全文获取类型
收费全文 | 12826篇 |
免费 | 1066篇 |
国内免费 | 772篇 |
专业分类
电工技术 | 435篇 |
技术理论 | 8篇 |
综合类 | 652篇 |
化学工业 | 1795篇 |
金属工艺 | 354篇 |
机械仪表 | 438篇 |
建筑科学 | 878篇 |
矿业工程 | 405篇 |
能源动力 | 825篇 |
轻工业 | 484篇 |
水利工程 | 815篇 |
石油天然气 | 218篇 |
武器工业 | 58篇 |
无线电 | 1892篇 |
一般工业技术 | 1819篇 |
冶金工业 | 377篇 |
原子能技术 | 548篇 |
自动化技术 | 2663篇 |
出版年
2024年 | 14篇 |
2023年 | 199篇 |
2022年 | 229篇 |
2021年 | 464篇 |
2020年 | 384篇 |
2019年 | 335篇 |
2018年 | 313篇 |
2017年 | 446篇 |
2016年 | 487篇 |
2015年 | 425篇 |
2014年 | 765篇 |
2013年 | 947篇 |
2012年 | 760篇 |
2011年 | 947篇 |
2010年 | 674篇 |
2009年 | 776篇 |
2008年 | 744篇 |
2007年 | 826篇 |
2006年 | 702篇 |
2005年 | 641篇 |
2004年 | 583篇 |
2003年 | 469篇 |
2002年 | 416篇 |
2001年 | 332篇 |
2000年 | 258篇 |
1999年 | 191篇 |
1998年 | 184篇 |
1997年 | 170篇 |
1996年 | 135篇 |
1995年 | 136篇 |
1994年 | 134篇 |
1993年 | 106篇 |
1992年 | 73篇 |
1991年 | 53篇 |
1990年 | 40篇 |
1989年 | 69篇 |
1988年 | 38篇 |
1987年 | 25篇 |
1986年 | 24篇 |
1985年 | 34篇 |
1984年 | 17篇 |
1983年 | 17篇 |
1982年 | 20篇 |
1981年 | 22篇 |
1980年 | 10篇 |
1979年 | 8篇 |
1978年 | 4篇 |
1976年 | 4篇 |
1959年 | 3篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 306 毫秒
41.
梁民基 《小型微型计算机系统》1994,15(12):41-46
本文给出了作者开发的一个单处理机实时多任务操作系统的响应性能(响应时间,同步时间)的实验结果和/或估算。与国外同期文献发表的数据相比,指标先进。 相似文献
42.
河道冲刷和清水水流河床冲刷率 总被引:14,自引:0,他引:14
在冲积河流里。水流条件变化如洪水、水库泄放清水、河道渠化等使挟沙力不饱和引起冲刷,称为河道冲刷。这与水工建筑造成的局部冲刷不同。河道冲刷深度主要决定于冲刷率和冲刷历时。本研究通过对各种泥沙大量实验,证明了河床冲刷率正比于水流提供的冲刷功率并依赖于泥沙粒径和容重,首次提出了冲刷率公式。经验证,该公式可以用于非恒定流输沙和河流洪水冲刷计算。 相似文献
43.
J. S. Kim D. G. Seiler R. A. Lancaster M. B. Reine 《Journal of Electronic Materials》1996,25(8):1215-1220
Variable-magnetic-field Hall measurements (0 to 1.5 T) are performed on very-narrow-gap bulk-grown Hg1−xCdxTe single crystals (0.165 ≤ x ≤ 0.2) at various temperatures (10 to 300K). The electron densities and mobilities are obtained
within the one-carrier (electrons) approximation of the reduced-con-ductivity-tensor scheme. The present data together with
the selected data set reported by other workers exhibit a pronounced peak when the electron mobility is plotted against the
alloy composition x-value which has been predicted to be due to the effective-mass minimum at the bandgap-crossing (Eg ≈ 0). The observed position (x ≈ 0.165), height (≈4 x 102 m2Vs), and width (≈0.01 in x) of the mobility-peak can be explained by a simple simulation involving only ionized-impurity scattering.
A lower bound of the effective mass is introduced as a fitting parameter to be consistent with the finiteness of the observed
electron mobility and is found to be of the order of 10−4 of the mass of a free electron. 相似文献
44.
The standard deviation of differential pressure fluctuations between pressure taps in a 31.7 mm i.d. vertical downer was found to be proportional to the square root of the distance between the taps when measured under otherwise constant conditions. This finding confirms the prediction of a theoretical model based on the Central Limit Theorem of sampling statistics. Although the paper only presents experimental confirmation for downward flow, the theoretical model should be valid for flows in all orientations. Except at very low solids flows, the pressure gradient was found to be positive in the flow direction, indicating that rise in pressure due to static pressure more than compensated for frictional pressure losses. 相似文献
45.
46.
Dan C. DeBorde William W. Woessner Bruce Lauerman Patrick Ball 《Water research》1998,32(12):3781-3785
At the present time, somatic and male-specific coliphage and human enterovirus groups are being considered as indicators of possible pathogenic human enteric virus contamination from fecal contamination. A primary attribute for any indicator of fecal contamination is its prevalence at the source and in associated ground water. It must be consistently found in the source material at concentrations that are measurable with available techniques. Over a period of ten months, male-specific and somatic coliphage ranged from 7000 to 4,000,000 PFU/L in the effluent from a multi-user septic-tank. Unlike the values determined for septic-tank effluent, coliphage concentrations measured in ground water over this same period only varied by five-fold. Coliphage concentration in ground water under the down-gradient edge of the drainfield contained 1000 PFU/L. This concentration decreased at −1 log10/5 m during 17.4 m of ground-water transport. From these data, coliphage concentrations in septic-tank effluent seem sufficient to allow their use as indicators of fecal contamination in ground water. 相似文献
47.
48.
Modeling video sources for real-time scheduling 总被引:1,自引:0,他引:1
What is the impact of the autocorrelation of variable-bit-rate (VBR) sources on real-time scheduling algorithms? Our results show that the impact of long term, or interframe, autocorrelation is negligible, while the impact of short term, or intraframe, autocorrelation can be significant. Such results are essentially independent of the video coding scheme employed. To derive these results, video sequences are modeled as a collection of stationary subsequences called scenes. Within a scene, a statistical model is derived for both the sequence of frames and of slices. The model captures the distribution and the autocorrelation function of real-time video data. In previous work, the pseudoperiodicity of the slice level auto-correlation function made it difficult to develop a simple yet accurate model. We present a generalization of previous methods that can easily capture this pseudoperiodicity and is suited for modeling a greater variety of autocorrelation functions. By simply tuning a few parameters, the model reproduces the statistic behavior of sources with different types and levels of correlation on both the frame and the slice level. 相似文献
49.
为了探讨长江上游流域水土流失及泥沙输移规律,选取嘉陵江中游的支流李子溪为典型流域进行分析研究,在实地调查,野外测验及应用1960年-1991年实测降雨、径流、输沙资料的基础上,利用单因子相关分析和多因子回归分析,分别建立了输水利沙量、最大输沙率计算方程。在此基础上,参照径流瞬时单位线原理,以线性时不变系统为基础,建立输沙瞬时单位线模型。通过输沙单位线与时段净侵蚀量的卷积得到流域出口断面的输沙率过程 相似文献
50.
New measurements of the vapor-phase viscosity of phenol were performed from 437 up to 624 K and for densities between 0.006 and 0.023 mol · L–1 in an all-quartz oscillating-disk viscometer with small gaps. Thus, including our own measurements reported earlier, experimental data are available in the temperature range between 376 and 639 K and in the density range from 0.001 up to 0.023 mol · L–1. The data were evaluated with a density series for the viscosity in which only a linear density contribution is included. The values of the second viscosity virial coefficient obtained for phenol as well as for benzene, toluene, and p-xylene were compared with results of the Rainwater-Friend theory and of the modified Enskog theory on the basis of the Lennard-Jones 12-6 potential. The agreement is reasonable, when the potential parameter ratios determined by Bich and Vogel are used. The influence of bound dimers seems to be already taken into account in the three-monomer contribution according to Hoffman and Curtiss.Paper dedicated to Professor Joseph Kestin. 相似文献