全文获取类型
收费全文 | 4538篇 |
免费 | 310篇 |
国内免费 | 2篇 |
专业分类
林业 | 303篇 |
农学 | 128篇 |
基础科学 | 37篇 |
815篇 | |
综合类 | 851篇 |
农作物 | 195篇 |
水产渔业 | 233篇 |
畜牧兽医 | 1842篇 |
园艺 | 109篇 |
植物保护 | 337篇 |
出版年
2023年 | 31篇 |
2022年 | 34篇 |
2021年 | 68篇 |
2020年 | 77篇 |
2019年 | 82篇 |
2018年 | 96篇 |
2017年 | 89篇 |
2016年 | 110篇 |
2015年 | 79篇 |
2014年 | 120篇 |
2013年 | 197篇 |
2012年 | 229篇 |
2011年 | 284篇 |
2010年 | 179篇 |
2009年 | 149篇 |
2008年 | 255篇 |
2007年 | 244篇 |
2006年 | 258篇 |
2005年 | 239篇 |
2004年 | 189篇 |
2003年 | 221篇 |
2002年 | 181篇 |
2001年 | 72篇 |
2000年 | 82篇 |
1999年 | 84篇 |
1998年 | 44篇 |
1997年 | 39篇 |
1996年 | 40篇 |
1995年 | 34篇 |
1994年 | 29篇 |
1993年 | 32篇 |
1992年 | 39篇 |
1991年 | 54篇 |
1990年 | 49篇 |
1989年 | 46篇 |
1988年 | 33篇 |
1987年 | 60篇 |
1986年 | 40篇 |
1985年 | 58篇 |
1984年 | 38篇 |
1983年 | 46篇 |
1982年 | 25篇 |
1981年 | 22篇 |
1980年 | 24篇 |
1979年 | 34篇 |
1978年 | 25篇 |
1976年 | 26篇 |
1973年 | 27篇 |
1970年 | 24篇 |
1969年 | 31篇 |
排序方式: 共有4850条查询结果,搜索用时 15 毫秒
171.
Background
The objective of this study was to describe aspects of case study herds investigated by the Department of Agriculture, Fisheries and Food (DAFF) in which animal welfare incidents occurred and to identify key performance indicators (KPIs) that can be monitored to enhance the Early Warning System (EWS). Despite an EWS being in place for a number of years, animal welfare incidents continue to occur. Questionnaires regarding welfare incidents were sent to Superintending Veterinary Inspectors (SVIs), resulting in 18 herds being chosen as case study herds, 12 of which had a clearly defined welfare incident date. For each study herd, data on six potential KPIs were extracted from DAFF databases. The KPIs for those herds with a clearly defined welfare incident date were studied for a consecutive four year window, with the fourth year being the ''incident year'', when the welfare incident was disclosed. For study herds without a clearly defined welfare incident date, the KPIs were determined on a yearly basis between 2001 and 2009.Results
We found that the late registration of calves, the use of on-farm burial as a method of carcase disposal, an increasing number of moves to knackeries over time and records of animals moved to ''herd unknown'' were notable on the case farms.Conclusion
Four KPIs were prominent on the case study farms and warrant further investigation in control herds to determine their potential to provide a framework for refining current systems of early warning and prevention. 相似文献172.
A proposal of clinical breakpoints for amoxicillin applicable to porcine respiratory tract pathogens
Schwarz S Böttner A Goossens L Goosens L Hafez HM Hartmann K Kaske M Kehrenberg C Kietzmann M Klarmann D Klein G Krabisch P Luhofer G Richter A Schulz B Sigge C Waldmann KH Wallmann J Werckenthin C 《Veterinary microbiology》2008,126(1-3):178-188
In the present position paper, an attempt was made to establish clinical breakpoints of amoxicillin to classify porcine respiratory tract pathogens as susceptible, intermediate or resistant based on their minimum inhibitory concentrations of amoxicillin. For this, a thorough review of the published literature with regard to swine-specific pharmacological data (including dosages of amoxicillin applied and routes of administration used), clinical efficacy, and in vitro susceptibility of the target pathogens was performed. Based on the comparative analysis of the results, the working group "Antibiotic Resistance" of the German Veterinary Medical Society (DVG) proposed to classify porcine respiratory tract pathogens that show MIC values of amoxicillin of < or =0.5microg/ml as "susceptible", those with MICs of 1microg/ml as "intermediate", and those with MICs of > or =2microg/ml as "resistant". 相似文献
173.
N Martin T Höftmann E Politt HO Hoppen M Sohr AR Günzel-Apel A Einspanier 《Reproduction in domestic animals》2009,44(S2):185-189
Different abortifacient regimes in dogs were analysed for their effect on the pregnancy corpora lutea (CL), namely, prostaglandin F2a analogue cloprostenol (CLO) combined with dopamine agonist cabergoline (CAB), or progesterone (P4) receptor antagonist aglepristone (AGL). Ovaries were collected after 6-10 days of treatment during first trimester. The CL of the control-group showed strong expression of relaxin (RLX), its receptor RXFP1 and enzymes of steroid biosynthesis (HSD) with high peripheral P4-levels. Whereas RXL, RXFP1 and HSD were lowest expressed in the CLO/CAB-group with a massive degeneration of CL and their blood vessels combined with low peripheral P4-level. The AGL-group showed less extensive CL degeneration and more intensive staining of the examined factors than CLO/CAB. In summary, all examined factors are associated with normal luteal function and are useful tools to stage luteolysis. Although both treatments have the same abortive action, their sequence of events on the CL is different. 相似文献
174.
Gawain J. C. Hammond Martin Sullivan Steven Weinrauch Alison M. King 《Veterinary radiology & ultrasound》2005,46(3):205-209
Fluid within the tympanic bulla is an indication of middle ear disease. Radiography has a relatively low accuracy for the detection of soft tissue opacification in the tympanic bulla, and the most useful radiographic projection, the rostrocaudal open mouth (RCd (open mouth)), is technically difficult to perform in dogs and cats. An alternative projection for the feline tympanic bulla, the rostro 10 degrees ventro-caudodorsal oblique (R10 degrees V-CdDO), was compared to the RCd (open mouth) in 41 feline cadaver heads with the tympanic bullae randomly filled with KY jelly. Computed tomography was used as the gold standard. Each tympanic bulla was recorded as being positive or negative for soft tissue opacification. Although there was no significant difference between the accuracy of the two views, the R10 degrees V-CdDO was subjectively more accurate and easier to perform, and in a live patient may be performed without the need for general anesthesia. The R10 degrees V-CdDO projection is a good alternative to the RCd (open mouth) projection for detecting otitis media in the cat. 相似文献
175.
Tamara B. Wills DVM rea A. Bohn DVM PhD DACVP Linda G. Martin DVM MS DACVECC 《Journal of Veterinary Emergency and Critical Care》2005,15(2):136-142
Objective: To present a case of clinical hypocalcemia in a critically ill septic dog. Case summary: A 12‐year old, female spayed English sheepdog presented in septic shock 5 days following hemilaminectomy surgery. Streptococcus canis was cultured from the incision site. Seven days after surgery, muscle tremors were noted and a subsequent low serum ionized calcium level was measured and treated. Intensive monitoring, fluid therapy, and antibiotic treatment were continued because of the sepsis and hypocalcemia, but the dog was euthanized 2 weeks after surgery. New or unique information provided: Low serum ionized calcium levels are a common finding in critically ill human patients, especially in cases of sepsis, pancreatitis, and rhabdomyolysis. In veterinary patients, sepsis or streptococcal infections are not commonly thought of as a contributing factor for hypocalcemia. Potential mechanisms of low serum ionized calcium levels in critically ill patients include intracellular accumulation of calcium ions, altered sensitivity and function of the parathyroid gland, alterations in Vitamin D levels or activity, renal loss of calcium, and severe hypomagnesemia. Pro‐inflammatory cytokines and calcitonin have also been proposed to contribute to low ionized calcium in the critically ill. Many veterinarians rely on total calcium levels instead of serum ionized calcium levels to assess critical patients and may be missing the development of hypocalcemia. Serum ionized calcium levels are recommended over total calcium levels to evaluate critically ill veterinary patients. 相似文献
176.
177.
Unrecognized diversity in New Guinean crayfish species (Decapoda,Parastacidae): The evidence from molecular data 下载免费PDF全文
The phylogenetic relationships among imported ornamental crayfish belonging to the genus Cherax were inferred from a combined dataset of 3 mitochondrial genes (COI, 16S and 12S) and by comparison with available GenBank sequences of 14 Cherax species. Furthermore, the concordance of previously described species obtained from a wholesaler (Cherax boesemani, C. holthuisi and C. peknyi) with available GenBank sequences was verified based on COI with special respect to comparison with sequences assigned as Cherax species. Recently described species C. gherardiae, C. pulcher and C. subterigneus belong to the northern group of Cherax species. Comparison and analysis with other GenBank COI sequences show previously unreported diversity of New Guinean species, suggesting 5 putative new species. Surprisingly, species assigned to the subgenus Astaconephrops do not form a monophyletic clade; this subgenus should be reappraised relative to the purported typical morphological characteristic of the uncalcified patch on male chelae. Increasing importation of crayfish underscores the importance of accurate species identification. Use of basic molecular methods is a necessary requisite for documenting occurrence, abundance and population trends of target species. Consequently, it helps to support eventual conservation decision‐making by stakeholders. 相似文献
178.
Marie Engel David W. Hird Tim E. Carpenter Martin Wierup 《Preventive veterinary medicine》1995,24(4):245-252
A cohort of 53 swine seronegative to Aujeszky's disease virus (ADV) was monitored in a 1 year study of a chronically infected commercial Swedish weaner pig producing herd. Serum samples were acquired from all 134 adult swine and analyzed by enzyme-linked immmunosorbent assay (ELISA). Animals testing negative, along with introduced replacement gilts, were followed serologically every second month. Movements of animals were recorded for 319 days and exposure to seropositive animals was calculated for each seronegative pig in the cohort. The accumulated daily pig contact between the 53 ADV-non-infected swine and 43 infected swine was 35 660 days and the median number of days in contact for the non-infected swine with infected was 222. Despite the frequent contact with seropositive pigs, no seronegative animals seroconverted during the first 11 months of observation. Forty-six of 53 pigs seroconverted after a clinical outbreak during the twelfth month of observation. 相似文献
179.
Martin Kváč Michaela Kestřánová Martina Pinková Dana Květoňová Jana Kalinová Pavla Wagnerová Michaela Kotková Jiří Vítovec Oleg Ditrich John McEvoy Brianna Stenger Bohumil Sak 《Veterinary parasitology》2013,191(3-4):218-227
We describe the morphological, biological, and molecular characteristics of Cryptosporidium pig genotype II and propose the species name Cryptosporidium scrofarum n. sp. to reflect its prevalence in adult pigs worldwide. Oocysts of C. scrofarum are morphologically indistinguishable from C. parvum, measuring 4.81–5.96 μm (mean = 5.16) × 4.23–5.29 μm (mean = 4.83) with a length to width ratio of 1.07 ± 0.06 (n = 400). Oocysts of C. scrofarum obtained from a naturally infected pig were infectious for 8-week-old pigs but not 4-week-old pigs. The prepatent period in 8-week-old Cryptosporidium-naive pigs was 4–6 days and the patent period was longer than 30 days. The infection intensity of C. scrofarum in pigs was generally low, in the range 250–4000 oocysts per gram of feces. Infected pigs showed no clinical signs of cryptosporidiosis and no pathology was detected. Cryptosporidium scrofarum was not infectious for adult SCID mice, adult BALB/c mice, Mongolian gerbils (Meriones unguiculatus), southern multimammate mice (Mastomys coucha), yellow-necked mice (Apodemus flavicollis), or guinea pigs (Cavia porcellus). Phylogenetic analyses based on small subunit rRNA, actin, and heat shock protein 70 gene sequences revealed that C. scrofarum is genetically distinct from all known Cryptosporidium species. 相似文献