全文获取类型
收费全文 | 86437篇 |
免费 | 6307篇 |
国内免费 | 2930篇 |
学科分类
工业技术 | 95674篇 |
出版年
2024年 | 242篇 |
2023年 | 1269篇 |
2022年 | 1921篇 |
2021年 | 3057篇 |
2020年 | 2325篇 |
2019年 | 2009篇 |
2018年 | 2244篇 |
2017年 | 2495篇 |
2016年 | 2341篇 |
2015年 | 2964篇 |
2014年 | 4039篇 |
2013年 | 5098篇 |
2012年 | 5295篇 |
2011年 | 5583篇 |
2010年 | 4966篇 |
2009年 | 4745篇 |
2008年 | 4524篇 |
2007年 | 4443篇 |
2006年 | 4716篇 |
2005年 | 4155篇 |
2004年 | 2803篇 |
2003年 | 2518篇 |
2002年 | 2216篇 |
2001年 | 2039篇 |
2000年 | 2302篇 |
1999年 | 2572篇 |
1998年 | 2391篇 |
1997年 | 1887篇 |
1996年 | 1749篇 |
1995年 | 1451篇 |
1994年 | 1228篇 |
1993年 | 889篇 |
1992年 | 659篇 |
1991年 | 546篇 |
1990年 | 408篇 |
1989年 | 369篇 |
1988年 | 314篇 |
1987年 | 171篇 |
1986年 | 155篇 |
1985年 | 105篇 |
1984年 | 92篇 |
1983年 | 60篇 |
1982年 | 57篇 |
1981年 | 52篇 |
1980年 | 37篇 |
1979年 | 32篇 |
1978年 | 13篇 |
1977年 | 33篇 |
1976年 | 16篇 |
1975年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
991.
992.
基于RFID的虚拟标签算法研究与改进 总被引:3,自引:2,他引:1
针对室内定位算法VIRE的定位精度,特别是邻近边界目标的定位精度较低的问题,以RFID标签定位为研究基础,从改变VIRE算法中虚拟标签的插值方式和在边界上加入虚拟标签两个方面进行研究和改进。使用拉格朗日插值代替VIRE算法中的线性插值方式,使虚拟标签的数据更加接近实际环境值;在边界上加入虚拟参考标签能增加已知标签数,防止在计算待定位标签坐标时引入误差标签。实验结果表明,标签定位精度有了明显提高,整体能提高了35%,邻近边界标签定位精度提高较大,可达到50%以上。 相似文献
993.
994.
995.
It is well established in the psychology literature that personality predicts performance to some degree. However, personality neither solely nor directly predicts outcomes. Rather, performance and outcomes unfold through context-specific mediating constructs. This study identified two constructs that mediate the relationship between proactivity and perceived control of time in e-mail use and tested the model with data from 251 knowledge workers. The results show that proactivity predicts the perceived control of time in e-mail use through both e-mail-specific time management behavior and e-mail self-efficacy. Further, greater e-mail self-efficacy leads to improved e-mail-specific time management behavior. 相似文献
996.
Drawing upon a relationship quality framework, this study identifies how satisfaction, trust and different styles of handling conflict influence online buyers’ participation intentions in reputation systems associated with a C2C online shopping platform. Furthermore, we investigate how these effects are moderated by social conformity and the perceived value of knowledge. The results of a survey of 269 online buyers indicate that satisfaction, trust and an accommodating conflict handling style positively impact the intention to submit positive ratings, whereas an avoiding conflict handling style negatively affects the intention to submit positive ratings. Implications and suggestions for future research are provided. 相似文献
997.
The purpose of this study was to characterize the mechanical behavior of asphalt modified by styrene–butadiene–styrene (SBS) and sulfur. Viscosity, microscopy, and rheological tests were conducted to understand the engineering properties of the polymer‐modified asphalt (PMA). Without the addition of sulfur, the polymer‐modified asphalt was microheterogeneous and was made up of two distinct finely interlocked phases, especially at high SBS concentrations. After the addition of sulfur, the PMA was observed to have smaller asphalt domains and a fairly homogeneous dispersion of the asphalt in the SBS matrix. The compatibility between polymer and asphalt produced an elastic network into the asphalt. The addition of sulfur resulted in an excellent elastic system and substantially increased the rheological properties of the PMA. Because of the colloidal nature of asphalt cements, their engineering properties were greatly improved because of the reinforcement of the SBS polymer and the physical‐chemical interaction between SBS and asphalt. The difference in the softening point between the top and bottom layers decreased significantly, and elastic recovery increased when was sulfur was present. A viscoelastic model was examined and shown to be appropriate for predicting the rheological properties ofthe asphalt–SBS blend mixed with sulfur. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2817–2825, 2007 相似文献
998.
One of the fundamental tasks of targeted marketing is to elicit associations between customers and products. Based on the results from information retrieval and utility theory, this article proposes a unified framework of targeted marketing. The customer judgments of products are formally described by preference relations and the connections of customers and products are quantitatively measured by market value functions. Two marketing strategies, known as the customer‐oriented and product‐oriented marketing strategies, are investigated. Four marketing models are introduced and examined. They represent, respectively, the relationships between a group of customers and a group of products, between a group of customers and a single product, between a single customer and a group of products, and between a single customer and a single product. Linear and bilinear market value functions are suggested and studied. The required parameters of a market value function can be estimated by exploring three types of information, namely, customer profiles, product profiles, and transaction data. Experiments on a real‐world data set are performed to demonstrate the effectiveness of the proposed framework. 相似文献
999.
The paper is to introduce a new systematic method that can produce lower bounds for eigenvalues. The main idea is to use nonconforming finite element methods. The conclusion is that if local approximation properties of nonconforming finite element spaces are better than total errors (sums of global approximation errors and consistency errors) of nonconforming finite element methods, corresponding methods will produce lower bounds for eigenvalues. More precisely, under three conditions on continuity and approximation properties of nonconforming finite element spaces we analyze abstract error estimates of approximate eigenvalues and eigenfunctions. Subsequently, we propose one more condition and prove that it is sufficient to guarantee nonconforming finite element methods to produce lower bounds for eigenvalues of symmetric elliptic operators. We show that this condition hold for most low-order nonconforming finite elements in literature. In addition, this condition provides a guidance to modify known nonconforming elements in literature and to propose new nonconforming elements. In fact, we enrich locally the Crouzeix-Raviart element such that the new element satisfies the condition; we also propose a new nonconforming element for second order elliptic operators and prove that it will yield lower bounds for eigenvalues. Finally, we prove the saturation condition for most nonconforming elements. 相似文献
1000.
Meetings play an important role in our daily lives. Verbal communication and social relationship development are the primary activities of meeting attendees. In this paper, we propose a meeting support system, namely SmartMic, to enhance user experiences and facilitate social interactions during meetings. SmartMic uses smartphone and readily available facilities in common meeting venues to support easy speaking and establishing new social connections. Meeting attendees in the system speak through smartphone instead of microphone and contact with each other conveniently. Preliminary experiment results show that SmartMic can facilitate the social interaction among attendees and promote the meeting productivity efficiently. 相似文献