全文获取类型
收费全文 | 18299篇 |
免费 | 101篇 |
国内免费 | 1篇 |
专业分类
林业 | 3711篇 |
农学 | 1353篇 |
基础科学 | 145篇 |
3099篇 | |
综合类 | 948篇 |
农作物 | 2232篇 |
水产渔业 | 1928篇 |
畜牧兽医 | 1786篇 |
园艺 | 1151篇 |
植物保护 | 2048篇 |
出版年
2023年 | 10篇 |
2021年 | 27篇 |
2020年 | 41篇 |
2019年 | 37篇 |
2018年 | 2766篇 |
2017年 | 2719篇 |
2016年 | 1215篇 |
2015年 | 96篇 |
2014年 | 66篇 |
2013年 | 99篇 |
2012年 | 877篇 |
2011年 | 2251篇 |
2010年 | 2148篇 |
2009年 | 1315篇 |
2008年 | 1405篇 |
2007年 | 1683篇 |
2006年 | 149篇 |
2005年 | 188篇 |
2004年 | 200篇 |
2003年 | 230篇 |
2002年 | 142篇 |
2001年 | 36篇 |
2000年 | 71篇 |
1999年 | 29篇 |
1998年 | 18篇 |
1997年 | 20篇 |
1996年 | 17篇 |
1995年 | 14篇 |
1994年 | 18篇 |
1993年 | 28篇 |
1992年 | 38篇 |
1991年 | 12篇 |
1990年 | 29篇 |
1989年 | 29篇 |
1988年 | 27篇 |
1987年 | 22篇 |
1986年 | 18篇 |
1985年 | 25篇 |
1984年 | 25篇 |
1982年 | 10篇 |
1981年 | 17篇 |
1980年 | 11篇 |
1979年 | 11篇 |
1978年 | 12篇 |
1977年 | 12篇 |
1976年 | 16篇 |
1975年 | 10篇 |
1974年 | 14篇 |
1973年 | 12篇 |
1967年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 312 毫秒
1.
2.
3.
George J. Brewer MD William Schall DVM Robert Dick BS Vilma Yuzbasiyan-Gurkan PhD Michael Thomas DVM George Padgett DVM 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》1992,6(1):41-43
Inherited canine copper toxicosis is a serious problem in Bedlington terriers and West Highland White terriers, and may also be a problem in other less-studied breeds. Affected dogs become ill at midlife with progressive and ultimately fatal liver disease. Treatments for removal of copper and prevention of copper accumulation are available, but are most effective if begun before the dog becomes ill. Until recently diagnosis has not been available until the dog is 1 year of age, and then only by an invasive liver biopsy with determination of liver copper concentration. The authors studied the use of 64copper for early diagnosis of canine copper toxicosis. Two procedures were evaluated. The first involved measuring the concentration of 64copper in blood 24 hours after oral administration of the radioisotope. At this time, 64copper was associated primarily with ceruloplasmin secreted into the blood by the liver. This procedure is useful in the diagnosis of the human counterpart, Wilson's disease. However, the authors found it to be nondiscriminatory between affected and unaffected dogs. In contrast, the second procedure, which involved measuring 64copper excreted in stool during 48 hours after an intravenous dose of radioisotope, yielded results that differentiated most affected and unaffected dogs. 相似文献
4.
5.
Bovine neutrophil chemotactic activity was detected in the supernatant fluid of logarithmic phase cultures of P. haemolytica serotype 1. The chemoattractant was produced under culture conditions suitable for P. haemolytica leukotoxin production. An inverse correlation existed between the leukotoxin LC50 and the chemotactic activity in the culture fluid. Elimination of leukotoxin activity by heating, dilution or ultrafiltration, exposed the chemotactic activity in the culture fluid. The chemoattractant was partially resistant to heating (60 degrees C, 30 min), and had an apparent molecular weight greater than 100,000. Detection of chemotactic activity in both the concentrate and filtrate after XM300 filtration suggested that there might be more than one component with chemotactic activity or else that polymerization was occurring. Production of a potent neutrophil chemoattractant by P. haemolytica may explain the rapid infiltration of neutrophils that occurs during the early stages of bovine pneumonic pasteurellosis. 相似文献
6.
Pharmacokinetic and Phase I Evaluation of Carboplatin in Dogs 总被引:1,自引:1,他引:0
Rodney L. Page DVM MS Margaret C. McEntee DVM Steven L. George PhD Patrick L. Williams PhD Greta L. Heidner DVM Carol A. Novotney DVM Jim E. Riviere DVM PhD Mark W. Dewhirst DVM PhD Donald E. Thrall DVM PhD 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》1993,7(4):235-240
Thirty dogs with spontaneously occurring malignant neoplasms were treated monthly with carboplatin (CBDCA) given as a 30-minute intravenous infusion in a dose escalation study. Twenty-eight dogs were considered evaluable for toxicity. The maximally tolerated dose of CBDCA was conceptually defined as that dose, determined by logistic regression analyses of toxicity data, resulting in a 50% incidence of moderate toxicity (MOD50) or a 5% incidence of severe toxicity (SEV5). Each designated maximally tolerated dose was calculated for the first course of treatment only and for the first and second courses of treatment combined to estimate cumulative drug toxicity. The MOD50 and SEV5 for the first treatment course were 340 and 278 mg/M2, respectively. MOD50 and SEV5 values for the first plus second treatment courses were 327 and 231 mg/M2, respectively. The nadir of neutrophil and platelet counts occurred approximately 14 days after treatment. The mean neutrophil and platelet values for all dogs experiencing myelosuppression during the first two treatment courses were 1541/μL and 62,600/μL, respectively. Nonparametric pharmacokinetic analysis of plasma CBDCA values suggested that half-life (T1/2), area-under-the-curve and total body clearance (CLb) were not dose dependent. Volume of distribution (VDss) significantly increased with dose only between 100 and 150 mg/M2, not between 150 and 300 mg/M2. Dose-independent serum CBDCA pharmacokinetic disposition indicates that detailed investigation of tissue CBDCA distribution would be warranted and may identify novel dosing strategies that could improve the therapeutic index of CBDCA by minimizing toxicity. (Journal of Veterinary Internal Medicine 1993; 7:235–240. Copyright © 1993 by the American College of Veterinary Internal Medicine.) 相似文献
7.
8.
C. E. Cornelius B. A. Myers M. L. Bruss J. W. George 《Veterinary research communications》1989,13(5):395-401
Fasted Brazilian squirrel monkeys (BrSMs) exhibited slightly higher serum bilirubin levels (0.30±0.05 mg/dl) than others in the fed state (0.13±0.01). The mean liver weight was 50% lower following a 22 h fast. The rate of bile flow was unaffected by fasting and averaged 13.8 l/min/kg and 47.5 l/min/100g liver in six BrSMs. No significant difference in mean bilirubin excretion/min was observed on a body weight basis following fasting. When the mean rate of bilirubin excretion was calculated as a function of liver weight, a two-fold higher rate was present in fasted monkeys, but only at the p=0.06 level of statistical significance. From data collected in this and earlier studies, it would appear that BrSMs represent the best animals studied to date to serve as experimental controls in comparative studies with Bovilian squirrel monkeys which exhibit a Gilbert-like syndrome. 相似文献
9.
M. Angeles Achon Vicente Medina Michael Shanks Peter Markham George P. Lomonossoff 《European journal of plant pathology / European Foundation for Plant Pathology》1994,100(2):157-165
In order to characterise and classify an unknown maize-infecting potyvirus isolated from fields in northeast Spain, the entire coat protein gene and the C-terminal twothirds of the large nuclear inclusion protein (NIb) gene were cloned and sequenced. Protein sequencing enabled the cleavage site between the two proteins to be deduced and also revealed that on storage the viral coat protein undergoes a specific degradation in which the N-terminal 39 amino acids are removed. Comparison of the nucleotide sequence of the 3 non-coding region of the viral RNA and the predicted amino acid sequence of the coat protein with the equivalent regions of other members of the potyvirus group revealed that the Spanish virus is closely related to maize dwarf mosaic virus strain A. 相似文献
10.
A. Schots J. De Boer A. Schouten J. Roosien J. F. Zil Verentant H. Pomp L. Bouwman-Smits H. Overmars F. J. Gommers B. Visser W. J. Stiekema J. Bakker 《European journal of plant pathology / European Foundation for Plant Pathology》1992,98(2):183-191
Engineering resistance against various diseases and pests is hampered by the lack of suitable genes. To overcome this problem we started a research program aimed at obtaining resistance by transfecting plants with genes encoding monoclonal antibodies against pathogen specific proteins. The idea is that monoclonal antibodies will inhibit the biological activity of molecules that are essential for the pathogenesis. Potato cyst nematodes are chosen as a model and it is thought that monoclonal antibodies are able to block the function of the saliva proteins of this parasite. These proteins are, among others, responsible for the induction of multinucleate transfer cells upon which the nematode feeds. It is well documented that the ability of antibodies to bind molecules is sufficient to inactivate the function of an antigen and in view of the potential of animals to synthesize antibodies to almost any molecular structure, this strategy should be feasible for a wide range of diseases and pests.Antibodies have several desirable features with regard to protein engineering. The antibody (IgG) is a Y-shaped molecule, in which the domains forming the tips of the arms bind to antigen and those forming the stem are responsible for triggering effector functions (Fc fragments) that eliminate the antigen from the animal. Domains carrying the antigen-binding loops (Fv and Fab fragments) can be used separately from the Fc fragments without loss of affinity. The antigen-binding domains can also be endowed with new properties by fusing them to toxins or enzymes. Antibody engineering is also facilitated by the Polymerase Chain Reaction (PCR). A systematic comparison of the nucleotide sequence of more than 100 antibodies revealed that not only the 3′-ends, but also the 5′-ends of the antibody genes are relatively conserved. We were able to design a small set of primers with restriction sites for forced cloning, which allowed the amplification of genes encoding antibodies specific for the saliva proteins ofGlobodera rostochiensis. Complete heavy and light chain genes as well as single chain Fv fragments (scFv), in which the variable parts of the light (VL) and heavy chain (VH) are linked by a peptide, will be transferred to potato plants. A major challenge will be to establish a correct expression of the antibody genes with regard to three dimensional folding, assembly and intracellular location. 相似文献