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   4223篇
  免费   20篇
  国内免费   6篇
电工技术   3篇
综合类   9篇
化学工业   73篇
金属工艺   11篇
机械仪表   17篇
建筑科学   31篇
矿业工程   5篇
能源动力   7篇
轻工业   65篇
水利工程   4篇
石油天然气   5篇
武器工业   1篇
无线电   32篇
一般工业技术   73篇
冶金工业   3852篇
原子能技术   1篇
自动化技术   60篇
  2022年   7篇
  2021年   6篇
  2020年   3篇
  2019年   8篇
  2018年   8篇
  2017年   8篇
  2016年   5篇
  2015年   3篇
  2014年   12篇
  2013年   22篇
  2012年   27篇
  2011年   28篇
  2010年   16篇
  2009年   24篇
  2008年   23篇
  2007年   47篇
  2006年   13篇
  2005年   29篇
  2004年   21篇
  2003年   10篇
  2002年   12篇
  2001年   7篇
  2000年   8篇
  1999年   146篇
  1998年   1263篇
  1997年   684篇
  1996年   460篇
  1995年   262篇
  1994年   219篇
  1993年   246篇
  1992年   30篇
  1991年   42篇
  1990年   49篇
  1989年   48篇
  1988年   39篇
  1987年   31篇
  1986年   30篇
  1985年   32篇
  1983年   5篇
  1982年   28篇
  1981年   23篇
  1980年   27篇
  1978年   4篇
  1977年   66篇
  1976年   152篇
  1975年   2篇
  1973年   3篇
  1964年   3篇
  1955年   2篇
  1954年   1篇
排序方式: 共有4249条查询结果,搜索用时 15 毫秒
41.
BACKGROUND: Our objective was to determine the possible presence of IgA antibodies directed against human central nervous system (CNS) structures in sera from coeliac disease (CD) patients. METHODS: Serum samples were collected from 4 patients with active CD on a gluten-containing diet, 11 biopsy-proven CD patients on a gluten-free diet (GFD), and 52 non-coeliac gastrointestinal controls. In all patients IgA antigliadin antibody (AGA) titres were determined with enzyme-linked immunoassay (ELISA), and IgA antiendomysium antibodies (EMA) with indirect immunofluorescence on human umbilical cord. Cryostat sections of human brain occipital cortex were incubated with the patients' sera and subsequently labelled with anti-human IgA fluorescein conjugate. RESULTS: All sera from patients with active CD on a gluten-containing diet yielded positive results in both the IgG-AGA and EMA test and in indirect immunofluorescence on brain tissue, disclosing a strong fluorescence over blood-vessels structures. All sera from CD patients on a GFD and from non-coeliac gastrointestinal controls gave a negative result on both the EMA test and the immunofluorescence reaction on human brain. CONCLUSIONS: Sera from patients with active CD contain IgA antibodies that react with human brain vessel structures, giving intense fluorescence. These antibodies are not present in sera from coeliac patients on a GFD or non-coeliac controls. This finding might be involved in the abnormal nervous system manifestations frequently described in association with coeliac disease.  相似文献   
42.
43.
A melt pelletization process was investigated in an 8 litre laboratory scale high shear mixer using a formulation with paracetamol, glyceryl monostearate 40-50, and microcrystalline wax. The effects of jacket temperature, product temperature during massing, product load, massing time and impeller speed were investigated by means of factorially designed experiments. The maximum yield of pellets in the range of 500-1400μm was found to approx. 90%. For process conditions preventing deposition of moist mass, the process was found to be reproducible. Impeller speed and massing time were found to be important process variables. Remarkably low in vitro drug release rates were observed in USP-dissolution tests.  相似文献   
44.
45.
Seventeen years after the introduction of x-ray digital subtraction angiography (DSA), gadolinium-enhanced magnetic resonance (MR) angiography techniques have become available for the performance of MR-DSA. For the purposes of this article, we will consider this to include two-dimensional and three-dimensional approaches using time-resolved and non-time-resolved applications. Magnetic resonance-DSA is one in a historical progression of techniques which have aimed to produce less invasive forms of angiography. After outlining some historical milestones, several current issues regarding current methods for MR-DSA are discussed.  相似文献   
46.
47.
48.
We investigated the effect of chronic exposure (3 days) with low-density lipoprotein (LDL) and oxidized (Ox)-LDL on the unstimulated and stimulated formation of prostacyclin (6-keto-prostaglandin [PG]F1 alpha) and total inositol phosphates (IPs) by cultured bovine aortic endothelial cells. Neither basal nor bradykinin-stimulated (1 to 10 nmol/L) formation of 6-keto-PGF1 alpha was affected by LDL, except at the highest concentration of bradykinin tested (100 nmol/L). In the presence of the antioxidants N-acetyl-L-cysteine (NAC, 10 mumol/L) or vitamin E (100 mumol/L), basal and bradykinin-stimulated formation of 6-keto-PGF1 alpha was potentiated by 20 micrograms protein/mL of LDL. Ox-LDL decreased unstimulated formation of the eicosanoid from 3.1 +/- 0.2 pg/micrograms protein in control cells to 1.6 +/- 0.1 and 0.5 +/- 0.1 pg/microgram protein after 3-day incubation with 5 and 20 micrograms protein/mL of Ox-LDL, respectively (P < .05). As in the basal state, Ox-LDL decreased bradykinin-induced 6-keto-PGF1 alpha formation. NAC or vitamin E did not influence Ox-LDL-induced endothelial cell changes in eicosanoid production. IPs formation by endothelial cells increased to a similar extent in the presence of 20 micrograms protein/mL of either LDL or Ox-LDL. However, no change was apparent in the bradykinin (10 mumol/L)-induced increase in total IPs formation after incubation with the lipoproteins. The data indicate that chronic exposure to Ox-LDL abolishes the production of prostacyclin by cultured endothelial cells. The oxidatively modified lipoprotein seems to more specifically affect the prostacyclin pathway.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
49.
Old lipid acting drugs (fibrates, resins and niacin) continue to demonstrate morbidity and mortality benefits with variable efficacy and safety. Controlled trials have provided efficacy and safety data that support the use of statins as the first choice in the treatment and prevention of atherosclerosis. Knowledge of old and new mechanisms of action, optimal doses, pharmacokinetic behavior and drug interactions improve the safety and effectiveness of these hypolipidemic agents.  相似文献   
50.
The changing clinical dynamics of prostate cancer have resulted in a broadening of the research focus of the Genitourinary (GU) Cancer Committee of the Southwest Oncology Group (SWOG). Beginning with an emphasis on hormone-refractory disease in its early years, SWOG prostate cancer trials now cover the entire spectrum of the disease: localized, locally advanced, metastatic and hormone-refractory disease. As the world's largest GU cancer research group, the GU committee of SWOG has pioneered studies in combined androgen therapy for metastatic disease, quality-of-life (QOL) assessments for patients with localized and advanced disease, adjuvant therapy models, and prostate cancer chemoprevention. The committee has also formed the GU Global Group, whose purpose is to convene the chairs of the GU committees of all the major national and international oncology cooperative groups. Meeting semiannually, this group discusses activities within their respective organizations, plans collaborative strategies and protocols, and establishes global strategy in prostate cancer clinical research. The future directions of national and international prostate cancer trials will build on this broad foundation of well-conceived, logically sequenced studies.  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