全文获取类型
收费全文 | 5505篇 |
免费 | 262篇 |
国内免费 | 4篇 |
专业分类
林业 | 423篇 |
农学 | 183篇 |
基础科学 | 35篇 |
1101篇 | |
综合类 | 877篇 |
农作物 | 231篇 |
水产渔业 | 344篇 |
畜牧兽医 | 2002篇 |
园艺 | 176篇 |
植物保护 | 399篇 |
出版年
2023年 | 33篇 |
2022年 | 54篇 |
2021年 | 84篇 |
2020年 | 135篇 |
2019年 | 126篇 |
2018年 | 135篇 |
2017年 | 121篇 |
2016年 | 130篇 |
2015年 | 110篇 |
2014年 | 131篇 |
2013年 | 259篇 |
2012年 | 303篇 |
2011年 | 382篇 |
2010年 | 220篇 |
2009年 | 168篇 |
2008年 | 310篇 |
2007年 | 317篇 |
2006年 | 291篇 |
2005年 | 289篇 |
2004年 | 264篇 |
2003年 | 271篇 |
2002年 | 256篇 |
2001年 | 64篇 |
2000年 | 71篇 |
1999年 | 82篇 |
1998年 | 56篇 |
1997年 | 53篇 |
1996年 | 54篇 |
1995年 | 39篇 |
1994年 | 47篇 |
1993年 | 49篇 |
1992年 | 39篇 |
1991年 | 46篇 |
1990年 | 46篇 |
1989年 | 42篇 |
1988年 | 38篇 |
1987年 | 39篇 |
1986年 | 54篇 |
1985年 | 32篇 |
1984年 | 43篇 |
1983年 | 35篇 |
1982年 | 36篇 |
1981年 | 27篇 |
1980年 | 20篇 |
1979年 | 23篇 |
1978年 | 27篇 |
1977年 | 26篇 |
1975年 | 20篇 |
1973年 | 24篇 |
1972年 | 20篇 |
排序方式: 共有5771条查询结果,搜索用时 0 毫秒
111.
Stepien RL Rapoport GS Henik RA Wenholz L Thomas CB 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2003,17(1):65-72
Comparison of test characteristics allows a clinician to choose the optimal diagnostic test method for an individual patient. This study assessed the comparative test characteristics of noninvasive (NI) blood pressure measurement methods (oscillometric and Doppler) and used this information to develop optimal cutoff values for diagnosis of systolic hypertension in dogs by these NI methods. Simultaneous NI (oscillometric or Doppler methods) and invasive (arterial puncture [AP]) systolic blood pressure (SBP) measurements were obtained prospectively from normal dogs and dogs suspected of having systemic hypertension based on clinical signs. Oscillometric SBP readings were obtained from the distal hind limb (Osc-L, n = 54) or the proximal tail (T. n = 27). Doppler BP measurements were obtained using a forelimb cuff (n = 57). AP-SBP was categorized as hypertensive if > or = 160 mmHg, and sensitivity (Se). specificity (Sp), and likelihood ratios (LR) were calculated for diagnostic cutoff values ranging from 130 to 220 mmHg. Receiver operator characteristic (ROC) curves were analyzed to determine optimal cutoff values for diagnosis of AP-SBP > or = 160 mmHg. Optimal NI SBP cutoff values considered to reflect AP values > or = 160 mmHg were: Osc-L = 160 mmHg (Se: 65%, Sp: 85%. LR = 4.33: 1), Osc-T = 150 mmHg (Se: 84%, Sp: 75%, LR = 3.36: 1), and Doppler = 160 mmHg (Se: 71%, 相似文献
112.
Bosken JM Tobin T Mundy GD Fisher M Gantz MG Banks RO 《Veterinary therapeutics : research in applied veterinary medicine》2003,4(3):292-298
Postrace urine samples from thoroughbred horses were examined to compare osmolality and specific gravity between horses treated with furosemide and those not treated. Samples were assigned to groups in relation to reported medication (furosemide) status, race finish position, and distance of race. Urine osmolality was significantly (P <.05) lower in samples from horses treated with furosemide when compared with untreated horses. Specific gravity determinations are less precise at measuring urine osmolality at lower levels (1.01 g/ml or less). The measurement of osmolality is a superior method for determining the urine solute concentration and facilitating the regulation of furosemide. 相似文献
113.
Adin CA Herrgesell EJ Nyland TG Hughes JM Gregory CR Kyles AE Cowgill LD Ling GV 《Journal of the American Veterinary Medical Association》2003,222(11):1576-1581
OBJECTIVE: o determine sensitivity and specificity of radiography, ultrasonography, and antegrade pyelography for detection of ureteral obstructions in cats. DESIGN: Retrospective study. ANIMALS: 11 cats. PROCEDURE: Medical records of cats that had radiography, ultrasonography, and antegrade pyelography performed for suspected ureteral obstructions were examined. Ultrasound-guided pyelocentesis and fluoroscopic-assisted antegrade pyelography were performed on 18 kidneys in 11 cats. Obstructive ureteral lesions were confirmed in all cats by surgical or necropsy examination. Sensitivity and specificity of survey radiography, ultrasonography, and antegrade pyelography for identification of ureteral obstructions were calculated. Surgical or necropsy findings were used as the standard for comparison. RESULTS: All cats were azotemic. Mean +/- SD serum creatinine and BUN concentrations were 10.2 +/- 6.1 and 149 +/- 82 mg/dL, respectively. Fifteen of 18 ureters were found to be obstructed at surgery or necropsy. Sensitivity and specificity were 60 and 100% for radiography and 100 and 33% for ultrasonography, respectively, in identification of ureteral obstructions. Leakage of contrast material developed in 8 of 18 kidneys during antegrade pyelography and prevented diagnostic interpretation in 5 of 18 studies. For the 13 diagnostic studies, specificity and sensitivity were 100% by use of the antegrade pyelography technique. Correct identification of the anatomic location of the ureteral obstruction was obtained in 100% of diagnostic antegrade pyelography studies and in 60% of radiography or ultrasonography studies. CONCLUSIONS AND CLINICAL RELEVANCE: Antegrade pyelography can be a useful alternative in the diagnosis and localization of ureteral obstructions in azotemic cats, although leakage of contrast material may prevent interpretation of the study. 相似文献
114.
Grubb TL Schlipf JW Riebold TW Cebra CK Poland L Zawadzkas X Mailhot N 《Journal of the American Veterinary Medical Association》2003,223(8):1167-1169
OBJECTIVE: To determine the minimum alveolar concentration (MAC) of sevoflurane in spontaneously breathing llamas and alpacas. DESIGN: Prospective study. ANIMALS: 6 healthy adult llamas and 6 healthy adult alpacas. PROCEDURE: Anesthesia was induced with sevoflurane delivered with oxygen through a mask. An endotracheal tube was inserted, and a port for continuous measurement of end-tidal and inspired sevoflurane concentrations was placed between the endotracheal tube and the breathing circuit. After equilibration at an end-tidal-to-inspired sevoflurane concentration ratio > 0.90 for 15 minutes, a 50-Hz, 80-mA electrical stimulus was applied to the antebrachium until a response was obtained (ie, gross purposeful movement) or for up to 1 minute. The vaporizer setting was increased or decreased to effect a 10 to 20% change in end-tidal sevoflurane concentration, and equilibration and stimulus were repeated. The MAC was defined as the mean of the lowest end-tidal sevoflurane concentration that prevented a positive response and the highest concentration that allowed a positive response. RESULTS: Mean +/- SD MAC of sevoflurane was 2.29 +/- 0.14% in llamas and 2.33 +/- 0.09% in alpacas. CONCLUSIONS AND CLINICAL RELEVANCE: The MAC of sevoflurane in llamas and alpacas was similar to that reported for other species. 相似文献
115.
116.
Steinbach G Methner U Springer S Lindner T Selbitz HJ 《Berliner und Münchener tier?rztliche Wochenschrift》2003,116(3-4):124-129
LPS antibody reaction of S. Typhimurium was detected in a total of 111 two- to ten-week-old pigs, which had been exposed to experimental oral infection with this serovar in 16 separate experiments. The total antibody level was determined according to the meat juice ELISA provided for the Salmonella control programme and the antibody concentrations of the isotopes IgG1, IgG2, IgA and IgM. Although there were significant differences between the individual experiments with respect to the reaction intensity and proportion of the individual immune globulin isotypes, the following general statements on the dynamics of the antibody reaction can be made: Clearly elevated antibody levels could be observed one week after the onset of infection. After one and two weeks, respectively, 22.5 and 52.9% of the infected animals showed antibody levels which were to be evaluated as positive in the sense of the Salmonella control programme (> or = 40%). While the concentration of the IgM-related antibodies decreased again during the second week already, the antibody concentration of IgG1 and IgG2 continued to increase until the end of the experiment after 3 weeks. The clear differences in the reactions between the experiments cannot be explained solely by defined conditions of infection such as strain of infection, infective dose or age of the pigs. Obviously, other non-defined or non-recognized factors may have a decisive influence on the dynamics of the antibody reaction in the animal groups. 相似文献
117.
Kinzel S Hein S Stopinski T Koch J Buecker A Treusacher HP Schmachtenberg A Jansen T Eble M Küpper W 《Berliner und Münchener tier?rztliche Wochenschrift》2003,116(3-4):134-138
This study describes the experience with hypofractionated radiation therapy of squamous cell carcinoma and melanoma in dogs and cats. A total dose of 32-48 Gray (Gy) was delivered once a week in 8 Gy fractions. 34 animals in which a complete surgical excision was impossible were treated. There was no tumor detectable macroscopically in 14 patients at the beginning of radiation therapy. In 20 animals the median volume of the tumor was 9.9 cm3. The median survival times and the local tumor control of squamous cell carcinoma of the oral and nasal cavities and of the body are comparable to results which were reached with a Monday-Wednesday-Friday scheme. For the treatment of Melanoma the hypofractionated radiation therapy is first choice. There are no significant side effects. Late side effects did not occur. 88% of the owners are satisfied with this kind of treatment and would choose it again. 相似文献
118.
119.
120.
Adherence to various host cell lines of Mycoplasma bovis strains differing in pathogenic and cultural features 总被引:1,自引:0,他引:1
Thomas A Sachse K Dizier I Grajetzki C Farnir F Mainil JG Linden A 《Veterinary microbiology》2003,91(2-3):101-113
Mycoplasma bovis is known to be responsible for pneumonia and arthritis in calves, as well as mastitis in dairy cows. Despite clear evidence of its pathogenic potential, little is known about mechanisms of cytadherence and the molecular factors involved. The purpose of this work was to compare adherence rates of M. bovis field strains to different host cell lines and study the effects of cloning and sub-culturing M. bovis strains on their adherence properties. Eighteen metabolically labeled M. bovis strains isolated from different pathological backgrounds were examined in adherence trials using four different host cell lines, i.e. embryonic bovine lung (EBL), embryonic bovine trachea (EBTr), Madin Darby bovine kidney (MDBK) and rabbit kidney (RK) cells. Although large interstrain variations in adherence rates (3.4-19.1%) were measured they could not be correlated to the pathological background (pneumonia, arthritis or mastitis). Adherence rates to the fibroblast cell line (EBTr) were significantly lower than those to the three epithelial cell lines (EBL, MDBK and RK). The only non-pathogenic strain (221/89) exhibited lower adherence rates than three isolates from clinical mastitis. Interestingly, adherence rates were significantly reduced after in vitro passaging. In contrast, no effect of single cloning of strains on adherence was observed. There was no general correlation between expression of variable surface proteins (Vsps) as monitored by immunoblotting and adherence rates, although alterations in Vsp expression profiles were seen as a consequence of passaging. As there is probably a large number of adhesins, variable and non-variable, on the surface of M. bovis cells the issue is very complex, and the most active components have yet to be identified. 相似文献