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排序方式: 共有292条查询结果,搜索用时 15 毫秒
111.
Hiroki Takahashi Taku Oshima Jon L. Hobman Neil Doherty Selina R. Clayton Mudassar Iqbal Philip J. Hill Toru Tobe Naotake Ogasawara Shigehiko Kanaya Dov J. Stekel 《Journal of the Royal Society Interface》2015,12(106)
Zinc is essential for life, but toxic in excess. Thus all cells must control their internal zinc concentration. We used a systems approach, alternating rounds of experiments and models, to further elucidate the zinc control systems in Escherichia coli. We measured the response to zinc of the main specific zinc import and export systems in the wild-type, and a series of deletion mutant strains. We interpreted these data with a detailed mathematical model and Bayesian model fitting routines. There are three key findings: first, that alternate, non-inducible importers and exporters are important. Second, that an internal zinc reservoir is essential for maintaining the internal zinc concentration. Third, our data fitting led us to propose that the cells mount a heterogeneous response to zinc: some respond effectively, while others die or stop growing. In a further round of experiments, we demonstrated lower viable cell counts in the mutant strain tested exposed to excess zinc, consistent with this hypothesis. A stochastic model simulation demonstrated considerable fluctuations in the cellular levels of the ZntA exporter protein, reinforcing this proposal. We hypothesize that maintaining population heterogeneity could be a bet-hedging response allowing a population of cells to survive in varied and fluctuating environments. 相似文献
112.
Donald S. Silverberg Dov Wexler Doron Schwartz 《International journal of molecular sciences》2015,16(6):14056-14074
Anemia is present in about 40% of heart failure (HF) patients. Iron deficiency (ID) is present in about 60% of the patients with anemia (about 24% of all HF patients) and in about 40% of patients without anemia (about 24% of all HF patients). Thus ID is present in about half the patients with HF. The ID in HF is associated with reduced iron stores in the bone marrow and the heart. ID is an independent risk factor for severity and worsening of the HF. Correction of ID with intravenous (IV) iron usually corrects both the anemia and the ID. Currently used IV iron preparations are very safe and effective in treating the ID in HF whereas little information is available on the effectiveness of oral iron. In HF IV iron correction of ID is associated with improvement in functional status, exercise capacity, quality of life and, in some studies, improvement in rate of hospitalization for HF, cardiac structure and function, and renal function. Large long-term adequately-controlled intervention studies are needed to clarify the effect of IV iron in HF. Several heart associations suggest that ID should be routinely sought for in all HF patients and corrected if present. In this paper we present our approach to diagnosis and treatment of iron deficiency in heart failure. 相似文献
113.
Dov Te’eni 《欧洲信息系统杂志》2017,26(3):237-239
114.
Dori L. Severi M. Impronta M. Sun J.Y.-C. Arienzo M. 《Electron Devices, IEEE Transactions on》1990,37(1):177-182
Charge trapping and interface-state generation in very thin nitride/oxide (4-nm Si3N4+8-nm SiO2) composite gate insulators are studied as a function of gate electrode work function and bottom oxide thickness. The behavior of the trapped positive charge under bias-temperature stress after avalanche electron injection (AEI) is investigated. Evidence is presented that secondary hole injection from the anode (gate/Si3N4 interface) and subsequent trapping near the SiO2-Si interface result in a turnaround of the flatband voltage shift during AEI from the substrate. Just like the thermal oxides on Si, slow-state generation near the SiO2-Si interface and boron acceptor passivation in the surface-space charge layer of the Si substrate are also observed after AEI in these nitride/oxide capacitors, and they are found to be strongly related to the secondary hole injection and trapping. Finally, interface-state generation can take place with little secondary anode hole injection and is enhanced by the occurrence of hole trapping 相似文献
115.
A phase-locked loop with variable parameters is considered. In such a system it is possible to obtain a short convergence time together with a small bandwidth. It is supposed that the PLL's parameters cannot be switched and there is a restriction on the velocity of the parameter variation. An optimal strategy of parameter variation is obtained which gives an improvement in convergence time by a factor of about 30 in comparision to fixed parameter and small-bandwidth PLLs. 相似文献
116.
The study tested a hypothesis whereby anxiety concerning examinations covering different subjects is an additive function of dispositional test anxiety and the anticipated results of individual tests. This hypothesis was generated on the basis of the integration of test anxiety theory and appraisal models of emotion. The study involved 118 students who took 3 examinations during the course of a Scholastic Aptitude Test preparation class, namely Quantitative, Verbal, and English (as a foreign language). Results with a repeated-measures design indicated that expected success, measured with self-efficacy for grade attainment 3 days before each test, incrementally predicted anxiety level during the test (i.e., beyond the prediction offered by test anxiety [trait], general efficacy [trait], and self-efficacy ratings for the previous exam). The same results were obtained when anxiety level was residualized on the basis of anxiety level associated either with the previous exam or with the Quantitative exam. These data indicate that anxiety level associated with different exams is an incremental function of dispositional and situational factors. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
117.
The authors describe two cases of premacular hemorrhage secondary to retinal macroaneurysm, with significant loss of vision. A few low-energy bursts of ND:YAG laser were applied to perforate the anterior surface of the hemorrhage, subsequently draining the blood into the vitreous cavity. The blood gradually cleared from the vitreous, with restoration of good vision. Nd:YAG laser seems to be a safe and efficient method for treating premacular hemorrhage and should be considered as a therapeutic option. 相似文献
118.
Sparse-pixel recognition of primitives in engineering drawings 总被引:4,自引:0,他引:4
Recognition of primitives in technical drawings is the first stage in their higher level interpretation. It calls for processing
of voluminous scanned raster files. This is a difficult task if each pixel must be addressed at least once, as required by
Hough transform or thinning-based methods. This work presents a set of algorithms that recognize drawing primitives by examining
the raster file sparsely. Bars (straight line segments), arcs, and arrowheads are identified by the orthogonal zig-zag, perpendicular
Bisector tracing, and self-supervised arrowhead recognition algorithms, respectively. The common feature of these algorithms
is that rather than applying massive pixel addressing, they recognize the sought primitives by screening a carefully selected
sample of the image and focusing attention on identified key areas. The sparse-pixel-based algorithms yield high quality recognition,
as demonstrated on a sample of engineering drawings. 相似文献
119.
Examined the relationship between empathy and ego development to determine whether, as J. Loevinger (1976) suggested, empathy is characteristic of higher levels of ego development. 51 undergraduates (dormitory advisors) completed the Affective Sensitivity Scale (a measure of empathy) and the Loevinger Sentence Completion Test (a measure of ego development). Analysis of test scores indicated that Ss at higher levels of ego development (I-? and above) had significantly higher empathy scores than did those at lower ego levels. Findings have implications for the selection and training of individuals to serve in counseling or quasi-counseling roles. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
120.
Use of different sensing materials and deposition techniques for thin-film sensors to increase sensitivity and selectivity 总被引:1,自引:0,他引:1
The performances of metal oxide semiconducting materials used as gas-sensing detectors depend strongly on their structural and morphological properties. The average grain size has been proved to play a prominent role and better sensor performances were found in polycrystalline films where the grain size is few tens of nm or smaller. On the other hand, thermal treatments during thin-film deposition and/or sample postprocessing could lead to a grain coalescence, thus decreasing the conductivity of the sensing film. Avoiding such a phenomenon, still keeping optimized processing conditions, will increase the sensor performances, maintaining the resistivity at acceptable values. In this work, new gas-sensing materials and new thin-film deposition procedures have been investigated. Aiming to preserve the sensitivity, to enhance selectivity and to reduce the drift, thin films of WO/sub 3/ and CrTiO/sub 3/ deposited by pulsed-laser ablation (PLA) and of SnO/sub 2/ deposited by rheotaxial growth and thermal oxidation techniques were comparatively characterized. Three issues were mainly addressed: the variation of the conductivity as a function of RH, the sensitivity toward benzene, CO, acetone, and NO/sub 2/, and the selectivity. 相似文献