全文获取类型
收费全文 | 252881篇 |
免费 | 2790篇 |
国内免费 | 870篇 |
专业分类
电工技术 | 4811篇 |
综合类 | 194篇 |
化学工业 | 36129篇 |
金属工艺 | 9508篇 |
机械仪表 | 7545篇 |
建筑科学 | 6076篇 |
矿业工程 | 880篇 |
能源动力 | 7228篇 |
轻工业 | 21090篇 |
水利工程 | 2202篇 |
石油天然气 | 3230篇 |
武器工业 | 15篇 |
无线电 | 34281篇 |
一般工业技术 | 49977篇 |
冶金工业 | 48546篇 |
原子能技术 | 5075篇 |
自动化技术 | 19754篇 |
出版年
2021年 | 2172篇 |
2020年 | 1560篇 |
2019年 | 1916篇 |
2018年 | 3272篇 |
2017年 | 3309篇 |
2016年 | 3399篇 |
2015年 | 2219篇 |
2014年 | 3957篇 |
2013年 | 11474篇 |
2012年 | 6234篇 |
2011年 | 8572篇 |
2010年 | 6908篇 |
2009年 | 7890篇 |
2008年 | 8405篇 |
2007年 | 8296篇 |
2006年 | 7365篇 |
2005年 | 6501篇 |
2004年 | 6282篇 |
2003年 | 6555篇 |
2002年 | 6035篇 |
2001年 | 6513篇 |
2000年 | 5974篇 |
1999年 | 6389篇 |
1998年 | 16483篇 |
1997年 | 11410篇 |
1996年 | 8795篇 |
1995年 | 6607篇 |
1994年 | 5901篇 |
1993年 | 5844篇 |
1992年 | 4132篇 |
1991年 | 4020篇 |
1990年 | 3857篇 |
1989年 | 3649篇 |
1988年 | 3559篇 |
1987年 | 3017篇 |
1986年 | 2941篇 |
1985年 | 3206篇 |
1984年 | 2926篇 |
1983年 | 2828篇 |
1982年 | 2636篇 |
1981年 | 2542篇 |
1980年 | 2463篇 |
1979年 | 2306篇 |
1978年 | 2107篇 |
1977年 | 2604篇 |
1976年 | 3562篇 |
1975年 | 1764篇 |
1974年 | 1729篇 |
1973年 | 1666篇 |
1972年 | 1465篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
921.
1. In the present study we have investigated the ontogeny of FMRFamide expression in the snail, Lymnaea stagnalis, from its first appearance to its distribution in young adults. 2. The first FMRFamide-like immunoreactive (FaLI) cells within CNS appear by E45 embryonic stage (premetamorphic veliger). The number of FaLI neurons increases throughout both pre- and post-hatching development. 3. Both transient and sustained expression of FMRFamide-like immunoreactivity by specific sets of neurons occurs. Two cells which transiently express immunoreactivity appear outside the future CNS by the stage E45. Other population of transient FaLI neurons includes bilaterally symmetric groups of cells in the cerebral and pedal ganglia during posthatching stages P1 (hatchlings) to P5 (juveniles). All other immunostained cells which appear during development maintain their transmitter phenotype into adulthood. 4. The possible role of FMRFamide-related peptides in the processes of morpho- and neurogenesis is discussed. 相似文献
922.
923.
I Miura A Ohshima N Takahashi K Hashimoto T Nimura S Utsumi M Saito T Miki S Hirosawa AB Miura 《Canadian Metallurgical Quarterly》1996,64(3-4):249-256
We describe two cases of non-Hodgkin's lymphoma associated with t(3;6)(q27;p21.3) and BCL6 rearrangement. The first case was in a 78-year old woman, whose performance status (PS) was 1, the serum lactate dehydrogenase (LDH) level was elevated, and the Ann Arbor stage was IIIA with no extra nodal lymphomatous site. The pathological diagnosis from a biopsy of the inguinal lymph node was 'malignant lymphoma (ML), follicular, small cleaved' according to the Working Formulation. Complete remission was achieved. Although she had relapse in 1992, remission was obtained again. The second case was in a 62-year old man, whose PS was 1, the serum LDH was normal, and Ann Arbor stage was IVA with the involvement of the small intestine. Histological diagnosis of the cervical lymph node was 'ML, diffuse, large cell'. Complete remission was obtained without relapse. The 3q27 translocations, found in 20-30% of non-Hodgkin's lymphoma, are unique in having multiple chromosomal translocation partners. Chromosome band 6p21.3 is one of these partner sites that may be the site of a novel gene. The two cases presented here show that this translocation is a non-random chromosomal change involving 3q27 and BCL6. Since t(3;6) was the sole karyotypic abnormality in one case, this translocation may play a role in lymphomagenesis. 相似文献
924.
M Steinhardt HH Thielscher T von Horn R von Horn K Ermgassen D Smidt 《Canadian Metallurgical Quarterly》1996,103(4):136-141
Dairy calves and their dams from the dairy herd of the institute were used for this investigation. Calvings were watch carefully and jugular venous blood samples taken immediately after delivery from the cow and the calf and in the calf at 24 hours and at 48 hours of postnatal age as well were analyzed for T4, FT4, T3 and FT3 by luminescence enzyme immunoassay (LEIA). Higher thyroid values in calves than in their dams could be found increasing short after birth and reaching their highest level within 24 hours of postnatal life. The individual thyroid hormone values at birth and at 24 hours and at 48 hours of age are well correlated meaning the changes during the first days are specific for each calf. Strong correlation between the thyroid hormone values of the cows and those of the calves could be found. Mean values of thyroid hormones were significantly higher in female than in male calves all time but not different in the dams of these calves. 相似文献
925.
A. K. Karklit 《Refractories and Industrial Ceramics》1996,37(12):422-426
Dielectrics produced from corundum with commercial alumina and from quartz ceramics by hot pressing and by the conventional method with the use of F-9 silicone resin are described. The effect of technological factors on the properties of the specimens is studied.Translated from Ogneupory i Tekhnicheskaya Keramika, No. 12, pp. 7–12, December, 1996. 相似文献
926.
J Knodel VP Ruffolo P Ratanalangkarn K Wongboonsin 《Canadian Metallurgical Quarterly》1996,27(6):307-318
Two large national surveys in 1988 and 1933 provide new evidence on trends in family-size preferences in Thailand at a time when the Thai fertility transition is reaching its conclusion. Although the average preferred number of children has continued to decline, a resistant lower bound of two children is found for the vast majority of respondents, stemming, apparently, from a pervasive, although not inflexible, desire to have one child of each sex. Moreover, new evidence from birth-registration data indicates that the decline in the total fertility rate appears to have leveled off at about replacement level. These findings challenge the view that fertility in Thailand will continue to fall well below replacement level, and contradict recently expressed alarmist predictions of population decline in the foreseeable future. 相似文献
927.
As a science and as a special activity concerned with measurements, the science of metrology pursues a classical, orthodox
purpose, mainly involving the measurement of physical quantities. The term “measurement” is now applied also to social, economic,
medical, and other disciplines, including cybernetics and problems of management and control.
Translated from Izmeritel'naya Tekhnika, No. 7, pp. 17–20, July, 1996. 相似文献
928.
Ohne Zusammenfassung 相似文献
929.
930.
The microsecond Nd glass pulsed laser interaction with polycrystalline nickel was studied with particular emphasis on melting and the nature of the microstructural development following irradiation. The change in the melt pool shape and the melting efficiency as a function of the total laser power has been determined. Evidence is presented to show that for low energy pulse, the microstructural development accompanies fresh nucleation of grains and leads to a finer grain size than that of the substrate. At a higher energy level, growth competition leads to a coarser grain size. We also report a banded feature roughly parallel to the melt substrate interface that develops in the resolidified region during high energy interaction. These results are discussed in the light of our present understanding of rapid solidification processes. 相似文献