全文获取类型
收费全文 | 5142篇 |
免费 | 36篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 45篇 |
综合类 | 6篇 |
化学工业 | 529篇 |
金属工艺 | 36篇 |
机械仪表 | 60篇 |
建筑科学 | 140篇 |
矿业工程 | 4篇 |
能源动力 | 59篇 |
轻工业 | 215篇 |
水利工程 | 28篇 |
石油天然气 | 3篇 |
无线电 | 356篇 |
一般工业技术 | 468篇 |
冶金工业 | 2843篇 |
原子能技术 | 35篇 |
自动化技术 | 352篇 |
出版年
2021年 | 31篇 |
2019年 | 20篇 |
2018年 | 39篇 |
2017年 | 34篇 |
2016年 | 31篇 |
2015年 | 18篇 |
2014年 | 48篇 |
2013年 | 161篇 |
2012年 | 67篇 |
2011年 | 100篇 |
2010年 | 82篇 |
2009年 | 80篇 |
2008年 | 100篇 |
2007年 | 94篇 |
2006年 | 79篇 |
2005年 | 88篇 |
2004年 | 77篇 |
2003年 | 78篇 |
2002年 | 68篇 |
2001年 | 71篇 |
2000年 | 65篇 |
1999年 | 134篇 |
1998年 | 910篇 |
1997年 | 476篇 |
1996年 | 315篇 |
1995年 | 228篇 |
1994年 | 181篇 |
1993年 | 202篇 |
1992年 | 76篇 |
1991年 | 61篇 |
1990年 | 87篇 |
1989年 | 83篇 |
1988年 | 70篇 |
1987年 | 68篇 |
1986年 | 81篇 |
1985年 | 62篇 |
1984年 | 42篇 |
1983年 | 41篇 |
1982年 | 34篇 |
1981年 | 56篇 |
1980年 | 52篇 |
1979年 | 35篇 |
1978年 | 29篇 |
1977年 | 80篇 |
1976年 | 130篇 |
1975年 | 25篇 |
1974年 | 24篇 |
1973年 | 18篇 |
1972年 | 19篇 |
1971年 | 18篇 |
排序方式: 共有5179条查询结果,搜索用时 15 毫秒
61.
The paper presents a case study of the development of an expert decision support system which uses simple heuristic methods for fast determination of routes for simultaneous signals in a transmission network of limited capacity. It illustrates how heuristic solutions can be embodied in a model-based DSS and how the standard decision support literature, although intuitively appealing, provides little practical assistance in system construction or classification 相似文献
62.
SR Hall 《Canadian Metallurgical Quarterly》1996,21(3):225-229
An asymmetric triazine derivative, HOE 092 V,2-[3,5-alpha-dichloro-4-(4-methyl-sulfonylphenoxy)-phenyl]- 1-methyl-hexahydro-1,2,4-triazine-3,5-dion, was tested in vivo against Glugea anomala parasitizing the connective tissue of sticklebacks (Gasterosteus aculeatus). Naturally infected sticklebacks were incubated in 10-1 plastic aquaria in water containing 0, 2.5, 5, and 10 micrograms HOE 092 V/ml for 2, 3, and 4 h at 22 degrees C. As seen at the ultrastructural level, the drug caused severe damage to all developmental stages of G. anomala except the mature spores. Starting with a dose of 2.5 micrograms/ml, the drug caused significant damage on uni- and multinucleate meronts, sporogonial plasmodia, and sporoblasts. The damage mainly consisted in a decrease in the number of ribosomes, an enlargement of the smooth endoplasmic reticulum and a vacuolization of the cytoplasma. When treatment was done with 5 micrograms for 2 h, multinucleate meronts and sporogonial plasmodia were no longer detectable, and the sporoblasts and the prespore stages except the mature spores had shrunk. After incubation of the infected fish with 10 micrograms HOE 092 V/ml and 4 h exposure, uninucleate meronts were no longer detectable by means of transmission electron microscopy. In the sporoblast mother cells, vacuolization of the cytoplasma and lysis of the nuclei occurred. However, mature spores were not affected. It seems likely that HOE 092 V can be successfully applied in medicinal baths against Microsporidia in fish. The infected fish should be incubated in separate, aerated containers. 相似文献
63.
64.
R Pichlmayr A Weimann J Klempnauer KJ Oldhafer H Maschek G Tusch B Ringe 《Canadian Metallurgical Quarterly》1996,224(5):628-638
OBJECTIVES: The authors evaluated the experience and results of a single center in surgical treatment of proximal bile duct carcinoma. SUMMARY BACKGROUND DATA: Whenever feasible, surgery is the appropriate treatment in proximal bile duct carcinoma. To improve survival rates and with special regard to liver transplantation, the extent of surgical radicalness remains an open issue. PATIENTS AND METHODS: Retrospective analysis of 249 patients who underwent surgery for proximal bile duct carcinoma via the following procedures: resection (n = 125), liver transplantation (n = 25), and exploratory laparotomy (n = 99). Survival rates were calculated according to the Kaplan-Meier method, uni- and multivariate analysis of prognostic factors, and log rank test (p < 0.05). RESULTS: Survival rates after resection and liver transplantation are correlated with international Union Against Cancer (UICC) tumor stage (resection: overall 5-year, 27.1%; stage I and II, 41.9%; stage IV, 20.7%; liver transplantation: overall 5-year, 17.1%; stage I and II, 37.8%; stage IV, 5.8%). Significant univariate prognostic factors for survival after liver resection were lymph node involvement (N category), tumor stage, tumor-free margins, and vascular invasion; for transplantation, they were local tumor extent, N category, tumor stage, and infiltration of liver parenchyma. For resection and transplantation, a multivariate analysis showed prognostic significance of tumor stage and tumor-free margins. CONCLUSION: Resection remains the treatment of choice in proximal bile duct carcinoma. Whenever possible, decisions about resectability should be made during laparotomy. With regard to the observation of long-term survivors, liver transplantation still can be justified in selected patients with stage II carcinoma. It is unknown whether more radical procedures, such as liver transplantation combined with multivisceral resections, will lead to better outcome in advanced stages. With regard to palliation, surgical drainage of the biliary system performed as hepatojejunostomy can be recommended. 相似文献
65.
JF McCarthy DJ Cook MG Massad Y Sano KJ O''Malley NR Ratliff RW Stewart NG Smedira RC Starling JB Young PM McCarthy 《Canadian Metallurgical Quarterly》1998,14(2):197-200
28 isolates of canine parvovirus type-2 (CPV-2) were obtained from dogs with hemorrhagic gastroenteritis in Italy. The antigenic structure of CPV-2 isolates was characterized, using four discriminating monoclonal antibodies. In addition, four vaccinal strains were examined. Similar to reports from Australia and the United Kingdom, a much higher prevalence of CPV-2a (25/28 isolates) was observed than the other variant type, CPV-2b (3/28 isolates). DNA fragments (2.2 kbp) of representative strains of CPV-2, CPV-2a and CPV-2b were amplified by the polymerase chain reaction (PCR) and the products were digested by the restriction enzymes (RE) RsaI, HpaII, HindIII and PvuII. The RvaI enzyme allows the differentiation of CPV-2 from CPV-2a and CPV-2b. 相似文献
66.
BL Lum KJ Lane TW Synold A Goram SB Charnick BI Sikic 《Canadian Metallurgical Quarterly》1997,17(5):887-890
STUDY OBJECTIVE: To validate the utility of a previously reported 3-point limited sampling model (LSM) for determining etoposide area under the curve to infinity (AUC(infinity)). DESIGN: Secondary analysis of data from two clinical trials of etoposide. SETTING: University medical center clinical research center. PATIENTS: Thirty-four patients with different malignancies. INTERVENTIONS: Etoposide was administered as a 2-hour infusion to 34 patients. Serial plasma samples were drawn over 24 hours after the infusion and analyzed for etoposide by high-performance liquid chromatography. MEASUREMENTS AND MAIN RESULTS: The 3-point LSM AUC was compared with a 14-point actual AUC calculated by the linear trapezoidal rule. Actual and predicted AUC(infinity) by the LSM were highly correlated (r=0.97, p<0.0001). The LSM predictions had a mean absolute error of 10.9% (95% CI -14.1, -5.3) and a mean error of -9.7% (95% CI 6.9, 14.9). Nine patients with poor AUC(infinity) estimations by the LSM (error > 12%) tended to have abnormally low or high peak concentrations. CONCLUSION: Our findings suggest the development of more robust LSM using other techniques, such as pharmacostatistical models, that can accommodate a greater degree of pharmacokinetic variability. 相似文献
67.
LA Parada G Bardi M Hallén I H?gerstrand KG Tranberg F Mitelman B Johansson 《Canadian Metallurgical Quarterly》1997,21(11):1381-1386
Hepatoblastomas usually occur in children < 3 years of age, and only occasional adult cases have been described. To date, 20 cytogenetically abnormal childhood hepatoblastomas have been reported. Karyotypic investigations have shown that most hepatoblastomas are diploid or hyperdiploid, often displaying trisomies for chromosomes 2 and 20. We have cytogenetically investigated an adult hepatoblastoma for which no previous karyotypic data exist. A hypertriploid stemline with multiple numerical and structural chromosomal aberrations, including +2 and +20, was found. In addition, the tumor displayed extensive clonal evolution with 11 subclones. Although the tumor thus displayed some chromosomal abnormalities commonly observed in childhood tumors, providing further support for the importance of these abnormalities in the development of hepatoblastoma, the level of genomic complexity seen in the present case has never been described in childhood hepatoblastomas and may suggest a different etiology or pathogenesis. 相似文献
68.
KJ Guidera J Hooten W Weatherly M Highhouse A Castellvi JA Ogden L Pugh S Cook 《Canadian Metallurgical Quarterly》1993,18(4):427-431
Fifty-two posterior spinal fusions were performed for pediatric idiopathic, congenital, and neuromuscular scoliotic curves. Cotrel-Dubousset instrumentation was used in all patients. Nine had prior anterior spinal releases and fusions. The patterns were mixed, with a predominance of right thoracic curvatures. The average preoperative curve measured 60.6 degrees, with correction to 29. Seven patients required revision surgery, and 17 wore orthoses after operation. There were 17 complications in this group, including hook pullout, prominent hardware, infection, pseudarthrosis, and two cases of broken Cotrel-Dubousset instrumentation rods. Fatigue failure of this instrumentation, secondary to pseudarthrosis, has not been reported previously, and these two cases are presented in detail. The operative morbidity and difficulty were increased in the larger idiopathic curves and in neuromuscular and congenital scoliosis. Cotrel-Dubousset instrumentation is an overall excellent tool for the multiplanar correction of scoliosis and is amenable to revision surgery. 相似文献
69.
MG Beconi-Barker RE Hornish TJ Vidmar KJ Dame SA Brown 《Canadian Metallurgical Quarterly》1996,19(3):192-199
Coccidioides immitis, the primary pathogenic fungus that causes coccidioidomycosis, is most commonly found in the deserts of the southwestern United States and Central and South America. During the early 1990s, the incidence of coccidioidomycosis in California increased dramatically. Even though most infections are subclinical or self-limited, the outbreak is estimated to have cost more than $66 million in direct medical expenses and time lost from work in Kern County, California, alone. In addition to the financial loss, this pathogen causes serious and life-threatening disseminated infections, especially among the immunosuppressed, including AIDS patients. This article discusses factors that may be responsible for the increased incidence of coccidioidomycosis (e.g., climatic and demographic changes and the clinical problems of coccidioidomycosis in the immunocompromised) and new approaches to therapy and prevention. 相似文献
70.
C. A. Hall L. E. De Carlo M. L. Wenner N. L. Troyani 《International journal for numerical methods in engineering》1993,36(21):3617-3627
The computational method for large deformation plasticity called differential equations on a manifold (DEM) has previously been shown to be effective for axisymmetric and plane strain sheet metal forming problems. The method has now been formulated for in-plane stretching problems, incorporated into a computer code, and applied to several problems. The code's performance is robust and accurate, as evidenced by a comparison with other published results. Incorporation of an automatic mesh generator significantly reduces data preparation time. 相似文献