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   1601篇
  免费   120篇
  国内免费   4篇
林业   95篇
农学   40篇
基础科学   7篇
  200篇
综合类   258篇
农作物   50篇
水产渔业   157篇
畜牧兽医   766篇
园艺   45篇
植物保护   107篇
  2023年   15篇
  2022年   15篇
  2021年   32篇
  2020年   56篇
  2019年   48篇
  2018年   47篇
  2017年   41篇
  2016年   43篇
  2015年   35篇
  2014年   45篇
  2013年   70篇
  2012年   107篇
  2011年   137篇
  2010年   70篇
  2009年   62篇
  2008年   94篇
  2007年   90篇
  2006年   84篇
  2005年   85篇
  2004年   76篇
  2003年   67篇
  2002年   71篇
  2001年   20篇
  2000年   24篇
  1999年   24篇
  1998年   10篇
  1997年   8篇
  1996年   10篇
  1995年   7篇
  1994年   7篇
  1993年   8篇
  1991年   9篇
  1990年   11篇
  1989年   14篇
  1988年   6篇
  1987年   11篇
  1986年   11篇
  1985年   12篇
  1984年   16篇
  1983年   9篇
  1980年   7篇
  1978年   10篇
  1977年   10篇
  1976年   13篇
  1975年   8篇
  1974年   8篇
  1972年   5篇
  1971年   7篇
  1970年   6篇
  1969年   9篇
排序方式: 共有1725条查询结果,搜索用时 46 毫秒
51.
This retrospective study evaluates the effectiveness of nonsurgical treatment using antibiotics to treat hematogenous septic arthritis in five dogs. Giant-breed dogs were over-represented, with all dogs <1 year of age. Synovial fluid cultures were positive in all cases, with common bacterial species isolated that included Streptococcus B-haemolytic spp., Pasteurella multocida, and Staphylococcus intermedius. Dogs treated with appropriate duration and selection of antibiotics had clinical resolution with no residual deficits. This report and a previous clinical report demonstrate that hematogenous septic arthritis can be successfully treated nonsurgically with antibiotic therapy.  相似文献   
52.
OBJECTIVE: To determine effects of short-chain fatty acids (SCFA) on canine colonic smooth muscle. SAMPLE POPULATION: Colonic tissue obtained from 14 healthy dogs. PROCEDURE: Short-chain fatty acid (SCFA; acetate, propionate, and butyrate; 1 to 100 mmol/L)-induced contractions were compared with responses obtained with acetylmethylcholine (AMCh; 10(-4) mol/L). Roles of enteric neurons, cholinergic receptors, calcium stores in the sarcoplasmic reticulum, and extracellular calcium in the SCFA-induced responses were investigated by incubating muscle strips with tetrodotoxin (1 micromol/L), atropine (1 micromol/L), ryanodine (10 micromol/L), nifedipine (1 micromol/L), ethylene glycol-bis (beta-aminoethylether)-N,N,N',N'-tetra-acetate (EGTA; 0.1 mmol/L), or an extracellular calcium-depleted (zero extracellular calcium) solution prior to the addition of propionate or butyrate. RESULTS: Incubation with SCFA elicited isometric stress responses (0.25 to 2.15 x 10(4) N/m2) in colonic longitudinal smooth muscle. Maximal responses to butyrate and propionate (50 mmol/L) were 37 and 23%, respectively, of the maximal AMCh response. Acetate was least effective in stimulating contractile responses. Tetrodotoxin and atropine did not affect SCFA-induced contractions. Nifedipine and zero extracellular calcium solution abolished responses to butyrate and propionate, whereas EGTA attenuated (> 60%) but did not abolish those responses. Ryanodine did not affect SCFA-induced contractile responses. The SCFA did not affect colonic circular smooth muscle. CONCLUSIONS AND CLINICAL RESPONSE: The SCFA stimulate longitudinal but not circular colonic smooth muscle contractions via a direct effect on smooth muscle. The mechanism of the SCFA effect appears to involve the influx of extracellular calcium. These findings may account for some of the effects of fiber on canine colonic motility [corrected].  相似文献   
53.
OBJECTIVE: To evaluate whether immunosuppressive doses of cyclosporine (CsA) have an adverse effect on the liver, kidney, and pancreatic beta cells of pigs. ANIMALS: 8 juvenile 8-week-old Landrace X Large White crossbred pigs. PROCEDURE: CsA (100 to 140 mg/kg) was administered orally to euglycemic pigs to reach whole blood trough concentrations of approximately 1500 ng/mL. To determine pancreatic beta cell function, plasma C-peptide and insulin concentrations were measured in response to i.v. administration of glucose, glucagon, arginine, and oral administration of glucose. Effects on liver and kidney were determined by monitoring serum measurements of liver function and serum creatinine concentrations, respectively. RESULTS: Plasma concentrations of C-peptide were significantly lower in euglycemic CsA-treated pigs, compared with control pigs, following i.v. administration of glucose, glucagon, arginine, and oral administration of glucose. Furthermore, the glucose clearance rate was decreased in euglycemic CsA-treated pigs, compared with control pigs. Serum creatinine concentrations and 4 of 7 serum measurements of liver function were not adversely affected by CsA administration. Serum concentrations of bilirubin and albumin were significantly increased, and serum alanine aminotransferase activity was significantly decreased in CsA-treated pigs, compared with control pigs. Histologic evaluation of liver and kidney sections revealed no pathologic findings in CsA-treated or control pigs. CONCLUSIONS AND CLINICAL RELEVANCE: In our study, immunosuppressive doses of CsA caused an impairment of porcine pancreatic beta cell function, but did not have toxic effects on the kidney. However, on the basis of changes in serum bilirubin and albumin concentrations and alanine aminotransferase activity, subclinical toxic effects on the liver did occur when immunosuppressive doses of CsA were administered.  相似文献   
54.
55.
The cause of death in a postsmolt, Atlantic salmon population with elevated levels of mortalities was investigated. Diagnosis of a rickettsia-like organism was based on gross pathology, histopathology, differential staining, electron microscopy and fluorescent antibody tests. The course of the infection and response to treatment are discussed. This is the first reported occurrence of salmon rickettsias in the Atlantic coast of North or South America.  相似文献   
56.
1. Selected Fat or Lean chickens differ in their plasma glucose insulin relationship: in the fed or fasted state, Fat chickens have a lower glycaemia associated with normal or higher insulinaemia, depending upon the difference in glycaemia. 2. Conversely, chickens selected for low fasting glycaemia (LG) are fattier than their counterparts selected for high fasting glycaemia (HG), although the divergence in fat content is lower than in the Fat-Lean model. 3. The plasma glucose insulin relationship has been investigated in males of the HG and LG lines in the F4 and F5 generations. 4. A difference in glycaemia is suggested during embryonic development and was present at hatching and later on in the fasted or the fed state; insulinaemia did not differ. 5. During refeeding after an overnight fast, glycaemia differed between lines (except at intermediate times); cumulative food intake and insulinaemia were similar. 6. During a glucose tolerance test, glucose disposal rate and insulinaemia were rather similar. 7. Exogenous insulin exerted a very similar hypoglycaemic effect in both lines. 8. Other variables (body temperature, plasma concentrations of potassium and alpha NH2-non protein nitrogen) did not differ between HG and LG chickens. 9. In conclusion, HG and LG chickens do not exhibit any differences in glucose disposal rate, insulinaemia (in various nutritional conditions) or sensitivity to exogenous insulin, which contrasts with Fat or Lean chickens and may explain why HG and LG chickens have diverged to a lesser extent in fat content.  相似文献   
57.
Forty peptides were synthesized corresponding to hydrophilic clusters of amino acids within the sequences of foot-and-mouth disease virus (FMDV) nonstructural proteins (NSP). Six peptides were studied in more detail and the most promising, a 2B peptide, was evaluated in enzyme-linked immunosorbent assay (ELISA) using sera from naive, vaccinated, and vaccinated-and-challenged cattle as well as bovine sera from field outbreaks. The performance of the new NSP peptide ELISA was compared to that of 4 commercial NSP ELISA kits. Antibody to 2B was detectable from the end of the first week to the second week after infection in most of the nonvaccinated animals and by the second to third week in vaccinated-and-challenged animals. The sensitivity of the 2B peptide ELISA was comparable to the 3ABC Ceditest (Ceditest FMDV-NS, Cedi Diagnostics B.V.; Chung et al., 2002). With some modification and further validation, this 2B test could be useful as a screening or conformational NSP test in postvaccination surveillance for FMD.  相似文献   
58.
Flamingos are filter feeders that only rarely ingest larger food items. Their bill anatomy is adapted to the suction, filtration, and ejection of a fluid medium. This case report documents a rare case of bill impaction in a group of Caribbean flamingos (Phoenicopterus ruber) that were kept in a mixed exhibit together with roseate spoonbills (Platalea ajaja) and scarlet ibis (Eudocimus ruber). The latter species received fatty minced meat as part of their diet, which was also accessible to the flamingos. Weakness and poor body condition of one flamingo were noted. On clinical examination, the animal was emaciated, hypoglycemic, and showed a severe impaction of the bill with a mixture of lard, mud, and sand. This mixture had compressed the tongue and eventually had most likely prevented further food intake. In five additional flamingos, a bulging of the gular area, similar to the extension of this area during the tongue-retraction stage of the feeding cycle, was noted and interpreted as a sign of tongue displacement by similar masses in their bills. All animals were caught and the masses removed. All animals resumed food intake immediately, and the emaciated animal rapidly improved in condition. Food presentation was changed so that the trays for the other species were no longer accessible to the flamingos, and no similar problems have been observed since that time.  相似文献   
59.
60.
Radappertized chicken drumsticks were experimentally contaminated with suspensions ofCampylobacter jejuni in two trials. Qualitative analysis on drumsticks with an initial level of contamination of 4.8×103 CFU/cm2 showed that viability was retained for at least 10 days of storage at either 9° or –12°C.In a second quantitative trial, the level of contamination declined from 9.9×102 CFU/cm2 to 4.5×101 CFU/cm2 after 7 days at –20°C. Thereafter,C. jejuni persisted at levels ranging from 1.8×101 to 0.2×101 CFU/cm2 through the 26th week of storage. Drumsticks held at 4°C showed a significant decline in count from 9.9×102 CFU/cm2 to 1.8×102 CFU/cm2 on day 7.It is concluded that the viability ofC. jejuni on chicken parts is maintained under both refrigerated and freezing conditions which approximate commercial storage. This is of significance to the meat industry and consumers.  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