全文获取类型
收费全文 | 5873篇 |
免费 | 8篇 |
国内免费 | 1篇 |
专业分类
综合类 | 1篇 |
化学工业 | 30篇 |
金属工艺 | 5篇 |
机械仪表 | 1篇 |
建筑科学 | 1篇 |
矿业工程 | 2篇 |
能源动力 | 1篇 |
轻工业 | 18篇 |
无线电 | 3篇 |
一般工业技术 | 11篇 |
冶金工业 | 5806篇 |
自动化技术 | 3篇 |
出版年
2020年 | 4篇 |
2019年 | 1篇 |
2018年 | 2篇 |
2017年 | 4篇 |
2016年 | 3篇 |
2015年 | 1篇 |
2014年 | 4篇 |
2013年 | 3篇 |
2012年 | 2篇 |
2011年 | 3篇 |
2010年 | 4篇 |
2008年 | 2篇 |
2007年 | 5篇 |
2006年 | 4篇 |
2005年 | 3篇 |
2004年 | 6篇 |
2003年 | 12篇 |
2002年 | 1篇 |
2000年 | 2篇 |
1999年 | 184篇 |
1998年 | 1915篇 |
1997年 | 1096篇 |
1996年 | 701篇 |
1995年 | 377篇 |
1994年 | 275篇 |
1993年 | 357篇 |
1992年 | 42篇 |
1991年 | 42篇 |
1990年 | 53篇 |
1989年 | 44篇 |
1988年 | 36篇 |
1987年 | 38篇 |
1986年 | 35篇 |
1985年 | 44篇 |
1984年 | 1篇 |
1983年 | 9篇 |
1982年 | 19篇 |
1981年 | 37篇 |
1980年 | 52篇 |
1979年 | 2篇 |
1978年 | 14篇 |
1977年 | 129篇 |
1976年 | 291篇 |
1975年 | 13篇 |
1974年 | 1篇 |
1973年 | 2篇 |
1972年 | 1篇 |
1965年 | 1篇 |
1963年 | 1篇 |
1955年 | 4篇 |
排序方式: 共有5882条查询结果,搜索用时 15 毫秒
331.
332.
KS Armour BJ Clatworthy AR Bean JE Wells AM Clarke 《Canadian Metallurgical Quarterly》1997,110(1057):462-465
AIMS: To establish trends in frequency of serious spinal cord injuries in rugby and rugby league over a 20 year period and to elucidate patterns of injury from retrospective analysis of cases admitted to New Zealand's two spinal injuries units. METHODS: A detailed survey of unit records with follow-up of selected patients; statistical analysis of data. RESULTS: During the 20 years 1976 to 1995, 119 rugby and 22 rugby league players (total 141) were admitted to New Zealand's two spinal injuries units suffering serious spinal injuries and 47 of these became permanently confined to wheelchairs. There was a steady increase in frequency throughout the period studied. Of the injuries 83% occurred in forwards and 17% in backs. In rugby it was the scrum which produced most injuries, and in rugby league it was the tackle. The early season month of April produced most spinal injuries. In the eighteen months since intense compulsory educational programmes on safety were introduced by the New Zealand Rugby Union there have been no serious spinal cord injuries from rugby scrums. CONCLUSION: Contrary to widespread belief, there has not been a decrease in spinal cord injuries in rugby following rule changes in the mid 1980s. The information produced by this retrospective study has been an effective educational platform to make rugby and rugby league safer. 相似文献
333.
334.
335.
336.
337.
Cheryl AM Anderson Scarlett Bellamy Mindy Figures Charnita Zeigler-Johnson Mohamed Jalloh Elaine Spangler Margerie Coomes Serigne Gueye Timothy R Rebbeck 《Nutrition journal》2010,9(1):7
The aim of this work is to identify major food sources and dietary constituents of Senegalese adults. We conducted a cross-sectional study, using a single 24-hour dietary recall interview. Foods were classified into food groups based on similarities in nutrient content or use. Food groups included foods consumed individually, or as part of food mixtures such as stews, soups, or sandwiches. Median consumption (amount/day) of each food was determined and examined by relevant subgroups. Participants were 50 healthy Senegalese men, aged 20-62 years recruited at the Hôpital Général de Grand Yoff in Dakar, Senegal and from Sendou village, a rural area outside Dakar. A total of 90 foods and beverages were identified and classified into 11 groups. Sixty-five percent of foods identified could be classified as meats, grains, or fruits/vegetables. Fruits and vegetables comprised 42% (38/90) of all foods; meats 12% (11/90); and grains 11% (10/90). Sauces (6%, 5/90), sweets (4%, 4/90), and desserts (4%, 4/90) were also reported. The most common fruits/vegetables reported were potato, carrot, mango, and lettuce; commonly reported grains were bread and rice; and commonly reported meats were fish, beef, and ox. There were no differences in reported daily intake of each food by age, ethnicity, education, or residence. Most foods reported were traditional to the Senegalese diet, despite the increasing availability of Western foods in Senegal. 相似文献
338.
A seminested PCR assay, based on the amplification of the pneumococcal pbp1A gene, was developed for the detection of penicillin resistance in clinical isolates of Streptococcus pneumoniae. The assay was able to differentiate between intermediate (MICs = 0.25 to 0.5 microgram/ml) and higher-level (MICs = >/=1 microgram/ml) resistance. Two species-specific primers, 1A-1 and 1A-2, which amplified a 1,043-bp region of the pbp1A penicillin-binding region, were used for pneumococcal detection. Two resistance primers, 1A-R1 and 1A-R2, were designed to bind to altered areas of the pbp1A gene which, together with the downstream primer 1A-2, amplify DNA from isolates with penicillin MICs of >/=0.25 and >/=1 microgram/ml, respectively. A total of 183 clinical isolates were tested with the pbp1A assay. For 98.3% (180 of 183) of these isolates, the PCR results obtained were in agreement with the MIC data. The positive and negative predictive values of the assay were 100 and 91%, respectively, for detecting strains for which the MICs were >/=0.25 microgram/ml and were both 100% for strains for which the MICs were >/=1 microgram/ml. 相似文献
339.
G Gaidano D Capello AM Cilia A Gloghini T Perin S Quattrone A Migliazza F Lo Coco G Saglio V Ascoli A Carbone 《Canadian Metallurgical Quarterly》1999,24(1):16-23
A new type of antimicrobial peptide, snakin-1 (SN1), has been isolated from potato tubers and found to be active, at concentrations < 10 microM, against bacterial and fungal pathogens from potato and other plant species. The action of SN1 and potato defensin PTH1 was synergistic against the bacterium Clavibacter michiganensis subsp. sepedonicus and additive against the fungus Botrytis cinerea. Snakin-1 causes aggregation of both gram-positive and gram-negative bacteria. The peptide has 63 amino acid residues (M(r) 6,922), 12 of which are cysteines, and is unrelated to any previously isolated protein, although it is homologous to amino acid sequences deduced from cloned cDNAs that encode gibberellin-inducible mRNAs and has some sequence motifs in common with kistrin and other hemotoxic snake venoms. A degenerate oligonucleotide probe based on the internal sequence CCEECKC has been used to clone an SN1 cDNA. With the cDNA used as probe, one copy of the StSN1 gene per haploid genome has been estimated and expression of the gene has been detected in tubers, stems, axillary buds, and young floral buds. Expression levels in petals and carpels from fully developed flowers were much higher than in sepals and stamens. The expression pattern of gene StSN1 suggests that protein SN1 may be a component of constitutive defense barriers, especially those of storage and reproductive plant organs. 相似文献
340.
T Knubovets JJ Osterhout PJ Connolly AM Klibanov 《Canadian Metallurgical Quarterly》1999,96(4):1262-1267
Hen egg-white lysozyme dissolved in glycerol containing 1% water was studied by using CD and amide proton exchange monitored by two-dimensional 1H NMR. The far- and near-UV CD spectra of the protein showed that the secondary and tertiary structures of lysozyme in glycerol were similar to those in water. Thermal melting of lysozyme in glycerol followed by CD spectral changes indicated unfolding of the tertiary structure with a Tm of 76.0 +/- 0.2 degreesC and no appreciable loss of the secondary structure up to 85 degreesC. This is in contrast to the coincident denaturation of both tertiary and secondary structures with Tm values of 74.8 +/- 0.4 degreesC and 74.3 +/- 0.7 degreesC, respectively, under analogous conditions in water. Quenched amide proton exchange experiments revealed a greater structural protection of amide protons in glycerol than in water for a majority of the slowly exchanging protons. The results point to a highly ordered, native-like structure of lysozyme in glycerol, with the stability exceeding that in water. 相似文献