全文获取类型
收费全文 | 1317篇 |
免费 | 0篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 1篇 |
化学工业 | 3篇 |
金属工艺 | 2篇 |
建筑科学 | 2篇 |
轻工业 | 1篇 |
一般工业技术 | 1篇 |
冶金工业 | 1306篇 |
自动化技术 | 3篇 |
出版年
2011年 | 2篇 |
2007年 | 1篇 |
2004年 | 1篇 |
2003年 | 2篇 |
1999年 | 30篇 |
1998年 | 359篇 |
1997年 | 230篇 |
1996年 | 140篇 |
1995年 | 74篇 |
1994年 | 81篇 |
1993年 | 76篇 |
1992年 | 12篇 |
1991年 | 22篇 |
1990年 | 18篇 |
1989年 | 24篇 |
1988年 | 16篇 |
1987年 | 31篇 |
1986年 | 23篇 |
1985年 | 12篇 |
1983年 | 3篇 |
1982年 | 14篇 |
1981年 | 8篇 |
1980年 | 16篇 |
1978年 | 4篇 |
1977年 | 38篇 |
1976年 | 78篇 |
1975年 | 3篇 |
1955年 | 1篇 |
排序方式: 共有1319条查询结果,搜索用时 15 毫秒
11.
12.
13.
A longitudinal study evaluating the degree of rotation of the bimalleolar axis of tibia and fibula at birth, 6 month, 12 months and 24 months revealed a gradual statistically significant external rotation from a mean of 4 degrees at birth to a mean of 11 degrees at 24 months. There was no correlation with the sex or race of the child or with the age at which the child began independent walking. It is concluded that this external rotation is a part of normal growth and development of the infants' lower extremities. 相似文献
14.
V Rodriguez J Gottlieb MA Burgess R Livingston W Wheeler G Spitzer GP Bodey GR Blumenschein EJ Freireich 《Canadian Metallurgical Quarterly》1976,38(2):690-694
Phase I studies were conducted in 58 adult cancer patients with Baker's Antifol (BAF), a new active-site directed inhibitor of dihydrofolate reductase. Dose escalation ranged from 10 to 250 mg/m2/day X 5 days and courses of treatment were repeated every 2-3 weeks. Biologic effects were observed mostly at doses greater than 100 mg/m2/day X 5 days. The patients developed myelosuppression during 19% of the trials. Other types of toxicity were dermatitis in 12 to 30% and stomatitis in 7 to 38% of the trials. Toxicity was directly related to the impairment of the patient's liver function. Two partial responses (in a patient with adenocarcinoma of the lung and a patient with transitional cell carcinoma of the bladder) occurred. BAF is an active new chemotherapeutic agent which deserves further clinical trials in patients with various malignancies. 相似文献
15.
Archaea represent some of the most ancient organisms on earth, and they have relatively uncharacterized DNA repair processes. We now show, using an in vitro assay, that extracts of two Crenarchaeota (Sulfolobus acidocaldarius and Pyrobaculum islandicum) and two Euryarchaeota (Pyrococcus furiosus and Thermococcus litoralis) contain the DNA repair protein O6-alkylguanine-DNA alkyltransferase (ATase). The ATase activities found in the archaea were extremely thermostable, with half-lives at 80 degreesC ranging from 0.5 hr (S. acidocaldarius) to 13 hr (T. litoralis). The temperature optima of the four proteins ranged from approximately 75 to approximately 100 degreesC, although activity was seen at 37 degreesC, the temperature optimum of the Escherichia coli and human ATases. In all cases, preincubaton of extracts with a short oligonucleotide containing a single O6-methylguanine residue caused essentially complete loss of ATase activity, suggesting that the alkylphosphotriester-DNA alkyltransferase activity seen in some prokaryotes is not present in Archaea. The ATase from Pyrobaculum islandicum had an apparent molecular mass of 15 kDa, making it the smallest of these proteins so far described. In higher organisms, ATase is responsible for the repair of toxic and mutagenic O6-alkylguanine lesions in alkylated DNA. The presence of ATase in these primitive organisms therefore suggests that endogenous or exogenous exposure to agents that generate appropriate substrates in DNA may be an early event in evolution. 相似文献
16.
AM Cirla N Sforza GP Roffi A Alessandrini R Stanizzi N Dorigo E Sala F Della Torre 《Canadian Metallurgical Quarterly》1996,51(5):299-305
A double-blind, placebo-controlled study was carried out to test the clinical efficacy and safety of local nasal immunotherapy (LNIT) in powder form. Twenty-two patients suffering from allergic rhinitis strictly associated with early spring symptoms, with positive skin prick tests and RAST for birch-alder, all responders to a specific nasal provocation test (NPT), received randomly active or placebo treatment for 4 months. Immunotherapy consisted of administration of a set of capsules containing progressively increasing amounts of birch (Betula pendula) and speckled alder (Alnus incana) allergens in powder form with controlled granulometry. The active (birch-alder) and placebo (lactose) group completed the treatment according to a similar schedule. During the pollen season (March-April), the patients who took the active treatment reported less sneezing and rhinorrhea than the placebo group, on the basis of a symptoms score, and the differences were statistically significant; the need for drugs (terfenadine) was also significantly reduced. These findings agreed well with the results of specific NPT after the treatment; only patients in the active group had a higher threshold dose of nasal specific reactivity to birch-alder allergens than in tests before the LNIT. 相似文献
17.
To assess the interaction of dopamine and acetylcholine systems in the rat nucleus accumbens in response to direct D-amphetamine administration, in vivo microdialysis measures of acetylcholine were used during reverse dialysis of amphetamine alone and in combination with D1 and D2 receptor antagonists SCH 23390 and sulpiride, respectively. During a 15-min exposure to amphetamine (50 microM) in the nucleus accumbens, acetylcholine increased to 33% above pre-infusion levels, became maximal at 15 min post-infusion (+41%) and gradually returned to baseline levels by 60 min post-amphetamine. Conversely, amphetamine (1 mM) administration caused a biphasic change in acetylcholine release with a trend toward a decrease (-14%) during exposure followed by a significant increase (+36%) at 30 min post-amphetamine that returned to baseline levels by 60 min after infusion. The increases observed during amphetamine (50 microM) exposure and during recovery from amphetamine (1 mM) were both blocked by co-administration with the D1 antagonist, SCH 23390 (10 microM), but not with the D2 antagonist, sulpiride (10 microM). Co-infusion of sulpiride eliminated the trend toward reduced acetylcholine release observed during 1 mM amphetamine whereas co-administration of SCH 23390 potentiated this decrease. A possible tonic D1 facilitation of nucleus accumbens acetylcholine release was indicated by the consistent reductions in acetylcholine release observed during infusion of SCH 23390. These results suggest that amphetamine administration in the nucleus accumbens induces a bidirectional change in acetylcholine release that is dependent on dose and opposing effects of nucleus accumbens D1 and D2 activation. In general, relatively low doses of amphetamine administered into the nucleus accumbens caused an increase in acetylcholine release that was dependent on dopamine D1 receptors whereas higher doses of amphetamine resulted in a D2-mediated decrease. 相似文献
18.
A Fawzy K Braun GP Lewis M Gaffney K Ice N Dias 《Canadian Metallurgical Quarterly》1995,154(1):105-109
A 16-week, double-blind, placebo controlled, dose titration study was done on 100 normotensive patients age 45 years or older to determine the efficacy and safety of doxazosin, a selective alpha 1-adrenoceptor antagonist, in the treatment of benign prostatic hyperplasia (BPH). Of the 41 efficacy evaluable patients 88% underwent dose titration to a maximum of 8 mg. doxazosin once daily. Maximum and average urinary flow rates increased significantly above baseline with doxazosin (2.9 ml. per second and 1.4 ml. per second, respectively) compared with placebo (0.7 ml. per second and 0.3 ml. per second, respectively). A significant effect on maximum flow rate was noted as early as week 2 of double-blind treatment at the initial efficacy evaluation. Doxazosin was superior to placebo in patient and investigator assessments of total, obstructive and irritative BPH symptoms. The onset of efficacy for total patient-assessed symptoms was significant for doxazosin compared to placebo 4 weeks after the start of the treatment regimen. Statistically significant decreases in mean blood pressure of 4 to 6 mm. Hg were noted with doxazosin compared with placebo. Adverse events, primarily mild to moderate in severity, were reported in 44% of patients given doxazosin and 30% of those given placebo. Our results strongly demonstrate that doxazosin is significantly superior to placebo in the treatment of BPH in normotensive patients, with the patient experiencing significant relief early after initiation of therapy. 相似文献
19.
20.