全文获取类型
收费全文 | 1737952篇 |
免费 | 69915篇 |
国内免费 | 35708篇 |
专业分类
电工技术 | 65764篇 |
综合类 | 45489篇 |
化学工业 | 293825篇 |
金属工艺 | 87720篇 |
机械仪表 | 63785篇 |
建筑科学 | 68590篇 |
矿业工程 | 26942篇 |
能源动力 | 58606篇 |
轻工业 | 137404篇 |
水利工程 | 26122篇 |
石油天然气 | 48266篇 |
武器工业 | 5622篇 |
无线电 | 228572篇 |
一般工业技术 | 294164篇 |
冶金工业 | 135454篇 |
原子能技术 | 39849篇 |
自动化技术 | 217401篇 |
出版年
2022年 | 20265篇 |
2021年 | 32822篇 |
2020年 | 24380篇 |
2019年 | 23192篇 |
2018年 | 23270篇 |
2017年 | 23837篇 |
2016年 | 29874篇 |
2015年 | 32849篇 |
2014年 | 48471篇 |
2013年 | 111336篇 |
2012年 | 63170篇 |
2011年 | 75567篇 |
2010年 | 70327篇 |
2009年 | 77767篇 |
2008年 | 71433篇 |
2007年 | 67034篇 |
2006年 | 67417篇 |
2005年 | 57273篇 |
2004年 | 53887篇 |
2003年 | 48912篇 |
2002年 | 46239篇 |
2001年 | 40366篇 |
2000年 | 37118篇 |
1999年 | 32088篇 |
1998年 | 29082篇 |
1997年 | 29162篇 |
1996年 | 27956篇 |
1995年 | 27348篇 |
1994年 | 26008篇 |
1993年 | 25859篇 |
1992年 | 25076篇 |
1991年 | 22038篇 |
1990年 | 22526篇 |
1989年 | 21458篇 |
1988年 | 19852篇 |
1987年 | 18298篇 |
1986年 | 17638篇 |
1985年 | 21024篇 |
1984年 | 21599篇 |
1983年 | 19534篇 |
1982年 | 18734篇 |
1981年 | 18803篇 |
1980年 | 17425篇 |
1979年 | 18032篇 |
1978年 | 17239篇 |
1977年 | 16320篇 |
1976年 | 16180篇 |
1975年 | 15569篇 |
1974年 | 15157篇 |
1973年 | 15189篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Mohanalakshmi Sabapati Narahari N. Palei Ashok Kumar C.K. Ravindra Babu Molakpogu 《Drug development and industrial pharmacy》2019,45(4):577-586
The present study was aimed to develop Annona muricata fruit extract loaded solid lipid nanoparticles (SLNs) and explore its cytotoxic potential in vitro model of breast cancers. Extract loaded SLNs were successfully prepared by high-pressure homogenization followed by ultrasonication method and optimized using 23 full factorial design. The extract loaded SLNs were characterized using different parameters such as particle size (PS), % entrapment efficiency (EE), zeta potential (ZP) and % cumulative drug release (CDR). The SLNs formulation was optimized on the basis of software analysis with an overall desirability factor. The PS and %EE of the optimized formulation were found to be 134.8?nm and 83.26%, respectively. The optimized formulation showed a CDR of 79.83% up to 48?h. In vitro cytotoxicity efficacy of extract loaded SLNs was determined using MTT and Apoptosis assay and compared to that of a free extract. The SLNs showed a notable apoptotic effect and better efficacy to kill MCF7 cancer cells as compared to free extract. Thus, extract loaded SLNs could be an alternative dosage form which possibly controls therapeutic action with reducing side effect. 相似文献
992.
Measurement Techniques - We consider measurements of pitch and roll angles using compensation pendulum accelerometers with closed feedback. A three-component mathematical model of a single-axis... 相似文献
993.
Russian Microelectronics - Experimental studies on the influence of the electric mode (active and passive) on dose of the radiation resistance of microcircuits of different structural and... 相似文献
994.
995.
Seung‐Hyun Kim Victoria Hwang Sang Goo Lee Jong‐Wook Ha Vinothan N. Manoharan Gi‐Ra Yi 《Small (Weinheim an der Bergstrasse, Germany)》2019,15(23)
Hollow carbon–silica nanospheres that exhibit angle‐independent structural color with high saturation and minimal absorption are made. Through scattering calculations, it is shown that the structural color arises from Mie resonances that are tuned precisely by varying the thickness of the shells. Since the color does not depend on the spatial arrangement of the particles, the coloration is angle independent and vibrant in powders and liquid suspensions. These properties make hollow carbon–silica nanospheres ideal for applications, and their potential in making flexible, angle‐independent films and 3D printed films is explored. 相似文献
996.
G. Inglese 《Inverse Problems in Science & Engineering》2019,27(4):439-459
We deal with the mathematical model of the incremental degradation of the internal coating (e.g. a polymeric material) of a metallic pipe in which a fluid flows relatively fast. The fluid drags solid impurities so that longitudinal scratches, inaccessible to any direct inspection procedure, are produced on the coating. Time evolution of this kind of defects can be reconstructed from the knowledge of a sequence of temperature maps of the external surface. The time-varying orthogonal section of this damaged interface is determined as a function of time and polar angle through the identification of a suitable effective heat transfer coefficient by means of Thin Plate Approximation. 相似文献
997.
This paper deals with the determination of an initial condition in degenerate hyperbolic equation from final observations. With the aim of reducing the execution time, this inverse problem is solved using an approach based on double regularization: a Tikhonov’s regularization and regularization in equation by viscose-elasticity. So, we obtain a sequence of weak solutions of degenerate linear viscose-elastic problems. Firstly, we prove the existence and uniqueness of each term of this sequence. Secondly, we prove the convergence of this sequence to the weak solution of the initial problem. Also we present some numerical experiments to show the performance of this approach. 相似文献
998.
Ivonne Sgura Amos S. Lawless Benedetto Bozzini 《Inverse Problems in Science & Engineering》2019,27(5):618-647
The process of electrodeposition can be described in terms of a reaction-diffusion partial differential equation (PDE) system that models the dynamics of the morphology profile and the chemical composition. Here we fit such a model to the different patterns present in a range of electrodeposited and electrochemically modified alloys using PDE constrained optimization. Experiments with simulated data show how the parameter space of the model can be divided into zones corresponding to the different physical patterns by examining the structure of an appropriate cost function. We then use real data to demonstrate how numerical optimization of the cost function can allow the model to fit the rich variety of patterns arising in experiments. The computational technique developed provides a potential tool for tuning experimental parameters to produce desired patterns. 相似文献
999.
Metallurgical and Materials Transactions B - The influence of Mn segregation that occurs during casting on recrystallization kinetics has been explored for a C-Mn automotive steel. A homogenization... 相似文献
1000.
ABSTRACTThis article examines equity concerns and inherent conflicts related to rural–urban water supply allocation and use, with focus on Metro Manila. Going beyond the much-discussed difficulty farmers experience from an allocation policy prioritizing urban water requirements, it shows that inequity in raw water allocation is linked to, and further exacerbated by, inequities in urban domestic water provision. Moreover, it highlights the need for broader equity reviews, using the concept of the rural–urban water equity nexus to draw attention to key equity considerations across space and scale that otherwise might remain invisible. 相似文献