全文获取类型
收费全文 | 1844篇 |
免费 | 2篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 2篇 |
化学工业 | 26篇 |
金属工艺 | 1篇 |
机械仪表 | 3篇 |
建筑科学 | 1篇 |
能源动力 | 28篇 |
轻工业 | 8篇 |
无线电 | 6篇 |
一般工业技术 | 13篇 |
冶金工业 | 1747篇 |
原子能技术 | 1篇 |
自动化技术 | 11篇 |
出版年
2021年 | 4篇 |
2016年 | 2篇 |
2015年 | 1篇 |
2014年 | 1篇 |
2013年 | 2篇 |
2012年 | 2篇 |
2011年 | 2篇 |
2010年 | 3篇 |
2009年 | 6篇 |
2008年 | 1篇 |
2007年 | 6篇 |
2006年 | 4篇 |
2005年 | 5篇 |
2004年 | 4篇 |
2003年 | 3篇 |
2002年 | 6篇 |
2001年 | 2篇 |
2000年 | 4篇 |
1999年 | 57篇 |
1998年 | 583篇 |
1997年 | 300篇 |
1996年 | 203篇 |
1995年 | 88篇 |
1994年 | 86篇 |
1993年 | 96篇 |
1992年 | 11篇 |
1991年 | 30篇 |
1990年 | 22篇 |
1989年 | 26篇 |
1988年 | 21篇 |
1987年 | 26篇 |
1986年 | 22篇 |
1985年 | 28篇 |
1984年 | 1篇 |
1983年 | 6篇 |
1982年 | 6篇 |
1981年 | 10篇 |
1980年 | 19篇 |
1979年 | 1篇 |
1978年 | 6篇 |
1977年 | 39篇 |
1976年 | 87篇 |
1975年 | 4篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1968年 | 1篇 |
1962年 | 1篇 |
1955年 | 1篇 |
1938年 | 1篇 |
排序方式: 共有1847条查询结果,搜索用时 31 毫秒
31.
Two cases of cystic hygroma arising as a primary lesion in the chest are presented. Because of calcifications discovered on CT and because of the anterior location of the mass in both cases, teratoma was the first diagnostic consideration. However, after surgical removal, histologic study determined that both lesions were cystic hygromas with areas of scattered calcification probably secondary to hemorrhage. These cases are presented because of the remarkable similarity of their imaging features to those of teratoma. 相似文献
32.
AL Barry PC Fuchs C Thornsberry JC McLaughlin SG Jenkins DJ Hardy SD Allen 《Canadian Metallurgical Quarterly》1996,15(8):676-678
Three methods approved by the National Committee for Clinical Laboratory Standards for testing the susceptibility of anaerobic bacteria were used to evaluate the fluoroquinolone, trovafloxacin. The methods gave essentially comparable results with 126 anaerobes and with three quality control strains. A collaborative study defined the quality control range for trovafloxacin MICs. Trovafloxacin had good in vitro activity against the more common anaerobes (MIC 90 < = or 2.0 micrograms/ml). 相似文献
33.
SD Edwards 《Canadian Metallurgical Quarterly》1996,92(43):34-35
This paper discusses a hypothetical situation, taken from the author's book Nursing Ethics: a principle-based approach, in which a nurse feels pressured into working beyond his official span of duty. The nurse experiences a conflict between a number of obligations; to patients and clients, to his family and to himself. To which should he give greatest weight? Steven Edwards suggests the nurse's decision is a moral one, based on personal standards held by the nurse. 相似文献
34.
S Dawson D Bennett SD Carter M Bennett J Meanger PC Turner MJ Carter I Milton RM Gaskell 《Canadian Metallurgical Quarterly》1994,56(2):133-143
Twelve specific pathogen-free cats were infected either by intra-articular inoculation or by contact exposure to one of two strains of feline calicivirus (FCV), either F65, a field strain originating from an outbreak of lameness in a group of cats, or a vaccine strain. Following either route of exposure, both strains induced signs typical of FCV infection including oral and nasal ulceration, conjunctivitis and ocular discharge. These signs were of equal severity for both virus strains, but overall, following either route of infection, F65 induced more severe disease than the vaccine strain, with marked pyrexia, lethargy and lameness. Vaccine virus only induced a relatively mild lameness following intra-articular inoculation. Gross pathological and histopathological lesions were seen in some of the joints, but again changes were more severe in the F65-exposed cats. Virus was isolated from both normal and affected joints from both groups of F65-exposed cats, and from a joint from each cat inoculated intra-articularly with vaccine virus. Mild transient lameness was also seen in one of two control cats inoculated intra-articularly, but no pathological changes were seen or virus isolated from joints. A cDNA probe used in RNA dot blot hybridisation experiments was found to be specific and more sensitive than virus isolation in detecting FCV in selected tissues. This may be useful in future studies on the pathogenesis of FCV disease and in studies on viral persistence in FCV carriers. 相似文献
35.
Activation of auditory cortex during silent lipreading 总被引:1,自引:0,他引:1
GA Calvert ET Bullmore MJ Brammer R Campbell SC Williams PK McGuire PW Woodruff SD Iversen AS David 《Canadian Metallurgical Quarterly》1997,276(5312):593-596
Watching a speaker's lips during face-to-face conversation (lipreading) markedly improves speech perception, particularly in noisy conditions. With functional magnetic resonance imaging it was found that these linguistic visual cues are sufficient to activate auditory cortex in normal hearing individuals in the absence of auditory speech sounds. Two further experiments suggest that these auditory cortical areas are not engaged when an individual is viewing nonlinguistic facial movements but appear to be activated by silent meaningless speechlike movements (pseudospeech). This supports psycholinguistic evidence that seen speech influences the perception of heard speech at a prelexical stage. 相似文献
36.
Previous studies have shown that Tetrahymena citrate synthase and the Tetrahymena 14-nm filament protein are encoded by a single gene and translated from one species of mRNA, and that they are identical in terms of molecular weight, antigenicity, and some enzymatic properties. In this study, using two-dimensional gel electrophoresis, we demonstrated that the citrate synthase comprised pI 7.7 and 8.0 isoforms, while the 14-nm filament protein comprised three isoforms with isoelectric points of 7.7, 8.0, and 8.4. The amino acid sequences of the NH2-terminal portions of all isoforms were identical and the peptide maps with V8 protease were almost the same. In addition, when the citrate synthase activity of each isoform was measured after separation by non-urea isoelectric focusing without denaturing treatment, the pI 7.7 and/or pI 8.0 isoforms exhibited the citrate synthase activity, but the pI 8.4 isoform only found for the 14-nm filament protein did not possess this activity. These results suggest that the polymorphism of these isoforms is caused by some posttranslational modifications, and that it may have resulted in the different compartmentalization and functions of Tetrahymena citrate synthase and the 14-nm filament protein. 相似文献
37.
ZR Gan Y Li TM Connolly MK Sardana PK Tsai SD Lewis JA Shafer 《Canadian Metallurgical Quarterly》1993,301(2):228-236
Site-directed mutagenesis was employed to assess the importance of the Arg-Gly-Asp triplet that comprises residues 197 to 199 in the B-chain of thrombin. Properties of the R197E and the D199E variants were compared with those of zeta-thrombin and the inactive S205A variant wherein the active site Ser is replaced by Ala. Relative to zeta-thrombin, the R197E thrombin variant under the assay conditions used exhibits 26% activity toward a small chromogenic substrate, 13% activity in the activation of protein C in the presence of thrombomodulin, < 3% activity in processing fibrinogen, and 1% activity in inducing platelet activation. Thus, the substrate specificity of thrombin was altered by the R197-->E replacement. The D199E variant was essentially inactive. It exhibited only 0.02% of the activity of thrombin toward the chromogenic substrate and its reactivity toward the active site-directed alkylating agent D-Phe-Pro-Arg-CH2Cl was 10,000-fold lower than that of thrombin. Like the inactive S205A thrombin variant, the D199E variant antagonized the interactions of thrombin with hirudin and thrombomodulin, but was a less effective antagonist. The dependence of the antagonism of the thrombin-thrombomodulin interaction on the concentration of D199E thrombin variant provided evidence suggesting the presence of two or more domains in thrombin that independently interact with their counterparts in thrombomodulin. Although the S205A thrombin variant antagonized the action of thrombin on platelets no such activity could be demonstrated for the D199E variant in the concentration range studied (< 800 nm). Comparison of the circular dichroism spectra of zeta-thrombin, the D199E, R197E, and S205A variants indicated that subtle differences in conformation exist between the D199E variant and the other thrombins. These differences in conformation might well account for the altered behavior of the D199E variant with respect to its interactions toward thrombomodulin, hirudin, and platelets. 相似文献
38.
39.
RL Conhaim SD Cooler AM McGrath DA DeAngeles GA Myers BA Harms 《Canadian Metallurgical Quarterly》1998,158(4):1204-1212
Diaspirin crosslinked hemoglobin (DCHb) is a new blood substitute manufactured from human blood. To evaluate its microvascular filtration properties, we infused DCLHb into unanesthetized sheep (10%, 20 ml/kg) and measured the flow and composition of lung and soft tissue lymph. For comparison, we also infused human serum albumin (HSA; 10%, 20 ml/kg). DCLHb raised systemic and pulmonary arterial pressures from baseline values of 83 +/- 7 and 13 +/- 2 mm Hg, respectively, to peak values of 113 +/- 9 and 26 +/- 3 mm Hg (p < 0.05 versus baseline). These increases were significantly greater than those associated with HSA, which raised systemic and pulmonary arterial pressures from baseline values of 86 +/- 4 and 13 +/- 2 mm Hg, respectively, to peak values of 97 +/- 3 and 21 +/- 7 mm Hg (p <= 0.05 versus baseline and versus DCLHb). These differences reflect the known pressor properties of DCLHb. Accordingly, DCLHb raised lung and soft tissue lymph flows to peak values of 12.2 +/- 3.8 and 1.6 +/- 0.7 ml/30 min, respectively, while HSA raised lung and soft tissue lymph flows to peak values of 7.5 +/- 4.8 and 4.6 +/- 1.9 ml/30 min, respectively (p <= 0.05 versus DCLHb). The half-times of DCLHb equilibration from plasma into lung and soft tissue lymph of 1. 0 +/- 0.3 and 2.1 +/- 1.1 h, respectively, were significantly faster than HSA equilibration half-times of 3.1 +/- 0.2 and 3.8 +/- 0.9 h. Filtration differences between DCLHb and HSA appear to be due to the pressor properties DCLHb. 相似文献
40.
OBJECTIVE: To determine whether concurrent intravenous administration of the loop diuretic ethacrynic acid potentiates the toxicity of the aminoglycoside antibiotic gentamicin applied topically on the round window. STUDY DESIGN: The authors studied the effects on cochlear sensitivity of co-administered intracardiac ethacrynic acid (40 mg/kg) and high-dose topical gentamicin solution (100%) applied to the round window. Comparisons were made with animals receiving ethacrynic acid plus systemic gentamicin (100 mg/kg); topical gentamicin alone; systemic gentamicin alone; and intravenous ethacrynic acid alone. METHODS: Experiments were carried out on pigmented guinea pigs weighing 400 to 500 g. Changes in cochlear function were characterized by monitoring shifts in compound action potential (CAP) thresholds by use of chronic indwelling electrodes implanted at the round window, vertex, and contralateral mastoid. RESULTS: After 20 days animals receiving ethacrynic acid in combination with topical gentamicin to the round window failed to demonstrate a significant deterioration in cochlear sensitivity, whereas all animals receiving systemic gentamicin plus ethacrynic acid experienced profound increases in CAP thresholds. CONCLUSIONS: This study supports the contention that ethacrynic acid potentiates aminoglycoside ototoxicity by facilitating the entry of the antibiotics from the systemic circulation into the endolymph. In addition, this study answers important clinical concerns regarding the safety of the use of topical aminoglycoside agents in combination with loop diuretics. 相似文献