全文获取类型
收费全文 | 7176篇 |
免费 | 186篇 |
国内免费 | 17篇 |
专业分类
电工技术 | 305篇 |
综合类 | 5篇 |
化学工业 | 1524篇 |
金属工艺 | 166篇 |
机械仪表 | 183篇 |
建筑科学 | 169篇 |
矿业工程 | 1篇 |
能源动力 | 204篇 |
轻工业 | 679篇 |
水利工程 | 37篇 |
石油天然气 | 8篇 |
无线电 | 620篇 |
一般工业技术 | 1264篇 |
冶金工业 | 1399篇 |
原子能技术 | 222篇 |
自动化技术 | 593篇 |
出版年
2023年 | 39篇 |
2022年 | 64篇 |
2021年 | 143篇 |
2020年 | 67篇 |
2019年 | 80篇 |
2018年 | 128篇 |
2017年 | 91篇 |
2016年 | 161篇 |
2015年 | 87篇 |
2014年 | 166篇 |
2013年 | 379篇 |
2012年 | 260篇 |
2011年 | 367篇 |
2010年 | 252篇 |
2009年 | 313篇 |
2008年 | 329篇 |
2007年 | 254篇 |
2006年 | 264篇 |
2005年 | 230篇 |
2004年 | 214篇 |
2003年 | 220篇 |
2002年 | 209篇 |
2001年 | 147篇 |
2000年 | 122篇 |
1999年 | 175篇 |
1998年 | 533篇 |
1997年 | 371篇 |
1996年 | 272篇 |
1995年 | 153篇 |
1994年 | 157篇 |
1993年 | 168篇 |
1992年 | 72篇 |
1991年 | 69篇 |
1990年 | 68篇 |
1989年 | 67篇 |
1988年 | 57篇 |
1987年 | 43篇 |
1986年 | 67篇 |
1985年 | 72篇 |
1984年 | 48篇 |
1983年 | 52篇 |
1982年 | 41篇 |
1981年 | 45篇 |
1980年 | 43篇 |
1979年 | 29篇 |
1978年 | 20篇 |
1977年 | 36篇 |
1976年 | 50篇 |
1975年 | 16篇 |
1973年 | 14篇 |
排序方式: 共有7379条查询结果,搜索用时 203 毫秒
981.
T Yamamoto T Watanabe N Ikegaya Y Fujigaki K Matsui H Masaoka M Nagase A Hishida 《Canadian Metallurgical Quarterly》1998,9(12):2253-2261
Protein and mRNA expression of transforming growth factor-beta (TGF-beta) receptor type I (TbetaRI), type II (TbetaRII), and type III (TbetaRIII) were studied in serial sections of kidney samples obtained from patients with glomerulonephritis. In minimal change disease, weak expression of TbetaRI and TbetaRII was observed mainly in glomerular endothelial cells, peritubular capillaries, and interstitial arteriolar endothelial cells, whereas TbetaRIII expression was found mainly in the interstitium. Expression of all three TGF-beta receptors (TbetaR) was increased remarkably in glomerular and Bowman's capsular cells comprising the tuft adhesions to Bowman's capsules in glomerulonephritis with increased matrix accumulation, including IgA nephropathy, lupus nephritis, focal and segmental glomerulosclerosis, myeloperoxidase-antineutrophil cytoplasmic antibody-associated crescentic glomerulonephritis, and membranoproliferative glomerulonephritis. Increased expression of the three TbetaR was also seen in glomerular epithelial cells in the vicinity of glomerulosclerotic lesions, in crescent cells, and in some tubules and infiltrative mononuclear cells found in the periglomerular and tubulointerstitial lesions with increased matrix deposition. In contrast, no remarkable TbetaRII expression was noted in mesangial proliferative lesions in IgA nephropathy, lupus nephritis, and membranoproliferative glomerulonephritis. These data suggest that distinctive modulation of TbetaR expression may be involved in the development of adhesive, sclerotic, and proliferative renal lesions in human glomerulonephritis. 相似文献
982.
A Nakajima N Watanabe S Yoshino H Yagita K Okumura M Azuma 《Canadian Metallurgical Quarterly》1997,9(5):637-644
The interaction between CD28 and its ligands, CD80 and CD86, is crucial for an optimal activation of antigen-specific T cells. However, the requirement of CD80 or CD86 co-stimulation in Th2 cell differentiation and activation is controversial. Freshly isolated murine CD4+ and CD8+ T cells were incubated with P815 transfectants expressing a similar level of either CD80 or CD86 in the presence of anti-CD3 mAb. Both CD80 and CD86 co-stimulated the proliferation of CD4+ and CD8+ T cells at comparable time-kinetics and magnitude, but CD86 alone was able to co-stimulate IL-4 and especially IL-10 production in CD4+ T cells. In typical Th2-dependent immune responses elicited by Nippostrongylus brasillensis infection, the anti-CD86 mAb treatment but not the anti-CD80 mAb treatment efficiently inhibited antigen-specific IgE and IgG1 production, which was accompanied with the reduced IL-4 production. Our results suggest that CD86 co-stimulation plays a dominant role not only in the primary activation of Th2 cells but also in the secondary interaction between antigen-primed Th2 cells and B cells. 相似文献
983.
Ikemoto Satoshi; Murphy James M.; McBride William J. 《Canadian Metallurgical Quarterly》1997,111(2):369
This study used an intracerebral self-administration paradigm in rats to determine if blockade of GABAA receptors in the ventral tegmental area (VTA) has a reinforcing effect. Rats quickly learned to self-infuse a picrotoxin solution into the anterior VTA; rats discriminated the lever that produced picrotoxin infusions from the lever without consequences; and when the response requirement was increased, rats increased response levels for picrotoxin infusion. The reinforcing effect of picrotoxin was site-specific: Anterior VTA regions supported vigorous self-infusions, but not the posterior VTA, substantia nigra, or lateral hypothalamus. Muscimol, a GABAA agonist, disrupted picrotoxin self-infusion, but bicuculline, a GABAA antagonist, was self-infused into the VTA. The results suggest that blockade of GABAA receptors in the anterior VTA is reinforcing and that functional organization of the GABA systems within the VTA is heterogeneous. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
984.
BACKGROUND: Subpopulations of c-Kit immunopositive cells in the muscle coat of the gastrointestinal tract are considered pacemaker cells and have been investigated in human tissue relating to motility disorder. However, the morphology of c-kit immunopositive cells in intact human tissue is still unclear. METHODS: The authors studied the distribution of c-Kit immunopositive cells in the normal human colon and their cellular configuration by confocal microscopy on whole-mount preparations. The authors then compared them with six cases of Hirschsprung's disease (HD; two of short segment aganglionosis, three of extensive aganglionosis, and one of total aganglionosis). RESULTS: In the normal colon regional differences were found in the distribution of c-Kit immunopositive cells. The population in the muscle layers and at the submucosal border was larger in the anal part than in the oral part. Accumulation of positive cells at the myenteric plexus level was prominent only at the descending colon. In the descending colon of HD the authors could not demonstrate any differences in c-Kit immunopositive cells on aganglionic segments compared with the corresponding area of intact tissue. CONCLUSION: More attention must be paid to these regional differences of distribution, and identical regions of affected and unaffected bowels must be compared when discussing the relation between the abnormality of c-Kit-positive cells and motility disorders including HD. 相似文献
985.
Two new alcoholic aroma precursors, cis- and trans-linalool, 3,7-oxides 6-O-beta-D-apiofuranosyl-beta-D-glucopyranosides (1 and 2), as well as two already known compounds, (Z)-3-hexenyl beta-D-glucopyranoside (3) and methyl salicylate 6-O-beta-D-xylopyranosyl-beta-D-glucopyranoside (beta-primeveroside: 4), and another new monoterpendiol glycoside, 8-hydroxygeranyl beta-primeveroside (5) have recently been isolated as aroma precursors in tea leaves (Camellia sinensis var. sinensis cv. Maoxie) ready for oolong tea processing. 相似文献
986.
A molybdenum single crystal with an optional shape was produced by the secondary recrystallization method. First, a specimen with an optional shape was mechanically fabricated by drilling, punching or bending from a hot-rolled sheet doped with CaO and MgO. Then the specimen was isothermally annealed at 2300°C for 1 h. 相似文献
987.
988.
Transmission loss increase of optical glass fibre caused by hydrogen diffusion is measured as a function of temperature and partial pressure of hydrogen gas. The activation energy of hydroxyl group formation from the diffused molecular hydrogen was found to be 15.9 kcal/mole. Also the hydroxyl absorption loss increase at 200°C was found to be proportional to the square root of the partial pressure of hydrogen gas. 相似文献
989.
990.