全文获取类型
收费全文 | 434篇 |
免费 | 24篇 |
专业分类
电工技术 | 2篇 |
综合类 | 2篇 |
化学工业 | 171篇 |
金属工艺 | 3篇 |
机械仪表 | 9篇 |
建筑科学 | 21篇 |
矿业工程 | 1篇 |
能源动力 | 8篇 |
轻工业 | 55篇 |
水利工程 | 2篇 |
石油天然气 | 1篇 |
无线电 | 17篇 |
一般工业技术 | 69篇 |
冶金工业 | 32篇 |
原子能技术 | 1篇 |
自动化技术 | 64篇 |
出版年
2023年 | 7篇 |
2022年 | 27篇 |
2021年 | 27篇 |
2020年 | 10篇 |
2019年 | 6篇 |
2018年 | 11篇 |
2017年 | 12篇 |
2016年 | 12篇 |
2015年 | 15篇 |
2014年 | 20篇 |
2013年 | 31篇 |
2012年 | 27篇 |
2011年 | 27篇 |
2010年 | 27篇 |
2009年 | 13篇 |
2008年 | 15篇 |
2007年 | 17篇 |
2006年 | 11篇 |
2005年 | 5篇 |
2004年 | 5篇 |
2003年 | 2篇 |
2002年 | 7篇 |
2000年 | 4篇 |
1999年 | 7篇 |
1998年 | 10篇 |
1997年 | 6篇 |
1996年 | 5篇 |
1995年 | 7篇 |
1994年 | 5篇 |
1993年 | 4篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1984年 | 5篇 |
1982年 | 2篇 |
1968年 | 2篇 |
1954年 | 3篇 |
1948年 | 5篇 |
1943年 | 3篇 |
1942年 | 5篇 |
1940年 | 3篇 |
1939年 | 6篇 |
1935年 | 3篇 |
1934年 | 2篇 |
1933年 | 2篇 |
1932年 | 3篇 |
1925年 | 2篇 |
1924年 | 1篇 |
排序方式: 共有458条查询结果,搜索用时 15 毫秒
81.
During in vitro development of rat skeletal muscle cells, contraction and calcium currents progressively appear after fusion of myoblasts. To investigate whether muscle-specific functions are expressed in the absence of myoblast fusion, rat neonatal muscle cells were cultured in a differentiation medium under conditions that are well known to inhibit fusion: prolonged culture in a low-calcium medium or treatment with cytochalasin B. We have demonstrated that the fusion-arrested cells expressed differentiative properties in L-type calcium current, transient release of calcium ions from internal stores in response to caffeine and depolarizing agents, and contraction elicited by depolarization. Properties and potential-dependence of L-type calcium currents were similar to that in control fused cells, but T-type calcium currents were not observed, while both types coexist in myotubes. Properties of calcium transients and voltage dependence of contraction suggested that the excitation-contraction mechanisms were well established. However, comparing to well-developed myotubes at the same time of culture, the characteristics of calcium transients and contraction of fusion-arrested cells were closer to those of younger myotubes, which can be interpreted in terms of a delay in maturation of excitation-contraction coupling and contractile machinery. All these observations demonstrate that myoblast fusion is not necessary for triggering the establishment of calcium transport and release and contractile functions of rat muscle cells developing in culture. The appearance of muscle-specific functions is consistent with previous results demonstrating that the fusion-arrested cells express muscle-specific proteins and structures. 相似文献
82.
Prof. Dr.-Ing. Constantin Canavas 《化学,工程师,技术》1995,67(6):709-717
History of Control and Automation in Chemical Engineering . Control and automatization have been associated with chemistry and chemical engineering since long before the present information era. Since the early history of mankind precedents of what were to be called unit operations have been closely associated with control and automation concepts. The history of these concepts illustrates the development of theory and practice from the classic Greek times through Islamic and European Middle Ages up to today's chemical engineering. It also demonstrates the close interdependence of such development with leading social and scientific concepts, education systems and economic conditions. 相似文献
83.
J Constantin F Suzuki-Kemmelmeier NS Yamamoto A Bracht 《Canadian Metallurgical Quarterly》1997,54(10):1115-1125
Production, uptake, and metabolic effects of cyclic AMP (cAMP) were measured in the bivascularly perfused rat liver in anterograde and retrograde perfusion. Glucagon, cAMP, N6,2'-O-dibutyryl cAMP and N6-monobutyryl cAMP were infused into the portal vein (anterograde perfusion), the hepatic vein (retrograde perfusion), or the hepatic artery (anterograde and retrograde perfusion) in order to reach different cell populations. The following results were obtained: (1) cAMP release caused by glucagon was directly proportional to the cell spaces that were accessible via the hepatic artery in anterograde and retrograde perfusion; since the metabolic effects of glucagon were not proportional to the accessible cell spaces, this observation also implies a disproportion between cAMP release and metabolic effects of the hormone; (2) when cAMP and N6,2'-O-dibutyryl cAMP were given to all liver cells (e.g. when infused into the portal vein), their metabolic effects were qualitatively and quantitatively the same and qualitatively equal to the effects of glucagon; (3) the changes caused by cAMP were a function of the cell spaces that can be reached via the hepatic artery in anterograde and retrograde perfusion; this behaviour contrasts markedly with that of glucagon, whose metabolic effects were practically independent of the accessible cell spaces; and (4) the effects of N6,2'-O-dibutyryl cAMP and N6-monobutyryl cAMP were independent of the cell spaces that were accessible via the hepatic artery in anterograde and retrograde perfusion; in this respect their behaviour was equal to that of glucagon. It is apparent that exogenously added cAMP mimicked the metabolic effects of glucagon in the liver only when it was supplied to all liver cells. Since glucagon, N6,2'-O-dibutyryl cAMP, and N6-monobutyryl cAMP were able to produce a full response even when given to only 30% of the liver parenchyma, it was concluded that cAMP production under the stimulus of glucagon or in consequence of the metabolic transformation of N6,2'-O-dibutyryl cAMP and N6-monobutyryl cAMP occurs in a compartment to which exogenous cAMP has no access. cAMP generated within this compartment is possibly able to diffuse from cell to cell. 相似文献
84.
Wu
Yang Yan‐Wu Wang Irinel‐Constantin Morrescu Zhi‐Wei Liu Yuehua Huang 《国际强度与非线性控制杂志
》2020,30(12):4550-4564
》2020,30(12):4550-4564
The article proposes several fault‐tolerant control (FTC) laws for singularly perturbed systems (SPS) with actuator faults and disturbances. One of the main challenges in this context is that the fast‐slow decomposition is not available for actuator faults and disturbances. In view of this, some conditions for the asymptotic stability of the closed‐loop dynamics are investigated by amending the composite Lyapunov approach. On top of this, a closed‐form expression of the upper bound of singular perturbation parameter (SPP) is provided. Moreover, we design several SPP‐independent composite FTC laws, which can be applied when this parameter is unknown. Finally, the chattering phenomenon is eliminated by using the continuous approximation technique. We also emphasize that, for linear SPSs, the FTC design can be formulated as a set of linear matrix inequalities, while the SPP upper bound can be obtained by solving a convex optimization problem. Two numerical examples are given to illustrate the effectiveness of the proposed methodology. 相似文献
85.
The concentration-dependent effects of two different synthetic phospholipids on cell proliferation and phosphatidylcholine
biosynthesis were compared in Madin-Darby canine kidney (MDCK) cells. The alkyllysophospholipid 1-O-octadecyl-2-O-methyl-sn-glycero-3-phosphocholine and the alkylphosphocholine, hexadecylphosphocholine, inhibited cell proliferation with half-inhibitory
concentrations (IC50) of 75 and 135 μmol/L, respectively. The agents also inhibited phosphatidylcholine biosynthesis in confluent and proliferating
MDCK cells. The IC50 of 1-O-octadecyl-2-O-methyl-sn-glycero-3-phosphocholine was 40 μmol/L in confluent cells and 20 μmol/L in proliferating cells, whereas the IC50 of hexadecylphosphocholine was higher in both experimental systems (67 μmol/L in confluent cells and 40 μmol/L in proliferating
cells). Further experiments revealed that the effect of both agents on phosphatidylcholine biosynthesis was reversible and
that the inhibition was mediated by translocation of the rate-limiting enzyme of this pathway, CTP: phosphocholine cytidylyltransferase
(EC 2.7.7.15), from membranes to the cytosol, where it is inactive. The present findings suggest that the inhibition of phosphatidylcholine
biosynthesis by both synthetic phospholipids might be related, in part, to their antiproliferative effects. 相似文献
86.
Summary Poly(methyl methacrylate)-block-polysulfide-block-poly(methyl methacrylate) copolymers were synthesized for the first time through a new method involving the free radical
polymerization of MMA in the presence of a thiocol oligomer as a chain transfer agent, followed by chemical oxidation of the
remaining SH end-groups. The chain transfer constant of the SH end-groups of the thiocol was estimated from the rate of consumption
of the thiol groups versus the rate of consumption of the monomer (CT=0.67). The triblock copolymers synthesized were characterized by SEC and 1H NMR measurements. 相似文献
87.
In this paper, we introduce a general multilevel gradient Uzawa algorithm for symmetric saddle point systems. We compare its performance with the performance of the standard Uzawa multilevel algorithm. The main idea of the approach is to combine a double inexact Uzawa algorithm at the continuous level with a gradient type algorithm at the discrete level. The algorithm is based on the existence of a priori multilevel sequences of nested approximation pairs of spaces, but the family does not have to be stable. To ensure convergence, the process has to maintain an accurate representation of the residuals at each step of the inexact Uzawa algorithm at the continuous level. The residual representations at each step are approximated by projections or representation operators. Sufficient conditions for ending the iteration on a current pair of discrete spaces are determined by computing simple indicators that involve consecutive iterations. When compared with the standard Uzawa multilevel algorithm, our proposed algorithm has the advantages of automatically selecting the relaxation parameter, lowering the number of iterations on each level, and improving on running time. By carefully choosing the discrete spaces and the projection operators, the error for the second component of the solution can be significantly improved even when comparison is made with the discretization on standard families of stable pairs. 相似文献
88.
Constantin Pyriki 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1948,88(3):254-269
Ohne Zusammenfassung 相似文献
89.
Constantin Ciobanu Xiaozu Han Constantin N. Cascaval Fengchun Guo Dan Rosu Leonard Ignat Gabriela Moroi 《应用聚合物科学杂志》2003,87(11):1858-1867
Three series of weakly crosslinked polyurethanes based on a hydroxyterminated polybutadiene, hydroxyterminated butadiene–acrylonitrile copolymer, and hydroxyterminated ethylene–adipate–maleate–fumarate copolymer were prepared while varying the hard segment content between 1.72 and 2.36 mol ? NH? COO? /1000 g polymer. Information on the microphase structure and the properties of the synthesized polyurethanes was obtained by differential scanning calorimetry, wide‐angle X‐ray scattering, and mechanical studies. Up to a urethane concentration of around 2 mol ? NH? COO? /1000 g polymer, there is a mixture of hard–hard and hard–soft segments. Above this concentration a large part of the hard–soft segments passes into hard–hard crystallites, liberating the soft segments. The best mechanical properties of the studied polyurethanes were found for a urethane concentration of around 2 mol ? NH? COO? /1000 g polymer. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1858–1867, 2003 相似文献
90.