全文获取类型
收费全文 | 84138篇 |
免费 | 4710篇 |
国内免费 | 57篇 |
专业分类
林业 | 2935篇 |
农学 | 2283篇 |
基础科学 | 565篇 |
9285篇 | |
综合类 | 14909篇 |
农作物 | 3102篇 |
水产渔业 | 3911篇 |
畜牧兽医 | 45934篇 |
园艺 | 898篇 |
植物保护 | 5083篇 |
出版年
2018年 | 1045篇 |
2017年 | 1179篇 |
2016年 | 1098篇 |
2015年 | 951篇 |
2014年 | 1191篇 |
2013年 | 3073篇 |
2012年 | 2165篇 |
2011年 | 2749篇 |
2010年 | 1678篇 |
2009年 | 1772篇 |
2008年 | 2612篇 |
2007年 | 2426篇 |
2006年 | 2432篇 |
2005年 | 2152篇 |
2004年 | 2099篇 |
2003年 | 2095篇 |
2002年 | 1979篇 |
2001年 | 2707篇 |
2000年 | 2805篇 |
1999年 | 2137篇 |
1998年 | 815篇 |
1997年 | 829篇 |
1996年 | 814篇 |
1995年 | 1018篇 |
1994年 | 892篇 |
1993年 | 843篇 |
1992年 | 1933篇 |
1991年 | 2085篇 |
1990年 | 1926篇 |
1989年 | 1936篇 |
1988年 | 1825篇 |
1987年 | 1930篇 |
1986年 | 1976篇 |
1985年 | 1872篇 |
1984年 | 1483篇 |
1983年 | 1298篇 |
1982年 | 882篇 |
1979年 | 1367篇 |
1978年 | 1123篇 |
1977年 | 974篇 |
1976年 | 937篇 |
1975年 | 983篇 |
1974年 | 1272篇 |
1973年 | 1298篇 |
1972年 | 1234篇 |
1971年 | 1147篇 |
1970年 | 1088篇 |
1969年 | 964篇 |
1968年 | 832篇 |
1967年 | 869篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
221.
Byron JK Chew DJ McLoughlin ML 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2011,25(5):980-984
Background: Transurethral collagen injections are an alternative treatment for canine urinary incontinence. There is controversy regarding the long‐term effectiveness of collagen and the impact urethral coaptation and injection site have on outcome. Hypothesis/Objectives: To evaluate outcome and client satisfaction after urethral collagen injections, and correlation between degree of urethral coaptation and collagen placement with outcome. Animals: Thirty‐six procedures on 31 dogs, 10 with ureteral ectopia. Methods: Retrospective review of records and video evaluation of injection procedures. Follow‐up communication with owners was performed between 1 and 56 months after bovine cross‐linked collagen implantation to evaluate duration of continence, need for additional medical therapy, and owner satisfaction. Continence score was evaluated before and after the procedure, and after additional medical therapy, if needed. Injection location and degree of urethral coaptation was assessed with respect to duration of continence. Results: Dogs had a significant increase in continence score after the procedure. Mean (SD) duration of continence in dogs without addition of medication was 16.4 (15.2) months, and 5.2 (4.3) months in dogs needing additional medical therapy. No significant difference was found with respect to degree of coaptation. Median client satisfaction with the procedure was 100%. Conclusions and Clinical Importance: Transurethral collagen implantation may be a viable option for treatment of female dogs with urethral sphincter mechanism incompetence, particularly after medical failure. Duration and degree of improvement are variable. Client satisfaction was excellent despite lack of complete continence in some dogs, and highlights the importance of discussing outcome expectations with owners. 相似文献
222.
Danyi S Widart J Douny C Dang PK Baiwir D Wang N Tu HT Tung VT Phuong NT Kestemont P Scippo ML 《Journal of veterinary pharmacology and therapeutics》2011,34(2):142-152
Determination and kinetics of enrofloxacin and ciprofloxacin in Tra catfish (Pangasianodon hypophthalmus) and giant freshwater prawn (Macrobrachium rosenbergii) using a liquid chromatography/mass spectrometry method. J. vet. Pharmacol. Therap. 34, 142-152. The fluoroquinolones enrofloxacin (EF) and ciprofloxacin (CF) residues were investigated in the edible tissues of two important Asian aquacultured species such as Tra catfish (Pangasianodon hypophthalmus) and giant freshwater prawn (Macrobrachium rosenbergii) using a sensitive liquid chromatography-electrospray ionization-tandem mass spectrometry method. Fish and prawn were treated with medicated feed with multiple doses of EF, in field conditions. A validation study of the analytical method was realized in terms of linearity, specificity, precision (repeatability and within-laboratory reproducibility), recovery and decision limit (CCα). The time needed before the antibiotic disappears from animal tissues or reach the maximum residue limit (MRL, 100μg/kg) was assessed. The concentration values of EF detected in Tra catfish tissue were between the MRL and 2×MRL concentrations, according to the fish density, 7days following the end of the enrofloxacin treatment (20mg/kg body weight per day, for seven consecutive days). The concentration value of ER in prawn tissue was lower than the MRL and the limit of quantification (LOQ, 14μg/kg) 5 and 7days after the stop of the EF treatment (50mg/kg body weight per day, for five consecutive days), respectively. The mean detected levels of CF was much lower in comparison with that of EF, indicating that only a small part of EF is metabolized into CF (<5%) in both Tra catfish and prawn. 相似文献
223.
224.
Megaesophagus, hypercalcemia, and eosinophilia associated with glucocorticoid deficiency were detected in a 5-year-old neutered female Standard Poodle with concurrent hypothyroidism. Clinical and biochemical abnormalities resolved with glucocorticoid replacement treatment, and the dog was normal 29 months after diagnosis. The dog's breed and sex and the existence of a second endocrinopathy supported an underlying immunologic disorder. 相似文献
225.
R N Arnold K K Scheller S C Arp S N Williams D R Buege D M Schaefer 《Journal of animal science》1992,70(10):3055-3065
Three experiments were conducted to examine the effects of vitamin E supplementation on feedlot cattle. Vitamin E supplementation did not affect feedlot performance or carcass characteristics of cattle fed a high-concentrate diet (P greater than .1). The major finding was the effectiveness of vitamin E in extending the color stability of displayed beef (P less than .01). Color stability during display of longissimus lumborum steaks from cattle supplemented with 300 IU/d for 266 d, 1,140 IU/d for 67 d, or 1,200 IU/d for 38 d was extended by 2.5 to 4.8 d. Gluteus medius steaks had an extended color display life of 1.6 to 3.8 d. The accumulation of lipid oxidation products, but not aerobic microbes, associated with displayed longissimus lumborum was suppressed for muscle from vitamin E-supplemented steers. Taste panelists detected no difference among longissimus lumborum steaks from control and vitamin E-supplemented steers but found (P less than .01) steaks aged for 21 d to be more tender than steaks aged for 7 d. Supplementing cattle with vitamin E should reduce economic losses associated with discolored beef during retail display. 相似文献
226.
J D Mogollon C Pijoan M P Murtaugh P P Cleary J E Collins 《Research in veterinary science》1992,53(2):244-246
Previous reports have suggested that the surface proteins found in meningeal strains of Streptococcus suis might be similar to the M protein of group A streptococci. Fifty-five strains of S suis, including human and swine meningeal and pneumonic isolates, were tested for M protein genes by DNA probes representing the constant domain of the 3' end of the group A, M protein gene. None of the S suis strains examined was positive, indicating that these organisms either lack M protein genes or harbour different genes, not expressing the constant domains of protein M from group A. 相似文献
227.
K L Angel J Schumacher D F Wolfe P H Klesius J W Tyler R L Carson 《American journal of veterinary research》1992,53(1):78-82
The effects of subcutaneous administration of a commercially available estradiol 17 beta implant on hematologic values and the chemiluminescence response of neutrophils were evaluated in 14 steers. Chemiluminescence and hematologic values were measured in treated (n = 8) and nontreated (n = 6) steers on days -14, -7, and -1 prior to implantation. Estradiol 17B was implanted into the treated group of steers on day 0, and blood samples were obtained from all steers on days 1, 2, 3, 4, 8, 15, 22, 29, 36, 43, and 50. The concentration of estrogen in serum was significantly (P = 0.0120) higher following implantation. Chemiluminescence and hematologic indices were not significantly affected by either implant status or serum concentrations of estrogen. The results of this study suggested that the use of implants containing estradiol 17 beta for promotion of weight gain in steers will not result in alterations of hematologic values or the neutrophil respiratory burst. 相似文献
228.
Testicular regrowths were observed in 10 of 21 tom turkeys between 28 and 32 weeks old, which was between 19 and 23 weeks after surgical caponization at 9 weeks of age. Regrowths were not observed in younger caponized toms. Two types of histologic patterns that differed from the normal pattern were observed in these regrowths. The first pattern was observed in seven regrowths and was characterized by a higher density of seminiferous tubules and more interstitial cells. The second pattern was seen in three regrowths and was characterized by extensive intertubular fibrosis, tubular detachment, and an increased number of interstitial cells. No correlation was found between the presence of these regrowths and plasma testosterone levels. The interstitial cell hyperplasia in all regrowths possibly was related to a diminished negative feedback by the endogenous testosterone on the release of luteinizing hormone from the pituitary. The appearance of regrowths at this age probably was related to the onset of normal physiological puberty. 相似文献
229.
S D White R A Rosychuk T A Janik P Denerolle P Schultheiss 《Journal of the American Veterinary Medical Association》1992,200(9):1377-1380
Clinical signs, laboratory findings, and treatment results of 40 cats with the histologic diagnosis of plasma cell stomatitis-pharyngitis are discussed. Median age was 7.1 years, with no discernable sex predilection. Anorexia and difficulty prehending food were the most common clinical signs. Hyperproteinemia with associated hyperglobulinemia was the most common laboratory finding. Of various treatments, administration of corticosteroids or injectable gold (aurothioglucose) proved most effective in controlling the clinical signs. 相似文献
230.
To investigate possible circadian and ultradian periodicities for peripheral insulin and urea in lactating dairy cows, integrated 15-min blood samples were taken sequentially over 48 hr from six cows. In addition, radiotelemetry measurements of body temperature were averaged over the same 15-min periods. Cows were housed in an environmental chamber at 19 degrees C with lights on 0700 to 2300 hr; fed daily at 0900 hr; and milked at 0800 and 2000 hr. For five of the six cows, body temperature showed a circadian rhythm peaking at 2323 hr with an amplitude of 0.34 degree C. For the sixth cow, body temperature was 180 degrees out-of-phase, peaking at 1230 hr with an amplitude of 0.12 degree C. Circadian rhythms for insulin and urea were consistent for all six cows peaking at 1743 hr with an amplitude of 0.74 ng/ml for insulin and at 1034 hr with an amplitude of 3.83 mM for urea. Body temperature and insulin also displayed episodic increases that often exceeded the amplitudes of circadian rhythms. For body temperature, a broad increase in spectral power was seen for periods between 100 and 175 min; time intervals between peaks averaged around 100 min. For insulin, power spectra for individual cows universally indicated rhythms with periods of approximately 45 and 80 min; time intervals between peaks averaged approximately 65 min. For urea, almost all spectral energy was confined to the 24-hr rhythm, although there was evidence of a low-amplitude, 60-min rhythm. In conclusion, when animals are acclimated to a rigidly controlled environment and frequent blood sampling is accomplished with minimal intervention, it is possible to detect rhythms inherent in the regulation of metabolic variables. 相似文献