首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   132457篇
  免费   8570篇
  国内免费   4312篇
电工技术   9665篇
技术理论   19篇
综合类   13743篇
化学工业   7411篇
金属工艺   2751篇
机械仪表   5350篇
建筑科学   23551篇
矿业工程   4638篇
能源动力   3036篇
轻工业   17968篇
水利工程   7551篇
石油天然气   3806篇
武器工业   537篇
无线电   9264篇
一般工业技术   6549篇
冶金工业   8167篇
原子能技术   787篇
自动化技术   20546篇
  2024年   444篇
  2023年   1363篇
  2022年   2480篇
  2021年   3278篇
  2020年   3531篇
  2019年   2718篇
  2018年   2518篇
  2017年   3172篇
  2016年   3618篇
  2015年   4038篇
  2014年   10118篇
  2013年   8209篇
  2012年   9642篇
  2011年   10315篇
  2010年   7857篇
  2009年   8400篇
  2008年   7955篇
  2007年   9577篇
  2006年   8489篇
  2005年   6990篇
  2004年   6092篇
  2003年   5392篇
  2002年   4481篇
  2001年   3281篇
  2000年   2614篇
  1999年   2013篇
  1998年   1351篇
  1997年   1038篇
  1996年   865篇
  1995年   728篇
  1994年   543篇
  1993年   405篇
  1992年   320篇
  1991年   237篇
  1990年   168篇
  1989年   180篇
  1988年   143篇
  1987年   94篇
  1986年   108篇
  1985年   112篇
  1984年   104篇
  1983年   103篇
  1982年   47篇
  1981年   32篇
  1980年   32篇
  1979年   16篇
  1978年   9篇
  1977年   20篇
  1975年   10篇
  1959年   16篇
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
1.
介绍了目前最炙手可热的REST架构风格,该风格顺应Web2.0的兴起,完美的匹配了云计算时代来临的可扩展要求,在各种应用场景中都得到了充分的表现。根据其技术特点,分析了该风格的API在移动通信网络管理中的应用,从网管系统内部、网管系统之间以及网管系统与上层APP应用之间等多方面对是否适用于REST风格以及如何在合适的位置使用REST API进行了分析。  相似文献   
2.
本文提出了将智能全站仪这种精密测量仪器广泛应用于田赛项目测量中,并结合其他科技元素用于解决田赛项目中跳远、投掷等项目的测量及数据管理问题,实现实时、自动、准确地裁定和报告比赛成绩。  相似文献   
3.
高校是培养人才的摇篮,肩负着科教兴国、人才强国两大历史性战略任务。由于社会环境的复杂化,人际关系的交错性,新时代的大学生行为状况给高校学生管理工作带来了新的挑战。针对新时期大学生行为特点,我们通过加强党建工作、强化学风建设、做好班级自主管理和深化社会服务四个方面工作进行分析,提出了全面引导、约束、规范和优化大学生的行为的建议和对策,从而有效解决新形势下普通高校学生管理工作的实际困难。  相似文献   
4.
The synergistic application of hot water dip at 42 °C for 30 min and 1% chitosan coating on differentiation in postharvest quality traits, microstructure as well as microbiological evolution of wolfberry fruits was investigated. Fresh wolfberry fruits were stored at 2 ± 0.5 °C and 90% relative humidity (RH) for 28 days. Results indicated the combination of prestorage heat treatment and chitosan coating maintained higher levels of ascorbic acid, total phenolic contents and antioxidant capacity as well as lower decay, compared with untreated wolfberry fruits. The possible mechanism was that the heat treatment almost sealed open stomata to limit the sites of pathogen penetration into fruits independently, followed by the biofilm formed by chitosan which controlled secondary infections as well as slowed changes in fruit respiration and metabolic activity in wolfberries. The synergistically treated fruit also exhibited a higher acceptability obtained by sensory analysis after cold storage. In this sense, the integrated application of heat treatment and chitosan coating could be regarded as an effective strategy to extend storage life and maintain the postharvest quality of wolfberry fruits.  相似文献   
5.
An Intermediate Bulk Container (IBC) was punctured during its handling, releasing oil onto soil at an environmentally-sensitive region of Australia. The telehandler did not pierce the plastic of the IBC directly (as was expected) but rather one of the tynes had caught on the underside of the metal base plate, despite numerous controls being in place at time of spill, revealing a previously unreported mechanism for a fluid spill from handling of petroleum hydrocarbons. The diverse investigation team used a root cause analysis (RCA) technique to identify the underlying cause: the inspection process was inadequate with contributing factors of not using a spotter and design of IBC did not anticipate conditions. Engineering controls were put in place as part of the change management process to help prevent spills from occurring from piercing from telehandler tynes on the current project site.  相似文献   
6.
In this paper, the Thyristor-Controlled Series-Compensated (TCSC) devices are located for congestion management in the power system by considering the non-smooth fuel cost function and penalty cost of emission. For this purpose, it is considered that the objective function of the proposed optimal power flow (OPF) problem is minimizing fuel and emission penalty cost of generators. A hybrid method that is the combination of the bacterial foraging (BF) algorithm with Nelder–Mead (NM) method (BF-NM) is employed to solve the OPF problems. The optimal location of the TCSC devices are then determined for congestion management. The size of the TCSC is obtained by using of the BF-NM algorithm to minimize the cost of generation, cost of emission, and cost of TCSC. The simulation results on IEEE 30-bus, modified IEEE 30-bus and IEEE 118-bus test system confirm the efficiency of the proposed method for finding the optimal location of the TCSC with non-smooth non-convex cost function and emission for congestion management in the power system. In addition, the results clearly show that a better solution can be achieved by using the proposed OPF problem in comparison with other intelligence methods.  相似文献   
7.
通过对档案管理中存在的问题进行分析,提出了提高学籍档案管理效率的对策,以期能为中职学籍档案的管理工作提供有益的参考和借鉴。  相似文献   
8.
电网的安全水平主要取决于其使用产品的质量是否过关。如果产品的质量较好,则能建造出优质的电网,电网的安全水平便会随之提高。因此,应加强对产品质量的监督管理,从而提高电网的安全水平。我们可建立质量监督管理系统,及时抽检出质量不过关的产品,从而消除电网运行过程中潜在的安全隐患。  相似文献   
9.
Goat milk has specific chemical composition and physical properties. The purpose of this study was to investigate the change of milk quality and emulsion stability during 60 d frozen storage. Milk sample was taken from three Ettawah Crossedbred goats that were divided into three groups. Samples were frozen and stored for 0, 30 and 60 days. At the end of each storage periode, milk sample was thawed in the refrigerator and analyzed for total number of bacteria, chemical (acidity, pH, free fatty acids), physical (alcohol test, clot on boiling test) quality, and emulsion stability. The microbiological and chemical data were analyzed statistically using one way ANOVA, whereas physical quality and emulsion stabilty were expressed qualitatively. There were no change in the total bacteria, acidity, pH and free fatty acid (FFA) of milk during storage, whereas the assessment by 70% alcohol showed positive since 0 d. Emulsions stability changed after 30 d of storage. While, the clot on boiling (COB) test of milk was positive at 60 d of storage. Recommendation is frozen storage of goat milk should not longer than 30 d.  相似文献   
10.
Cattle access to streams has been linked globally with degradation of stream water quality, driven largely by bank erosion and resultant instream, fine sediment deposition. The majority of evidence on such effects is however based in arid and semiarid regions of the United States and Australia, with few studies relating to cool temperate climates such as Northwest Europe. In this study, “Quorer” resuspendable sediment samples were taken from riffle geomorphic units upstream (control) and at two points downstream (pressure and recovery) of cattle access points in headwater streams in agricultural catchments in Ireland to assess levels of deposited stream sediment. Samples were taken in April/May (2016) prior to the grazing season and in October (2016) at the end of the grazing season. Sites in good‐high ecological status catchments and less than good ecological status catchments were included in the study. Higher levels of sediment were found downstream of cattle access points in both good‐high status and less than good status catchments; however, the impacts of access points were spatially confined to, in most cases, the area immediately downstream of the point of access. There was a strong correlation between deposited sediment mass and organic matter (OM) mass, with levels of OM increasing linearly with deposited sediment mass. Levels of measured sediment were negatively correlated with riparian habitat health (measured using a qualitative habitat assessment). The results of this study highlight the need for measures to prevent cattle access to headwater streams where access points can be many in order to manage local habitat quality and downstream water quality issues.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号