全文获取类型
收费全文 | 263091篇 |
免费 | 3271篇 |
国内免费 | 824篇 |
专业分类
电工技术 | 5161篇 |
综合类 | 335篇 |
化学工业 | 37688篇 |
金属工艺 | 10302篇 |
机械仪表 | 8532篇 |
建筑科学 | 6206篇 |
矿业工程 | 1098篇 |
能源动力 | 6437篇 |
轻工业 | 23125篇 |
水利工程 | 2581篇 |
石油天然气 | 3913篇 |
武器工业 | 68篇 |
无线电 | 34894篇 |
一般工业技术 | 50541篇 |
冶金工业 | 47612篇 |
原子能技术 | 5445篇 |
自动化技术 | 23248篇 |
出版年
2021年 | 2077篇 |
2019年 | 2053篇 |
2018年 | 3508篇 |
2017年 | 3559篇 |
2016年 | 3773篇 |
2015年 | 2355篇 |
2014年 | 4092篇 |
2013年 | 11455篇 |
2012年 | 6645篇 |
2011年 | 9000篇 |
2010年 | 7064篇 |
2009年 | 7949篇 |
2008年 | 8806篇 |
2007年 | 8739篇 |
2006年 | 7888篇 |
2005年 | 7232篇 |
2004年 | 6951篇 |
2003年 | 6807篇 |
2002年 | 6434篇 |
2001年 | 6522篇 |
2000年 | 6233篇 |
1999年 | 6321篇 |
1998年 | 14443篇 |
1997年 | 10401篇 |
1996年 | 8212篇 |
1995年 | 6470篇 |
1994年 | 5773篇 |
1993年 | 5653篇 |
1992年 | 4581篇 |
1991年 | 4229篇 |
1990年 | 4086篇 |
1989年 | 3811篇 |
1988年 | 3649篇 |
1987年 | 3214篇 |
1986年 | 3098篇 |
1985年 | 3649篇 |
1984年 | 3430篇 |
1983年 | 3064篇 |
1982年 | 2877篇 |
1981年 | 2979篇 |
1980年 | 2795篇 |
1979年 | 2671篇 |
1978年 | 2535篇 |
1977年 | 2996篇 |
1976年 | 3623篇 |
1975年 | 2339篇 |
1974年 | 2333篇 |
1973年 | 2335篇 |
1972年 | 1861篇 |
1971年 | 1760篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
It is established that the capillary rise of a liquid has an oscillatory character, in contrast to the commonly accepted opinion that a vertical capillary is filled at a monotonically varying velocity. The value of the tangential shear stress arising in an ascending liquid is evaluated for ethyl alcohol and distilled water. 相似文献
62.
63.
This paper deals with accurate recipe implementation for abnormal condition management in a batch process using a case‐based reasoning (CBR) approach. A set of new problems can be solved by reusing proven process solutions. The proposed system integrates quantitative and qualitative parameters for adaptation of cases. A novel methodology to generate accurate recipes and to adapt to the processes is introduced during normal and abnormal conditions. In particular, the differences between current conditions and the references (recipes) should be managed to prevent any hazardous conditions arising. The processes are evaluated using their similarity to the past cases. This intelligent approach distinguishes plausible cases, generates accurate recipes, and adapts to new situations. The aim is to use the offline historical process data and safety related information in order to propose changes and adjustments in the processes. 相似文献
64.
65.
A program called GELYMAC takes data on the distances migrated by DNA fragments in a one-dimensional electrophoretic gel and, using a cubic-spline best-fit of marker fragment distance migrated versus molecular size, calculates the molecular sizes of the fragments. Written in the Rascal (Real-time Pascal) programming language, the program runs on the Macintosh family of microcomputers. Rapid entry of marker and experimental fragment migration data is afforded using a scroll bar system adjacent to a graphic representation of a gel. Output includes tabular listing of the data, graphic cartoons of the gel, and the fragment locations and molecular sizes for individual gel lanes, and the calibration curve used in data computations. 相似文献
66.
67.
68.
69.
70.
Faulkner D.W. Payne D.B. Stern J.R. Ballance J.W. 《Lightwave Technology, Journal of》1989,7(11):1741-1751
Some of the options for optical technology within the local loop environment are examined. In particular, passive shared access networks have been considered in some detail. These networks show great promise for delivering existing telephone services to small to medium business customers (4-30 lines) economically by the early 1990s. Extending fiber to the home will also be possible by virtue of a similar passive network infrastructure for customers requiring new broadband services beyond the single telephone line. For one-line plain old telephone service (POTS) customers, an intermediate approach of terminating the fiber network at the final network distribution point, with copper retained for the final leg, may be used prior to the provision of broadband services. A key feature of the passive optical network architecture is the use of wavelength-division multiplexing (WDM) as an upgrade strategy, allowing graceful upgrading from telephone services to multichannel high-definition television (HDTV) on gigabit/second bearers and full two-way switched broadband services employing wavelength routing across the network 相似文献