全文获取类型
收费全文 | 22134篇 |
免费 | 1674篇 |
国内免费 | 956篇 |
专业分类
电工技术 | 1049篇 |
技术理论 | 4篇 |
综合类 | 1386篇 |
化学工业 | 3966篇 |
金属工艺 | 1261篇 |
机械仪表 | 1186篇 |
建筑科学 | 1542篇 |
矿业工程 | 557篇 |
能源动力 | 524篇 |
轻工业 | 1292篇 |
水利工程 | 338篇 |
石油天然气 | 1316篇 |
武器工业 | 120篇 |
无线电 | 2377篇 |
一般工业技术 | 2684篇 |
冶金工业 | 2191篇 |
原子能技术 | 216篇 |
自动化技术 | 2755篇 |
出版年
2024年 | 90篇 |
2023年 | 386篇 |
2022年 | 553篇 |
2021年 | 791篇 |
2020年 | 631篇 |
2019年 | 553篇 |
2018年 | 583篇 |
2017年 | 676篇 |
2016年 | 549篇 |
2015年 | 762篇 |
2014年 | 930篇 |
2013年 | 1177篇 |
2012年 | 1252篇 |
2011年 | 1329篇 |
2010年 | 1234篇 |
2009年 | 1247篇 |
2008年 | 1139篇 |
2007年 | 1118篇 |
2006年 | 1093篇 |
2005年 | 995篇 |
2004年 | 676篇 |
2003年 | 659篇 |
2002年 | 688篇 |
2001年 | 557篇 |
2000年 | 526篇 |
1999年 | 663篇 |
1998年 | 876篇 |
1997年 | 633篇 |
1996年 | 488篇 |
1995年 | 418篇 |
1994年 | 346篇 |
1993年 | 270篇 |
1992年 | 168篇 |
1991年 | 134篇 |
1990年 | 94篇 |
1989年 | 113篇 |
1988年 | 60篇 |
1987年 | 36篇 |
1986年 | 34篇 |
1985年 | 21篇 |
1984年 | 13篇 |
1983年 | 9篇 |
1982年 | 12篇 |
1981年 | 14篇 |
1980年 | 19篇 |
1978年 | 1篇 |
1977年 | 31篇 |
1976年 | 113篇 |
1975年 | 1篇 |
1955年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
HH Henneicke-von Zepelin U Mrowietz L F?rber K Bruck-Borchers C Schober J Huber G Lutz R Kohnen E Christophers D Welzel 《Canadian Metallurgical Quarterly》1993,129(6):713-717
We report the results of a multicentre, double-blind, placebo-controlled study of topical therapy with omega-3-polyunsaturated fatty acids (omega-3-PUFA) in 52 patients suffering from moderate plaque-type psoriasis. In each patient, two similar stable psoriatic plaques served as indicator lesions for the study. One indicator lesion was randomly assigned to treatment with topical preparations of highly purified omega-3-PUFA in one of two concentrations (1 or 10%), and the other was treated with placebo. Efficacy assessment was based on changes in local psoriasis severity index, area involved, erythema, desquamation, induration and pruritus. After 8 weeks of treatment, all indicator lesions had improved significantly, compared with baseline. However, no statistically or clinically relevant differences between the omega-3-PUFA-treated and the placebo-treated lesions were found. Therapy was well tolerated and, apart from one patient who developed perilesional eczema, no clinically relevant adverse events occurred. In conclusion, topical omega-3-PUFA were not effective in a randomized, placebo-controlled, double-blind setting. Results of non-blind trials should be (re-)considered with caution. 相似文献
72.
We have used the fluorescence in situ hybridization (FISH) technique to refine the localization of the cystic fibrosis transmembrane conductance regulator (CFTR) gene on human chromosome 7. The result shows that the gene is most likely located within band q31.3. 相似文献
73.
Zeng Yanwei Xue Wanrong A. Benedetti G. Fagherazzi 《Journal of Materials Science》1994,29(4):1045-1050
By using the X-ray diffraction profile-fitting technique, the microstructures of Sm, Mn-modified PbTiO3 piezoelectric ceramic discs, including ferroelectric domain sizes, microstrains, and their variations with the poling strength have been quantitatively investigated. The results manifest that the modified PbTiO3 ceramics contain a high density of domain walls due to the presence of finely-divided coherent domain structures (tens of nanometres in dimension). The poling treament can evidently influence the domain-size distribution, with a more homogeneous microstructure being developed; however, it simultaneously causes high anisotropic microstrains within the structure which, together with the high density of domain walls, is expected to be responsible for the unusual high electromechanical coupling properties possessed by this material. 相似文献
74.
曾荣昌 《石油化工腐蚀与防护》1998,15(1):48-49
介绍了氯磺化聚乙烯涂料、改性聚苯乙烯涂料、环氧树脂类涂料、水冷器涂料、抗静电涂料等涂料的性能、用途和在洞庭氮肥厂的使用情况.同时对几种涂料施工方案进行了比较. 相似文献
75.
Analysis of simian hemorrhagic fever virus (SHFV) subgenomic RNAs, junction sequences, and 5' leader
Full-length simian hemorrhagic fever virus (SHFV) genome RNA (about 15 kb in length) and six subgenomic RNAs, ranging in size from 0.65 to 4.7 kb, were detected by Northern blot hybridization in MA104 cytoplasmic extracts with a 3' genomic antisense probe. The 5' regions of the two smallest subgenomic RNAs (RNAs 6 and 7) were cloned and sequenced. Sequence analysis indicated that these two RNAs contained a common 5' leader sequence joined to the subgenomic RNA bodies via a highly conserved junction sequence; the junction sequence of RNA 7 was 5'-TTAACC-3', while that of RNA 6 was 5'-TCAACC-3'. The complete 5' leader sequence (208 nt) was obtained from genomic RNA. The genomic 5' junction sequence is identical to that of RNA 7. Northern blot hybridization with an antisense 5' leader probe confirmed the presence of the complete leader sequence in all six species of subgenomic RNA. In its virion morphology, genome size, gene order, and replication strategy, SHFV is most similar to viruses such as equine arteritis virus, lactate dehydrogenase-elevating virus, and Lelystad virus/porcine respiratory and reproductive syndrome virus. 相似文献
76.
77.
HH Thole 《Canadian Metallurgical Quarterly》1994,48(5-6):463-466
Fragments of 32, 26 and 17 kDa of the porcine estradiol receptor were prepared, all of which contain the ligand-binding site. While dimers of the 32 and 26 kDa fragments like those of intact receptor can be dissociated by protonation, the dimer of the 17 kDa fragment obtained by trypsination of the 26 kDa fragment is resistant to lowering the pH from 7.0 to 6.5 and below. Its dissociation can be achieved by 0.5 M MgCl2 at pH 7.0. All fragments are recognized by the MAB 13H2 in Western blots. The antibody also reacts with native receptor and the three fragments, both in their monomer and dimer states. The combining ratios of antibody with receptor, or its fragments, in the monomer and dimer states and the weakening of the estradiol-receptor bond by antibody attachment support the back to back and head to toe model of receptor dimers. 相似文献
78.
本文介绍了系统信息提示的一种方法,井重点讨论了用8088汇编语言实现的方法。它采用基本信息串表和索引表,对于使用频度较高的系统,可以大大节约系统内存,具存较好的实性用。 相似文献
79.
80.
在对石油化工改扩建工程施工现场火灾危险因素识别评估的基础上,判定现场火灾危险等级、火灾类别,对灭火级别和保护距离进行验算,提出施工现场灭火器选型和配置方案。 相似文献