全文获取类型
收费全文 | 2569篇 |
免费 | 5篇 |
专业分类
电工技术 | 20篇 |
综合类 | 1篇 |
化学工业 | 74篇 |
金属工艺 | 5篇 |
机械仪表 | 9篇 |
建筑科学 | 18篇 |
矿业工程 | 1篇 |
能源动力 | 29篇 |
轻工业 | 52篇 |
水利工程 | 6篇 |
石油天然气 | 3篇 |
无线电 | 78篇 |
一般工业技术 | 134篇 |
冶金工业 | 2050篇 |
原子能技术 | 22篇 |
自动化技术 | 72篇 |
出版年
2021年 | 8篇 |
2020年 | 9篇 |
2019年 | 7篇 |
2018年 | 10篇 |
2017年 | 8篇 |
2016年 | 13篇 |
2015年 | 4篇 |
2014年 | 13篇 |
2013年 | 35篇 |
2012年 | 15篇 |
2011年 | 21篇 |
2010年 | 19篇 |
2009年 | 33篇 |
2008年 | 34篇 |
2007年 | 16篇 |
2006年 | 25篇 |
2005年 | 21篇 |
2004年 | 21篇 |
2003年 | 25篇 |
2002年 | 24篇 |
2001年 | 29篇 |
2000年 | 15篇 |
1999年 | 69篇 |
1998年 | 663篇 |
1997年 | 353篇 |
1996年 | 236篇 |
1995年 | 146篇 |
1994年 | 92篇 |
1993年 | 121篇 |
1992年 | 27篇 |
1991年 | 28篇 |
1990年 | 34篇 |
1989年 | 33篇 |
1988年 | 21篇 |
1987年 | 21篇 |
1986年 | 25篇 |
1985年 | 41篇 |
1984年 | 6篇 |
1983年 | 7篇 |
1982年 | 22篇 |
1981年 | 9篇 |
1980年 | 15篇 |
1978年 | 8篇 |
1977年 | 59篇 |
1976年 | 99篇 |
1974年 | 4篇 |
1973年 | 3篇 |
1969年 | 3篇 |
1968年 | 5篇 |
1966年 | 4篇 |
排序方式: 共有2574条查询结果,搜索用时 15 毫秒
51.
52.
Modeling biomass as a renewable energy source poses many challenges with respect to feedstock variability, which are difficult to account for. It is found that at the preliminary stages of energy planning, heating value and moisture content of the feedstock are the most important factors. In addition, the effects of harvesting, transportation and storage are found to be significant even though they are often overlooked. Using the gathered information a biomass module for energy planning is created and integrated to H2RES, a renewable energy planning program. Using this excel based software, a case study for a wood processing factory is performed, using the waste wood as feedstock. Comparing various scenarios, it is concluded that using a combination of solid oxide fuel cells, solar panels and steam turbines can satisfy the factories energy requirements with excess sold to the grid. 相似文献
53.
To detect new genetic variation in human plasma proteins, a panel of 63 radioactive substances were screened as potential radioligands using polyacrylamide gel electrophoresis (PAGE) and autoradiography. Vitamins, hormones, drugs, amino acids, purines, pyrimidines, sugars and lipids labeled with 14C or other radionuclides were among those substances tested. A majority bound to albumin and a smaller fraction to prealbumins and lipoproteins. Several vitamins and hormones bound to specific alpha and beta globulins. (1) Electrophoretic polymorphisms of vitamin D-binding protein (group-specific component), a vitamin B12-binding protein (transcobalamin II), and thyroxine-binding alpha-globulin are described elsewhere. (2) Testosterone-binding beta-globulin (TeBG) showed an electrophoretic polymorphism in Caucasians and a possible deficiency allele. (3) Transcortin showed an electrophoretic doublet in all persons tested but no electrophoretic variation. (4) A protein binding derivative of norepinephrine or epinephrine was identified as transferrin. (5) A nonpolymorphic protein running cathodal to albumin and binding a derivative of riboflavin was tentatively identified as a fraction of albumin with mobility altered as a result of interaction with the ligand. 相似文献
54.
55.
Fistulas between the abdominal aorta and renal vein are exceedingly rare. Diagnostic delays are not unusual. Correction can be extremely difficult because of anatomical distortion and size of the arterialized veins. A young woman with such a fistula following a gunshot wound is presented. Four years following injury, the fistula was repaired successfully during intentional arrest of the circulation for 7 minutes. This was accomplished with deep hypothermia and cardiopulmonary bypass. No serious problems occurred during the operation. The patient tolerated the procedure well and has been relieved of her symptoms completely. Most patients with traumatic or spontaneous arteriovenous fistulas can be managed safely and effectively by conventional operative techniques. In selected situations, the risk of total circulatory arrest and deep hypothermia may be less than the risk of uncontrollable bleeding inherent in conventional techniques. Suggested indications for use of total circulatory arrest in vascular surgery are (1) inability to achieve vascular control by more conventional means, (2) massive distention of regional veins as occurrs in well established fistulas of the trunk, (3) one or more prior corrective attempts with use of conventional techniques, and (4) anticipated anatomical distortion and/or multiple abnormal vascular communications. This technique is a valuable approach to the correction of otherwise inoperable cardiovascular lesions. 相似文献
56.
57.
SP Goller D Schoisswohl M Baron M Parriche CP Kubicek 《Canadian Metallurgical Quarterly》1998,64(9):3202-3208
Cell extracts of Trichoderma reesei exhibited dibasic endopeptidase activity toward the carboxylic side of KR, RR, and PR sequences. This activity was stimulated by the presence of Ca2+ ions and localized in vesicles of low bouyant density; it therefore exhibited some similarity to yeast Kex2. Analytical chromatofocusing revealed a single peak of activity. The dibasic endopeptidase activity was strongly and irreversibly inhibited in vitro as well as in vivo by 1 mM p-amidinophenylmethylsulfonyl fluoride (pAPMSF) but not by PMSF at concentrations up to 5 mM. We therefore used pAPMSF to study the role of the dibasic endopeptidase in the secretion of protein by T. reesei. Secretion of xylanase I (proprotein processing sequence -R-R- downward arrow-R- downward arrow-A-) and xylanase II (-K-R- downward arrow-Q-) was strongly inhibited by 1 mM pAPMSF, and a larger, unprocessed enzyme form was detected intracellularly under these conditions. Secretion of cellobiohydrolase II (CBH II; -E-R- downward arrow-Q-) was only slightly inhibited by pAPMSF, and no accumulation of unprocessed precursors was detected. In contrast, secretion of CBH I (-R-A- downward arrow-Q-) was stimulated by pAPMSF addition, and a simultaneous decrease in the concentration of intracellular CBH I was detected. Similar experiments were also carried out with a single heterologous protein, ShBLE, the phleomycin-binding protein from Streptoalloteichus hindustanus, fused to a series of model proprotein-processing sequences downstream of the expression signals of the Aspergillus nidulans gpdA promoter. Consistent with the results obtained with homologous proteins, pAPMSF inhibited the secretion of ShBLE with fusions containing dibasic (RK and KR) target sequences, but it even stimulated secretion in fusions to LR, NHA, and EHA target sequences. Addition of 5 mM PMSF, a nonspecific inhibitor of serine protease, nonspecifically inhibited the secretion of heterologous proteins from fusions bearing the NHA and LR targets. These data point to the existence of different endoproteolytic proprotein processing enzymes in T. reesei and demonstrate that dibasic processing is obligatory for the secretion of the proproteins containing this target. 相似文献
58.
This article was prepared and submitted to members of the TMD academic community for their endorsement. A total of 120 people signed an endorsement; their names are available on request. 相似文献
59.
BACKGROUND: Synthetic homopyrimidine peptide nucleic acids (PNAs) can bind complementary targets in double-stranded DNA, generating strand-displacement complexes, and so offering an opportunity to modulate specific gene expression. Several issues remain to be addressed before these attributes can be exploited in vivo, however. RESULTS: The kinetics of the interaction between a homopyrimidine PNA and a complementary homopurine target on double-stranded DNA were analyzed in the presence or absence of a preformed strand-displacement complex proximal to the target. The complex was established under low salt conditions by the binding of a different homopyrimidine PNA to a target situated adjacent to the first PNA target. These two targets were placed next to each other on opposite strands at distances of 0, 2, 4 and 8 base pairs apart. The presence of a preformed strand-displacement complex near the target accelerates the binding of PNA to double-stranded DNA in a salt-dependent manner. The influence of salt on the binding rates was also examined. The binding rate is increased by a factor of 1 x exp(70[NaCl]), that is, 16-fold at 40 mM NaCl and more than 10(4)-fold if extrapolated to 140 mM NaCl. This effect is significantly reduced if the two targets are 2 base pairs apart and completely absent if the distance is 4 base pairs or more. CONCLUSIONS: The perturbation of the DNA helix imposed by a PNA strand-displacement complex only propagates a few base pairs. It is therefore possible to target sites in the immediate vicinity of strand invasion complexes specifically. The results presented have implications for the mechanism of strand displacement and for the application of PNA in a genomic context. 相似文献
60.
Assessment of regional left ventricular long-axis motion with MR velocity mapping in healthy subjects 总被引:1,自引:0,他引:1
SP Karwatowski R Mohiaddin GZ Yang DN Firmin MS Sutton SR Underwood DB Longmore 《Canadian Metallurgical Quarterly》1994,4(2):151-155
We present a case of trichothiodystrophy associated with a hypereosinophilic syndrome. This case had been followed for 30 years. Trichothiodystrophy was characterized by lamellar ichthyosis, hair and nail dystrophies, kyphoscoliosis, congenital luxation of the hip. The hypereosinophilic syndrome was characterized by an itching urticaria-like eruption. Although the patient's general condition had remaining stable for 30 years, during the last year it worsened and the patient suddenly died. The authors discuss about the significance of this association. 相似文献