全文获取类型
收费全文 | 41074篇 |
免费 | 994篇 |
国内免费 | 76篇 |
专业分类
电工技术 | 451篇 |
综合类 | 39篇 |
化学工业 | 7948篇 |
金属工艺 | 1015篇 |
机械仪表 | 846篇 |
建筑科学 | 2101篇 |
矿业工程 | 302篇 |
能源动力 | 1176篇 |
轻工业 | 3409篇 |
水利工程 | 401篇 |
石油天然气 | 225篇 |
武器工业 | 3篇 |
无线电 | 2886篇 |
一般工业技术 | 6482篇 |
冶金工业 | 9114篇 |
原子能技术 | 401篇 |
自动化技术 | 5345篇 |
出版年
2022年 | 243篇 |
2021年 | 434篇 |
2020年 | 362篇 |
2019年 | 451篇 |
2018年 | 561篇 |
2017年 | 576篇 |
2016年 | 603篇 |
2015年 | 536篇 |
2014年 | 833篇 |
2013年 | 2469篇 |
2012年 | 1419篇 |
2011年 | 1827篇 |
2010年 | 1410篇 |
2009年 | 1482篇 |
2008年 | 1680篇 |
2007年 | 1705篇 |
2006年 | 1460篇 |
2005年 | 1397篇 |
2004年 | 1215篇 |
2003年 | 1207篇 |
2002年 | 1212篇 |
2001年 | 787篇 |
2000年 | 781篇 |
1999年 | 723篇 |
1998年 | 1269篇 |
1997年 | 991篇 |
1996年 | 946篇 |
1995年 | 818篇 |
1994年 | 764篇 |
1993年 | 773篇 |
1992年 | 591篇 |
1991年 | 419篇 |
1990年 | 551篇 |
1989年 | 543篇 |
1988年 | 489篇 |
1987年 | 507篇 |
1986年 | 457篇 |
1985年 | 618篇 |
1984年 | 601篇 |
1983年 | 526篇 |
1982年 | 533篇 |
1981年 | 510篇 |
1980年 | 432篇 |
1979年 | 442篇 |
1978年 | 414篇 |
1977年 | 428篇 |
1976年 | 475篇 |
1975年 | 375篇 |
1974年 | 304篇 |
1973年 | 334篇 |
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
1.
Thomas S. Lowry John C. Bright Murray E. Close Christina A. Robb Paul A. White Stewart G. Cameron 《国际水资源开发杂志》2003,19(4):579-592
The primary objective of this project is to identify gaps, whether real or perceived, that hinder effective groundwater management in New Zealand. These gaps show as gaps in information, gaps in implementation, gaps in technological and management tools, and gaps in understanding of fundamental processes. The secondary objective is to propose a management strategy to close the identified gaps. Several methods are used to meet these objectives: surveys distributed to selected staff in each regional council; the review of various written reports; the analysis of land-use databases; and private consultation within each regional council. Results show that groundwater management in New Zealand is generally reactionary with the main gaps being in strategic planning and national guidelines. Most gaps appear to be predominantly information and implementation issues. In some cases there are gaps in the understanding of fundamental processes within an aquifer system, including the long-term effects of land-use on groundwater quality. An adaptive management approach is suggested as a means of closing these gaps. 相似文献
2.
3.
John Bensted 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1985,35(4):181-184
Characterisation of raw materials for Portland cement manufacture by use of the methylene blue adsorption method is discussed. The method is shown to be a simple, convenient ‘rule of thumb’ procedure. It provides a guide to the quantity and type of argillaceous minerals present in a given raw material sample. 相似文献
4.
Experiments showing the frequency and amplitude of the flow induced motion of the gate for a 2- and a 4-in. swing check valve have been performed. The gate motion is due to turbulence in approach flow. We have found the dominant turbulent frequency of the approach flow is about half the natural frequency of the valves. The valves appear to be almost critically damped. Because of this, the valves respond almost as they would to a static force of the magnitude characteristic of the turbulent fluctuation in the flow. Both the dimensionless exciting force and the damping ratio have been found to be independent of valve size so the above statements are true for larger valves also. The recommended valve oscillation amplitudes and frequencies are used to calculate the wear at the shaft and at the stop. For an unpegged check valve, such as one of the 10-in. valves which was used at the San Onofre Nuclear Generation Station, it was found that shaft bearing wear would amount to 0.27 in.3/year and stop wear to 0.03 in.3/year. 相似文献
5.
6.
Significant increases in the activity of vanadium(III) amidinate catalysts for ethylene polymerization have been obtained by immobilization on a MgCl2‐based support prepared by reaction of AlEt3 with a MgCl2/ethanol adduct. Catalyst immobilization and activation on this type of support prevents the rapid decay in activity observed under homogeneous polymerization conditions with unsupported catalysts. Stable polymerization activity is also observed with analogous titanium(III) complexes. Polyethylene with narrow molecular weight distribution and spherical particle morphology is obtained without reactor fouling. Copyright © 2005 Society of Chemical Industry 相似文献
7.
Graduates of clinical training programs were surveyed to determine the degree to which they have found various graduate school experiences useful in their professional work. Samples of academic clinical psychologists and practicing clinical psychologists reported time allocation and preference for various professional activities, perceived usefulness of various theoretical orientations, and the influence on their current professional work of 19 different graduate training topics. Results suggest that where differences exist, academic clinical psychologists are generally more satisfied with Boulder-model-inspired scientific training than are clinical practitioners. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
8.
Underflow baffles have gained in popularity over the years as a viable mean to intercept floatables in Combined Sewer Overflows (CSOs). This choice was mainly justified by the extremely low capital cost (CAPEX) and operational cost (OPEX) of this solution, although the efficiency of underflow baffles has never been clearly proven. The only similar application to underflow baffles are scum boards in grit chambers and clarifier. However, the flow conditions at CSOs vary considerably from those in grit chambers and clarifier. For this reason, review of the behavior of floatables in a rapid flow is paramount. Only then can comprehensive design criteria for underflow baffles and overflow chambers be suggested. Pilot scale tests, performed in a 17 metres long basin at various flowrates, had already shown that a critical horizontal velocity for floatables (Vcr) may develop in the overflow chambers. In this follow up study, the fate of intercepted floatables was investigated. It appears from this latest data that permanent capture of floatables decreases rapidly with an increase in the horizontal velocity of the flow, no matter what the baffle depth. Baffle depth increases capture at lower velocities (0.17 m/s) but become irrelevant at higher velocities (0.61 m/s). This data suggests that capture efficiency of existing underflow baffles in overflow chambers can be, at best, very low whenever the horizontal velocity increases above 0.30 m/s or 1 ft/s. 相似文献
9.
10.
Yanqing Ji Hao Ying John Yen Shizhuo Zhu Daniel C. Barth‐Jones Richard E. Miller R. Michael Massanari 《国际智能系统杂志》2007,22(8):827-845
Discovering unknown adverse drug reactions (ADRs) in postmarketing surveillance as early as possible is highly desirable. Nevertheless, current postmarketing surveillance methods largely rely on spontaneous reports that suffer from serious underreporting, latency, and inconsistent reporting. Thus these methods are not ideal for rapidly identifying rare ADRs. The multiagent systems paradigm is an emerging and effective approach to tackling distributed problems, especially when data sources and knowledge are geographically located in different places and coordination and collaboration are necessary for decision making. In this article, we propose an active, multiagent framework for early detection of ADRs by utilizing electronic patient data distributed across many different sources and locations. In this framework, intelligent agents assist a team of experts based on the well‐known human decision‐making model called Recognition‐Primed Decision (RPD). We generalize the RPD model to a fuzzy RPD model and utilize fuzzy logic technology to not only represent, interpret, and compute imprecise and subjective cues that are commonly encountered in the ADR problem but also to retrieve prior experiences by evaluating the extent of matching between the current situation and a past experience. We describe our preliminary multiagent system design and illustrate its potential benefits for assisting expert teams in early detection of previously unknown ADRs. © 2007 Wiley Periodicals, Inc. Int J Int Syst 22: 827–845, 2007. 相似文献