全文获取类型
收费全文 | 80907篇 |
免费 | 10378篇 |
国内免费 | 6572篇 |
专业分类
电工技术 | 7041篇 |
技术理论 | 2篇 |
综合类 | 9244篇 |
化学工业 | 7181篇 |
金属工艺 | 2871篇 |
机械仪表 | 6699篇 |
建筑科学 | 11672篇 |
矿业工程 | 2694篇 |
能源动力 | 2443篇 |
轻工业 | 7751篇 |
水利工程 | 2693篇 |
石油天然气 | 3662篇 |
武器工业 | 1339篇 |
无线电 | 5591篇 |
一般工业技术 | 9851篇 |
冶金工业 | 3040篇 |
原子能技术 | 746篇 |
自动化技术 | 13337篇 |
出版年
2024年 | 593篇 |
2023年 | 1640篇 |
2022年 | 2982篇 |
2021年 | 3200篇 |
2020年 | 3423篇 |
2019年 | 2837篇 |
2018年 | 2765篇 |
2017年 | 3273篇 |
2016年 | 3591篇 |
2015年 | 3704篇 |
2014年 | 5039篇 |
2013年 | 5243篇 |
2012年 | 6457篇 |
2011年 | 6389篇 |
2010年 | 4777篇 |
2009年 | 4675篇 |
2008年 | 4406篇 |
2007年 | 5278篇 |
2006年 | 4537篇 |
2005年 | 3788篇 |
2004年 | 3093篇 |
2003年 | 2613篇 |
2002年 | 2048篇 |
2001年 | 1919篇 |
2000年 | 1658篇 |
1999年 | 1330篇 |
1998年 | 1095篇 |
1997年 | 970篇 |
1996年 | 786篇 |
1995年 | 685篇 |
1994年 | 549篇 |
1993年 | 457篇 |
1992年 | 363篇 |
1991年 | 274篇 |
1990年 | 259篇 |
1989年 | 232篇 |
1988年 | 159篇 |
1987年 | 115篇 |
1986年 | 65篇 |
1985年 | 80篇 |
1984年 | 77篇 |
1983年 | 52篇 |
1982年 | 49篇 |
1981年 | 18篇 |
1980年 | 53篇 |
1979年 | 40篇 |
1965年 | 16篇 |
1964年 | 21篇 |
1959年 | 15篇 |
1955年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
Protein Extraction from Heat-stabilized Defatted Rice Bran: II. The Role of Amylase, Celluclast, and Viscozyme 总被引:1,自引:0,他引:1
ABSTRACT: The effectiveness of 3 carbohydrases for protein extraction from heat-stabilized defatted rice bran (HDRB) was evaluated. Amylase, viscozyme and celluclast extracted a maximum of 45.4, 12.1, and 28.5% protein, respectively. Further study showed that extracted protein ranged from 9.5 to 58.4% under conditions of water to bran ratio (5:1 to 20:1), α-amylase (0 to 110000 units/10 g rice bran), temperature (35 to 55 °C), and time (1 to 8 h). The maximum protein extracted was 58.4% with a water to bran ratio of 17:1, 87637 units amylase, and 50.9 °C. These results suggest that impure food-grade amylase containing protease is more effective than celluclast and viscozyme in protein extraction from HDRB. 相似文献
32.
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
33.
34.
The current study replicated, in a sample of 2,300 outpatients seeking psychiatric treatment, a previous study (R. F. Krueger & M. S. Finger, 2001) that implemented an item response theory approach for modeling the comorbidity of common mood and anxiety disorders as indicators along the continuum of a shared latent factor (internalizing). The 5 disorders examined were major depressive disorder, social phobia, panic disorder/agoraphobia, specific phobia, and generalized anxiety disorder. The findings were consistent with the prior research. First, a confirmatory factor analysis yielded sufficient evidence for a nonspecific factor underlying the 5 diagnostic indicators. Second, a 2-parameter logistic item response model showed that the diagnoses were represented in the upper half of the internalizing continuum, and each was a strongly discriminating indicator of the factor. Third, the internalizing factor was significantly associated with 3 indexes of social burden: poorer social functioning, time missed from work, and lifetime hospitalizations. Rather than the categorical system of presumably discrete disorders presented in DSM-IV, these 5 mood and anxiety disorders may be alternatively viewed as higher end indicators of a common factor associated with social cost. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
35.
Sinéad C. Mac Namara Maria M. Garlock David P. Billington 《Canadian Metallurgical Quarterly》2007,21(2):152-156
Steam generator replacement at nuclear power plants requires large construction openings in nuclear containment structures. This study examines the effects of such openings placed in a 61?cm (2?ft) thick dome of a shield building. The dome is cast in two layers, and the limiting cases of the two layers acting as one and the lower layer carrying the entire load are considered. Without openings, the stresses due to dead load in the structure are very low when compared to the material strength. With openings, the loads are easily redistributed around the opening, and the maximum stresses for the conservative case are between three and four and one-half times larger than in the original structure with no openings. The extent of the affected area around the holes is relatively small. Smooth corners in the openings are necessary to avoid high local stress concentrations. 相似文献
36.
已往库存论中的决策模型,它是把现实过程用数学的方法进行分析,得到决策值,但不能看到决策的过程,不能反映出现实生活中的不确定性、动态性。运用Delphi 7.0和SQL server 2000对销售过程进行了动态仿真,利用Newsboy模型的推广(S,s)订购策略来监控库存并做出决策,这样就体现出此过程的不确定性、动态性;且举出了一个仿真商品销售的实例,对其中的一些关键技术,如何仿真、算法的实现等进行了阐述。 相似文献
37.
利用随机振动复模态分析,提出了一种求解时变线性系统,在确定性激励与随机激励共同作用下非平稳随机响应的计算方法,并以舰载火箭武器系统为研究对象,用该法探讨了海浪对舰面火箭发射初始扰动和系统振动特性的影响。 相似文献
38.
重力坝常采用横,纵缝将坝体分为柱状体施工。为此,横缝须设置止水,纵缝则待坝体冷却后灌浆,将柱状坝块连成整体。此外坝体内部还须设置坝面排水管以消除坝内渗透压力。关于坝内这些细部构造,设计规范仅有原则性要求,一般专业书列举不多,目前有些工程往往参照已建工程的设计图采用,常由于施工详图不祥易发生施工质量问题。根据丹江口重力坝设计经验,对接缝灌浆中的键槽,止浆片,灌浆管道,出浆盒,排气槽及排气管,基岩陡坡 相似文献
39.
40.
单层球面网壳地震反应特征分析 总被引:29,自引:0,他引:29
考虑不同矢跨比、荷载、跨度和支座刚度等多种因素的影响,对单层球面网壳在地震作用下的反应进行了较全面的研究,给出了其随各参数变化的规律,得出了在单层球面网壳抗震设计中起控制作用的是水平地震作用而不是竖向地震作用等有益的结论.此外本文还给出了由于阻尼比不同而需对引用现行抗震规范反应谱分析的网壳地震作用进行修正的建议. 相似文献