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   8451篇
  免费   1篇
  国内免费   1篇
电工技术   1篇
综合类   5篇
化学工业   33篇
金属工艺   5篇
建筑科学   3篇
轻工业   11篇
水利工程   1篇
石油天然气   3篇
武器工业   1篇
无线电   8篇
一般工业技术   11篇
冶金工业   8357篇
原子能技术   1篇
自动化技术   13篇
  2020年   3篇
  2016年   1篇
  2014年   4篇
  2013年   3篇
  2012年   3篇
  2011年   2篇
  2010年   4篇
  2009年   5篇
  2008年   4篇
  2007年   8篇
  2006年   7篇
  2005年   7篇
  2004年   11篇
  2003年   13篇
  2001年   3篇
  2000年   6篇
  1999年   277篇
  1998年   2676篇
  1997年   1480篇
  1996年   947篇
  1995年   547篇
  1994年   419篇
  1993年   526篇
  1992年   61篇
  1991年   102篇
  1990年   99篇
  1989年   87篇
  1988年   93篇
  1987年   91篇
  1986年   95篇
  1985年   65篇
  1984年   1篇
  1983年   9篇
  1982年   35篇
  1981年   37篇
  1980年   77篇
  1979年   2篇
  1978年   12篇
  1977年   181篇
  1976年   431篇
  1975年   9篇
  1963年   2篇
  1955年   7篇
  1954年   1篇
排序方式: 共有8453条查询结果,搜索用时 31 毫秒
71.
72.
73.
74.
Dyslipidaemia may be treated with a number of safe and effective pharmacological agents that target specific lipid disorders through a variety of mechanisms. The bile-acid sequestrants--cholestyramine and colestipol--primarily decrease LDL cholesterol by binding bile acids, thereby decreasing intrahepatic cholesterol, and by increasing the activity of LDL receptors. Nicotinic acid lowers LDL cholesterol and triglyceride by decreasing VLDL synthesis and by decreasing free fatty acid mobilization from peripheral adipocytes. The HMG-CoA reductase inhibitors--fluvastatin, lovastatin, pravastatin and simvastatin--lower LDL cholesterol by partially inhibiting HMG-CoA reductase (the rate-limiting enzyme of cholesterol biosynthesis) and by increasing the activity of LDL receptors. The fibric-acid derivatives--bezafibrate, ciprofibrate, clofibrate, fenofibrate and gemfibrozil--primarily decrease triglyceride by increasing lipoprotein lipase activity and by decreasing the release of free fatty acids from peripheral adipose tissue. Probucol decreases LDL cholesterol by increasing non-receptor-mediated LDL clearance; as an anti-oxidant, probucol also decreases LDL oxidation; oxidized LDL which is thought to lead to atherogenesis. Although these agents have been proven safe in clinical trials, like any drug, they carry the risk for adverse effects. The bile-acid sequestrants may cause constipation, reflux oesophagitis, and dyspepsia, and may bind coadministered medications such as digitalis glycosides, beta blockers, warfarin, and exogenous thyroid hormone. Nicotinic acid use is commonly associated with flushing and pruritus and may also cause non-specific gastrointestinal complaints, hepatotoxicity (hepatic necrosis, hepatitis, or elevated liver enzymes), gout, myolysis, decreased glucose tolerance and increased fasting glucose levels, and ophthalmological complications including decreased visual acuity, toxic amblyopia, and cystic maculopathy. The HMG-CoA reductase inhibitors may produce liver enzyme elevations, creatine kinase elevations and rhabdomyolysis. The combination of a reductase inhibitor and a fibrate increases the risk for rhabdomyolysis. Possible adverse effects of the fibric-acid derivatives include abdominal discomfort, nausea, flatulence, increased lithogenicity of bile, liver enzyme elevations and creatine kinase elevations. Probucol may increase the QTc interval and may cause non-specific gastrointestinal complaints.  相似文献   
75.
76.
77.
Culture of Chlamydia trachomatis from synovial tissues/fluids from Reiter's syndrome (RS) patients frequently yields negative results. However, we have identified chlamydial RNA at that site in such patients, suggesting that viable organisms may be present. Here we define the cellular location of chlamydia within the synovium via in situ hybridization. Using a chlamydial ribosomal RNA-directed probe, we show that synovial tissue from culture-negative RS patients gives strong hybridization which is often localized to a subsynovial cell layer, rather than to the synovial lining; in some cases, hybridizing cells are dispersed through the synovium. All hybridization signal is located within host cells, indicating that infectious extracellular elementary bodies are rare or absent. These data confirm the extensive intracellular presence of inapparent chlamydia in the synovia of RS patients and provide some insight into the usual culture negativity of synovial tissues for the organism.  相似文献   
78.
We have investigated factors influencing the survival of women with early breast cancer in Scotland. In a retrospective study, clinical, treatment and 'service' factors, e.g. surgical case load, deprivation and geographical area (health board of first treatment) were recorded from hospital records. A total of 2148 women with invasive breast cancer diagnosed in 1987 were identified from the Scottish Cancer Registry, of whom 1619 without metastases at diagnosis underwent surgery as part of their primary treatment. In a multivariate analysis, clinical factors (age, clinical stage, pathological tumour size, node status and oestrogen receptor status) all influenced survival. After allowing for these clinical factors, surgical case load and deprivation did not have statistically significant effects on survival. By contrast, health board did affect survival. This was explained in part by the selection of patients for surgery. There appeared, however, to be a residual effect that may be related to differences in the use of adjuvant systemic treatment among the different health boards. We conclude that, in Scotland, geographical variation in both surgical and non-surgical treatment has a greater effect on variability in survival for women with breast cancer than surgical case load and deprivation.  相似文献   
79.
Mantle cell lymphoma (MCL) patients represent a difficult problem, sometimes to establish the diagnosis but mostly because of their refractoriness to standard lymphoma treatments. Which treatments to apply and to whom is not yet defined. In this study, we attempted to analyze the clinical features, to identify the major prognostic factors, and to evaluate the outcome of 121 MCL patients treated in our institution between 1979 and 1997. Clinical data, treatment modalities, and International Prognostic Index (IPI) score were evaluated. Median age was 63 years. Patients usually presented with advanced stage disease (87%), disseminated lymph nodes (57%), bone marrow involvement (79%), but with a good performance status (PS) (81%). Lymphocytosis >4000/microl and/or peripheral blood involvement was present in 36% of cases, and gastrointestinal disease in 18%. The t(11;14)(q13;q32) and/or bcl-1 rearrangement was detected in 47/57 studied cases. Median overall survival (OS) was 3.12 years and a longer survival was significantly associated with younger age (<70 years), good PS (<2), localized disease (stage I-II), fewer than two extra-nodal sites, absence of spleen or peripheral blood involvement, normal serum LDH and beta2-microglobulin levels, and hemoglobin level greater than 12 g/dl. However, the IPI failed to identify patients with longer OS and in a multiparametric analysis, only older age, hemoglobin less than 12 g/dl, poor PS, and blood involvement were associated with a poorer outcome. Treatment modalities had no impact on survival with 75% of patients relapsing or progressing. Our data showed that the poor outcome of MCL patients is mainly related to adverse patient characteristics, a highly disseminated tumor, and some unknown parameters associated with the refractoriness to standard therapy.  相似文献   
80.
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