全文获取类型
收费全文 | 2951篇 |
免费 | 2篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 3篇 |
综合类 | 1篇 |
化学工业 | 32篇 |
金属工艺 | 3篇 |
机械仪表 | 4篇 |
建筑科学 | 13篇 |
轻工业 | 51篇 |
水利工程 | 2篇 |
石油天然气 | 3篇 |
无线电 | 14篇 |
一般工业技术 | 59篇 |
冶金工业 | 2730篇 |
原子能技术 | 4篇 |
自动化技术 | 35篇 |
出版年
2022年 | 3篇 |
2020年 | 3篇 |
2019年 | 6篇 |
2018年 | 5篇 |
2016年 | 6篇 |
2014年 | 4篇 |
2013年 | 26篇 |
2012年 | 7篇 |
2011年 | 11篇 |
2010年 | 10篇 |
2009年 | 9篇 |
2008年 | 4篇 |
2007年 | 5篇 |
2006年 | 9篇 |
2005年 | 10篇 |
2004年 | 11篇 |
2003年 | 8篇 |
2002年 | 5篇 |
2001年 | 5篇 |
2000年 | 8篇 |
1999年 | 83篇 |
1998年 | 828篇 |
1997年 | 479篇 |
1996年 | 311篇 |
1995年 | 175篇 |
1994年 | 140篇 |
1993年 | 177篇 |
1992年 | 34篇 |
1991年 | 40篇 |
1990年 | 31篇 |
1989年 | 34篇 |
1988年 | 50篇 |
1987年 | 35篇 |
1986年 | 33篇 |
1985年 | 30篇 |
1983年 | 5篇 |
1982年 | 18篇 |
1981年 | 18篇 |
1980年 | 24篇 |
1979年 | 5篇 |
1978年 | 8篇 |
1977年 | 51篇 |
1976年 | 157篇 |
1975年 | 10篇 |
1973年 | 3篇 |
1967年 | 2篇 |
1966年 | 2篇 |
1957年 | 2篇 |
1955年 | 3篇 |
1928年 | 2篇 |
排序方式: 共有2954条查询结果,搜索用时 15 毫秒
991.
AL McDonald RJ Fielder GE Diggle DR Tennant CE Fisher 《Canadian Metallurgical Quarterly》1996,15(9):739-746
A pragmatic possible approach to the prioritization of chemical carcinogens occurring as food contaminants is described, based on the carcinogenic risk to the population. This should be of value in ensuring that resources for assessment and management of carcinogens in food are directed to the most important areas with regard to carcinogenic risk to the population. Key components of this approach are an assessment of the carcinogenic hazard to humans combined with estimations of intakes per person and of the proportion of the population exposed. These are used to derive an index referred to as the Population Carcinogenic Index. Concerning the hazard assessment expert judgement is used to place the chemical in one of five categories. The highest category is for chemical carcinogens that are believed to act by a genotoxic mechanism. It is recognised that such compounds may vary enormously with respect to their potency and various approaches to ranking carcinogens on the basis of potency are reviewed. The approach adopted is to subdivide the genotoxic carcinogens category into high, medium and low potency based on the TD50 value. Methods of estimating intakes and exposed populations are considered and an approach which groups these into broad categories is developed. The hazard and exposure assessments are then combined to derive the Population Carcinogenicity Index. 相似文献
992.
O Takamiya G Kemball-Cook DM Martin DN Cooper A von Felten E Meili I Hann DR Prangnell H Lumley EG Tuddenham 《Canadian Metallurgical Quarterly》1993,2(9):1355-1359
Five unrelated subjects with dysfunctional coagulation factor VII (FVII) were studied in order to identify missense mutations affecting function. Exons 2 to 8 and the intron-exon junctions of their FVII genes were amplified from peripheral white blood cell DNA by PCR and screened by SSCP analysis. DNA fragments showing aberrant mobility were sequenced. The following mutations were identified: in case 1 (FVII:C < 1%, FVII:Ag 18%) a heterozygous A to G transition at nucleotide 8915 in exon 6 results in the amino acid substitution Lys-137 to Glu near the C-terminus of the FVIIa light chain; in case 2 (FVII:C 7%, FVII:Ag 47%) a heterozygous A to G transition at nucleotide 7834 in exon 5 results in the substitution of Gln-100 by Arg in the second EGF-like domain; in case 3 (FVII:C 20%, FVII:Ag 76%) a homozygous G to A transition at nucleotide position 6055 in exon 4 was detected resulting in substitution of Arg-79 by Gln in the first EGF-like domain; in case 5 (FVII:C 10%, FVII:Ag 52%) a heterozygous C to T transition at nucleotide position 6054 in exon 4 also results in the substitution of Arg79, but in this case it is replaced by Trp; case 4 (FVII:C < 1%, FVII:Ag 100%) was homozygous for a previously reported mutation (G to A) at nucleotide position 10715 in exon 8, substituting Gln for Arg at position 304 in the protease domain. Cases 1, 2 and 5 evidently have additional undetected mutations. 相似文献
993.
It has been reported that alteration of deletion of critical residues within one of the two homologous protein tyrosine phosphatase (PTPase)-like domains of CD45 completely abolishes all activity, suggesting that only the more N-terminal domain is catalytically active. However, we now demonstrate, by two independent techniques, that the second (C-terminal) domain is also a viable phosphatase. Limited proteolysis by endoproteinase Lys-C or trypsin increased the phosphatase activity toward reduced, carboxymethylated, and maleylated lysozyme approximately 8-fold. A 50-kDa fragment, isolated by ion exchange chromatography, was found to be responsible for this activity. N-terminal sequencing revealed that this fragment includes less than half of the first phosphatase domain and most, if not all, of the second. In a second experiment, 109 residues, including the presumed catalytic region, were removed from domain I by site-directed mutagenesis. Expression of this construct in a mammalian cell line resulted in increased PTPase activity over nontransfected control cells. Isolation of the recombinant CD45 by immunoprecipitation and immunoaffinity chromatography revealed that it had phosphatase activity. Both of these experimental approaches demonstrate that the second conserved PTPase domain of CD45 is a functioning PTPase, but that external regulation may be required to express its activity in the context of the native molecule. 相似文献
994.
D Neumark-Sztainer M Story S French N Cassuto DR Jacobs MD Resnick 《Canadian Metallurgical Quarterly》1996,86(11):1599-1606
OBJECTIVES: This study compared prevalence rates of health-compromising behaviors among boys and girls from different ethnic backgrounds in early, middle, and late adolescence and compared co-occurrences of such behaviors across gender and ethnic groups. METHODS: The study population included 123 132 adolescents in grades 6, 9, and 12. Adolescents completed a classroom-administered statewide survey focusing on high-risk behaviors, including unhealthy weight loss, substance abuse, suicide risk, delinquency, and sexual activity. RESULTS: Prevalence rates of most health-compromising behaviors differed by gender, increased with age, and tended to be highest among American Indian youth and lowest among Asian Americans. Strong associations were found between substance abuse and delinquency across all ethnic groups. Substance abuse and delinquency were associated with suicide risk across most ethnic groups. Covariations with sexual activity and unhealthy weight loss behaviors showed more ethnic variation. CONCLUSIONS: Prevention interventions should take into account the tendency for health-compromising behaviors to co-occur and should be sensitive to demographic and socioeconomic differences in behavior patterns. 相似文献
995.
EK Rowinsky V Chaudhry AA Forastiere SE Sartorius DS Ettinger LB Grochow BG Lubejko DR Cornblath RC Donehower 《Canadian Metallurgical Quarterly》1993,11(10):2010-2020
PURPOSE: To determine the maximum-tolerated doses (MTD), the principal toxicities, and the pharmacologic behavior of high doses of Taxol (paclitaxel; Bristol-Myers Squibb, New York, NY) combined with cisplatin and granulocyte colony-stimulating factor (G-CSF). PATIENTS AND METHODS: Untreated and minimally pretreated solid-tumor patients received 24-hour infusions of Taxol on day 1 followed by cisplatin on day 2 and G-CSF, 5 micrograms/kg/d subcutaneously (SC), beginning on day 3. Treatment was repeated every 3 weeks. Starting doses of Taxol and cisplatin were 135 and 75 mg/m2, respectively. RESULTS: The development of a severe peripheral neuropathy and/or severe myalgias precluded the chronic administration of Taxol and cisplatin with G-CSF at doses greater than 250 mg/m2 and 75 mg/m2, respectively. At this dose, the mean Taxol steady-state plasma concentration (Css) exceeds concentrations capable of inducing pertinent antimicrotubule effects in vitro. The severity of the neuropathy was related to the cumulative dose of Taxol, the magnitude of the dose administered during each treatment, and the presence of a pre-existing medical disorder associated with peripheral neuropathy. A proximal myopathy of modest severity also was documented. Although severe neutropenia occurred frequently, especially at the MTD, it was rarely associated with fever (8% of courses), and absolute neutrophil counts (ANCs) less than 500/microL never persisted for more than 5 days. Responses were noted in non-small-cell lung cancer (NSCLC) and head and neck, breast, and esophageal cancers. CONCLUSION: Taxol and cisplatin doses of 250 mg/m2 and 75 mg/m2, respectively, can be administered repetitively with G-CSF to untreated and minimally pretreated patients. However, these doses are not recommended for patients with pre-existing neuropathies until additional experience in high-risk patients is obtained. Although this Taxol dose is nearly 85% higher than the dose that can be combined with cisplatin in the absence of G-CSF, this high-dose regimen should not be used outside the investigational setting until a dose-response relationship has been demonstrated for Taxol in randomized clinical trials. 相似文献
996.
M Makris FE Preston FR Rosendaal JC Underwood KM Rice DR Triger 《Canadian Metallurgical Quarterly》1996,94(4):746-752
Most haemophiliacs treated with non-virally-inactivated clotting factor concentrates have been infected with hepatitis C virus (HCV). We have studied the natural history of chronic HCV infection by following all 138 HCV-positive patients from our centre for periods of up to 28 years. As well as the clinical and biochemical characteristics, we studied 116 liver samples from 63 patients obtained at elective biopsy (n = 103) or autopsy (n = 13). 36 (26%) of the patients were HIV positive, and three were chronic carriers of hepatitis B. Evidence of previous exposure to hepatitis A and B was found in 37.2% and 48.1% respectively. Raised transaminase levels were found in 82.6% of patients. 11 of 15 patients with normal transaminases tested by PCR for HCV RNA were positive, indicating that most patients, even in this group, have chronic hepatitis C infection. Cirrhosis was diagnosed by liver histology in 19 patients, and nine patients developed liver failure. The incidence of cirrhosis rose rapidly 15 years after HCV infection to 15.6 per 1000 person-years. Multivariate analysis showed that HIV status, length of time since HCV infection and age at HCV infection were independently associated with both the development of cirrhosis and liver failure. Two patients developed hepatocellular carcinoma: one of these was exposed only to a single batch of FVIII concentrate 11 years earlier. Chronic hepatitis C is increasingly recognized as a major cause for morbidity and mortality in haemophiliacs, especially those who are HIV positive and who were infected at an older age. 相似文献
997.
998.
999.
LE Kazis DR Miller J Clark K Skinner A Lee W Rogers A Spiro S Payne G Fincke A Selim M Linzer 《Canadian Metallurgical Quarterly》1998,158(6):626-632
In a curative resection for advanced sigmoid or rectal cancer, an extensive dissection of the regional lymph nodes is generally required. This often necessitates the removal of the autonomic nerves around the inferior mesenteric artery. The present study was done in an attempt to clarify the influence of a neurectomy around the inferior mesenteric ganglion and plexus on the motility of the colon. In eight dogs, we resected the ganglion and plexus around the inferior mesenteric artery, together with an implantation of strain gauge force transducers in various parts of the colon, and 7-10 days later, colonic motility was examined. The percentage of contractile states and contractile forces increased at both the distal colon in fasting dogs, as well as at the middle colon in the late postprandial period. At the distal colon, contractile forces were noted in the early and late postprandial periods. These contractile abnormalities at the middle and distal colon may thus explain the frequent bowel movements or diarrhea often observed after extensive surgery in patients with sigmoid or rectal cancer. 相似文献
1000.