全文获取类型
收费全文 | 6738篇 |
免费 | 2858篇 |
国内免费 | 144篇 |
专业分类
林业 | 137篇 |
农学 | 536篇 |
基础科学 | 58篇 |
1680篇 | |
综合类 | 379篇 |
农作物 | 147篇 |
水产渔业 | 2054篇 |
畜牧兽医 | 2919篇 |
园艺 | 11篇 |
植物保护 | 1819篇 |
出版年
2024年 | 16篇 |
2023年 | 34篇 |
2022年 | 40篇 |
2021年 | 148篇 |
2020年 | 506篇 |
2019年 | 933篇 |
2018年 | 822篇 |
2017年 | 884篇 |
2016年 | 690篇 |
2015年 | 643篇 |
2014年 | 602篇 |
2013年 | 871篇 |
2012年 | 986篇 |
2011年 | 603篇 |
2010年 | 542篇 |
2009年 | 258篇 |
2008年 | 269篇 |
2007年 | 128篇 |
2006年 | 124篇 |
2005年 | 129篇 |
2004年 | 107篇 |
2003年 | 100篇 |
2002年 | 94篇 |
2001年 | 91篇 |
2000年 | 100篇 |
1999年 | 9篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1988年 | 1篇 |
排序方式: 共有9740条查询结果,搜索用时 15 毫秒
81.
82.
Yoshinobu Uemoto Masayuki Takeda Atushi Ogino Kazuhito Kurogi Shinichro Ogawa Masahiro Satoh Fuminori Terada 《Animal Science Journal》2020,91(1)
The objectives of this study were to estimate genetic parameters and to perform a genome‐wide association study (GWAS) for predicted methane‐related traits in Japanese Black steers. The methane production and yield traits were predicted using on‐farm measurable traits, such as dry matter intake and average daily gain. A total of 4,578 Japanese Black steers, which were progenies of 362 sires genotyped with imputed 551,995 single nucleotide polymorphisms (SNPs), had phenotypes of predicted methane‐related traits during the total fattening period (52 weeks). For the estimation of genetic parameters, the estimated heritabilities were moderate (ranged from 0.57 to 0.60). In addition, the estimated genetic correlations of methane production traits with most of carcass traits and feed‐efficiency traits were unfavorable, but those of methane yield traits were favorable or low. For the GWAS, no genome‐wide significant SNP was detected, but a total of four quantitative trait locus (QTL) regions that explained more than 5.0% of genetic variance were localized on the genome, and some candidate genes associated with growth and feed‐efficiency traits were located on the regions. Our results suggest that the predicted methane‐related traits are heritable and some QTL regions for the traits are localized on the genome in Japanese Black steers. 相似文献
83.
Masato MIYAKE Shinichiro HAYASHI Yoshikazu TAKETA Shunsuke IWASAKI Kouichi WATANABE Shyuich OHWADA Hisashi ASO Takahiro YAMAGUCHI 《Animal Science Journal》2010,81(2):223-229
Myostatin (MSTN) is a negative regulator during muscle differentiation, whereas insulin‐like growth factors (IGFs) are essential for muscle development. MSTN and IGFs act oppositely during myogenesis, but there is little information on the mutual relationship of MSTN and IGFs. The present study was conducted to examine whether MSTN affects IGF expression during early myogenesis in cattle. IGF‐1 mRNA was similarly expressed in M. longissimus thoracis of double‐muscled (DM) and normal (NM) Japanese shorthorn cattle. IGF‐2 mRNA expression was consistently higher in the normal and regenerating muscle of DM cattle than those of NM cattle. When myoblasts were isolated from regenerating M. longissimus thoracis, IGF‐2 mRNA expression showed a significant increase in differentiating DM derived myoblasts (DM‐myoblasts) as compared with differentiating NM derived myoblasts (NM‐myoblasts). An addition of recombinant mouse myostatin (rMSTN) to myoblast cultures attenuated IGF‐2 mRNA expression and decreased myotube formation, but did not effect IGF‐1 mRNA expression. An activin‐like kinase (ALK) inhibitor, SB431542, mediates MSTN action, suppressed the translocation of Smad2/3 into the nucleus in DM‐myoblasts, and restored the attenuated IGF‐2 mRNA expression and the decreased myotube formation induced by rMSTN in myoblast cultures. The findings indicate that MSTN may negatively regulate myoblast differentiation by suppressing IGF‐2 expression via ALK‐Smad signaling. 相似文献
84.
Canine anal sac apocrine gland adenocarcinoma (ASAGAC) is an uncommon but highly invasive and metastatic malignancy. Toceranib phosphate (Palladia) is a receptor tyrosine kinase (RTK) inhibitor that targets several members of the split kinase RTK family. These membrane receptors are important for cell cycling, apoptosis and angiogenesis, all of which can contribute to carcinogenesis. The objective of this study was to evaluate archived, paraffin-embedded canine ASAGAC and normal canine anal sacs for immunohistochemical detection of Kit and platelet-derived growth factor receptor beta (PDGFR-β). Two of 77 neoplasms (2.6%) expressed Kit. Fifteen of the neoplasms (19.5%) were positive for PDGFR-β expression. None of the normal canine anal sac epithelium expressed Kit or PDGFR-β. Because of these results, further investigation should be considered to determine the role of RTKs in the clinical course and treatment of canine ASAGAC. 相似文献
85.
86.
Comparison on the physico‐chemical and nutritional qualities of normal and abnormal colored fresh chicken liver
下载免费PDF全文
![点击此处可从《Animal Science Journal》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Guoyuan Xiong Xueqin Gao Haibo Zheng Xin Li Xinglian Xu Guanghong Zhou 《Animal Science Journal》2017,88(6):893-899
This study evaluated the differences of physico‐chemical and nutritional qualities between abnormal colored chicken livers (ANCCLs) and normal colored chicken livers (NCCLs) and the safety of the both livers. Compared with NCCLs, ANCCLs were lower in protein, water contents (P < 0.01), pH and pigment contents (P < 0.05). NCCLs contained higher polyunsaturated fatty acid (PUFA) and saturated fatty acids (SFA) (P < 0.05). The PUFA/SFA ratio of NCCLs was 0.453, higher (P < 0.05) than that of ANCCLs. The contents of alanine, valine, tyrosine, lysine and histidine in NCCLs were higher (P < 0.05) than in ANCCLs. The contents of K, Na, P, Cu, Fe and Se of NCCLs were higher (P < 0.05), but the Ca content was lower (P < 0.05). The content of the heavy metals (As, Hg, Pb and Cd) of the two types of livers complied with food safety requirements. Although NCCLs had higher nutritional value than ANCCLs, both livers were acceptable for human consumption. 相似文献
87.
The salt‐sensitive Glycine max N23674 cultivar, the salt‐born Glycine soja BB52 population, and their hybrid 4076 strain (F5) selected for salt tolerance generation by generation were used as the experimental materials in this study. First, the effects of NaCl stress on seed germination, tissue damage, and time‐course ionic absorption and transportation were compared. When qualitatively compared with seed germination appearance in culture dishes, and tissue damages on roots or leaves of seedlings, or quantitatively compared with the relative salt injury rate, the inhibition on N23674 was all the most remarkable. After the exposure of 140 mm NaCl for 1 h, 4 h, 8 h, 12 h, 2 days and 4 days, the content of Cl? gradually increased in the roots and leaves of seedlings of BB52, 4076 and 23674. Interestingly, the extents of the Cl? rise in roots of the three experimental soybean materials were BB52 > 4076 > N23674, whereas those in leaves were just on the contrary. Secondly, by using the scanning ion‐selective electrode technique (SIET), fluxes of Na+ and Cl? in roots and protoplasts isolated from roots and leaves were also investigated among the three experimental soybean materials. After 140 mm NaCl stress for 2, 4 and 6 days, and when compared with N23674, slighter net Cl? influxes were observed in root tissue and protoplasts of roots and leaves of BB52 and 4076 seedlings, especially at the cellular protoplast level. The results indicate that with regard to the ionic effect of NaCl stress, Cl? was the main determinant salt ion for salt tolerance in G. soja, G. max and their hybrid, and the difference in their Cl?/salt tolerance is mainly attributed to the capacity of Cl? restriction to the plant above‐ground parts such as leaves. 相似文献
88.
Pedotransfer functions to assess adsorbed phosphate using iron oxide content and magnetic susceptibility in an Oxisol
下载免费PDF全文
![点击此处可从《Soil Use and Management》网站下载免费的PDF全文](/ch/ext_images/free.gif)
L. A. Camargo J. Marques Jr. G. T. Pereira L. R. F. Alleoni A. S. R. de S. Bahia D. De B. Teixeira 《Soil Use and Management》2016,32(2):172-182
Adsorbed phosphate in soils can be chemically extracted; however, this process is both time‐consuming and not cost‐effective if large numbers of samples have to be analysed. Indirect assessment of adsorbed phosphate by pedotransfer functions (PTFs) can help optimize fertilizer strategies. This study aimed to evaluate the spatial variability of adsorbed phosphate (Pads), iron oxides and magnetic susceptibility (MS) in oxisols and to calibrate PTFs to predict Pads. A total of 308 soil samples were collected from Hapludox and Eutrudox soils formed from sandstone in Brazil. The contents of clay (196–607 g/kg), iron oxides (40–165 g/kg), MS (1.2–29 × 10?6 m3/kg) and Pads (327–842 mg/kg) were in the range of typical values for these highly weathered soils. This study showed that the attributes studied were spatially dependent. Geomorphic surfaces enabled understanding of spatial variability and helped to develop a more efficient sampling scheme to calibrate PTFs. Moreover, the adsorbed phosphate in these oxisols could be predicted by a PTF using iron oxides and MS as predictors. The MS attribute enabled the most accurate prediction (concordance coefficient = 0.95, root‐mean‐square error = 46 mg/kg and relative improvement in root‐mean‐square error = ?4.12) of spatial variability through PTF compared to other predictors. 相似文献
89.
The effect of 0, 0.05 or 0.1 mm abscisic acid treatment on chilling tolerance and salicylic acid‐related responses was investigated in young maize seedlings (Zea mays L., hybrid Norma). Although the pre‐treatment of maize seedlings with abscisic acid slightly decreased the chlorophyll content, it also reduced the level of chilling injury caused by 6 days of cold treatment at 5 °C. Under normal growth conditions, increased levels of bound salicylic acid and of bound ortho‐hydroxycinnamic acid were observed in the leaves during abscisic acid treatment. In the roots, abscisic acid did not affect the free and bound salicylic acid levels, but increased the amount of free and bound ortho‐hydroxycinnamic acid. The activity of glutathione‐S‐transferase increased on the 3rd day of abscisic acid treatment, whereas it did not change when followed by cold stress, compared with the control leaves. In the roots, the activities of glutathione reductase, glutathione‐S‐transferase and ascorbate peroxidase increased during the abscisic acid treatment, and those of glutathione‐S‐transferase and ascorbate peroxidase were also stimulated when abscisic acid pre‐treatment was followed by cold stress, compared with the control roots. Our results suggest that an overlap may exist between the abscisic acid‐induced cold acclimation and the salicylic acid‐related stress response. 相似文献
90.
D. Liu Z. F. Pei M. S. Naeem D. F. Ming H. B. Liu F. Khan W. J. Zhou 《Journal of Agronomy and Crop Science》2011,197(4):284-295
The present study assesses the effects of 5‐aminolevulinic acid (ALA, 0, 0.1, 1 and 10 mg l?1) on the growth of oilseed rape (Brassica napus L. cv. ZS758) seedlings under water‐deficit stress induced by polyethylene glycol (PEG 6000, 0 and ?0.3 MPa). Water‐deficit stress imposed negative effects on seedling growth by reducing shoot biomass, cotyledon water potential, chlorophyll content and non‐enzymatic antioxidants (glutathione and ascorbic acid) levels. On the other hand, water‐deficit stress enhanced the malondialdehyde (MDA) content, reactive oxygen species (ROS) production, enzymatic antioxidants activities, reduced/oxidized glutathione ratio (GSH/GSSG) and reduced/oxidized ascorbic acid (ASA/DHA) ratio in seedlings. Application of ALA at lower dosages (0.1 and 1 mg l?1) improved shoot weight and chlorophyll contents, and decreased MDA in rape seedlings, whereas moderately higher dosage of ALA (10 mg l?1) hampered the growth. The study also indicated that 1 mg l?1 ALA improved chlorophyll content, but reduced MDA content and ROS production significantly under water‐deficit stress. Lower dosages of ALA (0.1 and 1 mg l?1) also enhanced GSH/GSSG and ASA/DHA as compared to the seedlings under water‐deficit stress. The antioxidant enzymes (ascorbate peroxidase, peroxidase, catalase, glutathione reductase and superoxide dismutase) enhanced their activities remarkably with 1 mg l?1 ALA treatment under water‐deficit stress. It was also revealed that 1 mg l?1 ALA treatment alone induced the expression of APX, CAT and GR substantially and under water‐deficit stress conditions ALA treatment could induce the expression of POD, CAT and GR to a certain degree. These results indicated that 0.1–1 mg l?1 ALA could enhance the water‐deficit stress tolerance of oilseed seedlings through improving the biomass accumulation, maintaining a relative high ratio of GSH/GSSG and ASA/DHA, enhancing the activities of the specific antioxidant enzymes and inducing the expression of the specific antioxidant enzyme genes. 相似文献