全文获取类型
收费全文 | 108831篇 |
免费 | 6338篇 |
国内免费 | 52篇 |
专业分类
林业 | 3851篇 |
农学 | 3400篇 |
基础科学 | 660篇 |
13490篇 | |
综合类 | 19165篇 |
农作物 | 4498篇 |
水产渔业 | 5559篇 |
畜牧兽医 | 56291篇 |
园艺 | 1325篇 |
植物保护 | 6982篇 |
出版年
2019年 | 1032篇 |
2018年 | 1598篇 |
2017年 | 1855篇 |
2016年 | 1720篇 |
2015年 | 1444篇 |
2014年 | 1782篇 |
2013年 | 4349篇 |
2012年 | 3271篇 |
2011年 | 3888篇 |
2010年 | 2594篇 |
2009年 | 2534篇 |
2008年 | 3791篇 |
2007年 | 3631篇 |
2006年 | 3385篇 |
2005年 | 3157篇 |
2004年 | 2935篇 |
2003年 | 3034篇 |
2002年 | 2811篇 |
2001年 | 3543篇 |
2000年 | 3428篇 |
1999年 | 2772篇 |
1998年 | 1188篇 |
1997年 | 1139篇 |
1996年 | 993篇 |
1995年 | 1168篇 |
1994年 | 1037篇 |
1993年 | 1063篇 |
1992年 | 2149篇 |
1991年 | 2232篇 |
1990年 | 2107篇 |
1989年 | 2150篇 |
1988年 | 1881篇 |
1987年 | 2000篇 |
1986年 | 2027篇 |
1985年 | 1990篇 |
1984年 | 1601篇 |
1983年 | 1421篇 |
1982年 | 1054篇 |
1979年 | 1435篇 |
1978年 | 1153篇 |
1977年 | 1035篇 |
1976年 | 1012篇 |
1975年 | 1090篇 |
1974年 | 1287篇 |
1973年 | 1310篇 |
1972年 | 1250篇 |
1971年 | 1156篇 |
1970年 | 1078篇 |
1969年 | 1070篇 |
1967年 | 981篇 |
排序方式: 共有10000条查询结果,搜索用时 328 毫秒
131.
Canine distal renal tubular acidosis and urolithiasis 总被引:1,自引:0,他引:1
D J Polzin C A Osborne F W Bell 《Veterinary Clinics of North America: Small Animal Practice》1986,16(2):241-250
Distal RTA is characterized by decreased distal renal tubular hydrogen ion secretion, decreased ability to acidify urine, hypercalciuria, hyperphosphaturia, hypocitraturia, and metabolic acidosis. Because of the resulting alterations in urine composition and pH, patients with distal RTA are predisposed to urolithiasis and renal calcification. Diagnosis of distal RTA is important because it is a potentially reversible disorder that, left untreated, may cause nephrocalcinosis, recurrent urolith formation, moderate to severe metabolic acidosis, and renal failure. 相似文献
132.
ANTHONY W. P. BASHER BVetMed mrcvs MARY C. WALTER dvm CHARLES D. NEWTON dvm ms Diplomateacvs 《Veterinary surgery : VS》1986,15(5):356-362
The medical records from 95 cases of coxofemoral luxation in dogs and cats were reviewed. Unilateral craniodorsal luxation was most common, (78.1% of dogs, 72.7% of cats). Trauma from being struck by an automobile was the most frequent cause (59.0%). Treatment was closed (manual) or open (surgical) reduction. The failure rate following single closed reduction was 64.8%. The surgical reduction procedure included capsular repair (capsulorrhaphy) via a craniolateral approach to the hip or via trochanteric osteotomy or gluteal tenotomy. The success rate following reduction via the craniolateral approach was 82%; no failure was recorded with trochanteric transposition, but reluxa-tion followed the single gluteal tenotomy. The Ehmer sling was the most common external fixation and was kept in place an average of 12.5 days. Thirty-three animals were available for follow-up, and no difference was recorded in limb function between the two groups of animals treated by closed vs surgical reduction. Patients with degenerative joint disease at the time of luxation were less likely to be successfully reduced; 64.3% of these animals were eventually treated by femoral head and neck excision. Thirty-eight patients had associated major injuries. Long-term follow-up results were better in those patients with concomitant orthopedic injuries than in those without other injuries. 相似文献
133.
C. McL. Press 《Anatomia, histologia, embryologia》2005,34(S1):40-41
Paratuberculosis is a chronic granulomatous enteritis and lymphadenitis in ruminants caused by Mycobacterium avium subsp. paratuberuclosis . To investigate the efficacy of assays for early diagnosis, experimental infections were performed in goat kids. Oral doses of M. a. paratuberculosis were administered to goat kids over extended periods and the resulting infection was followed for 12–24 months. Complementary experiments were performed on goat kids vaccinated against M. a. paratuberculosis . Immunological, pathological and morphological examinations were undertaken in both these experimental systems. The analysis of results from these experiment series provided novel insights into the influence of the biology of gut-associated lymphoid tissue on the progress of disease, into the character of the tissue granuloma and its dominance of the local tissue response and into the relationship between the local and systemic immune responses. 相似文献
134.
Spealman CR 《Science (New York, N.Y.)》1941,93(2408):187-188
The rate of the frog or guinea pig heart preparation was not significantly influenced by the H-ion concentration when this was kept within limits which allowed the heart to continue beating. The theory that the H-ion concentration is intimately concerned with the origination of the heart beat is not supported by the results of this investigation. 相似文献
135.
136.
137.
The 1998 Report of the American Association of Feline Practitioners and Academy of Feline Medicine Advisory Panel on Feline Vaccines was developed to help veterinary practitioners formulate vaccination protocols for cats. The current panel report updates information, addresses questions, and speaks to concerns raised by the 1998 report. In addition it reviews vaccine licensing, labeling, and liability issues and suggests ways to successfully incorporate vaccination protocol changes into a private practice setting. 相似文献
138.
A.J.A. Vinten D.R. Lewis D.R. Fenlon K.A. Leach R. Howard I. Svoboda I. Ogden 《Soil Use and Management》2002,18(3):223-231
Abstract. Slurry from farm animals may contaminate water supplies, rivers and bathing waters with faecal coliforms, such as Escherichia coli . Where animals harbour the O157 strain the hazard to human health is particularly high, but both the hazard level, and the low incidence and sporadic nature of the excretion of E. coli O157 make it difficult to study this strain under field conditions. The survival of total E. coli and of E. coli O157 were compared in the laboratory for two soils under controlled temperature and moisture. E. coli O157 die-off rate was the same as or quicker than for total E. coli . This result meant that field experiments studying the fate of total E. coli should give a satisfactory evaluation of the risk of water contamination by the O157 strain. In four field experiments at three sites, slurry containing total E. coli numbers of 2.2 × 104 to 5.7 × 105 colony forming units per mL (c.f.u. mL–1 ) was applied to drained field plots. Field die-off was faster than expected from laboratory experiments, especially in one experiment where two weeks dry weather followed application. In all but this experiment, the first drain flow events after slurry application led to very high E. coli concentrations in the drains (103 to 104 c.f.u. mL–1 ). E. coli O157 was present in the slurry used for two of the experiments (33 c.f.u. per 100 mL in each case). However the proportion of E.coli O157 was very low (about 1 in 105 ) and it was not detected in the drainage water. After the first week E. coli drainage water numbers decreased rapidly but they were 1–10 c.f.u. mL–1 for much of the sampling period after slurry application (1–3 months). 相似文献
139.
140.
The data obtained in the workshop provide further evidence that CH128A and IL-A26 and the 12 new mAbs that form a cluster recognise the bovine orthologue of CD2. The mAbs inhibit rosetting with SRBC, stain cells in primary and secondary lymphoid organs in patterns consistent with those obtained in humans with anti-CD2 mAbs, and the 11 IgG mAbs all immunoprecipitate a peptide with a Mr of 58-62 kDa. It is not clear from the studies whether the epitopes defined by the mAbs correspond with the region I and II epitopes present on CD2. None of the data suggest that any of the mAbs recognise the region III (CDD2R) epitope (Peterson and Seed, 1987; Knapp et al., 1989). Further studies are now needed to define the physical and functional relation of the epitopes and establish whether antibody-mediated activation corresponds with that noted in humans. Data reported in one study (Baldwin et al., 1988) with IL-A26 suggest possible differences in the requirements for activation. In addition, further studies are needed to demonstrate how many cell types express BoCD2. In mice, evidence has been presented which shows the mouse orthologue is expressed on some B cells (Yagitta et al., 1989). Studies in cattle have clearly shown CD2 is present on the majority of CD4+ and CD8+ T-cells and a small population of CD4-/CD8- cells (Baldwin et al., 1988; Davis, unpublished observations). Evidence presented in this workshop has shown that some CD2+ cells express a WC2 molecule (Sopp et al., 1991).(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献