全文获取类型
收费全文 | 9161篇 |
免费 | 1143篇 |
国内免费 | 560篇 |
专业分类
电工技术 | 159篇 |
技术理论 | 4篇 |
综合类 | 818篇 |
化学工业 | 132篇 |
金属工艺 | 8篇 |
机械仪表 | 34篇 |
建筑科学 | 1384篇 |
矿业工程 | 123篇 |
能源动力 | 419篇 |
轻工业 | 57篇 |
水利工程 | 6893篇 |
石油天然气 | 277篇 |
武器工业 | 2篇 |
无线电 | 23篇 |
一般工业技术 | 108篇 |
冶金工业 | 162篇 |
原子能技术 | 14篇 |
自动化技术 | 247篇 |
出版年
2024年 | 52篇 |
2023年 | 183篇 |
2022年 | 363篇 |
2021年 | 362篇 |
2020年 | 401篇 |
2019年 | 389篇 |
2018年 | 324篇 |
2017年 | 404篇 |
2016年 | 407篇 |
2015年 | 376篇 |
2014年 | 507篇 |
2013年 | 487篇 |
2012年 | 691篇 |
2011年 | 801篇 |
2010年 | 531篇 |
2009年 | 479篇 |
2008年 | 471篇 |
2007年 | 553篇 |
2006年 | 548篇 |
2005年 | 464篇 |
2004年 | 395篇 |
2003年 | 283篇 |
2002年 | 249篇 |
2001年 | 192篇 |
2000年 | 173篇 |
1999年 | 155篇 |
1998年 | 96篇 |
1997年 | 99篇 |
1996年 | 96篇 |
1995年 | 55篇 |
1994年 | 77篇 |
1993年 | 48篇 |
1992年 | 41篇 |
1991年 | 13篇 |
1990年 | 10篇 |
1989年 | 48篇 |
1988年 | 9篇 |
1987年 | 11篇 |
1986年 | 9篇 |
1985年 | 8篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1959年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
《Journal of Hydro》2014,8(2):88-94
Replacing existing river groynes with longitudinal training dams is considered as a promising flood mitigation measure in the main Dutch rivers, which can also serve to guarantee navigability during low flows and to create conditions favourable for ecological development. Whereas the bed response in the streamwise uniform part of a river trained by a longitudinal dam can be readily predicted, the bed response at the transition zones is unclear. In the present study, we investigate the local morphological effects resulting at the intake section of a longitudinal training dam, where the flow is distributed over the main channel and a side channel in between the dam and the river shore. A sediment recirculating model with a nearly undistorted geometry with respect to the prototype was setup. Lightweight polystyrene granulates were used as a surrogate for sediment, to properly scale the Shields parameter without compromising Froude scaling, and reach dynamical similarity. A laser scanner allowed collecting high-resolution bed elevation data. Results obtained under typical low flow and high flow conditions show a general deepening of the bed in the area adjacent to the training dam, in response to narrowing of the main channel. Scour at an upstream river groyne embedded in the model showed a scour hole which was deeper than realistic. Throughout the entire domain, bedforms developed featuring geometrical properties that reproduced the prototype conditions appropriately. Based on a comparison with characteristics from the River Waal, regarded as the prototype without a longitudinal dam, lightweight sediments were considered to be a proper choice for this study, in which bedload is the main sediment transport mode. The main conclusion regards the absence of significant morphodynamic developments at the intake section, both during the high flow experiment and during the low flow experiment, which can be attributed to the alignment of the dam with the local streamlines. 相似文献
993.
Adaptive robust control of uncertain time delay systems 总被引:1,自引:0,他引:1
The problem of adaptive robust control for uncertain linear systems with multiple delays occurring in the state variables is studied in this paper. The essential requirement for the uncertainties is that they satisfy matching conditions and are norm-bounded, but the bounds of the uncertainties are not necessarily known. An adaptive controller is developed based on linear matrix inequality technique and it is shown that the controller can guarantee the state variables of the closed loop system to converge, globally, uniformly and exponentially, to a ball in the state space with any pre-specified convergence rate. The effectiveness of our approach has been verified by its application in the control of river pollution process for the purpose of preserving standards of water constituents in streams. 相似文献
994.
995.
丁坝在三屯河河道整治中的成功经验 总被引:1,自引:0,他引:1
三屯河渠首以下3km范围内的河道,东西两岸毗邻三屯河东西干渠及耕地,河道两岸多年遭受洪水的严重侵蚀破坏,直接危及到了下游东、西引水干渠的安全。2000年,对该段河道采用丁坝型式进行了总体整治设计,当年秋季竣工。经过近3a的运行,整治效果较明显,彻底根治了水患,确保了东、西引水干渠的安全,取得了巨大的防洪效益。 相似文献
996.
J. A. Cambray 《河流研究与利用》1991,6(1):39-52
The potamodromous smallscale redfin minnow (Pseudobarbus asper) spawned in the riffle areas of the regulated Groot River, the major tributary of the Gamtoos River system, during controlled releases of water from Beervlei Dam. Water had been released at irregular intervals from this flood control dam solely for irrigating agricultural lands. Flushing flows removed accumulated salts from riverine pools and were followed by reduced flows which initiated spawning of the minnow species. Developing embryos of P. asper were found in the riffle zone of the main river channel during the water releases. Ripe-running males were located under the boulders in the riffles. Several developing embryos of Labeo umbratus were found with the P. asper eggs. Very little is known about the effects of man-made alterations to the river flow regime on the reproductive activity of fishes in the majority of South African river systems. The agriculturally based flooding regime at Beervlei may have increased the recruitment of the redfin minnow species. Water management must give cognizance to the biological and environmental requirements within the regulated river systems. Water release strategies from Beervlei Dam should include instream flow decisions based on the requirements of the aquatic environment as well as for agriculture. 相似文献
997.
周素芳 《水利水电科技进展》2004,24(3):36-38
介绍钱塘江北岸明清老海塘概况和工程自然条件 .提出运用板桩防冲墙技术解决塘脚防冲技术难题 ,并研制出可以遥控操作的多功能打桩机 .该技术在海宁明清海塘塘脚防冲工程中应用9 9km ,节省投资 5 2 0 0万元 ,并已在类似工程中推广应用 . 相似文献
998.
The influence of braided pattern on macrobenthic communities was studied in the Lower Drǒme River (France). The qualitative differences between embanked and braided sections are weak. The sessile species (for example Psychomyia pusilla) are more frequent in the embanked section whereas the drifting species (for example Baetis fuscatus) are more frequent in the braided section. The density of macroinvertebrates in the latter, especially in the secondary channels, is higher than in the embanked section, but the diversity remains low because the location of the channels changes at each extreme flood. 相似文献
999.
1000.
潼关高程[潼关(六)断面1000m^3/s流量相应水位]关系着渭河下游防洪和三门峡水库综合效益的发挥.由于影响潼关高程的因素非常复杂,因此必须采取多种措施综合治理来改善或降低潼关高程.通过对1993年和2001年东垆湾道两次自然裁弯的效果进行分析,认为东垆湾裁弯之后,可以增大局部比降,对裁湾上段河道的冲刷有明显作用,对潼关高程产生有利影响、2002年10月份东垆湾再次发生自然裁弯,根据三门峡水库蓄清排浑运用以来,历年水库溯源冲刷的实测资料分析,若维持目前裁弯后的流路,经过一个汛期水库降低水位运用,在较为有利的水沙条件下,裁弯使潼关高程大约可降低0.12m左右。 相似文献