全文获取类型
收费全文 | 11849篇 |
免费 | 549篇 |
国内免费 | 65篇 |
专业分类
电工技术 | 496篇 |
综合类 | 35篇 |
化学工业 | 2992篇 |
金属工艺 | 274篇 |
机械仪表 | 315篇 |
建筑科学 | 357篇 |
矿业工程 | 13篇 |
能源动力 | 717篇 |
轻工业 | 1148篇 |
水利工程 | 103篇 |
石油天然气 | 159篇 |
武器工业 | 4篇 |
无线电 | 1219篇 |
一般工业技术 | 2244篇 |
冶金工业 | 551篇 |
原子能技术 | 204篇 |
自动化技术 | 1632篇 |
出版年
2023年 | 201篇 |
2022年 | 470篇 |
2021年 | 645篇 |
2020年 | 428篇 |
2019年 | 444篇 |
2018年 | 562篇 |
2017年 | 398篇 |
2016年 | 487篇 |
2015年 | 314篇 |
2014年 | 482篇 |
2013年 | 833篇 |
2012年 | 637篇 |
2011年 | 725篇 |
2010年 | 519篇 |
2009年 | 500篇 |
2008年 | 507篇 |
2007年 | 421篇 |
2006年 | 382篇 |
2005年 | 291篇 |
2004年 | 269篇 |
2003年 | 266篇 |
2002年 | 262篇 |
2001年 | 135篇 |
2000年 | 142篇 |
1999年 | 138篇 |
1998年 | 193篇 |
1997年 | 165篇 |
1996年 | 130篇 |
1995年 | 136篇 |
1994年 | 102篇 |
1993年 | 105篇 |
1992年 | 93篇 |
1991年 | 74篇 |
1990年 | 60篇 |
1989年 | 88篇 |
1988年 | 60篇 |
1987年 | 63篇 |
1986年 | 49篇 |
1985年 | 80篇 |
1984年 | 70篇 |
1983年 | 72篇 |
1982年 | 57篇 |
1981年 | 49篇 |
1980年 | 44篇 |
1979年 | 45篇 |
1978年 | 41篇 |
1977年 | 37篇 |
1976年 | 38篇 |
1975年 | 24篇 |
1974年 | 23篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
Thermal modeling of plasma spray deposition of nanostructured ceramics 总被引:12,自引:0,他引:12
A thermal model for plasma spray deposition of ceramic materials onto metallic substrates has been developed. The enthalpy-based
control volume formulation of the heat transfer processes has been used to study the temperature evolution in a two-dimensional
substrate and in the coating as it is grown. In this paper, additional melting of ceramic splats after deposition is examined,
with a view to predicting the retention of nanostructures in a spray consisting of agglomerated, nanometer-sized particles.
Initial results for thin coatings indicate that when the mean temperature of the incoming particles is close to the fusion
point of the ceramic material, the nanostructure distribution in the coating is largely determined by the composition of the
spray. However, with thicker coatings, additional melting due to prolonged plasma gas heating combined with increased thermal
resistance in the underlying coating leads to a loss of nanostructure. 相似文献
992.
Yuichiro Nagatsu Takashi Ogawa Yoshihito Kato Yutaka Tada 《American Institute of Chemical Engineers》2009,55(3):563-580
The reacting flow fields in reactive miscible viscous fingering in a Hele‐Shaw cell studied by Nagatsu and Ueda had not been completely elucidated, mainly because one cannot exactly recognize where and when the reaction takes place in the reactive fingering pattern. We developed a novel experimental method that allowed us to identify the reaction region in the fingering pattern employed in the previous studies. The novel method involves switching of the less‐viscous liquid injected in both the nonreactive and reactive experiments. By using the novel method, we succeeded in showing how the reaction region in the fingering pattern was affected by the initial reactant concentrations, the Péclet number, and time. We propose physical models of the reacting flow field in the cell's gap direction that can explain the obtained experimental results. © 2009 American Institute of Chemical Engineers AIChE J, 2009 相似文献
993.
Carlos H. Herrera-Mendez Samira Becila Gerald Coulis Miguel A. Sentandreu Laurent Aubry Ahmed Ouali 《Food research international (Ottawa, Ont.)》2010,43(1):356-363
Thrombin/antithrombin III (AT-III) proteolytic system is well known for its function in blood coagulation. Thrombin is expressed in skeletal muscle but nothing is known about the presence of AT-III in the tissue. In postmortem muscle this system has been and is still totally ignored. We therefore successfully attempted to purify AT-III from bovine skeletal muscle and characterized the purified protein (identified as AT-III by N-ter sequencing and mass spectrometry finger print) for its physicochemical and inhibitory properties. As the human blood serpin, muscle AT-III is thermolabile and stable only at alkaline pH (pH 9–10). The muscle serpin inhibits strongly thrombin in a heparin dependent manner and trypsin. Phosphatidylserine (PS) externalization demonstrated in the present work suggested that prothrombin can be activated to thrombin through binding of the activator complex on the external PS groups. PS externalization is concomitant with shrinkage of muscle fibers indicating that muscle cells are engaged in the cell death program known as apoptosis few minutes after death. We then discussed the potential role of this proteolytic system in postmortem apoptosis development as well as in the control of low voltage electrical stimulation efficiency. 相似文献
994.
Houssni El-Saied Altaf H. Basta Adly A. Hanna Ahmed M. El-Sayed 《Polymer-Plastics Technology and Engineering》2013,52(5):1095-1105
Metal chelates of three grades of carboxymethyl cellulose (CMC) (LI-L3) with Cu(II) ions, either originating from CuCl2 or CuSO4, were prepared and characterized by elemental analysis, infrared spectra, and electrical conductivity studies. The results showed that the degree of substitution of CMCs and the origin of the Cu(II) ion have a profound effect on the amount of metal included in the polymer complexes and the structure and the electrical conductivity of the prepared complexes. CMC acts as a uninegatively charged bidentate ligand when it is chelated with Cu(II) of CuCl2 via the carboxymethyl group and exhibits the formula Cu(L)2, whereas it acts as a binegatively charged bitentate ligand when it is chelated with CuSO4 via the carboxymethyl and secondary hydroxyl groups and exhibits the formula CuL.2H2O. The investigation revealed that the electrical conductivity depends on the temperature and has two maximum peaks. The values of the activation energy for the conductivity of CMC and their complexes indicated that the samples changed from a low-semiconductor to a high-semiconductor property with heating. It is found that CMC-Cu(II) complexes formed from CuSO4 exhibit a high-semiconductor property compared to complexes derived from CuCl2. 相似文献
995.
Adduct formation of 2-thenoyltrifluoroacetonato(tta) lantha-num(III), europium(III), and ytterbium(I II) with α-pheny 1 1 actic, α-methoxy phenyl acetic, salicylic, and o-methoxy benzoic acids in chloroform has been studied by solvent extraction technique. It has been found that 1anthanoid(111) chelates form more stable adducts with these carboxylic acids in the sequence: Yb(tta)3 < Eu(tta) 3 < La(tta) 3. The adduct formation constants as well as the separation factors obtained as the ratio of the constants between a pair of metals are the largest for α-phenyl lactic acid among these acids. The characteristics with α-phenyl 1actic acid would be caused by the action as bidentate unlike benzoic acid derivatives which work as monodentates owing to the internal complexa-tion through hydrogen bonding. 相似文献
996.
Ghareb M. Soliman Gihan Fetih Ahmed M. Abbas 《Drug development and industrial pharmacy》2017,43(3):399-408
Objective: The objective of this study is to develop and characterize in situ thermosensitive gels for the vaginal administration of sildenafil as a potential treatment of endometrial thinning occurring as a result of using clomiphene citrate for ovulation induction in women with type II eugonadotrophic anovulation. While sildenafil has shown promising results in the treatment of infertility in women, the lack of vaginal pharmaceutical preparation and the side effects associated with oral sildenafil limit its clinical effectiveness.Methods: Sildenafil citrate in situ forming gels were prepared using different grades of Pluronic® (PF-68 and PF-127). Mucoadhesive polymers as sodium alginate and hydroxyethyl cellulose were added to the gels in different concentrations and the effect on gel properties was studied. The formulations were evaluated in terms of viscosity, gelation temperature (Tsol-gel), mucoadhesion properties, and in vitro drug release characteristics. Selected formulations were evaluated in women with clomiphene citrate failure due to thin endometrium (Clinicaltrial.gov identifier NCT02766725).Results: The Tsol-gel decreased with increasing PF-127 concentration and it was modulated by addition of PF-68 to be within the acceptable range of 28–37?°C. Increasing Pluronic® concentration increased gel viscosity and mucoadhesive force but decreased drug release rate. Clinical results showed that the in situ sildenafil vaginal gel significantly increased endometrial thickness and uterine blood flow with no reported side effects. Further, these results were achieved at lower frequency and duration of drug administration.Conclusion: Sildenafil thermosensitive vaginal gels might result in improved potential of pregnancy in anovulatory patients with clomiphene citrate failure due to thin endometrium. 相似文献
997.
Raayaa Wananuruksawong Yutaka Shinoda Takashi Akatsu Fumihiro Wakai 《International Journal of Applied Ceramic Technology》2013,10(5):756-763
Creep behavior of Si3N4 polycrystals containing Y2O3‐MgO‐SiO2 glass phase (with and without Calcium oxide [CaO] additive) was studied by compression tests between 1500 and 1700°C. We studied the effect of CaO additive on flow stress, microstructural evolutions, and thermal stability of the intergranular glass phase during deformation. While the addition of CaO did not affect grain size, the flow stress decreased with the amount of CaO. This result suggested that the addition of CaO reduced the viscosity of intergranular glass phase. The addition of CaO further improved the thermal stability of the glass phase by suppressing the evaporation at elevated temperatures. 相似文献
998.
In this study carbon fibers of various morphologies have been synthesized by the decomposition of acetylene over copper supported catalysts (Cu(NO3)2/TiO2, at 250 °C). In order to investigate the relationship between the morphologies of the copper catalyst particle and that of the carbon fiber extruded, tilting procedures (±60 A axis and ±30 B axis) under TEM (120 kV) were performed. In this way a 3-D (rather than a 2-D) image of the Cu crystallites were obtained which permitted for the 3-D shape of the Cu catalyst particle to be linked to the morphology of the extruded carbon fiber. Whereby copper particles that give distorted decahedra are apt to form helical fibers, trigonal bi-pyramidal particles give linear fibers. Various plate-like particles were also investigated, and it was observed that as the number of sides varied (3, 4, 5 or 6) there was a corresponding change in the carbon fiber helicity. Herein we report on our findings that reveal the geometric structures involved in controlling the shape of morphologically diverse carbon coils, illustrating the influential role catalyst particle shape plays in carbon fiber synthesis. 相似文献
999.
In this paper, we introduce a new approach to the method of non-parametric adaptive spectral analysis by using the Amplitude and Phase Estimation (APES) method, and taking into account the small sample errors of the sample covariance matrix. This approach is referred to as Adaptive Tuning Amplitude and Phase Estimation method (ATAPES). The main advantage of the ATAPES algorithm is its elimination of biased estimation exists with APES method, which is a biased peak location and corresponding problem of the biased amplitude estimation. The ATAPES method provides more accurate peak location and amplitude estimation with higher resolution than APES method. 相似文献
1000.
Masao Kubo Takashi Matsubara Satoshi Shimizu Hiroshi Sato 《Artificial Life and Robotics》2010,15(2):207-211
In this article, a new localization approach for a team of robots that use the emergent properties of their formation is proposed.
Synchronized behavior sometimes generates spin-off effects that include geometric patterns. The question then arises as to
whether it is possible to use these patterns for something important for robots. In this article, Takayama’s control strategy,
which is a target enclosure formation, is discussed. A simple and useful expansion of Monte Carlo localization by the emergent
pattern is proposed. The proposed algorithms are confirmed through a series of computer simulations. 相似文献