全文获取类型
收费全文 | 2755篇 |
免费 | 64篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 26篇 |
化学工业 | 609篇 |
金属工艺 | 40篇 |
机械仪表 | 50篇 |
建筑科学 | 114篇 |
矿业工程 | 11篇 |
能源动力 | 44篇 |
轻工业 | 256篇 |
水利工程 | 17篇 |
石油天然气 | 6篇 |
无线电 | 349篇 |
一般工业技术 | 359篇 |
冶金工业 | 499篇 |
原子能技术 | 30篇 |
自动化技术 | 412篇 |
出版年
2022年 | 24篇 |
2021年 | 42篇 |
2020年 | 29篇 |
2019年 | 30篇 |
2018年 | 41篇 |
2017年 | 33篇 |
2016年 | 36篇 |
2015年 | 41篇 |
2014年 | 56篇 |
2013年 | 137篇 |
2012年 | 86篇 |
2011年 | 110篇 |
2010年 | 84篇 |
2009年 | 104篇 |
2008年 | 108篇 |
2007年 | 120篇 |
2006年 | 87篇 |
2005年 | 87篇 |
2004年 | 74篇 |
2003年 | 66篇 |
2002年 | 78篇 |
2001年 | 52篇 |
2000年 | 51篇 |
1999年 | 57篇 |
1998年 | 128篇 |
1997年 | 94篇 |
1996年 | 66篇 |
1995年 | 50篇 |
1994年 | 43篇 |
1993年 | 53篇 |
1992年 | 47篇 |
1991年 | 47篇 |
1990年 | 35篇 |
1989年 | 30篇 |
1988年 | 34篇 |
1987年 | 43篇 |
1986年 | 34篇 |
1985年 | 32篇 |
1984年 | 36篇 |
1983年 | 30篇 |
1982年 | 20篇 |
1981年 | 38篇 |
1980年 | 25篇 |
1979年 | 21篇 |
1978年 | 28篇 |
1977年 | 40篇 |
1976年 | 46篇 |
1975年 | 39篇 |
1974年 | 20篇 |
1973年 | 19篇 |
排序方式: 共有2822条查询结果,搜索用时 15 毫秒
1.
2.
Gilbert Held 《International Journal of Network Management》2003,13(2):163-169
3.
Gilbert Held 《International Journal of Network Management》2006,16(5):375-379
One of the software programs we take for granted is antivirus software. Perhaps part of the reason for not being excited about protecting our computers resides in the fact that most PCs marketed over the past few years are bundled with an antivirus solution. When you initialize the computer you also start your virus protection program, which will often provide you with only a short period of protection before pop‐up messages appear reminding you to renew your antivirus program license to ensure your protection is up to date. What is more than likely never mentioned to consumers is the fact that the antivirus software bundled with your computer was positioned there due to the software vendor paying the computer manufacturer a fee. While most third‐party software placed on new computers must pass a certain level of quality assurance, the computer manufacturer is more interested in the placement fee than whether the software is the best for the purchaser of the computer. Thus, one of the things we should do when our antivirus software license expires, if not sooner, is to look at other possible solutions beyond the software bundled with the computer. One such antivirus product that warrants our attention and which is the focus of this column is ESET's NOD32 for Windows antivirus solution, which was originally developed in Slovakia. 相似文献
4.
MC Jacobson E Franssen BD Birt MJ Davidson RW Gilbert 《Canadian Metallurgical Quarterly》1997,26(3):171-179
The aim of this study was to investigate the effect of the absence of elongate spermatids (ES) from the rat seminiferous epithelium on the quantitative secretion and synthesis of the three major Sertoli cell secretory proteins--SGP-1, SGP-2 and CP-2. Seminiferous tubules (ST) were isolated (a) from normal 28-day-old rats, in which the most mature germ cell type is the round spermatid, (b) from normal adult rats at stages IX-XIV of the spermatogenic cycle, i.e. after spermiation, or at stages I-V and VI-VIII, when ES are still attached to the Sertoli cell, and (c) at stages VI-VIII from normal adult rats and from rats treated with methoxyacetic acid (MAA) in order to specifically deplete ES at these stages. Two-dimensional SDS PAGE combined with computerized image analysis was used to analyse 35S-methionine-labelled intracellular and secreted proteins. In the case of SGP-1 and SGP-2, almost all of the protein synthesized by ST was secreted. The total amount of both SGP-1 and CP-2 secreted by unstaged ST from immature rats was significantly lower than that secreted by unstaged ST from adult rats. The total amount of SGP-1 and CP-2 secreted by adult ST at stages IX-XIV of the spermatogenic cycle also declined dramatically compared to ST at earlier stages. The proportion of the total CP-2 synthesized by ST which was secreted also declined in all situations in which ES were absent from the seminiferous epithelium. The synthesis of only SGP-2 was changed by ES depletion from ST at stages VI-VIII, which was almost doubled compared to synthesis of this protein by ST from control rats. Our results suggest strongly that the secretion of SGP-1 and SGP-2 is via the constitutive pathway, and that regulation of these two proteins by ES is at the level of protein synthesis. In contrast, the regulation of CP-2 by ES is predominantly at the level of secretion, suggesting that this protein is secreted via a regulated pathway. Our findings add to the evidence showing that ES play a major role in the regulation of Sertoli cell function. 相似文献
5.
B Blanc P Laloi D Atlan C Gilbert R Portalier 《Canadian Metallurgical Quarterly》1993,139(7):1441-1448
Lactobacillus helveticus ITGL1 is able to hydrolyse many amino-acyl and dipeptidyl-p-nitroanilides. Analysis of heat inactivation kinetics, metal ion and protease inhibitor effects, and the subcellular location of aminopeptidase activities in both the parental strain and mutants deficient in lysyl-p-nitroanilide hydrolysis, led to the characterization of two cell-wall-associated aminopeptidases, APII and APIV. APII, which catalysed L-lysine p-nitroanilide hydrolysis, was purified about 28-fold to homogeneity from cell-wall extracts of L. helveticus ITGL1 and characterized. The purified enzyme appeared to be monomeric, with a molecular mass of 97 kDa. Aminopeptidase activity was greatest at pH 6.5 and 50 degrees C. APII was completely inhibited by bestatin, chelating agents such as EDTA or 1,10-phenanthroline and the divalent cations Zn2+ and Cu2+. The activity of the EDTA-treated enzyme was restored by Co2+, Ca2+ or Mn2+. Although APII was able to degrade several dipeptides and tripeptides with hydrophobic N-terminal amino acid (Leu, Ala), it was inactive on peptides containing Pro or Gly, and may thus contribute to the development of cheese flavour by processing bitter peptides. 相似文献
6.
7.
Small-angle neutron scattering by a polymer melt with partly tagged chains is considered. When several types of chain (differently labelled) are present in the system a new long-range correlation effect which modifies the scattering spectrum is predicted. This effect will arise because of the chemical polydispersity of the sample. A general formalism is developed to calculate the scattering intensity and is applied to special cases: diblock and triblock chains. It is shown that even a small chemical polydispersity leads to important long-range fluctuations and modifies the scattering spectrum substantially. 相似文献
8.
Inaki Arrazola Agn s Plainfoss Henri Prade Claudette Testemale 《Information Systems》1989,14(6):487-492
This paper presents different approaches which enable a data base management system to obtain a plausible fuzzy estimate for an attribute value of an item for which the information is not explicitly stored in the data base. This can be made either by a kind of analogical reasoning from information about particular items or by means of expert rules which specify the (fuzzy) sets of possible values of the attribute under consideration, for various classes of items. Another kind of expert rules enables the system to compute an estimate from the attribute value of another item provided that, in other respects, this latter item sufficiently resembles the item, the value of which we are interested in; then these expert rules are used either for controlling the analogical reasoning process or for enlarging the scope of application of the first kind of expert rules. The different approaches are discussed in the framework of possibility theory. 相似文献
9.
Facility layout problems: A survey 总被引:3,自引:0,他引:3
Layout problems are found in several types of manufacturing systems. Typically, layout problems are related to the location of facilities (e.g., machines, departments) in a plant. They are known to greatly impact the system performance. Most of these problems are NP hard. Numerous research works related to facility layout have been published. A few literature reviews exist, but they are not recent or are restricted to certain specific aspects of these problems. The literature analysis given here is recent and not restricted to specific considerations about layout design.
We suggest a general framework to analyze the literature and present existing works using such criteria as: the manufacturing system features, static/dynamic considerations, continual/discrete representation, problem formulation, and resolution approach. Several research directions are pointed out and discussed in our conclusion. 相似文献
10.
The high-temperature crystallization of poly(p-phenylene terephthalamide) (PPTA) from dilute organic solutions was achieved through the introduction of a non-solvent, or precipitating agent, at the desired crystallization temperature. The morphology and crystal structure were examined for crystals produced from PPTA polymer with two different molecular weights (Mw = 46000 and 3430 g mol−1), using transmission electron microscopy. For the high-molecular-weight polymer, ribbon-like crystals were produced, while the low-molecular-weight polymer yielded small needles or platelets. In both cases, electron diffraction showed that the Northolt allomorph was obtained. For the high-molecular-weight polymer, the molecular axes were parallel to the ribbon axes in a chain-extended type structure. A hypothesis for the orientation of the low-molecular-weight PPTA in the small platelets, is also given. 相似文献