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   62882篇
  免费   5596篇
  国内免费   2618篇
耳鼻咽喉   712篇
儿科学   1564篇
妇产科学   1204篇
基础医学   6413篇
口腔科学   1199篇
临床医学   5913篇
内科学   5757篇
皮肤病学   796篇
神经病学   2258篇
特种医学   3401篇
外国民族医学   53篇
外科学   7867篇
综合类   10875篇
现状与发展   19篇
预防医学   1751篇
眼科学   708篇
药学   4345篇
  44篇
中国医学   2046篇
肿瘤学   14171篇
  2024年   123篇
  2023年   895篇
  2022年   1577篇
  2021年   2729篇
  2020年   2178篇
  2019年   1964篇
  2018年   1814篇
  2017年   2088篇
  2016年   2364篇
  2015年   2525篇
  2014年   3834篇
  2013年   3917篇
  2012年   3530篇
  2011年   3895篇
  2010年   3198篇
  2009年   3229篇
  2008年   3203篇
  2007年   3492篇
  2006年   3150篇
  2005年   2810篇
  2004年   2408篇
  2003年   2026篇
  2002年   1894篇
  2001年   1691篇
  2000年   1372篇
  1999年   1242篇
  1998年   1059篇
  1997年   986篇
  1996年   855篇
  1995年   764篇
  1994年   647篇
  1993年   509篇
  1992年   420篇
  1991年   349篇
  1990年   273篇
  1989年   267篇
  1988年   258篇
  1987年   213篇
  1986年   162篇
  1985年   211篇
  1984年   192篇
  1983年   123篇
  1982年   157篇
  1981年   133篇
  1980年   88篇
  1979年   88篇
  1978年   63篇
  1977年   44篇
  1976年   40篇
  1975年   16篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
肺癌患者血清一氧化氮浓度变化的观察   总被引:1,自引:0,他引:1  
于兰  陈新民 《天津医药》1999,27(10):596-597
为了解肿瘤患者体内NO变化规律,应用萘乙烯二胺盐酸盐显色法对25例健康人及18例肺癌患者者进行了血清NO含量测定,同时采用放射免疫法进行了TNF-α及SOD平行测定。结果示,肺癌患者血清NO及TNF-α含量明显高于对照组,而血清SOD含量明显低于对照组,NO含量与TNF-α及SOD含量间不存在明显相关性变化,肺癌患者血清,NO浓度随病情严重程度及病程延长而增加,与肿瘤病理分型无明显相关。  相似文献   
992.
Virtually every variant of neuroendocrine neoplasia can occur, at least rarely, in the head and neck region. This review focuses on the terminology surrounding neuroendocrine carcinomas of the larynx and their distinction from morphologically similar but biologically distinctive neoplasmas. It is suggested that rare typical laryngeal carcinoids be labeled as such. There is little evidence that these lesions are part of a morphologic continuum. In contrast, more common “carcinoid-like” carcinomas, previously referred to as “atypical carcinoids” are more appropriately labeled as “moderately differentiated neuroendocrine carcinomas”. These neoplasms should, in turn, be distinguished from “small cell neuroendocrine carcinomas,” although these latter two neoplasms do represent a morphologic and behavioral spectrum. Light microscopic and immunohistochemical features distinguishing neuroendocrine carcinomas of the larynx from paraganglioma, metastatic medullary carcinoma, malignant melanoma, and basaloid squamous cell carcinoma are presented. The second portion of this review outlines the clinicopathologic features of two head and neck neoplasms exhibiting varying degrees of neuroendocrine differentiation. Olfactory neuroblastomas have well-developed neuroendocrine differentiation, almost invariably arise from the olfactory mucosa, typically exhibit low-grade cytologic features, and may have protracted clinical course with an approximately 50% overall 5-yr survival. In contrast, sinonasal undifferentiated carcinoma is a microscopically high-grade neoplasm with minimal, abortive neuroendocrine features, a highly aggressive clinical course, and virtually 100% mortality. They can arise throughout the sinonasal region. Presented at the Endocrine Pathology Society—USCAP Meeting, Washington, DC, March 23, 1996.  相似文献   
993.
Primary spinal cord primitive neuroectodermal tumor (PNET) is a rare entity. In all, 13 cases have been reported in the literature, including 3 with intracranial seeding. A 3-month-old girl with involvement of the spinal cord below the mid-thoracic level is described. The brain MRI revealed findings indicative of seeding along the intracranial subarachnoid space. Biopsy, duraplasty and removal of laminotomy flap were done. In spite of a good response to the first cycle of postoperative 8-drugs-in-a-day chemotherapy, further treatment was refused. She died 21 days after the onset of leg weakness, which reveals the rapid progression of untreated cases. To our knowledge, this is the first case of spinal cord PNET with parenchymal involvement that has been described in an infant.  相似文献   
994.
Summary The growth inhibitory effect of IFN- was evaluated in 5 human glioma cell lines (AO2V4, GJC, GJR, NN and NNR) and in normal astrocyte cultures (SC and TM). All 5 glioma cell lines showed an anti-proliferative response to IFN- whereas normal glial cells were non-responsive. IFN- at 10, 100 and 500 U/ml lead to a 30%,70% and 80% relative decrease in cell number after 12 days, respectively in AO2V4 cells. GJC and GJR cell lines also responded significantly to the lowest concentration of IFN- tested and at 500 U/ml the relative cell number decreased 55%. The NN and NNR cells were the least responsive to IFN- with maximum growth inhibition of 30% at 500 U IFN-/ml. Following treatment with IFN-, AO2V4, GJC, GJR and normal astrocytes all expressed mRNA encoding the anti-viral protein, 2-5A synthetase demonstrating that IFN- bound to receptors on all four cell lines and activated signal transduction pathways required for induction of an anti-viral protein. A determination of the relative number of viable cells showed that none of these cells exhibited a significant decrease in cell viability. Since the antiproliferative response to IFN- was not primarily due to cell death, the effect of IFN- on cell cycle progression was evaluated by flow cytometry. All treated glioma cell lines showed a relative increase in proportion of cells in S phase. AO2V4 cells had a 50%–80% increase in the percentage of cells in S phase, whereas GJC, GJR and NNR had percentage increases of 20%–40%. IFN- treatment of normal astrocytes did not significantly alter their cell cycle profile. These data suggest that IFN- exerts its antiproliferative effect on glioma cells by arresting the ordered progression through S phase or decreasing entry into G2/M phase of the cell cycle.  相似文献   
995.
Summary In this prospective study, the authors examined 50 patients with breast tumors (malignant, n = 32; benign, n = 18) to investigate the correlation between color Doppler flow mapping and histopathological findings and to evaluate the clinical significance of color Doppler mapping. Among the 32 patients with breast cancer, color Doppler signals were detected in 24 patients (75%). The maximum flow velocities varied from 5 to 34 cm/sec, with 16 (67%) of them above 15 cm/sec. Among the 18 patients with benign tumors, color Doppler signals could be detected in 7 (39%). The maximum flow velocity varied from 3 to 30 cm/sec but was over 15 cm/sec in only two patients (28%). Histological studies revealed that color Doppler signals detected by Doppler sonography correlated with disordered neovascularization penetrating the lesion from its periphery, consisting of thin-walled blood vessels and large arteriovenous shunts. Although large tumors tend to have high Doppler flow, there is no significant correlation between the maximum flow velocity and tumor size. There is also no significant correlation between the detection of high flow color Doppler signals and the age, receptor status, tumor size, lymph node metastases, or clinical stage of patients with breast cancer. However, there is a positive association (p < 0.05) between nodal metastases and higher tumor flow velocity in T1 ( 2 cm) breast tumors, but not in larger tumors. It is concluded that color Doppler is useful in the assessment of tumor vascularity but is of limited value in the differentiation of benign from malignant lesions. However, the presence of color Doppler signals in Tl breast cancer suggesting early dissemination of the cancer might be of important clinical significance in detecting those small, apparently early, but aggressive tumors with poor prognosis.  相似文献   
996.
This study was conducted to investigate the role of tumor necrosis factor- (TNF-) and interleukin-2 (IL-2) in inducing cancer cachexia, and the results were compared with those obtained from our previous study on Fisher 344 rats with methylcholanthrene-induced sarcoma. Three groups of male Fisher 344 rats received one of the following regimens: 4×104 IU of human recombinant TNF- per rat per day subcutaneously (sc) for 5 consecutive days (n=5), 3.5×105 U human recombinant IL-2 per rat per day sc for 14 consecutive days (n=5), or normal saline (n=5). The activities of both phosphoenolpyruvate carboxykinase (PEPCK) and malic enzyme (ME) were increased slightly in the IL-2 group. Furthermore, LPL activity was significantly increased in the adipose tissue of the TNF group and in the cardiac muscle of the IL-2 group, but not in that of the TNF group. These results show that there is a significant difference between the metabolic alterations seen in the tumor-bearing state and those induced by either TNF- or IL-2 alone. Thus, it is unlikely that IL-2 or TNF- is the sole mediator of cancer cachexia in this tumor and rat model.  相似文献   
997.
Serum carcinoembryonic antigens (CEA), CA 15-3, and tissue polypeptide antigens (TPA) have been used in monitoring the clinical course of patients with breast cancer. However, recent reports have suggested that the serial levels of these markers during therapy do not always correlate with the response to therapy. To clarify the usefulness of the serial combination assay of these markers in monitoring the clinical course of patients during therapy, we investigated the relationship between the initial changes and the kinetic patterns of the markers after therapy and the objective responses. When an increase or decrease of over 20% in these markers is taken to be significant, then the initial changes in all three markers significantly correlated with the therapeutic responses (P<0.01). Five distinct kinetic patterns in the marker levels were observed. A paradoxical kinetic pattern of CEA and CA 15-3 levels — that is, an initial surge and subsequent drop — was seen in one-third of the responders. The TPA levels tended to exhibit a steady decline pattern in those responders. The sensitivity and specificity of the kinetic patterns to predict the clinical courses were significantly higher than those obtained from the analysis of initial changes. These findings thus suggest that adequate knowledge of the unique kinetics of each marker may help to make a more accurate prediction of the therapeutic responses.  相似文献   
998.
We herein report the usefulness of ultrasoundguided percutaneous needle biopsy for histological diagnosis in 18 patients with mediastinal tumors. Computed tomography revealed these tumors to be in contact with the chest wall. The preoperative diagnosis was thymoma in 7 patients, germinoma in 5, neurogenic tumor in 3, and other in 3. The most commonly encountered indication for an ultrasound-guided percutaneous needle biopsy was an anterior mediastinal lesion (78%; 14 of 18 patients). In 16 (89%) of the 18 patients, the biopsy diagnosis corresponded to the post-operative diagnosis. No complications were encountered in any of the patients. This new technique of ultrasound-guided percutaneous needle biopsy is both relatively simple and highly accurate and may thus be useful for outpatients. Preoperative ultrasound-guided percutaneous needle biopsy is thus considered to be a safe and reliable method for the histological diagnosis of mediastinal tumors, and a good alternative to traditional biopsy techniques such as mediastinoscopy or thoracotomy.Presented at the 11th Biennial Asian Congress on Thoracic and Cardiovascular Surgery, Kuala Lumpur, Malaysia, November, 21–25, 1993.  相似文献   
999.
A huge phyllodes tumor of the breast that appeared grossly malignant in a 43-year-old woman is described. The patient suffered from a large breast tumor that suddenly increased in size over 5 months to occupy the entire breast. The tumor was hard, ulcerated and 20 cm in greatest diameter. Diagnostic imaging (US, CT and MRI) demonstrated a circumscribed mass with a large cystic cavity. She underwent total mastectomy under a diagnosis of malignant breast tumor. Grossly, the cut surface of the tumor showed a large cystic cavity surrounding a fleshy, hemorrhagic and necrotic mass with a lobulared or trabeculared appearance. Unexpectedly, benign phyllodes tumor (PT) without any stromal overgrowth was diagnosed histologically. She has been doing well since total mastectomy. In our case and in many other reported cases, PT does not show any distinctive correlation between pathologic findings and tumor behavior. Thus wide local excision is the preferred initial treatment for PT.  相似文献   
1000.
Pollen JJ 《The Prostate》1980,1(2):251-258
This report reviews the roles of conventional radiography, computerized axial tomography, and nuclear bone scanning in the diagnosis, staging, follow-up, and management of prostatic cancer. Computed tomography (CT) offers great promise for the better definition of the extent of the primary tumor of prostatic cancer. It contributes positively to the planning of radiation therapy portals in the treatment of localized disease. By means of bipedal lymphangiography and CT scanning, pelvic and periaortic lymphadenopathy may be detected more often than was previously possible without staging pelvic lymphadenectomy, which can be reserved for the discovery of microscopic disease. Soft-tissue metastases that are located deep within the body cavities can now be measured accurately by CT scanning, as can their response to therapy. Skeletal metastases, the most common variety in prostatic cancer, can be detected with a high degree of sensitivity by nuclear bone imaging. Serial bone scans are remarkably useful in following the response of osseous deposits to treatment, as well as in detecting relapsing disease. The management of malignant obstruction of the ureters has been greatly facilitated by the application of angiographic techniques to percutaneous nephrostomy performed under fluoroscopic control.  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