全文获取类型
收费全文 | 4634篇 |
免费 | 91篇 |
国内免费 | 17篇 |
专业分类
电工技术 | 53篇 |
综合类 | 13篇 |
化学工业 | 318篇 |
金属工艺 | 60篇 |
机械仪表 | 54篇 |
建筑科学 | 40篇 |
矿业工程 | 1篇 |
能源动力 | 57篇 |
轻工业 | 205篇 |
水利工程 | 16篇 |
石油天然气 | 8篇 |
无线电 | 199篇 |
一般工业技术 | 302篇 |
冶金工业 | 3207篇 |
原子能技术 | 19篇 |
自动化技术 | 190篇 |
出版年
2023年 | 13篇 |
2022年 | 23篇 |
2021年 | 46篇 |
2020年 | 35篇 |
2019年 | 27篇 |
2018年 | 42篇 |
2017年 | 51篇 |
2016年 | 39篇 |
2015年 | 47篇 |
2014年 | 67篇 |
2013年 | 125篇 |
2012年 | 67篇 |
2011年 | 84篇 |
2010年 | 73篇 |
2009年 | 77篇 |
2008年 | 61篇 |
2007年 | 67篇 |
2006年 | 65篇 |
2005年 | 54篇 |
2004年 | 47篇 |
2003年 | 47篇 |
2002年 | 32篇 |
2001年 | 32篇 |
2000年 | 31篇 |
1999年 | 134篇 |
1998年 | 1012篇 |
1997年 | 631篇 |
1996年 | 394篇 |
1995年 | 200篇 |
1994年 | 171篇 |
1993年 | 232篇 |
1992年 | 44篇 |
1991年 | 24篇 |
1990年 | 39篇 |
1989年 | 30篇 |
1988年 | 32篇 |
1987年 | 24篇 |
1986年 | 27篇 |
1985年 | 24篇 |
1984年 | 6篇 |
1983年 | 15篇 |
1982年 | 18篇 |
1981年 | 26篇 |
1980年 | 30篇 |
1979年 | 10篇 |
1978年 | 17篇 |
1977年 | 98篇 |
1976年 | 219篇 |
1975年 | 8篇 |
1973年 | 5篇 |
排序方式: 共有4742条查询结果,搜索用时 21 毫秒
61.
AI Shul'mina VIa Cherniak NN Magretova EL Malova LA Dronova 《Canadian Metallurgical Quarterly》1976,41(7):1229-1234
Serine proteases inhibitor with pl-7.3, isolated from potatoe tubers by isoelectric focusing procedure as described previously (V.V. Mosolov et al., Bioorganic Chem., 1, 1449, 1975), was homogeneous under ultracentrifugation, having sedimentation coefficient S20,w 2.8S. Its molecular weight, investigated by sedimentation equilibrium and gel filtration through Sephadex G-100, was found to be 32500 and 31500 respectively. The Stokes radius R and frictional ratio f/fo were found to be 24 A and 1.14. The molecular weight of the inhibitor as determined by sodium dodecylsulfate polyacrylamide electrophoresis was twice as low as determined in ultracentrifuge and by gel filtration procedure. It is suggested that the inhibitor is dimer and consists of two protomers of equal molecular weight. 相似文献
62.
63.
64.
LA Gould LA Perez DB Hayt CV Reddy C Blatt RF Gomprecht 《Canadian Metallurgical Quarterly》1976,38(7):744-751
Myocardial imaging with technetium-99m stannous polyphosphate was performed on 46 patients. Eleven patients had no cardiac disease, 22 had acute myocardial infarction, and 13 had stable arteriosclerotic heart disease. Distinct patterns of myocardial activity were noted: (1) the patients with no obvious cardiac disease showed no cardiac activity; (2) stable arteriosclerotic heart disease showed faint, ill-defined cardiac activity, primarily in the anterior or inferior aspect of the left ventricle; (3) acute myocardial infarction showed intense, focal, well-defined activity, with a shape that characterized the location of the infarct. 相似文献
65.
In the light and electron microscopes, long tubular bones of Wistar rats that were flown for 22 d onboard the Cosmos-605 biosatellite and were exposed to a ground-based simulation experiment were examined. About half of the flight rats showed osteoporosis of metaphyses which was usually combined with a decrease of the mass of the primary spongiosa in the vicinity of the epiphyseal cartilaginous plate. This gives evidence that the growth of the bones could have been inhibited in flight. The light and electron microscopy of bones of flight rats revealed wide osteocyte lacunae which could have been produced by perilacunar osteolysis. In the simulation experiment, reduction in the metaphyseal spongiosa occurred only in one-third of the rats and was less pronounced than in flight rats; no decrease of the mass of the primary spongiosa near the cartilaginous plate was noted. Histological investigation of bones 27 d postflight demonstrated that that time period was not enough to eliminate all the changes in the bones tested. 相似文献
66.
The smoking habits of 56 families who lost babies to the sudden infant death syndrome (SIDS) were compared to those of 86 control families. A higher proportion of SIDS mothers smoked both during pregnancy (61% vs. 42%) and after their babies were born (59% vs. 37%). SIDS mother also smoked a significantly greater number of cigarettes than controls. Exposure to cigarette smoke ("passive smoking") appears to enhance the risk of SIDS for reasons not known. 相似文献
67.
Rabbit yolk sac splanchnopleur exposed in utero to IgG-HRP and IgG-ferritin conjugates, rabbit and bovine anti-HRP antibodies, free HRP, ferritin and human IgG, was examined ultrastructurally in an attempt to determine whether or not coated micropinocytotic vesicles are involved in selectively transporting immunoglobulins across yolk sac endodermal cells. Human, rabbit and bovine IgG-HRP conjugates, rabbit anti-HRP antibodies, free HRP and human IgG, all become localised in coated micropinocytotic vesicles. Differences were observed in that only human IgG and rabbit anti-HRP antibodies could be located in the intercellular space and bovine IgG-HRP conjugate could not be detected in coated micropinocytotic vesicles in confluence with the lateral and basal plasmalemma. Bovine anti-HRP anti-bodies, IgG-ferritin conjugates, and free ferritin, could not be observed in coated micropinocytotic vesicles. All proteins were detected in macropinocytotic vesicles, and dense bodies resembling phagolysosomes. Results are discussed in the light of a proposal that selection occurs at the cell surface during formation of coated micropinocytotic vesicles and is not linked to intracellular proteolysis. 相似文献
68.
69.
M. G. Enig LA. Pallansch J. Sampugna M. Keeney 《Journal of the American Oil Chemists' Society》1983,60(10):1788-1795
The fat in 220 samples from 35 food types has been analyzed for component fatty acids by gas liquid chromatography on a 15-m capillary column coated with SP-2340. The methodology permitted the determination of trans-octadecenoic fatty acids in the food samples. For food types in which the majority of samples containedtrans fatty acids, the range (weight percent of methyl esters) of this class of acids arranged by fat content of the food types was: high fat levels (>70% fat) — animal and dairy fats, 0.3–6.6%, stick margarines, 15.9–31.0%, tub margarines, 6.8–17.6%, and vegetable shortenings, 8.7–35.4%; moderately high fat levels (40–70% fat) —diet margarines, 11.3–13.3%; moderate fat levels (10–40% fat) — breading mixes and fried crusts, 8.1–32.7%, cakes, candies and frostings, 3.2–33.2%, cream substitutes, 0.4–11.5%, cookies, 2.5–34.2%, crackers, 1.9–29.0%, pastries and pastry crusts, 0.6–31.2%, corn and mixed grain snack chips, 0.4–30.4%; low fat levels (<10% fat) - breads and rolls, 0.2–23.6%, pretzels, 10.8–29.2%, and puddings, 28.4-35.1%. The majority of samples in the following food types did not containtrans fatty acids, except in cases where the label indicated partial hydrogenation of the oil: mayonnaises and salad dressings, salad and cooking oils and potato chips. For samples in these three food types which containedtrans fatty acids, the range was 0.2-23.2%. None of the peanut butters or pizza crusts analyzed containedtrans fatty acids. 相似文献
70.
目的:初步阐明谷糠多酚对酒精性胃黏膜损伤的保护作用以及具体分子机制,为谷糠多酚在饮酒人群胃黏膜损伤营养干预方面的应用提供科学依据。方法:雄性Wistar大鼠连续3 周每天灌胃50 mg/kg mb谷糠多酚,干预结束后通过灌胃体积分数75%乙醇溶液建立急性酒精性胃黏膜损伤模型;利用不同剂量(1~15 μg/mL)谷糠多酚对人胃黏膜上皮细胞(GES-1)处理24 h,继而通过1 000 mmol/L酒精继续作用12 h建立酒精性GES-1细胞损伤及干预模型;通过解剖观察大鼠胃组织形态学及病理结构,评价谷糠多酚对大鼠胃黏膜组织的保护作用;结合细胞形态变化及存活情况评价谷糠多酚对GES-1细胞的保护作用;通过测定氧化应激和细胞凋亡相关指标,评价谷糠多酚对急性酒精性胃黏膜损伤大鼠及GES-1细胞的抗氧化和抑制凋亡能力的影响。结果:谷糠多酚可以有效预防酒精引起的大鼠胃黏膜及GES-1细胞损伤,极显著缓解酒精引起的GES-1细胞活性氧(reactive oxygen species,ROS)水平升高(P<0.01);同时极显著缓解大鼠胃黏膜组织和GES-1细胞中丙二醛(methane dicarboxylic aldehyde,MDA)水平升高(P<0.01),提高超氧化物歧化酶(superoxide dismutase,SOD)活力,明显抑制酒精引起的细胞凋亡。结论:谷糠多酚能够通过缓解酒精引起的胃黏膜上皮细胞氧化损伤从而保护胃黏膜。 相似文献