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   347214篇
  免费   22848篇
  国内免费   7758篇
耳鼻咽喉   4174篇
儿科学   9590篇
妇产科学   6589篇
基础医学   29094篇
口腔科学   8127篇
临床医学   38260篇
内科学   43377篇
皮肤病学   4608篇
神经病学   19571篇
特种医学   8168篇
外国民族医学   35篇
外科学   37533篇
综合类   51561篇
现状与发展   12篇
一般理论   29篇
预防医学   35161篇
眼科学   5439篇
药学   30379篇
  391篇
中国医学   31532篇
肿瘤学   14190篇
  2023年   5572篇
  2022年   9895篇
  2021年   13581篇
  2020年   12668篇
  2019年   18566篇
  2018年   16077篇
  2017年   12997篇
  2016年   10551篇
  2015年   9869篇
  2014年   20250篇
  2013年   21695篇
  2012年   18576篇
  2011年   20039篇
  2010年   16146篇
  2009年   14834篇
  2008年   14433篇
  2007年   14858篇
  2006年   12966篇
  2005年   11257篇
  2004年   9222篇
  2003年   8062篇
  2002年   6412篇
  2001年   5693篇
  2000年   4683篇
  1999年   4075篇
  1998年   3310篇
  1997年   3150篇
  1996年   2731篇
  1995年   2623篇
  1994年   2522篇
  1993年   2010篇
  1992年   2040篇
  1991年   1766篇
  1990年   1572篇
  1989年   1400篇
  1988年   1339篇
  1987年   1145篇
  1985年   3817篇
  1984年   4810篇
  1983年   3356篇
  1982年   3810篇
  1981年   3557篇
  1980年   3161篇
  1979年   2911篇
  1978年   2542篇
  1977年   1909篇
  1976年   2153篇
  1975年   1632篇
  1974年   1430篇
  1973年   1278篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
A case of unusual longevity to the age of 58 years is reported for a female patient with complete transposition of the great arteries. The association with a wide atrial septal defect with intact interventricular septum may have contributed to the long survival without surgery. Factors determining intercirculatory mixing and systemic oxygen saturation may be the high pulmonary flow, the location of the anatomic communication, sufficient hemoglobin concentration to allow an adequate level of systemic resistance and recirculated systemic flow, and the belated development of pulmonary vascular disease.  相似文献   
992.
The policy and health service background to this discussion are the radical changes in cancer services currently underway in the wake of the Calman-Hine Report and the wider changes ushered in by the NHS and Community Care Act 1990 (UK). Using the changing face of hospice care as the focus, the authors explore some of the potential issues and dilemmas involved in providing supportive care for cancer patients and their families. Three 'themes', or areas of concern, are highlighted: links between services, changing organizational factors, and increasing 'medical imperialism'. Potential benefits and drawbacks of the changing ethos and organizational structures are discussed. Interview data are used as 'triggers' for the presentation of the authors' own reflections on developments in the hospice and cancer services' arenas. The paper draws on interview data collected in the pilot phase of a 3-year study on the psycho-social needs of cancer patients and their informal carers in north-west England. Twenty-nine interviews were conducted with a range of professionals involved in the provision of cancer services in Lancaster and Kendal. In the spirit of 'gathering thoughts' and facilitating debate, a commentary on developments in the hospice sector is offered rather than any firm conclusion.  相似文献   
993.
Objectives: This study was carried out to evolve a method to improve the registration of cancer mortality data in Chennai (Madras, India). Methods: Data on cancer deaths have been collected from the Vital Statistics Department (VSD) by a population-based cancer registry (PBCR) in Chennai only since 1982. The low mortality-to-incidence ratio during 1982-84 suggested under-registration of mortality data. Since 1985, the PBCR has taken special effort to ascertain the vital status of cancer cases by sending reply-paid postcards and/or making house visits. The data on all deaths occurring in Chennai, irrespective of stated cause of death in the death certificate, have been collected from the VSD since 1992. Results: Deaths that occurred in Chennai and obtained by sending reply-paid postcards and/or making house visits were registered in VSD as non-cancer causes of death; hence, these data were not collected from VSD. The sensitivity and positive predictive values of death certificates on cancer diagnosis based on 1992 and 1993 mortality data were 57 percent and 99.5 percent, respectively. Conclusion: Since the accuracy of death certificate information on cancer diagnosis is relatively low in a developing country such as in India, collecting data on all deaths will improve the mortality data registration in PBCRs.  相似文献   
994.
Although the osteosarcoma is considered to be among the most chemosensitive malignancies and preoperative chemotherapy is commonly applied, an appreciable proportion of cases are in fact quite insensitive. Predictive markers for chemosensitivity are therefore desirable in order to develop effective treatment strategies. Thirty-two cases of conventional osteosarcomas treated at the Cancer Institute Hospital, Tokyo, were analyzed. The sensitivity to preoperative chemotherapy was investigated with reference to loss of heterozygosity (LOH) at the 17p13 ( p 53) and 13q14 ( Rb ) loci and expression of the cell-cycle associated proteins, p53, Rb, p21/Waf-1, mdm-2 and Ki-67, as detected immunohistochemically. LOH was detected by analyzing polymerase chain reaction products at marker microsatellite loci. The efficacy of chemotherapy was evaluated both radiologically and histologically. LOH at p 53 or Rb loci was seen in 54% (13/24) and 58% (14/24) of cases, respectively. Only 15% of osteosarcomas with LOH at the p 53 locus were sensitive to preoperative chemotherapy, as compared to 64% of tumors without such loss ( P <0.05). A similar but much less distinct tendency was observed with LOH at the Rb locus. No relationship was evident between chemosensitivity and immunohistochemical staining patterns for p53, Rb, p21/Waf-1, mdm-2 or Ki-67. The results suggest that p 53 gene deletion, but not the other parameters investigated, may be useful for predicting chemoresistance of osteosarcomas.  相似文献   
995.
目的本研究利用人血白蛋白免疫损伤Wister大鼠造成肝纤维化模型,以观察“抑肝纤”对大鼠肝纤维化的阻断作用。方法将不同浓度中药“抑肝纤”用于治疗组并与模型组和对照组进行对比,综合分析血清肝纤维化指标、肝组织病理改变、肝组织胶原纤维和网状纤维病理图像定量分析等结果。结果治疗组血清肝纤维化指标(PCⅢ、HA、LN)均低于模型组,接近正常组,差异有显著性(P<0.001或P<0.05)。光镜下肝组织病理变化,肝组织中胶原纤维和网状纤维病理图像定量分析结果治疗组优与模型组,尤以低浓度组更为明显(P<0.005或P<0.05)。结论研究结果表明,中药“抑肝纤”如能早期应用,可有效地阻断或延缓实验鼠肝纤维化的发生  相似文献   
996.
Objective: To establish tissue inhibitor of metalloproteinase-1 (TIMP-1) concentrations in peritoneal fluid (PF) and sera of women with endometriosis and compare them to disease-free controls.

Design: Prospective randomized study.

Setting: Academic medical center.

Patient(s): Women with laparoscopically documented endometriosis and disease-free women of reproductive age.

Intervention(s): Peritoneal fluid and sera were collected, and some women received gonadotropin-releasing hormone agonist (GnRH-a) therapy for endometriosis.

Main Outcome Measure(s): Peritoneal fluid and sera TIMP-1 concentrations were measured with a specific RIA.

Result(s): The TIMP-1 concentrations were significantly lower in PF and sera of women with endometriosis compared with disease-free women. The GnRH-a therapy restored serum TIMP-1 concentrations.

Conclusion(s): Aberrant expression and localization of TIMP-1 may derange the proteolytic milieu of the peritoneal cavity and contribute to the etiology and underlying physiologic sequelae associated with endometriosis. Measurement of TIMP-1 in serum may aid in diagnosing endometriosis and assist with monitoring treatment efficacy in women with this disease.  相似文献   

997.
养血清脑颗粒治疗老年期痴呆的临床疗效观察   总被引:1,自引:0,他引:1  
目的:观察养血清脑颗粒对老年期痴呆的疗效。方法:治疗组老年期痴呆患者36例均应用养血清脑颗粒。详录治疗前后实验室检查数据。健康老年人34例为对照组,以其体检时所得相关指标与治疗组比较分析。结果:有效率85%,S-TC明显下降,P-SOD明显升高,P-LPO,Ht,Va降低、EET缩短。结论:养血清脑颗粒具有降脂、抗自由基损伤。改善异常血液流变,增加脑血流量等功用。对老年期痴呆防治有较好效果。  相似文献   
998.
药用老鹳草原植物分布概述   总被引:1,自引:1,他引:1  
通过对药用老鹳草常用品种及其同属原植物地区分布的概述,总结了目前国内外对药用老鹳草研究的各品系,为今后规范中药材的使用,以及开发更多的代用品提供相关前期基础。  相似文献   
999.
本文讨论了以分层法进行中药药效评价时权重设立的问题,主要由以下几部分组成:1.建立递阶层次结构;2.构造两两比较判断矩阵;3.计算单一准则下元素的相对权重;4.计算各层元素的组合权重。由于中药作用具有多途径、多靶点的特性,因此评价过程中权重的设立就占有重要位置。它直接影响对被评价对象药效作用的评判。全面解决中药作用多途径、多靶点药效学评价的数学方法,客观量化的评价中药的综合药效,是中药现代化进程中一个值得研讨的命题。  相似文献   
1000.
男性胰腺实性-假乳头状瘤2例临床病理观察   总被引:4,自引:1,他引:4  
目的探讨胰腺实性-假乳头状瘤(SPT)的临床病理特征及了解分子病理学研究进展。方法2例SPT分别作HE、PAS、免疫组织化学(S—P法)染色观察。结果2例SPT男性患者均有腹部包块及腹痛症状。术后均无复发。肿块体积较大,囊实性相间。镜下瘤细胞围绕纤维血管形成特征性的假乳头结构,并可见退行性变、出血和泡沫细胞。免疫组化结果:2例AACT、ACT、Cga和Syn均为阳性,PR、ER、Ck和Ins均为阴性,1例Vim为阳性。结论胰腺SPT为具有独特临床病理特征的低度恶性肿瘤。  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