全文获取类型
收费全文 | 112794篇 |
免费 | 5613篇 |
国内免费 | 79篇 |
专业分类
林业 | 5292篇 |
农学 | 3650篇 |
基础科学 | 738篇 |
12737篇 | |
综合类 | 20193篇 |
农作物 | 4289篇 |
水产渔业 | 5130篇 |
畜牧兽医 | 58826篇 |
园艺 | 1306篇 |
植物保护 | 6325篇 |
出版年
2018年 | 1380篇 |
2017年 | 1476篇 |
2016年 | 1430篇 |
2015年 | 1230篇 |
2014年 | 1448篇 |
2013年 | 3951篇 |
2012年 | 2764篇 |
2011年 | 3350篇 |
2010年 | 2208篇 |
2009年 | 2083篇 |
2008年 | 3173篇 |
2007年 | 3149篇 |
2006年 | 3053篇 |
2005年 | 2925篇 |
2004年 | 2761篇 |
2003年 | 2810篇 |
2002年 | 2667篇 |
2001年 | 3447篇 |
2000年 | 3343篇 |
1999年 | 2677篇 |
1998年 | 1124篇 |
1997年 | 1072篇 |
1995年 | 1194篇 |
1994年 | 1065篇 |
1992年 | 2351篇 |
1991年 | 2552篇 |
1990年 | 2663篇 |
1989年 | 2579篇 |
1988年 | 2438篇 |
1987年 | 2384篇 |
1986年 | 2344篇 |
1985年 | 2294篇 |
1984年 | 1911篇 |
1983年 | 1596篇 |
1982年 | 1170篇 |
1981年 | 1059篇 |
1979年 | 1800篇 |
1978年 | 1427篇 |
1977年 | 1203篇 |
1976年 | 1199篇 |
1975年 | 1272篇 |
1974年 | 1631篇 |
1973年 | 1581篇 |
1972年 | 1652篇 |
1971年 | 1564篇 |
1970年 | 1528篇 |
1969年 | 1311篇 |
1968年 | 1100篇 |
1967年 | 1259篇 |
1966年 | 1094篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
Red foxes ( Vulpes vulpes ) are a major pest species in Europe and Australia. Traditional methods of control such as hunting or poisoning are no longer sufficient or feasible. As with domestic dogs and cats, prolactin (PRL) in the vixen is an essential luteotropin during the second half of gestation. Hence, PRL inhibitors such as cabergoline have been used to induce abortions. Eighteen mated silver fox vixens (three groups of six foxes each) were treated orally with a placebo of paraffin oil (I), or with 15 μ g/kg cabergoline in feed once (II) or twice (III), on day 30 (I and II) or days 30 and 32 (III) post-coitum. Blood samples were taken prior to and after treatments and concentrations of PRL and progesterone (P4 ) were determined. Normal parturitions were observed in five of six, five of six and two of six vixens in groups I, II and III, respectively. In group III plasma concentrations of PRL and P4 decreased significantly but only temporarily. This drop in hormone concentrations was more pronounced in the vixens that did not carry to term. In conclusion, doses in excess of 15 μ g/kg of cabergoline are likely to prevent the development of fetuses to term in pregnant vixens. 相似文献
142.
D A Ward K S Latimer R M Askren 《Journal of the American Veterinary Medical Association》1992,200(10):1503-1506
Squamous cell carcinoma is an uncommon tumor of the cornea in dogs. A 12-year-old Shih Tzu with a history of chronic keratoconjunctivitis sicca was diagnosed as having squamous cell carcinoma of the corneoscleral limbus. The lesion was treated by surgical resection and cryotherapy. One year after surgery, multiple tumors, apparently unrelated to the first tumor, appeared on the same cornea. Keratoconjunctivitis sicca may have predisposed the dog to corneal squamous cell carcinoma development. 相似文献
143.
Martin W. Brunson Richard W. Taylor Bert J. Hoff 《Journal of the World Aquaculture Society》1988,19(1):8-13
Twenty-five domestic rice (Oryza sativa L.) cultivars were evaluated in a simulated rice/crawfish double cropping system in southwest Louisiana during 1983 and 1984. Wide variation was observed among cultivars in parameters believed to be important for maximizing productivity in such a system. Mean maturity ranged from 99 (Labelle) to 118 days (Starbonnet), while height ranged from 76 (Bellemont) to 130 cm (Della, Nato). Significant differences in grain yield response were observed, with yields ranging from 4,101 (Bluebelle) to 6,665 kg/hectare (Newbonnet). Straw dry matter production varied greatly, from 3,831 (Bellemont) to 9,170 kg/hectare (Della), and was positively correlated with plant height (r = 0.64; P = 0.0001). Ratoon biomass production was negatively correlated with both grain yield (r = -0.39; P = 0.0001) and maturity group (r = -0.69; P = 0.0001). Plant senescence at grain maturity also varied greatly and appears to be a factor in post-harvest ratoon capability. Early or very early maturing cultivars with both proven grain production and good ratooning capability appear best suited. Cultivar selection should be based upon individual farm situations and currently employed agronomic practices. 相似文献
144.
W. Riess 《European Journal of Forest Research》1992,111(1):236-242
Zusammenfassung Das bayerische Arten- und Biotopschutzprogramm (ABSP) wird seit 1984 auf der Basis der naturr?umlichen Gegebenheiten erarbeitet
und jeweils landkreisbezogen dargestellt. über die H?lfte der 71 bayerischen Landkreise ist vollst?ndig bearbeitet. In der
ersten Arbeitsphase wurden nur die innerhalb der Naturschutzverwaltung zug?nglichen Datenquellen ausgewertet. Neuerdings werden
in Absprache mit der Obersten Forstbeh?rde verst?rkt forstliche Informationen eingearbeitet. Bereits herausgegebene ?ltere
B?nde werden aktualisiert.
Das Programm hat keine unmittelbare Rechtswirksamkeit. Die Forstbeh?rden und Waldbesitzer sind aufgerufen, die im Programm
dargestellten Ziele des Arten- und Biotopschutzes zu unterstützen.
Diese umfassen u. a. die verst?rkte fachliche Zusammenarbeit, die Erhaltung und F?rderung von Sonderstandorten, Alt- und Totholz,
die Reduktion der Wilddichte und die Vermehrung der Waldfl?che.
Bavaria's program for the protection of species and biotopes, and its effects on forestry
Summary Bavaria's program for the protection of species and biotopes (ABSP) is being worked out since 1984, by counties, on the basis of given natural environmental conditions. Work has been completed for more than half of the 71 Bavarian counties. During the first phase of the work, only data sources of the nature conservation authorities were evaluated. More recently, also forestry-related information is increasingly incorporated in agreement with the State's top forestry authorities. Already issued volumes are updated. The program has no direct legal status. Forestry authorities and woodland owners are called upon to support the program's objectives of species and biotope protection. Such are, amongst others: increased professional cooperation; preservation and promotion of special sites, old timber and dead snags; reduction of game animal population densities; and increase of woodland areas.相似文献
145.
Twenty-nine pruritic, atopic dogs were entered into a double-blind, placebo-controlled, crossover study to evaluate the efficacy of an investigational antiallergenic compound, AHR-13268. Fourteen dogs were evaluated by a veterinary dermatologist (at intervals) and the owner (daily). Fifteen dogs were evaluated only by the owner. The mean (+/- SE) owner scores for pruritus, erythema, and lesions with placebo treatment (higher score = worse signs) were 3.24 (+/- 0.12), 2.73 (+/- 0.12), and 2.61 (+/- 0.09), respectively. With drug treatment, the corresponding scores were 2.89 (+/- 0.12), 2.50 (+/- 0.12), and 2.25 (+/- 0.09). Scores for pruritus and lesions (but not erythema) were significantly better with drug treatment than with placebo treatment. Investigator scores showed similar trends, but the differences were not great enough to be statistically significant. Overall, 11/29 (38%) owners reported their dogs had moderate or better improvement from drug capsules, and 4/29 dogs (14%) improved on placebo capsules. A variety of adverse effects were reported following both drug (9/29 dogs) and placebo (8/29 dogs) capsule administration, but were mild and well tolerated. Results of this study indicate that AHR-13268 has potential for empiric treatment of allergic inhalant dermatitis in some dogs. 相似文献
146.
Two cases of H.c.c. which occurred in winter 1987 in Vienna are described. Case one was a female Chow-Chow, 8 weeks of age, that died from the peracute form of the disease. The diagnosis was confirmed by histology and direct immunofluorescence. Case two, a 9-month old female Kuvacz, showed clinical signs of the subacute form of H.c.c. She was hospitalized and therapy was successful. The disease was diagnosed by the typical clinical signs and the raise of antibodies in paired serum samples. Etiology, clinical signs and immunology of H.c.c. are discussed. 相似文献
147.
P R Widders S C Dowling R P Gogolewski J W Smith L B Corbeil 《Research in veterinary science》1989,46(2):212-217
Bovine antibody responses to Haemophilus somnus were compared on the basis of clinical and bacteriological findings. Serum IgG1 and IgM antibody titres were significantly increased in clinically normal cattle that were bacteriologically positive for H somnus from the nasal or vaginal mucosae compared with clinically normal, negative cows. IgG2 titres did not differ significantly between these two groups. However, IgG2 antibody was significantly higher in animals with H somnus disease (pneumonia or abortion) than in clinically normal cattle (whether bacteriologically positive or negative), while IgG1 and IgM titres did not differ between diseased and bacteriologically positive, clinically normal cattle. These antibody trends were duplicated in experimental H somnus abortion or pneumonia, with the greatest response occurring within the IgG2 subclass. Cattle vaccinated systemically with killed whole H somnus produced a predominant IgG2 response with minimal IgG1 and IgM responses. These results demonstrate that IgG2 antibody is consistently elevated in H somnus disease, and suggest that this response may be useful in discriminating diseased from asymptomatic cattle. 相似文献
148.
Bilateral nephrolithiasis with intermittent ureterolithiasis was diagnosed in a 7-year old Holstein cow. Two episodes of ureterolithiasis resulted in severe azotemia which resolved after spontaneous movement of the stone. A third episode of obstruction one year after the initial episode resulted in rupture of one kidney, necessitating euthanasia. The histopathological examination of the kidney was diagnostic for chronic pyelonephritis. Corynebacterium sp. was cultured from a nephrolith. In this case it is believed that the chronic pyelonephritis predisposed to the calculi formation. 相似文献
149.
Evaluation of full cortical allografts in 25 dogs 总被引:1,自引:0,他引:1
K R Sinibaldi 《Journal of the American Veterinary Medical Association》1989,194(11):1570-1577
Twenty-five dogs received 26 cortical allografts from Apr 9, 1976 through Jan 31, 1982. Cortical allografts were used to reconstruct fractures of the femur, humerus, tibia, radius, and ulna. These grafts were used to replace comminuted fragments; to lengthen bones; to correct malunions, delayed unions, and nonunions; and in one case, to replace bone lost to sequestrum formation in an infected fracture site. All fractures were stabilized by use of standard ASIF techniques and dynamic compression plates. Frozen bone allografts were used in all cases. These were harvested aseptically and stored in a household freezer for 3 days to one year before use. Clinically normal function was achieved in 96% of the dogs. 相似文献
150.
Uterine response to inoculation with Streptococcus zooepidemicus organisms, 51Cr-labeled 15-microns microspheres, and charcoal was evaluated in 9 mares (4 resistant and 5 susceptible to endometritis) to determine mechanical and cellular clearance rates during the early postovulatory period. Mares were inoculated at estrus prior to ovulation during estrous cycles 1, 3, and 5. Uterine swab specimens for aerobic and anaerobic bacteriologic culture and serum for progesterone determination were obtained on postovulation day 3 during estrous cycle 1, on the day of ovulation during estrous cycle 3, and on postovulation day 5 during estrous cycle 5. Immediately thereafter, the uterus was irrigated with 50 ml of sterile physiologic saline solution containing tracer amounts of 125I-labeled human serum albumin. Streptococcus zooepidemicus was isolated from 10 of 15 (67%) uterine specimens collected from susceptible mares and incubated aerobically. Escherichia coli also was isolated from 2 of the 10 specimens incubated aerobically. Anaerobic bacteriologic culture of specimens from all mares yielded no growth. Chromium-labeled microspheres were recovered twice from 2 susceptible mares, on day 0 and day 5. Charcoal was retained in 5 specimens collected from 3 susceptible mares. Bacteriologic culture of specimens from resistant mares did not yield growth. On day 0, chromium-labeled microspheres and charcoal were recovered once from 1 resistant mare. Mares susceptible to endometritis accumulated more fluid within the uterine lumen after ovulation than did resistant mares (mean +/- SEM, 52.73 +/- 15.22 ml and 7.41 +/- 1.96 ml, respectively; P less than 0.01). From this study, it appeared that uterine cellular and bactericidal mechanisms are dysfunctional during the early postovulatory period. However, there appeared to be no disruption of the mechanisms responsible for mechanical clearance of materials inoculated in the uterus. 相似文献