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   1210篇
  免费   4篇
化学工业   18篇
金属工艺   6篇
机械仪表   2篇
建筑科学   8篇
矿业工程   1篇
轻工业   13篇
水利工程   1篇
无线电   4篇
一般工业技术   16篇
冶金工业   1141篇
自动化技术   4篇
  2019年   2篇
  2018年   3篇
  2017年   2篇
  2016年   1篇
  2013年   3篇
  2012年   2篇
  2011年   6篇
  2010年   3篇
  2009年   1篇
  2008年   2篇
  2007年   3篇
  2006年   6篇
  2005年   1篇
  2004年   1篇
  2003年   5篇
  2002年   3篇
  2001年   3篇
  2000年   1篇
  1999年   34篇
  1998年   347篇
  1997年   200篇
  1996年   136篇
  1995年   54篇
  1994年   63篇
  1993年   69篇
  1992年   10篇
  1991年   23篇
  1990年   9篇
  1989年   22篇
  1988年   25篇
  1987年   13篇
  1986年   24篇
  1985年   14篇
  1983年   2篇
  1982年   3篇
  1981年   9篇
  1980年   9篇
  1979年   3篇
  1978年   1篇
  1977年   28篇
  1976年   55篇
  1975年   3篇
  1972年   1篇
  1971年   3篇
  1970年   1篇
  1966年   1篇
  1960年   1篇
  1958年   1篇
  1955年   1篇
  1954年   1篇
排序方式: 共有1214条查询结果,搜索用时 31 毫秒
81.
82.
83.
84.
In this paper we analyze connectivity of one-dimensional Vehicular Ad Hoc Networks where vehicle gap distribution can be approximated by an exponential distribution. The probabilities of Vehicular Ad Hoc Network connectivity for difference cases are derived. Furthermore we proof that the nodes in a sub-interval [z1,z1 +Δz] of interval [0, z], z>0 where all the nodes are independently uniform distributed is a Poisson process and the relationship of Vehicle Ad hoc Networks and one-dimensional Ad Hoc networks ...  相似文献   
85.
Solvent extracts were prepared from Manda Enzyme®, one of the fermented health foods, and their activities of radical scavenging and cancer cell growth inhibition were evaluated. Manda Enzyme® was extracted with 55% ethanol, and then fractionated into n‐hexane, chloroform, ethyl acetate, methanol‐soluble and methanol‐insoluble fractions. The antioxidant activities were in the order chloroform > ethyl acetate > other fractions and of each fraction were positively related to the amount of total phenolics and the intensity of brown color. The cancer cell growth inhibitory activities were in the order n‐hexane > chloroform > other fractions. Proliferation of HRT‐18, HCT‐48 and HepG2 human cancer cells was inhibited by the treatment of the n‐hexane fraction of Manda Enzyme® at a concentration of 400 μg/mL to the extent of 75, 89 and 90%, respectively. From these results, it is considered that Manda Enzyme® has chemically different ingredients showing strong antioxidant and anticancer activity in vitro.  相似文献   
86.
87.
Rhodothermus marinus, a thermohalophilic bacterium, has a unique electron-transfer chain, containing, besides a cbb3 and a caa3 terminal oxidases, a novel cytochrome bc complex [Pereira, M. M., Carita, J. N., and Teixeira, M. (1999) Biochemistry 38, 1268-1275]. The membrane-bound iron-sulfur centers of this bacterium were studied by electron paramagnetic resonance (EPR) spectroscopy, leading to the identification of its main electron-transfer complexes. The resonances typical for the Rieske-type centers are not detected. Clusters S1 and S3 from succinate dehydrogenase were identified; interestingly, center S3 is shown to be present in two different conformations, with g values at 2.035, 2.009, and 2.001 and at 2.025, 2.002, and 2.000. Upon addition of NADH and dithionite, EPR signals assigned to resonances characteristic of binuclear and tetranuclear clusters develop and are attributed to the iron-sulfur centers of complexes I and II. A high-potential iron-sulfur protein- (HiPIP-) type center previously detected in the membranes of this bacterium [Pereira et al. (1994) FEBS Lett. 352, 327-330] is shown to belong indeed to a canonical HiPIP. This protein was purified and extensively characterized. It is a small water-soluble protein of approximately 10 kDa, containing a single [4Fe-4S]3+/2+ cluster. The reduction potential, determined by EPR redox titrations in intact and detergent-solubilized membranes as well as by cyclic voltammetry in solution, has a pH-independent value of 260 +/- 20 mV, in the range 6-9. In vitro reconstitution of the R. marinus electron-transfer chain shows that the HiPIP plays a fundamental role in the chain, as the electron shuttle between R. marinus cytochrome bc complex and the caa3 terminal oxidase, being thus simultaneously identified a HiPIP reductase and a HiPIP oxidase.  相似文献   
88.
How important is a particular object in a photograph of a complex scene? We propose a definition of importance and present two methods for measuring object importance from human observers. Using this ground truth, we fit a function for predicting the importance of each object directly from a segmented image; our function combines a large number of object-related and image-related features. We validate our importance predictions on 2,841 objects and find that the most important objects may be identified automatically. We find that object position and size are particularly informative, while a popular measure of saliency is not.  相似文献   
89.
DNA shape recognition determines the preferred binding sites for sequence-independent DNA binding proteins, and here we document that archaeal histones assemble archaeal nucleosomes in vitro centered preferentially within (CTG)6 and (CTG)8 repeats, close to junctions with flanking mixed-sequence DNA. Archaeal nucleosomes were not positioned by (CTG)4-, (CTG)5-, or (CTG)3AA(CTG)3-containing DNA sequences. The features of CTG repeat-containing sequences that direct eucaryal nucleosome positioning may also be similarly recognized by archaeal histones.  相似文献   
90.
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