全文获取类型
收费全文 | 1327篇 |
免费 | 38篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 17篇 |
综合类 | 2篇 |
化学工业 | 167篇 |
金属工艺 | 25篇 |
机械仪表 | 13篇 |
建筑科学 | 42篇 |
矿业工程 | 4篇 |
能源动力 | 42篇 |
轻工业 | 118篇 |
水利工程 | 10篇 |
石油天然气 | 4篇 |
无线电 | 139篇 |
一般工业技术 | 265篇 |
冶金工业 | 273篇 |
原子能技术 | 3篇 |
自动化技术 | 243篇 |
出版年
2023年 | 5篇 |
2022年 | 16篇 |
2021年 | 26篇 |
2020年 | 21篇 |
2019年 | 39篇 |
2018年 | 35篇 |
2017年 | 22篇 |
2016年 | 25篇 |
2015年 | 26篇 |
2014年 | 37篇 |
2013年 | 83篇 |
2012年 | 51篇 |
2011年 | 66篇 |
2010年 | 63篇 |
2009年 | 58篇 |
2008年 | 72篇 |
2007年 | 73篇 |
2006年 | 44篇 |
2005年 | 54篇 |
2004年 | 35篇 |
2003年 | 29篇 |
2002年 | 35篇 |
2001年 | 29篇 |
2000年 | 25篇 |
1999年 | 20篇 |
1998年 | 17篇 |
1997年 | 21篇 |
1996年 | 17篇 |
1995年 | 30篇 |
1994年 | 25篇 |
1993年 | 22篇 |
1992年 | 18篇 |
1991年 | 8篇 |
1990年 | 20篇 |
1989年 | 11篇 |
1988年 | 17篇 |
1987年 | 17篇 |
1986年 | 19篇 |
1985年 | 17篇 |
1984年 | 16篇 |
1983年 | 14篇 |
1982年 | 12篇 |
1981年 | 12篇 |
1980年 | 11篇 |
1979年 | 9篇 |
1978年 | 6篇 |
1977年 | 7篇 |
1975年 | 5篇 |
1974年 | 7篇 |
1973年 | 6篇 |
排序方式: 共有1367条查询结果,搜索用时 0 毫秒
51.
Sahana Gopal Ciro Chiappini Jelle Penders Vincent Leonardo Hyejeong Seong Stephen Rothery Yuri Korchev Andrew Shevchuk Molly M. Stevens 《Advanced materials (Deerfield Beach, Fla.)》2019,31(12)
Owing to their ability to efficiently deliver biological cargo and sense the intracellular milieu, vertical arrays of high aspect ratio nanostructures, known as nanoneedles, are being developed as minimally invasive tools for cell manipulation. However, little is known of the mechanisms of cargo transfer across the cell membrane‐nanoneedle interface. In particular, the contributions of membrane piercing, modulation of membrane permeability and endocytosis to cargo transfer remain largely unexplored. Here, combining state‐of‐the‐art electron and scanning ion conductance microscopy with molecular biology techniques, it is shown that porous silicon nanoneedle arrays concurrently stimulate independent endocytic pathways which contribute to enhanced biomolecule delivery into human mesenchymal stem cells. Electron microscopy of the cell membrane at nanoneedle sites shows an intact lipid bilayer, accompanied by an accumulation of clathrin‐coated pits and caveolae. Nanoneedles enhance the internalization of biomolecular markers of endocytosis, highlighting the concurrent activation of caveolae‐ and clathrin‐mediated endocytosis, alongside macropinocytosis. These events contribute to the nanoneedle‐mediated delivery (nanoinjection) of nucleic acids into human stem cells, which distribute across the cytosol and the endolysosomal system. This data extends the understanding of how nanoneedles modulate biological processes to mediate interaction with the intracellular space, providing indications for the rational design of improved cell‐manipulation technologies. 相似文献
52.
No doubt that chlorination has been successfully used for the control of water borne infections diseases for more than a century. However identification of chlorination byproducts (CBPs) and incidences of potential health hazards created a major issue on the balancing of the toxicodynamics of the chemical species and risk from pathogenic microbes in the supply of drinking water. There have been epidemiological evidences of close relationship between its exposure and adverse outcomes particularly the cancers of vital organs in human beings. Halogenated trihalomethanes (THMs) and haloacetic acids (HAAs) are two major classes of disinfection byproducts (DBPs) commonly found in waters disinfected with chlorine. The total concentration of trihalomethanes and the formation of individual THM species in chlorinated water strongly depend on the composition of the raw water, on operational parameters and on the occurrence of residual chlorine in the distribution system. Attempts have been made to develop predictive models to establish the production and kinetics of THM formations. These models may be useful for operational purposes during water treatment and water quality management. It is also suggested to explore some biomarkers for determination of DBP production. Various methods have been suggested which include adsorption on activated carbons, coagulation with polymer, alum, lime or iron, sulfates, ion exchange and membrane process for the removal of DBPs. Thus in order to reduce the public health risk from these toxic compounds regulation must be inforced for the implementation of guideline values to lower the allowable concentrations or exposure. 相似文献
53.
Antibiotic susceptibility profiles of new probiotic Lactobacillus and Bifidobacterium strains 总被引:3,自引:0,他引:3
The antimicrobial susceptibilities and presence of plasmids in four new probiotic lactic acid bacteria (LAB) strains, Lactobacillus rhamnosus HN001 (DR20) HN067, Lactobacillus acidophilus HN017 and Bifidobacterium lactis HN019 (DR10), were determined. Resistance to 18 commonly used antibiotics was assessed by disk diffusion. The three Lactobacillus strains had similar antibiotic susceptibility profiles to those of Lactobacillus plantarum strain HN045 and two commercial probiotic Lactobacillus strains, GG and LA-1. The B. lactis strain HN019 had a similar profile to three commercial probiotic B. lactis strains (Bb12, HN049 and HN098). All 10 strains were sensitive to the Gram-positive spectrum antibiotics erythromycin and novobiocin, the broad-spectrum antibiotics rifampicin, spectinomycin, tetracycline and chloramphenicol and the beta-lactam antibiotics penicillin, ampicillin and cephalothin. By contrast, most strains were resistant to the Gram-negative spectrum antibiotics fusidic acid, nalidixic acid and polymyxin B and the aminoglycosides neomycin, gentamicin, kanamycin and streptomycin. All three L. rhamnosus strains (HN001, HN067 and GG) were resistant to vancomycin and several strains were also resistant to cloxacillin. Of the four new probiotic strains, only L. rhamnosus HN001 contained plasmids; however, a plasmid-free derivative of HN001 had the same antibiotic susceptibility profile as the parent strain. 相似文献
54.
Silberg Judy L.; Erickson Marilyn T.; Meyer Joanne M.; Eaves Lindon J.; Rutter Michael L.; Hewitt John K. 《Canadian Metallurgical Quarterly》1994,62(3):510
The application of structural equation modeling to twin data is used to assess the impact of genetic and environmental factors on children's behavioral and emotional functioning. The models are applied to the maternal ratings of behavior of a subsample of 515 monozygotic and 749 dizygotic juvenile twin pairs, ages 8 through 16 yrs, obtained through mailed questionnaires as part of the Medical College of Virginia Adolescent Behavioral Development Twin Project. The importance of genetic, shared, and specific environmental factors for explaining variation is reported for both externalizing and internalizing behaviors, as well as significant differences in the causes of variation in externalizing behaviors among young boys and girls. The usefulness of applying structural equation models to data on monozygotic and dizygotic twins and the potential implications for addressing clinically relevant questions regarding the causes of psychopathology are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
55.
Ceramic Powder Synthesis by Spray Pyrolysis 总被引:12,自引:0,他引:12
Gary L. Messing Shi-Chang Zhang Gopal V. Jayanthi 《Journal of the American Ceramic Society》1993,76(11):2707-2726
A variety of spray pyrolysis (SP) techniques have been developed to directly produce ceramic powders from solutions. This paper reviews the current status of these processes in terms of the process parameters that enable the formation of particles with controlled morphology and composition. A model incorporating solute diffusion in the droplet and solvent evaporation from the droplet surface is presented to establish the critical parameters leading to solid particle formation. The model illustrates that solid particles can be obtained if solutes with high solubility and a large difference between the critical supersaturation and equilibrium concentration are used and if the process is designed to avoid solvent boiling. It is demonstrated that mixed metal oxide, non-oxide, and composite particles that are solid, hollow, porous, or fibrous can be produced by modifying the precursor characteristics, solution properties, and process parameters. The physical and chemical flexibility of SP processes offers numerous opportunities for the controlled synthesis of advanced ceramic powders and films. However, production rates are limited by the need to produce < 5-μm-diameter droplets and to avoid subsequent droplet coagulation. Developments in process controls, atomization, and system design are required for wider commercialization of SP-type processes. 相似文献
56.
Louise M. Canfield Judy M. Hopkinson Anne F. Lima Gail S. Martin Kyoto Sugimoto Jeanne Burr Larry Clark Daniel L. McGee 《Lipids》1990,25(7):406-411
A quantitative method was developed for the assay of vitamin K in human colostrum and milk. The procedure combines preparative
and analytical chromatography on silica gel in a nitrogen atmosphere followed by reversed phase high performance liquid chromatography
(HPLC). Two HPLC steps were used: gradient separation with ultraviolet (UV) detection followed by isocratic separation detected
electrochemically. Due to co-migrating impurities, UV detection alone is insufficient for identification of vitamin K. Exogenous
vitamin K was shown to equilibrate with endogenous vitamin K in the samples. A statistical method was incorporated to control
for experimental variability. Vitamin K1 was analyzed in 16 pooled milk samples from 7 donors and in individual samples from 15 donors at 1 month post-partrum. Vitamin
K1 was present at 2.94±1.94 and 3.15±2.87 ng/mL in pools and in individuals, respectively. Menaquinones, the bacterial form
of the vitamin, were not detected. The significance of experimental variation to studies of vitamin K in individuals is discussed. 相似文献
57.
Mixing time studies have been carried in a 0.3m diameter and 0.9m tall vessel equipped with three impellers. Conductivity measurement technique has been used for the measurements of mixing time. Effect of the various parameters i.e. tracer density, tracer volume, speed of rotation and impeller combination on mixing time has been studied for two impeller combinations used viz. PTD‐PTD‐PTD and PTD‐PTD‐DT. A compartment model (with one fitted parameter, the exchange flow rate QE) with single compartment per agitation stage has been used to predict the conductivity response and the exchange coefficients are calculated from the model parameter. An attempt has been made to explain the experimental results on the basis of the liquid phase axial dispersion coefficient and cell residence time, calculated from the model parameter QE 相似文献
58.
Safren Steven A.; O'Cleirigh Conall; Tan Judy Y.; Raminani Sudha R.; Reilly Laura C.; Otto Michael W.; Mayer Kenneth H. 《Canadian Metallurgical Quarterly》2009,28(1):1
Objective: To evaluate cognitive-behavioral therapy to enhance medication adherence and reduce depression (CBT-AD) in individuals with HIV. Design: A two arm, randomized, controlled, cross-over trial comparing CBT-AD to enhanced treatment as usual only (ETAU). ETAU, which both groups received, included a single-session intervention for adherence and a letter to the patient's provider documenting her or his continued depression. The intervention group also received 10 to 12 sessions of CBT-AD. Main Outcome Measures: Adherence to antiretroviral therapy as assessed by Medication Event Monitoring Systems (MEMs) and depression as assessed by blinded structured evaluation. Results: At the acute outcome assessment (3-months), those who received CBT-AD evidenced significantly greater improvements in medication adherence and depression relative to the comparison group. Those who were originally assigned to the comparison group who chose to cross over to CBT-AD showed similar improvements in both depression and adherence outcomes. Treatment gains for those in the intervention group were generally maintained at 6- and 12-month follow-up assessments. By the end of the follow-up period, those originally assigned CBT-AD demonstrated improvements in plasma HIV RNA concentrations, though these differences did not emerge before the cross-over, and hence there were not between-groups differences. Conclusions: CBT-AD is a potentially efficacious approach for individuals with HIV struggling with depression and adherence. Replication and extension in larger efficacy trials are needed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
59.
Lie‐Chien Lin Tzu‐Su Li Judy P. Kiang 《Quality and Reliability Engineering International》2009,25(5):551-569
During the recent years, the major driving forces of customer preference, vehicle safety, environmental protection, and flat demand for new cars led to a proliferation of car models and associated price reduction in the auto supply chain. To react to the complex and competitive environment, auto suppliers are urgent to conduct continual improvement (CI) in an effective and systematic way. Thus, this paper presents a framework for CI. The Integrated Development System is proposed to integrate both capability maturity model integration and six‐sigma approach. By implementing the framework, an automaker can establish a solid process‐based management system, identify critical processes, and optimize these processes. For demonstrating the application of this framework, a case study is presented and the result shows that all expected processes' performance targets are achieved, which has dramatically improved by 70% compared with the past records. Apparently, the proposed framework would act as a useful reference to improve an organization's process maturity. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
60.