全文获取类型
收费全文 | 330950篇 |
免费 | 32023篇 |
国内免费 | 21955篇 |
专业分类
电工技术 | 21107篇 |
技术理论 | 57篇 |
综合类 | 45643篇 |
化学工业 | 29690篇 |
金属工艺 | 10589篇 |
机械仪表 | 18776篇 |
建筑科学 | 40363篇 |
矿业工程 | 16271篇 |
能源动力 | 8367篇 |
轻工业 | 15920篇 |
水利工程 | 15069篇 |
石油天然气 | 11940篇 |
武器工业 | 3725篇 |
无线电 | 32084篇 |
一般工业技术 | 23333篇 |
冶金工业 | 17819篇 |
原子能技术 | 2854篇 |
自动化技术 | 71321篇 |
出版年
2024年 | 1299篇 |
2023年 | 3695篇 |
2022年 | 6898篇 |
2021年 | 8326篇 |
2020年 | 8670篇 |
2019年 | 7115篇 |
2018年 | 6658篇 |
2017年 | 8246篇 |
2016年 | 9656篇 |
2015年 | 10982篇 |
2014年 | 19436篇 |
2013年 | 17736篇 |
2012年 | 23059篇 |
2011年 | 24239篇 |
2010年 | 19476篇 |
2009年 | 20337篇 |
2008年 | 19658篇 |
2007年 | 24460篇 |
2006年 | 22753篇 |
2005年 | 19935篇 |
2004年 | 16892篇 |
2003年 | 15020篇 |
2002年 | 12114篇 |
2001年 | 10172篇 |
2000年 | 8429篇 |
1999年 | 6742篇 |
1998年 | 5077篇 |
1997年 | 4456篇 |
1996年 | 4053篇 |
1995年 | 3398篇 |
1994年 | 3016篇 |
1993年 | 2278篇 |
1992年 | 1988篇 |
1991年 | 1476篇 |
1990年 | 1292篇 |
1989年 | 1135篇 |
1988年 | 917篇 |
1987年 | 624篇 |
1986年 | 485篇 |
1985年 | 415篇 |
1984年 | 394篇 |
1983年 | 298篇 |
1982年 | 250篇 |
1981年 | 191篇 |
1980年 | 147篇 |
1979年 | 127篇 |
1978年 | 69篇 |
1977年 | 80篇 |
1976年 | 59篇 |
1975年 | 61篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Colin Fyfe 《Data mining and knowledge discovery》2007,14(2):207-224
We review a new form of self-organizing map which is based on a nonlinear projection of latent points into data space, identical
to that performed in the Generative Topographic Mapping (GTM) [Bishop et al. (1997) Neurl Comput 10(1): 215–234]. But whereas
the GTM is an extension of a mixture of experts, our new model is an extension of a product of experts [Hinton (2000) Technical
report GCNU TR 2000-004, Gatsby Computational Neuroscience Unit, University College, London]. We show visualisation results
on some real data sets and compare with the GTM. We then introduce a second mapping based on harmonic averages and show that
it too creates a topographic mapping of the data. We compare these mappings on real and artificial data sets.
Responsible editor: Soumen Chakrabarti. 相似文献
992.
Environment as a first class abstraction in multiagent systems 总被引:2,自引:1,他引:1
The current practice in multiagent systems typically associates the environment with resources that are external to agents and their communication infrastructure. Advanced uses of the environment include infrastructures for indirect coordination, such as digital pheromones, or support for governed interaction in electronic institutions. Yet, in general, the notion of environment is not well defined. Functionalities of the environment are often dealt with implicitly or in an ad hoc manner. This is not only poor engineering practice, it also hinders engineers to exploit the full potential of the environment in multiagent systems. In this paper, we put forward the environment as an explicit part of multiagent systems.We give a definition stating that the environment in a multiagent system is a first-class abstraction with dual roles: (1) the environment provides the surrounding conditions for agents to exist, which implies that the environment is an essential part of every multiagent system, and (2) the environment provides an exploitable design abstraction for building multiagent system applications. We discuss the responsibilities of such an environment in multiagent systems and we present a reference model for the environment that can serve as a basis for environment engineering. To illustrate the power of the environment as a design abstraction, we show how the environment is successfully exploited in a real world application. Considering the environment as a first-class abstraction in multiagent systems opens up new horizons for research and development in multiagent systems. 相似文献
993.
994.
实验考察了8种市售水溶性破乳荆对长庆油田陕北区有代表性的宝塔区、安塞和子长原油(均为低硫中间基-石蜡基原油)的脱水效果(加量100mg/L,脱水温度55℃,时间3h)。目前长庆采油一厂使用的YT-100和延炼集团使用的GT-940对这3种原油的脱水效果均较好,但对子长原油的脱水率不高,分别为69.7%和58.9%。在由所选性能较好的破乳刺组成的4种二元复配物中,GT-940 HQ96-1对3种原油的脱水效果均高于单剂,最佳配比分别为4:1,4:1,3:2;其余3种复配物则对原油有选择性,其中GT-940 YT-100相近(97.5%);YT-100 HQ96-1仅能改善子长原油的脱水效果,配比为4:1时脱水率最高(76.4%);SP-169 HQ96-1仅能改善宝塔区原油的脱水效果.配比3:2和2:3时脱水率最高(92.9%)。表5参6。 相似文献
995.
A globally convergent algorithm for transportation continuous network design problem 总被引:2,自引:0,他引:2
The continuous network design problem (CNDP) is characterized by a bilevel programming model, in which the upper level problem
is generally to minimize the total system cost under limited expenditure, while at the lower level the network users make
choices with regard to route conditions following the user equilibrium principle. In this paper, the bilevel programming model
for CNDP is transformed into a single level convex programming problem by virtue of an optimal-value function tool and the
relationship between System Optimum (SO) and User Equilibrium (UE). By exploring the inherent nature of the CNDP, the optimal-value
function for the lower level user equilibrium problem is proved to be continuously differentiable and its derivative in link
capacity enhancement can be obtained efficiently by implementing user equilibrium assignment subroutine. However, the reaction
(or response) function between the upper and lower level problem is implicit and its gradient is difficult to obtain. Although,
here we approximately express the gradient with the difference concept at each iteration, based on the method of successive
averages (MSA), we propose a globally convergent algorithm to solve the single level convex programming problem. Comparing
with widely used heuristic algorithms, such as sensitivity analysis based (SAB) method, the proposed algorithm needs not strong
hypothesis conditions and complex computation for the inverse matrix. Finally, a numerical example is presented to compare
the proposed method with some existing algorithms. 相似文献
996.
In long-term memory, negative information is better remembered than neutral information. Differences in processes important to working memory may contribute to this emotional memory enhancement. To examine the effect that the emotional content of stimuli has on working memory performance, the authors asked participants to perform working memory tasks with negative and neutral stimuli. Task accuracy was unaffected by the emotional content of the stimuli. Reaction times also did not differ for negative relative to neutral words, but on an n-back task using faces, participants were slower to respond to fearful faces than to neutral faces. These results suggest that although emotional content does not have a robust effect on working memory, in some instances emotional salience can impede working memory performance. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
997.
通过对多孔粒状铵油炸药质量影响因素的分析,结合乌海矿业公司爆破的特点,提出了保证炸药加工质量的合理参数。 相似文献
998.
沈建国 《石油地球物理勘探》2003,38(1):44-47
用穿透方法测量岩心或固体的声速时,从测量波形中确定纵波(或横波)的到达时刻(或称初始点)比较困难,当声波的频率比较低时,其误差对测量结果影响比较大。本文用相位分析的方法研究了初始点的选择问题。首先,用各向同性较强、均匀的汉白玉制作标准件,测量其不同传播距离的波形,再用相位补偿的方法得到其传播速度;其次,利用传播速度,可从不同距离的测量波形中确定初始点及其对应的测量系统的时间延迟常数;最后,确定波形的其他位置为初始点时对应的时间延迟常数,因此,我们可以根据实际测量波形的特点选择最佳的初始点,利用其对应的时间延迟常数得到比较精确的声速。模型测量结果表明,初始点位置不同,其对应的测量系统的时间延迟常数也不同,也即测量系统的时间延迟常数是与初始点的选择相对应的。 相似文献
999.
The present study examined whether siblings experience marital conflict differently and whether such differences, if present, were associated with differences in their adjustment. Self-report data about marital conflict, children's depressed mood, behavioral conduct, and externalizing problems were obtained from 122 sibling pairs (mean ages = 10 and 12 years) and their parents. Results indicated that siblings were significantly different in exposure to and appraisals of marital conflict. Differences in siblings' exposure to marital conflict were significantly correlated with differences in their depressed mood, behavioral conduct, and externalizing problems. Differences in siblings' feelings of self-blame for marital conflict were significantly correlated with differences in their depressed mood and behavioral conduct. Children who experienced more marital conflict than their siblings had more adjustment problems than their siblings. These results highlight the importance of studying siblings' unique experiences of marital conflict to better understand its impact on children's adjustment. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
1000.