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   395篇
  免费   5篇
  国内免费   1篇
电工技术   1篇
化学工业   10篇
机械仪表   16篇
建筑科学   8篇
矿业工程   1篇
轻工业   5篇
无线电   24篇
一般工业技术   15篇
冶金工业   314篇
自动化技术   7篇
  2023年   1篇
  2022年   1篇
  2021年   3篇
  2020年   3篇
  2019年   3篇
  2018年   5篇
  2017年   3篇
  2016年   6篇
  2014年   2篇
  2013年   6篇
  2012年   6篇
  2011年   7篇
  2010年   4篇
  2009年   1篇
  2008年   2篇
  2007年   3篇
  2006年   2篇
  2005年   2篇
  2004年   1篇
  2003年   2篇
  2002年   1篇
  2001年   1篇
  2000年   3篇
  1999年   3篇
  1998年   83篇
  1997年   51篇
  1996年   36篇
  1995年   21篇
  1994年   23篇
  1993年   19篇
  1992年   3篇
  1991年   4篇
  1990年   5篇
  1989年   7篇
  1988年   5篇
  1987年   8篇
  1986年   10篇
  1985年   8篇
  1984年   1篇
  1983年   3篇
  1982年   5篇
  1981年   6篇
  1980年   2篇
  1978年   1篇
  1977年   9篇
  1976年   18篇
  1975年   1篇
  1962年   1篇
排序方式: 共有401条查询结果,搜索用时 15 毫秒
1.
We investigated the capacity of the hyperthermophile Pyrococcus furiosus for DNA repair by measuring survival at high levels of 60Co gamma-irradiation. The P. furiosus 2-Mb chromosome was fragmented into pieces ranging from 500 kb to shorter than 30 kb at a dose of 2,500 Gy and was fully restored upon incubation at 95 degrees C. We suggest that recombination repair could be an extremely active repair mechanism in P. furiosus and that it might be an important determinant of survival of hyperthermophiles at high temperatures.  相似文献   
2.
3.
OBJECTIVE: Treatment with metformin is occasionally associated with the development of severe lactic acidosis. However, this is usually observed in patients with major contraindications to the drug. In this study, we aimed to determine the prevalence of conditions currently regarded as either contraindications or cautions to the use of metformin in patients with NIDDM. RESEARCH DESIGN AND METHODS: The case notes of metformin-treated NIDDM patients (mean age 62 years) attending a United Kingdom university hospital diabetes clinic over a 3-month period were reviewed according to criteria reflecting a pragmatic view of current prescribing recommendations. RESULTS: Of 89 consecutive patients whose notes could be evaluated in detail, only 41 (46%) had no contraindications or cautions to metformin whatsoever. Concomitant chronic disorders associated with a potentially increased risk of hyperlactatemia were renal impairment (n = 2; plasma creatinine concentrations 1.7 and 2.3 mg/dl, respectively), cardiac failure (n = 2), and chronic liver disease (n = 2). Other potentially relevant disorders included ischemic heart disease (n = 20), clinical proteinuria (n = 14), peripheral vascular disease (n = 22), and pulmonary disease (n = 7). Multiple conditions (i.e., two, three, or four) were present in eight, five, and one patient(s), respectively. CONCLUSIONS: More than half the patients in our series had concomitant conditions or complications conventionally regarded as cautions or contraindications to metformin; approximately 10% had a multiplicity of such conditions. Regular surveillance is necessary to detect the development of complications such as renal impairment. Vigilance is also required in view of the increased risk of major intercurrent illnesses, which may independently disturb lactate metabolism in patients with NIDDM. Metformin should be withdrawn promptly under such circumstances.  相似文献   
4.
5.
OBJECTIVE: To determine whether infrared skin thermography is an objective measurement reflecting the seriousness of nerve root irritation in lumbar disk herniation patients. DESIGN: Quantified nerve root signs by physical examination were collected from the patients along with the infrared skin temperature measurement on the lumbosacral region and posterior part of thighs. A correlation study was applied to observe the relation between the nerve root signs and the skin temperature before a successful conservative treatment (mainly spine manipulation), and between the alteration of nerve root signs and that of skin temperature after the treatment. SETTING: Hospitalized care. PATIENTS: Twenty-seven hospitalized samples with computed tomography or magnetic resonance approval were consecutively selected during the latter half of 1990. MAIN OUTCOME MEASURE: Changes in nerve root signs. RESULTS: The temperature difference between a troubled thigh and healthy one is significantly correlated to the score of the nerve root signs before the treatment; and the reduction of temperature difference between two thighs is also significantly correlated with decreasing score of nerve root signs after the treatment. The correlation between the temperature difference on the left and right sides of the lumbosacral region and the nerve root signs before the treatment is insignificant; and the variation of the temperature difference of the same region after the treatment is not correlated with the decreasing score of the nerve root signs. CONCLUSION: Infrared skin thermography of lower extremities might be an objective sign in signaling the soothing process of the nerve root irritation in lumbar disk herniation patients, which may help a doctor in checking the responses of the patient to treatment.  相似文献   
6.
The hydrolytic cleavage of a cyanine (Cy3)-labeled angiotensin, catalyzed by various proteases, was studied by capillary electrophoresis (CE) with laser-induced fluorescence detection (LIF). The end-labeled peptides and the Cy3 diacid internal standard were separated on a 20-microns x 27-cm capillary with LIF detection (emission, 580 nm) using a frequency-doubled solid-state diode laser emitting at 532 nm or a He-Ne laser emitting at 543 nm. Hydrolysis of the Cy3-labeled angiotensin I, catalyzed by proteinase K, is a sequential process beginning from the C-terminal of the peptide, instead of from random cleavages. Trypsin catalyzes a specific cleavage of Cy3-angiotensin I to Cy3-Asp-Arg as anticipated. Using a combination of endopeptidase and carboxypeptidases, the remnant of the labeled species was characterized by CE-LIF. The method provides a general tool for studying the mechanism of protease-catalyzed hydrolysis of peptide.  相似文献   
7.
8.
To examine the mechanisms of CD4 reconstitution in an adult population, lymphocyte repopulation was assessed following dose-intense chemotherapy in 25 breast cancer patients, ages 33 to 69 years. Chemotherapy resulted in a greater than 60% reduction in total CD4 T cells and, in particular, a greater than 90% loss of the CD45RA+ CD4 cells. CD4 recovery was protracted, achieving less than 50% of pretreatment levels after 12 to 14 months. Two facets of the CD4 recovery were notable. First, generation of CD45RA+ CD4 cells played only a minor role in the first year, suggesting that thymic production was not the main route of CD4 regeneration. Indeed, recovery of CD45RA+ CD4 cell levels remained limited in half of the patients even after 2 years. Second, expansion of the mature peripheral CD4 cells (CD45RO+) remaining after chemotherapy was the main source of early CD4 repopulation, peaking at 3 to 6 months postchemotherapy. This expansion was limited in duration, however, and was followed by a secondary decline, such that the total CD45RO+ CD4 levels at 9 to 12 months were lower than at 6 months. When stimulated by mitogens, an increased susceptibility to apoptosis was observed in postchemotherapy CD4 cells as compared with those from normal donors. The elevated expression of markers such as HLA-DR during chemotherapy and for several months postchemotherapy is consistent with the presence of an activated T-cell population. CD4 apoptotic frequency correlated with the frequency of HLA-DR expression on T cells. Thus, CD4 recovery is constrained in adults by a limited thymic regenerative capacity and by an increased susceptibility to apoptosis within the expanding peripheral CD4 population.  相似文献   
9.
Percutaneous balloon pericardiotomy is effective and less invasive for the treatment of recurrent pericardial effusion. This study suggests that the double-balloon method with 1 longer and 1 shorter balloon is the procedure of choice for percutaneous balloon pericardiotomy.  相似文献   
10.
This research maps some of the debates on community building in the planning of suburban developments. Particular reference is made to Kokoku New Town in Yokohama, Japan, and the Golden Grove Development in Adelaide, Australia. These two developments emerged in the early 1980s and the histories related suggest significant similarities, although they grew out of different regimes of power. Drawing upon Foucault and other governmentality thinkers, this study focuses on the relationships between neoliberalism and suburbanization. The primary concern is the exercise of government (the conduct of conduct) and how this exercise is carried out and maintained.  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