首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   827篇
  免费   35篇
  国内免费   2篇
林业   67篇
农学   31篇
基础科学   3篇
  107篇
综合类   65篇
农作物   44篇
水产渔业   75篇
畜牧兽医   405篇
园艺   9篇
植物保护   58篇
  2023年   3篇
  2022年   4篇
  2021年   8篇
  2020年   12篇
  2019年   5篇
  2018年   19篇
  2017年   22篇
  2016年   16篇
  2015年   30篇
  2014年   19篇
  2013年   52篇
  2012年   39篇
  2011年   74篇
  2010年   34篇
  2009年   30篇
  2008年   40篇
  2007年   53篇
  2006年   58篇
  2005年   42篇
  2004年   33篇
  2003年   50篇
  2002年   30篇
  2001年   21篇
  2000年   27篇
  1999年   19篇
  1998年   8篇
  1997年   6篇
  1996年   2篇
  1994年   4篇
  1993年   3篇
  1992年   8篇
  1991年   7篇
  1990年   8篇
  1989年   7篇
  1988年   7篇
  1987年   11篇
  1986年   5篇
  1985年   3篇
  1984年   3篇
  1983年   4篇
  1982年   3篇
  1979年   5篇
  1978年   4篇
  1977年   3篇
  1975年   2篇
  1974年   4篇
  1973年   3篇
  1971年   5篇
  1970年   3篇
  1966年   1篇
排序方式: 共有864条查询结果,搜索用时 15 毫秒
91.
Genomic DNA extracted from bovine mummified tissue is valuable material for detection of some genes that may contribute to fetal abnormalities. In this study bovine genomic DNA was extracted from the hardened tissue samples of ten bovine mummified fetuses. The amount of genomic DNA extracted from 2 g of the mummified tissues by the phenol/chloroform-ethanol method was low (less than 4 microg/ml) for all samples. The extracted DNA was then amplified by the GenomiPhi DNA amplification system. After amplification, the amount of DNA was increased to more than 100 microg/ml for all samples. This amplification system was shown to be a good tool for amplifying the genomic DNA of the mummified fetuses. The amplified genomic DNA was used for testing the mummies for Factor XI gene deficiency, an autosomal recessive deficiency involved in the early stages of the intrinsic blood coagulation pathway. Exon 12 of the Factor XI gene of the mummies was amplified by PCR. Two of the ten mummified fetuses were heterozygous for the Factor XI gene as indicated by the presence of two amplified DNA fragments of 320 bp and 244 bp. Factor XI deficiency has already been described in Holstein cattle. However, no report is available for bovine fetus. In this study, DNA was extracted and amplified from the bovine mummified fetuses, and the samples were successfully tested for Factor XI gene deficiency in the mummies.  相似文献   
92.
Replication of calf diarrhea coronavirus was not inhibited by 5-iodo-2′-deoxyuridine, indicating that the virus is an RNA virus. Sensitivity to ether and chloroform indicated that the virus is enveloped, and this was confirmed by electron microscopic observation of the virion. The virus was readily inactivated by trypsin and sodium deoxycholate. The virus was labile at 50°C in diluted medium, but readily stabilized in the presence of MgCl2. It was stable at pH 5 and 7, while a slight loss of infectivity was observed at pH 3. The virus was readily filtered through membrane filters of 200 and 100-nm pore sizes, but not through 50-nm filters. The buoyant density of the virion in CsCl was estimated to be 1.25 g/ml.  相似文献   
93.
94.
In a yeast two-hybrid screening test for tobacco proteins that interact with TMV replicase using the helicase (H) domain as bait, a cDNA clone was selected that encodes a polyamine biosynthetic enzyme, arginine decarboxylase (ADC). In yeast cells, the C-terminal internal region of ADC interacted with the H domain. This observation was confirmed in vitro by far-Western blotting. Inhibition of the binding between the H domain and the IRnHEL (I region and N-terminus of helicase domain) region by ADC using a yeast three-hybrid assay suggested possible interference of the heterodimerization of 126K and 183K by ADC.The nucleotide sequence data of pADCF reported in this study is available in the DDBJ/EMBL/GenBank databases under accession number AB110952  相似文献   
95.
Genetic and phylogenetic analyses of the region containing the glycoprotein (G) gene, which is related to pathogenicity and antigenicity, and the G-L intergenic region were carried out in 14 Brazilian rabies virus isolates. The isolates were classified as dog-related rabies virus (DRRV) or vampire bat-related rabies virus (VRRV), by nucleoprotein (N) analysis. The nucleotide and amino acid (AA) homologies of the area containing the G protein gene and G-L intergenic region were generally lower than those of the ectodomain. In both regions, nucleotide and deduced AA homologies were lower among VRRVs than among DRRVs. There were AA differences between DRRV and VRRV at 3 antigenic sites and epitopes (IIa, WB+ and III), suggesting that DRRV and VRRV can be distinguished by differences of antigenicity. In a comparison of phylogenetic trees between the ectodomain and the area containing the G protein gene and G-L intergenic region, the branching patterns of the chiropteran and carnivoran rabies virus groups differed, whereas there were clear similarities in patterns within the DRRV and VRRV groups. Additionally, the VRRV isolates were more closely related to chiropteran strains isolated from Latin America than to Brazilian DRRV. These results indicate that Brazilian rabies virus isolates can be classified as DRRV or VRRV by analysis of the G gene and the G-L intergenic region, as well as by N gene analysis.  相似文献   
96.
The spermatogenic function and plasma testosterone (T) level in the sex maturation process were investigated as to 180 mixed breed cats ranging from 4 months to 2 years in age to be castrated. Testis/epididymis weights reached a peak at 10 and 8 to 9 months of age, respectively. In the testis, sperm appeared at 5 months of age. At 7 months of age, sperm were observed in 96.2% of the cats. In the tail of the epididymis, sperm appeared in 46.9% of the cats at 6 months of age and in all cats at 8 or more months of age. Furthermore, the mean plasma T level rapidly increased at 8 months of age, and reached a peak (2.64 +/- 0.68 (SE) ng/ml) at 10 months of age. Three of 180 cats (1.67%) had unilateral cryptorchidism. These results suggest that the spermatogenic function in male cats becomes mature at 8 to 10 months of age.  相似文献   
97.
Unilateral intrauterine horn insemination (UIUI) was carried out in cats, and we investigated the fertilization rate of ova ovulated from the contralateral ovary. Various numbers of sperm were used to inseminate the uterine horn on the side where ovulation was inhibited. The rates of conception were 1/11 (9.1%), 2/11 (18.2%), and 5/7 (71.4%) in the 2 x 10(6), 4 x 10(6), and 8 x 10 (6) groups, respectively. Furthermore, the fertilization rate was 70.7% in the 8 x 10(6) group. Thus, ova ovulated from the contralateral ovary were not fertilized or the fertilization rate was low in some cats even when UIUI was performed with a large number of sperm.  相似文献   
98.
In order to evaluate the physiological roles of the testicular endothelin (Edn) signaling via Edn receptor subtype-A (Ednra) in mammals, the localization of Ednra was investigated by in situ hybridization and immunohistochemistry in the testis of rats, dogs, and monkeys. For in situ hybridization, a rat Ednra RNA probe which is highly homologous to the subcloned canine and monkey Ednra (88.7% and 87.9% identical, respectively) was used. Both Ednra mRNA and protein were detected in interstitial cells and cells in the basal compartment of the seminiferous tubules, mainly Sertoli cells, as well as spermatogonia and some early spermatocytes, but not spermatids. The localization pattern of Ednra was exhibited in a same manner among species, indicating that the physiological role of Edn signaling throughout Ednra was maintained in the mammalian testis.  相似文献   
99.
Hepatocyte growth factor/scatter factor (HGF/SF) is a pleiotropic cytokine that plays a crucial role in the embryonic and postnatal development of various organs including the mammary gland. We cloned bovine HGF and its c-Met receptor cDNAs, and examined their expression during mammary gland development in dairy cows. The 2.5-kbp HGF cDNA clone contained a 2190 bp open reading frame coding a 730 amino acid protein, while the 4.8-kbp c-Met cDNA clone contained a 4152 bp open reading frame coding a 1384 amino acid protein. The bovine HGF and c-Met sequences exhibited more than 87% identity with those of other mammals. RT-PCR analysis revealed ubiquitous expression of both HGF and c-Met mRNAs in various bovine tissues tested. HGF mRNA was detected only in the inactive stage of bovine mammary gland development and not in the developing, lactating, and involuting stages, while c-Met mRNA was detected in the inactive and involuting stages. Immunohistochemical analysis demonstrated that the c-Met protein was found on mammary epithelial cells in the inactive, developing, and involuting stages, and on myoepithelial cells in all stages. These results suggest pivotal roles of HGF and c-Met in the development of bovine mammary gland.  相似文献   
100.
Pulmonary alveolar echinococcosis (AE) caused by the metacestode of Echinococcus multilocularis is a lethal zoonosis and is a lesion secondarily induced by hematogenous dissemination from hepatic AE lesions. In the present study, a hematogenous pulmonary AE model was experimentally induced in rats by the injection of echinococcal larval tissue homogenate to the tail vein, and then the pathological and diagnostic aspects of pulmonary AE were examined by magnetic resonance imaging (MRI). Histological primary, mature and degenerated AE lesions were observed 5, 18 and 50 weeks after injection, respectively. These lesions were discriminated as signal-void, hypointense and hyperintense regions in T1-weighted MRI (T1WI), respectively. The change in signal intensity in T1WI might reflect the content of proteinaceous fluid as a result of AE cyst degeneration. Western blot analysis of sera with antibodies of two epitopes (Em18 and Em16) of E. multilocularis provided evidence for AE infection in the early stage. T1WI in combination with Western blot analysis could possibility become definitive and early signs of hematogenous pulmonary AE infection.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号