全文获取类型
收费全文 | 14663篇 |
免费 | 1434篇 |
国内免费 | 918篇 |
专业分类
电工技术 | 1519篇 |
技术理论 | 7篇 |
综合类 | 1564篇 |
化学工业 | 885篇 |
金属工艺 | 249篇 |
机械仪表 | 1215篇 |
建筑科学 | 1488篇 |
矿业工程 | 428篇 |
能源动力 | 499篇 |
轻工业 | 330篇 |
水利工程 | 287篇 |
石油天然气 | 435篇 |
武器工业 | 133篇 |
无线电 | 1861篇 |
一般工业技术 | 1342篇 |
冶金工业 | 481篇 |
原子能技术 | 57篇 |
自动化技术 | 4235篇 |
出版年
2024年 | 62篇 |
2023年 | 183篇 |
2022年 | 344篇 |
2021年 | 444篇 |
2020年 | 440篇 |
2019年 | 330篇 |
2018年 | 302篇 |
2017年 | 370篇 |
2016年 | 434篇 |
2015年 | 576篇 |
2014年 | 1052篇 |
2013年 | 881篇 |
2012年 | 1084篇 |
2011年 | 1280篇 |
2010年 | 1023篇 |
2009年 | 895篇 |
2008年 | 945篇 |
2007年 | 993篇 |
2006年 | 942篇 |
2005年 | 821篇 |
2004年 | 729篇 |
2003年 | 582篇 |
2002年 | 415篇 |
2001年 | 422篇 |
2000年 | 313篇 |
1999年 | 246篇 |
1998年 | 183篇 |
1997年 | 155篇 |
1996年 | 118篇 |
1995年 | 103篇 |
1994年 | 64篇 |
1993年 | 63篇 |
1992年 | 47篇 |
1991年 | 33篇 |
1990年 | 27篇 |
1989年 | 19篇 |
1988年 | 25篇 |
1987年 | 7篇 |
1986年 | 10篇 |
1985年 | 7篇 |
1984年 | 9篇 |
1983年 | 7篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1975年 | 3篇 |
1964年 | 3篇 |
1957年 | 1篇 |
1956年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
The requirements on an object-oriented DBMS for management of information in a large, complex enterprise are presented. These requirements aid in the achievement of an environment characterized by data sharing, open architectures, application and data portability, and assurance of data integrity. They were defined from the point of view of a user of the DBMS; therefore they describe the expected functionality of the DBMS and do not specify the method of implementation to achieve this functionality. They encompass requirements on the data model, query and data manipulation languages, the system architecure, interfaces to the system, change management, and transaction management. 相似文献
3.
Guo Ya-kun Wen Xian-yun Institute of Hydraulic Research Chengdu University of Science Technology Chengdu P.R.China 《水动力学研究与进展(B辑)》1993,(1)
In this paper,using complex functional theory,the authors turn the potentialflow around the surface irregularities in a pressure conduit and semi-infinite platforms intoDirichlet problem.Based on Schwarz formula and by the application of Plemelj's formula,theauthors change the problem into the integration of a Cauchy boundary integral equation in theflow plane through the substitution of variables.Using numerical integration,the authors obtainthe velocity distribution and pressure coefficient along surface irregularities and platforms.Thephysical concept of this method is clear,the convergent speed is rapid and the computative effi-ciency is high.The calculated values agree well with the measured results.It is an effective andsimple method in solving potential flow. 相似文献
4.
The precise integration and differential quadrature methods are two new unconditionally stable numerical schemes to approximate
time derivative with more than the second order accuracy. Recent studies showed that compared with the Houbolt and Newmark
methods, they produced more accurate solutions with large time step for the problems where response is primarily dominated
by low and intermediate frequency modes. This paper aims to investigate these time schemes in the context of the dual reciprocity
BEM (DRBEM) formulation of various shock-excited scalar elastic wave problems, where high modes have important affect on traction
response. The Houbolt method was widely recommended in many literatures for such DRBEM dynamic formulations. However, this
study found that the damped Newmark algorithm was the most efficient and accurate for impact traction analysis in conjunction
with the DRBEM. The precise integration and differential quadrature methods are shown inapplicable for such shock-excited
problems due to the absence of numerical damping. On the other hand, we also found that to achieve the same order of accuracy,
the differential quadrature method required much less computing effort than the precise integration method due to the use
of the Bartels–Stewart algorithm solving the resulting Lyapunov matrix analogization equation.
Received 6 November 2000 相似文献
5.
An integrated process based on simultaneous solid-liquid extraction and liquid membrane separation is proposed for recovery and isolation of valuable species from botanicals. This integration provides complete exhausting of the solid material even in the case of very low solubility of the specified solute in the extracting solvent. Selectivity of the liquid membrane ensures a preferential transport of the desired solute from the native extract into the strip solution, while the other co-extracted species remain predominantly in the native extract. 相似文献
6.
Kosuke Kurokawa 《Electrical Engineering in Japan》1993,113(4):54-65
Solar radiation has an irregularly varying factor due to a basic day and night cycle and climatic conditions. For such conditions a data sampling interval is important to ensure the accuracy of energy monitoring in a photovoltaic system. While treating a system monitoring equipment as a black box. the author has developed the method of calibrating an energy-integrating function. At first for various input waveforms, the relationship between sampling intervals and quasi-integration outputs have been examined by trapezoidal rule. In the numerical simulation the phases of the sampling clock also are considered Then it is concluded that a sampling interval can be inspected through outside observation only by using a rectangular single pulse. By applying the pulse to the energy-integrating process, two kinds of integrated outputs can be obtained for different sampling phases. The calculated difference between both outputs can uniquely give the sampling interval being inspected. Conditions to ensure measuring accuracy are discussed and the validity of this method has been demonstrated experimentally. Practical calibrating procedures also are proposed for the integrating function of PV system monitoring. 相似文献
7.
罗生鹏 《硫磷设计与粉体工程》2004,(2):42-44
由于建筑工程施工的单件性、复杂性,在工程项目实施过程中贯标工作与工程项目管理工作通常不太融合,有时甚至形成“两层皮”现象。因此,针对这一现象,在承建410t/h锅炉工程中,借贯彻2000版ISO9001标准的有力时机,进行了工程项目管理与贯标工作融合性的探索与实践,取得了较好的效果。 相似文献
8.
吴建功 《电子制作.电脑维护与应用》2014,(18)
经过60年的发展,陕西煤炭技工院校形成了以服务煤业为特色的专业结构和办学模式,为祖国煤炭发展做出了不可替代的贡献。近年来,由于煤炭市场遇冷,行业技校吸引力持续减弱,如何走出困境,重铸辉煌,作者从整合职教资源,调整管理职能,转换办学模式的角度进行了分析思考,或许能给陕煤技校改革发展提供一些有益参考。 相似文献
9.
本文主要根据大多数企业存在各种软件各自独立运行,各软件之间数据不能相互共享,一些旧软件或不适用的软件与目前主流操作系统不兼容等问题,分析问题并用接口和整合方法解决,此平台利用云计算技术,解决大多数企业建设信息平台投资大的问题,同时方便企业使用和维护. 相似文献
10.
Yoshitsugu Kosugi Tsutomu Kunieda Naoki Azuma 《Journal of the American Oil Chemists' Society》1994,71(4):445-448
Rice bran oil containing 30–50% free fatty acid was continually converted to an oil containing more than 75% of triacylglycerol
(TG) by means of immobilized lipase. The reaction was carried out at 60°C for 24 h with dehydration and reactant mixing by
dry nitrogen flow under a positive nitrogen atmosphere. Enzymatic TG synthesis with evaporation by heating was not suitable
because of the increasing peroxide value of the oil.
Part of this article was presented at the annual meeting of the Japan Oil Chemists' Society at Sendai, Japan, October, 16,
1990. 相似文献