimulated monocytes. Pentoxifylline potentiated IL-6 and IL-1 production in monocytes exposed to titanium particles and had a biphasic effect on the PGE(2) production. The results of this study support our hypothesis that human monocytes release bone resorption mediators after in vitro exposure to TiAlV alloy particles. The results also demonstrate the differences of bone-resorbing mediators in response to different wear particle size. The pharmacologic agents (ciprofloxacin, pentoxifylline, and indomethacin) that can modulate the release of bone resorbing mediators such as PGE(2), TNF-alpha, IL-1, and IL-6 release from human monocytes. The results help to elucidate the differences in cellular response to wear particles but may not be directly transposed to the human situation.  相似文献   
109.
目的探讨1例有不良孕产史的大Y携带者的胚胎异常情况。方法1对有2次自然流产史的夫妇,男方染色体核型为46,XY,Yqh ,常规超促排卵和卵母细胞胞浆内单精子注射,受精后第3天和第4天进行胚胎活检,获取分裂球,采用18,X,Y三色着丝粒探针进行荧光原位杂交分析(FISH),第5天移植正常胚胎。异常胚胎及废弃胚胎所有分裂球第6天再次FISH确定胚胎核型。结果患者获卵19个,对其中13个M2期卵母细胞进行ICSI,12个受精,分裂11胚。10个胚胎获得明确诊断,其中4个正常胚胎,6个异常胚胎,异常发生率达60%。5个为女胚,其中1个正常核型,4个异常胚胎中2个为无序分裂,2个为嵌合体;5个为男胚,3个正常,2个异常胚胎中1个为无序分裂,1个为嵌合体。对染色体正常的1个女胚进行宫腔内移植,未获得妊娠。结论该例大Y患者胚胎非整倍体发生率增高可能是导致其不良孕产史的原因。  相似文献   
110.
已有的研究成果表明,冠心病患者心脏各导联心电图(ECG)的关联维数D2比正常人均有不同程度的下降。为了进一步研究心肌缺血情况、导联位置和关联维数变化的关系,本研究设计了6只兔子急性心肌缺血实验模型,计算了其不同时间段的12导同步ECG,作出关联维数一时间(D2-T)曲线,结合电生理和解剖学知识,研究了实验结果,发现急性心肌缺血初期ECG的D2值具有动态变化特性,其原因在于心血管中存在代偿作用。ECG的D1的变化反映了单一化的心脏传输网络系统的非线性复杂性的变化。将此结论由动物推广到人,可以为临床上运用D2值分析心肌缺血病症严重程度提供理论指导。  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