全文获取类型
收费全文 | 1623篇 |
免费 | 30篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 8篇 |
化学工业 | 172篇 |
金属工艺 | 7篇 |
机械仪表 | 5篇 |
建筑科学 | 6篇 |
矿业工程 | 2篇 |
能源动力 | 18篇 |
轻工业 | 31篇 |
无线电 | 30篇 |
一般工业技术 | 57篇 |
冶金工业 | 1245篇 |
原子能技术 | 5篇 |
自动化技术 | 69篇 |
出版年
2023年 | 3篇 |
2022年 | 6篇 |
2021年 | 7篇 |
2020年 | 7篇 |
2019年 | 7篇 |
2018年 | 14篇 |
2017年 | 17篇 |
2016年 | 11篇 |
2015年 | 12篇 |
2014年 | 17篇 |
2013年 | 27篇 |
2012年 | 24篇 |
2011年 | 14篇 |
2010年 | 12篇 |
2009年 | 18篇 |
2008年 | 16篇 |
2007年 | 16篇 |
2006年 | 22篇 |
2005年 | 23篇 |
2004年 | 16篇 |
2003年 | 17篇 |
2002年 | 12篇 |
2001年 | 6篇 |
2000年 | 8篇 |
1999年 | 37篇 |
1998年 | 344篇 |
1997年 | 229篇 |
1996年 | 166篇 |
1995年 | 113篇 |
1994年 | 68篇 |
1993年 | 84篇 |
1992年 | 10篇 |
1991年 | 27篇 |
1990年 | 11篇 |
1989年 | 10篇 |
1988年 | 6篇 |
1987年 | 7篇 |
1986年 | 13篇 |
1985年 | 6篇 |
1984年 | 1篇 |
1983年 | 3篇 |
1982年 | 5篇 |
1981年 | 13篇 |
1980年 | 14篇 |
1979年 | 1篇 |
1978年 | 9篇 |
1977年 | 47篇 |
1976年 | 97篇 |
1974年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有1655条查询结果,搜索用时 0 毫秒
41.
P Lipponen S Aaltomaa M Eskelinen M Ala-Opas VM Kosma 《Canadian Metallurgical Quarterly》1998,34(3):237-243
Selective antagonists to the Type 3 serotonin receptor (5HT3) in combination with corticosteroids are now considered the standard of care for the prevention of emesis from moderately to highly emetogenic chemotherapy. Here we address issues of optimal dose, schedule and route of administration of four currently available selectable 5HT3 antagonists. This paper utilizes an evidence based medicine approach to the literature regarding this class of drugs, emphasizing the results large, randomized, controlled trials to make formal recommendations concerning optimal use of this important new class of anti-emetic agents. We conclude that for each drug there is a plateau in therapeutic efficacy at a definable dose level above which further dose escalation does not improve outcome. Furthermore, a single dose is as effective as multiple doses or continuous infusion, and finally, emerging data demonstrate that the oral route is equally efficacious as the intravenous route of administration, even with highly emetogenic chemotherapy. 相似文献
42.
43.
44.
45.
Trifluoroethanol (TFE) is often used to increase the helicity of peptides to make them usable as models of helices in proteins. We have measured helix propensities for all 20 amino acids in water and two concentrations of trifluoroethanol, 15 and 40% (v/v) using, as a model system, a peptide derived from the sequence of the alpha-helix of ribonuclease T1. There are three main conclusions from our studies. (1) TFE alters electrostatic interactions in the ribonuclease T1 helical peptide such that the dependence of the helical content on pH is lost in 40% TFE. (2) Helix propensities measured in 15% TFE correlate well with propensities measured in water, however, the correlation with propensities measured in 40% TFE is significantly worse. (3) Propensities measured in alanine-based peptides and the ribonuclease T1 peptide in TFE show very poor agreement, revealing that TFE greatly increases the effect of sequence context. 相似文献
46.
47.
48.
Formulating middle-phase microemulsions using mixed anionic and cationic surfactant systems 总被引:1,自引:0,他引:1
T.?Doan E.?Acosta J.?F.?Scamehorn D.?A.?SabatiniEmail author 《Journal of surfactants and detergents》2003,6(3):215-224
Although mixtures of anionic and cationic surfactants can show great synergism, their potential to precipitate and form liquid
crystals has limited their use. Previous studies have shown that alcohol addition can prevent liquid crystal formation, thereby
allowing formation of middle-phase microemulsions with mixed anionic-cationic systems. This research investigates the role
of surfactant selection in designing alcohol-free anionic-cationic microemulsions. Microemulsion phase behavior was studied
for three anionic-cationic surfactant systems and three oils of widely varying hydrophobicity [trichloroethylene (TCE), hexane,
and n-hexadecane]. Consistent with our hypothesis, using a branched surfactant and surfactants with varying tail length allowed
us to form alcohol-free middle-phase microemulsion using mixed anionic-cationic systems (i.e., liquid crystals did not form).
The anionic to cationic molar ratio required to form middle-phase microemulsions approached 1∶1 for univalent surfactants
as oil hydrophobicity increased (i.e., TCE to hexane to n-hexadecane); even for these equimolar systems, liquid crystal formation was avoided. To test the use of these anionic-cationic
surfactant mixtures in surfactant-enhanced subsurface remediation, we performed soil column studies: Greater than 95% of the
oil was extracted in 2.5 pore volumes using an anionic-rich surfactant system. By contrast, cationic-rich systems performed
very poorly (<1% oil removal), reflecting significant losses of the cationic-rich surfactant system in the porous media. The
results thus suggest that, when properly designed, anionic-rich mixtures of anionic and cationic surfactants can be efficient
for environmental remediation. By corollary, other industrial applications and consumer products should also find these mixtures
advantageous. 相似文献
49.
VM Ponomarenko 《Canadian Metallurgical Quarterly》1995,(5-6):12-15
An assessment is submitted of morbidity rates and physical development of children aged under 14, residing in the territories being monitored after the Chernobyl Power Plant accident. A high level of disharmony in physical development of the children examined was recordable, as was an excess in morbidity of both general and separate classes of disease entities among the pediatric population having been victims of the Chernobyl accident, as compared to that in relatively "clean" areas and in Ukraine as a whole. 相似文献
50.
Helicase II (uvrD gene product) and helicase IV (helD gene product) have been shown previously to be involved in the RecF pathway of recombination. To better understand the role of these two proteins in homologous recombination in the RecF pathway [recBCsbcB(C) background, we investigated the interactions between helD, uvrD and the following RecF pathway genes: recF, recO, recN and ruvAB. We observed synergistic interactions between uvrD ant the recF, recN, recO and recG genes in both conjugational recombination and the repair of methylmethane sulfonate (MMS)-induced DNA damage. No synergistic interactions were detected between helD and the recF, recO and regN genes when conjugational recombination was analyzed. We did, however, detect synergistic interactions between helD and recF/recO in recombinational repair. Surprisingly, the uvrD deletion completely suppressed the phenotype of a ruvB mutation in a recBCsbcB(C) background. Both conjugational recombination efficiency and MMS-damaged DNA repair proficiency returned to wild-type levels in the deltauvrDruvB9 double mutant. Suppression of the effects of the ruvB mutation by a uvrD deletion was dependent on the recG and recN genes and not dependent on the recF/O/R genes. These data are discussed in the context of two "RecF" homologous recombination pathways operating in a recBCsbcB(C) strain background. 相似文献