全文获取类型
收费全文 | 1828篇 |
免费 | 0篇 |
专业分类
化学工业 | 6篇 |
金属工艺 | 1篇 |
机械仪表 | 1篇 |
建筑科学 | 1篇 |
一般工业技术 | 1篇 |
冶金工业 | 1815篇 |
自动化技术 | 3篇 |
出版年
2022年 | 1篇 |
2014年 | 1篇 |
2013年 | 1篇 |
2005年 | 1篇 |
2003年 | 2篇 |
1999年 | 44篇 |
1998年 | 541篇 |
1997年 | 273篇 |
1996年 | 199篇 |
1995年 | 111篇 |
1994年 | 92篇 |
1993年 | 102篇 |
1992年 | 18篇 |
1991年 | 30篇 |
1990年 | 23篇 |
1989年 | 36篇 |
1988年 | 37篇 |
1987年 | 32篇 |
1986年 | 33篇 |
1985年 | 18篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 8篇 |
1981年 | 11篇 |
1980年 | 21篇 |
1979年 | 2篇 |
1978年 | 5篇 |
1977年 | 55篇 |
1976年 | 126篇 |
1975年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有1828条查询结果,搜索用时 31 毫秒
121.
PR Gibson I Birchall O Rosella V Albert CF Finch DH Barkla GP Young 《Canadian Metallurgical Quarterly》1998,43(5):656-663
The enzyme nitric oxide synthase catalyzes the oxidation of the amino acid L-arginine to L-citrulline and nitric oxide in an NADPH-dependent reaction. Nitric oxide plays a critical role in signal transduction pathways in the cardiovascular and nervous systems and is a key component of the cytostatic/cytotoxic function of the immune system. Characterization of nitric oxide synthase substrates and cofactors has outlined the broad details of the overall reaction and suggested possibilities for chemical steps in the reaction; however, the molecular details of the reaction mechanism are still poorly understood. Recent evidence suggests a role for the reduced bound pterin in the first step of the reaction--the hydroxylation of L-arginine. 相似文献
122.
123.
124.
DK Veronikis DH Nichols MM Wakamatsu 《Canadian Metallurgical Quarterly》1997,177(6):1305-13; discussion 1313-4
OBJECTIVE: Our aims were to compare several prolapse-reducing techniques during urodynamic evaluation and prospectively evaluate their usefulness in identifying the incidence of low urethral closure pressure in continent patients with massive prolapse. STUDY DESIGN: This preoperative, prospective, repeated-measures urodynamic study evaluated the maximum urethral closure pressure with the use of four different techniques in 30 consecutive continent patients with grade 4 prolapse at all vaginal sites. Twenty patients with grade 0 prolapse served as the control group. All patients from the prolapse group underwent surgical treatment and were followed up clinically for a minimum of 1 year. RESULTS: Use of the Scopette (Birchwood Laboratories, Eden Prairie, Minn.) reduction technique to reduce the prolapse in a linear orientation during multichannel urodynamics revealed a 56% incidence of low-pressure urethra and an overall genuine stress urinary incontinence of 83% in patients with massive pelvic organ prolapse but without clinical urinary incontinence. CONCLUSIONS: There may be an increased indication for sling urethropexy in patients with massive prolapse. 相似文献
125.
JP Dubey DH Graham DS da Silva T Lehmann LM Bahia-Oliveira 《Canadian Metallurgical Quarterly》2003,89(4):851-853
Most isolates of Toxoplasma gondii can be grouped into 3 genetic lineages. In the present study, 67 isolates of T. gondii were obtained by bioassay in mice inoculated with brains and hearts of 96 asymptomatic chickens from an area highly endemic to human infection in Rio de Janeiro, Brazil. Of the 48 isolates genotyped using the SAG2 locus, 34 (70%) were of type I and 13 (27%) were of type III. No isolate of type II was recovered. Isolates from 1 chicken contained a type I and type III mixed infection, indicating natural multiparasite infection in the same animal. Cats fed mice infected with 11 type I strains shed 19-535 million oocysts in their feces, indicating that type I isolates can circulate in the environment. 相似文献
126.
Aspergillus sinusitis is an uncommon complication of advanced human immunodeficiency virus (HIV) infection. We describe 2 patients with AIDS who developed histologically proven invasive Aspergillus sinusitis. We also review the findings of 14 histologically documented and 5 probable cases of invasive Aspergillus sinusitis. The literature on the prevalence, predisposing factors, diagnosis, treatment, and prognosis of the infection is reviewed. Major risk factors for the disease are advanced AIDS, chronic sinusitis or otitis, neutropenia, use of corticosteroids and prolonged use of broad spectrum antibiotics. The most common presenting symptoms are nonspecific and include fever, local pain, and swelling. Despite the newer diagnostic and therapeutic approaches discussed herein, the infection is usually fatal in HIV-infected patients. Early diagnosis and aggressive treatment remain the only available means to improve the currently dismal prognosis of Aspergillus sinusitis. 相似文献
127.
AH Rezvani DH Overstreet Y Yang IM Maisonneuve UK Bandarage ME Kuehne SD Glick 《Canadian Metallurgical Quarterly》1997,58(2):615-619
We previously reported that single administration of ibogaine, an indol alkaloid with antiaddictive properties, dose dependently reduced alcohol intake in three strains of alcohol-preferring rats. The present study examined the effect of different doses of a newly developed nontoxic ibogaine analogue, 18-methoxycoronaridine (18-MC), on alcohol intake. Selectively bred alcohol-preferring rats received a single intraperitoneal injection of vehicle or 5, 20 and 40 mg/kg of 18-MC at 9:30 AM, and their consumption of alcohol, water and food was measured for 24 h. Our results demonstrate that a single injection of 18-MC significantly and dose dependently attenuated alcohol consumption and preference and commensurately increased water intake. Only the highest dose of 18-MC significantly decreased food intake. Although the true mechanism of action of 18-MC in suppressing alcohol intake is not yet fully understood, it may, like ibogaine, exert its attenuating effects on alcohol consumption by modulating neurotransmitters believed to be involved in the regulation of alcohol intake. 相似文献
128.
BACKGROUND: Alveolar macrophages are thought to play an important part in regulating lung immune responses. While it is clear that human alveolar macrophages suppress T cell proliferation in vitro, the mechanisms by which this is achieved are not clear, nor is it known whether alveolar macrophages also inhibit other aspects of T cell function. METHODS: Peripheral blood mononuclear cells were stimulated with phytohaemagglutinin or house dust mite allergen, and cultured with variable numbers of autologous alveolar macrophages obtained by bronchoalveolar lavage from 20 normal subjects. RESULTS: Alveolar macrophages induced a reversible inhibition of T cell proliferation in response to both mitogen and allergen stimulation, with the latter being considerably more susceptible to inhibition. This was achieved via heterogenous mechanisms, involving both soluble factors derived from alveolar macrophages and cell-cell contact. Despite inhibiting proliferation, alveolar macrophages had little or no effect on T cell calcium flux, the characteristic changes in CD3, CD2, CD28 and interleukin-2 (IL-2) receptor expression which accompany normal T cell activation, and IL-2 and interferon gamma secretion. In contrast, alveolar macrophages inhibited the tyrosine phosphorylation of proteins which may be involved in IL-2 receptor-associated signal transduction. CONCLUSIONS: The immunoregulatory properties of alveolar macrophages are relatively selective, allowing T cell activation and cytokine secretion while inhibiting T cell proliferation within the lung. 相似文献
129.
130.