全文获取类型
收费全文 | 2730篇 |
免费 | 17篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 19篇 |
化学工业 | 120篇 |
金属工艺 | 11篇 |
机械仪表 | 17篇 |
建筑科学 | 12篇 |
能源动力 | 31篇 |
轻工业 | 53篇 |
石油天然气 | 4篇 |
无线电 | 87篇 |
一般工业技术 | 114篇 |
冶金工业 | 2198篇 |
原子能技术 | 14篇 |
自动化技术 | 70篇 |
出版年
2023年 | 12篇 |
2022年 | 21篇 |
2021年 | 13篇 |
2020年 | 12篇 |
2019年 | 15篇 |
2018年 | 19篇 |
2017年 | 15篇 |
2016年 | 32篇 |
2015年 | 17篇 |
2014年 | 23篇 |
2013年 | 52篇 |
2012年 | 15篇 |
2011年 | 38篇 |
2010年 | 19篇 |
2009年 | 26篇 |
2008年 | 24篇 |
2007年 | 19篇 |
2006年 | 14篇 |
2005年 | 12篇 |
2004年 | 17篇 |
2003年 | 11篇 |
2002年 | 6篇 |
2001年 | 8篇 |
2000年 | 4篇 |
1999年 | 83篇 |
1998年 | 647篇 |
1997年 | 386篇 |
1996年 | 275篇 |
1995年 | 161篇 |
1994年 | 126篇 |
1993年 | 129篇 |
1992年 | 25篇 |
1991年 | 36篇 |
1990年 | 27篇 |
1989年 | 40篇 |
1988年 | 46篇 |
1987年 | 39篇 |
1986年 | 29篇 |
1985年 | 41篇 |
1984年 | 6篇 |
1983年 | 8篇 |
1982年 | 11篇 |
1981年 | 16篇 |
1980年 | 16篇 |
1978年 | 5篇 |
1977年 | 43篇 |
1976年 | 91篇 |
1975年 | 5篇 |
1973年 | 2篇 |
1971年 | 2篇 |
排序方式: 共有2750条查询结果,搜索用时 31 毫秒
41.
42.
The temperature dependence of the viscosity of the undercooled melts exhibits an important role in the study of nucleation,
crystal growth and the glass-forming ability of materials. Several attempts have been made to study the viscous behaviour
of the glass-forming melts and these investigations are mainly based on free volume theory as well as on the configurational
entropy model. In the present investigation, an attempt has been made to correlate the thermodynamic parameters with the viscosity
of the glass-forming melts and to study the temperature dependence of the viscosity of undercooled liquids on the basis of
the free volume theory as well as on the basis of the configurational entropy model of Adam and Gibbs. The entire study is
confined on the expression for thermodynamic parameters reported by the authors recently. The expression obtained has been
successfully applied to study the temperature dependence of the viscosity of the metallic, molecular and oxide glass-forming
liquids. 相似文献
43.
44.
HM Chaung CH Hong CP Chiang SK Lin YS Kuo WH Lan CC Hsieh 《Canadian Metallurgical Quarterly》1996,95(7):545-550
This review reports the different genetic factors that have been identified either as risk factor for Alzheimer's disease (AD) or directly causing the disease. First are reviewed epidemiological data and biological mechanisms about the apoplipoprotein E gene allele epsilon 4 that is a major risk factor for Alzheimer's disease. The second part describes the mutations responsible for early-onset autosomal dominant AD found in three different genes. The gene located on chromosome 21 encodes the amyloid precusor protein (APP). The presenilin 1 and presenilin 2 genes, located on chromosome 14 and 1 respectively, encode not yet known membrane proteins. 相似文献
45.
46.
47.
48.
MR Sowers M Jannausch C Wood SK Pope LL Lachance B Peterson 《Canadian Metallurgical Quarterly》1998,147(10):914-920
Little is known about the epidemiology of renal stones, in spite of the relative frequency of this painful condition. This population-based study examined reported renal stone diagnosis in 1,309 women aged 20-92 years to determine whether renal stones are associated with 1) food or water exposures or 2) lower bone mineral density and an increased likelihood of fractures. Results indicated a renal stone prevalence of 3.4%. The average age at diagnosis was 42 years. Renal stone formation was not associated with community of residence, hypertension, bone mineral density, fractures, high-oxalate food consumption, or ascorbic acid from food supplements. Women with renal stones consumed almost 250 mg/day less dietary calcium (p < 0.01) than did women without stones and had a lower energy intake (p < 0.04). The authors' findings do not support the hypothesis that increased dietary calcium is associated with a greater prevalence of renal stones, nor do they identify renal stones as a risk factor for low bone mineral density. Furthermore, lack of other identifiable environmental correlates and the relatively young age at initial diagnosis suggest that genetic components of renal stone formation need further study. 相似文献
49.
50.
OBJECTIVE: The aim was to investigate the effects of the potassium-channel opener pinacidil on single uterine potassium channels and the contribution of the latter to pinacidil-induced myometrial relaxation. STUDY DESIGN: Myometrial strips and freshly dispersed uterine myocytes were prepared from the myometrial biopsy samples of women undergoing elective, nonlabor caesarean section at term gestation. RESULTS: In isometric tension experiments pinacidil potently relaxed pregnant nonlabor human myometrial strips, with an agonist concentration yielding the half maximal response of 0.4 +/- 0.1 micromol/L. This effect was antagonized by 500 nmol/L charybdotoxin. Application of 10 micromol/L glibenclamide also inhibited the pinacidil-induced relaxation. Coapplication of charybdotoxin (500 nmol/L) and glibenclamide (10 micromol/L) produced a biphasic curve, which was fitted to a two-site model with values for agonist concentration yielding the half maximal response of 0.6 +/- 0.2 micromol/L and 189.7 +/- 0.8 micromol/L. Large-conductance calcium-dependent potassium channel activity was dramatically increased after application of pinacidil (between 10 and 100 micromol/L) to both inside-out and outside-out patches. The activation required the presence of calcium ions at the intracellular aspect of the membrane. Charybdotoxin but not glibenclamide blocked pinacidil-induced unitary large-conductance calcium-dependent potassium channel activity. CONCLUSION: Pinacidil-mediated relaxation of human pregnant myometrial strips may be partially attributable to the opening of uterine large-conductance calcium-dependent potassium channels in addition to adenosine triphosphate potassium channel activation. Drugs with specific potassium channel-activating properties may have important clinical application as novel tocolytics in the treatment of preterm labor. 相似文献