全文获取类型
收费全文 | 10081篇 |
免费 | 612篇 |
国内免费 | 159篇 |
专业分类
电工技术 | 293篇 |
综合类 | 186篇 |
化学工业 | 1890篇 |
金属工艺 | 276篇 |
机械仪表 | 361篇 |
建筑科学 | 424篇 |
矿业工程 | 31篇 |
能源动力 | 299篇 |
轻工业 | 593篇 |
水利工程 | 80篇 |
石油天然气 | 124篇 |
武器工业 | 16篇 |
无线电 | 1886篇 |
一般工业技术 | 1728篇 |
冶金工业 | 1260篇 |
原子能技术 | 123篇 |
自动化技术 | 1282篇 |
出版年
2024年 | 18篇 |
2023年 | 128篇 |
2022年 | 209篇 |
2021年 | 268篇 |
2020年 | 204篇 |
2019年 | 179篇 |
2018年 | 247篇 |
2017年 | 243篇 |
2016年 | 232篇 |
2015年 | 246篇 |
2014年 | 353篇 |
2013年 | 617篇 |
2012年 | 520篇 |
2011年 | 564篇 |
2010年 | 474篇 |
2009年 | 515篇 |
2008年 | 523篇 |
2007年 | 469篇 |
2006年 | 449篇 |
2005年 | 373篇 |
2004年 | 335篇 |
2003年 | 340篇 |
2002年 | 272篇 |
2001年 | 259篇 |
2000年 | 250篇 |
1999年 | 216篇 |
1998年 | 499篇 |
1997年 | 331篇 |
1996年 | 235篇 |
1995年 | 161篇 |
1994年 | 137篇 |
1993年 | 154篇 |
1992年 | 87篇 |
1991年 | 82篇 |
1990年 | 77篇 |
1989年 | 55篇 |
1988年 | 55篇 |
1987年 | 54篇 |
1986年 | 60篇 |
1985年 | 32篇 |
1984年 | 32篇 |
1983年 | 20篇 |
1981年 | 40篇 |
1980年 | 25篇 |
1979年 | 21篇 |
1978年 | 26篇 |
1977年 | 40篇 |
1976年 | 43篇 |
1974年 | 12篇 |
1971年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
H Nakamine AS Masih WC Chan WG Sanger JO Armitage DD Weisenburger 《Canadian Metallurgical Quarterly》1993,10(1-2):79-88
Southern blot analysis was performed with a panel of DNA probes to detect rearrangements of c-myc, bcl-1, bcl-2 and bcl-3 in 14 cases of B-cell non-Hodgkin's lymphoma (NHL) with a clonal cytogenetic rearrangement involving the chromosome 14q32 locus and no known donor chromosome [t(14;?)(q32;?)]. In our experience, 21% of all chromosomal abnormalities involving the 14q32 locus in B-cell NHL are of this type. We found oncogene rearrangements in five of the 14 cases: bcl-1 rearrangement on one mantle zone lymphoma, bcl-2 rearrangements in two follicular lymphomas, and c-myc rearrangements in two small noncleaved cell lymphomas. We conclude that a 14q32+ abnormality of unknown origin is a relatively frequent karyotypic finding in B-cell NHL. In one third of the cases, known oncogenes that have been previously described in reciprocal translocations involving the immunoglobulin heavy chain locus were shown to be involved in the 14q32+ abnormality. The translocations in the other cases are likely to have involved one of the above oncogenes with breakpoints not revealed by the probes employed, other known oncogenes, or oncogenes that have not yet been identified. 相似文献
52.
We studied the efficacy of sequential intravenous-oral pefloxacin therapy in community-acquired lower respiratory tract infection in 24 patients with one or more underlying conditions. Twenty-eight patients were enrolled into the study but only 24 patients were evaluated. There were 16 males and 8 females with a mean age of 66.9 +/- 11.2 years (mean +/- SD, range 46 to 87 years). The underlying conditions present were bronchiectasis, chronic obstructive lung disease and diabetes mellitus. Patients who were older than 70 years but without any underlying condition were also enrolled. All received 4 days of intravenous pefloxacin 400 mg twice a day followed by oral pefloxacin 400 mg twice a day for another 10 days. Assessment of success was based on clinical, microbiological and radiological improvement. Pefloxacin produced 79.2% clinical cure rate. Another 8.3% showed improvement. Pefloxacin was well tolerated. There were few adverse effects and none of the patients required a change of antibiotic. Pefloxacin was an effective and well tolerated treatment for respiratory tract infection and had the advantage of broad in-vitro antibacterial activity, twice daily dosing and sequential availability in an intravenous and oral formulation. 相似文献
53.
54.
L Chan 《Canadian Metallurgical Quarterly》1995,6(5):335-340
Genetic manipulations of experimental animals have provided valuable information on lipoprotein metabolism in vivo. Somatic gene transfer is a novel method for introducing foreign genes into animals in vivo. Adenovirus-mediated transfer of genes for the LDL receptor, the receptor-associated protein, apolipoprotein A-I, apolipoprotein E, cholesterol 7 alpha-hydroxylase, and apolipoprotein B messenger RNA editing protein has resulted in high-level expression of these transgenes in mice and hamsters, and the production of interesting animal models of lipoprotein metabolism. Somatic gene transfer is a valuable tool for analyzing the role of transgenes in lipoprotein metabolism in vivo and for exploring the potential use of specific transgenes for human gene therapy. 相似文献
55.
We have examined the applicability of this simple and effective test to polymer systems widely used in the medical industry. First, it was found that not every polymer examined exhibited a distinct onset of autocatalytic oxidation detectable by DSC. However, for cases where distinct onsets are found, powerful insights can be obtained. These included activation energy of the degradation, thermal oxidative shelf life prediction, and correlation, with product performances. Actual examples are presented to illustrate the utility of the test. 相似文献
56.
A quartz microbalance technique has been used to study the growth of4He and H2 adsorbed on sodium. In contrast to cesium, adsorption of4He and H2 do occur on a sodium surface. 相似文献
57.
Charles A. Bateman Lijie Zhang Helen M. Chan Martin P. Harmer 《Journal of the American Ceramic Society》1992,75(5):1281-1283
It is experimentally observed that the peritectic reaction, 211 + liquid → 123, can be driven essentially to completion in 1 h at an undercooling of only ∽30°C. The kinetic data, together with the observed microstructures, are inconsistent with the normal mechanism of the peritectic reaction. It is proposed that the mechanism of the reaction involves dissolution of 211 particles into the liquid and precipitation of solid 123. The aligned grain structure is explained through sympathetic nucleation of new 123 grains on existing grains. 相似文献
58.
R Poon P Lecavalier P Chan C Viau H H?kansson I Chu VE Valli 《Canadian Metallurgical Quarterly》1995,15(6):455-463
Groups of ten male and female weanling Sprague-Dawley rats were fed diet containing 0, 5, 50, 500 or 5000 ppm of a medium-chain chlorinated paraffin (C14-17, 52% chlorination) for a period of 13 weeks. Increased relative liver weight was observed at 500 and 5000 ppm in females and at 5000 ppm in males. Relative kidney weight was increased at 5000 ppm in both sexes. Serum cholesterol was increased in the females in a dose-related manner starting at 50 ppm. At 5000 ppm, animals of both sexes had elevated hepatic UDP-glucuronosyltransferase activity while only females showed increased aminopyrine N-demethylase activity. Increased urinary N-acetylglucosaminidase activity occurred at 5000 ppm in females. Increased urinary ascorbic acid excretion monitored at week 12 and a decreased hepatic vitamin A level were detected in females receiving the 500 ppm diet and male and female rats at 5000 ppm. Mild, adaptive histopathological changes were detected in the liver of rats of both sexes at 500 and 5000 ppm, and in the thyroid of males and females starting at 500 and 50 ppm respectively. Minimal changes were observed in the kidney proximal tubules of male rats fed the 5000 ppm diet and in the inner medulla tubules of female rats fed the 500 and 5000 ppm diets. These data indicate that the medium-chain chlorinated paraffin produces biochemical and histological changes at dietary levels of greater than or = 50 ppm in females and greater than or = 500 ppm in males. 相似文献
59.
钢结构稳定设计——理论与实践 总被引:2,自引:0,他引:2
本文提出了实际工程结构的非线性理论设计和分析方法(NIDA),并以澳门回归纪念馆的设计为例,展示了本方法的优越性.在设计过程中,设计者无需假设K系数和有效长度,在结构分析完成后便可迅速完成设计,因此本文提出的方法既经济又便利.尽管对于钢框架在往复荷载及动力荷载作用下的弹塑性大位移分析已经非常成熟,但本文的方法开创了结构的非线性分析及设计的新纪元,能够对现行的设计方法理论起到巨大的推动作用. 相似文献
60.
Chan T.H. Yeung R.W. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2002,48(7):1992-1995
We establish a one-to-one correspondence between information inequalities and group inequalities. The major implication of our result is that we can prove information inequalities by proving the corresponding group inequalities, and vice versa. By giving a group-theoretic proof for all Shannon-type inequalities, we suggest that new inequalities could be discovered by making use of the rich set of tools in group theory. On the other hand, via a non-Shannon-type information inequality discovered by Zhang and Yeung (1997), we obtain a new inequality in group theory whose meaning is yet to be understood 相似文献