全文获取类型
收费全文 | 5541篇 |
免费 | 320篇 |
国内免费 | 70篇 |
专业分类
林业 | 299篇 |
农学 | 352篇 |
基础科学 | 62篇 |
973篇 | |
综合类 | 689篇 |
农作物 | 715篇 |
水产渔业 | 508篇 |
畜牧兽医 | 1925篇 |
园艺 | 137篇 |
植物保护 | 271篇 |
出版年
2024年 | 5篇 |
2023年 | 42篇 |
2022年 | 67篇 |
2021年 | 210篇 |
2020年 | 141篇 |
2019年 | 168篇 |
2018年 | 175篇 |
2017年 | 192篇 |
2016年 | 191篇 |
2015年 | 196篇 |
2014年 | 258篇 |
2013年 | 336篇 |
2012年 | 380篇 |
2011年 | 458篇 |
2010年 | 301篇 |
2009年 | 264篇 |
2008年 | 356篇 |
2007年 | 347篇 |
2006年 | 313篇 |
2005年 | 252篇 |
2004年 | 236篇 |
2003年 | 205篇 |
2002年 | 158篇 |
2001年 | 143篇 |
2000年 | 119篇 |
1999年 | 73篇 |
1998年 | 46篇 |
1997年 | 33篇 |
1996年 | 21篇 |
1995年 | 20篇 |
1994年 | 10篇 |
1993年 | 13篇 |
1992年 | 26篇 |
1991年 | 20篇 |
1990年 | 27篇 |
1989年 | 21篇 |
1988年 | 8篇 |
1987年 | 10篇 |
1986年 | 9篇 |
1985年 | 8篇 |
1984年 | 4篇 |
1983年 | 7篇 |
1982年 | 4篇 |
1980年 | 7篇 |
1978年 | 11篇 |
1974年 | 5篇 |
1972年 | 5篇 |
1970年 | 3篇 |
1969年 | 3篇 |
1968年 | 4篇 |
排序方式: 共有5931条查询结果,搜索用时 62 毫秒
991.
PET or PVC wig fibers are usually colored by the dope dyeing method in which the pigment or color master batch is mixed before
the spinning process. However, the colored fibers need to be dyed again to obtain a two-tone color along the longitudinal
fiber direction. In this study, PET and PVC fibers were dyed by the carrier dyeing method using a disperse dye, and the dyeing
behavior was investigated. The fiber was dyed at various carrier and dye concentrations. The dye uptake increased with increasing
carrier concentration or dye concentration. The saturation of the dye uptake was observed in each case. No change of the glass
transition temperature (Tg) was observed in the 1st run of the DSC thermogram, however, a decrease in the value of Tg was observed in the 2nd run performed after the 1st run sample was quenched and re-measured. The reduction in the value of
Tg implies that the carrier acted as a plasticizer in the fiber and enhanced the segmental mobility of the polymer chains. The
dyeing temperature and carrier concentration were varied and the diffusion coefficients of the dye and activation energy were
measured. The activation energy was increased at a higher carrier concentration, because the carrier acted as a plasticizer
and lowered the energy barrier to the penetration of the dye molecule into the polymer chains. 相似文献
992.
A study has been made on the quantification and evaluation of fabric pilling using two-dimensional and three-dimensional hybrid
imaging methods. Two-dimensional imaging method was good for some samples while three-dimensional measurement method for others,
according to the properties of their base fabric. Various image processing techniques as well as three-dimensional data processing
algorithms were applied for the extraction of pills from measured data and a series of shape parameters have been defined
for the objective evaluation of fabric pilling. An evaluation criterion that is compatible with the conventional evaluation
method has been proposed by applying the new evaluation method to the current photographic standards. 相似文献
993.
Sung Ok Sohn So Min Lee Yun Mi Kim Jeong Hyun Yeum Jin Hyun Choi Han Do Ghim 《Fibers and Polymers》2007,8(2):163-167
A durable aroma finishing for PET fabric was carried out by adopting poly(vinyl acetate) (PVAc) nanoparticles containing lavender
oil (LO) in core. Relatively small size of PVAc nanoparticles (ca. 244 nm of mean particle diameter) was expected to resist
the frictional destruction of the particles, which is frequently observed in cases of microcapsules. PVAc nanoparticles containing
LO in core were prepared by emulsification-diffusion method and their application as an aroma releasing agent for PET fabrics
was assessed through the observation of releasing profiles of LO in ethanol for experimental acceleration. Melamine-formaldehyde
(MF) microcapsules containing LO were also prepared and treated on fabrics for comparison. PVAc nanoparticles treated on PET
fabric showed higher initial releasing amount, which was ascribed to the enhanced surface area. After 2 days of releasing,
PET fabric treated with PVAc nanoparticles showed slower and more stable releasing profile and reached about 12 ppm of cumulative
release after 16 days, which was under two thirds of that with MF microcapsules. PVAc nanoparticles can be used as an agent
for durable aroma finishing of PET fabrics. 相似文献
994.
Joonseok Koh Sang-Mo Kang Soo-Jin Kim Min-Kyung Cha Yoon-Jung Kwon 《Fibers and Polymers》2006,7(2):180-185
A pineapple protease, bromelain, was used to improve the dyeing properties of protein fibers such as wool and silk. The optimal
condition for the activity of the pineapple protease was about 60 °C at pH 7. The wool and silk were treated with the protease
extracted from a pineapple and the K/S values of the dyed wool and silk were measured using a spectrophotometer in order to
compare the dye uptake. The protease treatment enhanced the dyeing properties of protein fibers without severe changes in
mechanical properties. The surface appearances of protease-treated fibers were observed by microscopy. 相似文献
995.
Ionic conductivity and mechanical properties of a mixed polymer matrix consisting of poly(ethylene glycol) (PEG) and cyanoresin
type M (CRM) with various lithium salts and plasticizer were examined. The CRM used was a copolymer of cyanoethyl pullulan
and cyanoethyl poly(vinyl alcohol) with a molar ratio of 1:1, mixed plasticizer was ethylene carbonate (EC) and propylene
carbonate (PC) at a volume ratio of 1:1. The conductive behavior of polymer electrolytes in the temperature range of 298∼338
K was investigated. The PEG/LiClO4 complexes exhibited the highest ionic conductivity of ∼10−5 S/cm at 25°C with the salt concentration of 1.5 M. In addition, the plasticized PEG/LiClO4 complexes exhibited improvement of ionic conductivity. However, their complexes showed decreased mechanical properties. The
improvement of ionic conductivity and mechanical properties could be obtained from the polymer electrolytes by using CRM.
The highest ionic conductivity of PEG/CRM/LiClO4/(EC-PC) was 5.33×10−4 S/cm at 25°C. 相似文献
996.
Polylactide(PLA) films were drawn at various drawing temperature of 65, 90 and 120 °C. The effects of drawing temperature on structural conformation and properties of PLA films were investigated. It was confirmed that the PLA films at drawing temperature of 65 and 90 °C were composed of α′ phase crystal form. The strain-induced crystallization and molecular orientation increased with increasing the draw ratio, which result in improving the mechanical and thermal properties of α′ phase PLA films. However, at drawing temperature of 120 °C, the strain-induced crystallization and molecular orientation of PLA films were not distinctly detected. It was supposed that the rate of the chain relaxation was faster than chain orientation and strain-induced crystallization during uniaxial drawing process. 相似文献
997.
The self-assembly of asymmetric ABC triblock copolymers in the ordered structure is investigated using an isothermal-isobaric
molecular dynamics simulation. Unlike symmetric ABC triblock copolymers, more fascinating morphologies are observed in asymmetric
ones because of a larger difference of incompatibility between the components. Various modes of self-assembly in assymmetric
ABC triblock copolymers are also observed depending on the block composition. When the composition of block A is changed from
0.125 to 0.25 at the samef
B
=0.25, the morphological transition from the “cylinder in cylinder” to “cylinders at cylinder” structure is observed in the
simulation. In the case of ABC triblocks withf
B
=0.5, a lamellar-type structure is changed to a cylinder-type structure with increasing the length of block A. When the mid-block
length increases further tof
B
=0.625, the “spheres on cylinder” structure is observed in both the A10B50C20 and A20B50C10 triblocks. From these results, the phase diagram of ABC triblock copolymers can be constructed.
Dedicated to Professor Won-Jei Cho on the occasion of his retirement. 相似文献
998.
SiO2对改性生物质焦理化特性的影响 总被引:1,自引:1,他引:0
为了探索SiO2对改性生物质焦理化特性的影响,以稻秆、棉秆、稻壳作为原料,在600℃下热解制备生物质焦;焦样再经不同温度下NH3/CO2高温气态改性后获得对CO2具有高选择性的富氮生物质焦。采用傅立叶红外光谱分析改性前后生物质焦的表面官能团结构,利用ASAP2020自动吸附仪测量其常温变压下的CO2吸附量,并结合X射线荧光光谱对热解焦的灰成分进行分析,探讨不同原料的生物质焦改性过程中,其理化特性的演变。研究表明,生物质焦灰分中过高的SiO2会阻碍其高温下CO2的活化作用及NH3的氨化作用;焦样灰分中的SiO2含量越低,其改性效果越理想。 相似文献
999.
Hur J Choi YY Park JH Jeon BW Lee HS Kim AR Lee JH 《Canadian journal of veterinary research》2011,75(1):49-56
Salmonella enterica subsp. enterica serovar Typhimurium was isolated from diarrheic piglets in 2 periods, 2000-2001 (n = 25) and 2005-2006 (n = 17). To compare the characteristics of the isolates collected during the 2 periods, all isolates were tested for antimicrobial resistance, the presence of virulence genes, and pulsed-field gel electrophoresis (PFGE) patterns. All 42 isolates were resistant to at least 1 of the 20 antimicrobials tested, and 39 (93%) were resistant to 2 or more antimicrobials. One isolate was resistant to 12 antimicrobials. Profiles of antimicrobial resistance revealed 20 resistance types. Several isolates were also resistant to quinolones and expanded-spectrum cephalosporins. Ten isolates (24%) were resistant to ampicillin, chloramphenicol, streptomycin, sulfonamides, and tetracycline (ACSSuT); only one isolate had been isolated in 2000-2001, indicating that this type of resistance has rapidly disseminated. Polymerase chain reaction (PCR) assays revealed that all the isolates carried invA. Among the 25 strains isolated in 2000-2001, all carried the sipA, sopA, sopD, sopE2, and ssaR genes, and 96% carried sopB and sifA. Among the 17 strains isolated in 2005-2006, all carried sifA, and approximately 90% carried sipA, sopA, sopB, sopD, sopE2, and ssaR. However, only 6 (14%) of the 42 isolates carried spvC. By PFGE analysis, all 42 strains were classified into 4 major clusters, basically by collection period. The genetic similarity according to PFGE suggests that the strains isolated from diarrheic piglets of this region within the same period may be closely related. 相似文献
1000.
Nam SM Hwang IK Yi SS Yoo KY Park OK Yan B Song W Won MH Yoon YS Seong JK 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2011,73(8):1037-1042
In this study, we investigated the effects of treadmill exercise on calretinin (CR), a marker of early postmitotic neurons, immunoreactivity in the dentate gyrus (DG) of Zucker diabetic fatty (ZDF) rats, before or after diabetes onset, and Zucker lean control (ZLC) rats. For this study, 6-week-old ZLC and prediabetic ZDF rats, and 22-week-old ZLC and ZDF rats were exercised on the treadmill. Sedentary ZLC and ZDF rats of the same age were used as exercise experiment controls. The exercised prediabetic ZDF rats did not show diabetes onset, while the sedentary prediabetic ZDF rats showed significantly increased blood glucose levels. The exercised diabetic ZDF rats exhibited a decrease in their blood glucose levels compared to the sedentary diabetic ZDF rats, but the levels were still above 20 mmol/l. ZLC rats of both ages were in the normoglycemic range. CR immunoreactivity was detected throughout the DG, including the subgranular zone and the polymorphic layer. Diabetic rats exhibited a significant decrease in the number of CR-immunoreactive cells and fibers in the DG. Exercise in the prediabetic ZDF rats significantly increased the number of CR-immunoreactive cells and fibers in the subgranular zone of the DG. In the ZLC and ZDF rats of chronic diabetic phase, exercise increased CR-immunoreactive neurons in the hilar region. These results suggest that diabetes significantly reduces the number of postmitotic CR-immunoreactive neurons and the intensity of immunoreactivity and that exercise increases these CR-related parameters in a diabetic stage-dependent manner. 相似文献