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   17482篇
  免费   922篇
  国内免费   18篇
林业   929篇
农学   572篇
基础科学   127篇
  2580篇
综合类   2679篇
农作物   937篇
水产渔业   988篇
畜牧兽医   8473篇
园艺   202篇
植物保护   935篇
  2021年   168篇
  2020年   171篇
  2019年   191篇
  2018年   331篇
  2017年   377篇
  2016年   283篇
  2015年   208篇
  2014年   333篇
  2013年   685篇
  2012年   524篇
  2011年   660篇
  2010年   452篇
  2009年   444篇
  2008年   665篇
  2007年   583篇
  2006年   532篇
  2005年   470篇
  2004年   442篇
  2003年   438篇
  2002年   389篇
  2001年   491篇
  2000年   483篇
  1999年   378篇
  1998年   180篇
  1997年   203篇
  1995年   193篇
  1994年   158篇
  1993年   165篇
  1992年   280篇
  1991年   314篇
  1990年   310篇
  1989年   316篇
  1988年   289篇
  1987年   250篇
  1986年   296篇
  1985年   255篇
  1984年   209篇
  1983年   207篇
  1979年   250篇
  1978年   166篇
  1975年   171篇
  1974年   234篇
  1973年   215篇
  1972年   251篇
  1971年   230篇
  1970年   203篇
  1969年   192篇
  1968年   158篇
  1967年   160篇
  1966年   161篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
A 10-year-old German shepherd dog was presented with unilateral uveitis and hyphaema. Treatment was unsuccessful and the eye was enucleated. Intraocular osteosarcoma was diagnosed by histological examination.  相似文献   
62.
A captive 16-year-old male camel (Camelus ferus bactrianus) was euthanized after a prolonged period of inappetence leading to cachexia. At necropsy, there was a 7 cm large, tan, firm, well-demarcated nodule in the tunica muscularis and serosa of the distal region of C3. Histologically, a gastric adenocarcinoma was diagnosed. Numerous metastases were found in the liver and the hepatic lymph nodes, in the wall of the portal vein and the aorta, in the lung, heart, and pleura parietalis. Osseous metaplasia was found within the pleural and aortic metastases. In the mucosa of the glandular region of the C3 compartment a diffuse marked hypertrophy of rugae resembling cerebral convolutions was observed. The lesion was characterized by glandular hyperplasia and stromal inflammation and oedema. These changes closely resembled Menétrier's disease described in humans. To our knowledge, this is the first report of concomitant metastatic gastric adenocarcinoma and gastric hyperplasia in a camel.  相似文献   
63.
Serum protein values were determined in 26 healthy dogs using agarose gel electrophoresis (SPE), splitting the electrophoretic separation into six regions: albumin, alpha(1), alpha(2), beta(1), beta(2)and gamma globulins. High-resolution electrophoresis (HRE) was used to separate single proteins. Serum proteins from dogs (26 healthy and 20 affected by various diseases) were then characterized by electrophoretic immunofixation (IFE) and Sudan black staining on HRE film. Haemoglobin and normal canine plasma and serum were used to identify haptoglobin and fibrinogen, respectively.In the standard pattern, determined by HRE, the following proteins were identified: albumin, alpha(1)-lipoprotein (alpha(1)-region), haptoglobin and alpha(2)-macroglobulin (alpha(2)-region), beta -lipoprotein and C3 (beta(1)-region), transferrin and IgM (beta(2)-region), IgG (mostly in gamma -region and partly in beta(2)-region). The HRE pattern shown by healthy dogs could be compared with those of dogs affected by various diseases to obtain clinical information.  相似文献   
64.
Direct and maternal genetic and environmental variances and covariances were estimated for weaning weight and growth and maturing traits derived from the Brody growth curve. Data consisted of field records of weight measurements of 3,044 Angus cows and 29,943 weaning weight records of both sexes. Growth traits included weights and growth rates at 365 and 550 d, respectively. Maturing traits included the age of animals when they reached 65% of mature weight, relative growth rates, and degrees of maturity at 365 and 550 d. Variance and covariance components were estimated by REML from a set of two-trait animal models including weaning weight paired with a growth or maturing trait. Weaning and cow contemporary groups were defined as fixed effects. Random effects for weaning weight included direct genetic, maternal genetic, and permanent environmental effects. For growth and maturing traits, a random direct genetic effect was included in the model. Direct heritability estimates for growth traits ranged from .46 to .52 and for maturing traits from .31 to .34. Direct genetic correlations between weaning weight and weights and growth rates at 365 and 550 d ranged from .56 to .70. Correlations of maternal weaning genetic effects with direct genetic effects on weights at 365 and 550 d were positive, but those with growth rates were negative. Between weaning weight and degrees of maturity at both 365 and 550 d, direct genetic correlation estimates were .55 and maternal genetic correlations estimates were -.05, respectively. Direct genetic correlations of weaning weight with relative growth rates and age at 65% of mature weight ranged from .04 to .06, and maternal-direct genetic correlation estimates ranged from -.50 to -.56, respectively. These estimates indicate that higher genetic capacity for milk production was related to higher body mass and degrees of maturity between 365 and 550 d of age but was negatively related to absolute and relative growth rates in that life stage.  相似文献   
65.
The objective of this study was to report our experience with an absorbable haemostatic gauze product in 20 horses with traumatic or surgical haemorrhage. The product is made from oxidised, regenerated cellulose (ORC) and is approved for external use and currently being studied to control internal bleeding in surgical settings in human subjects. Treated horses were from both practice and university settings. Signalment, anatomic location, underlying cause of bleeding and outcome were recorded in the medical record. The size of gauze, approximate time until bleeding stopped, and pre- and post-ORC adjunctive treatments were also recorded. The ORC was used in a variety of anatomic locations, including castration site, foot, flank incisions, distal limb, tooth extraction sites and the perineal region. The bleeding stopped or slowed dramatically within 90 s in 15 of 20 cases. There were no recorded complications in any of the cases. While this clinical report does not attempt to prove efficacy of the product in horses, it does show that this ORC product, which has been approved for use as a haemostatic agent in human subjects, is safe and of practical value, and may be a useful and viable option for the control of haemorrhage in a variety of equine clinical settings.  相似文献   
66.
Standardised procedure for obtaining reproducible haemagglutination-inhibition results for FPV antibody which correlate with serum-neutralization titres was described. Optimal conditions were found to be Alsevers anticoagulant, PBS/0.05% BSA (pH 6.8) as buffer, especially washed round bottom microplates, determination of maximally sensitive porcine erythrocytes, use of reproducible erythrocyte concentrations, inactivation of serum samples at 56 degrees C for 30 min and serum treatment with koalin pH 9.0. The concentration of erythrocyte used for estimation of haemagglutination units in H1 test should not differ from that used as indicator in the test. Predilution of serum beyond 1:4 associated with false results. Reproducible method for removing natural agglutinins in serum by adsorption with erythrocytes was described.  相似文献   
67.
Six intact Balami rams were experimentally infected with Anaplasma ovis. Another six were infected one month after splenectomy and six others served as controls. Clinical manifestations of the disease, first observed between 5 to 7 days post-infection, were more severe and prolonged in the splenectomised-infected than in the intact-infected group. There was progressive deterioration in semen quality, which was also significantly more severe and prolonged in the splenectomised than in the intact-infected rams. Following treatment with long-acting terramycine, clinical recovery occurred earlier in the intact-infected (1–4 weeks) than in the splenectomised-infected group (5–7 weeks). A similar pattern was observed in post-treatment improvement in the spermiogram. However, although the infected animals recovered clinically by 1–7 weeks post-treatment, restoration of the reproductive potential did not occur for 20 to 25 weeks. It appears that stress factors may aggravate the deliterious effects of anaplasmosis.  相似文献   
68.
The formation of zearalenone in a maize plot artificially infected with Fusarium culmorum was studied. The zearalenone concentration steeply increased only in the 8th week after inoculation and reached a maximum value of ca. 7 ppm, whereas zearalenone could not be detected in the control variants. The crude nutrient and dry matter content was not significantly influenced by the fungal infection. The infected crop showed average ear dry weights distinctly lower than that of the control variants (P less than or equal to 0.001). Apart from zearalenone, the mycotoxin deoxynivalenol was qualitatively detected in the infected maize. The toxicological relevance of the ascertained zearalenone content with regard to the health of dairy cattle and pigs was discussed.  相似文献   
69.
70.
Pathogenesis of Mycobacterium bovis infection in American bison   总被引:3,自引:0,他引:3  
Eighteen 12-month-old bison were randomly placed in each of 3 groups (6 animals/group): group-1 bison were exposed to live Mycobacterium bovis, group-2 bison were inoculated with killed M bovis in oil, and group-3 bison were noninfected controls. Six, 6-month-old, tuberculin test-negative calves were placed (pen contact) with group-1 bison 30 days after exposure to M bovis. Tuberculin skin test responses (caudal fold and/or comparative cervical) were detected in all bison in groups 1 and 2 at 2, 4, 6, 10, and 12 months. Tuberculin skin test responses were observed in 2 of 6 calves at 9 and 11 months after pen contact with M bovis-exposed bison (group 1). Statistically significant lymphocyte blastogenic responses to M bovis purified protein derivative were detected in group-1 bison exposed to live M bovis at 2 months after exposure (P less than 0.025). Significant ELISA reactions were detected in sera of bison at 2 months after exposure to killed M bovis in oil (P less than 0.005) and in bison 2 months after exposure to live M bovis (P less than 0.01). Significant tuberculin skin responses, ELISA reactions, or lymphocyte blastogenic responses to M bovis purified protein derivative were not observed in the 6 control bison. Grossly visible tuberculous lesions were observed in lymph nodes and/or lung collected at necropsy in 4 of 6 bison at 12 months after exposure to live M bovis. Microscopic granulomas compatible with tuberculosis were detected in 5 of 6 bison; M bovis was isolated from tissues of each of the 6 bison.(ABSTRACT TRUNCATED AT 250 WORDS)  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