全文获取类型
收费全文 | 3593篇 |
免费 | 32篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 16篇 |
综合类 | 1篇 |
化学工业 | 130篇 |
金属工艺 | 28篇 |
机械仪表 | 41篇 |
建筑科学 | 38篇 |
矿业工程 | 1篇 |
能源动力 | 7篇 |
轻工业 | 103篇 |
水利工程 | 8篇 |
石油天然气 | 2篇 |
无线电 | 79篇 |
一般工业技术 | 160篇 |
冶金工业 | 2890篇 |
原子能技术 | 7篇 |
自动化技术 | 116篇 |
出版年
2021年 | 12篇 |
2020年 | 11篇 |
2019年 | 14篇 |
2018年 | 11篇 |
2017年 | 20篇 |
2016年 | 16篇 |
2015年 | 7篇 |
2014年 | 16篇 |
2013年 | 45篇 |
2012年 | 29篇 |
2011年 | 38篇 |
2010年 | 19篇 |
2009年 | 27篇 |
2008年 | 26篇 |
2007年 | 37篇 |
2006年 | 47篇 |
2005年 | 29篇 |
2004年 | 30篇 |
2003年 | 29篇 |
2002年 | 25篇 |
2001年 | 26篇 |
2000年 | 25篇 |
1999年 | 95篇 |
1998年 | 913篇 |
1997年 | 494篇 |
1996年 | 342篇 |
1995年 | 199篇 |
1994年 | 136篇 |
1993年 | 172篇 |
1992年 | 35篇 |
1991年 | 35篇 |
1990年 | 29篇 |
1989年 | 39篇 |
1988年 | 30篇 |
1987年 | 42篇 |
1986年 | 40篇 |
1985年 | 41篇 |
1984年 | 12篇 |
1983年 | 14篇 |
1982年 | 22篇 |
1981年 | 18篇 |
1980年 | 28篇 |
1979年 | 12篇 |
1978年 | 14篇 |
1977年 | 62篇 |
1976年 | 172篇 |
1975年 | 15篇 |
1972年 | 9篇 |
1971年 | 10篇 |
1967年 | 6篇 |
排序方式: 共有3627条查询结果,搜索用时 960 毫秒
21.
We describe in this report a sensitive and direct method for the analysis of tamoxifen (TAM) in microsamples of plasma. The drug and internal standard (quinine bisulfate, I.S.) were separated on a 10-microm particle, 10 cm X 8 mm CN cartridge in conjunction with a radial compression system. The mobile phase was a mixture of 0.1 M sodium acetate in 0.001 M tetrabutylammonium phosphate solution (pH 6) and methanol (30:70, v/v) at a flow-rate of 4 ml/min. After addition of I.S. and o-phosphoric acid in acetonitrile (0.6 M) to the plasma (30 microl), the mixture was placed in an ultraviolet shortwave transluminator for 2 min prior to injection into the chromatograph. The compounds were detected in the effluent fluorometrically at excitation and emission wavelengths of 258 and 378 nm, respectively. Under these conditions, no interference in the assay from any endogenous substance or other concurrently used drugs was observed and the retention times of I.S. and TAM were 4.4 and 10.15 min, respectively. The concentration of TAM in plasma was linearly (r>0.9983) related to the peak height ratio (TAM/I.S.) in the range 0.01-2.0 microg ml(-1) and C.V. at 0.075, 0.4 and 1.2 microg ml(-1) was < or = 4.96%. We are currently using this assay for monitoring TAM in plasma and investigating its pharmacokinetics in cancer patients receiving cytotoxic drugs in addition to TAM as a multi-drug resistance modifier. 相似文献
22.
AL Lindstrom SL Erlandsen JH Kersey CA Pennell 《Canadian Metallurgical Quarterly》1997,90(6):2323-2334
Vascular leak syndrome (VLS) is the dose-limiting toxicity observed in clinical trials of immunotoxins containing ricin toxin A chain (RTA). RTA itself is thought to cause VLS by damaging vascular endothelial cells, but the exact mechanism remains unclear. This is partially due to the paucity of appropriate models. To study VLS, we developed an in vitro model in which human umbilical vein-derived endothelial cells were first grown to confluence on microporous supports and then cultured under low pressure in the presence or absence of RTA. Endothelial cell barrier function was assessed by measuring the volume of fluid that passed through each monolayer per unit time. We found that RTA significantly increased monolayer permeability at times and concentrations consistent with the onset of VLS in patients treated with RTA-based immunotoxins. Scanning electron microscopy showed that intercellular gaps formed in endothelial monolayers exposed to RTA. Intercellular gap formation followed endothelial cell death caused by the enzymatic activity of RTA. We conclude that RTA is directly toxic to endothelial cells in vitro and speculate that this contributes to VLS in vivo. 相似文献
23.
SD Shiian SV Kha?dukov AL Pukhal''ski? AP Toptygina NV Bovin 《Canadian Metallurgical Quarterly》1996,41(2):24-29
The interaction of human peripheral blood leukocytes with alpha 1-acid glycoprotein (AGP), its glycoforms as well as neoglyco-conjugates representing carbohydrate chains of AGP or its fragments was studied by flow cytometry. It was shown that the main target cells for AGP as well as for conjugates of its carbohydrate chains with polyacrylamide (PAA) are monocytes and polymorphonuclear leukocytes but not lymphocytes. The interaction of AGP with monocytes and granulocytes are mediated by its carbohydrate chains: the binding of AGP with cells was inhibited by AGP, AGP oligosaccharides as well as conjugates of oligosaccharides and its fragments with PAA. The data obtained show the existence of monocyte (and granulocyte) receptors which interact with complex type sialooligosaccharides of AGP. 相似文献
24.
VM Coiro AL Segre A Di Nola M Paci A Grottesi G Veglia A Ballio 《Canadian Metallurgical Quarterly》1998,257(2):449-456
Pseudomycin A is a cyclic lipodepsinonapeptide phytotoxin produced by a strain of the plant pathogenic bacterium Pseudomonas syringae. Like other members of this family of bacterial metabolites, it is characterised by a fatty acylated cyclic peptide with mixed chirality and lactonic closure. Several biological activities of Pseudomycin A are lower than those found for some of its congeners, a difference which might depend on the diverse number and distribution of charged residues in the peptide moiety. Hence, it was of interest to investigate its conformation in solution. After the complete interpretation of the two-dimensional NMR spectra, NOE data were obtained and the structure was determined by computer simulations, applying distance geometry and molecular dynamics procedures. The conformation of the large ring of Pseudomycin A in solution includes three rigid structural regions interrupted by three short flexible regions that act as hinges. The overall three-dimensional structure of the cyclic moiety is similar to that of previously studied bioactive lipodepsinonapeptides produced by other pseudomonads. 相似文献
25.
26.
Two cases of congenital absence of a cervical vertebral pedicle are reported. This condition includes hypoplasia of the ipsilateral posterior arch and may predispose to spinal cord injury. The radiographic and computed tomography (CT) findings are reviewed, and the importance of the ipsilateral oblique radiographic view and of CT in diagnosis is stressed. 相似文献
27.
Examined the job performance of 420 credit managers (mean age at hiring 25 yrs) from a large finance company who either quit their job, were fired, or were promoted to a higher position in the company. Six biographical variables and 12 performance appraisal scores accumulated from data in employee files were used in a cross-validated multiple discriminant analysis to predict membership in the 3 classification groups. Results reveal a systematic relation between the performance appraisal variables and the classification groups: The performance of promoted Ss was significantly superior to that of Ss who quit, which in turn was significantly superior to the performance of the fired Ss. 18 discriminating variables accounted for a 46.7% hit rate in group membership. Findings are discussed in the context of research on performance antecedents of voluntary and involuntary turnover, as well as the feedback properties of performance appraisal information. It is suggested that no single performance–turnover relation exists. (14 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
28.
29.
30.
TV Hoang EU Choe HL Lippton AL Hyman LM Flint JJ Ferrara 《Canadian Metallurgical Quarterly》1996,61(2):330-338
To characterize the mesenteric alpha1- and alpha2-adrenoceptor populations in newborn piglets, an extracorporeal circuit was established to control intestinal blood flow in 0- to 2-day old and 10- to 14-day old animals. In both groups, alpha-adrenoceptor activation was first documented by observing dose-dependent increases in mesenteric perfusion pressure after intramesenteric arterial injection of alpha-adrenoceptor agonists. In the 10- to 14-day old piglets, mesenteric vasoconstrictor responses to alpha1-adrenoceptor agonists (methoxamine and norepinephrine) and an alpha2-adrenoceptor agonist (BHT-933) were each blunted (P < 0.05, analysis of variance) by peripheral intravenous injections of prazosin (an alpha1-adrenoceptor antagonist) and yohimbine (an alpha2-adrenoceptor antagonist), respectively. The mesenteric vasoconstrictor responses to those agonists were not significantly attenuated by prazosin or yohimbine in 0- to 2-day old animals, nor were they blunted by YM-12617 (alpha1-adrenoceptor antagonist) or idazoxan (alpha2-adrenoceptor antagonist)--compounds that are structurally unrelated to prazosin and yohimbine, respectively. In addition, mesenteric vasoconstrictor responses to other known vasoconstrictor agents--angiotensin II, neuropeptide Y, and a thromboxane A2 mimic (U-46619)--were not effected in either age group by prazosin or yohimbine, implying these agents act independently of alpha-adrenoceptor mechanisms. These data suggest that (1) there exists functional mesenteric alpha1- and alpha2-adrenoceptor-like activity in 10- to 14-day old piglets that, in 0- to 2-day old animals, is not specifically expressed; and (2) mesenteric alpha-adrenoceptor function becomes more selective as newborn piglets mature. 相似文献