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   70832篇
  免费   5282篇
  国内免费   476篇
耳鼻咽喉   816篇
儿科学   1887篇
妇产科学   1547篇
基础医学   8940篇
口腔科学   1247篇
临床医学   7054篇
内科学   16046篇
皮肤病学   1388篇
神经病学   5591篇
特种医学   2327篇
外国民族医学   1篇
外科学   9843篇
综合类   1618篇
一般理论   48篇
预防医学   4829篇
眼科学   2325篇
药学   5276篇
  1篇
中国医学   365篇
肿瘤学   5441篇
  2023年   388篇
  2022年   629篇
  2021年   1566篇
  2020年   987篇
  2019年   1381篇
  2018年   1715篇
  2017年   1295篇
  2016年   1449篇
  2015年   1681篇
  2014年   2383篇
  2013年   3135篇
  2012年   4602篇
  2011年   4786篇
  2010年   2710篇
  2009年   2423篇
  2008年   4168篇
  2007年   4476篇
  2006年   4522篇
  2005年   4381篇
  2004年   4102篇
  2003年   3885篇
  2002年   3667篇
  2001年   1382篇
  2000年   1241篇
  1999年   1225篇
  1998年   845篇
  1997年   647篇
  1996年   608篇
  1995年   542篇
  1994年   502篇
  1993年   465篇
  1992年   667篇
  1991年   604篇
  1990年   579篇
  1989年   545篇
  1988年   499篇
  1987年   536篇
  1986年   461篇
  1985年   442篇
  1984年   474篇
  1983年   389篇
  1982年   428篇
  1981年   367篇
  1980年   345篇
  1979年   254篇
  1978年   251篇
  1977年   227篇
  1976年   222篇
  1975年   186篇
  1974年   155篇
排序方式: 共有10000条查询结果,搜索用时 203 毫秒
91.
Akt, a Serine/Threonine protein kinase, mediates growth factor-associated cell survival. Constitutive activation of Akt (phosphorylated Akt, P-Akt) has been observed in several human cancers, including lung cancer and may be associated with poor prognosis and chemotherapy and radiotherapy resistance. The clinical relevance of P-Akt in non-small cell lung cancer (NSCLC) is not well described. In the present study, we examined 82 surgically resected snap-frozen and paraffin-embedded stage I to IIIA NSCLC samples for P-Akt and Akt by Western blotting and for P-Akt by immunohistochemistry. P-Akt protein levels above the median, measured using reproducible semiquantitative band densitometry, correlated with a favorable outcome (P = 0.007). Multivariate analysis identified P-Akt as a significant independent favorable prognostic factor (P = 0.004). Although associated with a favorable prognosis, high P-Akt levels correlated with high tumor grade (P = 0.02). Adenocarcinomas were associated with low P-Akt levels (P = 0.039). Akt was not associated with either outcome or clinicopathologic variables.Cytoplasmic (CP-Akt) and nuclear (NP-Akt) P-Akt tumor cell staining was detected in 96% and 42% of cases, respectively. Both CP-Akt and NP-Akt correlated with well-differentiated tumors (P = 0.008 and 0.017, respectively). NP-Akt also correlated with nodal metastases (P = 0.022) and squamous histology (P = 0.037).These results suggest P-Akt expression is a favorable prognostic factor in NSCLC. Immunolocalization of P-Akt, however, may be relevant as NP-Akt was associated with nodal metastases, a known poor prognostic feature in this disease. P-Akt may be a potential novel therapeutic target for the management of NSCLC.  相似文献   
92.
The appearance of an acute effusion in a well-pneumatized temporal bone directs attention to the nasopharynx and skull base. Two patients are described in whom dehiscence of the temporomandibular joint allowed herniation of the contents of the joint posteromedically, where they obstructed the middle ear entrance of the eustachian tube, the protympanum. This is, to the authors' knowledge, a previously unreported cause of an acute middle ear and mastoid effusion.  相似文献   
93.
The clinical presentation and the biochemical and molecular genetic findings are described in a 13 year old Chinese boy with MELAS (mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes). The diagnosis was initially suspected because of the characteristic clinical features and the strong family history of convulsions. Using polymerase chain reaction—restriction enzyme analysis, the heteroplasmic nt3243 A→G mutation in mtDNA of peripheral blood leucocytes and a muscle sample was demonstrated. The oligosymptomatic relatives were then screened by this method and the degree of heteroplasmy was analysed. This appears to be the first report of a MELAS family in Hong Kong with this described mutation. Molecular genetic techniques are advantageous in the diagnosis of MELAS.  相似文献   
94.
应用双光子及单光子吸收测定技术,检测了92名出生3d内的新生儿骨矿质含量,其中巨大儿30名,正常体重儿32名,低出生体重儿30名,其孕龄分别是40.1±0.7、39.1±1.5和37.4±1.2孕周。结果表明,巨大儿、正常体重儿、低出生体重儿的全身骨矿质含量分别是101.6±28.8、85.2±19.8、59.9±27.2g/cm2,巨大儿骨矿质含量最高,正常体重儿次之,低出生体重儿最低,差异有显著性(P<0.01)。颅骨、肱骨、股骨的骨矿质含量与全身的骨矿质含量有高度的相关性,相关系数分别是0.943、0.879和0.745(P<0.01)。全身的骨矿质含量与出生体重、孕龄及头围有高度相关性,相关系数分别是0.755、0.596和0.556(P<0.01)。提示颅骨、肱骨及股骨的任一部位均可代表全身的骨矿质含量,肱骨是确定全身骨矿质含量较好的部位,新生儿骨矿质含量受出生体重、孕龄及头围的影响较大。  相似文献   
95.
Immunopathologic study of Vogt-Koyanagi-Harada syndrome   总被引:9,自引:0,他引:9  
We studied an enucleated eye from a patient with a 30-year history of Vogt-Koyanagi-Harada syndrome using both conventional and immunohistochemical techniques. Clinically, the eye was in the end stage of Vogt-Koyanagi-Harada syndrome, and was characterized by the absence of inflammation, large areas of chorioretinal scarring, and pigmentary changes. Histopathologic examination showed marked retinal gliosis, extensive chorioretinal adhesion and scar formation, migration of pigment into the retina, and severe retinal pigment epithelial changes. However, foci of mild to moderate nongranulomatous inflammation of the uvea were observed. These foci contained infiltrating cells that were mainly T lymphocytes with B lymphocyte aggregates at the center. Scattered macrophages were also noted in the uvea and retina. These findings suggest that both the cell-mediated and humoral immune arms may play roles in the pathogenesis of Vogt-Koyanagi-Harada syndrome.  相似文献   
96.
Studies on the effectiveness of pain management have uniformly concluded that health care providers underestimate or undertreat pain. In the emergency department (ED) in which this study was conducted, physicians receive formal didactic and bedside teaching on pain recognition and management in order to heighten the awareness of patient's need for pain control. The purpose of this study was to determine if this outpatient pain management of patients with acute, painful conditions is better than that reported in the medical literature. In this prospective study, 110 adult patients who had an acute, painful diagnosis were telephoned 48 hours after discharge from the ED and asked if they felt their pain at home was well controlled. Patient satisfaction with pain control was higher (91%) than that reported in the medical literature. Also, pain medication was provided more frequently by this study's ED (95%). Education on pain awareness and treatment is a way to improve pain management.  相似文献   
97.
98.
Studies of the ontogeny of IGF-I mRNA during embryonic and larval development of the gilthead sea breamSparus auratashowed its expression during these early developmental stages. The present study appliesin situhybridization to localize IGF-I and IGF receptor mRNAs in 16-day larvae ofS. aurata.Paraffin sections were hybridized with homologous RNA probes labeled by [35S]UTP. IGF-I mRNA expression was found mainly in chondrocytes, in both the gill arches and cranial cartilage, in skeletal muscle, in the brain, in the pancreas, in the retina, and in the epithelial cells surrounding the lens. A strong positive reaction for IGF receptor mRNA was found in skeletal muscle, in the pancreas, and in the lymphoid tissue found in the intertubular tissue of the kidney. Signals were less intense in brain and chondrocytes. It is suggested that in teleosts, as in higher vertebrates, IGF-I may be involved in the regulation of tissue growth and differentiation in an autocrine/paracrine manner.  相似文献   
99.
. We have estimated sarcoplasmic reticulum calcium content using rapid application of caffeine on voltage clamped, isolated guinea-pig ventricular myocytes. Caffeine induces the release of calcium from the sarcoplasmic reticulum and this calcium is extruded from the cells by the sarcolemmal Na/Ca exchange. Integrating the inward Na/Ca exchange current thus allows estimations of sarcoplasmic reticulum calcium content. Ventricular myocytes were stimulated to reach new steady-states by action potential voltage clamps of varying duration. Once contractile steady-state had been reached caffeine was rapidly applied in place of the next action potential and sarcoplasmic reticulum calcium content measured. Prolonging the action potential duration increased sarcoplasmic reticulum calcium content and vice-versa. This calcium loading may underlie the positive inotropic effect of increased action potential duration. Received: 11 July 1996 / Received after revision: 15 October 1996 / Accepted: 26 November 1996  相似文献   
100.
Although the leading causes of fever and pulmonary infiltrates in sickle cell patients are acute bacterial pneumonia and the acute chest syndrome, the former is usually responsive to antibiotics and not protracted, and the clinical course of the latter is short and self-limited. A patient with sickle cell anemia presented with fever and pulmonary infiltrates of several weeks duration that were unresponsive to antibiotics. Gross endobronchial abnormalities were noted on bronchoscopy, and the biopsies were consistent with sarcoidosis. The diagnosis of sarcoidosis can be difficult to establish in a patient with sickle cell anemia and protracted fever since both disorders are associated with chronic interstitial changes on the chest radiograph as well as restrictive physiology.  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