全文获取类型
收费全文 | 2366篇 |
免费 | 48篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 37篇 |
综合类 | 24篇 |
化学工业 | 479篇 |
金属工艺 | 38篇 |
机械仪表 | 46篇 |
建筑科学 | 77篇 |
矿业工程 | 16篇 |
能源动力 | 39篇 |
轻工业 | 181篇 |
水利工程 | 27篇 |
石油天然气 | 5篇 |
无线电 | 169篇 |
一般工业技术 | 293篇 |
冶金工业 | 612篇 |
原子能技术 | 37篇 |
自动化技术 | 336篇 |
出版年
2021年 | 27篇 |
2020年 | 24篇 |
2019年 | 30篇 |
2017年 | 23篇 |
2016年 | 44篇 |
2015年 | 37篇 |
2014年 | 32篇 |
2013年 | 127篇 |
2012年 | 67篇 |
2011年 | 84篇 |
2010年 | 86篇 |
2009年 | 80篇 |
2008年 | 93篇 |
2007年 | 91篇 |
2006年 | 78篇 |
2005年 | 89篇 |
2004年 | 65篇 |
2003年 | 44篇 |
2002年 | 64篇 |
2001年 | 40篇 |
2000年 | 28篇 |
1999年 | 33篇 |
1998年 | 41篇 |
1997年 | 27篇 |
1996年 | 42篇 |
1995年 | 37篇 |
1994年 | 31篇 |
1993年 | 38篇 |
1992年 | 38篇 |
1991年 | 23篇 |
1990年 | 36篇 |
1989年 | 38篇 |
1988年 | 26篇 |
1987年 | 22篇 |
1986年 | 39篇 |
1985年 | 47篇 |
1984年 | 52篇 |
1983年 | 43篇 |
1982年 | 53篇 |
1981年 | 25篇 |
1980年 | 35篇 |
1979年 | 31篇 |
1978年 | 30篇 |
1977年 | 40篇 |
1976年 | 36篇 |
1975年 | 37篇 |
1974年 | 29篇 |
1973年 | 25篇 |
1972年 | 24篇 |
1969年 | 22篇 |
排序方式: 共有2416条查询结果,搜索用时 15 毫秒
81.
Azizul Haque Arabinda Das Supriti Samantaray Denise Matzelle Mollie Capone Gerald Wallace Aarti N. Husarik Saied Taheri Russel J. Reiter Abhay Varma Swapan K. Ray Naren L. Banik 《International journal of molecular sciences》2022,23(4)
Spinal cord injury (SCI) causes significant mortality and morbidity. Currently, no FDA-approved pharmacotherapy is available for treating SCI. Previously, low doses of estrogen (17β-estradiol, E2) were shown to improve the post-injury outcome in a rat SCI model. However, the range of associated side effects makes advocating its therapeutic use difficult. Therefore, this study aimed at investigating the therapeutic efficacy of Premarin (PRM) in SCI. PRM is an FDA-approved E2 (10%) formulation, which is used for hormone replacement therapy with minimal risk of serious side effects. The effects of PRM on SCI were examined by magnetic resonance imaging, immunofluorescent staining, and western blot analysis in a rat model. SCI animals treated with vehicle alone, PRM, E2 receptor antagonist (ICI), or PRM + ICI were graded in a blinded way for locomotor function by using the Basso–Beattie–Bresnahan (BBB) locomotor scale. PRM treatment for 7 days decreased post-SCI lesion volume and attenuated neuronal cell death, inflammation, and axonal damage. PRM also altered the balance of pro- and anti-apoptotic proteins in favor of cell survival and improved angiogenesis and microvascular growth. Increased expression of estrogen receptors (ERs) ERα and ERβ following PRM treatment and their inhibition by ER inhibitor indicated that the neuroprotection associated with PRM treatment might be E2-receptor mediated. The attenuation of glial activation with decreased inflammation and cell death, and increased angiogenesis by PRM led to improved functional outcome as determined by the BBB locomotor scale. These results suggest that PRM treatment has significant therapeutic implications for the improvement of post-SCI outcome. 相似文献
82.
Ladle shrouds(LS)and submerged entry nozzles(SEN)are flow control products used in continuous casting which transfer the liquid steel from the ladle to the tund... 相似文献
83.
Optimization of segmented constrained layer damping with mathematical programming using strain energy analysis and modal data 总被引:2,自引:0,他引:2
A new method for enhancement of damping capabilities of segmented constrained layer damping material is proposed. Constrained layer damping has been extensively used since many years to damp flexural vibrations. The shear deformation occurring in the viscoelastic core is mainly responsible for the dissipation of energy. Cutting both the constraining and the constrained layer, which leads to segmentation, increases the shear deformation at that position. This phenomenon is called edge effect. A two-dimensional model of a cantilever beam has been realized for further investigations. An optimization algorithm using mathematical programming is developed in order to identify a cuts arrangement that optimizes the loss factor. The damping efficiency is estimated using the modal strain energy method. The Nelder–Mead simplex method is used to find the best distribution of cuts. In order to take into account geometrical limitations, the exterior point penalty method is used to transform the constrained objective function into an unconstrained objective function. As the optimization problem is not convex, a modal analysis is performed at each mode in order to identify initial cuts positions that lead to a global minimum. Over a large frequency range, the algorithm is able to identify a distribution of cuts that optimizes the loss factor of each mode under consideration. 相似文献
84.
Gerald J. Hahn 《技术计量学》2013,55(4):337-339
We describe a diagnostic method for assessing the degree to which individual cases and groups of cases influence the Box-Cox likelihood estimate of the transformation parameter for the response variable in linear regression models. We compare the method to a method proposed by Atkinson (1982) and sketch the extension to explanatory variables. We present two examples. 相似文献
85.
Rémi Bertrand Jean-François Henne Gerald Camus Francis Rebillat 《Oxidation of Metals》2017,88(3-4):237-246
Composites made of ceramic for both fibers and matrix are aimed at being used in aerospace applications, which means being submitted to mechanical stresses at high temperatures in oxidizing and corrosive environments for long durations. The oxidation/corrosion resistance of these materials is linked to their ability to self-heal by creating an oxide phase which can restrict the access of the oxygen into the bulk of the material. During thermomechanical cycles, the distribution of O2 inside the material as well as the distribution and the state of the liquid oxides will undergo some modifications. A specific test has been conceived and performed in order to evidence the influence of the viscosity of this oxide on the mechanical properties of the material. Results have shown that the stiffening which is observed seems to be proportional to the increase in the viscosity of the sealing oxide, in conjunction with the decrease in the temperature. 相似文献
86.
Gerald R. Fast 《Canadian Journal of Science, Mathematics, & Technology Education》2013,13(2-3):149-181
Abstract Analogies were used to facilitate reconstructing the probability knowledge of 54 culturally diverse, female, Zimbabwean secondary school students in cases where there were misconceptions in their comprehension of probability. Ten contextually appropriate misconception‐prone target situations were generated, together with their conceptually analogous counterparts, known as source or anchoring situations. The source analogues were designed to draw out those areas where student beliefs agreed with accepted mathematical theory. Students’ responses to the target situations indicated that probability misconceptions were common and that the source analogues were effective in providing anchors for mathematically correct ideas. The participants were interviewed and knowledge reconstruction was attempted using the source analogues. A success rate of 0.88 was achieved. Testing after one month indicated a stability rate of 0.82 for the reconstructed probability knowledge. 相似文献
87.
88.
Asiri K. A. R. Wijenayaka Christopher B. Colby Gerald J. Atkins Peter Majewski 《Journal of materials science. Materials in medicine》2009,20(7):1467-1473
The osteoclast (OC) is the cell type responsible for the resorption of bone. The activity of this cell is important in the
aetiology of a large number of skeletal pathologies, and also for the biocompatibility and osseointegration of orthopaedic
implant materials. OC mediated acid hydrolysis of calcium phosphate from the bone matrix offers a prime means of studying
the biology and activity of this cell type. We have developed a method of coating glass coverslips with a hydroxyapatite (HA)-like
mineral, using a biomimetic approach. Hydroxylation followed by formation of a self assembled monolayer (SAM) using the surfactant
triethoxysilylpropyl succinic anhydride (TESPSA), allowed biomimetic deposition of HA-like mineral from a simulated body fluid
(SBF). The biocompatibility of the TESPSA SAM-HA coated glass coverslips was tested by culturing human mature OC present in
samples of giant cell tumour of bone (GCT). Parameters of OC activity were assayed, including F-actin ring formation, release
of calcium and formation of osteoclastic resorption pits, confirming that OC were able to attach to and resorb the coated
surface. This approach for the preparation of HA coatings on glass coverslips could have wide applicability for the study
of osteoclast behaviour in vitro.
Gerald J. Atkins and Peter Majewski share senior author status. 相似文献
89.
Eddie Hyatt Russell Griffin Loring W. Rue III Gerald McGwin Jr. 《Accident; analysis and prevention》2009,41(5):1075-1079
Motorcyclists have been reported to be more likely to die in a motor vehicle collision (MVC) than automobile occupants. With the recent increase in the pump price of gasoline, it has been reported that people are switching to motorcycles as main modes of transportation. This study evaluated the association between motor vehicle collision-related injury and mortality rates and increases in gasoline prices for occupants of automobiles and riders of motorcycles.There were an estimated 1,270,512 motorcycle MVC and 238,390,853 automobile MVC involved occupants in the U.S. from 1992 to 2007. Higher gasoline prices were associated with increased motorcycle-related injuries and deaths; however, this association no longer remained after accounting for changes in the number of registered vehicles.The current study observed that, while the number of injuries and fatalities in motorcycle-related MVCs increase with increasing gasoline price, rates remained largely unchanged. This suggests that the observed increase in motorcycle-related injuries and fatalities with increasing gasoline price is more a factor of the number of motorcycles on the road rather than operator characteristics. 相似文献
90.
This paper proposes four decision-making procedures to be employed by electric generating companies as part of their bidding strategies when competing in an ologopolistic market: naïve, forward, adaptive, and moving average expectations. Decision-making is formulated in a dynamic framework by using linear control theory. The results reveal that interactions among all GENCOs affect market dynamics. Several numerical examples are reported, and conclusions are presented. 相似文献