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   3234篇
  免费   220篇
  国内免费   15篇
耳鼻咽喉   46篇
儿科学   314篇
妇产科学   48篇
基础医学   448篇
口腔科学   148篇
临床医学   218篇
内科学   625篇
皮肤病学   84篇
神经病学   215篇
特种医学   66篇
外国民族医学   2篇
外科学   428篇
综合类   110篇
一般理论   9篇
预防医学   197篇
眼科学   63篇
药学   222篇
中国医学   23篇
肿瘤学   203篇
  2023年   25篇
  2022年   50篇
  2021年   113篇
  2020年   58篇
  2019年   88篇
  2018年   135篇
  2017年   84篇
  2016年   117篇
  2015年   104篇
  2014年   140篇
  2013年   188篇
  2012年   254篇
  2011年   228篇
  2010年   133篇
  2009年   134篇
  2008年   180篇
  2007年   187篇
  2006年   152篇
  2005年   116篇
  2004年   125篇
  2003年   99篇
  2002年   95篇
  2001年   50篇
  2000年   60篇
  1999年   48篇
  1998年   21篇
  1997年   16篇
  1996年   21篇
  1995年   12篇
  1994年   13篇
  1993年   15篇
  1992年   40篇
  1991年   33篇
  1990年   36篇
  1989年   41篇
  1988年   18篇
  1987年   23篇
  1986年   27篇
  1985年   24篇
  1984年   17篇
  1983年   16篇
  1982年   9篇
  1981年   11篇
  1980年   11篇
  1979年   15篇
  1978年   10篇
  1977年   10篇
  1976年   11篇
  1974年   12篇
  1973年   8篇
排序方式: 共有3469条查询结果,搜索用时 140 毫秒
1.
Nanocrystalline platinum with different morphologies is synthesized via electrochemical deposition technique. The nucleation mechanism and its structural effect over the electrodeposited Pt on carbon electrodes have been systematically studied. Powder X-ray diffraction, X-ray photoelectron spectroscopy, and field-emission scanning electron microscopy are employed to study nucleation, oxidation states, and Pt structure growth on a carbon electrode. This study reports significant development of Pt metal nanoparticles with different morphologies such as a sphere, flower, core-flower, and rod-like structure directly fabricated on carbon electrode while tuning the deposition parameters such as current density, time, temperature, pH during the deposition process. The proposed electrochemical route represents a superior fabrication procedure for large-scale electrode fabrication compared to a conventional method for preparing membrane electrode assemblies for fuel cell stacks.  相似文献   
2.
3.
Placement of tunnelled dialysis lines is effective using ultrasoundand fluoroscopic guidance [1] and has a higher success ratethan ‘blind’ insertion [2]. After the ultrasound guided access into a neck vein, wires andcatheters are guided in to a suitable position in the  相似文献   
4.
OBJECTIVE AND DESIGN: Bacterial products as well as the host airway inflammatory responses contribute to the pathogenesis of Pseudomonas infections. We sought to determine if Pseudomonas elastase (PE) induces mitogen-activated protein (MAP) kinase activity in association with interleukin-8 (IL-8) production by alveolar epithelial cells. METHODS: We utilized Western blot analysis to detect phosphorylation of signaling intermediates and ELISA was used to measure IL-8 production. RESULTS: We found that PE induces phosphorylation of the extracellular signal-regulated (ERK1/2) proteins of the MAPK pathway in A549 epithelial cells. Similar results were obtained using primary cultures of rabbit alveolar type II epithelial cells. PE also enhanced IL-8 production, which was abolished in the presence of the ERK activation inhibitor U0126. CONCLUSIONS: We conclude that PE activates the ERK1/2 arm of the MAPK pathway and that activation of this pathway results in enhanced IL-8 production. The results demonstrate that PE may augment pulmonary inflammation via cellular signaling that regulates expression of IL-8.  相似文献   
5.
Poliomyelitis trends in Pondicherry, south India, 1989-91.   总被引:1,自引:1,他引:0       下载免费PDF全文
STUDY OBJECTIVES: To assess the poliomyelitis trend, including study of the epidemiological features, and to correlate this with the immunisation coverage of infants. DESIGN: Three annual lameness surveys in children aged 0-60 months employing cluster sampling methods and a series of five cross sectional surveys of immunisation coverage in children aged 12-23 months of age were undertaken. SETTING: Pondicherry, India, 1988-92. SUBJECTS: More than 10,000 children in the age group of 0-60 months took part in the three annual lameness surveys and samples of 210 children aged 12-23 months were covered each year in immunisation coverage surveys. MEASUREMENTS AND MAIN RESULTS: Altogether 50 of 11,461, 24 of 10,093, and 17 of 11,218 children surveyed during 1989, 1990, and 1991 respectively had become lame as a result of poliomyelitis, giving prevalences of 4.4, 2.4, and 1.5 per 1000 children for the three surveys. The corrected prevalences of poliomyelitis were 5.9, 3.2, and 2.0 per 1000 children during 1989, 1990, and 1991 respectively. The proportion of cases aged up to 36 months fell from 48% in 1989 to 12.5% in 1990 and 6% in 1991. The age at onset was less than 1 year in most. The median age at onset was 10.7 months. About 54% of the affected children had received three doses of oral poliomyelitis vaccine (OPV) before the onset of paralysis. In 1988 immunisation coverage for the third dose of OPV was 91% and in 1992 it was 97.6%. The drop out rate for the first versus the third dose of OPV fell from 6.3 in 1988 to 1.9% in 1992. CONCLUSION: Three successive annual lameness surveys showed that poliomyelitis was declining between 1989 and 1991. Five immunisation coverage surveys conducted from 1988 to 1992 showed high initial coverage followed by an improvement in the form of almost universal coverage for OPV.  相似文献   
6.
We present two cases of neonatal pleural effusion, a relatively rare condition, most commonly due to chylothorax. One had bilateral hypoplastic lungs and the other suffered birth asphyxia. Both died before any treatment could be initiated.  相似文献   
7.
Asymptomatic infection with Loa loa, an eye worm, is reported in a 32-year old Zambian woman. The patient revealed up to 28% eosinophilia but microfileraemia was not noticed. One gravid female parasite 56 X 0.56 mm, extracted from lower lid of left eye of the patient, is described. Treatment with diethylcarbamazine (DEC) extended over three weeks was successful against another parasite in tissues.  相似文献   
8.
The expression of alpha melanocyte stimulating hormone (MSH) has been investigated in two variants of the B16 murine melanoma. The presence of MSH was demonstrated by immunohistochemical methods using anti-MSH antibodies. The low metastasis variant B16-F1, which grows as an encapsulated non-invasive tumour, showed no alpha-MSH immunoreactivity. In contrast, the high metastasis variant BL6 was found to be alpha-MSH positive and the immunoreactivity was found predominantly in the peripheral invading zones of the tumour.  相似文献   
9.
10.
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