全文获取类型
收费全文 | 16186篇 |
免费 | 1390篇 |
国内免费 | 661篇 |
专业分类
电工技术 | 930篇 |
技术理论 | 2篇 |
综合类 | 932篇 |
化学工业 | 2830篇 |
金属工艺 | 1045篇 |
机械仪表 | 1071篇 |
建筑科学 | 1201篇 |
矿业工程 | 566篇 |
能源动力 | 459篇 |
轻工业 | 916篇 |
水利工程 | 257篇 |
石油天然气 | 1276篇 |
武器工业 | 113篇 |
无线电 | 1797篇 |
一般工业技术 | 1957篇 |
冶金工业 | 884篇 |
原子能技术 | 162篇 |
自动化技术 | 1839篇 |
出版年
2024年 | 85篇 |
2023年 | 317篇 |
2022年 | 513篇 |
2021年 | 708篇 |
2020年 | 571篇 |
2019年 | 479篇 |
2018年 | 543篇 |
2017年 | 552篇 |
2016年 | 475篇 |
2015年 | 645篇 |
2014年 | 830篇 |
2013年 | 920篇 |
2012年 | 1005篇 |
2011年 | 1072篇 |
2010年 | 919篇 |
2009年 | 909篇 |
2008年 | 924篇 |
2007年 | 804篇 |
2006年 | 825篇 |
2005年 | 677篇 |
2004年 | 554篇 |
2003年 | 462篇 |
2002年 | 449篇 |
2001年 | 380篇 |
2000年 | 374篇 |
1999年 | 414篇 |
1998年 | 312篇 |
1997年 | 297篇 |
1996年 | 250篇 |
1995年 | 223篇 |
1994年 | 184篇 |
1993年 | 131篇 |
1992年 | 118篇 |
1991年 | 70篇 |
1990年 | 69篇 |
1989年 | 49篇 |
1988年 | 31篇 |
1987年 | 28篇 |
1986年 | 18篇 |
1985年 | 12篇 |
1984年 | 13篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 7篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
The growing number of processing cores in a single CPU is demanding more parallelism from sequential programs. But in the past decades few work has succeeded in automatically exploiting enough parallelism, which casts a shadow over the many-core architecture and the automatic parallelization research. However, actually few work was tried to understand the nature, or amount, of the potentially available parallelism in programs. In this paper we will analyze at runtime the dynamic data dependencies among superblocks of sequential programs. We designed a meta re-arrange buffer to measure and exploit the available parallelism, with which the superblocks are dynamically analyzed, reordered and dispatched to run in parallel on an ideal many-core processor, while the data dependencies and program correctness are still maintained. In our experiments, we observed that with the superblock reordering, the potential speedup ranged from 1.08 to 89.60. The results showed that the potential parallelism of normal programs was still far from fully exploited by existing technologies. This observation makes the automatic parallelization a promising research direction for many-core architectures. 相似文献
102.
In the present study we investigated the effects of dietary fats containing predominantly PUFA, monounsaturated FA (MUFA),
or saturated FA (SFA) on lipid profile and liver cholesterol 7α-hydroxylase (CYP7α1) mRNA expression and bile acid production
in C57BL/6J mice. The animals (n=75) were randomly divided into five groups and fed a basic chow diet (AIN-93G) (BC diet), a chow diet with 1g/100g of cholesterol
(Chol diet), a chow diet with 1g/100g of cholesterol and 14g/100g of safflower oil (Chol+PUFA diet), a chow diet with 1g/100g
of cholesterol and olive oil (Chol+MUFA diet), or a chow diet with 1g/100g of cholesterol and myristic acid (Chol+SFA diet)
for 6 wk. The results showed that the Chol+SFA diet decreased CYP7α1 gene expression and bile acid pool size, resulting in
increased blood and liver cholesterol levels. Addition of PUFA and MUFA to a 1% cholesterol diet increased the bile acid pool
production or bile acid excretion and simultaneously decreased liver cholesterol accumulation despite decreased CYP7α1 mRNA
expression. The results indicate that the decreased bile acid pool size induced by the SFA diet is related to inhibition of
the liver CYP7α1 gene expression, but an increased bile acid pool size and improved cholesterol homeostasis are disassociated
from the liver CYP7α1 gene expression. 相似文献
103.
Poly(5‐bromoindole) (PBrI) films were synthesized electrochemically by direct oxidation of 5‐bromoindole in pure boron trifluoride diethyl etherate. The oxidation potential of 5‐bromoindole in this medium was measured to be only 0.97 V vs. saturated calomel electrode, which was lower than that determined in acetonitrile + 0.1 mol L?1 Bu4NBF4 (1.08 V). PBrI films obtained from this medium showed good electrochemical behavior and good thermal stability. Structural studies showed that the polymerization of 5‐bromoindole ring occurred at 2,3 position. As‐formed PBrI films were thoroughly soluble in strong polar solvent dimethylsulfoxide and partly soluble in tetrahydrofuran. Fluorescent spectral studies indicated that PBrI was a good blue‐light emitter. The excitation and emission spectra of PBrI showed a significant shift to longer wavelength compared with that of the monomer, consistent with the greater extent of electron delocalization. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 539–547, 2006 相似文献
104.
105.
催化热裂解工艺机遇及影响因素 总被引:2,自引:0,他引:2
分析了催化热裂解过程的反应机理及乙烯和丙烯形成的反应,乙烯和丙均可通过热裂解和催化裂解生成,讨论了影响乙烯,丙烯产率的因素:与USY和REY相比,使用ZSM-5催化剂能够提高乙烯,丙烯产率,磷改性ZRP-1经碱土金属改性后,可进一步提高乙烯和丙烯的产率,提高反应温度和降低剂油比,能够提高热裂解和催化裂解的比例,有利于乙烯产率的提高;增强蒸汽量能够减少焦炭产率,提高乙烯和丙烯产率。 相似文献
106.
本文依据陶瓷隧道窑热工测试数据和热平衡报告,采用多元回归和逐步回归统计理论,得到了陶瓷隧道窑单位重量热耗的多元回归数学模型和逐步回归数学模型。利用该数学模型可对单耗进行预测和控制。 相似文献
107.
108.
109.
110.
结构性土二元介质模型的有限元模拟 总被引:1,自引:1,他引:0
针对土的结构性对边坡稳定性的影响,结构性土二元介质模型将胶结元看成理想弹脆性材料,摩擦元看成硬化型弹塑性材料。基于该模型建立考虑结构性土的强度准则,编制相应有限元程序用于Biot固结的有限元模拟。通过对比初始各向同性和初始应力各向异性结构性土的天然边坡算例计算结果,发现初始应力各向异性天然边坡的安全系数要高于初始均质天然边坡;嵌入初始应力各向异性结构性土的强度准则后可以观察计算过程中边坡破坏区的发展,为采用破坏区贯通作为边坡的破坏标准的天然边坡的稳定性分析提供了一种新的思路且具有良好的工程适用性。 相似文献