全文获取类型
收费全文 | 5848篇 |
免费 | 36篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 45篇 |
综合类 | 2篇 |
化学工业 | 529篇 |
金属工艺 | 36篇 |
机械仪表 | 59篇 |
建筑科学 | 139篇 |
矿业工程 | 4篇 |
能源动力 | 58篇 |
轻工业 | 214篇 |
水利工程 | 28篇 |
石油天然气 | 2篇 |
无线电 | 356篇 |
一般工业技术 | 467篇 |
冶金工业 | 3560篇 |
原子能技术 | 35篇 |
自动化技术 | 351篇 |
出版年
2021年 | 31篇 |
2019年 | 21篇 |
2018年 | 39篇 |
2017年 | 34篇 |
2016年 | 32篇 |
2015年 | 18篇 |
2014年 | 46篇 |
2013年 | 162篇 |
2012年 | 67篇 |
2011年 | 99篇 |
2010年 | 82篇 |
2009年 | 80篇 |
2008年 | 100篇 |
2007年 | 93篇 |
2006年 | 79篇 |
2005年 | 88篇 |
2004年 | 76篇 |
2003年 | 76篇 |
2002年 | 68篇 |
2001年 | 72篇 |
2000年 | 64篇 |
1999年 | 135篇 |
1998年 | 1060篇 |
1997年 | 625篇 |
1996年 | 413篇 |
1995年 | 314篇 |
1994年 | 200篇 |
1993年 | 241篇 |
1992年 | 78篇 |
1991年 | 69篇 |
1990年 | 83篇 |
1989年 | 71篇 |
1988年 | 74篇 |
1987年 | 83篇 |
1986年 | 70篇 |
1985年 | 66篇 |
1984年 | 42篇 |
1983年 | 43篇 |
1982年 | 40篇 |
1981年 | 68篇 |
1980年 | 57篇 |
1979年 | 35篇 |
1978年 | 28篇 |
1977年 | 129篇 |
1976年 | 210篇 |
1975年 | 29篇 |
1974年 | 24篇 |
1973年 | 20篇 |
1972年 | 19篇 |
1971年 | 18篇 |
排序方式: 共有5885条查询结果,搜索用时 15 毫秒
41.
LJ Diehl CK Mathiason-Dubard LL O'Neil EA Hoover 《Canadian Metallurgical Quarterly》1996,70(4):2503-2507
Viral RNA load has been shown to indicate disease stage and predict the rapidity of disease progression in human immunodeficiency virus type 1 (HIV-1)-infected individuals. We had previously demonstrated that feline immunodeficiency virus (FIV) RNA levels in plasma correlate with disease stage in infected cats. Here we expand upon those observations by demonstrating that plasma virus load is 1 to 2 logs higher in cats with rapidly progressive FIV disease than in long-term survivors. Differences in plasma FIV RNA levels are evident by 1 to 2 weeks after infection and are consistent throughout infection. We also evaluated humoral immune responses in FIV-infected cats for correlation with survival times. Total anti-FIV antibody titers did not differ between cats with rapidly progressive FIV disease and long-term survivors. These findings indicate that virus replication plays an important role in FIV disease progression, as it does in HIV-1 disease progression. The parallels in virus loads and disease progressions between HIV-1 and FIV support the idea that the accelerated disease model is well suited for the study of therapeutic agents directed at reducing lentiviral replication. 相似文献
42.
EA Chernoff 《Canadian Metallurgical Quarterly》1996,40(4):823-831
To study the triggering mechanism(s) of the induction of apoptosis following exposure to u.v. light, we used a genetic approach involving cell strains derived from patients with inherited deficiencies in nucleotide excision repair. It was found that cells from patients with Cockayne's syndrome, which are deficient in the processing of u.v.-induced pyrimidine dimers from the transcribed DNA strand, are induced to undergo apoptosis at much lower doses of u.v. light than cells with proficient strand-specific repair. The induction of apoptosis correlated to the induction of p53 and to the inhibition of total RNA and poly(A) mRNA synthesis. We also show that active p53 proteins accumulate following u.v.-irradiation without any apparent requirement for DNA strand breaks or excision repair intermediates. We propose that the blockage of RNA polymerases at DNA lesions in the transcribed strand triggers the induction of a pathway leading to apoptosis. These findings may help explain a long standing enigma of why, despite the DNA repair deficiency, patients with Cockayne's syndrome do not experience an elevated risk for skin cancer since potentially pre-mutagenic cells are eliminated by an easily triggered apoptotic pathway. 相似文献
43.
This paper develops a transient thermal model for line traps. The model was incorporated into a computer program that numerically integrates the governing nonlinear differential equation in time to predict critical temperatures and component short and long term ratings for a wide range of operating conditions. The model accounts for many factors including: variable air properties, variable material properties, environmental conditions, and a wide variety of component geometries and orientations. To verify the temperatures predicted by the thermal model, The Georgia Power Research Center carried out an extensive series of indoor laboratory tests to experimentally measure temperatures of energized line traps under transient loading conditions. Model predictions were within 8°C for 75 percent of the data. This paper presents the development of the governing equations and describes in detail the calculation of the convective and radiative components of heat transfer. Comparisons of the model predictions for two different line trap designs in different orientations to experimental data are presented to demonstrate the accuracy and flexibility of the thermal model 相似文献
44.
Responsiveness of self-reported and objective measures of disease severity in carpal tunnel syndrome
JN Katz RH Gelberman EA Wright RA Lew MH Liang 《Canadian Metallurgical Quarterly》1994,32(11):1127-1133
Responsiveness, the ability to detect meaningful clinical change, is a critical attribute of instruments used to evaluate outcomes of treatments. The authors hypothesized that self-administered symptom severity and functional status questionnaires are more responsive to clinical improvement after carpal tunnel release than traditional physical examination measures of strength and sensibility. Data were obtained from a randomized clinical trial of endoscopic versus open carpal tunnel release conducted in four university medical centers. Patients were evaluated before surgery and 3 months after surgery. Seventy-four patients indicating that they were more than 80% satisfied with the results of surgery were assumed to have clinically meaningful improvement and were the focus of the analysis. Evaluations included questionnaires assessing symptom severity, functional status, and activities of daily living as well as measurement of grip, pinch, and abductor pollicus brevis strength, and 2-point discrimination and Semmes-Weinstein pressure sensibility. Responsiveness was calculated with the standardized response mean (mean change/standard deviation of change) as well as the effect size (mean change/standard deviation of baseline values). The symptom severity scale was four times as responsive, and the functional status and activities of daily living scales were twice as responsive, as the measures of strength and sensibility. Self-administered symptom severity and functional status scales are much more responsive to clinical improvement than measures of neuromuscular impairment and should severe as primary outcomes in clinical studies of therapy for carpal tunnel syndrome. 相似文献
45.
Tripe palms is a cutaneous paraneoplastic syndrome. We report a case of tripe palms in a 71-year-old man with non-small cell lung cancer. Approximately 90% of patients with tripe palms have an associated cancer, most commonly involving the lung or the stomach. Any patient with tripe palms must have a complete cancer workup, especially for lung and stomach cancer. 相似文献
46.
47.
L.P. Hall 《Food microbiology》1985,2(1):31-37
A medium giving maximum indole production colonies of Escherichia coli has been defined and includes diethylaminoethylcellulose which restricts the spread of indole through the agar medium. A reagent based on p-dimethylaminocinnamaldehyde has been developed to give optimum indication of indole production. A simple method which will identify E. coli in cultures obtained from selective media is described and an extension, including a resuscitation stage, devised for rapid and direct quantitation of E. coli from frozen foods. 相似文献
48.
The paper presents a case study of the development of an expert decision support system which uses simple heuristic methods for fast determination of routes for simultaneous signals in a transmission network of limited capacity. It illustrates how heuristic solutions can be embodied in a model-based DSS and how the standard decision support literature, although intuitively appealing, provides little practical assistance in system construction or classification 相似文献
49.
50.
SR Hall 《Canadian Metallurgical Quarterly》1996,21(3):225-229
An asymmetric triazine derivative, HOE 092 V,2-[3,5-alpha-dichloro-4-(4-methyl-sulfonylphenoxy)-phenyl]- 1-methyl-hexahydro-1,2,4-triazine-3,5-dion, was tested in vivo against Glugea anomala parasitizing the connective tissue of sticklebacks (Gasterosteus aculeatus). Naturally infected sticklebacks were incubated in 10-1 plastic aquaria in water containing 0, 2.5, 5, and 10 micrograms HOE 092 V/ml for 2, 3, and 4 h at 22 degrees C. As seen at the ultrastructural level, the drug caused severe damage to all developmental stages of G. anomala except the mature spores. Starting with a dose of 2.5 micrograms/ml, the drug caused significant damage on uni- and multinucleate meronts, sporogonial plasmodia, and sporoblasts. The damage mainly consisted in a decrease in the number of ribosomes, an enlargement of the smooth endoplasmic reticulum and a vacuolization of the cytoplasma. When treatment was done with 5 micrograms for 2 h, multinucleate meronts and sporogonial plasmodia were no longer detectable, and the sporoblasts and the prespore stages except the mature spores had shrunk. After incubation of the infected fish with 10 micrograms HOE 092 V/ml and 4 h exposure, uninucleate meronts were no longer detectable by means of transmission electron microscopy. In the sporoblast mother cells, vacuolization of the cytoplasma and lysis of the nuclei occurred. However, mature spores were not affected. It seems likely that HOE 092 V can be successfully applied in medicinal baths against Microsporidia in fish. The infected fish should be incubated in separate, aerated containers. 相似文献