全文获取类型
收费全文 | 215310篇 |
免费 | 3506篇 |
国内免费 | 631篇 |
专业分类
电工技术 | 3623篇 |
综合类 | 165篇 |
化学工业 | 32800篇 |
金属工艺 | 8356篇 |
机械仪表 | 6358篇 |
建筑科学 | 5415篇 |
矿业工程 | 1331篇 |
能源动力 | 5621篇 |
轻工业 | 19518篇 |
水利工程 | 2415篇 |
石油天然气 | 4080篇 |
武器工业 | 8篇 |
无线电 | 23901篇 |
一般工业技术 | 42612篇 |
冶金工业 | 39673篇 |
原子能技术 | 5171篇 |
自动化技术 | 18400篇 |
出版年
2021年 | 2166篇 |
2020年 | 1501篇 |
2019年 | 1946篇 |
2018年 | 3189篇 |
2017年 | 3215篇 |
2016年 | 3371篇 |
2015年 | 2223篇 |
2014年 | 3687篇 |
2013年 | 9985篇 |
2012年 | 6015篇 |
2011年 | 8118篇 |
2010年 | 6379篇 |
2009年 | 7108篇 |
2008年 | 7188篇 |
2007年 | 7150篇 |
2006年 | 6133篇 |
2005年 | 5693篇 |
2004年 | 5373篇 |
2003年 | 5230篇 |
2002年 | 4835篇 |
2001年 | 4875篇 |
2000年 | 4796篇 |
1999年 | 4932篇 |
1998年 | 12259篇 |
1997年 | 8644篇 |
1996年 | 6779篇 |
1995年 | 4889篇 |
1994年 | 4460篇 |
1993年 | 4264篇 |
1992年 | 3290篇 |
1991年 | 3159篇 |
1990年 | 2938篇 |
1989年 | 3015篇 |
1988年 | 2881篇 |
1987年 | 2452篇 |
1986年 | 2356篇 |
1985年 | 2768篇 |
1984年 | 2544篇 |
1983年 | 2389篇 |
1982年 | 2141篇 |
1981年 | 2261篇 |
1980年 | 2066篇 |
1979年 | 2149篇 |
1978年 | 2149篇 |
1977年 | 2424篇 |
1976年 | 3271篇 |
1975年 | 1854篇 |
1974年 | 1776篇 |
1973年 | 1796篇 |
1972年 | 1459篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
41.
Simple Sequence Repeat Markers in Genetic Divergence and Marker-Assisted Selection of Rice Cultivars: A Review 总被引:2,自引:0,他引:2
Shubhneet Kaur Manab B. Bera Varinder Kaur 《Critical reviews in food science and nutrition》2015,55(1):41-49
Sequencing of rice genome has facilitated the understanding of rice evolution and has been utilized extensively for mining of DNA markers to facilitate marker-assisted breeding. Simple sequence repeat (SSR) markers that are tandemly repeated nucleotide sequence motifs flanked by unique sequences are presently the maker of choice in rice improvement due to their abundance, co-dominant inheritance, high levels of allelic diversity, and simple reproducible assay. The current level of genome coverage by SSR markers in rice is sufficient to employ them for genotype identification and marker-assisted selection in breeding for mapping of genes and quantitative trait loci analysis. This review provides comprehensive information on the mapping and applications of SSR markers in investigation of rice cultivars to study their genetic divergence and marker-assisted selection of important agronomic traits. 相似文献
42.
43.
Nicholas Caffes David B. Kurland Volodymyr Gerzanich J. Marc Simard 《International journal of molecular sciences》2015,16(3):4973-4984
Ischemic and hemorrhagic strokes are associated with severe functional disability and high mortality. Except for recombinant tissue plasminogen activator, therapies targeting the underlying pathophysiology of central nervous system (CNS) ischemia and hemorrhage are strikingly lacking. Sur1-regulated channels play essential roles in necrotic cell death and cerebral edema following ischemic insults, and in neuroinflammation after hemorrhagic injuries. Inhibiting endothelial, neuronal, astrocytic and oligodendroglial sulfonylurea receptor 1–transient receptor potential melastatin 4 (Sur1–Trpm4) channels and, in some cases, microglial KATP (Sur1–Kir6.2) channels, with glibenclamide is protective in a variety of contexts. Robust preclinical studies have shown that glibenclamide and other sulfonylurea agents reduce infarct volumes, edema and hemorrhagic conversion, and improve outcomes in rodent models of ischemic stroke. Retrospective studies suggest that diabetic patients on sulfonylurea drugs at stroke presentation fare better if they continue on drug. Additional laboratory investigations have implicated Sur1 in the pathophysiology of hemorrhagic CNS insults. In clinically relevant models of subarachnoid hemorrhage, glibenclamide reduces adverse neuroinflammatory and behavioral outcomes. Here, we provide an overview of the preclinical studies of glibenclamide therapy for CNS ischemia and hemorrhage, discuss the available data from clinical investigations, and conclude with promising preclinical results that suggest glibenclamide may be an effective therapeutic option for ischemic and hemorrhagic stroke. 相似文献
44.
45.
46.
Metallurgist - We consider domestic and foreign standards for rolled metals used in bridge building. Domestic standards contain elevated requirements to the reliability of rolled metals in terms of... 相似文献
47.
Giorgio Benedek Joseph R. Manson Salvador Miret-Artés 《Advanced materials (Deerfield Beach, Fla.)》2020,32(25):2002072
Atom scattering is becoming recognized as a sensitive probe of the electron–phonon interaction parameter λ at metal and metal-overlayer surfaces. Here, the theory is developed, linking λ to the thermal attenuation of atom scattering spectra (in particular, the Debye–Waller factor), to conducting materials of different dimensions, from quasi-1D systems such as W(110):H(1 × 1) and Bi(114), to quasi-2D layered chalcogenides, and high-dimensional surfaces such as quasicrystalline 2ML-Ba(0001)/Cu(001) and d-AlNiCo(00001). Values of λ obtained using He atoms compare favorably with known values for the bulk materials. The corresponding analysis indicates in addition, the number of layers contributing to the electron–phonon interaction, which is measured in an atom surface collision. 相似文献
48.
Kolmachikhina E. B. Sviridov A.V. Naumov K. D. 《Russian Journal of Non-Ferrous Metals》2020,61(5):488-493
Russian Journal of Non-Ferrous Metals - This article is devoted to the influence of sodium lignosulfonate (SL), anionic surfactants (sodium dodecylsulfate (SDS), sodium dodecylbenzene sulfonate... 相似文献
49.
Isaac Isarn Leïla Bonnaud Lluís Massagus ngels Serra Francesc Ferrando 《Polymer International》2020,69(3):280-290
The enhancement of the thermal conductivity, keeping the electrical insulation, of epoxy thermosets through the addition of pristine and oxidized carbon nanotubes (CNTs) and microplatelets of boron nitride (BN) was studied. Two different epoxy resins were selected: a cycloaliphatic (ECC) epoxy resin and a glycidylic (DGEBA) epoxy resin. The characteristics of the composites prepared were evaluated and compared in terms of thermal, thermomechanical, rheological and electrical properties. Two different dispersion methods were used in the addition of pristine and oxidized CNTs depending on the type of epoxy resin used. Slight changes in the kinetics of the curing reaction were observed in the presence of the fillers. The addition of pristine CNTs led to a greater enhancement of the mechanical properties of the ECC composite whereas the oxidized CNTs presented a greater effect in the DGEBA matrix. The addition of CNTs alone led to a marked decrease of the electrical resistivity of the composites. Nevertheless, in the presence of BN, which is an electrically insulating material, it was possible to increase the proportion of pristine CNTs to 0.25 wt% in the formulation without deterioration of the electrical resistivity. A small but significant synergic effect was determined when both fillers were added together. Improvements of about 750% and 400% in thermal conductivity were obtained in comparison to the neat epoxy matrix for the ECC and DGEBA composites, respectively. © 2019 Society of Chemical Industry 相似文献
50.
Esteban Vera Pingitore María Silvina Juárez Tomás Birgitt Wiese 《Drug development and industrial pharmacy》2015,41(6):942-952
Context: The administration of pharmabiotics is a promising alternative to antimicrobial drugs for the treatment and/or prevention of female urogenital infections.Objective: To design pharmabiotic formulations including bioactive ingredients of microbial origin combined with non-microbial substances and then to evaluate the stability of the combinations during freeze-drying and storage.Materials and methods: Different formulations including Lactobacillus gasseri CRL 1263, Lactobacillus salivarius CRL 1328, salivaricin CRL 1328 (a bacteriocin) and non-microbial compounds (lactose, inulin and ascorbic acid) were assayed, and the ingredients were freeze-dried together or separately. The formulations were stored in gelatin capsules at 4?°C for 360?d.Results: The viability of lactobacilli was affected to different extents depending on the strains and on the formulations assayed. L. salivarius and ascorbic acid were successfully combined only after the freeze-drying process. Salivaricin activity was not detected in formulations containing L. gasseri. However, when combined with ascorbic acid, lactose, inulin or L. salivarius, the bacteriocin maintained its activity for 360?d. The selected microorganisms proved to be compatible for their inclusion in multi-strain formulations together with lactose, inulin and ascorbic acid. Salivaricin could be included only in a L. salivarius CRL 1328 single-strain formulation together with non-microbial substances.Conclusions: This study provides new insights into the design of urogenital pharmabiotics combining beneficial lactobacilli, salivaricin CRL 1328 and compounds with different functionalities. 相似文献