全文获取类型
收费全文 | 4104篇 |
免费 | 231篇 |
国内免费 | 12篇 |
专业分类
电工技术 | 37篇 |
综合类 | 2篇 |
化学工业 | 797篇 |
金属工艺 | 179篇 |
机械仪表 | 198篇 |
建筑科学 | 49篇 |
矿业工程 | 3篇 |
能源动力 | 170篇 |
轻工业 | 307篇 |
水利工程 | 5篇 |
石油天然气 | 10篇 |
无线电 | 527篇 |
一般工业技术 | 719篇 |
冶金工业 | 955篇 |
原子能技术 | 39篇 |
自动化技术 | 350篇 |
出版年
2024年 | 5篇 |
2023年 | 58篇 |
2022年 | 81篇 |
2021年 | 122篇 |
2020年 | 91篇 |
2019年 | 88篇 |
2018年 | 125篇 |
2017年 | 113篇 |
2016年 | 129篇 |
2015年 | 87篇 |
2014年 | 141篇 |
2013年 | 189篇 |
2012年 | 256篇 |
2011年 | 307篇 |
2010年 | 196篇 |
2009年 | 183篇 |
2008年 | 163篇 |
2007年 | 135篇 |
2006年 | 123篇 |
2005年 | 97篇 |
2004年 | 97篇 |
2003年 | 91篇 |
2002年 | 91篇 |
2001年 | 69篇 |
2000年 | 64篇 |
1999年 | 88篇 |
1998年 | 290篇 |
1997年 | 194篇 |
1996年 | 138篇 |
1995年 | 98篇 |
1994年 | 66篇 |
1993年 | 68篇 |
1992年 | 21篇 |
1991年 | 14篇 |
1990年 | 13篇 |
1989年 | 17篇 |
1988年 | 23篇 |
1987年 | 24篇 |
1986年 | 25篇 |
1985年 | 19篇 |
1984年 | 12篇 |
1983年 | 6篇 |
1982年 | 9篇 |
1981年 | 11篇 |
1980年 | 16篇 |
1979年 | 4篇 |
1978年 | 3篇 |
1977年 | 23篇 |
1976年 | 56篇 |
1967年 | 2篇 |
排序方式: 共有4347条查询结果,搜索用时 15 毫秒
31.
SJ McPherson RN Gibson NA Collier TG Speer ND Sherson 《Canadian Metallurgical Quarterly》1998,206(3):665-672
Ancylostoma duodenale is still the dominant hookworm species in the Mediterranean area, India, China and Japan. In the present study, biopsied materials were taken from the small intestine of 30 patients infected only with A. duodenale and 12 cross matched controls. The results showed some pathological changes in severely infected cases. However, normal or insignificant changes were seen in the enzymatic activity of the intestinal mucosa. 相似文献
32.
RS Veazey DW Horohov JL Krahenbuhl HW Taylor JL Oliver TG Snider 《Canadian Metallurgical Quarterly》1995,47(1-2):79-87
Susceptibility of C57BL/6 (Bcgs) and C3H/HeN (Bcgr) mice to an intraperitoneal infection with Mycobacterium paratuberculosis strain 19698 was compared (by histopathology and the number of mycobacteria isolated from the spleen). Mycobacterial counts from the spleen of Bcgr mice progressively decreased over the course of infection but remained unchanged in Bcgs mice. Granulomatous lesions and acid-fast bacteria were consistently present in the liver and lymph nodes of Bcgs mice, whereas lesions were transient or absent in Bcgr mice. These results indicate that Bcgr mice are inherently resistant to M. paratuberculosis, whereas Bcgs mice are inherently susceptible. These differences may prove useful in elucidating the mechanisms of resistance and susceptibility to paratuberculosis and other mycobacterial infections. 相似文献
33.
A comparison was made of the outcome of 73 neonates born with their birth weight of 500-999 gm in National Taiwan University Hospital during the period between January 1, 1993 and December 31, 1996 (Period II), with the outcome of 21 such neonates born between April 1, 1988 and October 31, 1992 (Period I). Exclusion criteria included parental refusal for resuscitation, and major anomalies. Data were collected via a predetermined record sheet. The incidences of the extremely-low-birth-weight infants were 23/10,173 (0.23%) and 81/13,835 (0.59%) in Periods I and II, respectively. Early neonatal mortality rate was significant decreased in Period II (43% versus 14%). The limit of viability was improved from gestational age of 26 weeks or 700 gm to gestational age of 24 weeks or 600 gm. The incidence of neonatal morbidity (80% versus 50%) and total survival rate (48% versus 60%) have not changed significantly as seen in this limited number of cases. This study concluded that, with the introduction of exogenous surfactant and modern neonatal care, early neonatal survival rate and the limit of viability were improved. 相似文献
34.
RE Schrohenloher WJ Koopman TG Woodworth LW Moreland 《Canadian Metallurgical Quarterly》1996,23(11):1845-1848
OBJECTIVE: To investigate the effect of diphtheria toxin interleukin 2 recombinant fusion protein (DAB 486IL-2) on in vitro synthesis of immunoglobulin and rheumatoid factor (RF) in patients with severe refractory rheumatoid arthritis (RA) enrolled in a phase II, double blind, placebo controlled study. METHODS: Anticoagulated venous blood samples were obtained before (Day 1) and after (Day 28) intravenous infusion of either DAB 486IL-2 at 0.075 mg/kg/day (12 patients) or saline placebo (10 patients) on Days 1-5. Peripheral blood leukocytes (PBL) were prepared by density gradient centrifugation, cultured in the presence and absence of pokeweed mitogen (PWM) for one week, and culture supernatants assayed for immunoglobulins and IgM RF by ELISA. RESULTS: Compared to placebo treated patients, PWM induced IgM RF synthesis by PBL decreased after treatment with DAB 486IL-2 (p = 0.043). However, there was no apparent correlation with clinical improvement. PWM induced IgM, IgA, and IgG synthesis also tended to decrease, although the changes did not attain statistical significance. In contrast, PWM induced IgM RF, IgM, IgA, and IgG synthesis by PBL from patients treated with placebo tended to increase during the observation period. Spontaneous immunoglobulin and IgM RF production by PBL from either the DAB 486IL-2 or placebo patients remained stable. CONCLUSION: These observations raise the possibility that DAB 486IL-2 may diminish B cell function either directly or indirectly through effects on T cell function, but the change may not correspond to clinical response. 相似文献
35.
TG Evans W Bonnez HR Soucier T Fitzgerald DC Gibbons RC Reichman 《Canadian Metallurgical Quarterly》1998,39(3):163-173
Criteria for detection of chromosome aberrations by Comparative Genomic Hybridization (CGH) are not standardized and improvement of this part of the analysis is of paramount importance to the applicability of the technique. The aim of this work was to suggest CGH detection criteria that increase the specificity and sensitivity and at the same time include chromosome regions previously excluded from CGH analysis. We analyzed 33 hybridizations with normal DNA and modified our CGH software in order to use a selection of these normal analyses as a model for interpretation of analyses of unknown samples. This approach was successfully tested on 14 samples with known aberrations. 相似文献
36.
Abbass Mohammed Y. Kwon Ki-Chul Kim Nam Abdelwahab Safey A. El-Samie Fathi E. Abd Khalaf Ashraf A. M. 《Artificial Intelligence Review》2021,54(5):3349-3360
Artificial Intelligence Review - Visual object tracking has become one of the most active research topics in computer vision, and it has been applied in several commercial... 相似文献
37.
Jung Nam Bae Jin Young Kim Geon Kim Yong Tae Lee Jae Sang Cha 《Multimedia Tools and Applications》2012,57(2):359-372
Recently, watermarking based data transmission techniques using terrestrial digital TV signal have been proposed since they
are also cost-free and can overcome the limitations of GPS. However, in the previous watermarking based methods, the detection
accuracy is low and additional data rate is too low. Thus, we propose the throughput enhancement method by employing the TZCD-MBOK
watermarking technique in T-DMB system. By applying the proposed scheme to T-DMB, it allows additional data transmission for
disaster broadcasting and improves efficiency of data transmission in shadow region and indoor to mobile environment through
watermarking spread code. From the simulation results, we confirm the proposed watermarking scheme affected on the existing
T-DMB signal. Moreover, it was also confirmed that the system capacity increases as the power of additional watermarking signal
rose. The results of the paper can be applied to wireless multimedia digital broadcasting systems. 相似文献
38.
Namhun Lee Se-Jong Oh Jang-Woo Park Kyung-Rok Nam Kyung-Jun Kang Kyo-Chul Lee Yong-Jin Lee June-Seek Choi Jeong-Ho Seok Jae-Yong Choi 《International journal of molecular sciences》2021,22(5)
Early life stress (ELS) is strongly associated with psychiatric disorders such as anxiety, depression, and schizophrenia in adulthood. To date, biological, behavioral, and structural aspects of ELS have been studied extensively, but their functional effects remain unclear. Here, we examined NeuroPET studies of dopaminergic, glutamatergic, and serotonergic systems in ELS animal models. Maternal separation and restraint stress were used to generate single or complex developmental trauma. Body weights of animals exposed to single trauma were similar to those of control animals; however, animals exposed to complex trauma exhibited loss of body weight when compared to controls. In behavioral tests, the complex developmental trauma group exhibited a decrease in time spent in the open arm of the elevated plus-maze and an increase in immobility time in the forced swim test when compared to control animals. In NeuroPET studies, the complex trauma group displayed a reduction in brain uptake values when compared to single trauma and control groups. Of neurotransmitter systems analyzed, the rate of decrease in brain uptake was the highest in the serotonergic group. Collectively, our results indicate that developmental trauma events induce behavioral deficits, including anxiety- and depressive-like phenotypes and dysfunction in neurotransmitter systems. 相似文献
39.
40.