全文获取类型
收费全文 | 5570篇 |
免费 | 315篇 |
国内免费 | 15篇 |
专业分类
电工技术 | 45篇 |
综合类 | 1篇 |
化学工业 | 1137篇 |
金属工艺 | 110篇 |
机械仪表 | 128篇 |
建筑科学 | 91篇 |
矿业工程 | 8篇 |
能源动力 | 131篇 |
轻工业 | 906篇 |
水利工程 | 61篇 |
石油天然气 | 25篇 |
无线电 | 232篇 |
一般工业技术 | 682篇 |
冶金工业 | 1778篇 |
原子能技术 | 29篇 |
自动化技术 | 536篇 |
出版年
2024年 | 25篇 |
2023年 | 48篇 |
2022年 | 152篇 |
2021年 | 244篇 |
2020年 | 158篇 |
2019年 | 203篇 |
2018年 | 217篇 |
2017年 | 215篇 |
2016年 | 189篇 |
2015年 | 143篇 |
2014年 | 180篇 |
2013年 | 281篇 |
2012年 | 275篇 |
2011年 | 282篇 |
2010年 | 195篇 |
2009年 | 220篇 |
2008年 | 183篇 |
2007年 | 157篇 |
2006年 | 123篇 |
2005年 | 104篇 |
2004年 | 75篇 |
2003年 | 73篇 |
2002年 | 62篇 |
2001年 | 56篇 |
2000年 | 53篇 |
1999年 | 89篇 |
1998年 | 525篇 |
1997年 | 307篇 |
1996年 | 232篇 |
1995年 | 124篇 |
1994年 | 121篇 |
1993年 | 95篇 |
1992年 | 41篇 |
1991年 | 36篇 |
1990年 | 30篇 |
1989年 | 31篇 |
1988年 | 25篇 |
1987年 | 32篇 |
1986年 | 28篇 |
1985年 | 20篇 |
1984年 | 10篇 |
1983年 | 6篇 |
1982年 | 14篇 |
1981年 | 15篇 |
1980年 | 18篇 |
1979年 | 4篇 |
1977年 | 54篇 |
1976年 | 116篇 |
1975年 | 3篇 |
1974年 | 3篇 |
排序方式: 共有5900条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
A novel dual-rotation bobbin tool friction stir welding (DBT-FSW) was developed, in which the upper shoulder (US) and lower shoulder (LS) have different rotational speeds. This process was tried to weld 3.2 mm thick aluminum-lithium alloy sheets. The metallographic analysis and torque measurement were carried out to characterize the weld formability. Experimental results show that compared to conventional bobbin tool friction stir welding, the DBT-FSW has an excellent process stability, and can produce the defect-free joints in a wider range of welding parameters. These can be attributed to the significant improvement of material flow caused by the formation of a staggered layer structure and the unbalanced force between the US and LS during the DBT-FSW process. 相似文献
5.
Alfredo M. Gravagnuolo Eden Morales‐Narváez Charlene Regina Santos Matos Sara Longobardi Paola Giardina Arben Merkoçi 《Advanced functional materials》2015,25(38):6084-6092
Class I hydrophobin Vmh2, a peculiar surface active and versatile fungal protein, is known to self‐assemble into chemically stable amphiphilic films, to be able to change wettability of surfaces, and to strongly adsorb other proteins. Herein, a fast, highly homogeneous and efficient glass functionalization by spontaneous self‐assembling of Vmh2 at liquid–solid interfaces is achieved (in 2 min). The Vmh2‐coated glass slides are proven to immobilize not only proteins but also nanomaterials such as graphene oxide (GO) and quantum dots (QDs). As models, bovine serum albumin labeled with Alexa 555 fluorophore, anti‐immunoglobulin G antibodies, and cadmium telluride QDs are patterned in a microarray fashion in order to demonstrate functionality, reproducibility, and versatility of the proposed substrate. Additionally, a GO layer is effectively and homogeneously self‐assembled onto the studied functionalized surface. This approach offers a quick and simple alternative to immobilize nanomaterials and proteins, which is appealing for new bioanalytical and nanobioenabled applications. 相似文献
6.
7.
Cypriano G da Trindade Neto Ana LP Fernandes Ana IB Santos Waldenice A Morais Marcos VM Navarro Tereza NC Dantas Mrcia R Pereira Jos LC Fonseca 《Polymer International》2005,54(4):659-666
Complexation of chitosan in aqueous solutions by low molecular weight electrolytes is one of the simplest methods for the preparation of aqueous chitosan dispersions. In this work, the influence of storage time, sulfate concentration, method of preparation and surfactant content on some properties of the resultant chitosan dispersions (turbidity, viscosity and zeta potential) was analyzed. Turbidimetry was adequate to monitor the formation of particles, while viscometry was suitable to monitor changes in the dispersing phase. An analysis of the properties of these systems, mainly in terms of particle–particle and macromolecule–macromolecule interactions was carried out. Copyright © 2004 Society of Chemical Industry 相似文献
8.
Severe symptomatic hypomagnesemia (0.15 mmol/L [0.3 mEq/L]) and hypocalcemia (1.47 mmol/L [5.9 mg/dL]) occurred in a 4-week-old infant coincidental with correction of a severe renal tubular acidosis with alkali therapy. The patient had no evidence of gastrointestinal abnormality and magnesium (Mg) intake was adequate for age and weight. Extreme renal conservation of Mg was observed, supporting the presence of Mg depletion. We suggest that Mg depletion in this infant occurred due to acidosis-induced bone demineralization and that symptomatic hypomagnesemia was precipitated by rapid remineralization accompanying correction of systemic acidosis. This patient represents a novel case of hungry bone syndrome (HBS). Since HBS has not been described previously in patients with acidosis undergoing therapy, several other factors may have contributed to this patient's severe hypomagnesemia, namely, prematurity, twin status, severity of acidosis, rapidity of correction of acidosis, catch-up growth and calcium supplementation. Clinicians should be vigilant for HBS in infants with severe acidosis undergoing alkali therapy. 相似文献
9.
Studies of adults, children, and laboratory animals suggest an association between lead exposure and hearing loss. A causal relationship might direct mandated medical surveillance of lead-exposed workers to include audiometric testing. A cross-sectional, computerized dataset was obtained from a private occupational health screening company to examine the relationship between blood lead level and hearing loss. Audiometry and blood lead results were available for 183 workers. A statistically significant correlation was found between blood lead level and an elevated hearing threshold at 400 Hz (P = 0.03); no other frequencies showed such a correlation. This finding suggests either an interaction between nose exposure and lead, interaction of other exposure factors (such as cigarette smoking), or that factors other than biomechanical ones render the organ of Corti more susceptible at 4000 Hz. Further evaluation of these questions should be undertaken. Computerized databases created for worker surveillance may be a source for data useful for examining other causal connections in occupational settings. 相似文献
10.
A new sub-class of binding protein-dependent transporter with specificity for a broad range of polar amino acids has been identified by sequence comparison, in Rhizobium leguminosarum, Rhodobacter capsulatus, Escherichia coli and Pseudomonas fluorescens. Southern blotting and PCR analysis has shown that transporters from this new sub-class are widely distributed in Gram-negative bacteria, including, in addition to the above, Citrobacter freundii, Erwinia carotovorum and Rhizobium meliloti. ABC transporters of polar amino acids can be divided into two groups: those with narrow solute specificity and the newly identified sub-class with broad solute specificity. The binding and inner membrane proteins from transporters with a broad solute specificity are larger by approximately 30% than those with a narrow solute specificity. Multiple alignment of the inner membrane proteins from all sequenced polar amino acid transporters indicates there is an N-terminal conserved region that may be involved in solute specificity. A conserved arginine or lysine at residue 30 of this region is changed to glutamate in arginine transporters. Residue 53 also has a strong correlation with the charge on the transported solute, with basic amino acid transporters replacing an aliphatic amino acid at this position with a negatively charged amino acid. The general amino acid permease from R. leguminosarum, which will transport aliphatic as well as basic and acidic amino acids, juxtaposes two prolines at residues 52 and 53 of the N-terminal conserved region. 相似文献