全文获取类型
收费全文 | 2350篇 |
免费 | 1篇 |
专业分类
电工技术 | 9篇 |
化学工业 | 21篇 |
金属工艺 | 3篇 |
机械仪表 | 2篇 |
建筑科学 | 6篇 |
能源动力 | 1篇 |
轻工业 | 21篇 |
水利工程 | 1篇 |
无线电 | 11篇 |
一般工业技术 | 19篇 |
冶金工业 | 2237篇 |
原子能技术 | 7篇 |
自动化技术 | 13篇 |
出版年
2023年 | 3篇 |
2021年 | 2篇 |
2020年 | 2篇 |
2019年 | 2篇 |
2017年 | 1篇 |
2016年 | 4篇 |
2015年 | 1篇 |
2013年 | 8篇 |
2012年 | 7篇 |
2011年 | 2篇 |
2010年 | 4篇 |
2009年 | 5篇 |
2008年 | 1篇 |
2007年 | 8篇 |
2006年 | 1篇 |
2005年 | 3篇 |
2004年 | 4篇 |
2003年 | 8篇 |
2002年 | 1篇 |
2001年 | 3篇 |
2000年 | 5篇 |
1999年 | 76篇 |
1998年 | 716篇 |
1997年 | 434篇 |
1996年 | 254篇 |
1995年 | 134篇 |
1994年 | 102篇 |
1993年 | 128篇 |
1992年 | 18篇 |
1991年 | 18篇 |
1990年 | 16篇 |
1989年 | 24篇 |
1988年 | 35篇 |
1987年 | 21篇 |
1986年 | 17篇 |
1985年 | 12篇 |
1983年 | 5篇 |
1982年 | 10篇 |
1981年 | 8篇 |
1980年 | 17篇 |
1978年 | 3篇 |
1977年 | 63篇 |
1976年 | 146篇 |
1975年 | 6篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1969年 | 1篇 |
1968年 | 2篇 |
1964年 | 1篇 |
1955年 | 3篇 |
排序方式: 共有2351条查询结果,搜索用时 62 毫秒
101.
EM Burns 《Canadian Metallurgical Quarterly》1976,57(12):48-54, 80
102.
Several viral isolates from ticks (Ornithodoros coriaceus) and from the blood of cattle which aborted after exposure to these ticks were found to be identical by reciprocal cross serum-neutralization tests. Characterization studies indicate that the virus is a member of the Togaviridae family, although specific identification is still incomplete. Whether its natural host is the tick or bovine animals is also unknown. Pregnant cows inoculated with the agent by all conventional parenteral routes, including intrafetal, delivered healthy calves at term. It was concluded, therefore, that it was not a bovine pathogen and that the abortions which occurred after tick-exposure were due to a 2nd agent in O coriaceus ticks which also harbor the virus. While several ciruses believed to be tick-borne have been isolated from cattle in various parts of the world, it is believed that the present report describes the first isolation in the Western Hemisphere for a viral agent from Argasid ticks which has been demonstrated to replicate in cattle. 相似文献
103.
Very low birth weight children at school age: comparison of neonatal management methods 总被引:1,自引:0,他引:1
ES Steiner EM Sanders EC Phillips CR Maddock 《Canadian Metallurgical Quarterly》1980,281(6250):1237-1240
The outcome of 293 infants born to a geographically defined community and weighing 501-1500 g was investigated. Medical intervention in the newborn period had been avoided. Morbidity was assessed at school age. Of the infants, 236 had been live born in the labour ward of this hospital; of these, 117 (49.6%) died in the neonatal period, one (0.4%) died in the first year, four (1.7%) were untraced, 13 (5.5%) had major handicap, 29 (12.3%) had minor handicap, and 72 (30.5%) were considered to be normal. In terms of survival, handicap, and intellectual with that of infants born over the same period (1963-71) in areas where intensive methods of perinatal care were used. These results imply that postnatal survival and potential of infants of very low birth weight are by no means prejudiced when only experienced nursing care is available. 相似文献
104.
P Puigdoménech P Martínez J Palau EM Bradbury C Crane-Robinson 《Canadian Metallurgical Quarterly》1976,65(2):357-363
Proton magnetic resonance and other measurements have been carried out in order to study the behaviour of the lysine-rich histones phi 1 in the sperm chromatin of certain marine invertebrates. Well defined particles (12 S) have been obtained from this chromatin by nuclease treatment. Chromatin solubility as a function of ionic strength shows a relaxation at salt concentrations higher than in the case of calf thymus nucleoprotein. Nuclear magnetic resonance (NMR) studies show that the release of histone from DNA occurs both in chromatin and in the reconstituted complexes at practically the same ionic strength as solubility relaxation. The higher the arginine content of a given phi 1, the higher the ionic strength at which both effects take place. The NMR results demonstrate that arginine residues are bound more strongly than lysine residues. The data overall show that phi 1 histones play a role in the contraction mechanism of sperm chromatin similar to that of H 1 histone in calf thymus chromatin. The highly contracted state of sperm chromatin is directly related to the increased arginine content of the phi 1 histone. 相似文献
105.
Starch gel electrophoresis of 55 donkey serum samples revealed three prealbumin (Pr) phenotypes temporarily designated Pr M, Pr MT and Pr T. The distribution was in agreement with a genetic theory of two codominant alleles of frequencies, PrM = 0.87 and PrT - 0.13. Variation was also observed for proteins migrating with the same rate as the Xh zones in the horse. 相似文献
106.
DJ Birnbach DJ Stein O Murray DM Thys EM Sordillo 《Canadian Metallurgical Quarterly》1998,88(3):668-672
OBJECTIVE: The clinical, mammographic and low grade cytologic features of mucinous carcinoma can make it difficult to diagnose by fine needle aspiration (FNA). Fine needle aspirates of mucinous carcinoma were reviewed with the mammographic findings to improve the diagnostic criteria and specificity for FNA. STUDY DESIGN: All aspirates were reviewed for cytologic criteria and cellularity, atypia and single epithelial cells (SEC). A nuclear grade was assigned to each aspirate. The mammographic findings were correlated with the FNA diagnoses. RESULTS: Forty-five patients with an aspirate and confirmed diagnosis of mucinous carcinoma were identified. The clinical impressions were: benign tissue (5), fibroadenoma (6) and cancer (32). The initial cytologic diagnoses were: adenocarcinoma (32), atypical/suspicious for cancer (11), insufficient (1) and negative (1). The cytologic findings showed smears with increased cellularity (35/45 cases) and minimal atypia. SEC with eccentrically located nuclei and eosinophilic cytoplasm were numerous. The assigned nuclear grade was as follows: grade 1, 16 cases; grade 2, 20 cases; and grade 3, 6 cases. Abundant mucin was present in Papanicolaou-stained slides in 23 cases; focal mucin was observed in 14 cases. The mammograms showed a smoothly outlined to lobulated mass with only slight irregularities identified. CONCLUSION: Mucinous carcinoma has a cytologic pattern that includes increased cellularity, with numerous single cells and abundant mucin. Although the mammographic findings may mimic a benign lesion, in the most patients a specific diagnosis of mucinous carcinoma can be made by FNA. 相似文献
107.
D Averill D Blockus B Brabson J Brom C Jung H Ogren DR Rust M Derrick P Kooijman JS Loos B Musgrave LE Price J Repond K Sugano B Cork C Akerlof J Chapman D Errede MT Ken DI Meyer H Neal D Nitz R Thun R Tschirhart S Abachi P Baringer BG Bylsma R DeBonte D Koltick EH Low RL McIlwain DH Miller CR Ng EI Shibata 《Canadian Metallurgical Quarterly》1989,39(1):123-137
108.
Data were first lactation production and reproduction records initiated from 1958 to 1981 in two experiment station Guernsey herds. Heritability estimates using paternal half sib groups were .24 +/- .12 for milk yield, .27 +/- .12 for fat yield, and .77 +/- .15 for fat percentage. Heritability estimates for reproductive traits ranged from .01 to .04 for number of services, service period, conception rate, and days open, but were higher for days in milk at first breeding (.12) and age at first calving (.13). Except for age at first calving, coefficients of additive genetic variation were larger for reproductive traits than for productive traits. Genetic correlations between measures of production and reproduction were moderate to large and antagonistic, except that the relationship between production and age at first calving was favorable. Breeding value estimates for milk yield and reproduction were negatively correlated for sires with above average breeding values for milk yield. Huge phenotypic variances for reproductive traits masked substantial additive genetic variation for these traits. When all things are considered it seems unwise to ignore reproductive performance in selection programs for dairy cattle. 相似文献
109.
EM Van der Aa IJ Meuwsen AC Boersen AC Wouterse JH Copius Peereboom-Stegeman FG Russel 《Canadian Metallurgical Quarterly》1994,15(3):279-289
The mechanism of uptake of p-aminohippurate (PAH) by syncytial microvillous membrane vesicles of human term placenta was investigated. Initial PAH uptake and efflux were increased in the presence of a pH-gradient and a Cl(-)-gradient, respectively. Forced negative and positive membrane potentials did not influence the uptake, which indicated that the transport is not electrogenic. The pH-dependent increase is probably the result of a higher rate of diffusion due to a lower degree of dissociation of PAH. Because several organic anions failed to transstimulate PAH uptake and FCCP did not decrease the uptake in the presence of an inwardly directed H(+)-gradient, ruling out a PAH/OH- antiport, an anion exchange system does not appear to be present in these membranes. Since electrogenicity and anion exchange seem not to be involved in the Cl(-)-dependent increase, an allosteric effect of Cl- on the transporter might be possible. Various organic anions were able to inhibit pH-stimulated PAH uptake significantly. Kinetic analysis of the probenecid sensitive part of uptake provided further evidence for mediated transport of PAH (Km = 7.4 +/- 2.6 mM and Vmax = 2.0 +/- 0.4 nmol/mg/15 s). Non-inhibitable diffusion accounted for the main part of total transport. Concentration dependent inhibition of PAH transport by probenecid showed a Ki of 2.5 +/- 0.9 mM. It is concluded that human placental syncytial microvillous membrane vesicles possess a low affinity transport mechanism for PAH with low specificity. The importance of this system, for placental excretion of anionic drugs, will depend on the intrasyncytial concentration of these drugs, caused by the transport across the basal membrane. 相似文献
110.
Identification of a gene that causes primary open angle glaucoma 总被引:3,自引:0,他引:3
EM Stone JH Fingert WL Alward TD Nguyen JR Polansky SL Sunden D Nishimura AF Clark A Nystuen BE Nichols DA Mackey R Ritch JW Kalenak ER Craven VC Sheffield 《Canadian Metallurgical Quarterly》1997,275(5300):668-670
Glaucoma is a major cause of blindness and is characterized by progressive degeneration of the optic nerve and is usually associated with elevated intraocular pressure. Analyses of sequence tagged site (STS) content and haplotype sharing between families affected with chromosome 1q-linked open angle glaucoma (GLC1A) were used to prioritize candidate genes for mutation screening. A gene encoding a trabecular meshwork protein (TIGR) mapped to the narrowest disease interval by STS content and radiation hybrid mapping. Thirteen glaucoma patients were found to have one of three mutations in this gene (3.9 percent of the population studied). One of these mutations was also found in a control individual (0.2 percent). Identification of these mutations will aid in early diagnosis, which is essential for optimal application of existing therapies. 相似文献