首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1282篇
  免费   28篇
  国内免费   1篇
电工技术   99篇
综合类   3篇
化学工业   372篇
金属工艺   28篇
机械仪表   42篇
建筑科学   15篇
能源动力   185篇
轻工业   86篇
石油天然气   1篇
无线电   83篇
一般工业技术   168篇
冶金工业   137篇
原子能技术   25篇
自动化技术   67篇
  2023年   2篇
  2022年   6篇
  2021年   18篇
  2020年   6篇
  2019年   15篇
  2018年   14篇
  2017年   14篇
  2016年   24篇
  2015年   16篇
  2014年   36篇
  2013年   66篇
  2012年   38篇
  2011年   79篇
  2010年   50篇
  2009年   52篇
  2008年   63篇
  2007年   56篇
  2006年   41篇
  2005年   44篇
  2004年   48篇
  2003年   52篇
  2002年   37篇
  2001年   21篇
  2000年   25篇
  1999年   23篇
  1998年   76篇
  1997年   52篇
  1996年   46篇
  1995年   25篇
  1994年   28篇
  1993年   25篇
  1992年   12篇
  1991年   11篇
  1990年   15篇
  1989年   8篇
  1988年   13篇
  1987年   12篇
  1986年   17篇
  1985年   18篇
  1984年   10篇
  1983年   16篇
  1982年   18篇
  1981年   12篇
  1980年   6篇
  1979年   10篇
  1978年   13篇
  1977年   9篇
  1976年   8篇
  1975年   3篇
  1971年   1篇
排序方式: 共有1311条查询结果,搜索用时 15 毫秒
1.
Monitoring the temperature in liquid hydrogen (LH2) storage tanks on ships is important for the safety of maritime navigation. In addition, accurate temperature measurement is also required for commercial transactions. Temperature and pressure define the density of liquid hydrogen, which is directly linked to trading interests. In this study, we developed and tested a liquid hydrogen temperature monitoring system that uses platinum resistance sensors with a nominal electrical resistance of approximately 1000 Ω at room temperature, PT-1000, for marine applications. The temperature measurements were carried out using a newly developed temperature monitoring system under different pressure conditions. The measured values are compared with a calibrated reference PT-1000 resistance thermometer. We confirm a measurement accuracy of ±50 mK in a pressure range of 0.1 MPa–0.5 MPa.  相似文献   
2.
Some reports demonstrated successful genome editing in pigs by one-step zygote microinjection of mRNA of CRISPR/Cas9-related components. Given the relatively long gestation periods and the high cost of housing, the establishment of a single blastocyst-based assay for rapid optimization of the above system is required. As a proof-of-concept, we attempted to disrupt a gene (GGTA1) encoding the α-1,3-galactosyltransferase that synthesizes the α-Gal epitope using parthenogenetically activated porcine oocytes. The lack of α-Gal epitope expression can be monitored by staining with fluorescently labeled isolectin BS-I-B4 (IB4), which binds specifically to the α-Gal epitope. When oocytes were injected with guide RNA specific to GGTA1 together with enhanced green fluorescent protein (EGFP) and human Cas9 mRNAs, 65% (24/37) of the developing blastocysts exhibited green fluorescence, although almost all (96%, 23/24) showed a mosaic fluorescent pattern. Staining with IB4 revealed that the green fluorescent area often had a reduced binding activity to IB4. Of the 16 samples tested, six (five fluorescent and one non-fluorescent blastocysts) had indel mutations, suggesting a correlation between EGFP expression and mutation induction. Furthermore, it is suggested that zygote microinjection of mRNAs might lead to the production of piglets with cells harboring various mutation types.  相似文献   
3.
This paper describes the dielectric breakdown characteristics of oil and oil‐impregnated paper for very fast transient (VFT) voltages. Blumlein circuits generate VFT voltages of 60 and 300 ns in a pulse width that simulates disconnecting switching surges in gas‐insulated switch gears. We measured the breakdown voltages of needle‐to‐plane, plane‐to‐plane oil gaps and several pieces of paper between plane electrodes for VFT and lightning impulse voltages. The measured data were formulated in V‐t characteristics and Weibull probability distributions. The inclination n of V‐t characteristics of insulating paper is 150, which is less than n = 13.7 of the plane‐to‐plane oil gap in the VFT time range. The shape parameters of Weibull distribution obtained in this study show that the scattering of breakdown voltages of paper is much less than that of oil. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 141(4): 16–24, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10043  相似文献   
4.
The copreheat-treatment of non-fusible and slightly fusible coals with A240 and hydrogenated A240 under high temperature-short contact-time conditions around 500 °C has been examined in an attempt to produce a formed coke with better anisotropic development. These conditions shortened the copreheat-treatment time and provided better anisotropic development in the resultant coke after carbonization. Effectiveness of short contact-time has been discussed in terms of the extent of depolymerization of coal molecules suitable for anisotropic development, this being related to coal liquefaction under similar conditions.  相似文献   
5.
We succeeded in observing the continuously tunable, pulsed InSb SFR (Spin-Flip Raman) laser emission in the infrared region of 11~16µm (11.4~16.3µm) from only one InSb device, merely by adjusting the pumping wavelength (11 lines from the infrared NH3 laser) and the applied magnetic field (0~80 kGauss).  相似文献   
6.
The nature of the events whereby the reactive intermediates resulting from the bioactivation of bromobenzene and furosemide induce hepatotoxicity is unknown. To examine a role for disturbances in intracellular calcium homeostasis, secondary to a depletion in cellular reduced glutathione (GSH) and reduced protein thiols (PSHs), isolated mouse hepatocytes were exposed to cytotoxic concentrations of bromobenzene or furosemide. Cytosolic calcium concentration, as well as thiol status, was determined. The incubation of hepatocytes with 3.0 mM bromobenzene, and subsequent additions (1.2 mM) of the agent every hour, resulted in significant GSH depletion. The loss of plasma membrane integrity at 1.5 h preceded both a rise in the cytosolic Ca2+ concentration and depletion of total PSH content. Furosemide (1.0 mM) produced a 70% depletion in cellular GSH content in isolated hepatocytes. The initiation of cell damage occurred concurrently with both a rise in the cytosolic Ca2+ concentration and a depletion of total PSH content 4 h following furosemide addition. Since the increase in cytosolic Ca2+ did not precede cytotoxicity, these results do not support an initiating role for Ca2+ deregulation in bromobenzene and furosemide hepatotoxicities. In addition, depletion of PSH content did not correlate with bromobenzene- or furosemide-induced cytotoxicity.  相似文献   
7.
The effects of particle size and food on the absolute bioavailability of U-78875 in dogs after oral administration of either a suspension or tablet dosage form were investigated. A reduction of particle size caused a significant increase in bioavailability along with an increase in dissolution rate. Additionally, both suspension and tablet dosage forms administered after food caused an increase in bioavailability. Thus, to accelerate drug dissolution, a reduction of U-78875 particle size from the unmilled state is important for the optimization of formulation compositions. To increase the bioavailability of U-78875, postprandial dosing should be considered.  相似文献   
8.
In this study, current collecting efficiency of the micro tubular solid oxide fuel cell (SOFC) was estimated to determine optimum size of the micro tubular SOFC. Two models for collecting current from single terminal (ST) and double terminal (DT) of anode tube were proposed and used to calculate the current collecting efficiency as functions of anode thickness, tube length and operating temperature. It was shown that design of the cell geometry and current correcting method are significantly important to achieve high performance micro tubular SOFC stacks. The efficiency loss estimated from the DT model was about 2–4-fold lower than those of obtained from the ST model. The DT model was shown to be more effective for higher operating temperature and the tube length.  相似文献   
9.
Using in situ hybridization techniques, we examined the expression of ornithine decarboxylase (ODC) mRNA in the skin of five patients with systemic sclerosis (SSc) and five normal controls. Sections treated with an anti-sense probe showed concentrated grains exclusively in the epidermis of SSc patients, but not in that of normal controls. Because our subcloned anti-sense probe specifically hybridizes with ODC mRNA, these findings indicate that the expression of ODC mRNA is elevated in SSc epidermis. Possibly polyamines have an important part to play in the skin changes of SSc.  相似文献   
10.
In this paper, we propose that the urinary toxins from the wastewater be adsorbed on an adsorbent such as spherical activated carbon and the latter be regenerated by subjecting it to high temperatures to recycle activated carbon and also to recycle the water used in dialysis. We studied the adsorption of artificial waste dialysate, which is a mixed solution of urea, creatinine, and uric acid, and the separate solutions for each of these and found that their extents of adsorption onto the spherical activated carbon material were nearly identical. The amount of adsorption was approximately 1.4 mg·g-1 for urea, 18 mg·g-1 for creatinine, and 20 mg·g-1 for uric acid. The urea, creatinine, and uric acid adsorbed onto the spherical activated carbon decomposed on heat treatment at 500℃, and the adsorption capacity of the spherical activated carbon was regenerated. Our study successfully demonstrated that the spherical activated carbon can be recycled in the waste dialysate treatment process.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号