全文获取类型
收费全文 | 2672篇 |
免费 | 14篇 |
国内免费 | 8篇 |
专业分类
电工技术 | 2篇 |
化学工业 | 78篇 |
金属工艺 | 10篇 |
机械仪表 | 4篇 |
建筑科学 | 3篇 |
矿业工程 | 1篇 |
能源动力 | 15篇 |
轻工业 | 7篇 |
石油天然气 | 10篇 |
武器工业 | 5篇 |
无线电 | 17篇 |
一般工业技术 | 59篇 |
冶金工业 | 2469篇 |
自动化技术 | 14篇 |
出版年
2024年 | 1篇 |
2023年 | 1篇 |
2022年 | 3篇 |
2021年 | 7篇 |
2020年 | 4篇 |
2019年 | 10篇 |
2018年 | 11篇 |
2017年 | 13篇 |
2016年 | 15篇 |
2015年 | 7篇 |
2014年 | 12篇 |
2013年 | 24篇 |
2012年 | 16篇 |
2011年 | 21篇 |
2010年 | 7篇 |
2009年 | 9篇 |
2008年 | 13篇 |
2007年 | 14篇 |
2006年 | 17篇 |
2005年 | 8篇 |
2004年 | 3篇 |
2003年 | 8篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1999年 | 78篇 |
1998年 | 810篇 |
1997年 | 408篇 |
1996年 | 288篇 |
1995年 | 159篇 |
1994年 | 122篇 |
1993年 | 175篇 |
1992年 | 30篇 |
1991年 | 25篇 |
1990年 | 29篇 |
1989年 | 20篇 |
1988年 | 30篇 |
1987年 | 29篇 |
1986年 | 22篇 |
1985年 | 25篇 |
1983年 | 1篇 |
1982年 | 12篇 |
1981年 | 10篇 |
1980年 | 26篇 |
1978年 | 4篇 |
1977年 | 52篇 |
1976年 | 108篇 |
1974年 | 1篇 |
1955年 | 3篇 |
排序方式: 共有2694条查询结果,搜索用时 62 毫秒
991.
A new technique of unipolar laparoscopic coagulation is particularly useful for the treatment of pelvic or abdominal bleeding during laparoscopic procedures. Blood present at the coagulation site is blown clear with a stream of argon gas prior to tissue coagulation. Of particular importance is the virtual absence of smoke, and because the procedure involves a nontouch technique, eschar is not removed inadvertently. The speed of tissue coagulation is faster than that of conventional bipolar and unipolar techniques. 相似文献
992.
JS Mattson SJ Gallagher MH Jabro LL McLey 《Canadian Metallurgical Quarterly》1998,19(9):923-6, 928, 930 passim; quiz 938
Dental practitioners need to be aware of the complications that can arise in the management and treatment of patients with diabetes mellitus. Patients with diabetes, and patients with a family history of diabetes, are at-risk dental patients. They are more likely to develop periodontal disease, and the periodontitis is more likely to be severe. Diabetes influences the progression and severity of periodontitis through changes in the small blood vessels, decreased collagen formation, and impairment of the host's defense mechanisms. Furthermore, complications associated with diabetes, such as impaired wound healing, can affect the patient's response to periodontal therapies like guided tissue regeneration (GTR). The case report in this article discusses the postsurgical complications that occurred during GTR treatment of a patient with non-insulin-dependent diabetes. The diabetic's susceptibility to periodontal disease and impaired wound healing can affect the progression of the disease and its treatment. Dental patients with diabetes require close supervision and frequent monitoring of their medical and dental health by the dental clinician. 相似文献
993.
LJ McCormack JI Semple MH Stickland JH Barrett PJ Grant 《Canadian Metallurgical Quarterly》1998,92(5):199-206
An insertion/deletion (4G/5G) polymorphism in what has been shown to be an enhancer/repressor binding site in the promoter region of the PAI-1 gene has been related to plasma PAI-1 activity. Transfection studies demonstrated increased interleukin-1 stimulated PAI-1 synthesis in cells containing the 4G sequence. To study this response in endothelial cells, first passage HUVEC from 26 umbilical cords were stimulated with interleukin-1 and tumor necrosis factor-alpha. PAI-1 antigen was measured in 24-hour conditioned medium and allele-specific PCR utilized to determine genotype at the 4G/5G locus. Analysis of covariance was used to determine whether the effect of a variable time in culture was masking a difference between genotypes. A trend towards higher PAI-1 levels with increasing time in culture was observed. The geometric mean (95% confidence interval) of the basal rate of PAI-1 release was, 4G/4G 9.7 (7.0, 13.5) ng/24 hours (n=11), 4G/5G 9.5 (6.5, 13.9) ng/24 hours (n=9), and 5G/5G 10.9 (7.8, 15.1) ng/24 hours (n=6). In cells of the same cultures, the interleukin-1 stimulated levels were 25.9 (23.1, 29.1), 27.2 (23.6, 31.3), and 23.1 (19.5, 27.3) ng/24 hours, respectively, corresponding to ratios of stimulated to basal levels of 2.68, 2.87, and 2.12. After adjustment for time in culture the basal PAI-1 release was 4G/4G 10.7, 4G/5G 9.1, and 5G/5G 9.7 ng/24 hours. For interleukin-1 stimulated release the adjusted levels were 26.3, 27.0, and 22.7 ng/24 hours, respectively. Adjusted levels in 4G/4G genotype cells were non-significantly greater than those in cells of 5G/5G genotype by a factor of 1.16 (0.95, 4.08). This study did not demonstrate a significant difference in basal or cytokine stimulated PAI-1 release from cells of different PAI-1 promoter (4G/5G) genotypes but does not exclude increased interleukin-1 stimulated PAI-1 release in the 4G/4G compared with the 5G/5G genotype. 相似文献
994.
RP Du Q Wang YP Yang AB Schryvers P Chong MH Klein SM Loosmore 《Canadian Metallurgical Quarterly》1998,66(8):3656-3665
The lactoferrin receptor genes from two strains of Moraxella catarrhalis have been cloned and sequenced. The lfr genes are arranged as lbpB followed by lbpA, a gene arrangement found in lactoferrin and transferrin receptor operons from several bacterial species. In addition, a third open reading frame, orf3, is located one nucleotide downstream of lbpA. The deduced lactoferrin binding protein A (LbpA) sequences from the two strains were found to be 99% identical, the LbpB sequences were 92% identical, and the ORF3 proteins were 98% identical. The lbpB gene was PCR amplified and sequenced from a third strain of M. catarrhalis, and the encoded protein was found to be 77% identical and 84% similar to the other LbpB proteins. Recombinant LbpA and LbpB proteins were expressed from Escherichia coli, and antisera raised to the purified proteins were used to assess antigenic conservation in a panel of M. catarrhalis strains. The recombinant proteins were tested for the ability to bind human lactoferrin following gel electrophoresis and electroblotting, and rLbpB, but not rLbpA, was found to bind lactoferrin. Bactericidal antibody activity was measured, and while the anti-rLbpA antiserum was not bactericidal, the anti-rLbpB antisera were found to be weakly bactericidal. Thus, LbpB may have potential as a vaccine candidate. 相似文献
995.
Quantitative Risk Assessment (QRA) is a methodology used to organize and analyze scientific information to estimate the probability and severity of an adverse event. Applied to microbial food safety, the methodology can also help to identify those stages in the manufacture, distribution, handling, and consumption of foods that contribute to an increased risk of foodborne illness, and help focus resources and efforts to most effectively reduce the risk of foodborne pathogens. The term Process Risk Model (PRM) is introduced in this paper to describe the integration and application of QRA methodology with scenario analysis and predictive microbiology to provide an objective assessment of the hygienic characteristics of a manufacturing process. The methodology was applied to model the human health risk associated with Escherichia coli O157:H7 in ground beef hamburgers. The PRM incorporated two mathematical submodels; the first was intended to described the behaviour of the pathogen from the production of the food through processing, handling, and consumption to predict human exposure. The exposure estimate was then used as input to a dose-response model to estimate the health risk associated with consuming food from the process. Monte Carlo simulation was used to assess the effect of the uncertainty and variability in the model parameters on the predicted human health risk. The model predicted a probability of Hemolytic Uremic Syndrome of 3.7 x 10(-6) and a probability of mortality of 1.9 x 10(-7) per meal for the very young. These estimates are likely high for all hamburger meals, but may be reasonable for the home-prepared hamburgers described by this model. The efficacy of three risk mitigation strategies were evaluated by modifying the values of the predictive factors and comparing the new predicted risk. The average probability of illness was predicted to be reduced by 80% under a hypothetical mitigation strategy directed at reducing microbial growth during retail storage through a reduction in storage temperature. This strategy was predicted to be more effective than a hypothetical intervention which estimated a plausible reduction in the concentration of E. coli O157:H7 in the feces of cattle shedding the pathogen and one aimed at convincing consumers to cook hamburgers more thoroughly. The conclusions of this approach are only accurate to the extent that the model accurately represents the process. Currently, uncertainty and ignorance about the hygienic effects of the individual operations during production, processing, and handling limit the applicability of a PRM to specify HACCP criteria in a quantitative manner. However, with continuous improvement through stimulated research, a PRM should encompass all available information about the process, food, and pathogen and should be the most appropriate decision-support tool since it represents current knowledge. 相似文献
996.
VP Khatri TA Fehniger RA Baiocchi F Yu MH Shah DS Schiller M Gould RT Gazzinelli ZP Bernstein MA Caligiuri 《Canadian Metallurgical Quarterly》1998,101(6):1373-1378
To investigate the coordinated occurrence of loss of heterozygosity (LOH) at the BRCA1 locus and microsatellite instability (MI) in sporadic breast carcinomas, 56 tumors were analysed for both genetic alterations. The comparison of clinicopathological features with the obtained data revealed that LOH at the BRCA1 locus was significantly correlated with features specific for familial BRCA1 tumors and with absence of hormone receptors. No correlation was found between LOH and MI. These results suggest that sporadic and familial breast tumors, where BRCA1 is altered, could display similar clinicopathological features and that LOH and MI are distinct genetic events in sporadic breast carcinogenesis. 相似文献
997.
On-line in vivo microdialysis was used to determine the effects of a 16-min handling period on release of dopamine (DA) in the nucleus accumbens and of DA and noradrenaline (NA) in the medial prefrontal cortex of awake, freely moving rats. DA and NA were determined in one HPLC run. Handling resulted in an immediate and strong increase of both catecholamines in the prefrontal cortex. Maximal values for DA were 295%, and for NA 225%, of controls. DA in the nucleus accumbens was also increased (to 135% of controls) but only after a short delay. Local inhibition of ionotropic glutamate receptors by continuous reversed dialysis of the drugs 6-cyano-7-nitroquinoxaline, D-2-amino-5-phosphonopentanoic acid, or dizocilpine did not significantly affect handling-induced increases in cortical DA and NA release. Neither did the agonist of metabotropic glutamate receptors, trans-(1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid (ACPD), or the GABA-B agonist baclofen. Reversed dialysis of dizocilpine in the nucleus accumbens was equally ineffective, but ACPD inhibited the increase in DA release in this area. Stimulation of metabotropic glutamate receptors in the nucleus accumbens was previously reported to inhibit activation of DA release in that area after stimulation of glutamatergic or dopaminergic afferents. It is concluded that metabotropic receptors in the nucleus accumbens are important for the control of activation of DA release in the accumbens by physiological stimuli but that a similar mechanism is lacking in the prefrontal cortex. 相似文献
998.
G Hansen L Nielsen E Kluger MH Thysen H Emmertsen K Steng?rd-Pedersen EC Lund B Unger PW Andersen 《Canadian Metallurgical Quarterly》1998,160(21):3074-3078
This study deals with the nutritional status of Danish rheumatoid arthritis (RA) patients and addresses the question whether or not RA can be directly influenced by dietary manipulation. In a prospective, single-blinded study of six months' duration, 109 patients with active RA were randomly assigned to treatment with or without a specialized diet. The energy consumption was adjusted to normal standards for body-weight and the intake of fish and antioxidants was increased. A daily food diary was completed by the patients, and the total intake of 47 different food-elements was calculated. Nutritional status together with disease activity parameters were recorded. At baseline, the Danish RA-patients had neglected food habits with a significant reduction in intake of total energy, of D-vitamin and of E-vitamin. A very low intake of n-3 fatty acids was also found. During the study, 28 of the 109 patients dropped out, introducing a confounding effect on the overall result. In the remaining 81, those following the diet demonstrated a significant improvement in the duration of morning stiffness, the number of swollen joints, the pain status and reduced the cost of medicine, while doctors' global assessment, laboratory data, X-ray and the daily activities were unaltered. In conclusion, dietary analysis and appropriate, corrective advice should be offered to Danish RA patients. 相似文献
999.
A study was made to evaluate the use of a marker organism for assessing whether hygienic slaughter practices were being followed at red meat abattoirs. The organism, a nonpathogenic strain of Escherichia coli K12 that was resistant to nalidixic acid, was detected and counted on a highly specific isolation medium. With beef carcases, the practice of bagging the excised anus reduced, but did not prevent the spread of the organism from an inoculum applied in the anal region before the hide was removed. The carcases of sheep that were processed at a low-throughput abattoir, were contaminated with the marker after the fleece had been inoculated at a single site. The contamination was significantly reduced (P<0.001) when the operative responsible for flaying had cleaned his hands, arms and apron before and during the handling of each carcase, and used a knife which was freshly pasteurised on several occasions. However, the subsequent washing of carcases had little or no effect on the levels of the marker organism. It was concluded that the marker may be of value in assessing hygiene control, improving present practices, and training abattoir staff. 相似文献
1000.
Polymorphism in transporter associated with antigen processing (TAP)1 gene has been observed in African American Graves' disease patients. Single strand conformational polymorphism has been used to identify variation for the locus. First-strand cDNA was generated from cell lines obtained by Epstein-Barr virus immortalization. Four variant alleles for TAP1 have been observed and the products have been sequenced to compare with the location of observed with SSCP position patterns. Variants were detected and compared with substitutions within TAP1 polypeptide which includes changing valine to leucine and three (3) silent substitutions for glycine, glutamic acid and alanine. 相似文献