全文获取类型
收费全文 | 2410篇 |
免费 | 57篇 |
专业分类
电工技术 | 8篇 |
化学工业 | 111篇 |
金属工艺 | 9篇 |
机械仪表 | 10篇 |
建筑科学 | 16篇 |
能源动力 | 47篇 |
轻工业 | 45篇 |
水利工程 | 10篇 |
石油天然气 | 3篇 |
无线电 | 75篇 |
一般工业技术 | 132篇 |
冶金工业 | 1891篇 |
原子能技术 | 2篇 |
自动化技术 | 108篇 |
出版年
2023年 | 5篇 |
2022年 | 6篇 |
2021年 | 24篇 |
2020年 | 19篇 |
2019年 | 13篇 |
2018年 | 31篇 |
2017年 | 17篇 |
2016年 | 26篇 |
2015年 | 12篇 |
2014年 | 18篇 |
2013年 | 35篇 |
2012年 | 38篇 |
2011年 | 43篇 |
2010年 | 21篇 |
2009年 | 34篇 |
2008年 | 39篇 |
2007年 | 40篇 |
2006年 | 24篇 |
2005年 | 24篇 |
2004年 | 30篇 |
2003年 | 21篇 |
2002年 | 15篇 |
2001年 | 13篇 |
2000年 | 12篇 |
1999年 | 62篇 |
1998年 | 600篇 |
1997年 | 305篇 |
1996年 | 209篇 |
1995年 | 98篇 |
1994年 | 92篇 |
1993年 | 111篇 |
1992年 | 19篇 |
1991年 | 30篇 |
1990年 | 23篇 |
1989年 | 29篇 |
1988年 | 20篇 |
1987年 | 29篇 |
1986年 | 23篇 |
1985年 | 32篇 |
1984年 | 4篇 |
1983年 | 8篇 |
1982年 | 12篇 |
1981年 | 16篇 |
1980年 | 23篇 |
1979年 | 4篇 |
1978年 | 7篇 |
1977年 | 41篇 |
1976年 | 92篇 |
1975年 | 5篇 |
1973年 | 5篇 |
排序方式: 共有2467条查询结果,搜索用时 15 毫秒
1.
Daniela Frasca Maria Romero Alain Diaz Denisse Garcia Seth Thaller Bonnie B. Blomberg 《International journal of molecular sciences》2021,22(4)
Senescent cells accumulate in the adipose tissue (AT) of individuals with obesity and secrete multiple factors that constitute the senescence-associated secretory phenotype (SASP). This paper aimed at the identification of B cells with a SASP phenotype in the AT, as compared to the peripheral blood, of individuals with obesity. Our results show increased expression of SASP markers in AT versus blood B cells, a phenotype associated with a hyper-metabolic profile necessary to support the increased immune activation of AT-derived B cells as compared to blood-derived B cells. This hyper-metabolic profile is needed for the secretion of the pro-inflammatory mediators (cytokines, chemokines, micro-RNAs) that fuel local and systemic inflammation. 相似文献
2.
The factors contributing to the duration of a motor unit action potential (MUAP) are believed to be well known, with both manual measurements and computer simulations agreeing with respect to MUAP durations approaching 10 ms. In this investigation, it is clearly demonstrated that use of a wide-open amplifier bandpass combined with signal-to-noise ratio enhancement results in MUAP durations approaching 30 ms recorded with either a macro or single-fiber electrode. Why the clinically recorded MUAP duration differs significantly from these physiologic durations is discussed. A hypothesis is presented whereby the major contributing factor toward MUAP duration is the total time of action potential transmembrane current flow along the muscle fiber from end-plate zone to musculotendinous junction. 相似文献
3.
4.
5.
Takeshi Kondo Sang Min Lee Michal Malicki Benoit Domercq Seth R. Marder Bernard Kippelen 《Advanced functional materials》2008,18(7):1112-1118
We report on a single‐layer organic memory device made of poly(N‐vinylcarbazole) embedded between an Al electrode and ITO modified with Ag nanodots (Ag‐NDs). Devices exhibit high ON/OFF switching ratios of 104. This level of performance could be achieved by modifying the ITO electrodes with some Ag‐NDs that act as trapping sites, reducing the current in the OFF state. Temperature dependence of the electrical characteristics suggest that the current of the low‐resistance state can be attributed to Schottky charge tunnelling through low‐resistance pathways of Al particles in the polymer layer and that the high‐resistance state can be controlled by charge trapping by the Al particles and Ag‐NDs. 相似文献
6.
Seth Green George Turkiyyah 《International journal for numerical methods in engineering》2004,61(3):380-405
We present a new method for enforcing boundary conditions within subdivision finite element simulations of thin shells. The proposed framework is demonstrated to be second-order accurate with respect to increasing refinement in the displacement and energy norm for simply supported, clamped, free and symmetric boundary conditions. Second-order accuracy on the boundary is consistent with the accuracy of subdivision-based approaches for the interior of a body. Our proposed framework is applicable to both triangular and quadrilateral refinement schemes, and does not impose any topological requirements upon the underlying subdivision control mesh. Several examples from an obstacle course of benchmark problems are used to demonstrate the convergence of the scheme. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
7.
We have used a variety of methods to characterize the genome of the archaeon Methanosarcina thermophila TM-1. Pulsed-field gel analysis indicates a genome size of 2.8 Mb. We have constructed a bacterial artificial chromosome (BAC) library of M. thermophila and have used it to generate physical maps for this organism. The library is made up of 384 clones with an average insert size of 58 kb representing 8.0 genome equivalents. The utility of the library for low-resolution physical mapping was shown by identifying NotI linking clones and using these to order the NotI macrorestriction fragments of M. thermophila into a 2.8 Mb map. Hybridization of nine single copy genes and a 16S rRNA sequence to these macrorestriction fragments forms the basis for the first genetic map in this organism. High-resolution physical maps, consisting of overlapping clones, have been created using HindIII fingerprints of BAC clones. In this way, we identified a minimal path of five clones that span a 270 kb NotI fragment. The ease of manipulating BAC clones makes the BAC system an excellent choice for the construction of low-resolution and high-resolution physical and genetic maps of archaeal genomes. It also provides a substrate for future genome-sequencing efforts. 相似文献
8.
9.
In 1989, 125 African-American and 123 European-American girls aged 12-14 years were enrolled in a 2-year study in which they maintained a menstrual calendar, recording the date and amount of menstrual bleeding. Weight, exercise, and stress during the previous week were recorded at the start of each menstrual cycle. Although only minor ethnic differences were observed in expected cycle length (29.3 vs. 28.8 days for European-American and African-American girls, respectively), more prominent differences were observed in the between-subjects standard deviation of cycle length (2.9 vs. 2.2 days, respectively) and in the odds of having a cycle longer than 45 days (odds ratio=1.86, 95% confidence interval 1.17-2.97) for European-American compared with African-American girls. Low weight for height and high levels of exercise increased the probability of having a cycle longer than 45 days and decreased expected cycle length of 13- to 45-day cycles. Additional investigation of potential ethnic differences in menstrual cycle characteristics is warranted. 相似文献
10.
Kelly Jeffrey A.; Murphy Debra A.; Sikkema Kathleen J.; Kalichman Seth C. 《Canadian Metallurgical Quarterly》1993,48(10):1023
Behavior change remains the only means for primary prevention of HIV disease. Psychology should take a leading role in efforts to curtail the epidemic, but has not contributed to HIV prevention at a level proportionate to the urgency of the crisis. The authors propose an updated agenda for behavioral research on AIDS-HIV prevention implementing accelerated community trials of promising behavior change models, conducting trials of community-level interventions on a large scale and focused on populations most vulnerable to HIV infections, establishing partnerships between HIV research and community service organizations, integrating efforts from across psychology disciplines to advance and refine HIV prevention interventions, and mobilizing interdisciplinary HIV prevention resources and communication mechanisms to rapidly translate research findings to community and public policy arenas. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献