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   387篇
  免费   1篇
化学工业   8篇
机械仪表   3篇
建筑科学   2篇
能源动力   6篇
轻工业   4篇
水利工程   1篇
无线电   10篇
一般工业技术   15篇
冶金工业   326篇
自动化技术   13篇
  2022年   4篇
  2021年   2篇
  2020年   1篇
  2016年   2篇
  2015年   3篇
  2014年   2篇
  2013年   5篇
  2012年   1篇
  2011年   4篇
  2008年   3篇
  2007年   2篇
  2006年   3篇
  2005年   1篇
  2004年   2篇
  2003年   3篇
  2002年   1篇
  2001年   1篇
  1999年   8篇
  1998年   115篇
  1997年   61篇
  1996年   34篇
  1995年   30篇
  1994年   15篇
  1993年   13篇
  1992年   5篇
  1991年   5篇
  1990年   2篇
  1989年   1篇
  1988年   1篇
  1986年   1篇
  1985年   2篇
  1983年   1篇
  1982年   2篇
  1981年   5篇
  1980年   4篇
  1978年   3篇
  1977年   14篇
  1976年   22篇
  1975年   2篇
  1971年   1篇
  1954年   1篇
排序方式: 共有388条查询结果,搜索用时 31 毫秒
91.
The placental pathology in two second trimester fetal losses associated with mild maternal disseminated intravascular coagulation are reported. Case one had a dental abscess, a leukocytosis of 36300 white blood cells/m, and evidence of mild consumptive coagulopathy at 20 weeks. Case two had septic findings including disseminated intravascular thrombosis associated with pyelonephritis. The placentae had extensive intervillous thrombosis at the periphery of spiral arterial flow. It is hypothesized that in mild disseminated intravascular coagulation, the trophoblast inhibits fibrinolysis, favouring thrombosis perhaps due to production of plasminogen activator inhibitor.  相似文献   
92.
Thirteen strains of a new acetogenic bacterium were isolated from the rumen contents of lambs, llamas and bisons. This paper is the first report of Gram-positive coccoid spore-forming bacteria occurring in chains and able to use H2 + CO2 as energy source and produce acetate from this gas mixture. One of them, chosen as the reference strain for its efficiency in utilizing H2/CO2 likely via the acetyl-CoA pathway, was characterized in detail. The G + C ratio of the DNA of the organism was 46.5 mol%. The temperature and pH optimum were 37 degrees-40 degrees C and 6.3-6.8, respectively. Numerous organic substrates including some o-methylate aromatic compounds were used heterotrophically. The full 16S rRNA gene sequence was determined. The phylogeny, physiology, morphology and numerous features described here are sufficiently different from those of any bacteria described today to justify the definition of a new species. The name "New acetogenic bacterium" is temporarily proposed, awaiting a future taxonomic revision of the genus Clostridium.  相似文献   
93.
Renal transplantation represents the most favorable treatment for patients with advanced renal failure and it is followed, in most cases, by a significant enhancement in patients’ quality of life. Significant improvements in one-year renal allograft and patients’ survival rates have been achieved over the last 10 years primarily as a result of newer immunosuppressive regimens. Despite these notable achievements in the short-term outcome, long-term graft function and survival rates remain less than optimal. Death with a functioning graft and chronic allograft dysfunction result in an annual rate of 3%–5%. In this context, drug toxicity and long-term chronic adverse effects of immunosuppressive medications have a pivotal role. Unfortunately, at the moment, except for the evaluation of trough drug levels, no clinically useful tools are available to correctly manage immunosuppressive therapy. The proper use of these drugs could potentiate therapeutic effects minimizing adverse drug reactions. For this purpose, in the future, “omics” techniques could represent powerful tools that may be employed in clinical practice to routinely aid the personalization of drug treatment according to each patient’s genetic makeup. However, it is unquestionable that additional studies and technological advances are needed to standardize and simplify these methodologies.  相似文献   
94.
Conductive electroactive polymer polyaniline is utilized to substitute conductive additive acetylene black in the LiMn1·95Al0·05O4 cathode for lithium ion batteries. Results show that LiMn1·95Al0·05O4 possesses stable structure and good performance. Percolation theory is used to optimize the content of conductive additive in cathode. It shows that the conductivity of cathode reaches its maximum value when the content of conductive additives is 15 wt%. This is in agreement with the results of charge and discharge experiments. The application of polyaniline can evidently enhance the electrochemical performance of cathode. The discharge capacity of cathode using 15 wt% polyaniline is 95·9 mAh g???1 at the current density of 170 mA g???1. The charge transfer resistance under different depths of discharge of cathode is much lower compared with the use of acetylene black. It can be concluded that the application of polyaniline in cathode can greatly improve the electrochemical performances of LiMn1·95Al0·05O4 cathode.  相似文献   
95.
The aim of this paper is to investigate the effect of sintering temperature and time on the properties of Fe–Al2O3 composite (5 wt% Al2O3; 95 wt% Fe) prepared by powder metallurgy process. X-ray diffraction, microstructure, density, hardness and compressive strength of prepared samples have been investigated. XRD studies show the presence of Fe and Al2O3 along with iron aluminate phase. Iron aluminate is formed as a result of reactive sintering between iron and alumina particles. Microstructural examination of the specimen showed a dense structure with nanosize dispersion of the reinforcement of ceramic phase. Density as well as hardness of specimens depend on the formation of iron aluminate phase, which in turn depends on sintering temperature and time.  相似文献   
96.
Marras WS  Davis KG  Kirking BC  Granata KP 《Ergonomics》1999,42(10):1258-1273
Two-person or team lifting is a popular method for handling materials under awkward or heavy lifting conditions. While many guidelines and standards address safe lifting limits for individual lifting, there are no such limits for team lifting, and these lifts are poorly understood. The literature associated with team lifting offers some interesting paradoxes. Many studies have indicated that people lift less per individual under team conditions compared with one-person lifting. Yet, at least one study has reported an increase in team-lifting capacity when subjects were height-matched. The current study explored the spine loading characteristics of one- and two-person lifting teams when subjects lifted under several sagittally symmetric and asymmetric conditions. Spine compression was lower for two person lifts for a given weight, while lifting in sagittally symmetric conditions whereas lateral shear became much greater for two-person lifts under asymmetric lifting conditions. This study has linked these changes to differences in trunk kinematic patterns adopted during one- versus two-person lifting.  相似文献   
97.
Guava cv.'Allahabad Safeda'was crushed and treated with pectic enzymes at 0.1% concentration (w/v), incubated for 1 h at 40–50C and the liquefied juice having 10.8 Brix and 0. 65% acidity was used for carbonation. The juice was converted into sugar syrup base having 40% guava juice at 40 Brix and 1% acidity. After dosing 50 ml of it into a glass bottle (200ml capacity) filled with chilled (4-6C) carbonated water at 80 psi pressure of CO2 gas, the bottle was sealed with crown cork and heat processed at 60C for 30 min. The carbonated guava beverage could be stored for 3 months at room (23-41C) and low (3-5C) temperatures and was found acceptable with respect to color, flavor and overall quality. Heat processing improved the flavor of the carbonated guava beverage, and the beverage contained no detectible microbes.  相似文献   
98.
Pediatric allograft recipients in particular are at increased risk for Epstein-Barr virus (EBV)-associated disorders. Early identification and diagnosis of EBV-associated disorders is critical, since disease progression can often be halted by reduction of immunosuppression. In this study we examined viral and immunologic parameters of EBV infection in the circulation of pediatric liver recipients to identify factors associated with disease. Peripheral blood DNA from pediatric liver recipients was analyzed by PCR for the EBV genes coding for the nuclear antigen 1 (EBNA-1) and the viral capsid antigen gp220. Sequences for these viral genes could be readily detected in the circulation of 36.5% of patients. Moreover, identification of the EBV genome was associated with symptomatic infection, suggesting that circulating EBV may be a useful marker of disease. Since EBV-infected B cells release the low-affinity IgE receptor (sCD23), we measured sCD23 in the circulation of pediatric liver recipients and found it to be elevated in patients with detectable virus or symptoms of infection. However, sCD23 was also elevated in cases where no EBV was detectable, suggesting that factors other than viral infection could stimulate release of sCD23. To further characterize the immune response to EBV infection, the peripheral levels of IL-4, IL-5, IL-10, and IFN-gamma were determined in pediatric liver recipients. Each of these cytokines was elevated in patients with symptoms or circulating virus compared with stable, age-matched liver recipients. IL-4, in particular, was significantly increased, indicating an important role for this cytokine in EBV infection. Together, these findings suggest that (1) monitoring circulating levels of EBV may be useful in patients at high risk and (2) cytokines that promote B cell growth and differentiation contribute to EBV-associated disorders.  相似文献   
99.
100.
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