全文获取类型
收费全文 | 8426篇 |
免费 | 87篇 |
国内免费 | 133篇 |
专业分类
电工技术 | 88篇 |
综合类 | 48篇 |
化学工业 | 883篇 |
金属工艺 | 180篇 |
机械仪表 | 426篇 |
建筑科学 | 530篇 |
矿业工程 | 212篇 |
能源动力 | 45篇 |
轻工业 | 2070篇 |
水利工程 | 127篇 |
石油天然气 | 118篇 |
武器工业 | 32篇 |
无线电 | 362篇 |
一般工业技术 | 2882篇 |
冶金工业 | 114篇 |
原子能技术 | 103篇 |
自动化技术 | 426篇 |
出版年
2023年 | 13篇 |
2022年 | 14篇 |
2021年 | 26篇 |
2020年 | 17篇 |
2019年 | 17篇 |
2018年 | 19篇 |
2017年 | 13篇 |
2016年 | 13篇 |
2015年 | 25篇 |
2014年 | 42篇 |
2013年 | 40篇 |
2012年 | 811篇 |
2011年 | 1140篇 |
2010年 | 223篇 |
2009年 | 107篇 |
2008年 | 771篇 |
2007年 | 754篇 |
2006年 | 625篇 |
2005年 | 603篇 |
2004年 | 494篇 |
2003年 | 422篇 |
2002年 | 362篇 |
2001年 | 283篇 |
2000年 | 289篇 |
1999年 | 163篇 |
1998年 | 96篇 |
1997年 | 97篇 |
1996年 | 81篇 |
1995年 | 70篇 |
1994年 | 75篇 |
1993年 | 61篇 |
1992年 | 75篇 |
1991年 | 56篇 |
1990年 | 67篇 |
1989年 | 67篇 |
1988年 | 42篇 |
1987年 | 56篇 |
1986年 | 49篇 |
1985年 | 71篇 |
1984年 | 55篇 |
1983年 | 75篇 |
1982年 | 50篇 |
1981年 | 36篇 |
1980年 | 40篇 |
1979年 | 41篇 |
1978年 | 14篇 |
1977年 | 8篇 |
1976年 | 10篇 |
1966年 | 8篇 |
1965年 | 7篇 |
排序方式: 共有8646条查询结果,搜索用时 0 毫秒
41.
42.
Interaction between dietary protein and fat in triglyceride metabolism in the rat: Effects of soy protein and menhaden oil 总被引:4,自引:0,他引:4
The objective of the present study was to determine the mechanisms by which dietary proteins interact with dietary lipids
in the regulation of triglyceridemia in rats. Male Sprague-Dawley rats (n=56) were subjected to 28-d experimental diets containing different combinations of proteins (20% w/w) and lipid sources (14%
w/w): (i) casein-menhaden oil, (ii) casein-beef tallow, (iii) soy protein-menhaden oil, and (iv) soy protein-beef tallow.
Significant protein-lipid interactions were observed on triglyceridemia and hepatic cholesterol in fasted rats. The combination
of casein and beef tallow was associated with high plasma TG and hepatic cholesterol concentrations, which were reduced by
substitution either of soy for casein or of menhaden oil for beef tallow. Therefore, triglyceridemia and liver cholesterol
remained low with soy protein feeding, independently of the lipid source, as well as with menhaden oil feeding, regardless
of the protein source. The menhaden oil diets reduced plasma cholesterol, hepatic TG, and TG secretion compared with beef
tallow diets independently of the dietary protein source. Modifying the source of dietary proteins and lipids had no effect
on post-heparin plasma lipoprotein lipase activity. These results demonstrate that soy protein can lower rat triglyceridemia
relative to casein when associated with beef tallow consumption, whereas menhaden oil can attenuate hypertriglyceridemia when
rats are fed casein. The data further suggest that part of the hypotriglyceridemic effect of soy protein in the rat may be
mediated by reduced hepatic lipid synthesis, as is the case for menhaden oil. 相似文献
43.
The full-range behavior of partially bonded, together with partially prestressed concrete beams containing fiber reinforced
polymer (FRP) tendons and stainless steel reinforcing bars was simulated using a simplified theoretical model. The model assumes
that a section in the beam has a trilinear moment—curvature relationship characterized by three particular points, initial
cracking of concrete, yielding of non-prestressed steel, and crushing of concrete or rupturing of prestressing tendons. Predictions
from the model were compared with the limited available test data, and a reasonable agreement was obtained. A detailed parametric
study of the behavior of the prestressed concrete beams with hybrid FRP and stainless steel reinforcements was conducted.
It can be concluded that the deformability of the beam can be enhanced by increasing the ultimate compressive strain of concrete,
unbonded length of tendon, percentage of compressive reinforcement and partial prestress ratio, and decreasing the effective
prestress in tendons, and increasing in ultimate compressive strain of concrete is the most efficient one. The deformability
of the beam is almost directly proportional to the concrete ultimate strain provided the failure mode is concrete crushing,
even though the concrete ultimate strain has less influence on the load-carrying capacity.
Foundation item: Project (50478502) supported by the National Natural Science Foundation of China 相似文献
44.
Garrett BC Dixon DA Camaioni DM Chipman DM Johnson MA Jonah CD Kimmel GA Miller JH Rescigno TN Rossky PJ Xantheas SS Colson SD Laufer AH Ray D Barbara PF Bartels DM Becker KH Bowen KH Bradforth SE Carmichael I Coe JV Corrales LR Cowin JP Dupuis M Eisenthal KB Franz JA Gutowski MS Jordan KD Kay BD Laverne JA Lymar SV Madey TE McCurdy CW Meisel D Mukamel S Nilsson AR Orlando TM Petrik NG Pimblott SM Rustad JR Schenter GK Singer SJ Tokmakoff A Wang LS Wettig C Zwier TS 《Chemical reviews》2005,105(1):355-390
45.
46.
已开发出一种获得专利的废橡胶脱硫新工艺和几种反应装置。这一技术以使用高能超声波为基础,一定频率的超声波在一定压力和温度条件下迅速地破坏硫化橡胶的三维网络。脱硫胶几乎和新胶一样能够重新加工、定型和硫化。第一个实验脱硫装置已由NationalFeedscrewandMachining(NFM)公司扩大至中试水平。本研究采用SBR和废轮胎胶粉(GRT)进行了多种脱硫试验,对不同工艺条件下脱硫橡胶的硫化性能、流变性能、结构特性以及脱硫胶试样的物理性能进行了研究,讨论了一种可能的脱硫机理。完成的测试表明,在超声波作用下,硫化橡胶只是部分脱硫,而且在脱硫过程中伴随一些大分子链的降解,尽管如此,在实验确定的工艺条件下获得的脱硫胶还是能保持良好的机械性能。进一步的工作是寻找最佳脱硫工艺条件和提高该工艺只破坏化学交联网络的针对性。 相似文献
47.
苯甲酰苯基脲类化合物杀虫活性的发现揭示了化学防治公害的新途径.第一个商品化的化合物除虫脲能干扰昆虫蜕皮过程,因而作为昆虫生长调节剂使用.其主要作用方式为摄入,对某些昆虫也可通过触杀而起作用.其部分活性似乎与对于几丁质形成的生物化学过程的抑制作用有关.对于更有前途的酰脲化合物的探索工作得到了三个对农业害虫较除虫脲有更高活性的新型化合物:石原公司的chlorfluazuron、Calemerck公司的teflubenzuron 相似文献
48.
用“双套管法”淬火测定Cu:Cu-Al扩散偶中的相平衡,由于该法具有较快的冷却速度,保证了α/β相界面处于局部平衡.传统的淬火方法冷速通常是不够快的,不足以抑制β相的分解.较慢的冷却使界面形貌发生改变;测出的界面浓度是较低温度下的数值.有理由相信,Eifert等实验得到的各温度下都远较平衡浓度为高的α/β相界浓度,是由于实验过程中较慢的冷速所导致. 相似文献
49.
DESPITE of the rapid development of computerfacilities and numerical methods of computing thestress-strain state of large-size parts,the accuracy ofcomputations is not sufficient because of the lack ofaccurate input data.For this reason,heat treatingengineers do not trust computations and are afraid ofquenching of large-size parts in water,in particular,when Bi—>°°.There are some causes of suchsituation:1)Because of inaccurate boundary conditions andincomplete information on mechanical p… 相似文献
50.