全文获取类型
收费全文 | 754篇 |
免费 | 42篇 |
国内免费 | 4篇 |
专业分类
林业 | 34篇 |
农学 | 23篇 |
基础科学 | 1篇 |
207篇 | |
综合类 | 79篇 |
农作物 | 118篇 |
水产渔业 | 58篇 |
畜牧兽医 | 217篇 |
园艺 | 13篇 |
植物保护 | 50篇 |
出版年
2023年 | 2篇 |
2022年 | 12篇 |
2021年 | 24篇 |
2020年 | 16篇 |
2019年 | 25篇 |
2018年 | 17篇 |
2017年 | 17篇 |
2016年 | 27篇 |
2015年 | 32篇 |
2014年 | 26篇 |
2013年 | 46篇 |
2012年 | 58篇 |
2011年 | 73篇 |
2010年 | 26篇 |
2009年 | 14篇 |
2008年 | 42篇 |
2007年 | 40篇 |
2006年 | 40篇 |
2005年 | 32篇 |
2004年 | 31篇 |
2003年 | 30篇 |
2002年 | 25篇 |
2001年 | 23篇 |
2000年 | 22篇 |
1999年 | 14篇 |
1998年 | 6篇 |
1997年 | 2篇 |
1995年 | 2篇 |
1994年 | 4篇 |
1993年 | 4篇 |
1992年 | 3篇 |
1991年 | 5篇 |
1990年 | 4篇 |
1989年 | 11篇 |
1988年 | 5篇 |
1987年 | 3篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1972年 | 2篇 |
1969年 | 4篇 |
1967年 | 1篇 |
1966年 | 1篇 |
1965年 | 2篇 |
1964年 | 3篇 |
1963年 | 1篇 |
排序方式: 共有800条查询结果,搜索用时 46 毫秒
791.
Kwan Woo Kim Keun Hyung Lee Bong Seok Lee Yo Seung Ho Seung Jin Oh Hak Yong Kim 《Fibers and Polymers》2005,6(2):121-126
Semicrystalline poly(ethylene terephthalate) (cPET)/amorphous poly(ethylene terephthalate) with isophthalic acid (aPET) blends
with 100/0, 75/25, 50/50, 25/75, and 0/100 by weight ratios were dissolved in a mixture of trifluoroacetic acid (TFA)/methylene
chloride (MC) (50/50, v/v) and electrospun via the electrospinning technique. Solution properties such as solution viscosity,
surface tension and electric conductivity were determined. The solution viscosity slightly decreased as aPET content increased,
while there was no difference in surface tension with respect to aPET composition. The characteristics of the electrospun
cPET/aPET blend nonwovens were investigated in terms of their morphology, pore size and gas permeability. All these measurements
were carried out before and after heat treatment for various blend weight ratios. The average diameter of the fibers decreased
with increasing aPET composition due to the decrease in viscosity. Also, the morphology of the electrospun cPET/aPET blend
nonwovens was changed by heat treatment. The pore size and pore size distribution varied greatly from a few nanometers to
a few microns. The gas permeability after heat treatment was lower than that before heat treatment because of the change of
the morphology. 相似文献
792.
Silica nanofibers containing silver nanoparticles were successfully prepared using sol-gel chemistry and electro-spinning
technique. Solution of tetraethly orthosilicate in ethanol containing silver nitrate was aged to have sufficient viscosity
and electrospun to form nanofibers. Upon thermal treatment, the gelation reaction between silanols was completed in the prepared
silica nanofibers, and at the same time, silver ions in the nanofiber changed to metallic silver or silver oxides. The reduction
of silver ions could be also achieved by UV irradiation, and the generated silver nanoparticles were present preferentially
on the surface of the silica nanofibers. On testing release behavior of silver ions, it was found that most of silver remained
in the silica nanofiber. The silica nanofibers containing silver nanoparticles exhibited excellent antibacterial and deodorant
properties. 相似文献
793.
The effect of block sequence on the self-assembly of ABC-type triblock copolymers in the ordered state is investigated using
an isothermal-isobaric molecular dynamics simulation. The block sequence has an important effect on the morphology of ABC
triblock copolymers. Different morphologies are observed depending on the block sequence as well as the block composition.
The triblock copolymers with the volume fraction of 1:1:1 (f
A=f
B=f
C=0.33) show the three phase and four layered lamellar structures irrespective of the block sequence. The A32B16C32 triblock copolymer withf
B=0.2 shows a morphology in which cylinders of midblock B are formed at the interface between A and C lamellae, whereas the
morphology of triblock copolymer B16C32A32 and C32A32B16 show a cylindrical core-shell structure and a lamellar type morphology, respectively. The A20B40C20 triblock copolymer with the block B as a major component shows a tricontinuous structure, whereas both B40C20A20 and C20A20B40 triblock copolymers exhibit the lamellar structures. When the block B has larger volume fraction withf
B=0.75, the matrix is composed of block B, and other two blocks A and C form spherical domains. 相似文献
794.
Dyeing and color fastness properties of a reactive disperse dye containing an acetoxyethylsulphone group on PET, Nylon, silk
and N/P fabrics were examined. The reactive disperse dye exhibited almost the same dyeing properties on PET fabric as a conventional
disperse dye except the level of dye uptake. The most appropriate pH and dyeing temperature for the dyeing of Nylon fabric
were 7 and 100°C respectively. The build-up on Nylon fabric was good and various color fastnesses were good to excellent due
to the formation of the covalent bond. Application of the reactive disperse dye on silk fabric at pH 9 and 80°C yielded optimum
color strength. The rate of dyeing on Nylon fabric was faster than that on PET fabric when both fabrics were dyed simultaneously
in a dye bath, accordingly color strength of the dyed Nylon was higher. The reactive disperse dye can be applied for one-step
and one-bath dyeing of N/P mixture fabric with good color fastness. 相似文献
795.
Jeong Ho Park Haan Woo Sung Byung Il Yoon Hyuk Moo Kwon 《Journal of veterinary science (Suw?n-si, Korea)》2009,10(2):131-139
The aim of this study was to examine the efficacy of in ovo prime-boost vaccination against infectious bursal disease virus (IBDV) using a DNA vaccine to prime in ovo followed by a killed-vaccine boost post hatching. In addition, the adjuvant effects of plasmid-encoded chicken interleukin-2 and chicken interferon-γ were tested in conjunction with the vaccine. A plasmid DNA vaccine (pcDNA-VP243) encoding the VP2, VP4, and VP3 proteins of the very virulent IBDV (vvIBDV) SH/92 strain was injected into the amniotic sac alone or in combination with a plasmid encoding chicken IL-2 (ChIL-2) or chicken IFN-γ (ChIFN-γ) at embryonation day 18, followed by an intramuscular injection of a commercial killed IBD vaccine at 1 week of age. The chickens were orally challenged with the vvIBDV SH/92 strain at 3 weeks of age and observed for 10 days. In ovo DNA immunization followed by a killed-vaccine boost provided significantly better immunity than the other options. No mortality was observed in this group after a challenge with the vvIBDV. The prime-boost strategy was moderately effective against bursal damage, which was measured by the bursa weight/body weight ratio, the presence of IBDV RNA, and the bursal lesion score. In ovo DNA vaccination with no boost did not provide sufficient immunity, and the addition of ChIL-2 or ChIFN-γ did not enhance protective immunity. In the ConA-induced lymphocyte proliferation assay of peripheral blood lymphocyte collected 10 days post-challenge, there was greater proliferation responses in the DNA vaccine plus boost and DNA vaccine with ChIL-2 plus boost groups compared to the other groups. These findings suggest that priming with DNA vaccine and boosting with killed vaccine is an effective strategy for protecting chickens against vvIBDV. 相似文献
796.
Jung Min Ryu Dong Hyun Kim Min Young Lee Sang Hun Lee Jae Hong Park Seung Pil Yun Min Woo Jang Seong Hwan Kim Gyu Jin Rho Ho Jae Han 《Journal of veterinary science (Suw?n-si, Korea)》2009,10(2):93-98
The shortage of organ donors has stimulated interest in the possibility of using animal organs for transplantation into humans. In addition, pigs are now considered to be the most likely source animals for human xenotransplantation because of their advantages over non-human primates. However, the appropriate standard values for estimations of the liver of micropigs have not been established. The determination of standard values for the micropig liver using multi-detector row computed tomography (MDCT) would help to select a suitable donor for an individual patient, determine the condition of the liver of the micropigs and help predict patient prognosis. Therefore, we determined the standard values for the livers of micropigs using MDCT. The liver parenchyma showed homogenous enhancement and had no space-occupying lesions. The total and right lobe volumes of the liver were 698.57 ± 47.81 ml and 420.14 ± 26.70 ml, which are 51.74% and 49.35% of the human liver volume, respectively. In micropigs, the percentage of liver volume to body weight was approximately 2.05%. The diameters of the common hepatic artery and proper hepatic artery were 6.24 ± 0.20 mm and 4.68 ± 0.13 mm, respectively. The hepatic vascular system of the micropigs was similar to that of humans, except for the variation in the length of the proper hepatic artery. In addition, the diameter of the portal vein was 11.27 ± 0.38 mm. In conclusion, imaging evaluation using the MDCT was a reliable method for liver evaluation and its vascular anatomy for xenotransplantation using micropigs. 相似文献
797.
Lunasin and BBI (Bowman Birk protease inhibitor) are bioactive soy peptides that have been shown to be effective suppressors of carcinogenesis in in vitro and in vivo model systems. Since they are subject to digestion in the gastrointestinal tract, we investigated here the stabilities of lunasin and BBI to digestion in vitro by simulated intestinal fluid (SIF) and simulated gastric fluid (SGF). Samples containing lunasin and BBI of varying purities were subjected to in vitro digestion by SIF and SGF at different times and analyzed by Western blot. While the pure BBI reaction is stable after SIF and SGF digestions, the purified lunasin from soybean and synthetic lunasin are easily digested after 2 min in both in vitro digestions. In contrast, lunasin from soy protein containing BBI is comparatively stable after SIF and SGF digestions. Both lunasin and BBI are able to internalize into the cell and localize in the nucleus even after digestion, suggesting that some of the peptides are intact and bioactive. These data suggest that BBI plays a role in protecting lunasin from digestion when soy protein is consumed orally. The role of other soy protease inhibitors such as Kunitz Trypsin Inhibitor (KTI) cannot be excluded from these experiments. 相似文献
798.
The gene (lat) encoding L-lysine epsilon-aminotransferase (LAT) in Streptomyces clavuligerus was cloned and expressed in Escherichia coli. Nucleotide sequence analysis of lat predicted a single open reading frame (ORF) of 1371 bp, encoding a polypeptide of 457 amino acids with calculated molecular mass of 49.89 kDa. S. clavuligerus LAT was grouped into aminotransferase subfamily II of alpha family on the basis of sequence homology. A model system composed of the recombinant LAT in phosphate buffer was set up to study the biosynthesis of 2-acetyltetrahydropyridine. Lysine was found to be transformed to 1-piperideine-6-carboxylic acid. 2-Acetyltetrahydropyridine was characterized from the mixture of 1-piperideine-6-carboxylic acid and methylglyoxal. For the first time, we demonstrated that the L-lysine epsilon-aminotransferase is responsible for the formation of 1-piperideine-6-carboxylic acid, which may react with methylglyoxal to generate the acylated N-heterocyclic odorant 2-acetyltetrahydropyridine. 相似文献
799.
Different central manifestations in response to electroacupuncture at analgesic and nonanalgesic acupoints in rats: a manganese-enhanced functional magnetic resonance imaging study 总被引:6,自引:0,他引:6 下载免费PDF全文
Jen-Hwey Chiu Mao-Shu Chung Hui-Cheng Cheng Tzu-Cheng Yeh Jen-Chuen Hsieh Chung-Yen Chang Wan-Yo Kuo Henrich Cheng Low-Tone Ho 《Canadian journal of veterinary research》2003,67(2):94-101
Acupuncture analgesia is an important issue in veterinary medicine. This study was designed to elucidate central modulation effects in response to electroacupuncture (EA) at different acupoints. Manganese-enhanced functional magnetic resonance imaging was performed in Sprague-Dawley rats after sham acupuncture, sham EA, or true EA at somatic acupoints. The acupoints were divided into 3 groups: group 1, analgesic acupoints commonly used for pain relief, such as Hegu (LI 4); group 2, nonanalgesic acupoints rarely used for analgesic effect, such as Neiguan (PC 6); and group 3, acupoints occasionally used for analgesia, such as Zusanli (ST 36). Image acquisition was performed on a 1.5-T superconductive clinical scanner with a circular polarized extremity coil. The results showed that there was no neural activation caused by EA at a true acupoint with shallow needling and no electric current (sham acupuncture). When EA at a true acupoint was applied with true needling but no electric current (sham EA), there was only a slight increase in brain activity at the hypothalamus; when EA was applied at a true acupoint with true needling and an electric current (true EA), the primary response at the hypothalamus was enhanced. Also, there was a tendency for the early activation of pain-modulation areas to be prominent after EA at analgesic acupoints as compared with nonanalgesic acupoints. In conclusion, understanding the linkage between peripheral acupoint stimulation and central neural pathways provides not only an evidence-based approach for veterinary acupuncture but also a useful guide for clinical applications of acupuncture. 相似文献
800.
Mertens Arne Bawin Yves Vanden Abeele Samuel Kallow Simon Swennen Rony Vu Dang Toan Vu Tuong Dang Minh Ho Thi Panis Bart Vandelook Filip Janssens Steven B. 《Genetic Resources and Crop Evolution》2022,69(7):2515-2534
Genetic Resources and Crop Evolution - Collection and storage of crop wild relative (CWR) germplasm is crucial for preserving species genetic diversity and crop improvement. Nevertheless, much of... 相似文献