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   924篇
  免费   25篇
  国内免费   1篇
电工技术   81篇
综合类   3篇
化学工业   282篇
金属工艺   23篇
机械仪表   40篇
建筑科学   13篇
能源动力   170篇
轻工业   75篇
石油天然气   1篇
无线电   42篇
一般工业技术   120篇
冶金工业   33篇
原子能技术   15篇
自动化技术   52篇
  2022年   5篇
  2021年   13篇
  2020年   4篇
  2019年   10篇
  2018年   14篇
  2017年   15篇
  2016年   22篇
  2015年   13篇
  2014年   29篇
  2013年   55篇
  2012年   35篇
  2011年   65篇
  2010年   46篇
  2009年   43篇
  2008年   55篇
  2007年   51篇
  2006年   39篇
  2005年   38篇
  2004年   43篇
  2003年   46篇
  2002年   34篇
  2001年   10篇
  2000年   21篇
  1999年   19篇
  1998年   35篇
  1997年   20篇
  1996年   24篇
  1995年   13篇
  1994年   13篇
  1993年   12篇
  1992年   7篇
  1991年   6篇
  1990年   8篇
  1989年   5篇
  1988年   6篇
  1987年   2篇
  1986年   7篇
  1985年   12篇
  1984年   3篇
  1983年   5篇
  1982年   7篇
  1981年   5篇
  1980年   4篇
  1979年   7篇
  1978年   9篇
  1977年   4篇
  1976年   5篇
  1975年   3篇
  1971年   1篇
  1959年   1篇
排序方式: 共有950条查询结果,搜索用时 312 毫秒
1.
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   
2.
OBJECTIVE: To better understand the immunoglobulin variable (V) region repertoire of rheumatoid factors (RF). METHODS: We characterized the heavy (H) and light (L) chain gene segments utilized in a monospecific IgG RF secreting hybridoma (AEE111F) which were derived from a patient with rheumatoid arthritis (RA). The hybridoma was established by fusion of a mouse myeloma cell line with bone marrow derived mononuclear cells from a patient with RA. First strand complementary DNA (cDNA) was generated and used for a polymerase chain reaction amplification of the H and L chain V domains. The amplified V domains were sequenced and compared with an extensive database of germline and cDNA V gene segments. RESULTS: The VH sequence was found to be 96% homologous to a previously described fetal VH3 cDNA (60P2). The VL sequence was also highly homologous to the previously described V lambda II gene (96%) derived from a patient with systemic lupus erythematosus which correlated with an 8.12 idiotype (Id), and to an antibacterial antibody against the Haemophilus influenzae type b capsular polysaccharide (94.7%). CONCLUSION: The overlap among this RF VL gene and the 2 reported V lambda sequences of antibodies that expressed anti-DNA related Id and an environmental pathogen specificity suggests that a part of the IgG RF isolated from patients with RA may thus be derived from the physiological natural antibody repertoire during an abnormal immune response and then develop high affinity, monospecific RF by the selection of an antigen driven mechanism.  相似文献   
3.
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   
4.
5.
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   
6.
BACKGROUND/AIMS: Liver cancer extension to the adjacent organs does not necessarily indicate tumor invasion. It is very hard to diagnose extrahepatic cancer invasion to the adjacent organs using preoperative imaging. This study was undertaken, therefore, to determine the real cancer invasion using a manual dissection. METHODOLOGY: Of the 51 consecutive patients with liver cancer, 6 cases with extrahepatically growing tumors were suspected to have cancer invasion both preoperatively and intraoperatively. Thus, we diagnosed whether or not any real extrahepatic cancer invasion was present by either removing the tumour by hand or by performing a blunt gauze dissection. RESULTS: Three hepatocellular carcinomas and one metastatic cancer were stripped off from the adjacent organ using a manual blunt dissection. However, the other two tumors could not be removed in the same manner and therefore a combined resection of the invaded portion had to be performed along with the hepatectomy. A postoperative detailed pathological examination revealed no cancer cells on the surface of the adjacent organ in the former 4 tumors. Cancer invasion was recognized, however, on the outside of the liver in the latter 2 combined resected tumors. CONCLUSIONS: An accurate intraoperative diagnosis of extrahepatic cancer invasion can be made using manual blunt dissection.  相似文献   
7.
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   
8.
A high-performance liquid chromatographic method, using post-column detection with diphenyl-1-pyrenyl-phosphine (DPPP), was developed for the quantitative and qualitative determination of isomeric lipid hydroperoxides (OOH). The OOH eluted from a normal-phase column were passed through a photodiode array detector and then mixed with DPPP solution in a reaction coil heated at 80°C. DPPP oxide formed by the reaction with OOH was determined by monitoring the fluorescence intensity at 380 nm and excitation at 352 nm. The conjugated diene OOH (13-cis, trans- and 9-cis, trans-OOH) and nonconjugated OOH (12-cis-trans- and 10-cis, trans-OOH) from photosensitized oxidation of methyl linoleate were determined in a molar ratio of 31∶29∶19∶21, respectively. However, only the two conjugated hydroperoxides were detected by ultraviolet absorption at 234 nm. Further applications were carried out for the determination of OOH of methyl oleate and methyl linolenate. This method proved to be useful for the determination of the OOH containing both conjugated and nonconjugated diene structures.  相似文献   
9.
The miscibility of poly(methyl methacrylate) (PMMA) and styrene-acrylonitrile random copolymers (SAN) blends was investigated on the basis of the Flory—Orwoll—Vrij equation of state theory. To obtain the equation of state parameters (P*, V*sp, T*: characteristic parameters), the pressure—volume—temperature (PVT) behaviour was measured for PMMA and a series of SANs with various acrylonitrile contents. The exchange energy parameter Xij was also calculated by fitting the theory to some phase diagrams of PMMA/SAN blends. The Flory—Huggins interaction parameter χ was separated into two contributions based on the equation of state theory for mixtures: the exchange energy term χinter and the free volume term χfree. Both the temperature and copolymer composition dependences of χinter and χfree were estimated by calculations using the equation of state parameters. There exists a region in which χinter is negative, leading to a miscibility window in PMMA/SAN blends. However, the immiscibility at high temperatures in the blends cannot be explained only by χinter; it is caused by the free volume contribution, χfree. The miscibility window behaviour in PMMA/SAN blends may be explained within the framework of the equation of state theory.  相似文献   
10.
Amorphous CeO2–ZrO2 gels were prepared by coprecipitation in ammonia solutions. The onset of crystallization of the gels, from calcining in air, was 420°C, while 200° to 250°C in the presence of water and organic solvents such as methanol and ethanol. The sintering behaviors of CeO2–ZrO2 powders were sensitive to the crystallizing conditions, since hard agglomerates formed when the precipitated gels were crystallized by normal calcination in air, whereas soft agglomerates formed when they were crystallized in water or organic solvents. CeO2–ZrO2 powders crystallized in methanol and water at 250°C were sintered to full theoretical density at 1150° and 1400°C, respectively, whereas that crystallized by calcination in air at 450°C was sintered to only 95.2% of theoretical density, even at 1500°C.  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