全文获取类型
收费全文 | 2422篇 |
免费 | 8篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 14篇 |
化学工业 | 133篇 |
金属工艺 | 29篇 |
机械仪表 | 30篇 |
建筑科学 | 61篇 |
矿业工程 | 1篇 |
能源动力 | 26篇 |
轻工业 | 131篇 |
水利工程 | 12篇 |
石油天然气 | 1篇 |
无线电 | 94篇 |
一般工业技术 | 214篇 |
冶金工业 | 1530篇 |
原子能技术 | 18篇 |
自动化技术 | 137篇 |
出版年
2021年 | 6篇 |
2018年 | 6篇 |
2016年 | 7篇 |
2015年 | 6篇 |
2014年 | 16篇 |
2013年 | 57篇 |
2012年 | 36篇 |
2011年 | 50篇 |
2010年 | 24篇 |
2009年 | 33篇 |
2008年 | 41篇 |
2007年 | 37篇 |
2006年 | 37篇 |
2005年 | 48篇 |
2004年 | 36篇 |
2003年 | 37篇 |
2002年 | 36篇 |
2001年 | 21篇 |
2000年 | 30篇 |
1999年 | 60篇 |
1998年 | 474篇 |
1997年 | 242篇 |
1996年 | 189篇 |
1995年 | 112篇 |
1994年 | 89篇 |
1993年 | 105篇 |
1992年 | 23篇 |
1991年 | 38篇 |
1990年 | 28篇 |
1989年 | 33篇 |
1988年 | 28篇 |
1987年 | 20篇 |
1986年 | 23篇 |
1985年 | 27篇 |
1984年 | 21篇 |
1983年 | 15篇 |
1982年 | 26篇 |
1981年 | 13篇 |
1980年 | 22篇 |
1979年 | 17篇 |
1978年 | 22篇 |
1977年 | 47篇 |
1976年 | 76篇 |
1975年 | 16篇 |
1974年 | 6篇 |
1973年 | 15篇 |
1972年 | 5篇 |
1971年 | 11篇 |
1970年 | 10篇 |
1965年 | 7篇 |
排序方式: 共有2431条查询结果,搜索用时 15 毫秒
91.
BR Moed BK Ahmad JG Craig GP Jacobson MJ Anders 《Canadian Metallurgical Quarterly》1998,80(4):537-546
Cells of the innate immune system secrete cytokines early in immune responses that guide maturing T helper (Th) cells along appropriate lineages. This study investigates the role of cytokine networks, bridging the innate and acquired immune systems, in the pathogenesis of an organ specific autoimmune disease. Experimental allergic encephalomyelitis (EAE), a demyelinating disease of the central nervous system, is widely used as an animal model for multiple sclerosis. We demonstrate that interleukin (IL)-12 is essential for the generation of the autoreactive Th1 cells that induce EAE, both in the presence and absence of interferon gamma. The disease-promoting effects of IL-12 are antagonized by IL-10 produced by an antigen nonspecific CD4+ T cell which, in turn, is regulated by the endogenous production of IL-12. This unique immunoregulatory circuit appears to play a critical role in controlling Th cell differentiation and provides a mechanism by which microbial triggers of the innate immune system can modulate autoimmune disease. 相似文献
92.
BR Hoar BB Chomel FJ Argazz Rodriguez PA Colley 《Canadian Metallurgical Quarterly》1998,212(11):1714-1720
PURPOSE: The purpose of this study was to develop an analytical method for the quantitative determination of the extent of neutralization of the carboxylic acid function in Carbopol 974P NF using Diffuse Reflectance Fourier Transform Infrared Spectroscopy (DRIFT) with Kubelka-Munk function analysis. METHODS: Carbopol 974P NF is a high molecular weight, chemically crosslinked polymer of acrylic acid, that has the C=O stretching band of the unionized carboxylic acid function at 1695 cm(-1). The quantitative determination of the extent of neutralization of the carboxylic acid function in Carbopol 974P NF is based upon the asymmetrical C=O stretching of the carboxylate anion at 1570 cm(-1) measured by DRIFT spectroscopy. RESULTS: To overcome spectral differences arising from sample preparation (powders, granules and tablets) and in an effort to increase the precision of the analytical method, the following approaches were used: (1) an internal standard, (2) first derivative of the spectrum to eliminate the effect of baseline drift and (3) the ratio of the first derivative of the C=O stretch of the carboxylate anion peak (1570 cm(-1)) in the neutralized Carbopol 974P NF to that of the peak of the internal standard (866 cm(-1)). The above data treatment techniques proved to be superior to the usual methods of peak height or peak area. The calibration curve of the ratio of the first derivative (1570 cm(-1)/866 cm(-1)) was a linear function of the mass of sodium carboxylate over the range from 0.0% to 100.0% neutralization of the carboxylic acid function in Carbopol 974P NF (Fig. 1a). No particle size or sample preparation effects were noted within the experimental error. CONCLUSIONS: DRIFT spectroscopy using the Kubelka-Munk function is a powerful tool for the routine determination of the extent of neutralization of the carboxylic acid function in Carbopol 974P NF in complex pharmaceutical formulations. 相似文献
93.
JM Mariner JB McMahon BR O'Keefe K Nagashima MR Boyd 《Canadian Metallurgical Quarterly》1998,248(3):841-845
Concentrations of the potent, HIV(human immunodeficiency virus) inactivating protein, cyanovirin-N (CV-N), which completely inhibit HIV-1 infectivity, do not block the binding of soluble CD4-receptor (sCD4) to HIV-1 lysates nor the attachment of intact HIV-1 virions to several target T-cell lines. Furthermore, in contrast to the known disassociative effects of sCD4 on viral envelope glycoproteins, treatment of HIVRF with high concentrations of CV-N results in complete viral inactivation but without apparent shedding of gp120 or other ultrastructural changes. These results are consistent with the view that the virucidal effects of CV-N result from interference with step(s) in the fusion process subsequent to the initial binding of the virus to target cells. 相似文献
94.
S Chen J Sawicka L Prentice JF Sanders H Tanaka V Petersen C Betterle M Volpato S Roberts M Powell BR Smith J Furmaniak 《Canadian Metallurgical Quarterly》1998,83(8):2977-2986
A panel of five mouse monoclonal antibodies (MAbs) to human recombinant steroid 21-hydroxylase (21-OH) were produced, characterized, and used to study the interaction of 21-OH autoantibodies (AAbs) with different epitopes on human 21-OH. AAbs in patients with isolated autoimmune Addison's disease, autoimmune polyglandular syndromes types I and II, and 21-OH antibody-positive patients without overt Addison's disease (25 patients in total) were studied. Four MAbs were IgG1 subclass, one was IgG2a, and all had kappa light chains. The affinities of four of the antibodies were in the range 2.0 x 10(8) M(-1) to 7.0 x 10(8) M(-1), and the affinity of the other was 2.3 x 10(7) M(-1) 21-OH MAbs did not cross-react with 17alpha-hydroxylase (17alpha-OH)) or P450 side chain cleavage enzyme. Studies using a series of 21-OH fragments allowed the identification of short stretches of amino acids (AA) that were involved in forming the MAb binding sites. AA 391-405, defined as epitope region (ER) 1, were found to be important for binding of M21-OH1 and M21-OH2, AA 406-411 (ER2) were important for M21-OH3 and M21-OH4 binding, and AA 335-339 (ER3) for M21-OH5 binding. In addition, MAb Fab or F(ab')2 fragments were used to study 21-OH AAb epitopes in competition experiments. These investigations demonstrated that 21-OH AAbs recognize similar epitopes to the MAbs, with ER2 and ER3 being part of two distinct major epitopes, and ER 1 being part of a minor epitope. Mixtures of M21-OH antibody Fab or F(ab')2 fragments caused almost complete inhibition (80%-95%) of AAb binding in 24 out of 25 sera, and in the case of the remaining serum, the effect was marked but incomplete (67% inhibition). There were no major differences between the binding characteristics of AAbs from patients with different forms of autoimmune adrenal disease. All five 21-OH MAbs reacted with human adrenal tissue in an immunofluorescence test, but only M21-OH1 and M21-OH2 reacted with bovine adrenal tissue in these experiments. None of the MAbs reacted with human ovarian tissue in an immunofluorescence test. Overall, these studies indicate that 21-OH AAbs bind to at least three different epitopes in the C-terminal part of 21-OH, and two of these epitopes appear to be human 21-OH specific. 相似文献
95.
We reviewed the use of a low radiation portable fluoroscopy unit in 100 patients. The most common indication was closed reduction of distal radial fractures. Fracture and joint stability were assessed on the real-time monitor and stored on videotape. Static images were stored on thermographic paper. Fluoroscopically guided joint injections and localization of implants, foreign bodies and bone tumours were performed. Fluoroscopy is a useful adjunct to arthroscopic assisted fracture reduction and other arthroscopic procedures such as distal ulnar resection. These new generation units produce superior resolution images, are easy to manoeuvre and do not require a radiographer. 相似文献
96.
Ray Hunt 《Computer Communications》1984,7(6):283-288
The requirements of a highly reliable data transport mechanism are outlined, and a practical implementation of the CCITT/ISO standards within the airline is demonstrated. An understanding of the ISO Open Systems Interconnection architecture, as well as CCITT recommendations such as X.25 and X.75, is assumed. The selection of various X.25 subsets and how they meet the data communications needs of a variety of interconnection structures are then described. Finally, the paper reviews the current work being undertaken with respect to the higher layers of the ISO OSI architecture. 相似文献
97.
BR Berends F Van Knapen DA Mossel SA Burt JM Snijders 《Canadian Metallurgical Quarterly》1998,44(3):219-229
Cell-cell and cell-extracellular matrix interactions are fundamental processes involved in cell migration and tissue remodeling. Both the cyclic regeneration of the human endometrium during the menstrual cycle as well as the process of embryo implantation involve such dynamic interactions. It has become quite clear that integrin adhesion molecules expressed on the surface of cells play critical roles in the transmission of signals from the extracellular milieu to the cells. It is these signals that presumably regulate the behavior of these cells during major morphogenetic processes. In recent years, work in human endometrium and trophoblasts has uncovered both the regulated and constitutive expression of integrin subunits and their extracellular matrix ligands in these tissues. In addition, attempts have been made to correlate pathological states related to either infertility or abnormal pregnancy to the aberrant expression of several of these integrins. The purpose of the present review is to describe briefly our present state of knowledge of the expression of integrins in human endometrium and trophoblasts and provide the reader with the necessary background needed to understand, at the cellular and molecular levels, processes in reproduction such as embryo implantation. 相似文献
98.
BR Nelson DJ Fader M Gillard SR Baker TM Johnson 《Canadian Metallurgical Quarterly》1995,32(4):623-626
We describe our experience with two patients with xeroderma pigmentosum who underwent periodic trichloroacetic acid chemical peels. One also received a full-face dermabrasion. The effect of chemical peeling was more transient than dermabrasion but was associated with less morbidity. Both chemical peeling and dermabrasion provided a prophylactic effect against the development of skin malignancies; the latter had a more pronounced effect. 相似文献
99.
100.
Although sequences within the C terminus of apolipoprotein B (apoB) have been implicated in the formation of covalent lipoprotein(a) [Lp(a)] particles, sequences in apoB that mediate initial noncovalent interaction with apo(a) remain to be characterized. To address this question, we have used an affinity chromatography method in which 2 recombinant forms of apo(a) [r-apo(a); either a 17-kringle form (17K) or a derivative containing apo(a) kringle IV types 5-8] have been immobilized onto Sepharose beads. Conditioned media from rat hepatoma (McA-RH7777) cell lines stably expressing various carboxyl-terminally truncated forms of human apoB (ranging from full-length apoB to apoB15) were applied to the r-apo(a) affinity columns; the columns were subsequently washed and eluted with epsilon-aminocaproic acid (epsilon-ACA). Specific binding was quantified by Western blot analysis of column fractions. Of the apoB truncations examined, apoB94, apoB42, apoB37, and apoB29 exhibited complete specific binding to 17K r-apo(a). Only approximately 50% binding was observed for apoB18, whereas essentially no detectable binding was observed with apoB15. In all cases, similar results were obtained when the r-apo(a) kringle IV types 5-8-Sepharose column was used. Additionally, substitution of proline for epsilon-ACA as the eluent resulted in similar column profiles with either r-apo(a) affinity column. We also demonstrated that apoB48 present in chylomicrons bound completely to the 17K column in an epsilon-ACA-dependent manner. Taken together, these results represent the first demonstration that N-terminal sequences in apoB between amino acid residues 680 (apoB15) and 781 (apoB18) are essential for noncovalent association with apo(a) and that these sequences interact with domain(s) present within apo(a) kringle IV types 5-8. 相似文献