全文获取类型
收费全文 | 5873篇 |
免费 | 6篇 |
国内免费 | 1篇 |
专业分类
综合类 | 1篇 |
化学工业 | 30篇 |
金属工艺 | 3篇 |
机械仪表 | 1篇 |
建筑科学 | 1篇 |
矿业工程 | 2篇 |
能源动力 | 1篇 |
轻工业 | 18篇 |
无线电 | 3篇 |
一般工业技术 | 10篇 |
冶金工业 | 5807篇 |
自动化技术 | 3篇 |
出版年
2020年 | 4篇 |
2019年 | 1篇 |
2018年 | 2篇 |
2017年 | 4篇 |
2016年 | 2篇 |
2015年 | 1篇 |
2014年 | 4篇 |
2013年 | 3篇 |
2012年 | 2篇 |
2011年 | 3篇 |
2010年 | 4篇 |
2008年 | 2篇 |
2007年 | 4篇 |
2006年 | 3篇 |
2005年 | 3篇 |
2004年 | 6篇 |
2003年 | 12篇 |
2002年 | 1篇 |
2000年 | 2篇 |
1999年 | 184篇 |
1998年 | 1915篇 |
1997年 | 1096篇 |
1996年 | 701篇 |
1995年 | 377篇 |
1994年 | 275篇 |
1993年 | 357篇 |
1992年 | 42篇 |
1991年 | 42篇 |
1990年 | 53篇 |
1989年 | 44篇 |
1988年 | 36篇 |
1987年 | 38篇 |
1986年 | 35篇 |
1985年 | 44篇 |
1984年 | 1篇 |
1983年 | 9篇 |
1982年 | 19篇 |
1981年 | 37篇 |
1980年 | 52篇 |
1979年 | 2篇 |
1978年 | 14篇 |
1977年 | 130篇 |
1976年 | 291篇 |
1975年 | 13篇 |
1974年 | 1篇 |
1973年 | 2篇 |
1972年 | 1篇 |
1965年 | 1篇 |
1963年 | 1篇 |
1955年 | 4篇 |
排序方式: 共有5880条查询结果,搜索用时 15 毫秒
141.
EA Liberman AM Arzumanian MA Vladimirova LM Tsofina 《Canadian Metallurgical Quarterly》1976,21(3):476-481
"Zero-loop" of the molecular potential transformer of submitochondrial particles (SMP) is separated from the remaining electron transfer chain by rotenone, and its e.m.f. ET=0,003+RT/2F in [NADP X H] [NAD+]/[NADP+] [NAD X H] volts is used in the compensative method of measurement of the potential difference across the SMP membrane (delta USMP). The phospholipid membrane, measuring the concentration of the penetrating anions in the solution contained SMP, is used as "zero-indicators". This concentration drops monotonically with increase in delta USMP. Delta USMP is equal to ET when the addition of substrates of transhydrogenase reaction with definite ET does not change the potential across phospholipid membrane. 相似文献
142.
Clinical and immunocytochemical analysis of twenty eight cases of giant cell tumour of bone was performed in this study. The results revealed that nine of the cases were benign, while the other nineteen were malignant. The female to male ratio was 2.5:1. The average age incidence was 28.18 years. The most common site of occurrence was the femur. anti endothelial antibody revealed negative immunocytochemical reaction of the stromal cells and giant cells for both benign and malignant cases; While using anti-HLA-DR antibody demonstrated positive immune reaction of some of the strumal and giant cells of all the cases examined. 相似文献
143.
144.
AM Rauck FB Ruymann K Klopfenstein N Grossman R Rosselet L Grovas S Ceselski J Hayes AC Grovas 《Canadian Metallurgical Quarterly》1998,13(4):146-154
PURPOSE: Peripheral blood stem cell (PBSC) apheresis provides an alternative to autologous marrow harvest as a source of hematologic stem cells for transplantation in children with solid tumors. PATIENTS AND METHODS: Eight children with metastatic or recurrent solid tumors underwent 27 apheresis procedures. Recovery from myelosuppressive chemotherapy occurred without continuous daily growth factor support prior to mobilization. Granulocyte colony stimulating factor (G-CSF) at 16 microgs/kg/day was used to increase stem cells in the peripheral circulation. CD 34 positive cells, mononuclear cells (MNC), and CFU-GM were measured in the apheresis products. Prior chemotherapy was examined as a clinical factor that affected PBSC yield. RESULTS: A significant correlation was found between CD 34+/kg and CFU-GM/kg of the products (r = 0.758, P < 0.001). Patients receiving cumulative doses of carboplatin over 1,600 mg/m2 produced adequate MNC (1 x 10(8)/kg) but yielded significantly less CD 34+ cells or CFU-GM than those patients receiving less carboplatin. Prior doses of etoposide and ifosfamide did not effect PBSC yield. CONCLUSIONS: The mobilization technique was well tolerated, and the products obtained produced trilineage engraftment in the patients that underwent peripheral blood stem cell transplantation. Peripheral blood stem cell apheresis in children can be optimized by selection of appropriate candidates and mobilization with G-CSF after an absence of hematopoietic growth factor support. 相似文献
145.
BM Cadre M Qi DM Eble TR Shannon DM Bers AM Samarel 《Canadian Metallurgical Quarterly》1998,30(11):2247-2259
Abnormal intracellular Ca2+ handling in hypertrophied and failing hearts is partly due to changes in Ca2+ transporter gene expression, but the mechanisms responsible for these alterations remain largely unknown. We previously showed that intrinsic mechanical load (i.e. spontaneous contractile activity) induced myocyte hypertrophy, and down-regulated SR Ca2+ ATPase (SERCA2) gene expression in cultured neonatal rat ventricular myocytes (NRVM). In the present study, we examined whether extrinsic mechanical load (i.e. cyclic stretch) also induced NRVM hypertrophy, and led to down-regulation of SERCA2 and other Ca2+ transporter genes which have been associated with cardiac hypertrophy and failure in vivo. NRVM were maintained in serum-free culture medium under control conditions, or subjected to cyclic mechanical deformation (1.0 Hz, 20% maximal strain, 48 h). Under these conditions, cyclic stretch induced NRVM hypertrophy, as evidenced by significant increases in total protein/DNA ratio, myosin heavy chain (MHC) content, and atrial natriuretic factor (ANF) secretion. Cyclic stretch also induced the MHC isoenzyme "switch" which is characteristic of hemodynamic overload of the rat heart in vivo. Cyclic stretch significantly down-regulated SERCA2 and ryanodine receptor (RyR) mRNA and protein levels, while simultaneously increasing ANF mRNA. In contrast, Na+-Ca2+ exchanger and phospholamban mRNA levels were unaffected. Load-dependent SERCA2 and RyR down-regulation was independent of Ca2+ influx via voltage-gated, L-type Ca2+ channels, as cyclic stretch down-regulated SERCA2 and RyR mRNA levels in both control and verapamil-treated NRVM. These results indicate that extrinsic mechanical load (in the absence of other exogenous stimuli) induces NRVM hypertrophy and causes down-regulation of Ca2+ transporter gene expression. This in vitro model system should prove useful to dissect the intracellular signaling pathways responsible for transducing this phenotype during cardiac hypertrophy and heart failure in vivo. 相似文献
146.
AM Bravo-Angel HA Becker R Kunze B Hohn WH Shen 《Canadian Metallurgical Quarterly》1995,248(5):527-534
A reverse genetic system for studying excision of the transposable element Ds1 in maize plants has been established previously. In this system, the Ds1 element, as part of the genome of maize streak virus (MSV), is introduced into maize plants via agroinfection. In the presence of the Ac element, excision of Ds1 from the MSV genome results in the appearance of viral symptoms on the maize plants. Here, we used this system to study DNA sequences required in cis for excision of Ds1. The Ds1 element contains the Ac transposase binding motif AAACGG in only one of its subterminal regions (defined here as the 5' subterminal region). We showed that mutation of these motifs abolished completely the excision capacity of Ds1. This is the first direct demonstration that the transposase binding motifs are essential for excision. Mutagenesis with oligonucleotide insertions in the other (3') subterminal region resulted in elements with either a reduced or an increased excision efficiency, indicating that this subterminal region also has an important function. 相似文献
147.
Using a previous model, which was developed to describe the light-induced creation of the defect density in the a-Si:H gap states, we present in this work a numerical modelling of the photodegradation effect in the a-Si:H p-i-n solar cell under continuous illumination. We first considered the simple case of a monochromatic light beam with a wavelength λ between 530-540 nm non uniformly absorbed, then the global standard solar spectrum (AM 1.5) illumination is taken into account. The photodegradation is analysed on the basis of the resulting changes in the free carrier's densities, recombination rate, band structure, electrical potential and field, space charge, and current densities. Changes in the cell's external parameters: the open circuit voltage Voc, the short circuit current density Jsc, the fill factor FF and the maximum power density Pmax are also presented. 相似文献
148.
AC Rosa AT Mariano AM Pereira A Tibana TA Gomes JR Andrade 《Canadian Metallurgical Quarterly》1998,47(9):781-790
Faeces from urban children < 2 years old with acute diarrhoeal illness and from non-diarrhoeal infants (controls) were examined for Escherichia coli and other enteropathogens. A total of 990 E. coli isolates from 100 patients and 50 controls was tested for enteropathogenic E. coli (EPEC) serotype (O:H), adherence to HEp-2 cells after incubation for 3 and 6 h, fluorescent actin staining (FAS), DNA hybridisation with EAF, eaeA, STh, STp and EAggEC probes and production of heat-labile enterotoxin (LT) and verocytotoxin (VT) with Y1 and Vero cells. EPEC were the most prevalent enteropathogens in patients (32.7%; and 14% in controls). Enteroinvasive E. coli (EIEC) and Vero cytotoxin-producing E. coli (VTEC) were not detected. The rate of isolation of enterotoxigenic E. coli (ETEC) was identical in both groups. Among the EPEC isolates the prevalent serotypes were O111:H2, O55:NM and O119:H6. Localised adherence (LA) was found significantly more frequently in isolates from patients (19.6%) than controls (2.1%). All LA-positive EPEC isolates were FAS+ and eaeA+, but only 75.2% of them hybridised with the EAF probe. Diffusely adhering E. coli (DAEC) and enteroaggregative E. coli (EAggEC) were found with equal frequency in patients and controls. Twenty-seven E. coli isolates were negative for EAF but positive for eaeA and FAS and produced LA in 6-h adherence tests. These EAF-/eaeA+ strains were the only putative enteropathogen identified in seven patients and were not found in controls. The ability of these strains to elicit ultrastructural cell alterations and cell-signalling events was evaluated in Caco-2 cells (human colon carcinoma cell line) by the gentamicin invasion assay and by transmission electron microscopy. The numbers of intracellular bacteria in cell invasion tests varied from 0.4% to 1.6% of the cell-associated bacteria after a 6-h incubation period. Tyrosine phosphorylation of host cell proteins was assessed in HEp-2 cells by immunofluorescence microscopy and all strains gave positive results. EAF-/eaeA+ E. coli strains express most of the virulence properties found among true EPEC strains and can be a relevant cause of infant diarrhoea in developing countries. 相似文献
149.
M Tormo AM Tari TJ McDonnell F Cabanillas J Garcia-Conde G Lopez-Berestein 《Canadian Metallurgical Quarterly》1998,30(3-4):367-379
The roles of Bcl-2 protein and the protein ratio of Bcl-2/Bax in regulating cell growth in various lymphoma cell lines were examined. A dose-dependent decrease in Bcl-2 protein expression was observed in the different lymphomas incubated with lipid-incorporated bcl-2 antisense oligonucleotides (L-bcl-2). Growth inhibition was observed in a transformed follicular lymphoma (FL) cell line, which has the t(14;18) translocation and Bcl-2 protein overexpression. One of the mechanisms by which L-bcl-2 growth inhibition is mediated in these transformed FL cells might be through apoptotic induction, because the treated cells had an increased apoptotic index and showed the typical DNA fragmentation. These studies indicate that Bcl-2 protein is critical in the growth regulation of transformed FL cells. L-bcl-2 did not induce growth inhibition in lymphoma cells not expressing Bcl-2 or Bax protein. Thus, the protein ratio of Bcl-2/Bax may also be important in regulating the growth of these lymphomas. 相似文献
150.
AN Reshetilov DA Efremov PV Iliasov AM Boronin NI Kukushskin RV Greene TD Leathers 《Canadian Metallurgical Quarterly》1998,13(7-8):795-799
Amperometric biosensors register oxygen depletion in response to analyte catabolism, and thus are limited by the availability of dissolved oxygen. Microbial sensors containing immobilized cells of Gluconobacter oxydans were hyperoxygenated to 400% of control levels and the effects on sensor responses to glucose were determined. Oxygenated perfluorodecalin (a completely fluorinated organic substance) was as effective in hyperoxygenation as direct sparging with O2, increasing sensor base medium oxygen concentrations from 9.3 to 37 mg/l. Hyperoxygenation enhanced maximal biosensor response amplitudes, particularly at high cell loading densities. Maximal response rates were also improved, although less dramatically. Results suggest that hyperoxygenation may be a new general approach for modulating biosensor responses. 相似文献