全文获取类型
收费全文 | 2442篇 |
免费 | 92篇 |
国内免费 | 14篇 |
专业分类
电工技术 | 50篇 |
综合类 | 1篇 |
化学工业 | 327篇 |
金属工艺 | 57篇 |
机械仪表 | 44篇 |
建筑科学 | 85篇 |
矿业工程 | 20篇 |
能源动力 | 67篇 |
轻工业 | 169篇 |
水利工程 | 18篇 |
石油天然气 | 8篇 |
无线电 | 297篇 |
一般工业技术 | 360篇 |
冶金工业 | 649篇 |
原子能技术 | 26篇 |
自动化技术 | 370篇 |
出版年
2022年 | 15篇 |
2021年 | 27篇 |
2020年 | 20篇 |
2019年 | 44篇 |
2018年 | 45篇 |
2017年 | 27篇 |
2016年 | 48篇 |
2015年 | 44篇 |
2014年 | 56篇 |
2013年 | 126篇 |
2012年 | 74篇 |
2011年 | 108篇 |
2010年 | 88篇 |
2009年 | 100篇 |
2008年 | 98篇 |
2007年 | 86篇 |
2006年 | 100篇 |
2005年 | 70篇 |
2004年 | 77篇 |
2003年 | 56篇 |
2002年 | 72篇 |
2001年 | 47篇 |
2000年 | 33篇 |
1999年 | 48篇 |
1998年 | 168篇 |
1997年 | 104篇 |
1996年 | 50篇 |
1995年 | 55篇 |
1994年 | 51篇 |
1993年 | 53篇 |
1992年 | 38篇 |
1991年 | 21篇 |
1990年 | 21篇 |
1989年 | 31篇 |
1988年 | 30篇 |
1987年 | 28篇 |
1986年 | 23篇 |
1985年 | 31篇 |
1984年 | 25篇 |
1983年 | 23篇 |
1982年 | 20篇 |
1981年 | 14篇 |
1980年 | 19篇 |
1979年 | 11篇 |
1978年 | 10篇 |
1977年 | 18篇 |
1976年 | 43篇 |
1974年 | 19篇 |
1973年 | 21篇 |
1972年 | 11篇 |
排序方式: 共有2548条查询结果,搜索用时 93 毫秒
71.
Gaurang Pant Prakaipetch Punchaipetch M. J. Kim Robert M. Wallace Bruce E. Gnade 《Thin solid films》2004,460(1-2):242-246
Physical and electrical properties of hafnium silicon oxynitride (HfSixOyNz) dielectric films prepared by UV ozone oxidation of hafnium silicon nitride (HfSiN) followed by annealing to 450 °C are reported. Interfacial layer growth was minimized through room temperature deposition and subsequent ultraviolet/ozone oxidation. The capacitance–voltage (C–V) and current–voltage (I–V) characteristics of the as-deposited and annealed HfSixOyNz are presented. These 4 nm thick films have a dielectric constant of 8–9 with 12 at.% Hf composition, with a leakage current density of 3×10−5 A/cm2 at Vfb+1 V. The films have a breakdown field strength >10 MV/cm. 相似文献
72.
Spriet C Trinel D Waharte F Deslee D Vandenbunder B Barbillat J Héliot L 《Microscopy research and technique》2007,70(2):85-94
Studies of proteins' interaction in cells by FRET can take benefit from two important photo-physical properties describing fluorescent proteins: fluorescence emission spectrum and fluorescence lifetime. These properties provide specific and complementary information about the tagged proteins and their environment. However, none of them taken individually can completely quantify the involved fluorophore characteristics due to their multiparametric dependency with molecular environment, experimental conditions, and interpretation complexity. A solution to get a better understanding of the biological process implied at the cellular level is to combine the spectral and temporal fluorescence data acquired simultaneously at every cell region under investigation. We present the SLiM-SPRC160, an original temporal/spectral acquisition system for simultaneous lifetime measurements in 16 spectral channels directly attached to the descanned port of a confocal microscope with two-photon excitation. It features improved light throughput, enabling low-level excitation and minimum invasivity in living cells studies. To guarantee a fairly good level of accuracy and reproducibility in the measurements of fluorescence lifetime and spectra on living cells, we propose a rigorous protocol for running experiments with this new equipment that preserves cell viability. The usefulness of SLiM approach for the precise determination of overlapping fluorophores is illustrated with the study of known solutions of rhodamine. Then, we describe reliable FRET experiments in imaging mode realized in living cells using this protocol. We also demonstrate the benefit of localized fluorescence spectrum-lifetime acquisitions for the dynamic study of fluorescent proteins. proteins. 相似文献
73.
The electron incident-energy dependence of the relative intensities of Al and Si x-rays produced in a respirable-sized quartz particle by scanning electron microscopy is sensitive to the inhomogeneity of the distribution of Al and Si in the particle. Realistic Monte Carlo calculations of this energy dependence validate the proposal to use this effect for the detection of particles in which an aluminosilicate coating occludes the surface of a silica core. 相似文献
74.
75.
Alvaro J. Romera Gil Levy Pierre C. Beukes Dave A. Clark Chris B. Glassey 《Nutrient Cycling in Agroecosystems》2012,92(3):329-346
On New Zealand dairy farms, it is the nitrogen excreted directly onto pasture, particularly urine, that drives nitrogen (N)
leaching from the farm. A new framework (UPF: Urine Patch Framework) is presented that post-processes the results of a whole
farm model and runs a mechanistic soil model to simulate the urine patches. Two alternative methods to simulate the spatial
distribution of urine patches were implemented and compared (Grid: spatially explicit, and Probabilistic: based on the probability of different temporal urination patterns). This paper describes the implementation of these two
methods in connection with a Whole Farm Model; and compares the N leaching predictions with observed data. Two examples are
provided, one analyzing the impact of urine patch overlap and another, the relative risk of N leaching at different times
of urinary N deposition. The model showed good correlation and predictive ability between simulated annual N leaching results
and observed data [R2 = 94 %, mean relative prediction error (MRPE) = 10 % for Grid and R2 = 72 %, MRPE = 20 % for Probabilistic]. The two methods produced similar results across an 8-year period for monthly and annual N leaching (R2 = 96 %, MRPE = 10 % and R2 = 86 %, MRPE = 8 %; respectively). Only 8 % of the paddock area was covered with multiple urinations during 1 year, but as
much as 39 % of the total urine volume was deposited on overlapped patches. Systematically removing all urinary N for 1 month
in either May or June reduced N leaching by approximately 20 %. Avoiding urinary N deposition during autumn or early winter
could be highly effective in mitigating N leached during the following winter. 相似文献
76.
77.
78.
79.
80.