全文获取类型
收费全文 | 1936篇 |
免费 | 3篇 |
专业分类
电工技术 | 1篇 |
综合类 | 4篇 |
化学工业 | 38篇 |
机械仪表 | 3篇 |
建筑科学 | 6篇 |
矿业工程 | 1篇 |
能源动力 | 42篇 |
轻工业 | 10篇 |
水利工程 | 1篇 |
石油天然气 | 5篇 |
无线电 | 12篇 |
一般工业技术 | 14篇 |
冶金工业 | 1785篇 |
原子能技术 | 1篇 |
自动化技术 | 16篇 |
出版年
2022年 | 1篇 |
2020年 | 4篇 |
2017年 | 2篇 |
2016年 | 1篇 |
2015年 | 2篇 |
2014年 | 4篇 |
2013年 | 11篇 |
2012年 | 1篇 |
2011年 | 2篇 |
2010年 | 4篇 |
2009年 | 3篇 |
2008年 | 3篇 |
2007年 | 5篇 |
2006年 | 4篇 |
2005年 | 4篇 |
2004年 | 6篇 |
2003年 | 6篇 |
2002年 | 3篇 |
2001年 | 4篇 |
2000年 | 2篇 |
1999年 | 65篇 |
1998年 | 625篇 |
1997年 | 318篇 |
1996年 | 179篇 |
1995年 | 100篇 |
1994年 | 94篇 |
1993年 | 113篇 |
1992年 | 19篇 |
1991年 | 22篇 |
1990年 | 28篇 |
1989年 | 32篇 |
1988年 | 22篇 |
1987年 | 15篇 |
1986年 | 26篇 |
1985年 | 15篇 |
1984年 | 2篇 |
1983年 | 7篇 |
1982年 | 7篇 |
1981年 | 20篇 |
1980年 | 17篇 |
1979年 | 4篇 |
1978年 | 9篇 |
1977年 | 39篇 |
1976年 | 78篇 |
1975年 | 4篇 |
1974年 | 2篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1970年 | 1篇 |
1963年 | 1篇 |
排序方式: 共有1939条查询结果,搜索用时 0 毫秒
91.
KJ Jones 《Canadian Metallurgical Quarterly》1996,23(3):463-476
As arthroscopy of the wrist moves into the second decade, the trend for more indications for both diagnostic and therapeutic procedures will continue. It is only a matter of time before arthroscopic fusions, soft-tissue repairs, and "ectomy" procedures of all kinds become more commonplace. Whereas the advantages of the early therapeutic techniques in preserving soft-tissue structures and shortening recovery are now obvious, we will have to wait and see if the same holds true for more complicated bony and soft-tissue procedures in the next decade. 相似文献
92.
OBJECTIVE: To characterize the biochemical mechanisms of expression of the pyruvate dehydrogenase (PDH) E1alpha subunit exon 10 R302C missense mutation. BACKGROUND: Mutations in the X-linked E1alpha subunit gene are responsible for most cases of PDH deficiency, an important cause of neurodevelopmental defects and neurodegeneration with primary lactic acidemia. Although the disease shows extreme allelic heterogeneity, the R302C mutation has been defined in several unrelated cases. METHODS: Cell lines expressing selectively either the mutant or wild-type E1alpha alleles against identical genetic backgrounds were generated from the fibroblasts of a female heterozygous for the R302C mutation. Enzyme activity, mRNA, polypeptide expression, and turnover were studied in each. RESULTS: The residual PDH activity was below measurable levels in the cell line (B5) expressing only the mutant allele and normal in the wild-type polypeptide expressing (A10) cell line, confirming that the R302C mutation alone is sufficient to cause a severe PDH deficiency. The mutant polypeptide was less stable than the wild-type polypeptide, but the steady-state level of the mutant E1alpha protein was reduced only two- to threefold. CONCLUSIONS: The primary mechanism of expression of the R302C mutation must be limitation of catalytic efficiency. We speculate that catalysis may be inhibited in the mutant polypeptide because conformational changes are induced near serine 300, a residue that is particularly important as a regulatory phosphorylation site in the wild-type polypeptide. 相似文献
93.
94.
95.
T Murate K Yamashita H Ohashi Y Kagami K Tsushita T Kinoshita T Hotta H Saito S Yoshida KJ Mori 《Canadian Metallurgical Quarterly》1993,21(1):169-176
The erythroid-potentiating activity (EPA) of the tissue inhibitor of metalloproteinase-1 (TIMP-1) was re-examined using ELM-I-1-3, a mouse erythroleukemia cell line, which responded well to erythropoietin. Depletion of pre-existing TIMP-1 from fetal calf serum in culture medium using monoclonal antibody suppressed erythropoietin-induced differentiation as measured by the induction of hemoglobin, commitment assay and globin mRNAs. The removal of TIMP-1 also suppressed the proliferation of ELM-I-1-3 as measured by cell number and de novo DNA synthesis. These changes were reversed by the addition of purified TIMP-1 to the culture medium. Anti-TIMP-1 antibody also blocked both hexamethylene bisacetamide (HMBA)-induced erythroid differentiation and the proliferation of both ELM-I-1-3 and Friend erythroleukemia cells. Considering previous reports analyzing the chemical induction of Friend mouse erythroleukemia cell differentiation, our results suggest that erythropoietin- or HMBA-induced erythroid differentiation might also be coupled with cell proliferation. Our 3H thymidine-uptake experiment shows that TIMP-1 removal was also effective in the inhibition of cell growth of various other cell lines in addition to erythroleukemia cell lines. These results suggest that EPA action of TIMP-1 on erythroid leukemia cell lines is closely related to its activity to promote the cell growth of various cell lines and cells including erythroleukemia cell lines. 相似文献
96.
KJ Greenlund WH Giles NL Keenan JB Croft ML Casper D Matson-Koffman 《Canadian Metallurgical Quarterly》1998,7(9):1125-1133
We sought to examine the prevalence of self-reported multiple cardiovascular disease (CVD) risk factors (hypertension, high blood cholesterol, diabetes, overweight, and current smoking) among women in 1992 and 1995 in the United States using data from the Behavioral Risk Factor Surveillance System. In 1992, 37.5%, 34.4%, and 28.1% of women had zero, one, and two or more of the five risk factors, respectively. In 1995, the respective estimates were 35.5%, 34.3%, and 30%. In both years, the prevalence of two or more risk factors increased with age, decreased with educational level, was higher among black women (lowest among Hispanic women and women of other ethnic groups), and higher among women reporting cost as a barrier to healthcare. The percentage of women with two or more risk factors was higher in 1995 than in 1992 for 35 of 48 states, being statistically significant for 7 states. The percentage of women with at least two risk factors was not significantly lower in 1995 than in 1992 for any state. A higher percentage of women reported having multiple CVD risk factors in 1995 compared with 1992. A multifactorial approach to primary prevention and risk factor reduction should be encouraged to help reduce the prevalence and burden of CVD among women. 相似文献
97.
CR Deible P Petrosko PC Johnson EJ Beckman AJ Russell WR Wagner 《Canadian Metallurgical Quarterly》1998,19(20):1885-1893
For cardiovascular biomaterials, thrombosis, thromboembolism and vascular graft occlusion are believed to be precipitated by the adsorption of proteins containing adhesive ligands for platelets. Polyethylene-glycol-diisocyanate (PEG-diisocyanate, 3400 MW) may potentially react with protein amines to form molecular barriers on adsorbed proteins on biomaterials, thereby masking adhesive ligands and preventing acute surface thrombosis. To test this notion, PE, PTFE, and glass microconduits were pre-adsorbed with fibrinogen and treated with PEG-diisocyanate, non-reactive PEG-dihydroxyl, or remained untreated. Following perfusion of 111In-labeled platelets in whole human blood for 1 min (wall shear rate = 312 s(-1)), PEG-diisocyanate treated surfaces experienced 96% (PE), 97% (PTFE) and 94% (glass) less platelet deposition than untreated surfaces. Similar reductions were seen for PEG-diisocyanate versus PEG-dihydroxyl treatment. Low shear perfusions of plasma for 1 h prior to blood contact did not reduce the inhibitory effect of PEG-diisocyanate. Platelet adhesion onto collagen-coated glass coverslips and platelet deposition onto preclotted Dacron were also reduced by treatment with PEG-diisocyanate (93 and 91%, respectively). Protein-reactive PEG may thus have utility in forming molecular barriers on surface-associated proteins to inhibit acute thrombosis on cardiovascular biomaterials. 相似文献
98.
Extensive restriction site polymorphism at the human phenylalanine hydroxylase locus and application in prenatal diagnosis of phenylketonuria 总被引:4,自引:0,他引:4
AS Lidsky FD Ledley AG DiLella SC Kwok SP Daiger KJ Robson SL Woo 《Canadian Metallurgical Quarterly》1985,37(4):619-634
A total of 10 restriction site polymorphisms have been identified at the human phenylalanine hydroxylase locus using a full-length human phenylalanine hydroxylase cDNA clone as a hybridization probe to analyze human genomic DNA. These polymorphic patterns segregate in a Mendelian fashion and concordantly with the disease state in various PKU kindreds. The frequencies of the restriction site polymorphisms at the human phenylalanine hydroxylase locus among Caucasians are such that the observed heterozygosity in the population is 87.5%. Thus, most families with a history of classical phenylketonuria can take advantage of the genetic analysis for prenatal diagnosis and carrier detection of the hereditary disorder. 相似文献
99.
100.
Jing Zheng Scott P. Beckman Joe N. Gray Mufit Akinc 《Journal of the American Ceramic Society》2001,84(9):1961-1967
X-ray tomography has been used to investigate the density variations in SiC joints formed using polymer pastes. It has been demonstrated that X-ray tomography provides accurate bulk density measurements and volumetric density gradients. The results suggest that the magnitude of the applied pressure after green state joining and the amount of polymer (polycarbosilane, PCS) in the joining pastes influence the green density of the joints. All joints are prepared and applied in air atmosphere and at room temperature. The green densities of the joints increase from 54% to 66% of theoretical with the increase of the applied pressure from ambient to 138 MPa. Highest joint density without applied pressure is achieved using paste containing 50 vol% PCS. Furthermore, allylhydridopopolycarbosilane- (AHPCS-) containing pastes resulted in higher densities at the joint–matrix interface, indicating infiltration of polymer into the matrix. 相似文献