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   1164篇
  免费   0篇
化学工业   2篇
金属工艺   1篇
矿业工程   4篇
轻工业   1篇
石油天然气   1篇
无线电   3篇
一般工业技术   11篇
冶金工业   1140篇
自动化技术   1篇
  2019年   1篇
  2018年   1篇
  2016年   1篇
  2013年   2篇
  2007年   1篇
  2006年   1篇
  2003年   1篇
  1999年   4篇
  1998年   274篇
  1997年   204篇
  1996年   161篇
  1995年   86篇
  1994年   73篇
  1993年   59篇
  1992年   14篇
  1991年   13篇
  1990年   1篇
  1989年   9篇
  1988年   7篇
  1987年   3篇
  1986年   5篇
  1985年   2篇
  1984年   1篇
  1983年   2篇
  1982年   7篇
  1981年   11篇
  1980年   18篇
  1979年   1篇
  1978年   3篇
  1977年   70篇
  1976年   122篇
  1975年   3篇
  1973年   1篇
  1955年   2篇
排序方式: 共有1164条查询结果,搜索用时 15 毫秒
1.
15.7% of spermatozoa were found to be abnormal in silver fox males during their first reproductive season. The total number of spermatozoa and the abnormal spermatogenesis remained unchanged during mating season. Sexual stimulation increased the testosterone level only at the beginning of the mating season.  相似文献   
2.
A total of 280 children and adolescents with congenital and acquired mandibular defects and deformations were treated. The main principle in the treatment of such children is to begin treatment as early as possible. Stages of rehabilitation and scope of therapeutic measures for each stage are determined. The best results were attained in patients administered multiple-modality treatment by surgical, orthodontic, physiotherapeutic methods and therapeutic exercises at an early age immediately after the defect was diagnosed.  相似文献   
3.
In experiments on male rabbits with the lack of insulin it is been revealed violations after the past immobilization the intensivity and duration of neutrophilic leukocytosis decrease, contents of lysosomes in neutrophils, activity of acid phosphatase. By lysosomal ferments don't determine the can observer discordance of processes of coagulation, fibrinolysis, kininogenesis.  相似文献   
4.
Oligonitrophilic bacteria were cultivated on a medium containing only 2.5--10.0 mg/litre of nitrogen compounds. They assimilated elementary nitrogen only after utilization of these nitrogen compounds during growth and formation of nitrogen-fixing enzyme system. Their cells grown on a medium containing high concentrations of bound nitrogen did not fix nitrogen during further incubation in the atmosphere of 15N; therefore, the enzymes involved in nitrogen fixation were induced. These organisms are characterized by diauxia during their growth on media containing "start" doses of nitrogen. Enzymes catalysing nitrogen fixation in azotobacter are also induced. But, contrary to oligonitrophilic bacteria, the azotobacter does not require nitrogen compounds in the medium in order to adapt to molecular nitrogen, and its growth curve is not of a biphasal character. These data and the evidence of other authors suggest that all nitrogen-fixing microorganisms are characterized by the induced, not constitutive, enzymes involved in reduction of molecular nitrogen.  相似文献   
5.
Bioelectrical impedance analysis (BIA) is a convenient, inexpensive, and noninvasive technique for measuring body composition. BIA has been strongly correlated with total body water (TBW) and also has been validated against hydrodensitometry (HD). The accuracy and clinical utility of BIA and HD during periods of substantial weight loss remain controversial. We measured body composition in moderately and severely obese patients serially using both methods during a very-low-energy diet (VLED). Mean initial weight in these patients was 116 (+/-30) kg (range, 74-196 kg). Mean weight loss was 24 (+/-13) kg with a decrease in fat mass (FM) by HD of kg (p < 0.001) and a decrease in fat-free mass (FFM) of 3.6 kg (p < 0.05). Loss of FFM is best predicted by the rate (kg/wk) of weight loss (r2 = 0.86, p < 0.0001). FFM, as predicted from BIA equations, was highly correlated with FFM as estimated by HD during all testing sessions (r = 0.92-0.98). Although highly correlated, BIA overestimated FFM relative to HD and this difference appeared to be more pronounced for taller patients with greater truncal obesity. Although the discrepancy was no greater during weight-loss treatment, the level of disagreement was considerable. Therefore, the two methods cannot be used interchangeably to monitor relative changes in body composition in patients with obesity during treatment with VLED. The discrepancy between BIA and HD may be caused by body mass distribution considerations and by perturbations in TBW which affect the hydration quotient for FFM (BIA) and/or which affect the density constants for FFM and FM (HD).  相似文献   
6.
It is shown that for scattering from a plane of an average rough surface, the scattering cross section of the range of small grazing angles of the scattered wave demonstrates a universal behavior. If the angle of incidence is fixed (in general, it should not be small), the diffuse component of the scattering cross section for the Dirichlet problem is proportional to &thetas;2 where &thetas; is the (small) angle of elevation and for the Neumann problem it does not depend on &thetas;. For the backscattering case, these dependencies correspondingly become &thetas;4 and &thetas;0. The result is obtained from the structure of the equations that determine the scattering problem rather than the use of an approximation  相似文献   
7.
We consider the theory of waves scattered from a moving, rough, and dispersive surface in the small perturbation limit. The first-order scattered field for a time-dependent surface is obtained in the far zone of scattering in terms of the two-dimensional spectral amplitude of the surface and its dispersion relation. We develop a rigorous Δk radar theory and show that the nonzero output of a Δk radar occurs only when the Bragg condition for each signal component is satisfied separately. The frequency correlation function of the scattered field is then proportional to the mean value of the product of the spectral amplitudes of the surface at the corresponding Bragg wavenumbers. The mean value of this product is nonzero only for surfaces that have a locally varying spectrum and is proportional to the Fourier transform (with the argument Δk) of the variation of the local spectrum with respect to the pattern position. Such variations may be caused by either amplitude or phase modulation of the surface structure. In the former case, our results are similar to the results of existing theory. The latter case of phase modulation of the surface (for example, internal waves interacting with capillary waves) cannot be explained by previous theory  相似文献   
8.
Forty patients with temporal epilepsy were operated on with a stereotaxic technique. Eleven patients had a unilateral localization of the epileptic focus, and in 29 bitemporal foci were diagnosed. In evaluating the results of the treatment the dynamics of the epileptic fits, the peculiarities of changes in the mental status, and the degree of social adaptation were taken into consideration. A postoperative improvement was achieved in 73% of the patients with monotemporal lesions, while in those with bitemporal epilepsy and distinct persistent mental disorders the state was improved in 44% of the cases. Indications for the choice of the zone of destruction depending on the clinical peculiarities of the lesion are presented.  相似文献   
9.
Some indexes of nitrogen metabolism in blood, rumen content and urine of bull-calves fed on urea were studied as affected by UV-radiation. The content of protein, nonprotein, amine nitrogen, urea and ammonia in the rumen content and blood as well as as intensity of urea nitrogen and ammonia excretion with urine were determined. It is established that when 25% of protein necessary for the organism was replaced in the ration by urea, UV-radiation with a dose of 120 merg/h-m2 lowers already at the beginning of irradiation the amount of amine nitrogen and further the protein one in the young cattle rumen content. In blood of the irradiated bull-calves at the beginning of irradiation the level of amine nitrogen decreases, the level of nonprotein nitrogen lowers with a longer irradiation. The content of protein nitrogen in blood at that time increases. It was found that the content of ammonia in the bull-calves rumen during the first twenty-hours lowers, the amount of urea in blood does not change essentially. Simultaneously the ammonia excretion with urine intensifies, at the same time the excretion of urea nitrogen with urine does not differ essentially from that in the control bull-calves. In the bull-calves under study the nitrogen balance and average daily gains increase that may testify to the fact that UV-radiation in the applied dose stimulates a more complete utilization of urea nitrogen for the synthesis processes in the organism.  相似文献   
10.
CT scans of 9 patients with orbital pseudotumor (bilateral in 6 and unilateral in 3) showed findings distinct from those observed in Graves' ophthalmopathy. In bilateral involvement, they ranged from localized mass lesions to complete obiliteration of normal orbital CT anatomical landmarks; diffuse or multifocal lesions involving the posterior globe and muscle insertions were most typical of the diagnosis. However, findings in unilateral psedotumor may be indistinguishable from orbital mass lesions other than Graves' ophthalmopathy. Serial CT scans were used to show progression of disease and response to treatment.  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