全文获取类型
收费全文 | 8590篇 |
免费 | 102篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 139篇 |
综合类 | 4篇 |
化学工业 | 866篇 |
金属工艺 | 109篇 |
机械仪表 | 144篇 |
建筑科学 | 164篇 |
矿业工程 | 32篇 |
能源动力 | 105篇 |
轻工业 | 709篇 |
水利工程 | 42篇 |
石油天然气 | 22篇 |
无线电 | 794篇 |
一般工业技术 | 984篇 |
冶金工业 | 3748篇 |
原子能技术 | 109篇 |
自动化技术 | 722篇 |
出版年
2021年 | 47篇 |
2019年 | 46篇 |
2018年 | 51篇 |
2017年 | 57篇 |
2016年 | 73篇 |
2015年 | 52篇 |
2014年 | 83篇 |
2013年 | 197篇 |
2012年 | 165篇 |
2011年 | 230篇 |
2010年 | 195篇 |
2009年 | 207篇 |
2008年 | 230篇 |
2007年 | 234篇 |
2006年 | 199篇 |
2005年 | 202篇 |
2004年 | 186篇 |
2003年 | 165篇 |
2002年 | 143篇 |
2001年 | 148篇 |
2000年 | 163篇 |
1999年 | 223篇 |
1998年 | 928篇 |
1997年 | 569篇 |
1996年 | 453篇 |
1995年 | 262篇 |
1994年 | 252篇 |
1993年 | 297篇 |
1992年 | 155篇 |
1991年 | 156篇 |
1990年 | 146篇 |
1989年 | 167篇 |
1988年 | 149篇 |
1987年 | 127篇 |
1986年 | 149篇 |
1985年 | 130篇 |
1984年 | 87篇 |
1983年 | 90篇 |
1982年 | 81篇 |
1981年 | 69篇 |
1980年 | 73篇 |
1979年 | 78篇 |
1978年 | 81篇 |
1977年 | 127篇 |
1976年 | 205篇 |
1975年 | 61篇 |
1974年 | 56篇 |
1973年 | 53篇 |
1972年 | 38篇 |
1971年 | 36篇 |
排序方式: 共有8693条查询结果,搜索用时 15 毫秒
61.
Numerous reports have demonstrated that specific protein synthesis in response to specific inducers is markedly stimulated by a simultaneous brief exposure to protein synthesis inhibitors such as cycloheximide. This phenomenon is known as "superinduction" and is most often attributed to the accumulation of cytoplasmic messenger RNA during the inhibition period. Messenger RNA, as defined by rapid labeling, oligo (dt)-cellulose binding, and cell free protein synthesis stimulation was measured in cycloheximide treated human fibroblasts. In spite of a consistent 40% decrease in total polysomal 3H-uridine labeled RNA, a 1.5- to 2-fold increase in extractable mRNA was observed. These data provide direct evidence that protein synthesis inhibition stimulates the appearance of cytoplasmic mRNA and/or completely blocks its degradation and, are consistent with the hypothesis that mRNA accumulation partly underlies the superinduction phenomena. 相似文献
62.
A review of the American Cancer Society's statistics for colorectal cancer indicates that there has been little improvements in the survival rate for this disease in the past 25 years. Although there have been advances in surgical techniques, radiation therapy, and chemotherapy, the key to improved survival rates is earlier diagnosis. A significant percentage of patients continues to present with regional or distal metastasis at the time of their initial diagnosis. Both proctosigmoidoscopy and guaiac impregnated filter slide paper methods have been productive in diagnosing this disease at an earlier stage. The "Hemoccult" test, however, is inexpensive, can be used on a routine basis, is easier for patients to perform themselves, and is aesthetically pleasing. It represents a significant cost savings compared to proctosigmoidoscopy and should be advocated for routine use in all patients over 40 years of age. Although there continues to be a role for local and regional mass screening programs, significant improvements in colorectal survival rates cannot be expected until routine application of this type of screening is practiced. 相似文献
63.
Miller S 《Environmental science & technology》1983,17(12):568A-570A
64.
The effects of transcontinental (interstate) transport and transoceanic shipment were determined on microbiological and shelf-life characteristics of beef tongues and livers. These variety meats were evaluated for both microbiological and shelf-life characteristics following slaughter in Guymon, Oklahoma, USA. The samples were then frozen and sent by refrigerated truck (4·5°C) to storage facilities in Jacksonville, Florida, USA. Further microbiological and shelf-life evaluations took place prior to overseas shipment at the University of Florida and following overseas shipment at The Institute CIVO-Technology, TNO, Zeist, The Netherlands. Aerobic plate counts (APCs) at 35°C for beef tongues showed a significant (P < 0·0.5) decrease following overseas shipment. Similar results were noted for beef livers. For both organs, the surface thawing in Florida, required for sampling, did not appear to affect the final bacterial counts. The 20°C APCs for beef tongues revealed a significant (P < 0·0.5) decrease following interstate transport but not transoceanic shipment. The 20°C APCs for beef livers did not differ significantly during the entire transportation period. The colour differences noted during transport of the product were probably the result of freezing and not of the actual shipping and storage conditions. 相似文献
65.
Miller S 《Environmental science & technology》1982,16(5):276A-279A
66.
Carl Miller Helen Austin Larry Posorske Jesus Gonzlez 《Journal of the American Oil Chemists' Society》1988,65(6):927-931
The lipase-catalyzed synthesis of ester bonds has been well-documented lately and is of much current commercial interest.
Immobilization of a fungal lipase on a unique macroporous support allows not only the ability to operate in non-aqueous media
but to catalyze ester synthesis in quantitative yields, employing attractive commercial conditions. Catalyst dose and process
configurations will be illustrated. The capability of the catalyst to operate efficiently in reverse under a variety of unnatural,
hostile, solvent-containing environments will be discussed. The range of substrates for this immobilized lipase, Lipzome,
has been investigated. The enzyme will catalyze ester synthesis with saturated, unsaturated and a variety of branched carboxylic
acids. The alcohol specificity for this enzyme also is equally broad. A wide variety of straight-chain, branched and polar
alcohols can be substrates. In addition, some examples of alcohol specificity for kinetic isomer resolution will be cited.
Presented at the symposium “The Biology, Biotechnology and Technology of Lipases” at the 78th annual meeting of the American
Oil Chemists’ Society held May 17–21, 1987, in New Orleans, Louisiana. 相似文献
67.
The right eye of a 9-year-old white boy with Best's vitelliform macular dystrophy had an intact egg-yolk lesion and a retinal pigment epithelial defect superiorly, suggesting an early pseudohypopyon stage. The disruptive phase of the left eye showed subretinal hemorrhages, a "signet ring," and a subretinal neovascular membrane. 相似文献
68.
69.
Aviles Fredy; Earleywine Mitchell; Pollock Vicki; Stratton Joy; Miller Norman 《Canadian Metallurgical Quarterly》2005,19(1):108
The authors examined alcohol's effect on triggered displaced aggression, the hostile reaction to a second provoking person after provocation from a first. Participants consumed an alcoholic or a nonalcoholic beverage. Subsequently, one individual provoked all of them with moderate intensity. Then, 2 groups were studied: those who received or who failed to receive a second provocation of minimal intensity. Consistent with prior research, participants who received a second, minimal provocation displayed more aggression than those who did not. After participants drank alcohol, the magnitude of this difference was significantly greater, indicating that alcohol increases triggered displaced aggression. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
70.
In adaptive control the goal is to design a controller to control an uncertain system whose parameters may be changing with time. Typically the controller consists of an identifier (or tuner) which is used to adjust the parameters of a linear time-invariant (LTI) compensator, and under suitable assumptions on the plant model uncertainty it is proven that good asymptotic behaviour is achieved, such as model matching (for minimum phase systems) or stability. However, a typical adaptive controller does not track time-varying parameters very well, and it is often highly nonlinear, which can result in undesirable behaviour, such as large transients or a large control signal. Furthermore, most adaptive controllers provide only asymptotic tracking, with no ability to design for a pre-specified settling time.Here we propose an alternative approach, which yields a linear periodic controller. Rather than estimating the plant or compensator parameters, instead we estimate what the control signal would be if the plant parameters were known. In this paper we argue the utility of this approach and then examine the first order case in detail, including a simulation. We also explore the benefits and limitations of the approach. 相似文献