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   9265篇
  免费   442篇
  国内免费   14篇
林业   588篇
农学   229篇
基础科学   84篇
  1585篇
综合类   1610篇
农作物   365篇
水产渔业   822篇
畜牧兽医   3391篇
园艺   278篇
植物保护   769篇
  2024年   19篇
  2023年   59篇
  2022年   90篇
  2021年   155篇
  2020年   211篇
  2019年   208篇
  2018年   207篇
  2017年   218篇
  2016年   210篇
  2015年   184篇
  2014年   252篇
  2013年   449篇
  2012年   542篇
  2011年   707篇
  2010年   368篇
  2009年   352篇
  2008年   635篇
  2007年   626篇
  2006年   594篇
  2005年   577篇
  2004年   609篇
  2003年   572篇
  2002年   507篇
  2001年   102篇
  2000年   91篇
  1999年   93篇
  1998年   81篇
  1997年   70篇
  1996年   67篇
  1995年   62篇
  1994年   61篇
  1993年   50篇
  1992年   57篇
  1991年   49篇
  1990年   58篇
  1989年   49篇
  1988年   42篇
  1987年   44篇
  1986年   33篇
  1985年   32篇
  1984年   34篇
  1983年   40篇
  1982年   26篇
  1981年   25篇
  1980年   28篇
  1979年   23篇
  1978年   20篇
  1976年   20篇
  1975年   22篇
  1974年   15篇
排序方式: 共有9721条查询结果,搜索用时 15 毫秒
171.
172.
173.
In 1910, H. B. Fantham described the life cycle of a coccidian parasite in birds. Fantham was a parasitologist at Cambridge University in the United Kingdom working for an enquiry into diseases affecting the red grouse. Despite the growing importance of the poultry industry and the realization that coccidiosis was an important disease of the fowl, little further work was carried out in the United Kingdom until coccidiosis research was initiated at the Veterinary Laboratory, Weybridge almost 30 yr later. Further progress depended upon research carried out at academic and agricultural institutions in the United States. E. E. Tyzzer at Harvard University provided the solid foundation upon which our present knowledge of coccidiosis, and the species of Eimeria involved in the disease, is based. Agricultural experiment stations (AESs) throughout the nation played an important role in communicating advances to the agricultural community. W. T. Johnson at Western Washington and, subsequently, Oregon AES made significant contributions to our understanding of the disease, as did C. A. Herrick and coworkers at Wisconsin AES, J. P. Delaplane and coworkers at Rhode Island AES, and P. P. Levine at Cornell University.  相似文献   
174.
An 11-year-old Trakehner gelding required 2 ventral midline celiotomies for correction of a large colon volvulus and a large colon displacement, respectively. Laparoscopic colopexy was performed 50 days following the 2nd celiotomy. Delayed laparoscopic colopexy is minimally invasive and does not disrupt the ventral midline incision following abdominal exploration.  相似文献   
175.
OBJECTIVE: To develop and validate an ELISA for measurement of serum canine pepsinogen A (cPG A) as a diagnostic marker of gastric disorders in dogs and to measure serum cPG A in healthy dogs after food deprivation and after feeding. SAMPLE POPULATION: Sera from 72 healthy dogs. PROCEDURE: A sandwich ELISA was developed and validated. The reference range for serum concentrations of cPG A was determined in 64 healthy dogs. Postprandial changes in serum concentrations of cPG A were evaluated in 8 healthy dogs. RESULTS: Assay sensitivity was 18 microg/L, and the maximum detectable concentration was 1,080 microg/L. The observed-to-expected ratio (O:E) for 3 serial dilutions of 3 serum samples ranged from 69.3 to 104.1%. The O:E for 3 serum samples spiked with 8 concentrations of cPG A ranged from 58.8 to 120.4%. Coefficients of variation for intra- and interassay variability of 3 serum samples ranged from 7.6 to 11.9% and from 10.1 to 13.1%, respectively. Mean +/- SD serum concentration of cPG A in healthy dogs was 63.8 +/- 31.0 microg/L and the reference range was 18 to 129 microg/L. Significant increases in serum concentrations of cPG A were observed between 1 and 7 hours after feeding. CONCLUSIONS AND CLINICAL RELEVANCE: The ELISA for measuring cPG A was sufficiently sensitive, linear, accurate, precise, and reproducible for clinical use. Serum concentrations of cPG A increase substantially after feeding, which should be taken into account when conducting clinical studies.  相似文献   
176.
177.
A 6-year-old castrated male Dalmatian was evaluated because of hematemesis. The dog had lived its entire life in South Dakota and Wyoming and had never traveled outside of these states. Results of laboratory testing were compatible with iatrogenic acute renal failure and gastrointestinal tract ulceration secondary to previous nonsteroidal anti-inflammatory drug and corticosteroid administration. Differential diagnoses for clinical signs and laboratory abnormalities that existed prior to these treatments included multisystemic infectious or inflammatory disease and neoplasia. Four-quadrant abdominocentesis did not yield any fluid, but because intra-abdominal disease was still suspected, diagnostic peritoneal lavage was performed. Fluid that was obtained was markedly cellular, and there were numerous extracellular structures with a round to oval shape; a 1-microm-thick, clear-staining capsule; a basophilic interior; and broad-based budding. Organisms were consistent with Blastomyces spp, and fungal culture yielded Blastomyces dermatitidis. Treatment with liposomal amphotericin B and itraconazole was recommended but could not be initiated because of the client's financial constraints. At necropsy, disseminated blastomycosis involving the stomach, small intestines, urinary bladder, omentum, mesentery of the small intestine, and abdominal wall musculature was seen. To our knowledge, peritoneal involvement has not been reported in dogs with blastomycosis, and gastrointestinal tract involvement has only rarely been reported. Findings in this dog suggest that diagnostic peritoneal lavage may be a useful technique in determining the cause of infectious peritonitis when the amount of abdominal fluid is below the limit of detection for abdominocentesis.  相似文献   
178.
Reports of cystic thyroid and parathyroid masses in cats are uncommon. Herein, the authors describe a series of four cats with cystic ventral cervical lesions, among them thyroid cyst (n=1), thyroid cystadenoma (n=2), and parathyroid adenocarcinoma (n=1). Presentations ranged from completely asymptomatic cervical swellings to signs related to local compression of adjacent structures (e.g., trachea). Ultrasonographic evaluation was helpful in localization of the mass in two cases. Hormone analysis and concentration of cystic fluid were performed in one cat. Surgical excision was performed successfully in three cases. Histopathological examination was performed in all four cases. Long-term prognosis was excellent for those cases in which follow-up was available.  相似文献   
179.
Diseases of the accessory lung lobe (AccLL) are often overlooked in dogs and cats, perhaps because of its recessed location. Diseases of this lobe also can mimic diseases of the diaphragm or structures comprising the caudal mediastinum. Normal anatomy of the AccLL and the diagnostic tools used today will be reviewed to help differentiate disease of adjacent organs. Four cases will also be described to illustrate disease presentation and radiographic findings affecting this lobe.  相似文献   
180.
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