全文获取类型
收费全文 | 2754篇 |
免费 | 0篇 |
专业分类
化学工业 | 13篇 |
建筑科学 | 5篇 |
轻工业 | 26篇 |
石油天然气 | 2篇 |
无线电 | 3篇 |
一般工业技术 | 11篇 |
冶金工业 | 2689篇 |
自动化技术 | 5篇 |
出版年
2014年 | 1篇 |
2013年 | 15篇 |
2012年 | 2篇 |
2005年 | 1篇 |
2004年 | 2篇 |
2003年 | 5篇 |
2001年 | 3篇 |
2000年 | 2篇 |
1999年 | 80篇 |
1998年 | 819篇 |
1997年 | 473篇 |
1996年 | 305篇 |
1995年 | 169篇 |
1994年 | 135篇 |
1993年 | 174篇 |
1992年 | 33篇 |
1991年 | 39篇 |
1990年 | 27篇 |
1989年 | 34篇 |
1988年 | 49篇 |
1987年 | 34篇 |
1986年 | 30篇 |
1985年 | 27篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 13篇 |
1981年 | 18篇 |
1980年 | 23篇 |
1979年 | 4篇 |
1978年 | 6篇 |
1977年 | 50篇 |
1976年 | 155篇 |
1975年 | 10篇 |
1974年 | 1篇 |
1971年 | 1篇 |
1968年 | 1篇 |
1967年 | 2篇 |
1966年 | 1篇 |
1957年 | 2篇 |
1955年 | 3篇 |
排序方式: 共有2754条查询结果,搜索用时 15 毫秒
91.
92.
DR Gallie H Le C Caldwell RL Tanguay NX Hoang KS Browning 《Canadian Metallurgical Quarterly》1997,272(2):1046-1053
Several translation initiation factors in mammals and yeast are regulated by phosphorylation. The phosphorylation state of these factors is subject to alteration during development, environmental stress (heat shock, starvation, or heme deprivation), or viral infection. The phosphorylation state and the effect of changes in phosphorylation of the translation initiation factors of higher plants have not been previously investigated. We have determined the isoelectric states for the wheat translation initiation factors eIF-4A, eIF-4B, eIF-4F, eIF-iso4F, and eIF-2 and the poly(A)-binding protein in the seed, during germination, and following heat shock of wheat seedlings using two-dimensional gel electrophoresis and Western analysis. We found that the developmentally induced changes in isoelectric state observed during germination or the stress-induced changes were consistent with changes in phosphorylation. Treatment of the phosphorylated forms of the factors with phosphatases confirmed that the nature of the modification was due to phosphorylation. The isoelectric states of eIF-4B, eIF-4F (eIF-4E, p26), eIF-iso4F (eIF-iso4E, p28), and eIF-2alpha (p42) were altered during germination, suggesting that phosphorylation of these factors is developmentally regulated and correlates with the resumption of protein synthesis that occurs during germination. The phosphorylation of eIF-2beta (p38) or poly(A)-binding protein did not change either during germination or following a thermal stress. Only the phosphorylation state of two factors, eIF-4A and eIF-4B, changed following a heat shock, suggesting that plants may differ significantly from animals in the way in which their translational machinery is modified in response to a thermal stress. 相似文献
93.
JH Markovitz D Smith JM Raczynski A Oberman OD Williams S Knox DR Jacobs 《Canadian Metallurgical Quarterly》1997,157(17):1953-1959
BACKGROUND: Previous studies have suggested that low plasma cholesterol levels or cholesterol lowering may increase the risk of suicide and violent death. Increased aggression, risk-taking behavior, or depression has been associated with low cholesterol levels in some studies. METHODS: A total of 4240 subjects of the Coronary Artery Risk Development in Young Adults study, aged 23 to 35 years, were included in the study. Analyses were stratified by race (black or white) and sex. Persons in the lowest 10% of plasma total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, and triglyceride levels were compared with the other participants in each race/sex group, using standardized measures of hostility, anger suppression, depressive symptoms, and anxiety. The relations between 5-year change in hostility and 5-year change in lipid levels also were examined. The relations between lipid levels and high-risk behavior (e.g., violent arguments or having a gun at home) were examined in a subset of subjects. All analyses were adjusted for relevant covariates. RESULTS: In cross-sectional analyses, low total cholesterol levels were not related to any of the psychological measures in any race/sex group. Among black women only, low low-density lipoprotein cholesterol was related to greater anxiety, and low triglycerides were related to lower anger suppression (P < or = .002). Among white men only, increases in hostility during the 5-year follow-up were related to increases in triglycerides (P < .01), but changes in hostility were unrelated to changes in cholesterol levels. Among a subset of 371 subjects with initially elevated total cholesterol (> or = 5.17 mmol/L [> or = 200 mg/dL]) and a non-medicated decrease of 0.52 mmol/L (> or = 20 mg/dL) or more during 5 years, hostility decreased in a univariate analysis (P < .001). High-risk behaviors also were not associated with low lipid levels. CONCLUSION: The results do not support a consistent relation between hostility, negative affect, or high-risk behaviors with low lipid levels or lipid-lowering among young adults. 相似文献
94.
BACKGROUND: Angiosarcomas are uncommon soft tissue neoplasms with a predilection for skin and superficial soft tissues. CASES: Two cases of angiosarcoma occurred at unusual sites, the parotid gland and lung. The parotid lesion was characterized by malignant cells present singly, in loose groups, in tight three-dimensional aggregates and in acinar formation initially misinterpreted as an adenocarcinoma. The lung mass showed malignant cells in association with vascular endothelium, suggestive of angiosarcoma. Both cases were negative for Ulex europaeus and Factor VIII-related protein but demonstrated strong immunopositivity for CD31, a highly specific endothelial marker. CONCLUSION: In the absence of vasoformative structures, important diagnostic pitfalls are pseudovascular adenoid squamous cell carcinoma, poorly differentiated adenocarcinoma, melanoma and lymphoma. Immunocytochemical studies and clinical history are essential to the correct diagnosis. 相似文献
95.
PURPOSE: We investigated patient satisfaction with a reusable undergarment for urinary incontinence. SUBJECTS AND SETTING: One hundred seventy-five participants with reported urinary incontinence from two urology-based clinics at large teaching hospitals and one prostate cancer support group participated in the study. METHODOLOGY: Each participant was given a minimum of one reusable undergarment for urinary incontinence. Participants used the undergarment for an average of 10 days (range 1 to 60 days). During the trial period, subjects alternated the reusable undergarment with their previous urine-containment devices, usually disposable pads, while the undergarment was being washed. Patient satisfaction was evaluated with a questionnaire. PRIMARY OUTCOME MEASURES: Patient satisfaction with the reusable undergarment was measured for six categories: (1) physical comfort, (2) ability to keep skin dry, (3) ability to prevent wet spots, (4) discretion, (5) odor control, and (6) confidence when wearing the garment versus previously used containment devices. RESULTS: Of the 175 subjects, 126 (33% female and 67% male) completed and returned the 7-page questionnaire. All respondents reported at least one urinary incontinent episode while wearing the reusable undergarment. Occurrence and degree of leakage by self-report varied from light leakage (33%) to moderate leakage (48%) and heavy leakage (17%). Patient satisfaction was measured as follows: (1) 83% rated the overall comfort of the undergarment as very good or excellent; (2) 52% said they felt very dry or dry when wearing the product after an incontinent episodes; (3) 75% rated the ability to prevent wet spots on outer clothing as adequate or excellent; (4) 75% rated the discretion of this product as excellent; (5) 80% rated the ability to control odor as adequate or excellent; and (6) 67% felt more confidence with this reusable undergarment than with other products with which they were familiar. CONCLUSION: The reusable garment provided effective containment from urine loss among this group of incontinent women and men. 相似文献
96.
97.
DR Senger KP Claffey JE Benes CA Perruzzi AP Sergiou M Detmar 《Canadian Metallurgical Quarterly》1997,94(25):13612-13617
Vascular endothelial growth factor (VEGF), also known as vascular permeability factor, is a cytokine of central importance for the angiogenesis associated with cancers and other pathologies. Because angiogenesis often involves endothelial cell (EC) migration and proliferation within a collagen-rich extracellular matrix, we investigated the possibility that VEGF promotes neovascularization through regulation of collagen receptor expression. VEGF induced a 5- to 7-fold increase in dermal microvascular EC surface protein expression of two collagen receptors-the alpha1beta1 and alpha2beta1 integrins-through induction of mRNAs encoding the alpha1 and alpha2 subunits. In contrast, VEGF did not induce increased expression of the alpha3beta1 integrin, which also has been implicated in collagen binding. Integrin alpha1-blocking and alpha2-blocking antibodies (Ab) each partially inhibited attachment of microvascular EC to collagen I, and alpha1-blocking Ab also inhibited attachment to collagen IV and laminin-1. Induction of alpha1beta1 and alpha2beta1 expression by VEGF promoted cell spreading on collagen I gels which was abolished by a combination of alpha1-blocking and alpha2-blocking Abs. In vivo, a combination of alpha1-blocking and alpha2-blocking Abs markedly inhibited VEGF-driven angiogenesis; average cross-sectional area of individual new blood vessels was reduced 90% and average total new vascular area was reduced 82% without detectable effects on the pre-existing vasculature. These data indicate that induction of alpha1beta1 and alpha2beta1 expression by EC is an important mechanism by which VEGF promotes angiogenesis and that alpha1beta1 and alpha2beta1 antagonists may prove effective in inhibiting VEGF-driven angiogenesis in cancers and other important pathologies. 相似文献
98.
99.
RB Roden A Armstrong P Haderer ND Christensen NL Hubbert DR Lowy JT Schiller R Kirnbauer 《Canadian Metallurgical Quarterly》1997,71(8):6247-6252
We have determined that three type-specific and conformationally dependent monoclonal antibodies, H16.E70, H16.U4, and H16.V5, neutralize pseudotype human papillomavirus type 16 (HPV16) virions in vitro. H16.U4 and H16.V5 neutralized pseudotype virions derived from the German HPV16 variant 114K and the Zairian variant Z-1194 with equal efficiency. In contrast, neutralization of Z-1194 pseudotype virions by H16.E70 was two orders of magnitude weaker than neutralization of 114K pseudotype virions. This difference correlated with enzyme-linked immunosorbent assay reactivity of H16.E70 to L1 virus-like particles of the two variants. A substitution at residue 282 of L1 was responsible for this differential reactivity, suggesting that this residue constitutes part of the H16.E70 epitope. 相似文献
100.