全文获取类型
收费全文 | 3003篇 |
免费 | 147篇 |
国内免费 | 9篇 |
专业分类
电工技术 | 57篇 |
综合类 | 2篇 |
化学工业 | 424篇 |
金属工艺 | 60篇 |
机械仪表 | 53篇 |
建筑科学 | 127篇 |
矿业工程 | 6篇 |
能源动力 | 81篇 |
轻工业 | 192篇 |
水利工程 | 23篇 |
石油天然气 | 6篇 |
无线电 | 258篇 |
一般工业技术 | 647篇 |
冶金工业 | 754篇 |
原子能技术 | 34篇 |
自动化技术 | 435篇 |
出版年
2023年 | 13篇 |
2022年 | 11篇 |
2021年 | 51篇 |
2020年 | 29篇 |
2019年 | 53篇 |
2018年 | 56篇 |
2017年 | 50篇 |
2016年 | 63篇 |
2015年 | 70篇 |
2014年 | 100篇 |
2013年 | 149篇 |
2012年 | 126篇 |
2011年 | 186篇 |
2010年 | 127篇 |
2009年 | 130篇 |
2008年 | 154篇 |
2007年 | 157篇 |
2006年 | 132篇 |
2005年 | 116篇 |
2004年 | 93篇 |
2003年 | 80篇 |
2002年 | 86篇 |
2001年 | 57篇 |
2000年 | 34篇 |
1999年 | 46篇 |
1998年 | 159篇 |
1997年 | 103篇 |
1996年 | 55篇 |
1995年 | 53篇 |
1994年 | 48篇 |
1993年 | 52篇 |
1992年 | 37篇 |
1991年 | 19篇 |
1990年 | 32篇 |
1989年 | 27篇 |
1988年 | 32篇 |
1987年 | 22篇 |
1986年 | 17篇 |
1985年 | 27篇 |
1984年 | 23篇 |
1983年 | 27篇 |
1982年 | 18篇 |
1981年 | 12篇 |
1980年 | 13篇 |
1977年 | 19篇 |
1976年 | 39篇 |
1975年 | 10篇 |
1974年 | 19篇 |
1973年 | 19篇 |
1972年 | 9篇 |
排序方式: 共有3159条查询结果,搜索用时 18 毫秒
1.
Stefan Wolf Jeremy W. Deuel Maija Hollmn Gunther Felmerer Bong-Sung Kim Mauro Vasella Lisanne Grünherz Pietro Giovanoli Nicole Lindenblatt Epameinondas Gousopoulos 《International journal of molecular sciences》2021,22(7)
Lipedema is an adipose tissue disorder characterized by the disproportionate increase of subcutaneous fat tissue in the lower and/or upper extremities. The underlying pathomechanism remains unclear and no molecular biomarkers to distinguish the disease exist, leading to a large number of undiagnosed and misdiagnosed patients. To unravel the distinct molecular characteristic of lipedema we performed lipidomic analysis of the adipose tissue and serum of lipedema versus anatomically- and body mass index (BMI)-matched control patients. Both tissue groups showed no significant changes regarding lipid composition. As hyperplastic adipose tissue represents low-grade inflammation, the potential systemic effects on circulating cytokines were evaluated in lipedema and control patients using the Multiplex immunoassay system. Interestingly, increased systemic levels of interleukin 11 (p = 0.03), interleukin 28A (p = 0.04) and interleukin 29 (p = 0.04) were observed. As cytokines can influence metabolic activity, the metabolic phenotype of the stromal vascular fraction was examined, revealing significantly increased mitochondrial respiration in lipedema. In conclusion, despite sharing a comparable lipid profile with healthy adipose tissue, lipedema is characterized by a distinct systemic cytokine profile and metabolic activity of the stromal vascular fraction. 相似文献
2.
Qiang Peng Christine Yim-Ping Wong Isabella Wai-yin Cheuk Jeremy Yuen-Chun Teoh Peter Ka-Fung Chiu Chi-Fai Ng 《International journal of molecular sciences》2021,22(9)
Spermine, a member of polyamines, exists in all organisms and is essential for normal cell growth and function. It is highly expressed in the prostate compared with other organs and is detectable in urine, tissue, expressed prostatic secretions, and erythrocyte. A significant reduction of spermine level was observed in prostate cancer (PCa) tissue compared with benign prostate tissue, and the level of urinary spermine was also significantly lower in men with PCa. Decreased spermine level may be used as an indicator of malignant phenotype transformation from normal to malignant tissue in prostate. Studies targeting polyamines and key rate-limiting enzymes associated with spermine metabolism as a tool for PCa therapy and chemoprevention have been conducted with various polyamine biosynthesis inhibitors and polyamine analogues. The mechanism between spermine and PCa development are possibly related to the regulation of polyamine metabolism, cancer-driving pathways, oxidative stress, anticancer immunosurveillance, and apoptosis regulation. Although the specific mechanism of spermine in PCa development is still unclear, ongoing research in spermine metabolism and its association with PCa pathophysiology opens up new opportunities in the diagnostic and therapeutic roles of spermine in PCa management. 相似文献
3.
Toby J. Holda Lars G. Rudstam Kelly L. Bowen Brian C. Weidel James M. Watkins Patrick J. Sullivan Jeremy P. Holden Michael J. Connerton 《Journal of Great Lakes research》2019,45(2):307-316
Mysis diluviana is a major component of prey fish diets in the Great Lakes, so annual production of M. diluviana is important for understanding and modeling energy flow through Great Lakes food webs. However, only three lake-wide measurements of M. diluviana annual production in Lake Ontario are currently available (1971, 1990, 1995). During 2013, lake-wide coverage of Lake Ontario was achieved during four periods from April to November. Annual mean density and biomass of M. diluviana in 2013 were 99?#/m2 (SE: 8) and 318?mg?dw/m2 (SE: 28) – approximately half of values observed in 1990s. M. diluviana comprised 13–30% of offshore zooplankton biomass in each period. Reproduction peaked in fall, with mean brood size of 32 embryos (range: 11–49), at least 10% larger than in 1990s. Generation time was two years from embryo to initial reproduction. Growth rates were 0.052?mm/d for the age-0 cohort and 0.027?mm/d for the age-1 cohort. Age-0 growth rate was significantly higher than in 1980s–90s (0.035?mm/d). Annual production in 2013 was 0.85?g?dw/m2/yr (SE: 0.03) which was 30–40% of values observed in 1990 and 1995 (2.23 and 2.53?g/m2/yr). Annual production to biomass ratio (P/B) in 2013 was 2.65?/yr which was 80–85% of values observed in 1990 and 1995 (3.24 and 3.11?/yr), but this difference was not statistically significant. Our results suggest that changes in annual production over time can be estimated using changes in biomass over time and a mean P/B ratio. 相似文献
4.
ICT projects are considered an important means of achieving development goals in developing countries. Although voluminous, the research to date is inconsistent in theorizing how, or why, development outcomes do or do not occur following the introduction of ICT4D. To better understand how and why ICT projects succeed, and even what success means in the ICT4D context, we conducted a literature review of ICT4D studies published during the period 2000–2016. We find that the very meaning of development varies, with four meanings of development emerging from the literature: (1) development as increased freedom, (2) development as expanded inclusion, (3) development as increased economic productivity, and (4) development as improved well-being. An ICT might succeed according to one meaning of development while simultaneously hindering achievement according to another meaning. As revealed by our analysis of the literature, these four perspectives suffer from some limitations, not least among them being the imposition of colonialist views of development on the recipients of the ICT4D. To address the limitations, we employ postcolonial theory to derive a new theory of ICT4D in which development is defined as an increase in power parity between dominant stakeholders and intended beneficiaries. 相似文献
5.
Wenbin Li Amir Ghazanfari Devin McMillen Ming C. Leu Gregory E. Hilmas Jeremy Watts 《Ceramics International》2018,44(11):12245-12252
The Ceramic On-Demand Extrusion (CODE) process is a novel additive manufacturing method for fabricating dense (~99% of theoretical density) ceramic components from aqueous, high solids loading pastes (>50?vol%). In this study, 3?mol% Y2O3 stabilized zirconia (3YSZ) specimens were fabricated using the CODE process. The specimens were then dried in a humidity-controlled environmental chamber and afterwards sintered under atmospheric conditions. Mechanical properties of the sintered specimens were examined using ASTM standard test techniques, including density, Young’s modulus, flexural strength, Weibull modulus, fracture toughness, and Vickers hardness. The microstructure was analyzed and grain size measured using scanning electron microscopy. The results were compared with those from Direct Inkjet Printing, Selective Laser Sintering, Lithography-based Ceramic Manufacturing (LCM), and other extrusion-based processes, and indicated that zirconia specimens produced by CODE exhibit superior mechanical properties among the additive manufacturing processes. Several sample components were produced to demonstrate CODE’s capability for fabricating geometrically complex ceramic components. The surface roughness of these components was also examined. 相似文献
6.
7.
8.
Changmo Kim Izhar Livne‐Bar Karsten Gronert Jeremy M. Sivak 《Molecular nutrition & food research》2020,64(4)
Lipoxins (LXs) are autacoids, specialized proresolving lipid mediators (SPMs) acting locally in a paracrine or autocrine fashion. They belong to a complex superfamily of dietary small polyunsaturated fatty acid (PUFA)–metabolites, which direct potent cellular responses to resolve inflammation and restore tissue homeostasis. Together, these SPM activities have been intensely studied in systemic inflammation and acute injury or infection, but less is known about LX signaling and activities in the central nervous system. LXs are derived from arachidonic acid, an omega‐6 PUFA. In addition to well‐established roles in systemic inflammation resolution, they have increasingly become implicated in regulating neuroinflammatory and neurodegenerative processes. In particular, chronic inflammation plays a central role in Alzheimer's disease (AD) etiology, and dysregulated LX production and activities have been reported in a variety of AD rodent models and clinical tissue samples, yet with complex and sometimes conflicting results. In addition, reduced LX production following retinal injury has been reported recently by the authors, and an intriguing direct neuronal activity promoting survival and homeostasis in retinal and cortical neurons is demonstrated. Here, the authors review and clarify this growing literature and suggest new research directions to further elaborate the role of lipoxins in neurodegeneration. 相似文献
9.
10.
Mining blasts may be defined as the use of explosive charges in a controlled manner by following a tightly controlled timing sequence according to an assigned firing order. Changes of timing between charges may result in an altered firing order and failure of the blasting sequence, which can cause high vibration levels, poor fragmentation, and/or an undesirable rock mass movement direction. Despite the importance of timing in determining mine blast results, there exists a lack of methodologies or tools with which to assess performance of a complete blast based on delay type and timing sequence. This document applies reliability engineering principles to evaluate the performance of a mine blast. The analyses are based on test results of the accuracy and precision of electronic and pyrotechnic detonators for typical firing times used in a surface coal mine, but may be applied to a variety of mines and timing scenarios. 相似文献