全文获取类型
收费全文 | 13608篇 |
免费 | 1257篇 |
国内免费 | 16篇 |
专业分类
电工技术 | 133篇 |
综合类 | 8篇 |
化学工业 | 3418篇 |
金属工艺 | 185篇 |
机械仪表 | 417篇 |
建筑科学 | 590篇 |
矿业工程 | 30篇 |
能源动力 | 337篇 |
轻工业 | 2629篇 |
水利工程 | 113篇 |
石油天然气 | 39篇 |
无线电 | 1037篇 |
一般工业技术 | 2641篇 |
冶金工业 | 952篇 |
原子能技术 | 41篇 |
自动化技术 | 2311篇 |
出版年
2024年 | 38篇 |
2023年 | 190篇 |
2022年 | 199篇 |
2021年 | 527篇 |
2020年 | 408篇 |
2019年 | 408篇 |
2018年 | 543篇 |
2017年 | 546篇 |
2016年 | 654篇 |
2015年 | 542篇 |
2014年 | 751篇 |
2013年 | 1317篇 |
2012年 | 1144篇 |
2011年 | 979篇 |
2010年 | 732篇 |
2009年 | 685篇 |
2008年 | 691篇 |
2007年 | 621篇 |
2006年 | 568篇 |
2005年 | 388篇 |
2004年 | 335篇 |
2003年 | 317篇 |
2002年 | 293篇 |
2001年 | 196篇 |
2000年 | 157篇 |
1999年 | 142篇 |
1998年 | 226篇 |
1997年 | 189篇 |
1996年 | 139篇 |
1995年 | 129篇 |
1994年 | 96篇 |
1993年 | 99篇 |
1992年 | 56篇 |
1991年 | 44篇 |
1990年 | 38篇 |
1989年 | 41篇 |
1988年 | 41篇 |
1987年 | 20篇 |
1986年 | 32篇 |
1985年 | 39篇 |
1984年 | 29篇 |
1983年 | 27篇 |
1982年 | 26篇 |
1981年 | 22篇 |
1980年 | 24篇 |
1979年 | 25篇 |
1978年 | 14篇 |
1977年 | 14篇 |
1976年 | 21篇 |
1973年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 296 毫秒
91.
92.
Marcella Bonchio Mauro Carraro Martino Gardan Gianfranco Scorrano Enrico Drioli Enrica Fontananova 《Topics in Catalysis》2006,40(1-4):133-140
The incorporation of decatungstate in polymeric membranes provides new heterogeneous photocatalysts for the oxidation of organic
substrates under oxygen atmosphere at 25 °C. Photocatalytic membranes have been prepared yielding polymeric films with a high
thermal, chemical and mechanical stability (PVDF, PDMS, Hyflon). Surface spectroscopy techniques including transmittance and
reflectance UV-Vis and FT-IR have been used to assess the photocatalyst integrity within the polymeric support. Catalyst screening
has been performed under both homogeneous and heterogeneous photooxygenation conditions. The photocatalyst activity has been
evaluated in terms of the substrate conversion, turnover numbers, and recycling experiments. A membrane induced selectivity
behavior has been evidenced by comparison with homogeneous oxidations. 相似文献
93.
94.
SL Alam JD Satterlee JM Mauro TL Poulos JE Erman 《Canadian Metallurgical Quarterly》1995,34(47):15496-15503
The cyanide-ligated form of the baker's yeast cytochrome c peroxidase mutant bearing the mutation Asn82-->Ala82 ([N82A]CcPCN) has been studied by proton NMR spectroscopy. This mutation alters an amino acid that forms a hydrogen bond to His52, the distal histidine residue that interacts in the heme pocket with heme-bound ligands. His52 is a residue critical to cytochrome c peroxidase's normal function. Proton hyperfine resonance assignments have been made for the cyanide-ligated form of the mutant by comparison with 1-D and NOESY spectra of the wild-type native enzyme. For [N82A]CcPCN, proton NMR spectra reveal two significant phenomena. First, similar to results published for the related mutant [N82D]CcPCN [Satterlee, J. D., et al. (1994) Eur. J. Biochem. 244, 81-87], for Ala82 mutation disrupts the hydrogen bond between His52 and the heme-ligated CN. Second, four of the 24 resolved hyperfine-shifted resonances are doubled in the mutant enzyme's proton spectrum, leading to the concept that the heme active site environment is dynamically microheterogeneous on a very localized scale. Two magnetically inequivalent enzyme forms are detected in a pure enzyme preparation. Varying temperature causes the two enzyme forms to interconvert. Magnetization transfer experiments further document this interconversion between enzyme forms and have been used to determine that the rate of interconversion is 250 (+/- 53) s-1. The equilibrium constant at 20 degrees C is 1.5. Equilibrium constants have been calculated at various temperatures between 5 and 29 degrees C leading to the following values: delta H = 60 kJ mol-1; delta S = 0.20 kJ K-1 mol-1. 相似文献
95.
An executable subset of VDM-SL in an SA/RT framework 总被引:2,自引:2,他引:0
In this article we present the executable specification language IPTES Meta-IV based on the formal specification language VDM-SL. The language has been fitted to work in an SA/RT framework and the article presents how it supports the specification of the data transformation part of SA/RT. Furthermore we present some of the advanced constructs of the language seen as an executable specification language in its own right. Finally we present how an IPTES Meta-IV interpreter is used in combination with a high-level timed Petri net executor to execute SA/RT models. 相似文献
96.
Gerardo Gabriel Acosta Miguel Angel Mayosky José Maria Catalfo 《Applied Intelligence》1994,4(1):53-66
This article proposes a scheme for the on-line adjustment of three mode controller settings based on experimental measurements of closed-loop performance. It uses a recently developed heuristic tuning procedure to identify estimated process parameters. This method may give rise to conflicting estimates. Fuzzy Set theory is applied to manage the situation in terms of a fuzzy conjunction to combine the various estimates. PID control was chosen because of its wide use in the industrial environment due to driving simplicity and robustness. The article shows design, development, and computer simulation aspects. 相似文献
97.
RF Buckman MM Badellino LH Mauro JA Asensio C Caputo J Gass JD Grosh 《Canadian Metallurgical Quarterly》1993,34(5):717-25; discussion 725-7
A prospective study of 66 consecutive patients with cardiac wounds seen over a 27-month period is reported. No patient was excluded. Patients were stratified by injury mechanism and by physiologic scoring at admission using the cardiovascular-respiratory elements of the Trauma Score (CVRS). Admission cardiac rhythm was obtained in patients with a CVRS of 0 and a Glasgow Coma Scale (GCS) score of 3. Information concerning the anatomic extent of the cardiac wound, the presence or absence of tamponade, and the degree of injury to other structures was also collected prospectively. Seventy percent of the cardiac wounds were caused by gunshots. The probability of successful resuscitation was significantly related to mechanism of injury and physiologic condition on arrival. Among patients arriving with a CVRS of 0 and a GCS score of 3, survival correlated with cardiac rhythm. Pericardial tamponade did not prove to be an independent predictor of early survival. The presence of tamponade was statistically linked to the mechanism of injury. Transport by non-official conveyance was associated with a higher CVRS on arrival. Intoxication with alcohol or cocaine had no evident effect on resuscitation probability. 相似文献
98.
T Tomioka I Toshkov K Kazakoff A Andrén-Sandberg T Takahashi M Büchler H Friess R Vaughn PM Pour 《Canadian Metallurgical Quarterly》1995,15(5):231-250
Four normal pancreas, 8 chronic pancreatitis specimens, and 30 non-endocrine pancreatic tumors from humans and 6 normal and 6 induced pancreatic cancers in hamsters were examined immunohistochemically by antibodies against human transforming growth factor-alpha (TGF-alpha) and epidermal growth factor receptor (EGFR). Two normal pancreas and two pancreatic cancer specimens from each species were also studied immunoelectron microscopically by the immunogold method. In chronic pancreatitis, the reactivity and intensity of the staining with both antibodies were much greater in ductal/ductular cells than in the normal pancreas. All 30 pancreatic cancers reacted with both antibodies with a variable degree of reactivity and staining intensity. No correlation was found between the histological type of tumors, the degree of tumor differentiation, and the incidence and patterns of reactivity of either antibody. Immunoelectron microscopically, both EGFR and TGF-alpha were demonstrated primarily on the basal membrane. In the normal hamster pancreas, TGF-alpha was overexpressed in the alpha-cells but not in any other islet cells. Both TGF-alpha and EGFR were marginally detectable in the exocrine pancreas and in induced pancreatic lesions. This is the first demonstration of subcellular localization of TGF-alpha and EGFR in the normal and diseased human and hamster pancreas. 相似文献
99.
100.
C Casali JF Obadia E Canet K Bendjelid X André-Fou?t D Revel MF Janier 《Canadian Metallurgical Quarterly》1997,32(11):713-720
RATIONALE AND OBJECTIVES: Validation of new positron emission tomography (PET) tracers or magnetic (MR) imaging contrast agents is based on isolated rodent heart preparations. The use of larger animals could provide a more direct validation using the devices used for humans. METHODS: An isolated pig heart preparation has been developed and adapted to the technical constraints of whole body PET and MR imaging. This preparation could be used either in the Langendorff or working mode after selective cannulation of both coronary arteries. RESULTS: The authors showed that quantification of regional kinetics of PET tracers was possible using this preparation by measuring fluorine-18-labeled deoxyglycose (18FDG) kinetics in remote and ischemic territories. Experiments using MR imaging contrast agents, for myocardial perfusion, demonstrated the ability of this preparation to accurately validate these contrast agents over a wide range of flow rates. CONCLUSIONS: An isolated pig heart preparation could be developed to fulfill the constraints of PET and MR imaging, and proved useful for the study of the distribution of different tracers or contrast media developed for functional cardiac imaging in humans. 相似文献