全文获取类型
收费全文 | 5906篇 |
免费 | 413篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 41篇 |
综合类 | 1篇 |
化学工业 | 1142篇 |
金属工艺 | 88篇 |
机械仪表 | 99篇 |
建筑科学 | 197篇 |
矿业工程 | 9篇 |
能源动力 | 97篇 |
轻工业 | 1122篇 |
水利工程 | 123篇 |
石油天然气 | 19篇 |
无线电 | 255篇 |
一般工业技术 | 870篇 |
冶金工业 | 1447篇 |
原子能技术 | 24篇 |
自动化技术 | 789篇 |
出版年
2024年 | 9篇 |
2023年 | 47篇 |
2022年 | 86篇 |
2021年 | 150篇 |
2020年 | 121篇 |
2019年 | 134篇 |
2018年 | 213篇 |
2017年 | 218篇 |
2016年 | 239篇 |
2015年 | 202篇 |
2014年 | 249篇 |
2013年 | 493篇 |
2012年 | 369篇 |
2011年 | 367篇 |
2010年 | 262篇 |
2009年 | 269篇 |
2008年 | 257篇 |
2007年 | 260篇 |
2006年 | 146篇 |
2005年 | 130篇 |
2004年 | 134篇 |
2003年 | 108篇 |
2002年 | 119篇 |
2001年 | 87篇 |
2000年 | 69篇 |
1999年 | 80篇 |
1998年 | 539篇 |
1997年 | 295篇 |
1996年 | 196篇 |
1995年 | 97篇 |
1994年 | 81篇 |
1993年 | 74篇 |
1992年 | 20篇 |
1991年 | 12篇 |
1990年 | 14篇 |
1989年 | 11篇 |
1988年 | 22篇 |
1987年 | 15篇 |
1986年 | 17篇 |
1985年 | 21篇 |
1984年 | 10篇 |
1983年 | 3篇 |
1982年 | 8篇 |
1981年 | 6篇 |
1980年 | 7篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 21篇 |
1976年 | 28篇 |
1975年 | 2篇 |
排序方式: 共有6323条查询结果,搜索用时 15 毫秒
11.
Meza-Espinoza Libier de los Ángeles Vivar-Vera María de Lourdes García-Magaña María Sáyago-Ayerdi Sonia G. Chacón-López Alejandra Becerrea-Verdín Eduardo M. Montalvo-González Efigenia 《Food science and biotechnology》2018,27(2):509-517
Food Science and Biotechnology - The enzymatic activity and partial characterization of proteases from Bromelia karatas fruits were evaluated and compared with Bromelia pinguin proteases. The... 相似文献
12.
The paper is a comprehensive review of the Spanish National Hydrological Plan, which proposes to transfer water from the lower part of the Ebro River up to the Levante basins, around 912 km away. The National Hydrological Plan is a conventional, static plan, which focuses primarily on supply management. The plan is based on the explicit assumption that the world will change only incrementally during its entire economic life of 100-200 years. The analysis indicates that much of the increased water demands forecasted are unlikely to materialize due to increasing emphasis on demand management practices, major structural changes in the agricultural sector that will occur by 2020 and the requirements of the Water Directive of the European Union, which must be fulfilled by 2010. Even now, the cost per cubic metre of water delivered at the end of the transfer is nearly twice the cost of desalinated water. The National Hydrological Plan in its present form cannot be justified for economic, environmental and social reasons. In addition, the plan will not be necessary if demand management practices are implemented. 相似文献
13.
14.
G García-Bermúdez H Somacal MA Cardona A Filevich E Achterberg L Szybisz 《Canadian Metallurgical Quarterly》1995,51(3):1181-1191
15.
JM Rodríguez J Arias Díaz C García Carreras J Torres Melero JL Balibrea 《Canadian Metallurgical Quarterly》1994,9(5):304-310
Reaction of bacterial adhesins with complementary receptors on the surfaces of mucosal respiratory, gastrointestinal and genitourinary cells leads to bacterial adhesion to the human body. This is the first step in the sequence of events leading to infection. It has been observed that subinhibitory concentrations (sub-MICs) of some antibiotics are able to reduce bacterial adhesion. The pharmacokinetic curves of antibiotics show that these sub-MICs are present in tissues during a typical course of therapy. This study investigated the ability of sub-MICs of seven macrolides and four fluoroquinolones to reduce adhesiveness of Staphylococcus aureus to human buccal cells. The literature generally reports data for only one antibiotic at a time. To obtain an overall view of the findings of eleven antibiotics together, the data have been normalized according to the molecular weight of each antibiotic and the dose-effect curves determined. 相似文献
16.
17.
Summary In this study, new hydrogels in rod shape were prepared from N-acryloyl-TRIS(hydroxymethyl)aminomethane (NAT) using ethylene glycol dimethacrylate (EGDMA) or N,N’methylenebisacrylamide (BIS) as crosslinking agent, dimethylformamide (DMF) as solvent and benzoyl peroxide (BPO) as initiator. In most cases, 2-hydroxyethyl methacrylate (HEMA), acrylamide (Aam) or acrylic acid (Aac) were used as co-monomers. The polymeric matrices obtained by free radical polymerization exhibited different properties by changing crosslinker, crosslinker concentration, co-monomer and initial NAT/co-monomer mole ratio. Besides, hydrogels from HEMA, Aam and Aac with BIS in absence of NAT were prepared under the same experimental reaction conditions in order to compare the properties of these products with those synthesized from NAT and the respective co-monomers. Some of the final products were selected to perform urea release assays, conducted through swelling-controlled release. Urea was chosen as “model” plant fertilizer agent. 相似文献
18.
19.
J García-Martínez JA Castro M Ramón A Latorre A Moya 《Canadian Metallurgical Quarterly》1998,149(3):1377-1382
The evolution of Drosophila subobscura mitochondrial DNA has been studied in experimental populations, founded with flies from a natural population from Esporles (Majorca, Balearic Islands, Spain). This population, like other European ones, is characterized by the presence of two very common (>96%) mitochondrial haplotypes (called I and II) and rare and endemic haplotypes that appear at very low frequencies. There is no statistical evidence of positive Darwinian selection acting on the mitochondrial DNA variants according to Tajima's neutrality test. Two experimental populations, with one replicate each, were established with flies having a heterogeneous nuclear genetic background, which was representative of the composition of the natural population. Both populations were started with the two most frequent mitochondrial haplotypes, but at different initial frequencies. After 13 to 16 generations, haplotype II reached fixation in three cages and its frequency was 0.89 by generation 25 in the fourth cage. Random drift can be rejected as the force responsible for the observed changes in haplotype frequencies. There is not only statistical evidence of a linear trend favoring a mtDNA (haploid) fitness effect, but also of a significant nonlinear deviation that could be due to a nuclear component. 相似文献
20.