全文获取类型
收费全文 | 2731篇 |
免费 | 12篇 |
国内免费 | 1篇 |
专业分类
化学工业 | 75篇 |
金属工艺 | 21篇 |
机械仪表 | 14篇 |
建筑科学 | 17篇 |
矿业工程 | 6篇 |
能源动力 | 3篇 |
轻工业 | 68篇 |
水利工程 | 7篇 |
石油天然气 | 19篇 |
无线电 | 21篇 |
一般工业技术 | 61篇 |
冶金工业 | 2414篇 |
原子能技术 | 10篇 |
自动化技术 | 8篇 |
出版年
2021年 | 8篇 |
2020年 | 6篇 |
2019年 | 7篇 |
2018年 | 7篇 |
2017年 | 10篇 |
2016年 | 5篇 |
2015年 | 5篇 |
2014年 | 6篇 |
2013年 | 17篇 |
2012年 | 7篇 |
2011年 | 8篇 |
2010年 | 15篇 |
2009年 | 6篇 |
2008年 | 5篇 |
2007年 | 8篇 |
2006年 | 8篇 |
2005年 | 13篇 |
2004年 | 5篇 |
2003年 | 9篇 |
2001年 | 4篇 |
2000年 | 5篇 |
1999年 | 72篇 |
1998年 | 727篇 |
1997年 | 399篇 |
1996年 | 282篇 |
1995年 | 174篇 |
1994年 | 117篇 |
1993年 | 160篇 |
1992年 | 21篇 |
1991年 | 22篇 |
1990年 | 39篇 |
1989年 | 35篇 |
1988年 | 34篇 |
1987年 | 17篇 |
1986年 | 24篇 |
1985年 | 24篇 |
1984年 | 7篇 |
1983年 | 5篇 |
1982年 | 17篇 |
1981年 | 23篇 |
1980年 | 31篇 |
1979年 | 7篇 |
1978年 | 19篇 |
1977年 | 84篇 |
1976年 | 190篇 |
1975年 | 10篇 |
1974年 | 6篇 |
1972年 | 4篇 |
1969年 | 3篇 |
1965年 | 3篇 |
排序方式: 共有2744条查询结果,搜索用时 15 毫秒
971.
TB Whitaker MW Trucksess AS Johansson FG Giesbrecht WM Hagler DT Bowman 《Canadian Metallurgical Quarterly》1998,81(6):1162-1168
Variances associated with sampling, sample preparation, and analytical steps of a test procedure that measures fumonisin in shelled corn were estimated. The variance associated with each step of the test procedure increases with fumonisin concentration. Functional relationships between variance and fumonisin concentration were estimated by regression analysis. For each variance component, functional relationships were independent of fumonisin type (total, B1, B2, and B3 fumonisins). At 2 ppm, coefficients of variation associated with sampling (1.1 kg sample), sample preparation (Romer mill and 25 g subsample), and analysis are 16.6, 9.1, and 9.7%, respectively. The coefficient of variation associated with the total fumonisin test procedure was 45% and is about the same order of magnitude as that for measuring aflatoxin in shelled corn with a similar test procedure. 相似文献
972.
973.
Hyaline cartilage was found on microscopy of sections of the extrahepatic biliary tree in two infants with extrahepatic biliary atresia (EHBA). Respiratory epithelium was not present, and the cartilage did not seem to block the bile duct lumen. Hyperbilirubinemia was manifest in one infant on the second postnatal day, but clinical courses were otherwise unremarkable. In neither infant was the ductal plate malformation found on light microscopy of liver biopsy specimens, and in neither infant was visceral topography abnormal. Hyaline cartilage at the porta hepatis appears to be a novel finding in EHBA. Its significance remains to be defined. 相似文献
974.
975.
J Koulack VC McAlister CA Giacomantonio H Bitter-Suermann AS MacDonald TD Lee 《Canadian Metallurgical Quarterly》1995,16(2):110-113
Chronic rejection is the most common cause of late graft failure after solid organ transplantation. A model of chronic rejection, the rat aortic allograft, has histologic features that parallel those in the vessels of human transplanted organs. However, the molecular tools required to dissect the immunology of chronic rejection are unavailable in the rat. We developed aortic transplantation in the mouse as a new model of chronic rejection. This will allow the use of the diversity of recombinant cytokines and monoclonal antibodies available for the mouse and its well-defined genetics to investigate chronic rejection in greater detail. We describe the perioperative care and surgical technique for the model in which a 1 cm segment of donor thoracic aorta was used to replace a section of recipient abdominal aorta below the renal arteries and above the aortic bifurcation. Mortality rates were initially high (70%) due to thrombosis and shock. Changes in technique and operator facility resulted in a high rate of success (75%). After 192 operations, the current success rate is > 80%. Mice free from complications at 12 hrs postop had indefinite survival, and after 2 months the typical vascular lesion of chronic rejection was present. This new model of chronic rejection will be a valuable tool to study the molecular immunology and genetics of chronic rejection. 相似文献
976.
977.
In the presence of amine-containing sulfhydryl compounds, binding of heat-transformed cytosolic rat liver glucocorticoid receptor complex (GRC) to double-stranded calf thymus DNA-coated cellulose and to rat liver chromatin was enhanced up to 10-fold. These observations were made under conditions when a maximum of 8% of the total GRC bound to DNA in the absence of test compound. Compounds which did not contain both a sulfhydryl and amine group were inactive. Phosphorothioate derivatives of the active sulfhydryl compounds were also inactive. However, pretreatment of the phosphorothioate compounds with alkaline phosphatase restored activity. Upon centrifugation at 8800g, amine-containing disulfide compounds at millimolar concentrations caused considerable sedimentation of the GRC in the absence of DNA-coated cellulose or chromatin and no apparent increase in GRC binding to DNA or chromatin. Amine-containing disulfide compounds at micromolar concentrations did not cause heavy sedimentation of the GRC and enhanced binding of the GRC to DNA-coated cellulose up to 9.5-fold. Thus, diaminosulfhydryl compounds and the disulfide 1,18-diamino-6,13-diaza-9,10-dithiaoctadecane (WR 149,024) possess both the ability to restore and preserve the steroid binding capacity of the glucocorticoid receptor and to enhance binding of the GRC to DNA and chromatin. 相似文献
978.
979.
CG Kissel M McQuaid DR Lucas AS Sundareson RS Klimecki 《Canadian Metallurgical Quarterly》1995,85(6):301-305
Bizarre parosteal osteochondromatous proliferation of bone is a rare, benign bone tumor. The authors discuss two cases involving the bones of the feet, and review clinical, radiographic, and histopathologic characteristics. Awareness of this lesion is essential as bizarre parosteal osteochondromatous proliferation of bone can be mistaken for a malignancy. 相似文献
980.
Integrins were cross-linked to their extracellular matrix ligands using non-penetrating chemical cross-linkers. This procedure did not disturb the distribution of integrin in the adhesion structure and adhesion plaque integrin staining remained even when the cultures were extracted with ionic detergents. 80-90% of the beta 1 integrin in the cross-linked culture was extracted with RIPA buffer and the remaining 10-20% was recovered following reversal of the cross-linking. This separated two distinct integrin pools, one which can be cross-linked to substrate bound extracellular matrix and one which is not. The specificity of this procedure for cross-linking of integrins involved in substrate adhesion was demonstrated using NIH 3T3 cells which express both alpha 5 beta 1 and alpha 6 beta 1 integrins. alpha 6 was cross-linked only in cells plated on laminin whereas alpha 5 was cross-linked when fibronectin was present. Using antisera directed to the cytoplasmic domains of either alpha 5 or beta 1 integrin, it was demonstrated that these domains can be blocked in the intact cell but the blocking can be removed using ionic detergent extraction after chemical cross-linking. The extracellular matrix associated with the substrate surface but not that associated with the media exposed surface is both cross-linked and retained on the plastic dish following cross-linking. 相似文献