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   238篇
  免费   2篇
电工技术   25篇
化学工业   28篇
金属工艺   3篇
机械仪表   7篇
能源动力   4篇
轻工业   17篇
无线电   13篇
一般工业技术   44篇
冶金工业   87篇
原子能技术   3篇
自动化技术   9篇
  2022年   4篇
  2021年   5篇
  2020年   1篇
  2017年   2篇
  2016年   5篇
  2013年   5篇
  2012年   3篇
  2011年   8篇
  2010年   3篇
  2009年   5篇
  2008年   6篇
  2007年   6篇
  2006年   6篇
  2005年   9篇
  2004年   5篇
  2003年   10篇
  2002年   6篇
  2001年   6篇
  2000年   5篇
  1999年   9篇
  1998年   41篇
  1997年   22篇
  1996年   8篇
  1995年   6篇
  1994年   9篇
  1993年   5篇
  1992年   4篇
  1991年   4篇
  1990年   2篇
  1989年   1篇
  1988年   5篇
  1987年   1篇
  1986年   1篇
  1985年   1篇
  1984年   1篇
  1983年   2篇
  1982年   3篇
  1981年   2篇
  1980年   3篇
  1979年   3篇
  1978年   2篇
  1976年   1篇
  1974年   2篇
  1973年   1篇
  1972年   1篇
排序方式: 共有240条查询结果,搜索用时 0 毫秒
81.
Recombinant RNase LE from tomato and squid liver RNase Tp, typical plant/animal type RNases belonging to the RNase T2 family, were subjected to limited digestion with several proteases, and the cleavage sites were analyzed by Edman degradation. Recombinant RNase LE was cleaved specifically at the 24th Lys by lysylendopeptidase and trypsin, and RNase Tp was cleaved at the 21st Glu by V8 protease. These cleavage sites are located very close to those where the cleavage during preparation of several animal RNase T2 family enzymes was observed. From this finding, it was concluded that the short segment around the 20th amino acid residue in plant/animal RNases is located on the surface of the molecules and forms loops, and is thus very sensitive to proteases.  相似文献   
82.
A study of the clinical, radiological, and pathological correlations in 43 patients with solitary cysticercus granuloma and epilepsy focused on factors that might help in predicting the presence of the parasite in the granuloma and those that might influence the formation of oedema around the granuloma. The duration of symptoms (< six months and > or = six months) and CT morphology of the granuloma (ring and disc, type A; nodular lesion, type B) were studied as factors that could possibly predict the presence of the parasite in the granuloma. The influence of sex of the patient and the presence of a neutrophilic response in the granuloma on the intensity of oedema around the lesion as seen on CT was also studied. The pathological features were studied in the excised granulomas. The intact or degenerated form of the cysticercus was evident in 22 of 43 specimens. Neither the duration of seizures (P = 0.17) nor the type of lesion on CT (P = 0.16) was predictive of the presence of the parasite in the granuloma. The sex of the patient (P = 0.51) and the neutrophilic response in the specimen (P = 0.73) did not correlate with the degree of oedema on CT indicating that neither of these host factors was a major determinant of oedema production. The findings point to the varied and unpredictable natural history of solitary cysticercus granulomas and the complex nature of host-parasite interactions in individual patients. The inability to predict the presence of the parasite in the granuloma on the basis of the clinical or radiological features precludes a selection of patients with such lesions for cysticidal drug treatment.  相似文献   
83.
MARS14 Monte Carlo simulations were performed for collimation and shielding studies of the J-PARC 3 GeV synchrotron ring. The beam line module locations in the 348.3 m ring and the curved tunnel sections were described by the 'MAD-MARS beam line builder' tool. A 400 MeV proton beam loss distribution, calculated with the STRUCT code, was used as a 4 kW source term in the collimator region, with 1 kW source terms in the injection and extraction regions at 400 MeV and 3 GeV, respectively. Deep penetration calculations were carried out with good statistics using a newly developed three-dimensional multi-layer technique. Prompt dose-rate distributions were calculated inside and outside the concrete and soil shield up to the ground level. Using the calculation results obtained thus, an effective shielding design was made.  相似文献   
84.
A scanning critical illumination system is designed to couple a synchrotron radiation source to a three-aspherical-mirror imaging system for extreme ultraviolet lithography. A static illumination area of H x V = 8 mm x 3 mm (where H is horizontal and V is vertical) can be obtained. Uniform intensity distribution and a large ring field of H x V = 150 mm x 3 mm can be achieved by scanning of the mirror of the condenser. The coherence factor (varsigma) of this illumination system is ~0.6, with the same beam divergence in both the horizontal and the vertical directions. We describe the performance of the imaging optics at varsigma = 0.6 to confirm that the illumination optics can meet the requirements for three-aspherical-mirror imaging optics with a feature size of 0.06 mum.  相似文献   
85.
86.
Since the successful completion of the Human Genome Project, increasing concern is being directed toward the polymorphic aspect of the genome and its clinical relevance. A form of single-strand DNA-conformation polymorphism analysis (SSCP) employing nondenaturing slab-gel electrophoresis (SGE) is applicable to the genetic diagnosis of bladder cancer from urine samples. To bring this technique into routine clinical practice, the use of capillary electrophoresis (CE) is naturally favorable in terms of speed and automation. However, the resolving power of SSCP, a prerequisite basis for reliability required in diagnostics, remains as a challenge for CE systems. We thus focused on this topic and conducted studies on CE instruments equipped with a single capillary or an array of multiple capillaries, using the resolution (Rs) as a quantitative scale for the resolving power. Polymer concentration and buffer are shown to be the decisive parameters. High Rs values of >2.5 are achieved for representative SNPs markers under the optimized conditions, without sacrificing such intrinsic advantages of CE over SGE as the 10-fold quicker migration time and operation that is reproducible, continuous, and automatic. The strategies presented broaden the limits of CE in both the current and related applications.  相似文献   
87.
Ba2Bi4Ti5O18 single crystals were grown, and their dielectric permittivity, conductivity, and ferroelectricity were investigated along the a -(or b -)axis and the c -axis separately. The dielectric permittivity at 1 MHz along the a -(or b -)axis was 2000 at the Curie temperature (360°C); this value was 8 times greater than that along the c -axis. The dc conductivity was greater along the a -(or b -)axis than that along the c -axis, by one order of magnitude. In regard to the ferroelectricity, the saturated remanent polarization was 120 mC/m2 and the saturated coercive field was 3 MV/m along the a -(or b -)axis; values of 8.5 mC/m2 and 0.81 MV/m, respectively, were observed along the c -axis. The Ba2Bi4Ti5O18 single crystals had large electrical anisotropies, which were due to the layered structure.  相似文献   
88.
We reported previously that high hydrostatic pressure-injured stationary phase cells of Escherichia coli K-12 lost their intrinsic deoxycholate tolerance. The AcrAB-TolC multi-drug resistance pump driven by proton motive force has been argued to be responsible for the tolerance to deoxycholate. In this report, we tested the sensitivity of the AcrAB-TolC (three components) pump to high hydrostatic pressure treatment (HPT). E. coli K-12 treated with HPT became sensitive to AcrAB-TolC-specific drugs such as ethidium bromide, but not to tetracycline which is pumped out by a one-component transporter, Tet. Only E. coli K-12 overproducing both AcrAB and TolC exhibited restored tolerance to deoxycholate after HPT but not E. coli overproducing either TolC or AcrAB. These observations strongly suggest that three-component pumps such as AcrAB-TolC are more susceptible to HPT than one-component pumps such as Tet, resulting in the differential loss of deoxycholate tolerance in high hydrostatic pressure-injured E. coli cells.  相似文献   
89.
BACKGROUND: The stage of fruit ripeness at the time of harvest determines the final quality of ripe fruit. In this study, changes in the chemical composition of seed kernels from the oleaginous gourd Lagenaria siceraria (Molina) Standl. during maturation were evaluated to determine the best time to harvest the berries. Two cultivars (round and oval berry) were studied at three maturation stages (30 and 50 days after fruit set (DAFS) and complete plant whiteness (CPW)). RESULTS: Seed kernels were rich in oil (527.2–544.6 g kg−1), protein (402.8–403.3 g kg−1), minerals and energy. Maturation influenced the chemical compounds of the two cultivars differently. Best quantities of these components were reached at 50 DAFS. However, protein bioavailability was better at 30 DAFS and CPW in the round and oval berry cultivars respectively. Lagenaria siceraria oils were of good quality, containing an abundance of essential fatty acids (647.2–667.0 g kg−1). CONCLUSION: Both cultivars of L. siceraria should be harvested at 50 DAFS owing to the good nutritional properties of their seeds and oils. However, to obtain best‐quality proteins, round and oval berry cultivars should be harvested at 30 DAFS and CPW respectively. The results of this study will be useful in reducing the production time of fruits and improving the nutritional quality of their seeds. Copyright © 2011 Society of Chemical Industry  相似文献   
90.
Nishioka T  Irie M 《Meat science》2005,70(2):399-404
The firmness and stickiness of chilled porcine fat at 4°C were evaluated with an Instron compression tester and compared with fatty acid composition. Firmness of cylindrical adipose samples was measured at a force producing a 70% deformation. Firmness values were correlated with refractive index data (r=-0.67), melting point data (r=0.77), and saturated fatty acids concentration data (r=0.72) of the extracted lipid, and with sensory scores data (r=0.89). The firmness value correlated with the concentration of C18:0 (r=0.73). The stickiness of comminuted fat samples was evaluated with the Instron using a fixed load at a compression force of 20N and crosshead speed of 1.5mm/s. Single regression analyses showed that the stickiness parameters, stretch and adhesiveness correlated negatively with the concentration of the saturated fatty acids data (r=-0.64, -0.52) but positively and weakly with the monounsaturated fatty acids data (r=0.28, 0.34). Multiple regression analysis improved their relationships. These results indicate that mechanical evaluation may be used to predict porcine fat texture and saturated fatty acids concentration.  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