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   61154篇
  免费   5688篇
  国内免费   3431篇
耳鼻咽喉   519篇
儿科学   874篇
妇产科学   1005篇
基础医学   7021篇
口腔科学   1079篇
临床医学   7136篇
内科学   9894篇
皮肤病学   733篇
神经病学   2915篇
特种医学   2524篇
外国民族医学   34篇
外科学   7337篇
综合类   9071篇
现状与发展   15篇
一般理论   16篇
预防医学   3964篇
眼科学   1486篇
药学   6520篇
  53篇
中国医学   3085篇
肿瘤学   4992篇
  2024年   178篇
  2023年   845篇
  2022年   2081篇
  2021年   2868篇
  2020年   2070篇
  2019年   1902篇
  2018年   2033篇
  2017年   1806篇
  2016年   1798篇
  2015年   2501篇
  2014年   3161篇
  2013年   3176篇
  2012年   4449篇
  2011年   4727篇
  2010年   3067篇
  2009年   2514篇
  2008年   3363篇
  2007年   3423篇
  2006年   3174篇
  2005年   2960篇
  2004年   2392篇
  2003年   2208篇
  2002年   2007篇
  2001年   1666篇
  2000年   1596篇
  1999年   1439篇
  1998年   774篇
  1997年   780篇
  1996年   631篇
  1995年   530篇
  1994年   463篇
  1993年   313篇
  1992年   506篇
  1991年   412篇
  1990年   388篇
  1989年   345篇
  1988年   274篇
  1987年   260篇
  1986年   205篇
  1985年   160篇
  1984年   117篇
  1983年   84篇
  1982年   60篇
  1981年   73篇
  1980年   39篇
  1979年   72篇
  1978年   37篇
  1974年   36篇
  1973年   33篇
  1972年   41篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
目的 :了解当归注射液改善脑循环治疗脑血栓的临床效果。方法 :对 46例脑血栓形成患者应用当归注射液进行治疗 ,对比分析其治疗前后血浆前列环素 (PGI2 )、血栓烷A2 (TXA2 )及自由基水平。结果 :脑血栓形成患者TXA2 、丙二醛 (MDA)明显升高 ,超氧化物岐化酶 (SOD)明显降低。当归注射液治疗后上述改变明显减轻或恢复至正常组水平。结论 :当归注射液能有效调节花生四烯酸代谢产物和氧自由基水平 ,对治疗脑血栓效果明显。  相似文献   
102.
103.
A solid phase radioimmunoassay has been compared with an enzyme-linked immunosorbent assay (ELISA) for efficacy in measuring anti-chromatin antibodies. The low backgrounds achieved with the radioimmunoassay method produced a high signal-to-noise ratio and enabled detection of the human test antiserum at a dilution of 1:102,400. By contrast, the ELISA could detect the same antiserum only at a dilution of 1:3200 and above. The radioimmunoassay was consistently more sensitive than the ELISA for detection of anti-chromatin antibodies in a number of human and mouse sera and ascites fluid containing a monoclonal antibody. Factors affecting sensitivity in both assays are discussed.  相似文献   
104.
An acoustical technique has been developed for the measurement of structural symmetry of the hip joints. A mild vibratory force was applied to the sacrum and sound signals were picked up at both hips by a pair of microphones installed in two stethoscopes. These stethoscope–microphone assembles were calibrated to achieve a difference in relative sensitivity of less than 0.2 dB. The relative transmission of sound signals was analysed and compared between both hips by a dual-channel signal analyser. Twenty-seven healthy adults, 20 healthy pre-school children and 19 normal neonates were tested. Results from these three groups showed high coherence of the sound signals and that the discrepancy between both hips was smallest in the frequency range of 200–315 Hz. For normal neonates, the sound signals maintained a high coherence (γ2>0.97) and small discrepancy (D<1.25 dB) between both hips. This study has shown that the acoustical technique provides a practical structural testing for bony symmetry of the hips and the results offer a baseline for further investigation into developmental dysplasia of the hip (DDH) in neonates. Clinical screening for DDH is still problematic in developing countries.  相似文献   
105.
Mimicking cell membrane and the biomolecular recognition associated with membranes represents a great technical challenge, yet it has opened doors to innovative diagnostic and therapeutic methods. Our work has focused on design and synthesis of a class of smart materials exploiting biological principals for use in biosensors: these materials are functional polymeric assemblies that mimic the cell membrane and conveniently report the presence of pathogens with a color change. Biologically active cell membrane components are incorporated into conjugated polymers with desirable optical properties and the binding of the target molecules onto the material triggers conformational and electronic shifts that are reflected in a chromatic change (a so-called biochromic shift) that is conveniently observed and recorded. Langmuir–Blodgett thin films and vesicle bilayers provide ideal configurations for precise delivery of the biological binding entity to the sensing interface, and for control of molecular orientation for effective biomolecular interaction. Polydiacetylenic membrane-mimicking materials containing cell surface receptor gangliosides and sialic acid residues, respectively were formulated into these architectures and used for colorimetric detection of bacterial toxins and influenza virus. One advantage of these biochromic conjugated polymer (BCP) sensors is that their molecular recognition and signal transduction functionalities are resident in a single functional unit, making them amenable to convenient microfabrication and use.  相似文献   
106.
Ashdown's medium, Burkholderia pseudomallei selective agar (BPSA), and a commercial Burkholderia cepacia medium were compared for their abilities to grow B. pseudomallei from 155 clinical specimens that proved positive for this organism. The sensitivity of each was equivalent; the selectivity of BPSA was lower than that of Ashdown's or B. cepacia medium.  相似文献   
107.
The involvement of the pituitary in cases of toxoplasmosis has been described in the literature only rarely. This is the first report to describe pituitary adenoma in association with Toxoplasma gondii infection. The two patients were 43 and 19 year old women. Radiological examination revealed tumours in the sellar region. Microscopically, the tumours consisted of small homogeneous polygonal or round cells. Toxoplasma cysts were found among the tumour cells, a finding confirmed by Toxoplasma gondii specific antibody immunohistochemistry. The association between pituitary adenoma and toxoplasma raises the possibility that T gondii might be involved in the development of certain cases of pituitary adenoma.  相似文献   
108.
Mycobacterium bovis infection of cattle represents a natural host-pathogen interaction and, in addition to its economic and zoonotic impact, represents a model for human tuberculosis. Extravasation and trafficking of activated lymphocytes to inflammatory sites is modulated by differential expression of multiple surface adhesion molecules. However, effects of M. bovis infection on adhesion molecule expression have not been characterized. To determine these changes, peripheral blood mononuclear cells from M. bovis-infected cattle were stimulated with M. bovis purified protein derivative (PPD) or pokeweed mitogen (PWM) and evaluated concurrently for proliferation and activation marker expression. Stimulation with PPD or PWM increased CD25 and CD44 mean fluorescence intensity (MFI) and decreased CD62L MFI on CD4(+) cells from infected animals. CD62L MFI on PPD- and PWM-stimulated gammadelta T-cell receptor-positive (TCR(+)) and CD8(+) cells was also reduced compared to that of nonstimulated gammadelta TCR(+) and CD8(+) cells. Using a flow cytometry-based proliferation assay, it was determined that proliferating cells, regardless of lymphocyte subset, exhibited increased expression of CD25 and CD44 and decreased expression of CD62L compared to cells that had not proliferated. In contrast to proliferation, activation-induced apoptosis of CD4(+) cells resulted in a significant down regulation of CD44 expression. Lymphocytes obtained from lungs of M. bovis-infected cattle also had reduced expression of CD44 compared to lymphocytes from lungs of noninfected cattle. These alterations in surface molecule expression upon activation likely impact trafficking to sites of inflammation and the functional capacity of these cells within tuberculous granulomas.  相似文献   
109.
In the pancreas, 3 types of morphologically similar lesions may present as "squamous cysts": Lymphoepithelial cysts, dermoid cysts (monodermal teratomas), and epidermoid cysts in intrapancreatic accessory spleen. Lymphoepithelial cysts (LECs) are seen predominantly in men (M/F: 4/1) and in adulthood (mean age, 56, and range, 35 to 74 years). They may occur at any site of the organ (head, body, or tail). LECs are well-delineated cysts that may be multilocular (60%) or unilocular (40%), and they are characterized microscopically by stratified squamous epithelium surrounded by a band of mature lymphoid tissue with intervening well-formed germinal centers. Solid lymphoepithelial clusters are seldom seen. The pathogenesis of LECs is unclear; clinical diseases that are known to be associated with their counterparts in the salivary glands such as Sjogren disease or human immunodeficiency virus have not been documented for the LECs of the pancreas. The second type of squamous-lined cyst in the pancreas is the epidermoid cyst arising in intrapancreatic accessory spleen. These are located almost exclusively in the tail of the pancreas, in the fourth decade of life (mean age = 38). Their mean size is 4.5 cm (range, 2.3 to 6.5). In some cases, the cyst lining may be partly mucinous. Dermoid cysts of the pancreas are also rare. The cases that appear to be true dermoid cysts occur in a younger age group (mean age, 23, range, 2 to 53 years), and in contrast with LEC, there is no gender predominance. Mucinous epithelium, respiratory-type mucosa and sebaceous units are more readily identifiable in dermoid cysts, and they may contain hair. Subepithelial lymphoid tissue is not a feature. They are sometimes complicated by suppurative infections. The importance of these lesions is in their distinction from other cystic neoplasms, especially mucinous cystic tumors.  相似文献   
110.
KOCH三角的解剖   总被引:6,自引:0,他引:6  
本实验解剖了110例人心标本(成人70、儿童40)的Koch三角区,观察和测量了房室结的形态、大小、毗邻和标志。房间隔及冠状窦口上、下方均有肌束连于房室结。Todaro腱在儿童多全部为腱性;在成人,其后部为肌性。三角区的深面为左、右心房壁和室间隔顶所构成的锥形间隙,其内为进入房室结区的血管和神经。根据构成不同,可将三角区分为5个区,即前上角的纤维支架区和房室结区,其余部分自上向下分别为房间隔区、右房壁区和室间隔区。本文还讨论了这些形态结构的功能及外科意义。  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