全文获取类型
收费全文 | 31033篇 |
免费 | 2828篇 |
国内免费 | 1378篇 |
专业分类
电工技术 | 1722篇 |
技术理论 | 3篇 |
综合类 | 2901篇 |
化学工业 | 2505篇 |
金属工艺 | 1307篇 |
机械仪表 | 1099篇 |
建筑科学 | 1788篇 |
矿业工程 | 635篇 |
能源动力 | 456篇 |
轻工业 | 5067篇 |
水利工程 | 529篇 |
石油天然气 | 1105篇 |
武器工业 | 274篇 |
无线电 | 3962篇 |
一般工业技术 | 2017篇 |
冶金工业 | 1518篇 |
原子能技术 | 102篇 |
自动化技术 | 8249篇 |
出版年
2025年 | 227篇 |
2024年 | 570篇 |
2023年 | 579篇 |
2022年 | 779篇 |
2021年 | 864篇 |
2020年 | 1118篇 |
2019年 | 889篇 |
2018年 | 879篇 |
2017年 | 945篇 |
2016年 | 933篇 |
2015年 | 1108篇 |
2014年 | 1741篇 |
2013年 | 1849篇 |
2012年 | 2127篇 |
2011年 | 2216篇 |
2010年 | 1744篇 |
2009年 | 1807篇 |
2008年 | 1844篇 |
2007年 | 2128篇 |
2006年 | 1862篇 |
2005年 | 1736篇 |
2004年 | 1419篇 |
2003年 | 1140篇 |
2002年 | 919篇 |
2001年 | 728篇 |
2000年 | 645篇 |
1999年 | 473篇 |
1998年 | 334篇 |
1997年 | 307篇 |
1996年 | 273篇 |
1995年 | 211篇 |
1994年 | 203篇 |
1993年 | 123篇 |
1992年 | 107篇 |
1991年 | 77篇 |
1990年 | 66篇 |
1989年 | 49篇 |
1988年 | 37篇 |
1987年 | 31篇 |
1986年 | 28篇 |
1985年 | 24篇 |
1984年 | 20篇 |
1983年 | 9篇 |
1982年 | 13篇 |
1981年 | 10篇 |
1980年 | 7篇 |
1979年 | 6篇 |
1956年 | 3篇 |
1955年 | 3篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
Buffalo milk Cheddar cheese samples of different ages were analysed for compositional attributes (CA), ripening indices (RI) and Instron Textural Profile (ITP). All samples were compositionally alike, except for pH and salt-in-moisture (SM) contents. RI showed significant variations. CA and RI showed highly significant correlations within themselves and with each other, except for moisture with pH, SM with moisture, MNFS, Fat and FDM and Fat with MNFS. The ITPs of cheeses showed significant variations and had highly significant intercorrelations indicating their interdependence. CA (except moisture and MNFS) and RI showed a highly significant correlationship with ITPs. Moisture content showed a highly significant correlationship with all ITPs, except cohesiveness and springiness, where it was significant. MNFS content showed significant correlations only with hardness and brittleness. Stepwise regression analysis revealed that MI was the most predominant factor influencing cheese texture, followed by pH, SM, FDM and TVFA. Knowing Ca and RI, the textural properties of cheeses can be forecast through mathematical equations. Similarly the age of cheese can also be predicted if RI and/or textural properties are known. 相似文献
3.
Bhupesh C. Roy Motonobu Goto & Tsutomu Hirose 《International Journal of Food Science & Technology》1996,31(2):137-141
Tomato seed oil was extracted with supercritical carbon dioxide in a semibatch-flow extractor within the temperature range 313–343 K and the pressure range 10.8–24.5MPa. The extraction rates increased with pressure, but decreased with temperature increase because of the variation in solvent density and resultant differences in oil solubility. The fatty acid composition of the extracted oil was similar to that of soybean oil. 相似文献
4.
5.
对高校图书馆参考咨询服务的探讨 总被引:2,自引:0,他引:2
面对现代信息时代的挑战,高校图书馆参考咨询服务进行着深刻的变革,其系统化、网络化、合作化、社会化、高效化是这种变革的集中体现。 相似文献
6.
7.
It has recently been shown that authenticated Byzantine agreement,
in which more than a third of the parties are corrupted, cannot be
securely realized under concurrent or parallel (stateless)
composition. This result puts into question any usage of
authenticated Byzantine agreement in a setting where many
executions take place. In particular, this is true for the whole
body of work of secure multi-party protocols in the case that a
third or more of the parties are corrupted. This is because these
protocols strongly rely on the extensive use of a broadcast
channel, which is in turn realized using authenticated Byzantine
agreement. We remark that it was accepted folklore that the use of
a broadcast channel (or authenticated Byzantine agreement) is
actually essential for achieving meaningful secure multi-party
computation whenever a third or more of the parties are corrupted.
In this paper we show that this folklore is false. We present a
mild relaxation of the definition of secure computation allowing
abort. Our new definition captures all the central security issues
of secure computation, including privacy, correctness and
independence of inputs. However, the novelty of the definition is
in decoupling the issue of agreement from these issues. We
then show that this relaxation suffices for achieving secure
computation in a point-to-point network. That is, we show that
secure multi-party computation for this definition can be achieved
for any number of corrupted parties and without a
broadcast channel (or trusted pre-processing phase as required for
running authenticated Byzantine agreement). Furthermore, this is
achieved by just replacing the broadcast channel in known
protocols with a very simple and efficient echo-broadcast
protocol. An important corollary of our result is the ability to
obtain multi-party protocols that remain secure under composition,
without assuming a broadcast channel. 相似文献
8.
The broadband integrated services digital networks (B-ISDN) based on asynchronous transfer mode (ATM) technology can support
a wide range of applications such as voice, video, still images, and data. Compression techniques increase the effective bandwidth
utilization, but the bursty and asynchronous nature of the traffic can still lead to congestion in the network, and degradation
of image quality and quality of service (QOS). Some of the features to provide better coding schemes for ATM networks are
layered coding, resynchronization, buffering, interleaved schemes, constrained bit rate due to buffers, encapsulation with
the RTP or AAL1 for clock recovery, lapped transforms, motion compensation, and optimal bit allocation for coders based on
wavelet transforms. We review various techniques forimage and video coding such as transforms, motion compensation, vector
quantization, and subband coding. We outline the impact of the cell loss ratio (CLR), delay and cell delay variation (CDV)
on video coding: blocking effects, loss of frame synchronization, motion vectors, and vector quantization codewords. The open
problems include tuning coding parameters to the available QOS provided by the network. 相似文献
9.
Service life planning comprises a model for the determination of a reasonable expected service life for buildings and components, and it establishes a routine for the assessment of design alternatives. A design option is considered reasonable when it meets or exceeds performance requirements over time that have been drawn up specifically for the specific project. Due to this assessment reference, there is a very evident link to the concept of performance-based building. Any stakeholder involved in the value chain or in the design process of the building, as well as regulators and building users, can express performance requirements. Identified requirements, both in relevance and in quality, will vary with the stakeholder and his/her perspective of interest. As building sector manufacturers develop most products with reference to standards rather than with reference to specific requirements, there is no direct link from user requirements to the product design. Instead, the building designer has the responsibility to ensure performance requirements are met by the performance of products integrated into the design. As these design decisions also have to be made at the material and component level, a performance-based building would benefit from an established rationale that enables the communication of performance requirements across the relevant system levels in the relevant design processes. A path for the connection of the established concepts of service life planning and performance-based building is presented. The aim is to identify key elements that need to be developed for the successful linkage of performance-based building with service life planning. 相似文献
10.