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61.
Tracing the trajectory of scientific fields has been recognized by informaticians, nonetheless, little effort has been dedicated to understanding the evolution of the fast-moving research field of transport, quantitatively and qualitatively. This paper identifies intellectual turning points and emerging trends in the area of transport. Using bibliometric methods, co-keyword networks, journal co-citation networks, highly cited categories, and country and institute networks are detected, visualized and discussed. To conduct this analysis, all publications (35,712) in 23 top journals in the field of transport are extracted from the Institute for Scientific Information (Web of Science). The output of this article could be a valuable source for academics and practitioners working in the field of transport planning and those who work in the areas having a strong relationship with transport issues including mathematicians, economics, operation research, management and geography.  相似文献   
62.
Van der Waals (vdW) heterostructures have recently been introduced as versatile building blocks for a variety of novel nanoscale and quantum technologies. Harnessing the unique properties of these heterostructures requires a deep understanding of the involved interfacial interactions and a meticulous control of the growth of 2D materials on weakly interacting surfaces. Although several epitaxial vdW heterostructures have been achieved experimentally, the mechanisms governing their synthesis are still nebulous. With this perspective, herein, the growth dynamics of antimonene on graphene are investigated in real time. In situ low‐energy electron microscopy reveals that nucleation predominantly occurs on 3D nuclei followed by a self‐limiting lateral growth with morphology sensitive to the deposition rate. Large 2D layers are observed at high deposition rates, whereas lower growth rates trigger an increased multilayer nucleation at the edges as they become aligned with the Z2 orientation leading to atoll‐like islands with thicker, well‐defined bands. This complexity of the vdW growth is elucidated based on the interplay between the growth rate, surface diffusion, and edges orientation. This understanding lays the groundwork for a better control of the growth of vdW heterostructures, which is critical to their large‐scale integration.  相似文献   
63.
A vestigial, nonphotosynthetic plastid has been identified recently in protozoan parasites of the phylum Apicomplexa. The apicomplexan plastid, or "apicoplast," is indispensable, but the complete sequence of both the Plasmodium falciparum and Toxoplasma gondii apicoplast genomes has offered no clue as to what essential metabolic function(s) this organelle might perform in parasites. To investigate possible functions of the apicoplast, we sought to identify nuclear-encoded genes whose products are targeted to the apicoplast in Plasmodium and Toxoplasma. We describe here nuclear genes encoding ribosomal proteins S9 and L28 and the fatty acid biosynthetic enzymes acyl carrier protein (ACP), beta-ketoacyl-ACP synthase III (FabH), and beta-hydroxyacyl-ACP dehydratase (FabZ). These genes show high similarity to plastid homologues, and immunolocalization of S9 and ACP verifies that the proteins accumulate in the plastid. All the putatively apicoplast-targeted proteins bear N-terminal presequences consistent with plastid targeting, and the ACP presequence is shown to be sufficient to target a recombinant green fluorescent protein reporter to the apicoplast in transgenic T. gondii. Localization of ACP, and very probably FabH and FabZ, in the apicoplast implicates fatty acid biosynthesis as a likely function of the apicoplast. Moreover, inhibition of P. falciparum growth by thiolactomycin, an inhibitor of FabH, indicates a vital role for apicoplast fatty acid biosynthesis. Because the fatty acid biosynthesis genes identified here are of a plastid/bacterial type, and distinct from those of the equivalent pathway in animals, fatty acid biosynthesis is potentially an excellent target for therapeutics directed against malaria, toxoplasmosis, and other apicomplexan-mediated diseases.  相似文献   
64.
This article proposes a bi‐criteria formulation to find the optimal location of light rapid transit stations in a network where demand is elastic and budget is constrained. Our model is composed of two competing objective functions seeking to maximize the total ridership and minimize the total budget allocated. In this research, demand is formulated using the random utility maximization method with variables including access time and travel time. The transit station location problem of this study is formulated using mixed integer programming and we propose a heuristic solution algorithm to solve large‐scale instances which is inspired by the problem context. The elastic demand is integrated with the optimization problem in an innovative way which facilitates the solution process. The performance of our model is evaluated on two test problems and we carry out its implementation on a real‐world instance. Due to the special shape of the Pareto front function, significant practical policy implications, in particular budget allocation, are discussed to emphasize the fact that the trade‐off between cost and benefit may result in large investments with little outcomes and vice versa.  相似文献   
65.
A single rock type was drilled using two types of thermally stable polycrystalline diamond compact (PDC) and an impregnated diamond core bit using a fully instrumented laboratory drilling rig at a fixed rotational speed, and over a range of weights on bit (WOB). Operating parameters of the bits such as WOB, rate of penetration (ROP), rotational speed (RPM), torque and drilling specific energy (SE) were continuously monitored during the drilling trials. The effects of these parameters on the performance of the bits were examined. Relations between the drilling variables are also described. At each set WOB for each bit, the drilling detritus were collected. The detritus sizes between 1180 and 53 microns were analysed using wet sieving and sub 53 micron was analysed using a Malvern particle size machine. Both data were combined to obtain a particle size distribution at set WOBs for each bit. The relations between the particle size of the drilling detritus and operating parameters, cutter size and wear of the PDC and impregnated diamond core bits, and original rock grain size were established. An increase in WOB, ROP, wear rates, pins or diamond size increased the drilling detritus size for the bits. No relation was found between the drilling detritus and the rock grain size due to the regrinding effect and the high proportion (> 30%) of matrix material in the rock.  相似文献   
66.
The ability to recognize and accurately interpret facial expressions are critical social cognition skills in primates, yet very few studies have examined how primates discriminate these social signals and which features are the most salient. Four experiments examined chimpanzee facial expression processing using a set of standardized, prototypical stimuli created using the new ChimpFACS coding system. First, chimpanzees were found to accurately discriminate between these expressions using a computerized matching-to-sample task, and recognition was impaired for all but one expression category when they were inverted. Third, a multidimensional scaling analysis examined the perceived dissimilarity among these facial expressions revealing 2 main dimensions, the degree of mouth closure and extent of lip-puckering and retraction. Finally, subjects were asked to match each facial expression category using only individual component features. For each expression category, at least 1 component movement was more salient or representative of that expression than the others. However, these were not necessarily the only movements implicated in subject's overall pattern of errors. Therefore, similar to humans, both configuration and component movements are important during chimpanzee facial expression processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
67.
The authors reflect on "Scholarship in Psychology: A Paradigm for the Twenty-First Century" (D. F. Halpern et al., 1998) from their perspective as liberal arts college professors. They applaud various features of the report's multidimensional understanding of scholarship, suggest points of clarification and critique, and conclude with a suggestion for defining faculty priorities and rewards. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
68.
Invasive squamous carcinoma of the uterine cervix (CC) arises from sequential progression of low-grade (L) and high-grade (H) squamous intraepithelial lesions (SILs). In clinical observations, these lesions are frequently found as synchronous multiple foci. The nature and evolutionary mechanism of these lesions are largely unknown. We have performed allelotyping of three 3p markers (at 3p14, 3p22-24, and 3p25) on 22 LSILs and 15 HSILs microdissected from patients with multiple (n = 21) or uniform (n = 6) cervical lesions. The results were analyzed together with our previous allelotyping of 57 deeply invasive CCs. Loss of heterozygosity at one of the three markers was observed in 23%, 27%, and 31 % of LSILs, HSILs, and CCs, respectively. Frequent and early allelic loss was noted (in 30% of LSILs and 50% of HSILs) at 3p14, which may harbor tumor suppressor genes involved in early stages of cervical carcinogenesis. A high frequency of microsatellite alteration (MA) was found in LSIL (41%) and HSIL (67%) but not in CC (5.3%). In particular, MA was more frequently found in low-grade lesions in association with invasive cancers (75%, 6/8) than in those associated with SILs (29%, 4/14) (P < 0.05). Together with the finding of a monoclonal origin of premalignant and malignant cervical lesions, the present results allow us to propose a model of local field effect of genomic instability that progressively affects the clonal evolution of SIL of uterine cervix.  相似文献   
69.
The cathodic reduction of dibenzofuran ( 2 ), 2-chlorodibenzofuran ( 4 ), and 3-chlorodibenzofuran ( 1 ) in deuterated methanol is investigated. The Birch-type reduction product 1,4-dibenzofuran ( 3 ) is formed from 1 via 2 , whereas 2-chloro-1,4-dihydrodibenzofuran ( 5 ) is obtained as by-product besides 3 from 4 as starting compound. Deuterium is only incorporated into the reduction products if CH3OD or CD3OD but not if CD3OH are used. This observation is strongly indicative of a polar mechanism involving protonation rather than a radical mechanism with hydrogen atom abstraction to be operative.  相似文献   
70.
Biosensor assay for determination of haptoglobin in bovine milk   总被引:1,自引:0,他引:1  
Despite more than 30 years of research into mastitis diagnostics, there are few alternatives to the somatic cell count (SCC) in practical use for identification of cows with subclinical mastitis. Mastitis is not only an animal welfare problem, but also affects the yield, composition and technological properties of milk. Hence, dairy cooperatives give farmers a premium quality payment to encourage low SCC although there is no clear scientific data defining the level of SCC in bulk tank milk that is associated with additional benefits in terms of milk quality. Recent research on alternative markers for inflammatory reactions in the lactating cow, e.g. in mastitis, includes investigations of the acute phase protein, haptoglobin (Hp). So far, the content of Hp in milk has mainly been studied in relation to mastitis diagnostics, with little attention given to its importance for milk composition and technological properties. At present, Hp in milk is measured using ELISA, but this technique is not suitable for routine large-scale analysis. In recent years, optical biosensor technology has been used for automated and rapid quantitative analysis of different components in milk, but so far not for analysis of acute phase proteins. The aim of the present study was to develop a rapid and sensitive biosensor method to determine Hp in milk. An affinity sensor assay based on the interaction between Hp and haemoglobin was developed using surface plasmon resonance (SPR) biosensor technology. The assay was used to analyse Hp in composite milk samples from cows without any clinical signs of mastitis and quarter milk samples with a weak to strong reaction in the California Mastitis Test (CMT). A commercial ELISA for determination of Hp in milk was used for comparison. The limit of detection (LOD) of the biosensor assay was determined as 1.1 mg/l. Within-assay and between-day variations were determined both with bulk tank milk spiked with human Hp and with composite milk samples containing bovine Hp. Coefficients of variation varied between 3.6 and 8.6% at concentrations between 4.0 and 12 mg/l, respectively. Agreement between the results obtained by the biosensor assay and the ELISA was satisfactory; however, the results obtained by the biosensor were generally lower than the results obtained by the ELISA. Possible explanations for this observation are discussed.  相似文献   
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