全文获取类型
收费全文 | 6865篇 |
免费 | 118篇 |
国内免费 | 18篇 |
专业分类
电工技术 | 376篇 |
综合类 | 3篇 |
化学工业 | 1241篇 |
金属工艺 | 206篇 |
机械仪表 | 162篇 |
建筑科学 | 112篇 |
能源动力 | 174篇 |
轻工业 | 476篇 |
水利工程 | 34篇 |
石油天然气 | 6篇 |
无线电 | 637篇 |
一般工业技术 | 1208篇 |
冶金工业 | 1795篇 |
原子能技术 | 136篇 |
自动化技术 | 435篇 |
出版年
2023年 | 28篇 |
2022年 | 64篇 |
2021年 | 111篇 |
2020年 | 50篇 |
2019年 | 56篇 |
2018年 | 71篇 |
2017年 | 68篇 |
2016年 | 77篇 |
2015年 | 76篇 |
2014年 | 96篇 |
2013年 | 235篇 |
2012年 | 205篇 |
2011年 | 286篇 |
2010年 | 197篇 |
2009年 | 216篇 |
2008年 | 230篇 |
2007年 | 233篇 |
2006年 | 222篇 |
2005年 | 196篇 |
2004年 | 186篇 |
2003年 | 189篇 |
2002年 | 186篇 |
2001年 | 161篇 |
2000年 | 141篇 |
1999年 | 167篇 |
1998年 | 671篇 |
1997年 | 431篇 |
1996年 | 306篇 |
1995年 | 219篇 |
1994年 | 220篇 |
1993年 | 176篇 |
1992年 | 99篇 |
1991年 | 105篇 |
1990年 | 94篇 |
1989年 | 84篇 |
1988年 | 75篇 |
1987年 | 64篇 |
1986年 | 75篇 |
1985年 | 85篇 |
1984年 | 58篇 |
1983年 | 60篇 |
1982年 | 49篇 |
1981年 | 56篇 |
1980年 | 57篇 |
1979年 | 33篇 |
1978年 | 28篇 |
1977年 | 54篇 |
1976年 | 56篇 |
1975年 | 31篇 |
1973年 | 27篇 |
排序方式: 共有7001条查询结果,搜索用时 15 毫秒
931.
Y Tanaka Y Yoshida M Hirano M Morimoto T Kanaseki 《Canadian Metallurgical Quarterly》1993,107(6):522-526
The distribution of substance P (SP) and calcitonin gene-related peptide (CGRP) immunoreactive (ir) fibres in the cat's larynx was investigated utilizing immunohistochemistry. Many SP- and CGRP-ir fibres with varicosities were found within and below the epithelium and along the basement membrane of the mucosa of all different regions except in the membranous portion of the vocal fold. In the subepithelium, some SP- and CGRP-ir nerve bundles and nerve fibres were recognized around the vessels and glands. In the mucosa, the pattern of distribution and the density of SR-ir fibres were similar to those of CGRP-ir fibres. These reactive fibres were denser in the supraglottic region than in the subglottic region. In the taste bud-like structures, only SP-ir fibres appeared, whereas in the motor endplates, CGRP-reaction was found exclusively. The present findings suggest that the regional distribution of SP- and CGRP-immunoreactivity might be related with sensory and autonomic innervation in the larynx. 相似文献
932.
Three experiments tested the ability to integrate information about object–object relationships in 2 chimpanzees. In Experiment 1, the subjects were trained to match 1 part of a 2-part object to its other part, match a tool to its assembled object, match a container to its tool, and match a tool to its container. In Experiment 2, the subjects were trained to match a picture of the sample. One subject learned this type of matching task and was then tested on whether she could choose the pictures of related items in Experiment 1. Although the subject was reinforced irrespective of her choices, she chose pictures of items related to the sample when there was no picture of the sample. Experiment 3 showed that the subject was able to match a picture of the item among related items. The results suggest that the subject might integrate information about relationships acquired in Experiment 1 and organize it to make networks of related items. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
933.
G Richard AR Wright S Harris SZ Doyle B Korge C Mazzanti T Tanaka W Harth OW McBride JG Compton 《Canadian Metallurgical Quarterly》1994,103(5):665-668
Darier's disease (DD) is an autosomal dominant genodermatosis characterized by epidermal acantholysis and dyskeratosis. We have performed genetic linkage studies in 10 families with DD (34 affected) by analyzing 14 polymorphic microsatellite markers. Our results confirm recent reports mapping the DD gene to chromosome 12q23-q24.1. Haplotype analysis of recombinant chromosomes in our families, along with previously reported data, narrow the location of the DD gene to a 5 cM interval flanked by the loci D12S354 and D12S84/D12S105. This localization allowed exclusion of two known genes, PLA2A and PAH, as candidate loci for DD. Three other gene loci (PPP1C, PMCH, PMCA1), mapping in 12q21-q24, remain potential candidates. 相似文献
934.
935.
K Koike T Kawabe T Tanaka S Toh T Uchiumi M Wada S Akiyama M Ono M Kuwano 《Canadian Metallurgical Quarterly》1997,57(24):5475-5479
The human cMOAT gene encodes a membrane protein involved in the ATP-dependent transport of hydrophobic compounds. To determine whether cMOAT is associated with drug sensitivity, we transfected an expression vector containing cMOAT antisense cDNA into the HepG2 human hepatic cancer cell line. We observed a reduction in cMOAT protein, as well as an enhanced level of glutathione, in the antisense transfectants. The transfectants displayed an increased sensitivity to cisplatin, vincristine, doxorubicin, and the camptothecin derivatives, (4S)-4,11-diethyl-4-hydroxy-9-[(4-piperidinopiperidino)carbonyl oxy]dione hydrochloride triethydrate and 7-ethyl-10-hydroxycamptothecin, but not to etoposide, 3-[4-amino-2-methyl-5-pyrimidinyl)methyl]-1-(2-chloroethyl)-1-nitrosoure a, 5-fluorouracil, and mitomycin C. Results suggest that cMOAT levels are inversely correlated with those of glutathione, and that cMOAT and its related genes may be involved in the sensitivity of cells to certain anticancer agents. 相似文献
936.
[Correction Notice: An erratum for this article was reported in Vol 75(1) of Journal of Applied Psychology (see record 2008-10492-001). An error exists in Figure 2 and the accompanying text of the article. The corrected information is included in the erratum.] The problem of assessing fit of structural equation models is reviewed, and two sampling studies are reported that examine the effects of sample size, estimation method, and model misspecification on fit indices. In the first study, the behavior of indices in a known-population confirmatory factor analysis model is considered. In the second study, the same problem in an empirical data set is examined by looking at antecedents and consequences of work motivation. The findings across the two studies suggest that (a) as might be expected, sample size is an important determinant in assessing model fit; (b) estimator-specific, as opposed to estimator-general, fit indices provide more accurate indications of model fit; and (c) the studied fit indices are differentially sensitive to model misspecification. Some recommendations for the use of structural equation model fit indices are given. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
937.
A Tahara M Saito T Sugimoto Y Tomura K Wada T Kusayama J Tsukada N Ishii T Yatsu W Uchida A Tanaka 《Canadian Metallurgical Quarterly》1998,125(7):1463-1470
Three subtypes of human (h) arginine vasopressin (AVP) receptors, hV1A, hV1B and hV2, were stably expressed in Chinese hamster ovary (CHO) cells and characterized by [3H]-AVP binding studies. In addition, the coupling of the expressed receptor protein to a variety of signal transduction pathways was investigated. Scatchard analysis of saturation isotherms for the specific binding of [3H]-AVP to membranes, prepared from CHO cells transfected with hV1A, hV1B and hV2 receptors, yielded an apparent equilibrium dissociation constant (Kd) of 0.39, 0.25 and 1.21 nM and a maximum receptor density (Bmax) of 1580 fmol mg(-1) protein, 5230 fmol mg(-1) protein and 7020 fmol mg(-1) protein, respectively. Hill coefficients did not differ significantly from unity, suggesting binding to homogenous, non-interacting receptor populations. Pharmacological characterization of the transfected human AVP receptors was undertaken by measuring the relative ability of nonpeptide AVP receptor antagonists, YM087, OPC-21268, OPC-31260, SR 49059 and SR 121463A, to inhibit binding of [3H]-AVP. At hV1A receptors, the relative order of potency was SR49059>YM087>OPC-31260>SR 121463A> >OPC-21268 and at hV2 receptors, YM087=SR 121463A>OPC-31260>SR 49059> >OPC-21268. In contrast, the relative order of potency, at hV1B receptors, was SR 49059> >SR 121463A=YM087=OPC-31260=OPC-21268. In CHO cells expressing either hV1A or hV1B receptors, AVP caused a concentration-dependent increase in intracellular Ca2+ concentration ([Ca2+]i) with an EC50 value of 1.13 nM and 0.90 nM, respectively. In contrast, stimulation of CHO cells expressing hV2 receptors resulted in an accumulation of cyclic AMP with an EC50 value of 2.22 nM. The potency order of antagonists in inhibiting AVP-induced [Ca2+]i or cyclic AMP response was similar to that observed in radioligand binding assays. In conclusion, we have characterized the pharmacology of human cloned V1A, V1B and V2 receptors and used these to determine the affinity, selectivity and potency of nonpeptide AVP receptor antagonists. Thus they may prove to be a valuable tool in further examination of the physiological and pathophysiological roles of AVP. 相似文献
938.
The regulation of glucose metabolism by glucagon and GLP-1 is well established, but novel functions for these and other proglucagon-derived peptides are less well defined. This paper highlights the diversity of both GLP-1 and glucagon activity by studying the tissue distribution of glucagon and GLP-1 receptor gene expression by both Southern blot analysis of RT-PCR products and nuclease protection assays. By Southern blot analysis of RT-PCR products, GLP-1 receptor mRNA was detected in lung, hypothalamus, hippocampus, cerebral cortex, kidney, pancreas, and throughout the gastrointestinal tract. Glucagon receptor expression was detected in liver, kidney, spleen, thymus, adrenal glands, pancreas, cerebral cortex, lung, and throughout the gastrointestinal tract. Nuclease protection assay revealed glucagon receptor expression to be highest in liver and kidney, whereas GLP-1 receptor expression was only detected by protection assay in lung, stomach, and large bowel. Despite previous evidence that other receptors for proglucagon-derived peptides may exist, no evidence of novel receptors or multiple isoforms of the glucagon and GLP-1 receptors was found, indicating that the two cloned receptors may mediate all the effects of proglucagon-derived peptides, or that novel receptors may share less homology with the glucagon and GLP-1 receptors than previously anticipated. 相似文献
939.
940.
T Tanaka H Makita T Kawamori K Kawabata H Mori A Murakami K Satoh A Hara H Ohigashi K Koshimizu 《Canadian Metallurgical Quarterly》1997,18(5):1113-1118
The modifying effect of dietary administration of a xanthine oxidase inhibitor 1'-acetoxychavicol acetate (ACA) present in an edible plant Languas galanga in Thailand on the development of azoxymethane (AOM)-induced colonic aberrant crypt foci (ACF) was investigated in rats. Male F344 rats were given s.c. injections of AOM (15 mg/kg body wt) once a week for 3 weeks to induce colonic ACF. They were fed the diets containing 100 or 200 ppm ACA for 5 weeks, starting 1 week before the first dosing of AOM. At the termination of the study (week 5), AOM induced 118 +/- 28 ACF/colon. Dietary administration of ACA caused significant reduction in the frequency of ACF (41% inhibition by 100 ppm ACA feeding and 37% inhibition by 200 ppm ACA feeding, P<0.01). Such inhibition might be associated with suppression of the proliferation biomarkers' expression such as ornithine decarboxylase activity in the colonic mucosa, number of silver-stained nucleolar organizer regions' protein in the colonic mucosal cell nuclei and blood polyamine content. These results indicate that ACA could inhibit the development of AOM-induced ACF through its suppression of cell proliferation in the colonic mucosa and ACA might be a possible chemopreventive agent against colon tumourigenesis. 相似文献