全文获取类型
收费全文 | 799篇 |
免费 | 23篇 |
专业分类
电工技术 | 5篇 |
综合类 | 5篇 |
化学工业 | 265篇 |
金属工艺 | 7篇 |
机械仪表 | 22篇 |
建筑科学 | 21篇 |
矿业工程 | 1篇 |
能源动力 | 37篇 |
轻工业 | 58篇 |
水利工程 | 4篇 |
石油天然气 | 1篇 |
无线电 | 80篇 |
一般工业技术 | 141篇 |
冶金工业 | 37篇 |
原子能技术 | 10篇 |
自动化技术 | 128篇 |
出版年
2023年 | 10篇 |
2022年 | 27篇 |
2021年 | 44篇 |
2020年 | 14篇 |
2019年 | 19篇 |
2018年 | 17篇 |
2017年 | 15篇 |
2016年 | 27篇 |
2015年 | 16篇 |
2014年 | 24篇 |
2013年 | 54篇 |
2012年 | 52篇 |
2011年 | 43篇 |
2010年 | 47篇 |
2009年 | 46篇 |
2008年 | 38篇 |
2007年 | 39篇 |
2006年 | 36篇 |
2005年 | 30篇 |
2004年 | 23篇 |
2003年 | 22篇 |
2002年 | 13篇 |
2001年 | 16篇 |
2000年 | 12篇 |
1999年 | 11篇 |
1998年 | 12篇 |
1997年 | 8篇 |
1996年 | 11篇 |
1995年 | 8篇 |
1994年 | 6篇 |
1993年 | 6篇 |
1992年 | 6篇 |
1991年 | 5篇 |
1990年 | 4篇 |
1989年 | 9篇 |
1988年 | 2篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1985年 | 8篇 |
1984年 | 5篇 |
1982年 | 6篇 |
1981年 | 5篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1976年 | 3篇 |
1973年 | 3篇 |
1972年 | 2篇 |
1966年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有822条查询结果,搜索用时 265 毫秒
1.
E Campagnutta R Cannizzaro M De Cicco G De Piero G Giorda F Sopracordevole A Parin C Scarabelli 《Canadian Metallurgical Quarterly》1998,50(7-8):305-311
BACKGROUND AND AIMS: Intestinal obstruction is a frequent cause of death in patients suffering from gynecological cancer, who have undergone multiple treatment in the form of surgery and/or chemotherapy and/or radiotherapy. The usual form of rescue treatment consists in the use of a nasogastric tube to administer support and analgesic treatment. Surgical gastrostomy is not a viable proposition in these extremely weak patients with large masses compressing and displacing the stomach. Percutaneous endoscopic gastrostomy (PEG), a technique first introduced for nutritional purposes, can be beneficially used to achieve decompression in these patients. METHODS: PEG was performed in a total of 67 patients who had already undergone multiple treatment for abdominal-pelvic neoplasia with upper gastrointestinal obstruction, who could no longer be operated and who had a life expectancy of less than sixty days. In three cases positioning was not possible owing to the lack of transillumination of the gastric and abdominal wall. 54/64 patients had previously undergone at least two operations. RESULTS: Esophagogastric lesions were found in 29% of patients, some of which were attributed to the nasogastric tube. Symptomatic wellbeing was obtained in 76.5% a few days after PEG. PEG remained in situ from 4 to 472 days. Slight peristomal infection was observed in 9% of cases. In seven cases it was necessary to add octreotide owing to the reappearance of symptoms. CONCLUSIONS: PEG is relatively easy to use and allows obstructive symptoms to be resolved in the majority of patients. Special medical skills are not required and the patient may be easily managed at home together with support therapy and pain management. Once PEG has been performed, it is possible to take fluids and semi-liquid foods, offering the patient a chance to taste flavours which have often been forgotten. PEG enables neoadjuvant chemotherapy to be performed in patients with previously untreated intestinal obstruction. 相似文献
2.
Carlo Bertucci Piero Salvadori Francesco Ciardelli Graziella Fatti 《Polymer Bulletin》1985,13(5):469-472
Summary Circular dichroism of isotactic samples of poly-(S)-4-methyl-1-hexene and poly-(R)-3,7-dimethyl-1-octene, have been measured in the vacuum ultraviolet spectral region (200-140 nm). The c.d. band at about 160. nm accounts for the optical activity in the visible region and reflects the presence of one screw sense helical conformation of the sample examined.The authors thank Prof. W.C. Johnson, Jr., Department of Biochemistry and Biophysics, Oregon State University, for allowing them to use the vacuum u.v. spectrometer. This work has been partially supported by a N.A.T.O. grant, and by Ministero Pubblica Istruzione (MPI), Roma — Italy. 相似文献
3.
Piero Villaggio 《Journal of Engineering Mathematics》2003,46(3-4):409-416
The diffusion of contact stresses between an elastic bar, bonded to an elastic half-plane and loaded longitudinally, requires the integration of a singular integral equation. The solution of this equation is not available in closed form, but only by a series expansion of the contact tangential force mutually transmitted between the stiffener and the plate. Since forty years it has been realized that the expansion of the solution in terms of Chebyshev polynomials is its most convenient method of representation. The procedure can also be extended to treat the brittle detachments of the tips of the stiffener when, according to Griffith's criterion of fracture, a balance can be virtually established between the increase of strain energy due to a propagation of cracks and the surface energy created. 相似文献
4.
Giampiero Sacchetti Paola Pittia Manuela Biserni Gian G. Pinnavaia & Marco D. Rosa 《International Journal of Food Science & Technology》2003,38(2):135-143
Summary Ready‐to‐eat breakfast cereals immersed in milk undergo undesirable changes in texture because of sudden moisture uptake. The textural changes are ascribable to a plasticizing effect of water, which modifies the mechanical strength of products by softening the starch/protein matrix. In this work, some textural parameters of different cereal flakes were derived from the force–displacement curves monitored during 300 s of immersion in milk. Hardness loss, deformability increment and changes in the force–displacement curve profile were calculated and plotted against soaking time. The application of a sugar coating process to a model cereal flake increased the initial product hardness and improved the preservation of the textural parameters during immersion. The Peleg model closely fitted the experimental data, with regression coefficients from 0.967 to 0.999. 相似文献
5.
Gian Piero Zarri 《Artificial Intelligence and Law》2007,15(3):251-279
An application of Narrative Knowledge Representation Language (NKRL) techniques on (declassified) ‘terrorism in Southern Philippines’
documents has been carried out in the context of the IST Parmenides project. This paper describes some aspects of this work:
it is our belief, in fact, that the Knowledge Representation techniques and the Intelligent Information Retrieval tools used
in this experiment can be of some interest also in an ‘Ontological Modelling of Legal Events and Legal Reasoning’ context. 相似文献
6.
Roberto Simonutti Angiolina Comotti Piero Sozzani 《Journal of Inorganic and Organometallic Polymers and Materials》1996,6(4):313-324
The existence of mesomorphism in polydiethylphosphazene was recently established by MAS NMR and X-ray diffraction characterization. In the present work the mechanism of motion of the ethyl side groups in the high-temperature polymorph tabove 45 C) is identified and compared to the arrangement of side groups in the low-temperature polymorph. For this purpose a few NMR active nuclei (13C,14N, and2H) were exploited to define the side-chain motions occurring at transition. Experiments performed at varying temperatures close to the onset of solid transition suggest the presence of jumps between two conformations in the pretransition state. Rotor-synchronized triple-resonance NMR of the high-temperature phase determined the average distances between the carbons and the nitrogens in the polymorphs. The theoretical prediction of the dipolar interaction between the nuclei supports the hypothesis that ethyl groups can undergo a complete rotation about the P CH2 bond by jumping across a conformational barrier. The mechanism of motion of the ethyl groups must be cooperative and the collapse of the rigid shell around the main chain is described at the transition. 相似文献
7.
8.
The definite trend towards the use of large-diameter rebars and the introduction of high-strength steels (f
y=500 to 600 MPa) make it necessary to study the effects of longitudinal splitting on the steel-to-concrete bond. The study
of splitting effects requires firstly basic tests to be performed in order to gather experimental information on bond and
confinement stresses acting at the bar-to-concrete interface. For this purpose, three series of tests were recently carried
out at the Politecnico di Milano. The results make it possible to ascertain a few basic properties of the bond after concrete
splitting, and to formulate empirical constitutive laws regarding the stresses and the displacements (bar slip and opening
of the splitting crack). All specimens consisted of a short deformed bar embedded in a concrete block, which had a preformed
splitting crack in the plane passing through the bar axis: twelve specimens (Tests A and C) were fitted up with a round deformed
bar having crescent-shaped lugs (Db=18 mm); seven specimens (Tests B) were fitted up with a specially machined deformed bar having a rectangular cross-section
and straigth, lugs, so that concrete deterioration close to the bar could be investigated at the surface of the specimen,
by means of the moiré technique. The tests were carried out at constant slip rate, up to very large slip values (
); both the ascending and the descending branches of the stress-slip curves were measured, for four different values of the
opening of the splitting crack. The agreement among the results of the three series is generally satisfactory and often very
good: consequently, constitutive laws regarding the four main variables (crack opening and bar slip, shear and confinement
stresses) can be worked out, as will be shown in a companion paper on constitutive relationships and on concrete deterioration
at the bar-to-concrete interface. 相似文献
9.
Laura Francesca Pisani Gian Eugenio Tontini Carmine Gentile Beatrice Marinoni Isabella Teani Nicoletta Nandi Pasquale Creo Emanuele Asti Luigi Bonavina Maurizio Vecchi Luca Pastorelli 《International journal of molecular sciences》2021,22(11)
Interleukin (IL)-33 is a member of the interleukin (IL)-1 family of cytokines linked to the development of inflammatory conditions and cancer in the gastrointestinal tract. This study is designed to investigate whether IL-33 has a direct effect on human gastric epithelial cells (GES-1), the human gastric adenocarcinoma cell line (AGS), and the gastric carcinoma cell line (NCI-N87) by assessing its role in the regulation of cell proliferation, migration, cell cycle, and apoptosis. Cell cycle regulation was also determined in ex vivo gastric cancer samples obtained during endoscopy and surgical procedures. Cell lines and tissue samples underwent stimulation with rhIL-33. Proliferation was assessed by XTT and CFSE assays, migration by wound healing assay, and apoptosis by caspase 3/7 activity assay and annexin V assay. Cell cycle was analyzed by means of propidium iodine assay, and gene expression regulation was assessed by RT-PCR profiling. We found that IL-33 has an antiproliferative and proapoptotic effect on cancer cell lines, and it can stimulate proliferation and reduce apoptosis in normal epithelial cell lines. These effects were also confirmed by the analysis of cell cycle gene expression, which showed a reduced expression of pro-proliferative genes in cancer cells, particularly in genes involved in G0/G1 and G2/M checkpoints. These results were confirmed by gene expression analysis on bioptic and surgical specimens. The aforementioned results indicate that IL-33 may be involved in cell proliferation in an environment- and cell-type-dependent manner. 相似文献
10.
Rosalinda Madonna Stefania Moscato Enza Polizzi Damiana Pieragostino Maria Concetta Cufaro Piero Del Boccio Francesco Bianchi Raffaele De Caterina Letizia Mattii 《International journal of molecular sciences》2021,22(11)
Cardiac connexins (Cxs) are proteins responsible for proper heart function. They form gap junctions that mediate electrical and chemical signalling throughout the cardiac system, and thus enable a synchronized contraction. Connexins can also individually participate in many signal transduction pathways, interacting with intracellular proteins at various cellular compartments. Altered connexin expression and localization have been described in diseased myocardium and the aim of this study is to assess the involvement of Cx43, Cx26, and some related molecules in ponatinib-induced cardiac toxicity. Ponatinib is a new multi-tyrosine kinase inhibitor that has been successfully used against human malignancies, but its cardiotoxicity remains worrisome. Therefore, understanding its signaling mechanism is important to adopt potential anti cardiac damage strategies. Our experiments were performed on hearts from male and female mice treated with ponatinib and with ponatinib plus siRNA-Notch1 by using immunofluorescence, Western blotting, and proteomic analyses. The altered cardiac function and the change in Cxs expression observed in mice after ponatinib treatment, were results dependent on the Notch1 pathway and sex. Females showed a lower susceptibility to ponatinib than males. The downmodulation of cardiac Cx43, Cx26 and miR-122, high pS368-Cx43 phosphorylation, cell viability and survival activation could represent some of the female adaptative/compensatory reactions to ponatinib cardiotoxicity. 相似文献