全文获取类型
收费全文 | 121431篇 |
免费 | 10718篇 |
国内免费 | 5148篇 |
专业分类
电工技术 | 7377篇 |
技术理论 | 7篇 |
综合类 | 7789篇 |
化学工业 | 20872篇 |
金属工艺 | 6747篇 |
机械仪表 | 7553篇 |
建筑科学 | 10049篇 |
矿业工程 | 3572篇 |
能源动力 | 3590篇 |
轻工业 | 7945篇 |
水利工程 | 2207篇 |
石油天然气 | 7589篇 |
武器工业 | 932篇 |
无线电 | 13833篇 |
一般工业技术 | 14667篇 |
冶金工业 | 5657篇 |
原子能技术 | 1336篇 |
自动化技术 | 15575篇 |
出版年
2024年 | 598篇 |
2023年 | 2136篇 |
2022年 | 3732篇 |
2021年 | 5093篇 |
2020年 | 3901篇 |
2019年 | 3277篇 |
2018年 | 3506篇 |
2017年 | 4062篇 |
2016年 | 3418篇 |
2015年 | 4865篇 |
2014年 | 5917篇 |
2013年 | 6996篇 |
2012年 | 7722篇 |
2011年 | 8245篇 |
2010年 | 7190篇 |
2009年 | 6829篇 |
2008年 | 6594篇 |
2007年 | 6246篇 |
2006年 | 6507篇 |
2005年 | 5644篇 |
2004年 | 3865篇 |
2003年 | 3391篇 |
2002年 | 3145篇 |
2001年 | 2862篇 |
2000年 | 3038篇 |
1999年 | 3247篇 |
1998年 | 2731篇 |
1997年 | 2309篇 |
1996年 | 2142篇 |
1995年 | 1865篇 |
1994年 | 1496篇 |
1993年 | 1078篇 |
1992年 | 876篇 |
1991年 | 687篇 |
1990年 | 497篇 |
1989年 | 446篇 |
1988年 | 356篇 |
1987年 | 246篇 |
1986年 | 169篇 |
1985年 | 97篇 |
1984年 | 65篇 |
1983年 | 50篇 |
1982年 | 64篇 |
1981年 | 39篇 |
1980年 | 35篇 |
1979年 | 10篇 |
1978年 | 3篇 |
1965年 | 3篇 |
1959年 | 5篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
111.
随着各高校校园网络规模的不断扩大和各种应用的急剧增加,各种新的网络问题也在不断出现。Sniffer是网络管理员进行网络管理的有效工具,可以有效地对网络进行实时监控,及时发现网络中存在的各种问题。本文首先介绍了Sniffer的工作原理,其次给出了实现Sniffer功能的编程流程图,并用C语言给出了编程所需的关键代码。 相似文献
112.
113.
114.
115.
116.
117.
118.
In this paper mud was treated as the Bingham fluid. In staggered grids, two-dimensional incompressible Navier-Stokes equations for non-Newtonian fluid was solved by the MAC method. Numerical simulations were conducted on mud bed-generating phenomenon and mud impacting a wall along a slope. The distributions of free surface, pressure and velocity of mud and water were obtained. The results indicate that the computed layer thickness of mud bed almost equals the theoretically predicted value. Because of the differences in constitutive relationship, the distributions of free surface are different for water and mud. The distortion of water free surface is much more complicated. 相似文献
119.
Xu Baowen Zhang Weifeng 《电子科学学刊(英文版)》2002,19(4)
The users' interest can be mined from the web cache and can be used widely. The interest can be specialized by the two-tuple (term, weight) in the simple interest model, in which the association relations are not mined, and then the interest cannot be associated in expressing the users' interest. Based on analyzing the WWW cache model, this letter brings forward a two-dimensional interest model and gives the interrelated methods on how to store the two-dimensional interest model effectively. 相似文献
120.
The kinetics of substrate removal by the liver and the resulting nonlinear changes in unbound fraction along the flow path at varying input drug concentrations were examined by a model simulation study. Specifically, we varied the binding association constant, KA, and the Michaelis-Menten constants (Km and Vmax) to examine the steady state drug removal (expressed as hepatic extraction ratio E) and changes in drug binding for (i) unienzyme systems and (ii) simple, parallel metabolic pathways; zonal metabolic heterogeneity was also added as a variable. At low KA, E declined with increasing input drug concentration, due primarily to saturation of enzymes; only small differences in binding were present across the liver. At high KA, a parabolic profile for E with concentration was observed; changes in unbound fraction between the inlet and the outlet of the liver followed in parallel fashion. Protein binding was the rate-determining step at low input drug concentrations, whereas enzyme saturation was the rate-controlling factor at high input drug concentration. Heterogeneous enzymic distribution modulated changes in unbound fraction within the liver and at the outlet. Despite marked changes in unbound fraction occurring within the liver for different enzymic distributions, the overall transhepatic differences were relatively small. We then investigated the logarithmic average unbound concentration and the length averaged concentration as estimates of substrate concentration in liver in the presence of nonlinear drug binding. Fitting of simulated data, with and without assigned random error (10%), to the Michaelis-Menten equation was performed; fitting was repeated for simulated data obtained with presence of a specific inhibitor of the high-affinity, anteriorly distributed pathway. Results were similar for both concentration terms: accurate estimates were obtained for anterior, high affinity pathways; an overestimation of parameters was observed for the lower affinity posteriorly distributed pathways. Improved estimations were found for posteriorly distributed pathways upon inhibition with specific inhibitors; with added random error, however, the improvement was much decreased. We applied the method for fitting of several sets of metabolic data obtained from rat liver perfusion studies performed with salicylamide (SAM) (i) without and (ii) with the presence of 2,6-dichloro-4-nitrophenol (DCNP), a SAM sulfation inhibitor. The fitted results showed that SAM sulfation was a high-affinity high-capacity pathway; SAM glucuronidation was of lower affinity but comparable capacity as the sulfation pathway, whereas SAM hydroxylation was of lower affinity and lower capacity. 相似文献