全文获取类型
收费全文 | 2014篇 |
免费 | 1篇 |
专业分类
电工技术 | 1篇 |
化学工业 | 16篇 |
金属工艺 | 10篇 |
机械仪表 | 3篇 |
轻工业 | 6篇 |
石油天然气 | 1篇 |
无线电 | 3篇 |
一般工业技术 | 7篇 |
冶金工业 | 1958篇 |
自动化技术 | 10篇 |
出版年
2022年 | 1篇 |
2021年 | 1篇 |
2017年 | 1篇 |
2015年 | 1篇 |
2014年 | 1篇 |
2013年 | 6篇 |
2012年 | 1篇 |
2011年 | 3篇 |
2010年 | 3篇 |
2009年 | 1篇 |
2008年 | 1篇 |
2007年 | 1篇 |
2006年 | 2篇 |
2005年 | 4篇 |
2004年 | 1篇 |
2003年 | 4篇 |
2002年 | 1篇 |
2000年 | 1篇 |
1999年 | 58篇 |
1998年 | 580篇 |
1997年 | 327篇 |
1996年 | 199篇 |
1995年 | 118篇 |
1994年 | 113篇 |
1993年 | 114篇 |
1992年 | 26篇 |
1991年 | 39篇 |
1990年 | 29篇 |
1989年 | 45篇 |
1988年 | 38篇 |
1987年 | 26篇 |
1986年 | 29篇 |
1985年 | 18篇 |
1984年 | 1篇 |
1983年 | 7篇 |
1982年 | 13篇 |
1981年 | 8篇 |
1980年 | 12篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 53篇 |
1976年 | 120篇 |
1975年 | 2篇 |
1968年 | 1篇 |
1967年 | 1篇 |
1961年 | 1篇 |
排序方式: 共有2015条查询结果,搜索用时 15 毫秒
71.
In sensory hair cells of the cochlea, deflection of the stereociliary bundle results in direct mechanical gating of mechanoelectrical transduction channels, a function generally attributed to the tip link running between the tips of short stereocilia and the sides of adjacent taller ones. However, immunocytochemical experiments indicate that the channels may not be associated with the tip link but occur just below it in a region of contact between the stereocilia. To determine whether transduction channels in this location could be operated during physiologically appropriate deflections as effectively by shear displacement as if they were associated with the tip link, a two dimensional kinematic analysis of relative motion between stereocilia has been performed assuming contact between stereocilia is maintained during deflection. Bundle geometry and dimensions were determined from transmission electron micrographs of hair cells from several frequency locations between 0.27 and 13.00 kHz in the guinea-pig cochlea. The analysis indicates that for a 10 nm deflection of the tallest stereocilia of both inner and outer hair cells, i.e. within the range of the maximum sensitivity of mammalian hair bundles, the average shear displacement in the contact region would be 1.6 nm, but that it increases systematically towards higher frequency regions for outer hair cells. This displacement is comparable in magnitude to tip-link elongation for individual stereociliary pairs. 相似文献
72.
M González LA Bagatolli I Echabe JL Arrondo CE Argara?a CR Cantor GD Fidelio 《Canadian Metallurgical Quarterly》1997,272(17):11288-11294
The effect of biotin binding on streptavidin (STV) structure and stability was studied using differential scanning calorimetry, Fourier transform infrared spectroscopy (FT-IR), and fluorescence spectroscopy. Biotin increases the midpoint temperature Tm, of thermally induced denaturation of STV from 75 degrees C in unliganded protein to 112 degrees C at full ligand saturation. The cooperativity of thermally induced unfolding of STV changes substantially in presence of biotin. Unliganded STV monomer has at least one domain that unfolds independently. The dimer bound to biotin undergoes a single coupled denaturation process. Simulations of thermograms of STV denaturation that take into account only the thermodynamic effects of the ligand with a Ka approximately 10(15) reproduce the behavior observed, but the estimated values of Tm are 15-20 degrees C lower than those experimentally determined. This increased stability is attributed to an enhanced cooperativity of the thermal unfolding of STV. The increment in the cooperativity is as consequence of a stronger intersubunit association and an increased structural order upon binding. FT-IR and fluorescence spectroscopy data reveal that unordered structure found in unliganded STV disappears under fully saturating conditions. The data provide a rationale for previous suggestions that biotin binding induces an increase in protein tightness (structural cooperativity) leading, in turn, to a higher thermostability. 相似文献
73.
In this study, we examined whether endothelin (ET) plays a role in the short-term increase in mean arterial pressure (MAP) after nitric oxide synthase (NOS) inhibition with N(omega)-nitro-L-arginine methyl ester (L-NAME) in stroke-prone spontaneously hypertensive rats (SHRSPs). Experiments were performed by using Inactin-anesthetized male SHRSPs that were pretreated with chlorisondamine to block reflex autonomic cardiovascular effects. Injection of L-NAME (10 mg/kg, i.v.), but not D-NAME, produced rapid and marked increases (74 +/- 3 mm Hg) in MAP that were sustained for >1 h. In SHRSPs that were treated with the ET(A/B) receptor antagonist, L-754,142 (15 mg/kg + 15 mg/kg/h), L-NAME increased MAP by 45 +/- 4 mm Hg (p < 0.0001 compared with L-NAME alone). L-754,142 blocked pressor responses to big ET-1 by >90% but was without effect on pressor responses to norepinephrine. Plasma levels of ET-1 averaged 5 +/- 1 pg/ml in animals given vehicle and were slightly increased in animals given either L-NAME alone (7 +/- 2 pg/ml) or L-754,142 alone (7 +/- 2 pg/ml) but increased markedly when L-NAME and L-754,142 were given together (114 +/- 18 pg/ml). This may relate to an effect of L-754,142 to block ET-receptor-mediated clearance of ET-1. We conclude that ET plays a role in the short-term pressor response after NOS inhibition in SHRSPs. 相似文献
74.
We have previously described a model of outpatient integrated treatment for patients with comorbid psychoactive substance use disorders and schizophrenia (PSUD/S)(1). Here we review relevant literature on comorbidity and outline the rationale for integrated services. Further, we describe results from 3 related studies: First, we document the approximate incidence of PSUD among a heterogeneous group of 602 schizophrenic inpatient admissions to our hospital. Second, we describe in greater detail the psychiatric symptoms and patterns of substance abuse among a subsample of 106 inpatients with PSUD/S, contrasting them with 112 patients with PSUD and mixed psychotic disorders, but who are not schizophrenic. Third, we present a prospective research project and describe a sample of 30 patients with PSUD/S, detailing demographic characteristics, psychiatric symptoms and substance abuse history. Attention is given to current issues in the differential diagnosis of patients with PSUD/S using standardized instruments. 相似文献
75.
Insomnia may be periodic and transient, as caused by situational stress, or persistent, as caused by a chronic sleep disorder. Physicians can gain much information concerning the type, probable cause, onset, and duration of insomnia through history taking. A sleep diary may reveal helpful information, and input from the patient's sleeping partner can also be valuable. Complicating disorders, such as heart failure, prostatism, or depression, should be sought and specific treatment prescribed. Chemical dependency, too, requires appropriate treatment. These measures, institution of good sleep-hygiene practices, and behavior modification may resolve sleeplessness. The primary indication for use of hypnotic agents is transient sleep disruption caused by acute stress. When an agent is chosen, onset of action, metabolism, and side effects should be considered, especially in elderly patients. Addictive agents should not be given to patients with substance abuse problems. If insomnia persists, evaluation at a sleep-disorder center is recommended to facilitate design of an appropriate therapeutic regimen. 相似文献
76.
V Montserrat Orri E López-Bonet G Garijo M Ordis N Torrent CR Valiente JL Alvarez 《Canadian Metallurgical Quarterly》1996,20(7):659-661
Report of one case of pure yolk sack testicular tumour in an adult patient. This was a stage I case which had been under observation for 3 years without further evidence of disease. Several aspects related with this type of germinal, non-seminomatous tumour of the testicle are commented upon. 相似文献
77.
CL Patton PS Millard CR Kessenich D Storm E Kinnicutt CJ Rosen 《Canadian Metallurgical Quarterly》1998,7(7):909-915
We compared calcaneal ultrasound measurements (speed of sound [SOS], broadband ultrasound attenuation [BUA], and stiffness index [SI]) of lesbian and heterosexual women to examine the medical and lifestyle risk factors for osteoporosis in each group. This was an exploratory, community-based, cross-sectional study. Subjects were mailed food frequency, health, and physical activity questionnaires. Weight, height, and calcaneal ultrasound measurements were taken at one office visit. In communities in southern and eastern Maine, 71 lesbians and 77 heterosexual women between the ages of 30 and 50 with regular menses and in good general health were the subjects. Statistical analysis used t-tests and chi-square tests to evaluate differences between study groups. Linear regression models were used to evaluate risk factors for low calcaneal ultrasound measurements. There were no differences between the lesbian and heterosexual women in age, body mass index (BMI), exercise, calcium intake, alcohol use, or calcaneal ultrasound measurements. There was a positive association between BUA and both BMI and alcohol consumption (p < 0.01). Antidepressant use significantly reduced SOS and SI (p < 0.05). There were no differences in calcaneal ultrasound measurements between lesbian and heterosexual women. BMI was strongly and positively associated with BUA. Antidepressant use in both populations was associated with a significant reduction in calcaneal bone mass. Studies are needed to define the relationship of depression and its treatment to bone mineral density and the future risk of osteoporosis. 相似文献
78.
PURPOSE: To determine if ethnic and gender differences in smoking (lifetime prevalence and 30-day prevalence) exist among a cohort of Asian, black, Hispanic, and white inner-city adolescents during the 3-year middle school period. METHODS: Students in 22 urban schools completed self-report questionnaires and provided carbon monoxide breath samples at three annual assessments. Chi-square analyses were conducted to test for associations between ethnic group (Asian, black, Hispanic, and white) and smoking and to test for gender differences in smoking within each ethnic group. Additional analyses examined differences in smoking between two Hispanic subgroups (Puerto Rican and Dominican). RESULTS: Ethnicity was associated with lifetime smoking prevalence at all three assessment points but was only associated with 30-day smoking prevalence at the 2-year follow-up. However, there were no differences in smoking between Puerto Rican and Dominican youth. Black girls reported higher lifetime smoking prevalence than black boys at all three assessments. At the 2-year follow-up, Asian boys reported higher lifetime smoking prevalence than Asian girls; Hispanic girls reported higher 30-day prevalence than Hispanic boys. CONCLUSIONS: White and Hispanic adolescents were at higher risk for smoking relative to Asian and black adolescents. With the exception of white youth, gender differences were found within each ethnic group. 相似文献
79.
80.