全文获取类型
收费全文 | 252962篇 |
免费 | 2798篇 |
国内免费 | 870篇 |
专业分类
电工技术 | 4809篇 |
综合类 | 193篇 |
化学工业 | 36146篇 |
金属工艺 | 9509篇 |
机械仪表 | 7546篇 |
建筑科学 | 6077篇 |
矿业工程 | 880篇 |
能源动力 | 7234篇 |
轻工业 | 21098篇 |
水利工程 | 2202篇 |
石油天然气 | 3230篇 |
武器工业 | 15篇 |
无线电 | 34292篇 |
一般工业技术 | 49998篇 |
冶金工业 | 48554篇 |
原子能技术 | 5075篇 |
自动化技术 | 19772篇 |
出版年
2021年 | 2181篇 |
2020年 | 1565篇 |
2019年 | 1926篇 |
2018年 | 3276篇 |
2017年 | 3315篇 |
2016年 | 3411篇 |
2015年 | 2220篇 |
2014年 | 3961篇 |
2013年 | 11482篇 |
2012年 | 6234篇 |
2011年 | 8577篇 |
2010年 | 6911篇 |
2009年 | 7888篇 |
2008年 | 8403篇 |
2007年 | 8298篇 |
2006年 | 7363篇 |
2005年 | 6498篇 |
2004年 | 6285篇 |
2003年 | 6554篇 |
2002年 | 6036篇 |
2001年 | 6514篇 |
2000年 | 5973篇 |
1999年 | 6389篇 |
1998年 | 16486篇 |
1997年 | 11408篇 |
1996年 | 8793篇 |
1995年 | 6607篇 |
1994年 | 5901篇 |
1993年 | 5844篇 |
1992年 | 4131篇 |
1991年 | 4021篇 |
1990年 | 3857篇 |
1989年 | 3649篇 |
1988年 | 3560篇 |
1987年 | 3021篇 |
1986年 | 2943篇 |
1985年 | 3206篇 |
1984年 | 2927篇 |
1983年 | 2828篇 |
1982年 | 2636篇 |
1981年 | 2543篇 |
1980年 | 2461篇 |
1979年 | 2305篇 |
1978年 | 2109篇 |
1977年 | 2605篇 |
1976年 | 3564篇 |
1975年 | 1764篇 |
1974年 | 1729篇 |
1973年 | 1665篇 |
1972年 | 1465篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
911.
In this report, the role of 34 kDa HA-binding protein in hyaluronic acid-induced cellular signalling in lymphocytes has been examined. The binding of 125I-HA to lymphocytes in vivo was found to be inhibited by pre-incubation of the cells with anti-34 kDa HA-binding protein antibodies, thus confirming 34 kDa HA-binding protein as the specific HA-receptor in lymphocytes. This observation was substantiated by anti-34 kDa HA-binding protein antibodies immunoblotting and 125I-HA ligand blotting of lymphocytes cell lysate. The HA-induced cell aggregation, tyrosine phosphorylation and cytoskeletal protein phosphorylation demonstrate the HA-induced early cellular signalling events in lymphocytes. Further, to study the involvement of 34 kDa HA-binding protein in mitogen induced lymphocyte signalling, we studied in vivo phosphorylation and secondary messenger formation. The enhanced 34 kDa HA-binding protein phosphorylation by HA and the inhibition of cellular aggregation and IP3 formation by anti-HA-binding protein antibodies revealed that 34 kDa HA-binding protein is one of the potential mediators in HA-induced signal transduction. 相似文献
912.
T Yokoyama H Gondo Y Tanaka K Takenaka K Tanimoto M Nakamura Y Niho 《Canadian Metallurgical Quarterly》1996,37(4):358-361
A 62-year-old Japanese man complained of fever, general fatigue, anorexia and watery diarrhea during remission of adult T-cell leukemia-lymphoma. Laboratory examinations showed severe hypoproteinemia (2.9 g/dl). However, neither intestinal lesions associated with ATL nor findings suggesting protein losing gastroenteropathy were observed. Cytomegalovirus (CMV) antigen detection assay using peripheral blood leukocytes revealed that he had an active CMV infection with hemophagocytic syndrome. Treatment with ganciclovir and methylprednisolone led to an improvement of hypoproteinemia. CMV disease and associated hemophagocytic syndrome should be considered as a cause of hypoproteinemia in an immunocompromised host. 相似文献
913.
R Lehtinen H Siev?nen J Viik V Turjanmaa K Niemel? J Malmivuo 《Canadian Metallurgical Quarterly》1996,78(9):1002-1006
In this comparative cross-sectional study, we evaluated whether a novel computerized diagnostic variable, ST-segment depression/heart rate ST/HR analysis during both the exercise and postexercise recovery phases of the exercise electrocardiography (ECG) test, can detect coronary artery disease more accurately than methods using either exercise or recovery phase alone. The study population comprised 347 clinical patients referred for a routine bicycle exercise ECG test at Tampere University Hospital, Finland. Of these, 127 had angiographically proven coronary artery disease, whereas 13 had no coronary artery disease according to angiography, 18 had no perfusion defect according to technetium-99m sestamibi single-photon emission computed tomography, and 189 were clinically normal with respect to cardiac diseases. For each patient, the maximum values of the ST/HR hysteresis, ST/HR index, end-exercise ST depression, and recovery ST depression were determined from the Mason-Likar modification of the standard 12-lead exercise electrocardiogram [aVL, aVR, and V1 excluded]. The diagnostic performance of these continuous diagnostic variables was compared by means of receiver-operating characteristic analysis. The area under the receiver-operating characteristic curve of the ST/HR hysteresis was 89%, which was significantly larger than that of the end-exercise ST depression (76%, p < or = 0.0001), recovery ST depression (84%, p = 0.0063), or ST/HR index (83%, p = 0.0023), indicating superior diagnostic performance of the ST/HR hysteresis independent of the partition value selection. In conclusion, computerized analysis of the HR-adjusted ST depression pattern during the exercise phase, integrated with the HR-adjusted ST depression pattern during the recovery phase after exercise, can significantly improve the diagnostic performance and clinical utility of the exercise ECG test for the detection of coronary artery disease. 相似文献
914.
E Asakura T Hanamura A Umemura K Yada T Yamauchi T Tanabe 《Canadian Metallurgical Quarterly》1996,195(3):300-313
M-CSF is a macrophage-lineage-specific growth factor that causes proliferation and differentiation of progenitor cells in the bone marrow. To investigate the effects of M-CSF on more matured cells, human monocytes were cultured in the presence or absence of M-CSF for 6 days. Addition of M-CSF at more than 10(2) U/ml resulted in higher viability and caused morphological differentiation to large macrophage-like cells. LPS-induced mediator production was also compared between M-CSF-treated and control cell. Monocytes were incubated with or without M-CSF for 3 days, and were stimulated with 1 microgram/ml of LPS for 2 days. IL-1 beta was not detected in the both culture supernatants, and PGE2 production was not influenced by M-CSF. However, amounts of G-CSF, GM-CSF, IL-6, and TNF-alpha produced in response to 1 microgram/ml of LPS were 1.5 to 2 times greater from monocytes treated with 10(4) U/ml of M-CSF than from control cells. The priming effect of M-CSF on LPS-induced cytokine production was found to require 3-day preincubation, and reached a maximum at the concentration of 10(4) U/ml. M-CSF-treated cells responded to a 10 times lower concentration of LPS than control cells in terms of cytokine production. M-CSF was also shown by flowcytometric analysis to influence the expression of CD14, a receptor for LPS, which might render monocytes more sensitive to LPS. 相似文献
915.
Male rats were tested for their sexual preference behavior at either 37, 70, 90, or 150 days of age on three different occasions; while still sexually naive, after sexual experience with a receptive female, and while sexually aroused by having initiated copulation. These tests resulted in the following findings: a) 37-day-old sexually naive males showed a preference for other males and failed to show a preference for either sex after exposure to females; b) 70- and 90-day-old males showed a statistically significant preference for the female after acquiring sexual experience; c) 150-day-old animals showed a female-oriented preference only after being sexually aroused with two intromissions preceding the preference test, and d) none of the age groups tested showed a female-oriented preference without previous exposure to females. It was then concluded that a) female-oriented behavior requires sexual experience and b) the effects of experience varies with age. 相似文献
916.
Significant amounts of bismuth can be removed from magnesium-lead alloys by crystallization of the intermetallic compounds
Mg0. 6573Pb0. 3427 and Mg0.662Pb0.338in the Mg2Pb, magnesium plumbide phase field of the Pb-Mg-Bi system. The results of the previous studies have been used to develop a
process for debismuthizing lead using controlled conditions for the crystallization of magnesium plumbide from alloys containing
0.03 to 0.06 wt Pct bismuth and magnesium whose concentration is determined by the relationship wt Pct Mg = 2.9 + 20 x wt
Pct Bi. A flow diagram showing the sequence of operations is presented together with a material balance, which was established
from data obtained from individual experiments simulating the previously mentioned unit operations, with a final product containing
less than 0.0010 wt Pct Bi. The process also includes the recycling of magnesium recovered by vacuum distillation. Additional
procedures are included to extend the process to treat alloys containing up to 1.5 wt pct bismuth. 相似文献
917.
K Jaton-Ogay S Paris M Huerre M Quadroni R Falchetto G Togni JP Latgé M Monod 《Canadian Metallurgical Quarterly》1994,14(5):917-928
Aspergillus fumigatus secretes a serine alkaline protease (ALP) and a metalloprotease (MEP) when the fungus is cultivated in the presence of collagen as sole nitrogen and carbon source. The gene encoding ALP was isolated and characterized previously. We report here the cloning and the sequencing of the gene encoding MEP. Genomic and cDNA clones were isolated from A. fumigatus libraries using synthetic oligonucleotides as probes. Stretches of the deduced amino acid sequence were found to be in agreement with the N-terminal amino acid sequence of MEP and with internal peptide sequences. The amino acid sequence of the enzyme contains a putative active-site sequence HEYTH homologous to the active site of other bacterial and eukaryotic zinc metalloproteases. Sequence analysis reveals that MEP has a pre-proregion consisting of 245 amino acid residues preceding the 388 amino acid residues of the mature region (molecular mass of 42 kDa). An alp mep mutant, deficient in proteolytic activity at neutral pH in vitro, was constructed and tested for pathogenicity in a murine model. No difference in pathogenicity was observed between the wild-type strain and the alp mep double mutant, suggesting that ALP and MEP are not essential for the invasion of the lung tissues by A. fumigatus. 相似文献
918.
919.
Object and texture classification using higher order statistics 总被引:5,自引:0,他引:5
Tsatsanis M.K. Giannakis G.B. 《IEEE transactions on pattern analysis and machine intelligence》1992,14(7):733-750
The problem of the detection and classification of deterministic objects and random textures in a noisy scene is discussed. An energy detector is developed in the cumulant domain by exploiting the noise insensitivity of higher order statistics. An efficient implementation of this detector is described, using matched filtering. Its performance is analyzed using asymptotic distributions in a binary hypothesis-testing framework. The object and texture discriminant functions are minimum distance classifiers in the cumulant domain and can be efficiently implemented using a bank of matched filters. They are immune to additive Gaussian noise and insensitive to object shifts. Important extensions, which can handle object rotation and scaling, are also discussed. An alternative texture classifier is derived from a ML viewpoint and is statistically efficient at the expense of complexity. The application of these algorithms to the texture-modeling problem is indicated, and consistent parameter estimates are obtained 相似文献
920.
S. I. Glinchak Yu. A. Egorov R. R. Aliev E. D. Radchenko B. K. Nefedov N. A. Grigor'ev 《Chemistry and Technology of Fuels and Oils》1992,28(3):175-177
Translated from Khimiya i Tekhonologiy Topliv i Masel, No. 3, pp. 33–34, March, 1992. 相似文献