全文获取类型
收费全文 | 15146篇 |
免费 | 890篇 |
国内免费 | 813篇 |
专业分类
电工技术 | 345篇 |
综合类 | 898篇 |
化学工业 | 1023篇 |
金属工艺 | 814篇 |
机械仪表 | 1565篇 |
建筑科学 | 456篇 |
矿业工程 | 225篇 |
能源动力 | 318篇 |
轻工业 | 1149篇 |
水利工程 | 183篇 |
石油天然气 | 1370篇 |
武器工业 | 101篇 |
无线电 | 1372篇 |
一般工业技术 | 808篇 |
冶金工业 | 488篇 |
原子能技术 | 202篇 |
自动化技术 | 5532篇 |
出版年
2024年 | 37篇 |
2023年 | 89篇 |
2022年 | 256篇 |
2021年 | 308篇 |
2020年 | 286篇 |
2019年 | 289篇 |
2018年 | 254篇 |
2017年 | 369篇 |
2016年 | 432篇 |
2015年 | 459篇 |
2014年 | 706篇 |
2013年 | 751篇 |
2012年 | 874篇 |
2011年 | 1122篇 |
2010年 | 777篇 |
2009年 | 764篇 |
2008年 | 831篇 |
2007年 | 1012篇 |
2006年 | 972篇 |
2005年 | 944篇 |
2004年 | 811篇 |
2003年 | 831篇 |
2002年 | 651篇 |
2001年 | 492篇 |
2000年 | 463篇 |
1999年 | 375篇 |
1998年 | 304篇 |
1997年 | 222篇 |
1996年 | 219篇 |
1995年 | 175篇 |
1994年 | 137篇 |
1993年 | 132篇 |
1992年 | 91篇 |
1991年 | 65篇 |
1990年 | 52篇 |
1989年 | 41篇 |
1988年 | 37篇 |
1987年 | 29篇 |
1986年 | 21篇 |
1985年 | 25篇 |
1984年 | 22篇 |
1983年 | 30篇 |
1982年 | 18篇 |
1981年 | 16篇 |
1980年 | 5篇 |
1979年 | 9篇 |
1978年 | 11篇 |
1977年 | 5篇 |
1976年 | 8篇 |
1962年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Simonetta Balsamo Vittoria De Nitto Person Paola Inverardi 《Performance Evaluation》2003,51(2-4):269-288
A review is carried out on how queueing network models with blocking have been applied so far into the performance evaluation and prediction of Software Architectures (SA). Queueing network models with finite capacity queues and blocking have recently been introduced and applied as more realistic models of systems with finite capacity resources and population constraints. Queueing network models have been often adopted as models for the evaluation of software performance. Starting from our own experience, we observe the need of a more accurate definition of the performance models of SA to capture some features of the communication systems. We consider queueing networks with finite capacity and blocking after service (BAS) to represent some synchronization constraints that cannot be easily modeled with queueing network models with infinite capacity queues. We investigate the use of queueing networks with blocking as performance models of SA with concurrent components and synchronous communication. Queueing theoretic analysis is used to solve the queueing network model and study the synchronous communication and performance of concurrent software components. Our experience is supported by other approaches that also propose the use of queueing networks with blocking. Directions for future research work in the field are included. 相似文献
32.
利用沉降离心法将老虎山黄土-古土壤的酸不溶相分离成<2μm、2~45μm和>45μm三个粒级组分,并分别测定了这些组分和全岩的磁化率。结果表明,无论是全岩,还是三个不同粒级组分,它们的磁化率都可以单独作为长江中下游地区古气候演变的参考指标。其中,<2μm粒级的质量磁化率明显大于全岩和2~45μm、>45μm两粒级,而且其分辨率也明显高于2~45μm和>45μm这两个粒级组分。本实验结果还显示,虽然<2μum的质量磁化率最大,但对全岩质量磁化率的贡献率与2~45μm粒级相当,>45μm粒级的贡献率较低。 相似文献
33.
34.
It is well recognized that performance changes over time. However, the effect of these changes on overall assessments of performance is largely unknown. In a laboratory experiment, we examined the influence of salient Gestalt characteristics of a dynamic performance profile on supervisory ratings. We manipulated performance trend (flat, linear-improving, linear-deteriorating, U-shaped, and ∩-shaped), performance variation (small, large), and performance mean (negative, zero, positive) within subjects and display format (graphic, tabular) between subjects. Participants received and evaluated information about the weekly performance of different employees over a simulated 26-week period. Results showed strong main effects on performance ratings of both performance mean and performance trend, as well as interactions with display format. Theoretical and practical implications of the results are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
35.
Prolog逻辑程序设计语言具有不同于传统程序设计语言的特点.本文根据测试Prolog程序的实践,提出了一系列为Prolog程序生成测试用例的准则.按这些准则测试实际程序效果良好.这是在逻辑程序测试新领域迈出的一步. 相似文献
36.
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
37.
离子注入对Cr12MoV钢表面组织结构和力学性能的影响 总被引:1,自引:0,他引:1
研究了Cr12MoV钢离子注入层的显微组织特征及其对表面性能的影响。结果表明,离子注入使Cr12MoV钢的表面硬度和耐磨性能得到显著改善,且存在着一个最佳的注入剂量,约为3×10^1^7N^+/cm^2左右。离了注入在Cr12MoV钢表面层中形成了大量细小弥散的第二相粒子,并使α-Fe晶格发生严重畸变,从而引起材料表面强化。 相似文献
38.
用标准C语言在IBM-PC兼容微机上开发了基于PROSITE数据库检索蛋白质序列功能位点的PPS程序,PROSITE是Bairoch建立的蛋白质功能位点或结构模式的资料库,为蛋白质序列分析和结构功能研究提供了新工具。 相似文献
39.
40.
本文介绍了磨前滚刀滚切齿轮的最大根切量和磨后的渐开线长度计算,并建立了数学模型。为更加直观起见,还建立了模拟滚齿的数学模型。并在实验的基础上提出了参考标准。 相似文献