全文获取类型
收费全文 | 556310篇 |
免费 | 45356篇 |
国内免费 | 25480篇 |
专业分类
电工技术 | 33171篇 |
技术理论 | 90篇 |
综合类 | 60738篇 |
化学工业 | 73925篇 |
金属工艺 | 26465篇 |
机械仪表 | 30817篇 |
建筑科学 | 70905篇 |
矿业工程 | 29623篇 |
能源动力 | 18257篇 |
轻工业 | 43556篇 |
水利工程 | 23515篇 |
石油天然气 | 26844篇 |
武器工业 | 6717篇 |
无线电 | 39252篇 |
一般工业技术 | 41864篇 |
冶金工业 | 29905篇 |
原子能技术 | 5011篇 |
自动化技术 | 66491篇 |
出版年
2024年 | 2132篇 |
2023年 | 6508篇 |
2022年 | 12116篇 |
2021年 | 15461篇 |
2020年 | 15708篇 |
2019年 | 12311篇 |
2018年 | 11639篇 |
2017年 | 14346篇 |
2016年 | 16993篇 |
2015年 | 18448篇 |
2014年 | 34913篇 |
2013年 | 30898篇 |
2012年 | 38613篇 |
2011年 | 41344篇 |
2010年 | 31620篇 |
2009年 | 32542篇 |
2008年 | 29991篇 |
2007年 | 37945篇 |
2006年 | 35428篇 |
2005年 | 30850篇 |
2004年 | 26313篇 |
2003年 | 23403篇 |
2002年 | 19304篇 |
2001年 | 16236篇 |
2000年 | 13574篇 |
1999年 | 10834篇 |
1998年 | 8076篇 |
1997年 | 7002篇 |
1996年 | 6060篇 |
1995年 | 5078篇 |
1994年 | 4382篇 |
1993年 | 3228篇 |
1992年 | 2794篇 |
1991年 | 2004篇 |
1990年 | 1724篇 |
1989年 | 1508篇 |
1988年 | 1106篇 |
1987年 | 783篇 |
1986年 | 611篇 |
1985年 | 566篇 |
1984年 | 501篇 |
1983年 | 372篇 |
1982年 | 305篇 |
1981年 | 248篇 |
1980年 | 222篇 |
1979年 | 147篇 |
1978年 | 89篇 |
1977年 | 93篇 |
1976年 | 69篇 |
1975年 | 72篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
M. R. Thompson 《Drug development and industrial pharmacy》2015,41(8):1223-1231
Twin screw granulation (TSG) is a new process of interest to the pharmaceutical community that can continuously wet granulate powders, doing so at lower liquid concentrations and with better product consistency than found by a high shear batch mixer. A considerable body of research has evolved over the short time since this process was introduced but generally with little comparison of results. A certain degree of confidence has been developed through these studies related to how process variables and many attributes of machinery configuration will affect granulation but some major challenges still lay ahead related to scalability, variations in the processing regimes related to degree of channel fill and the impact of wetting and granulation of complex powder formulations. This review examines the current literature for wet granulation processes studied in twin screw extrusion machinery, summarizing the influences of operational and system parameters affecting granule properties as well as strives to provide some practical observations to newly interested users of the technique. 相似文献
22.
23.
文章通过对黑龙江省高效节水现状,存在问题的分析,结合黑龙江省高效节水发展的支撑能力,阐述黑龙江省节水增粮目标、任务及总体布局,为黑龙江省2012—2015年节水增粮实施提供依据。 相似文献
24.
25.
ABSTRACTIn this paper, we review some algebraic control system. Precisely, linear and bilinear systems on Euclidean spaces and invariant and linear systems on Lie groups. The fourth classes of systems have a common issue: to any class, there exists an associated subgroup. From this object, we survey the controllability property. Especially, from those coming from our contribution to the theory. 相似文献
26.
The Vehicle Routing Problem with Simultaneous Pickup and Delivery (VRPSPD) is an extension to the classical Vehicle Routing Problem (VRP), where customers may both receive and send goods simultaneously. The Vehicle Routing Problem with Mixed Pickup and Delivery (VRPMPD) differs from the VRPSPD in that the customers may have either pickup or delivery demand. However, the solution approaches proposed for the VRPSPD can be directly applied to the VRPMPD. In this study, an adaptive local search solution approach is developed for both the VRPSPD and the VRPMPD, which hybridizes a Simulated Annealing inspired algorithm with Variable Neighborhood Descent. The algorithm uses an adaptive threshold function that makes the algorithm self-tuning. The proposed approach is tested on well-known VRPSPD and VRPMPD benchmark instances derived from the literature. The computational results indicate that the proposed algorithm is effective in solving the problems in reasonable computation time. 相似文献
28.
Salman M.A. Salman 《国际水资源开发杂志》2015,31(1):4-16
The United Nations Watercourses Convention entered into force on 17 August 2014, following a long and complex journey that dates back to 1970 when the UN referred the matter to its legal arm, the International Law Commission. This article follows the Convention through that long and turbulent road, examines its main provisions and analyses the reasons for the delay of its entry into force. It concludes by answering the question of why entry into force of the Convention should indeed matter. 相似文献
29.
Health information technology (IT) is a promising way to achieve safer medication management in the delivery of healthcare. However, human factors/ergonomics dictates that in order to make the complex, cognitive work of healthcare delivery safer, health IT must properly support human cognition. This means, for example, that new health IT must reduce, not increase, workload during safety-critical tasks. The present study was the first to quantitatively assess the short- and long-term impact of bar coded medication administration (BCMA) IT on nurses' mental workload as well as on perceived medication safety. One-hundred seventy registered nurses across 3 dissimilar clinical units at an academic, freestanding pediatric hospital in the Midwest US participated in surveys administered before, 3 months after, and 12 months after the hospital implemented BCMA. Nurses rated their external mental workload (interruptions, divided attention, being rushed) and internal mental workload (concentration, mental effort) during medication administration tasks as well as the likelihood of each of three medication safety events: medication administration errors, medication errors on the clinical unit, and clinical unit-level adverse drug events. Clinical unit differences were assessed. Findings generally confirmed the hypothesis that external but not internal mental workload was associated with the perceived likelihood of a medication safety event. Comparisons of mental workload from pre- to post-BCMA revealed statistically significant changes in the critical care unit only. Medication safety appeared to improve over the long term in the hematology/oncology unit only. In the critical care and medical/surgical units, medication safety exhibited short-term improvements that were eliminated over time. Changes in mental workload and medication safety, two classically microergonomic constructs, were deeply embedded in macroergonomic phenomena. These included the fit between the BCMA system and the nature of nursing work, the process of BCMA implementation, and BCMA interactions with concurrent changes occurring in the hospital. Findings raise questions about achieving sustainable performance improvement with health IT as well as the balance between micro- and macroergonomic approaches to studying technology change.Relevance to industryDesigners must consider how technology changes cognitive work, including mental workload. Hospitals and other implementers of technology must ensure that new technology fits its users, their tasks, and the context of use, which may entail tailoring implementation, for example, to specific clinical units. Evaluators must look over time to assess both changes in cognitive work and implementation issues. Healthcare practitioners must also recognize that new technology means a complex transformation to an already complex sociotechnical system, which calls for a macroergonomic approach to design and analysis. 相似文献
30.
《Intermetallics》2015
An equiatomic CoCrFeNiMn high-entropy alloy was synthesized by mechanical alloying (MA) and spark plasma sintering (SPS). During MA, a solid solution with refined microstructure of 10 nm which consists of a FCC phase and a BCC phase was formed. After SPS consolidation, only one FCC phase can be detected in the HEA bulks. The as-sintered bulks exhibit high compressive strength of 1987 MPa. An interesting magnetic transition associated with the structure coarsening and phase transformation was observed during SPS process. 相似文献