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   13篇
  国内免费   2篇
电工技术   4篇
综合类   2篇
化学工业   44篇
金属工艺   2篇
机械仪表   1篇
建筑科学   22篇
矿业工程   5篇
能源动力   7篇
轻工业   13篇
水利工程   1篇
石油天然气   5篇
无线电   43篇
一般工业技术   37篇
冶金工业   27篇
原子能技术   1篇
自动化技术   39篇
  2024年   2篇
  2022年   10篇
  2021年   7篇
  2020年   7篇
  2019年   8篇
  2018年   5篇
  2017年   7篇
  2016年   8篇
  2015年   12篇
  2014年   5篇
  2013年   13篇
  2012年   13篇
  2011年   8篇
  2010年   10篇
  2009年   8篇
  2008年   6篇
  2007年   7篇
  2006年   6篇
  2005年   7篇
  2004年   8篇
  2003年   3篇
  2002年   9篇
  2001年   4篇
  2000年   3篇
  1998年   11篇
  1997年   7篇
  1996年   4篇
  1995年   2篇
  1994年   2篇
  1993年   6篇
  1990年   2篇
  1989年   2篇
  1985年   1篇
  1984年   2篇
  1983年   5篇
  1982年   5篇
  1981年   1篇
  1980年   1篇
  1979年   1篇
  1978年   1篇
  1976年   1篇
  1975年   2篇
  1974年   3篇
  1973年   2篇
  1972年   5篇
  1971年   1篇
  1970年   4篇
  1969年   2篇
  1968年   1篇
  1965年   1篇
排序方式: 共有253条查询结果,搜索用时 15 毫秒
241.
To test the proposition that an intake, multivariate battery of 42 psychometric predictors can predict duration of stay in rehabilitation and competence in ambulation and self-care, multiple-regression equations were computed for 54 Ss with left hemiplegia, and their retrospective outcome scores were highly accurately predicted. To reduce administration cost, redundant information was deleted. A compact battery of 27 variables was thus obtained, and the program was repeated. Resulting multiple correlations and predictive accuracy were only slightly less than those arrived at with the full battery. A cross-validation study on 15 new Ss yielded essentially identical results. It is concluded that the prediction of outcomes from psychometric measures, taken at the initiation of the rehabilitation program is highly feasible. (24 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
242.
The yeast, Candida oleophila, is acknowledged for its biocontrol activity against postharvest moulds. However, the mechanism of this activity is not fully understood. One of the conjectured modes of action is associated with extracellular lytic enzymes, such as beta-exoglucanase. The relationship of beta-exoglucanase in the biocontrol activity of C. oleophila was investigated by generating C. oleophila CoEXG1-knockouts and double-CoEXG1 transformants. The knockout transformants secreted 0-13% of the exoglucanase activity detected in the medium of the untransformed yeast (depending on the medium), indicating that CoEXG1 is the main gene responsible for the production of the secreted exoglucanase. Correspondingly, the double-CoEXG1 transformants secreted approximately twice as much 1,3-beta-exoglucanase as the untransformed C. oleophila. The biocontrol activity of the CoEXG1-knockout and the double-CoEXG1 transformants against Penicillium digitatum did not differ from that of the untransformed C. oleophila on kumquats. These results imply that the 1,3-beta-exoglucanase encoded by the gene CoEXG1 is not involved in the biocontrol activity of C. oleophila against P. digitatum under these experimental terms. However, these findings do not rule out the possibilities, that the participation of CoEXG1 in biocontrol is dependent on the activity of other gene products, or that its effect may be manifested under altered environmental conditions.  相似文献   
243.
An ``Alternating Sequential/Parallel' system, the Mopps was introduced a few years ago and is modified despite the fact that it solved satisfactorily a number of real-time problems. The new system, the ``Topps' is described and compared to Mopps in Section II and two applications are chosen to prove it to be superior. In Section III, the advantage of having a third basic, the ``ring' mode, is illustrated when solving sets of linear equations with band matrices. In Section IV, the advantage of having independent I/O for the slaves is illustrated for biomedical signal analysis.  相似文献   
244.
Transesophageal echocardiographic findings and their effect on disease management were evaluated in 216 patients with suspected cardiovascular source of emboli. Clinical and transesophageal echocardiographic findings were useful in defining pretest probability for finding a probable cardiovascular source of emboli on transesophageal echocardiography.  相似文献   
245.
In designing targets for laboratory long-rod penetration tests, the question of lateral confinement often arises, “How wide should the target be to exert enough confinement?” For ceramic targets, the problem is enhanced as ceramics are usually weak in tension and therefore have less self-confinement capability. At high velocities the problem is enhanced even more as the crater radius and the extent of the plastic zone around it are larger. Recently we used the quasistatic cavity expansion model to estimate the resistance of ceramic targets and its dependence on impact velocity [1]. We validated the model by comparing it to computer simulations in which we used the same strength model. Here we use the same approach to address the problem of lateral confinement.

We solved the quasistatic cavity expansion problem in a cylinder with a finite outside radius “b” at which σr (b) = 0 (σr = radial stress component). We did this for three cases: ceramic targets, metal targets, and ceramic targets confined in a metal casing. Generally, σr (a) is a decreasing function of “a” (“a” = expanding cavity radius, and σr (a) = the stress needed to continue opening the cavity). In the usual cavity expansion problem b → ∞, σr (a) = const., R =−σr (a) (R = resistance to penetration). For finite “b” we estimate R by averaging σr (a) over a range o ≤ a ≤ ar, (where ar, the upper bound of the range, is calibrated from computer simulations).

We ran 14 computer simulations with the CTH wavecode and used the results to calibrate ar for the different cases and to establish the overall validity of our approach.

We show that generally for Dt/Dp > 30, the degree of confinement is higher than 95% (Dt = target diameter; Dp = projectile diameter; and degree of CONFINEMENT = R/R; R∞ = resistance of a laterally infinite target). We also show the tensile strength of ceramic targets (represented by the spall strength Pmin) has a significant effect on the degree of confinement, while other material parameters have only a minor effect.  相似文献   

246.
The photodynamics of acetone and some other simple aliphatic ketones in the nπ* state are discussed in the light of recent results obtained in seeded supersonic beams. The Born-Oppenheimer approximation is used to describe the sequence of events beginning with light absorption and ending in molecular fragmentation. Intersystem crossing is shown to be an important process even for the isolated molecule. Its rate increases with the internal energy and may be related to the density of states in the triplet state. For all molecules studied so far, the results can be rationalized by assuming that dissociation takes place on the triplet surface, the S1 surface being stable in the energy range pertinent to these experiments (up to 35,000 cm−1 above the ground state). Fluorescence spectroscopy may be used also to detect small clusters. In the case of acetone, their presence is indicated by the decrease in the intensity of some spectral lines as a function of cooling efficiency. The results are used to estimate an upper limit for the van der Waals binding energies.  相似文献   
247.
A two-dimensional model for stratified turbulent-turbulent gas-liquid flow in inclined pipes is proposed. The gas phase is treated as bulk flow, but an exact solution is carried out for the liquid phase, applying the eddy viscosity theory to model the turbulent viscosity. The interfacial structure is taken into consideration using appropriate correlations for the interfacial shear stress. The model is capable of predicting the liquid velocity field, holdup and pressure drop given gas and liquid flow rates, physical properties, pipe size, and angle of inclination. The results are substantially better than the prediction of Lockhart and Martinelli (1949) correlation and better than the Taitel and Dukler (1976) model for stratified flow.  相似文献   
248.
249.
Journal of Superconductivity and Novel Magnetism - In this paper, operational principles of a cryogenic memory cell that utilizes high-temperature superconductors (high-Tc) are presented. Such a...  相似文献   
250.
Oreochromis fishes exhibit variability of sex-determination (SD) genes whose characterization contributes to understanding of the sex differentiation network, and to effective tilapia farming, which requires all-male culture. However, O. niloticus (On) amh is the only master-key regulator (MKR) of SD that has been mapped (XY/XX SD-system on LG23). In O. aureus (Oa), LG3 controls a WZ/ZZ SD-system that has recently been delimited to 9.2 Mbp, with an embedded interval rich with female-specific variation, harboring two paics genes and banf2. Developing genetic markers within this interval and using a hybrid Oa stock that demonstrates no recombination repression in LG3, we mapped the critical SD region to 235 Kbp on the orthologous On physical map (p < 1.5 × 10−26). DNA-seq assembly and peak-proportion analysis of variation based on Sanger chromatograms allowed the characterization of copy-number variation (CNV) of banf2. Oa males had three exons capable of encoding 90-amino-acid polypeptides, yet in Oa females, we found an extra copy with an 89-amino-acid polypeptide and three non-conservative amino acid substitutions, designated as banf2w. CNV analysis suggested the existence of two to five copies of banf2 in diploidic Cichlidae. Disrupting the Hardy–Weinberg equilibrium (p < 4.2 × 10−3), banf2w was concordant with female determination in Oa and in three cichlids with LG3 WZ/ZZ SD-systems (O. tanganicae, O. hornorum and Pelmatolapia mariae). Furthermore, exclusive RNA-seq expression in Oa females strengthened the candidacy of banf2w as the long-sought LG3 SD MKR. As banf genes mediate nuclear assembly, chromatin organization, gene expression and gonad development, banf2w may play a fundamental role inducing female nucleus formation that is essential for WZ/ZZ SD.  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