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   635篇
  免费   20篇
  国内免费   6篇
林业   30篇
农学   29篇
  116篇
综合类   46篇
农作物   20篇
水产渔业   80篇
畜牧兽医   297篇
园艺   5篇
植物保护   38篇
  2022年   9篇
  2021年   15篇
  2020年   5篇
  2019年   8篇
  2018年   7篇
  2017年   14篇
  2016年   13篇
  2015年   12篇
  2014年   22篇
  2013年   57篇
  2012年   24篇
  2011年   22篇
  2010年   17篇
  2009年   14篇
  2008年   36篇
  2007年   35篇
  2006年   39篇
  2005年   38篇
  2004年   36篇
  2003年   33篇
  2002年   36篇
  2001年   32篇
  2000年   31篇
  1999年   26篇
  1998年   5篇
  1997年   6篇
  1996年   3篇
  1995年   3篇
  1994年   4篇
  1992年   2篇
  1991年   8篇
  1990年   8篇
  1989年   5篇
  1988年   7篇
  1986年   3篇
  1985年   1篇
  1983年   4篇
  1981年   2篇
  1980年   1篇
  1979年   1篇
  1978年   2篇
  1977年   2篇
  1976年   1篇
  1973年   2篇
  1970年   1篇
  1968年   2篇
  1962年   1篇
  1960年   3篇
  1957年   1篇
  1956年   1篇
排序方式: 共有661条查询结果,搜索用时 15 毫秒
601.
ABSTRACT Tomato wilt, caused by the soilborne fungus Fusarium oxysporum f. sp. lycopersici, is effectively controlled by a foliar spray of validamycin A (VMA) or validoxylamine A (VAA) (>/=10 mug/ml); however, neither VMA nor VAA is antifungal in vitro. In pot tests, the effect of a foliar application of VMA or VAA at 100 mug/ml lasted for 64 days. Plants sprayed with VMA or VAA accumulated salicylic acid and had elevated expression of the systemic acquired resistance (SAR) marker genes P4 (PR-1), Tag (PR-2), and NP24 (PR-5). Foliar spray of VMA also controlled late blight and powdery mildew of tomato. The disease control by VMA and VAA lasted up to 64 days after treatment, was broad spectrum, and induced the expression of PR genes, all essential indicators of SAR, suggesting that VMA and VAA are plant activators. The foliar application of plant activators is a novel control method for soilborne diseases and may provide an economically feasible alternative to soil fumigants such as methyl bromide.  相似文献   
602.
A 9-year, 7-month-old female German shepherd weighing 26.6 kg was admitted to the hospital for pica and diarrhea. A large mass was found in the right ovary and removed, and cross section of the mass revealed a multilobular tumor consisting of several cystic cavities which contained tufts of dark hair in thick creamy-white sebaceous fluid. Histologically, the tumor consisted of adipose tissue, central nervous tissue, crystalline lens, cartilage and bone. In the central nervous tissue, lens and lesions like nonsuppurative inflammation comprizing of accumulation of glial cells and lymphocytic perivascular cuffing were observed. The tumor was diagnosed as a mature cystic teratoma.  相似文献   
603.
A novel colitis model using Syrian hamsters was developed. Colitis was induced by intracolonic administration of 1% acetic acid, and the ulcer area, tissue myeloperoxidase (MPO) activity, and luminal neutrophil elastase (NE) activity of the colon were determined at 1, 3, 8, 24 and 48 hr after colitis induction. The histopathological changes of the colon were also examined in this model. An increase of tissue MPO activity and NE activity was evident at 3 hr after induction of colitis, peaked at 24 hr, and decreased subsequently. The increase of luminal NE activity was well correlated with the colonic ulcer area. In histopathological examination, ulceration, erosion, crypt abscesses, neutrophil infiltration, hemorrhage, and edema were seen. The effects of prednisolone were examined to evaluate the adequacy of our colitis model. Syrian hamsters were treated orally with prednisolone at 18 and 1 hr before and at 6 hr after induction of colitis, and the ulcer area, tissue MPO activity, and luminal NE activity were evaluated at 24 hr after colitis induction. Prednisolone therapy had little effect on the tissue MPO activity. However, the NE activity of the prednisolone-treated group was significantly decreased. In addition, although prednisolone did not significantly decrease the ulcer area, a tendency toward decrease was noted. We conclude that this new model of experimental colitis in Syrian hamsters is useful for investigating the pathophysiology of colitis, especially useful for studying the relationship between colitis and NE activity.  相似文献   
604.
The relationship between the canine distemper virus (CDV) infection and apoptosis in the canine lymphoid tissues was investigated using immunostaining for single stranded DNA (ssDNA), TdT-mediated dUTP-biotin nick end-labeling (TUNEL) method, and electron microscopy. Twenty-six lymphoid tissues from 8 spontaneously CDV-infected dogs and 1 non-infected dog were used, and lesions were classified into 4 groups according to frequency of the CDV-antigen. Histologically, the degree of lymphoid depletion tended to depend on amount of CDV antigen. The numbers of ssDNA- and TUNEL-labeling cells were significantly high in the lymphoid tissues with abundant viral antigen. However, ssDNA- and TUNEL-positive lymphocytes were also frequently found even in the lymphoid tissues where there was only a small amount of CDV-antigen in sinus histiocytes. The incidence and distribution of apoptotic cells in the CDV-antigens-negative lymphoid tissues from infected dogs were equal to those from a non-infected dog. Double labeling immunostaining using a ssDNA and a CDV nucleocapsid protein (CDV-NP) antibody revealed that there were ssDNA positive but CDV-NP negative cells besides those stained doubly positive. Ultrastructurally, lymphocytes in the CDV-infected lymphoid tissues frequently had characteristic morphological features of apoptosis such as apoptotic bodies. All these results suggest that CDV leads to lymphocytic apoptosis directly or indirectly, resulting in severe lymphoid depletion and immunosuppression in acute or subacute phase of CDV infection.  相似文献   
605.
Our previous report demonstrated that small wild rodents in Japan harbored two types of novel Babesia microti-like parasites (Kobe and Hobetsu types), but not the type widely distributed throughout the temperate zones of North American and Eurasian Continents (U.S. type). In this study, we surveyed small wild mammals collected at various places in the northern part of Japan, seeking for U.S.-type B. microti. A total of 197 small mammals comprising 10 species, Apodemus speciosus, A. argenteus, Clethrionomys rufocanus, C. rutilus, Eothenomys andersoni, Microtus montebelli, Tamias sibiricus, Sorex unguiculatus, S. caecutiens, and Urotrichus talpoides, were examined. Babesia parasites were detected in A. speciosus, C. rufocanus, C. rutilus, M. montebelli, S. unguiculatus, and S. caecutiens by microscopy of blood smears and by PCR targeting babesial nuclear small-subunit rRNA (rDNA) and beta-tubulin genes. Inoculation of their bloods into experimental animals gave rise to 23 parasite isolates, which included 16 from A. speciosus, 4 from C. rufocanus, and 1 each from C. rutilus, M. montebelli and S. unguiculatus. Sequencing analyses of their rDNA and beta-tubulin genes revealed that, of the 23 isolates, 20 and 3 were of Hobetsu and U.S. types, respectively. The U.S.-type B. microti strains isolated in Japan, however, were distinguishable from the isolates in the United States when their beta-tubulin gene sequences and antigen profiles in Western blots were compared. We conclude that U.S.-type B. microti exists in Japan although it has been genetically and antigenically diversified from that distributed in the United States. The results also suggest that not only rodents, but also some insectivores may serve as reservoirs for the agent of human babesiosis.  相似文献   
606.
Three canine gastrointestinal stromal tumors (GISTs) were examined. Histopathologically, the tumor mass in the jejunum (Case 1) consisted of the proliferation of epithelioid cells with abundant eosinophilic or vacuolated cytoplasm. Gangliocyte-like or multinucleated giant cells were scattered. The tumor cells exhibited neural natures mimicking human gastrointestinal autonomic nerve tumors, which were immunopositive for several neuronal markers. Another jejunal mass (Case 2) was composed by a solid proliferation of spindle-shaped cells, arranging in interlacing fascicles and occasional storiform pattern. The tumor seemed to be classified undifferentiated GISTs, that showed no apparent neural or muscular features by ultrastructural and immunohistochemical examinations. In the pyloric mass (Case 3), the spindle cells having eosinophilic processes and elongated nuclei were arranged in sheets. Immunohistochemically, the tumor cells showed muscular natures as regards alpha smooth muscle actin and desmin expression.  相似文献   
607.
608.
Chlamydophila felis (C. felis), feline herpesvirus-1 (FHV-1) and feline calicivirus (FCV) were detected in 39 (59.1%), 11 (16.7%) and 14 (21.2%) cats respectively, from 66 domestic cats presented with conjunctivitis and upper respiratory tract disease (URTD) in 9 prefectures of Japan. Dual and multiple infections were found in 7 (10.6%) cats with both C. felis and FHV-1, 10 (15.2%) cats with both C. felis and FCV, and 1 (1.5%) cat with all three agents. C. felis was isolated from 11 (28.2%) of 39 PCR positive cats. Antigenic difference was found in a 96 kDa protein of our isolates and Fe/145 strain isolated in USA. In conclusion, C. felis is the most common agent of feline conjunctivitis and URTD, and the coinfection with C. felis, FHV-1 and FCV are also common in cats in Japan.  相似文献   
609.
An anterior mediastinal cystic lesion in an 11-year-old mongrel dog was examined. The dog showed dysbasia and vomiting due to megaoesophagus, and anterior mediastinal round mass lesion, approximately 35 mm in diameter, was found by X ray. Based on clinical examinations, the dog was diagnosed as acquired myasthenia gravis and was successfully controlled by anticholinesterase treatment for approximately 4 months. The dog died of thermic stroke and was necropsied. Grossly, fatty tissues with cysts containing yellowish fluid and white nodules were found in the anterior mediastinal area. Histopathologically, multiple cysts, neoplastic tissues, and atrophic thymus were found within the examined tissues. The cysts were lined by thin wall consisting of ciliated long cuboidal and non-ciliated round cells and were filled with eosinophilic colloidal fluid. Some extended cysts contained neoplastic foci within their lumen and walls. The neoplastic tissues consisted of mixed population of large epithelial cells with abundant clear cytoplasm and large oval nuclei, and lymphocytes. Immunohistochemically, proliferating epithelial cells were intensely positive for keratin and cytokeratin, and more than half number of infiltrating lymphocytes were intensely positive for CD3 suggesting T cells. All these findings indicate the neoplastic lesion is thymoma and multiple cysts are considered as thymic or brachial cleft cysts.  相似文献   
610.
A total of 1,013 feces samples and 8 mesenteric lymphonodus samples obtained from apparently healthy dogs were examined for the incidence of salmonella infection. One strain of S. typhimurium (ST) was isolated from feces of one dog, and S. enteritidis (SE) was isolated from the mesenteric lymphonodus of one dog. Sera obtained from 330 apparently healthy dogs were examined for Salmonella antibodies using an ELISA with heated whole cells of SE and ST. Fifty-one of the 330 serum samples were considered to be positive for salmonella antibodies, including 12 which were SE-positive and 39 which were ST-positive. These results indicate that dogs cause possible environmental problems as Salmonella carriers.  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