全文获取类型
收费全文 | 9424篇 |
免费 | 110篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 139篇 |
综合类 | 4篇 |
化学工业 | 851篇 |
金属工艺 | 109篇 |
机械仪表 | 142篇 |
建筑科学 | 164篇 |
矿业工程 | 32篇 |
能源动力 | 108篇 |
轻工业 | 693篇 |
水利工程 | 42篇 |
石油天然气 | 22篇 |
无线电 | 793篇 |
一般工业技术 | 983篇 |
冶金工业 | 4624篇 |
原子能技术 | 110篇 |
自动化技术 | 719篇 |
出版年
2021年 | 47篇 |
2019年 | 46篇 |
2018年 | 53篇 |
2017年 | 57篇 |
2016年 | 73篇 |
2015年 | 51篇 |
2014年 | 82篇 |
2013年 | 183篇 |
2012年 | 164篇 |
2011年 | 227篇 |
2010年 | 194篇 |
2009年 | 207篇 |
2008年 | 228篇 |
2007年 | 232篇 |
2006年 | 200篇 |
2005年 | 204篇 |
2004年 | 185篇 |
2003年 | 165篇 |
2002年 | 142篇 |
2001年 | 148篇 |
2000年 | 163篇 |
1999年 | 255篇 |
1998年 | 1261篇 |
1997年 | 722篇 |
1996年 | 542篇 |
1995年 | 321篇 |
1994年 | 291篇 |
1993年 | 373篇 |
1992年 | 162篇 |
1991年 | 164篇 |
1990年 | 154篇 |
1989年 | 172篇 |
1988年 | 159篇 |
1987年 | 126篇 |
1986年 | 149篇 |
1985年 | 132篇 |
1984年 | 88篇 |
1983年 | 91篇 |
1982年 | 88篇 |
1981年 | 73篇 |
1980年 | 74篇 |
1979年 | 78篇 |
1978年 | 79篇 |
1977年 | 146篇 |
1976年 | 229篇 |
1975年 | 61篇 |
1974年 | 56篇 |
1973年 | 53篇 |
1972年 | 37篇 |
1971年 | 36篇 |
排序方式: 共有9535条查询结果,搜索用时 15 毫秒
1.
Margeaux A. Miller Prof. Dr. Ellen M. Sletten 《Chembiochem : a European journal of chemical biology》2020,21(24):3451-3462
Perfluorocarbons, saturated carbon chains in which all the hydrogen atoms are replaced with fluorine, form a separate phase from both organic and aqueous solutions. Though perfluorinated compounds are not found in living systems, they can be used to modify biomolecules to confer orthogonal behavior within natural systems, such as improved stability, engineered assembly, and cell-permeability. Perfluorinated groups also provide handles for purification, mass spectrometry, and 19F NMR studies in complex environments. Herein, we describe how the unique properties of perfluorocarbons have been employed to understand and manipulate biological systems. 相似文献
2.
摘 要:主要介绍Sasol Agri公司硫酸四系统的技术改造,分两步进行,第一步更换转化器、热换热器及主省煤器,生产能力由1600t/d提高到1750 t/d,且鼓风机出口压力很低。第二步更换干燥塔、二吸塔及冷换热器,连续生产能力在1950 t/d以上。使用不锈钢材质及克瓦纳·凯密迪公司专有的换热器,使装置的改造相当成功,维护及操作费用较低,并具有较大的灵活性和可操作性。 相似文献
3.
可重定位的基于事务的系统级验证 总被引:2,自引:0,他引:2
功能验证已经成为开发SoC的主要问题。随着一些复杂SoC的规模超过两千万门,以及对开发和集成嵌入式软件的需求持续增加,软件模拟器已经力所不及。在设计过程需要几百万个时钟周期来充分测试和验证软件功能的情况下,软件仿真器的性能下降到1-5Hz。按照这种速率,软件调试需要几年的时 相似文献
4.
5.
We report a 20 month old female patient with diploid-triploid mixoploidy (46,XX/69,XXX) syndrome with hypothyroidism and precocious puberty. The triploid cell line was only expressed in the fibroblast culture and comprised the majority (95%) of the cells. Chromosome analysis of the fetal blood sample and peripheral blood sample were normal. The patient shows typical features of full triploidy (growth and severe mental retardation, cranial and facial dysmorphism, complete syndactyly of fingers 3/4, partial syndactyly of toes 2/3) and facial but no body asymmetry. At the age of 5 months central hypothyroidism and precocious puberty were diagnosed. Thin pigmented streaks were visible on the wrists and legs of the patient at the age of 16 months. This is the first patient reported so far with 46,XX/69,XXX mixoploidy suffering from hypothyroidism and precocious puberty. 相似文献
6.
7.
GS Kelner JM Minnerath MK Jenkins R Jemmerson 《Canadian Metallurgical Quarterly》1993,23(8):1992-1998
Male and female A/J mice were examined for their ability to elicit T lymphocyte and antibody (Ab) responses to the male-specific Ag, mouse testicular cytochrome c (Mt cyt). T lymphocytes from both male and female mice primed in vivo responded to the Ag in in vitro proliferation assays, and the dose-response curves were statistically indistinguishable. In addition, similar levels of Ab to Mt cyt were observed in immunized male and female mice. The B cells producing the Ab had switched isotypes to IgG1 and IgG2a, indicating that the self-reactive T helper (Th) cells in male mice were functional. Thus, male mice do not appear to be immunologically tolerant to Mt cyt, at least at the Th and B lymphocyte levels. No evidence for disease was found in male mice primed with Mt cyt. Major histocompatibility complex (MHC) class II-positive antigen-presenting cells are present in the testes and these were shown in vitro to process and present Mt cyt to a T cell hybridoma specific for the synthetic peptide Mt cyt 93-104. However, the hybridoma was not activated in the absence of exogenous Mt cyt 93-104 or Mt cyt, indicating that endogenous Mt cyt is not normally processed in sufficient quantity to effectively load MHC class II molecules with this particular Mt cyt-derived peptide. Notwithstanding any immunologic privilege of the testes, the lack of tolerance to Mt cyt and its failure to elicit an autoimmune disease could extend from the low levels of processed Mt cyt Ag available for T cell recognition. The T cell response elicited by Mt cyt contrasts the lack of response to mouse somatic cytochrome c which differs from Mt cyt at 13 amino acid residues and is expressed in most tissues and at higher levels. 相似文献
8.
FJ Overdyk PM Gramling-Babb JR Handy NI Faller MJ Miller 《Canadian Metallurgical Quarterly》1997,84(1):213-215
Robertsonian translocations, although relatively common as a constitutional genetic aberration, are rarely encountered in leukaemia. We report a case of acute myeloid leukaemia which showed an acquired Robertsonian translocation in the form of der(14;21) by cytogenetic analysis of leukaemic cells. This was confirmed by the PHA-stimulated culture of peripheral blood lymphocytes. A review of the literature identifies only eight reported cases of acquired Robertsonian translocations in leukaemia. In the majority of cases the Robertsonian translocation occurs as a secondary change in a complex abnormal clone, whereas in two out of nine patients reported, including ours, it is found as a sole karyotypic abnormality. 相似文献
9.
10.
RM Campbell EP Heimer M Ahmad HG Eisenbeis TJ Lambros Y Lee RW Miller PR Stricker AM Felix 《Canadian Metallurgical Quarterly》1997,49(6):527-537
In the present study, human growth hormone-releasing factor (hGRF) and analogs were successfully pegylated at the carboxy-terminus using a novel solid- and solution-phase strategy. Following synthesis, these pegylated hGRF analogs were evaluated for in vitro and in vivo biological activity. Specifically, hGRF (1-29)-NH2, [Ala15]-hGRF (1-29)-NH2, [desNH2Tyr1, D-Ala2, Ala15]-hGRF(1-29)-NH2 and [His1, Val2, Gln8, Ala15, Leu27]-hGRF(1-32)-OH were each C-terminally extended using a Gly-Gly-Cys-NH2 spacer (previously demonstrated not to alter intrinsic biological activity), and then monopegylated via coupling to an activated dithiopyridyl-PEG reagent. PEG moieties of 750, 2000, 5000 or 10,000 molecular weight (MW) were examined to determine the effect of polymer weight on activity. Initial biological evaluations in vitro revealed that all C-terminally pegylated hGRF analogs retained high growth hormone (GH)-releasing potencies, regardless of the MW of PEG polymer employed. Two of these pegylated hGRF analogs, [desNH2Tyr1, D-Ala2, Ala15]-hGRF (1-29)-Gly-Gly-Cys(NH2)-S-Nle-PEG5000 and [His1, Val2, Gln8, Ala15, Leu27]-hGRF(1-32)-Gly-Cys(NH2)-S-Nle-PEG5000, were subsequently evaluated in both pig and mouse models and found to be highly potent (in vivo potency range = 12-55-fold that of native hGRF). Relative to their non-pegylated counterparts, these two pegylated hGRF analogs exhibited enhanced duration of activity. 相似文献