全文获取类型
收费全文 | 17036篇 |
免费 | 898篇 |
国内免费 | 17篇 |
专业分类
林业 | 828篇 |
农学 | 558篇 |
基础科学 | 122篇 |
2505篇 | |
综合类 | 2663篇 |
农作物 | 911篇 |
水产渔业 | 950篇 |
畜牧兽医 | 8309篇 |
园艺 | 197篇 |
植物保护 | 908篇 |
出版年
2020年 | 161篇 |
2019年 | 182篇 |
2018年 | 310篇 |
2017年 | 365篇 |
2016年 | 261篇 |
2015年 | 198篇 |
2014年 | 316篇 |
2013年 | 664篇 |
2012年 | 496篇 |
2011年 | 620篇 |
2010年 | 428篇 |
2009年 | 410篇 |
2008年 | 628篇 |
2007年 | 553篇 |
2006年 | 513篇 |
2005年 | 453篇 |
2004年 | 420篇 |
2003年 | 429篇 |
2002年 | 369篇 |
2001年 | 486篇 |
2000年 | 475篇 |
1999年 | 373篇 |
1998年 | 180篇 |
1997年 | 201篇 |
1996年 | 156篇 |
1995年 | 192篇 |
1993年 | 164篇 |
1992年 | 280篇 |
1991年 | 313篇 |
1990年 | 307篇 |
1989年 | 312篇 |
1988年 | 289篇 |
1987年 | 246篇 |
1986年 | 295篇 |
1985年 | 253篇 |
1984年 | 209篇 |
1983年 | 207篇 |
1979年 | 250篇 |
1978年 | 165篇 |
1977年 | 155篇 |
1975年 | 171篇 |
1974年 | 234篇 |
1973年 | 215篇 |
1972年 | 251篇 |
1971年 | 230篇 |
1970年 | 203篇 |
1969年 | 192篇 |
1968年 | 158篇 |
1967年 | 160篇 |
1966年 | 161篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
991.
P T Oberem S R Van Amstel O Matthee J D Bezuidenhout 《The Onderstepoort journal of veterinary research》1985,52(4):283-287
Natural and experimental cases of sweating sickness were treated using a hyperimmune serum as specific treatment and hyperimmune serum combined with symptomatic and supportive treatment based on the clinicopathological changes observed in cases of sweating sickness. The treatment regimens were found to be highly effective in pigs and sheep as well as in calves, although recovery in the latter species was slower. 相似文献
992.
Chicks from lines selectively bred for either high or low antibody response post-primary immunization (PPI) to sheep erythrocytes (SRBC) and their reciprocal crosses were immunized intravenously with 0.1 ml of 0.25% SRBC antigen in Trials 1 and 3 and with 0.1 ml of 0.025%, 0.25%, or 25% SRBC antigen in Trial 2. All initial immunizations were made at 35 days of age, and 0.1 ml of 0.25% SRBC booster dose was given 24 days later. Results showed that (a) population differences appeared by day 4 PPI and persisted through day 24 PPI, (b) regardless of population, peak titers occurred at about the same time for primary and secondary immunizations, (c) dosage of antigen influenced differences among populations in antibody response to primary immunization, and (d) both selected lines had similar responses in 2-mercaptoethanol-sensitive and 2-mercaptoethanol-resistant antibodies to primary but not secondary immunization. 相似文献
993.
O F Pahnish J J Urick W C Burns W T Butts M Koger R L Blackwell 《Journal of animal science》1985,61(5):1146-1153
Genotype X environment interactions for postweaning performance traits of bulls produced by different lines of Hereford cattle were investigated in the contrasting environments of Miles City, Montana and Brooksville, Florida. During Phase 1 of the study (1966 to 1973), the performance of bull progeny from two unrelated lines (M1 and F6 previously developed in Montana and Florida, respectively) was compared at each of the two experimental sites. During Phase 2 (1967 to 1974), performance of bulls from two related lines (M1 of Montana origin and F4 derived from an M1 foundation through selection in Florida) was compared at each of the two locations. The line X location interaction effect in Phase 1 was highly significant for weaning weights and average daily gain during the postweaning test, and for end-of-test weight, conformation score, condition score and forecannon circumference. The interaction effect in Phase 2 was highly significant for 205-d and end-of-test weights and significant for all other traits except end-of-test conformation score. These results, consistent with results for traits covered in other papers of the same series (reproductive traits, birth-to-weaning traits of bull and heifer calves combined, and postweaning traits of heifers), indicated the existence of economically important genotype X environment interactions in beef cattle. Results from the series of papers indicated that adaptation to local environment should receive consideration in planning breeding programs, performance tests and interregional transfers of beef cattle. 相似文献
994.
O J Ginther 《Equine veterinary journal》1990,22(3):152-156
Prolonged luteal activity is one of the most formidable terminology challenges in mare reproductive biology. Prolonged luteal activity can be a result of persistence of an individual corpus luteum or the sequential development of luteal glands, each of which may have a normal life span. Luteal tissue can originate from an unovulated follicle or from an ovulation occurring during either follicular or luteal dominance. These complexities, together with ambiguous and inconsistent terminology, have resulted in confusion regarding those conditions which can be grouped broadly under the term prolonged luteal activity. Persistence of an individual corpus luteum can occur in association with severe damage to the endometrium resulting in loss of the uterine luteolytic mechanism. Spontaneous (no known uterine pathology) persistence of the corpus luteum from the follicular-phase ovulation has not been documented adequately as a clinical entity. The occurrence of ovulation towards the end of dioestrus may cause confusion about the origin of prolonged luteal activity. Such immature dioestrous corpora lutea may not respond to the release of uterine luteolysin, thereby leading to prolonged luteal activity even though the original corpus luteum regressed at the normal time. In the absence of critical monitoring of the corpus luteum (eg by ultrasound) the prolonged activity could be attributed erroneously to persistence of the corpus luteum from the follicular-phase ovulation. Pseudopregnancy is another confusing term that is sometimes used to describe persistence of the corpus luteum, especially when the luteal persistence is caused by embryonic loss after the embryo has blocked the uterine luteolytic mechanism.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
995.
996.
O. ANNEVILLE S. SOUISSI J. C. MOLINERO D. GERDEAUX 《Fisheries Management and Ecology》2009,16(6):492-500
Abstract Analysis of long-term catches from the deep peri-alpine Lake Geneva, showed a shift in the stock-recruitment relationship of Coregonus lavaretus (L.), a target species of commercial fishing. This change was mainly related to large-scale meteorological factors. Higher spring water temperatures may have improved larval survival and hence recruitment of whitefish via: (1) a better match between the hatching date of whitefish larvae and development of their zooplankton prey; and (2) the positive temperature effect on larval growth. In Lake Geneva, changes in regulatory mechanisms coupled with stocking and improved water-quality have led to an explosion in the C. lavaretus population in recent years. These results highlight the relevance of long-term changes in the stock-recruitment relationship for management of aquatic ecosystems that are sensitive to climate forcing. 相似文献
997.
Chicks infected with Salmonella typhimurium at 1 day of age were treated with normal intestinal flora starting 3 or 9 days later. Chicks were reared on the floor in isolated pens with wood shavings for litter. Cloacal-swab cultures were the main criteria for determining S. typhimurium infection. A single treatment reduced the infection period, but multiple treatments hastened the process considerably: after 6-8 weeks, birds given multiple treatments yielded sporadic or no isolations of S. typhimurium. It appears that litter from birds colonized by a protective microflora may serve as a vehicle for transmitting the flora to succeeding groups of birds. 相似文献
998.
O A Durojaiye P Kwenkam 《Revue d'élevage et de médecine vétérinaire des pays tropicaux》1990,43(4):439-440
The occurrence of infectious bursal disease (IBD) in industrial poultry flocks in Cameroon was investigated by serological and virological techniques. Antibody to IBD virus was detected in 118 (33.9%) out of 348 serum samples collected in seven randomly selected areas. On the other hand, virological examination was performed on bursa of Fabricius samples obtained post-mortem from flocks in which there was a high mortality among young birds. This virological examination revealed the presence of IBD virus antigen. These observations confirm the occurrence of infectious bursal disease in Cameronian industrial poultry flocks. 相似文献
999.
tests, based on the polymerase chain reaction (
), were developed for the detection of two breed-specific mutations responsible for the autosomal recessive disorder bovine α-mannosidosis. The tests involve separate amplification of two exons of the lysosomal α-mannosidase gene followed by restriction enzyme digestion of the amplicons. We demonstrate that one of the mutations, the 662G→A transition, is responsible for α-mannosidosis in Galloway cattle. The other mutation, the 961T→C transition, is uniquely associated with α-mannosidosis in Angus, Murray Grey and Brangus cattle from Australia. The 961T→C mutation was also detected in Red Angus cattle exported from Canada to Australia as embryos. All 39 animals classified as heterozygotes on the basis of biochemical assays were heterozygous for one of the two mutations. None of 102 animals classified as homozygous-normal on the basis of biochemical assays possessed the mutations. Our results indicate that the two breed-specific mutations may have arisen in Scotland and by the export of animals and germplasm disseminated to America, New Zealand and Australia. 相似文献
1000.
J. T. BLACKFORD dvm MS D. O. GOBLE dvm DiplomateACVS R. W. HENRY dvm PhD D. R. GEISER dvm J. P. HELD DrMedVet 《Veterinary surgery : VS》1985,14(4):287-294
A modified bone-flap technique was used to expose space occupying lesions that involved the conchofrontal sinus, ethmoturbinates, and caudal nasal cavity in five horses. The most common clinical findings were chronic nasal discharge and upper airway obstruction. Surgical intervention was based on endoscopic and radiographic interpretation. The triangulated bone-flap technique increased surgical exposure to the conchofrontal sinus by almost twice the area observed in previously described surgical techniques. The major advantages were that this technique allowed excellent visualization, thorough palpation, and surgical manipulation within the sinus and associated structures. Complications were minimal. One horse was euthanized 1 month postoperatively with recurrence and spread of a mycotic granuloma. The technique extended the usefulness of the other four horses in a 9 to 24 month follow-up period, although the obstructing lesion recurred after 2 years in one of the four horses. 相似文献