全文获取类型
收费全文 | 1812篇 |
免费 | 36篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 50篇 |
综合类 | 2篇 |
化学工业 | 229篇 |
金属工艺 | 51篇 |
机械仪表 | 24篇 |
建筑科学 | 24篇 |
能源动力 | 26篇 |
轻工业 | 66篇 |
水利工程 | 3篇 |
石油天然气 | 1篇 |
无线电 | 249篇 |
一般工业技术 | 177篇 |
冶金工业 | 822篇 |
原子能技术 | 54篇 |
自动化技术 | 75篇 |
出版年
2023年 | 4篇 |
2022年 | 5篇 |
2021年 | 11篇 |
2020年 | 16篇 |
2019年 | 18篇 |
2018年 | 13篇 |
2017年 | 20篇 |
2016年 | 29篇 |
2015年 | 17篇 |
2014年 | 30篇 |
2013年 | 56篇 |
2012年 | 27篇 |
2011年 | 38篇 |
2010年 | 44篇 |
2009年 | 45篇 |
2008年 | 49篇 |
2007年 | 32篇 |
2006年 | 46篇 |
2005年 | 35篇 |
2004年 | 35篇 |
2003年 | 47篇 |
2002年 | 43篇 |
2001年 | 39篇 |
2000年 | 28篇 |
1999年 | 42篇 |
1998年 | 257篇 |
1997年 | 146篇 |
1996年 | 130篇 |
1995年 | 69篇 |
1994年 | 59篇 |
1993年 | 60篇 |
1992年 | 28篇 |
1991年 | 22篇 |
1990年 | 19篇 |
1989年 | 20篇 |
1988年 | 14篇 |
1987年 | 12篇 |
1986年 | 22篇 |
1985年 | 17篇 |
1984年 | 16篇 |
1983年 | 12篇 |
1982年 | 13篇 |
1981年 | 16篇 |
1980年 | 14篇 |
1979年 | 5篇 |
1978年 | 10篇 |
1977年 | 33篇 |
1976年 | 69篇 |
1975年 | 7篇 |
1972年 | 3篇 |
排序方式: 共有1853条查询结果,搜索用时 562 毫秒
81.
Takami Tohyama Susumu Nagai Yasumasa Shibata Sadamichi Maekawa 《Journal of Low Temperature Physics》1999,117(3-4):211-215
We investigate the electronic states of underdoped La
2–x
Sr
x
CuO
4
(LSCO) by using a microscopic model, i.e., t-t-t-J model, containing charge stripes. The numerically exact diagonalization calculation is employed on small clusters. The physical properties observed in the angle-resolved photoemission and optical conductivity experiments are consistently explained in the model with vertical stripes, but not diagonal ones. These results demonstrate a crucial role of the vertical stripes in underdoped LSCO. 相似文献
82.
K Sakizono T Oita Y Shibata A Tamura S Kasakura 《Canadian Metallurgical Quarterly》1998,46(9):936-941
PIVKA-II is well known as a tumor maker of hepatocellular carcinoma (HCC). We measured serum PIVKA-II concentrations with a commercially available PIVKA-II immunoassay kit (Picolumi PIVKA-II: Eisai Co., Ltd., Tokyo) using Electrochemiluminescence Immunoassay (ECLIA). ECLIA system is a novel immunoassay system using a Ruthenium (II) Tris (bipyridyl) luminesced by electric energy. Cut off value was 40 mAU/ml by receiver-operating characteristic curves as a tumor maker for HCC. Eighty-nine out of 142 (62.2%) patients with HCC had elevated serum PIVKA-II levels and seventeen out of 36 (47.2%) patients whose tumor size was below 2 cm in diameter showed high PIVKA-II levels. We determined the serial changes in serum PIVKA-II levels of two patients with HCC following initial therapy. In these patients, elevations of serum PIVKA-II levels determined by ECLIA system preceded the HCC relapse detected by imaging diagnostic procedures. In summary, this assay system is suitable for detecting small increases in PIVKA-II concentrations. Determination of PIVKA-II by this assay system is found to be useful for the early detection of HCC. 相似文献
83.
We describe a method in which constant infusion inflow through an anterior chamber maintainer (ACM) is used to maintain positive intraocular pressure (IOP) during cataract extraction through a self-sealing tunnel incision. A retrospective review of patient records showed that the difference in the incidence of intraoperative suprachoroidal hemorrhage was significantly greater in eyes in which IOP was not constant throughout surgery than in eyes in which IOP was maintained using the ACM system. 相似文献
84.
Fukushima T. Matsumoto N. Nakayama H. Ikegami Y. Namegaya T. Kasukawa A. Shibata M. 《Photonics Technology Letters, IEEE》1993,5(9):963-965
Compressively strained 1.3-μm GaInAsP/InP multiple-quantum-well (MQW) ridge waveguide lasers were fabricated. Through optimizing the total well thickness, large bandwidth over 11 GHz was achieved, together with high quantum efficiency of about 0.48 W/A and high power output of 60 mW before rollover. The laser also showed less temperature sensitivity up to an elevated temperature of 85°C 相似文献
85.
C García Rodríguez DR Cundell EI Tuomanen LF Kolakowski C Gerard NP Gerard 《Canadian Metallurgical Quarterly》1995,270(42):25178-25184
Streptococcus pneumoniae has been shown to utilize the platelet activating factor receptor for binding and invasion of host cells (Cundell, D. R., Gerard, N. P., Gerard, C., Idanpaan-Heikkila, I., and Tuomanen, E. I. (1995) Nature, in press). Because bacterial binding is in part carbohydrate dependent, and the human platelet-activating factor (PAF) receptor bears a single N-linked glycosylation sequence in the second extracellular loop, we undertook studies to determine the role of this epitope in PAF receptor function. Binding of pneumococci to COS cells transfected with the human PAF receptor is greatly reduced for a receptor mutant that bears no N-linked glycosylation site. Immunohistochemical and binding analyses show decreased expression of the non-glycosylated molecule on the cell membrane relative to the wild type receptor; however, metabolic labeling and immunopurification indicate it is synthesized intracellularly at a level similar to the native molecule. A mutant receptor encoding a functional glycosylation site at the NH2 terminus is better expressed at the cell surface compared with the non-glycosylated form, indicating that trafficking to the cell surface is facilitated by glycosylation, but its location is relatively unimportant. The binding affinity for PAF is not significantly effected by the presence or location of the carbohydrate, and variations in cell surface expression have little influence on signal transduction, as the non-glycosylated PAF receptor is equally effective for activation of phospholipase C as the native molecule. These data are supportive of pneumococcal binding on protein moiety(ies) of the PAF receptor and indicate that N-glycosylation facilitates expression of the protein on the cell membrane. 相似文献
86.
MJ Bettencourt BG Pinto EI de Oliveira LS Carvalho JS Carvalho 《Canadian Metallurgical Quarterly》1998,17(11):875-879
OBJECTIVE: Autonomic modulation of hemodynamics, essential for the preservation of homeostasis, is well tested by the abrupt postural change from clinostatism to active orthostatism. The aim of this work was to study normal relationships between the cardiovascular variables in active orthostatism and those in clinostatism. METHODS: Hemodynamic parameters in clinostatism and orthostatism were easily measured in 20 healthy subjects of both sexes, aged between 33 and 78 years, without treatment, using the non-invasive thoracic electric bioimpedance method. RESULTS: Cardiovascular variables values in orthostatism are linearly related with their values in clinostatism. CONCLUSIONS: Results show that cardiovascular variables in active orthostatism are linearly related with their values in clinostatism, each variable being specially regulated. A clinostatism and orthostatism intraindividual correlation was obtained, which provides an easily accessible method of detection and interpretation of autonomic dysfunctions, without deleterious consequences for the subjects, which can be very useful for research on physiopathologic mechanisms. 相似文献
87.
GA Kosmiadi ZP Abramova TV Vaneeva NM Fomina VIa Gergert EI Shmelev 《Canadian Metallurgical Quarterly》1996,41(4):51-53
The effect of various concentrations of ofloxacin, ciprofloxacin and lomefloxacin on the morphokinetic parameters of the cellular elements of the lung tissue of intact animals (mice, guinea pigs and dogs) was studied under the conditions of the tissue culture. It was shown that in a concentration of 100 micrograms/ml and the exposure time of 24 hours the drugs had no effect on the mobility and structure of the lung tissue cellular elements. When the drugs were used in a concentration of 100 micrograms/ml the mobility rate of the lymphocytes and macrophages proved to by markedly retarded by the end of the 24th hour. In a concentration of 1000 micrograms/ml the drugs killed the cell culture. There were detected no specific differences in the effect of the fluoroquinolones on the cellular elements of the lung tissue of the intact animals. 相似文献
88.
An algorythm of differential diagnosis conduction of the transplant rejection reaction and the diseases caused by herpes viruses in recipients after the kidney transplantation was elaborated, basing on the analysis of results of the clinical, laboratory, immunological and serological examination methods. 相似文献
89.
90.
K Hayashi N Takahashi S Furuichi T Yoshioka S Shibata 《Canadian Metallurgical Quarterly》1998,26(12):1103-1107
Two cases of aneurysm incidentally detected after recanalization of middle cerebral artery (MCA) occlusion are reported. Patient 1 was a 62-year-old male with sudden onset of left hemiparesis. We performed emergent intravascular surgery. The initial cerebral angiography revealed occlusion at the M1 portion of the right MCA. After partial recanalization with a microcatheter, carotid angiography revealed a right M1-M2 junction aneurysm. Due to the risk of aneurysmal rupture, the thrombolytic procedure was stopped. Follow up angiography after 1 month revealed complete recanalization of the right MCA and a persistent aneurysm. Patient 2 was a 65-year-old male with left hemiparesis. The initial cerebral angiography revealed occlusion at the M1 portion of the right MCA. After 1 month follow-up cerebral angiography revealed spontaneous recanalization of the right MCA and an incidental aneurysm at the M1-M2 junction. Neck clipping of the aneurysm was performed. When using a microcatheter or microballoon catheter to treat arterial occlusion, surgeons should consider the possibility of a rupture of a hidden aneurysm. 相似文献