全文获取类型
收费全文 | 540523篇 |
免费 | 8482篇 |
国内免费 | 1129篇 |
专业分类
电工技术 | 9840篇 |
综合类 | 828篇 |
化学工业 | 85961篇 |
金属工艺 | 18848篇 |
机械仪表 | 15583篇 |
建筑科学 | 13478篇 |
矿业工程 | 2249篇 |
能源动力 | 13233篇 |
轻工业 | 55503篇 |
水利工程 | 4976篇 |
石油天然气 | 8223篇 |
武器工业 | 46篇 |
无线电 | 60458篇 |
一般工业技术 | 100511篇 |
冶金工业 | 102770篇 |
原子能技术 | 10489篇 |
自动化技术 | 47138篇 |
出版年
2021年 | 4888篇 |
2020年 | 3668篇 |
2019年 | 4706篇 |
2018年 | 7991篇 |
2017年 | 7734篇 |
2016年 | 8191篇 |
2015年 | 5622篇 |
2014年 | 9008篇 |
2013年 | 25578篇 |
2012年 | 14469篇 |
2011年 | 18783篇 |
2010年 | 14866篇 |
2009年 | 16496篇 |
2008年 | 17172篇 |
2007年 | 17049篇 |
2006年 | 14953篇 |
2005年 | 13473篇 |
2004年 | 13050篇 |
2003年 | 12649篇 |
2002年 | 12486篇 |
2001年 | 12268篇 |
2000年 | 11839篇 |
1999年 | 12155篇 |
1998年 | 29984篇 |
1997年 | 21540篇 |
1996年 | 16631篇 |
1995年 | 12720篇 |
1994年 | 11474篇 |
1993年 | 11175篇 |
1992年 | 8412篇 |
1991年 | 7910篇 |
1990年 | 7980篇 |
1989年 | 7741篇 |
1988年 | 7456篇 |
1987年 | 6362篇 |
1986年 | 6532篇 |
1985年 | 7567篇 |
1984年 | 6980篇 |
1983年 | 6455篇 |
1982年 | 5982篇 |
1981年 | 6171篇 |
1980年 | 5880篇 |
1979年 | 5642篇 |
1978年 | 5493篇 |
1977年 | 6533篇 |
1976年 | 8693篇 |
1975年 | 4813篇 |
1974年 | 4580篇 |
1973年 | 4697篇 |
1972年 | 3843篇 |
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
91.
Pavel Strunz Debashis Mukherji Přemysl Beran Ralph Gilles Lukas Karge Michael Hofmann Markus Hoelzel Joachim Rösler Gergely Farkas 《Metals and Materials International》2018,24(5):934-944
An addition of boron largely increases the ductility in polycrystalline high-temperature Co–Re alloys. Therefore, the effect of boron on the alloy structural characteristics is of high importance for the stability of the matrix at operational temperatures. Volume fractions of ε (hexagonal close-packed—hcp), γ (face-centered cubic—fcc) and σ (Cr2Re3 type) phases were measured at ambient and high temperatures (up to 1500 °C) for a boron-containing Co–17Re–23Cr alloy using neutron diffraction. The matrix phase undergoes an allotropic transformation from ε to γ structure at high temperatures, similar to pure cobalt and to the previously investigated, more complex Co–17Re–23Cr–1.2Ta–2.6C alloy. It was determined in this study that the transformation temperature depends on the boron content (0–1000 wt. ppm). Nevertheless, the transformation temperature did not change monotonically with the increase in the boron content but reached a minimum at approximately 200 ppm of boron. A probable reason is the interplay between the amount of boron in the matrix and the amount of σ phase, which binds hcp-stabilizing elements (Cr and Re). Moreover, borides were identified in alloys with high boron content. 相似文献
92.
Biological information is stored in DNA, RNA and protein sequences, which can be understood as genotypes that are translated into phenotypes. The properties of genotype–phenotype (GP) maps have been studied in great detail for RNA secondary structure. These include a highly biased distribution of genotypes per phenotype, negative correlation of genotypic robustness and evolvability, positive correlation of phenotypic robustness and evolvability, shape-space covering, and a roughly logarithmic scaling of phenotypic robustness with phenotypic frequency. More recently similar properties have been discovered in other GP maps, suggesting that they may be fundamental to biological GP maps, in general, rather than specific to the RNA secondary structure map. Here we propose that the above properties arise from the fundamental organization of biological information into ‘constrained'' and ‘unconstrained'' sequences, in the broadest possible sense. As ‘constrained'' we describe sequences that affect the phenotype more immediately, and are therefore more sensitive to mutations, such as, e.g. protein-coding DNA or the stems in RNA secondary structure. ‘Unconstrained'' sequences, on the other hand, can mutate more freely without affecting the phenotype, such as, e.g. intronic or intergenic DNA or the loops in RNA secondary structure. To test our hypothesis we consider a highly simplified GP map that has genotypes with ‘coding'' and ‘non-coding'' parts. We term this the Fibonacci GP map, as it is equivalent to the Fibonacci code in information theory. Despite its simplicity the Fibonacci GP map exhibits all the above properties of much more complex and biologically realistic GP maps. These properties are therefore likely to be fundamental to many biological GP maps. 相似文献
93.
94.
95.
Karolina M. Wójciak Dariusz M. Stasiak Joanna Stadnik Karolina Ferysiuk Anna Kononiuk 《International Journal of Food Science & Technology》2019,54(1):75-83
In this study, the influence of sonication time on the biogenic amines formation as a critical point in uncured dry-fermented beef manufacturing was studied. Samples of musculus semimembranosus were sonicated at different times (5 and 10 min) using ultrasound cold bath (4 °C) in acid whey (US 40 kHz and acoustic power 480 W). The effect of sonication on biogenic amine (BA) formation was investigated during 93 days of ripening period. Other parameters (pH value, water activity, microbial counts) that might provide further information on the product under study were also determined. The use of ultrasound during beef marinating in acid whey has a positive effect on retarding histamine (HIS), cadaverine (CAD), tyramine (TYR) and putrescine (PUT) formation. Moreover, the sonication treatment did not inhibit the growth of lactic acid bacteria (LAB) in dry-fermented beef during the whole ripening period. The pathogen bacteria (Staphylococcus aureus, Clostridium sp., Listeria monocytogenes) were not detected in all samples neither after 31 nor after 93 days of ripening period. 相似文献
96.
97.
A. E. Kudryashov Zh. V. Eremeeva E. A. Levashov V. Yu. Lopatin A. V. Sevost’yanova E. I. Zamulaeva 《Surface Engineering and Applied Electrochemistry》2018,54(5):437-445
Electrospark treatment of OT4-1 titanium alloy was performed sequentially with a STIM-20N hard-alloy electrode (TiC–20% Ni) and carbon-containing material (graphite and carbon-based composite materials). Kinetics of the mass transfer of the hard-alloy electrode was studied. The cathode mass loss during the first minute of the treatment was established. The kinetics results were processed using the methods of mathematical statistics. The erosion resistance of the applied carbon-containing materials was determined. Phase composition and relief of the coatings formed were analyzed. It was found that the application of the carbon-containing material increases the content of refractory phases in the coatings. Increase in the time of the treatment using the carbon-containing materials decreases the roughness of the coatings. 相似文献
98.
99.
Alfredo M. Gravagnuolo Eden Morales‐Narváez Charlene Regina Santos Matos Sara Longobardi Paola Giardina Arben Merkoçi 《Advanced functional materials》2015,25(38):6084-6092
Class I hydrophobin Vmh2, a peculiar surface active and versatile fungal protein, is known to self‐assemble into chemically stable amphiphilic films, to be able to change wettability of surfaces, and to strongly adsorb other proteins. Herein, a fast, highly homogeneous and efficient glass functionalization by spontaneous self‐assembling of Vmh2 at liquid–solid interfaces is achieved (in 2 min). The Vmh2‐coated glass slides are proven to immobilize not only proteins but also nanomaterials such as graphene oxide (GO) and quantum dots (QDs). As models, bovine serum albumin labeled with Alexa 555 fluorophore, anti‐immunoglobulin G antibodies, and cadmium telluride QDs are patterned in a microarray fashion in order to demonstrate functionality, reproducibility, and versatility of the proposed substrate. Additionally, a GO layer is effectively and homogeneously self‐assembled onto the studied functionalized surface. This approach offers a quick and simple alternative to immobilize nanomaterials and proteins, which is appealing for new bioanalytical and nanobioenabled applications. 相似文献
100.