全文获取类型
收费全文 | 8471篇 |
免费 | 89篇 |
国内免费 | 133篇 |
专业分类
电工技术 | 92篇 |
综合类 | 48篇 |
化学工业 | 872篇 |
金属工艺 | 189篇 |
机械仪表 | 428篇 |
建筑科学 | 530篇 |
矿业工程 | 212篇 |
能源动力 | 45篇 |
轻工业 | 2070篇 |
水利工程 | 127篇 |
石油天然气 | 118篇 |
武器工业 | 32篇 |
无线电 | 362篇 |
一般工业技术 | 2886篇 |
冶金工业 | 153篇 |
原子能技术 | 103篇 |
自动化技术 | 426篇 |
出版年
2023年 | 13篇 |
2022年 | 15篇 |
2021年 | 26篇 |
2020年 | 18篇 |
2019年 | 18篇 |
2018年 | 19篇 |
2017年 | 14篇 |
2016年 | 16篇 |
2015年 | 25篇 |
2014年 | 45篇 |
2013年 | 41篇 |
2012年 | 812篇 |
2011年 | 1143篇 |
2010年 | 227篇 |
2009年 | 110篇 |
2008年 | 776篇 |
2007年 | 758篇 |
2006年 | 628篇 |
2005年 | 603篇 |
2004年 | 495篇 |
2003年 | 423篇 |
2002年 | 364篇 |
2001年 | 285篇 |
2000年 | 298篇 |
1999年 | 162篇 |
1998年 | 97篇 |
1997年 | 92篇 |
1996年 | 82篇 |
1995年 | 72篇 |
1994年 | 76篇 |
1993年 | 59篇 |
1992年 | 76篇 |
1991年 | 58篇 |
1990年 | 67篇 |
1989年 | 66篇 |
1988年 | 41篇 |
1987年 | 56篇 |
1986年 | 49篇 |
1985年 | 71篇 |
1984年 | 55篇 |
1983年 | 75篇 |
1982年 | 50篇 |
1981年 | 36篇 |
1980年 | 40篇 |
1979年 | 41篇 |
1978年 | 14篇 |
1977年 | 8篇 |
1976年 | 10篇 |
1966年 | 8篇 |
1965年 | 7篇 |
排序方式: 共有8693条查询结果,搜索用时 13 毫秒
51.
52.
The effects of cooking viz. pressure-cooking and broiling and storage at 4 °C for six days and -10 °C for 90 days on lipid oxidation and development of cholesterol oxidation products in mutton were studied. Results revealed that cooking of meat significantly increased the total lipids, phospholipids, cholesterol, glycolipids, free fatty acids and glycerides, but they did not change during refrigerated and frozen storage. The TBA values increased on cooking and during storage. However, the values were below the threshold level for rancidity development. The following cholesterol oxidation products were separated by thin layer chromatography cholestanetriol, 7-α-hydroxy cholesterol, 19-hydroxycholesterol, 7-ketocholesterol, cholesterol-α-epoxide, cholesterol-β-epoxide and an unidentified fraction. All these fractions except the unidentified fraction increased on cooking. On refrigerated and even on frozen storage all these fractions increased except the unidentified fraction, which showed a concomitant reduction. The changes in broiled meat were more pronounced compared to pressure-cooked meat. Results clearly indicated that even frozen storage of cooked meat did not prevent the development of cholesterol oxidation products. 相似文献
53.
一维模型可以定量模拟沉积、压实、流体流动、热流和烃类演化等地质过程与时间的关系。输入钻井数据,如地层厚度、孔隙度与深度、地温梯度、镜质体反射率与深度、剩余流体压力与深度来限定动力模型。文中纳瓦茵盆地COST、号井模型重现了本井的埋藏史、流体流动史、热深化史和烃类生成史。 相似文献
54.
每逢二月,《宝石和宝石学》杂志社宝石新闻栏的编辑与宝石学家、珠宝商、宝石收藏家以及宝石业余爱好者一样,希望能到亚利桑那州图森参观每年一度的宝石、矿物博览会。图森博览会实际上是遍布整个城市的一系列博览会,是欣赏宝石世界之新、奇、特珍品的极好机会。今年的博览会旧往年一样有趣,令人目不暇接、留恋忘返。 相似文献
55.
设计人员将赛灵思多款FPGA互联,可以开发出新一类超级计算机,并通过定制用于多种应用领域的工作。在过去的20年里,许多超级计算机架构都同时采用了微处理器和FPGA,由微处理器发挥系统大脑的作用,FPGA则通常负责从CPU处卸载部分计算任务。事实上,对一代又一代超级计算机而言,这种将FPGA与独立的微处理器相搭配的方式被证明是一种成功的组合方案。 相似文献
56.
Gilja V Chestek CA Diester I Henderson JM Deisseroth K Shenoy KV 《IEEE transactions on bio-medical engineering》2011,58(7):1891-1899
Neural prosthetic systems aim to help disabled patients by translating neural signals from the brain into control signals for guiding computer cursors, prosthetic arms, and other assistive devices. Intracortical electrode arrays measure action potentials and local field potentials from individual neurons, or small populations of neurons, in the motor cortices and can provide considerable information for controlling prostheses. Despite several compelling proof-of-concept laboratory animal experiments and an initial human clinical trial, at least three key challenges remain which, if left unaddressed, may hamper the translation of these systems into widespread clinical use. We review these challenges: achieving able-bodied levels of performance across tasks and across environments, achieving robustness across multiple decades, and restoring able-bodied quality proprioception and somatosensation. We also describe some emerging opportunities for meeting these challenges. If these challenges can be largely or fully met, intracortically based neural prostheses may achieve true clinical viability and help increasing numbers of disabled patients. 相似文献
57.
A radio frequency (RF) telemetry system with a shape memory alloy microelectrode was designed and fabricated. The total size and weight are 15 mm x 8 mm and 0.1 g, respectively. Since the telemeter is small and light enough to be loaded on a small animal such as an insect, the system can be used for the neural recording of a freely moving insect. The RF-telemeter can transmit signals by frequency modulation transmission at 80-90 MHz. The transmitted signals can be received up to about 16 meters away from the telemeter with a high signal-to-noise ratio. The neural activity can be detected without attenuation by using an instrumentation amplifier with its input impedance set to 2 Mohms at 1 kHz. The telemeter was loaded on a cockroach and the neural activity during a free-walk was successfully measured through this telemetry system. 相似文献
58.
The influence of red blood cell (RBC) aggregation on transparency of blood in the red-near infrared spectral range is investigated. We argue that for relatively thin blood layers the light diffraction on aggregates becomes the dominant phenomenon. The nature of pulsatile changes of blood transparency is explained by pulsations of RBC aggregate size. For another case of over-systolic vessel occlusion the following time evolution of blood transparency strongly depends on light wavelength. This dependence may serve as a basis for an alternative approach to noninvasive blood tests: occlusion spectroscopy. Theoretical results well correspond to both in vivo and in vitro measurements reproducing pulsatile blood flow and long occlusion as well. 相似文献
59.
Coherent optical orthogonal frequency division multiplexing (CO-OFDM) is considered as a key solution for long haul optical fiber communication systems thanks to its high spectral efficiency and robustness against chromatic dispersion. We have investigated a CO-OFDM based on quadrature phase shift keying (QPSK)-OFDM and 16 quadrature amplitude modulation (16QAM)-OFDM over 500 km uncompensated fiber links. The simulation results show that the proposed system is a promising solution to meet the aggregate data rate demands cost effectively in future high-speed optical communication systems. 相似文献
60.
Yoshino T Sotome I Ohtani T Isobe S Oshita S Maekawa T 《Journal of electron microscopy》2000,49(3):483-486
Barley cells cut from a sprout were exposed to either air or high-pressure xenon gas for 3 days and the surface of those cells was observed by atomic force microscopy (AFM) to examine the effect of the gas treatment. This method enabled the direct observation of the fresh surface of the barley cells in solution at high resolution. The cuticle layer was preserved on the primary cell wall of 0.48 MPa xenon gas-treated barley cells, while air-treated barley cells lost the cuticle layer from the primary cell wall. These findings indicate that the high-pressure xenon gas treatment is effective to preserve the cuticle layer attached to the primary cell wall. AFM is a powerful tool for the observation of the surface structure of living plant cells in solution. 相似文献