全文获取类型
收费全文 | 1606篇 |
免费 | 1篇 |
专业分类
综合类 | 52篇 |
化学工业 | 39篇 |
金属工艺 | 1篇 |
机械仪表 | 1篇 |
建筑科学 | 31篇 |
能源动力 | 8篇 |
轻工业 | 10篇 |
水利工程 | 2篇 |
无线电 | 2篇 |
一般工业技术 | 15篇 |
冶金工业 | 1422篇 |
自动化技术 | 24篇 |
出版年
2023年 | 2篇 |
2022年 | 1篇 |
2020年 | 1篇 |
2019年 | 2篇 |
2018年 | 3篇 |
2015年 | 11篇 |
2014年 | 18篇 |
2013年 | 17篇 |
2012年 | 19篇 |
2011年 | 15篇 |
2010年 | 15篇 |
2009年 | 14篇 |
2008年 | 15篇 |
2007年 | 12篇 |
2006年 | 5篇 |
2005年 | 2篇 |
2004年 | 8篇 |
2003年 | 8篇 |
2002年 | 2篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1999年 | 38篇 |
1998年 | 396篇 |
1997年 | 239篇 |
1996年 | 151篇 |
1995年 | 103篇 |
1994年 | 84篇 |
1993年 | 92篇 |
1992年 | 11篇 |
1991年 | 28篇 |
1990年 | 27篇 |
1989年 | 31篇 |
1988年 | 25篇 |
1987年 | 27篇 |
1986年 | 18篇 |
1985年 | 14篇 |
1983年 | 3篇 |
1982年 | 8篇 |
1981年 | 6篇 |
1980年 | 8篇 |
1978年 | 5篇 |
1977年 | 32篇 |
1976年 | 82篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1971年 | 1篇 |
1965年 | 1篇 |
1960年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有1607条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
5.
Recently published studies indicate a potential clinical application of PET in head and neck tumors. In the preoperative staging phase, PET enables confirmation of regional lymph node extension and guides nodal neck dissection or systemic treatment. In this phase, a high negative predictive value, near 100%, could make it possible to avoid many negative neck dissections. This is a reliable technique for confirming or excluding the presence of recurrent/residual tumor and for obtaining an early evaluation of chemotherapeutic and radiotherapeutic response. PET imaging in many cases makes it possible to locate and guide histological study of tumors with an unknown primary. PET imaging for these indications is a perfect complementary method for clinical exploration and better than other imaging techniques. 相似文献
6.
PD Darney 《Canadian Metallurgical Quarterly》1996,14(1):51-61
The abundance of rapid eye movement (REM) sleep in the neonatal mammal and its subsequent decline in the course of development, as well as the dramatic and widespread enhancement of CNS activity during REM sleep, led us to propose that this state plays a functional role in the normative physiological and structural maturation of the brain [54]. When, after 1 week of monocular deprivation (MD), a second week of MD was coupled with behavioral deprivation of REM sleep, the structural alteration in the visual system provoked by MD alone (interlaminar relay cell-size disparity in the lateral geniculate nucleus (LGN) was amplified. With the addition of REM deprivation during MD, the LGN cells connected to the surgically patched eye, which are smaller than normal after MD, became even smaller, whereas the LGN cells receiving input from the seeing eye, which display compensatory hypertrophy after MD, grew even larger. We believe that the interlaminar disparity effect widened because during REM deprivation, the already vision-compromised LGN cells associated with the patched eye also lose the ascending brainstem activation reaching them during the REM state. Loss of the two main sources of 'afference' by these LGN cells permits their seeing-eye LGN counterparts to gain even greater advantage in the competition for synaptic connections in cortex, which is reflected in the relative soma sizes of the LGN relay cells. It is likely that the relatively abundant REM state in early maturation provides symmetric stimulation to all LGN relay cells, irrespective of eye of innervation. The symmetric activation propagated from brainstem to LGN acts to 'buffer' abnormal, asymmetric visual input and, thereby diminishes the extreme, asymmetric structural alteration that results from MD in the absence of REM sleep. We conclude that REM sleep-generated CNS discharge in development has the effect of 'protecting' the CNS against excessive plasticity changes. This is consistent with the possibility that REM sleep plays a role in the genetically programmed processes that direct normative brain development. 相似文献
7.
D Levine PD Barnes S Sher RC Semelka W Li CR McArdle S Worawattanakul RR Edelman 《Canadian Metallurgical Quarterly》1998,206(2):549-554
PURPOSE: To evaluate the normal appearance of fetal anatomy, the conspicuity of fetal organs, the reproducibility of images, and the limitations to image quality with the use of half-Fourier, single-shot rapid acquisition with relaxation enhancement (RARE) magnetic resonance (MR) imaging. MATERIALS AND METHODS: Fifty-four fetuses of 49 pregnancies underwent MR imaging with the half-Fourier, single-shot RARE technique. Two reviewers attempted to identify 47 organs and anatomic regions in each fetus. Organ or region conspicuity, image quality, and the limitations of image quality were graded. RESULTS: Fetal anatomy was well depicted in fetuses over 20 weeks in gestational age. Fetal imaging was limited by gestational age of 20 weeks or less usually owing to the small size of the organ or region being evaluated and, less frequently, by motion. CONCLUSION: Half-Fourier, single-shot RARE MR imaging provided a detailed and reproducible evaluation of normal fetal anatomy, which can be used as a standard of reference in MR imaging of fetal anomalies. 相似文献
8.
9.
10.
Antigen-induced arthritis in guinea pigs was used as a model to investigate the pathogenic mechanisms responsible for cartilage destruction in chronic joint inflammation. The activation of macrophages, their effects on cartilage metabolism, and the development of autoimmunity to cartilage constituents were studied during the progression of arthritis. The results show that in arthritic animals the macrophages are systemically activated, with a peak in the early phase of inflammation. Interleukin 1, produced by the activated cells, suppresses the proteoglycan synthesis in cartilage explants and cultured chondrocytes and increases the proliferation of the cells in vitro. During the progression of arthritis humoral and cell-mediated immune responses to collagen type II and cartilage proteoglycans occur correlating with the severity of arthritis. It is concluded that different immunological mechanisms may be involved in cartilage destruction during antigen-induced arthritis. Mediator-induced metabolic reactions dominate in the early phase, whereas autoimmunity to cartilage might play an essential role in later phases of arthritis. 相似文献