全文获取类型
收费全文 | 122008篇 |
免费 | 6753篇 |
国内免费 | 68篇 |
专业分类
林业 | 5892篇 |
农学 | 4272篇 |
基础科学 | 752篇 |
14998篇 | |
综合类 | 17551篇 |
农作物 | 4577篇 |
水产渔业 | 6191篇 |
畜牧兽医 | 65453篇 |
园艺 | 1455篇 |
植物保护 | 7688篇 |
出版年
2018年 | 1767篇 |
2017年 | 1928篇 |
2016年 | 1834篇 |
2015年 | 1563篇 |
2014年 | 1897篇 |
2013年 | 4679篇 |
2012年 | 3424篇 |
2011年 | 4043篇 |
2010年 | 2709篇 |
2009年 | 2714篇 |
2008年 | 3970篇 |
2007年 | 3891篇 |
2006年 | 3615篇 |
2005年 | 3414篇 |
2004年 | 3237篇 |
2003年 | 3363篇 |
2002年 | 3067篇 |
2001年 | 4110篇 |
2000年 | 3963篇 |
1999年 | 3153篇 |
1998年 | 1293篇 |
1997年 | 1300篇 |
1996年 | 1203篇 |
1995年 | 1406篇 |
1994年 | 1217篇 |
1993年 | 1189篇 |
1992年 | 2523篇 |
1991年 | 2778篇 |
1990年 | 2795篇 |
1989年 | 2685篇 |
1988年 | 2491篇 |
1987年 | 2467篇 |
1986年 | 2502篇 |
1985年 | 2358篇 |
1984年 | 2037篇 |
1983年 | 1671篇 |
1982年 | 1176篇 |
1979年 | 1825篇 |
1978年 | 1416篇 |
1977年 | 1229篇 |
1976年 | 1228篇 |
1975年 | 1259篇 |
1974年 | 1562篇 |
1973年 | 1581篇 |
1972年 | 1549篇 |
1971年 | 1462篇 |
1970年 | 1422篇 |
1969年 | 1347篇 |
1968年 | 1148篇 |
1967年 | 1250篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
OBJECTIVE: To compare radioulnar incongruence (RUI) of normal canine elbows and elbows with arthroscopically confirmed medial compartment disease in vivo using systematic computed tomography (CT) measurements. STUDY DESIGN: Prospective comparison of RUI measurements in normal and dysplastic canine elbows. SAMPLE POPULATION: Right elbows of 25 medium-large breed, adult dogs with medial compartment disease and 9 medium-large breed, adult dogs with no elbow disease. METHODS: Transverse CT images of proximal radioulnar articulation were reformatted to dorsal and sagittal planes. RUI in 3 locations of the forelimb's medial coronoid was measured. Arthroscopy confirmed diagnosis of medial compartment disease in the diseased group. RUI measurements of the diseased and normal elbows were compared. RESULTS: Cumulative statistical analysis of RUI in all planes revealed no significant difference between the normal and abnormal elbows (P = .61). The abnormal elbows had negative mean RUI at the mid (P = .56) and cranial (P = .24) coronoid regions that were not significantly different from normal elbows and mean positive RUI at the base coronoid that was significantly greater than in normal elbows (P = .00082). CONCLUSION: Canine elbows with established medial compartment disease do not have significant RUI at the medial coronoid region at the time of diagnosis when compared with normal elbows. CLINICAL RELEVANCE: If RUI is a significant factor in the pathophysiology of medial compartment elbow disease in the dog, it does not appear to be present at the time of diagnosis of disease. Ulnar or radial osteotomies do not appear to be indicated for restoration of normal radioulnar articular surface alignment. 相似文献
992.
Seeling K Lebzien P Dänicke S Spilke J Südekum KH Flachowsky G 《Journal of animal physiology and animal nutrition》2006,90(3-4):103-115
The aims of this study were to examine the effects of and possible interactions between dry matter (DM) intake and feeding Fusarium toxin-contaminated wheat on ruminal fermentation, serum chemical parameters and milk yield of dairy cows. Fourteen dairy cows equipped with ruminal and duodenal cannulas were analysed. All animals were fed the same ration, the daily feed amounts being adjusted to current performance. On DM basis, the ration consisted of 60% concentrate including 55% wheat [Fusarium-contaminated wheat (mycotoxin period) or control wheat (control period)] and was completed with 40% maize and grass silage. Each cow was fed the contaminated wheat [deoxynivalenol (DON), 8.21 mg/kg DM and zearalenone (ZON), 0.09 mg/kg DM] and the control wheat (0.25 mg DON/kg DM and 51 microg ZON/kg DM). As expected, a higher organic matter (OM) intake decreased the amounts of fermented crude nutrients related to the respective intakes. An increased amount of crude protein degraded (p < 0.05) and a lower molar percentage of propionate in the rumen fluid were observed when feeding the Fusarium toxin-contaminated wheat at increased OM intakes in comparison with the control wheat. The activities of serum aspartate aminotransferase (ASAT; p < 0.001), glutamate dehydrogenase (GLDH; p < 0.01) and gamma glutamyl transferase (gamma-GT; p < 0.01) increased with increasing OM intake and were not related to the mycotoxin contamination of the wheat. 相似文献
993.
Employing a purified lgG fraction of a polyclonal anti-AT1 receptor anti-body, raised against a synthetic octapeptide encompassing residues 14-21 of the first extracellular domain of the AT1 polypeptide, selective AT1 receptor expression was immunohistochemically demonstrable within renal structures in Sprague-Dawley (SD) rats and the desert rodent Meriones crassus. In both animal models, prominent AT1 receptor labelling was evident in renal vascular elements, particularly cortical inter-lobular arteries (IA) as well as vasa recta bundles in the inner stripe of the outer medulla. Less intense labelling was observed among peritubular capillary endothelia within the deep cortex, and at both the outer stripe and the inter-bundle regions of the inner stripe of the outer medulla. The binding of the anti-peptide anti-body was, however, lacking among glomeruli and, except for the intense labelling confined to basement membranes of Bowman's capsule of deep nephrons, was virtually absent in all renal tubular structures of both animal models. Structural assessment of the expressed AT1 receptors by two-dimensional Western blotting revealed that a spectrum of structurally distinct AT1 receptor isoforms is expressed in the renal tissues of both animal models. This spectrum was constituted by isoforms of equal size (70 kDa) but distinct pls in SD rats, and of both different sizes (67-73 kDa) and isoelectric points in M. crassus. In either species, the charge and/or size heterogeneity of AT1 receptor isoforms may be attributed in part to differential post-translational glycosylation mechanisms of the AT1 receptor polypeptide backbone. The potential for the differential glycosylation state of AT1 receptors to alter recognition properties may add another level of complexity to tissue-specific and/or species-specific mechanisms underlying angiotensin II interactions in the kidney. 相似文献
994.
Liste G María GA Buil T García-Belenguer S Chacón G Olleta JL Sañudo C Villarroel M 《DTW. Deutsche tier?rztliche Wochenschrift》2006,113(2):59-64
The transport of domestic animals by road can increase levels of stress and decrease meat quality, especially in unfavourable climates. The purpose of this study was to investigate the effect of journey duration and vertical position on the transport truck on some physiological indicators of stress and on instrumental meat quality parameters in commercial rabbits. In the summer months (June and July, 2003), 78 rabbits were subjected to either long (7 h) (LJ) or short (1 h) (SJ) journeys (3 replicates each, n = 6) between the farm and an abattoir in northern Spain. The position (top, middle, or bottom) occupied by the rabbits on the Multi-Floor cage Rolling Stand (MFRS) of the transport truck was recorded. Blood samples were collected at sticking and meat pH was measured at 24 h post-mortem (pH24). At 48 h post-mortem, samples of the M. longissimus dorsi were used to determine water-holding capacity (WHC) and instrumental tenderness using an INSTRON machine. The levels of corticosterone, glucose, lactate, and creatine kinase were slightly higher in LJ than in SJ samples, but the difference was not statistically significant (p < or = 0.10). Independent of journey length, rabbits in the middle and bottom of the MFRS showed higher levels (p < or = 0.05) of glucose and creatine kinase (middle), and corticosterone (bottom) than the rabbits located at the top floor. The pH 24 and WHC values of the SJ and LJ rabbits did not differ significantly. Journey length had a significant effect (p < or = 0.01) on meat tenderness. The meat from rabbits subjected to LJ had higher values of maximum stress and total toughness than did the SJ rabbits (p < or = 0.05). There were similar differences (p < or = 0.05) between LJ and SJ rabbits in their stress values of compression at 20% and 40% (measures of the tenderness of raw meat). In hot weather, the position on the transport truck appeared to have a greater effect on rabbit welfare than the duration of the journey. 相似文献
995.
Duscher G Pleydell D Prosl H Joachim A 《Journal of veterinary medicine. B, Infectious diseases and veterinary public health》2006,53(3):138-144
The prevalence rates of Echinococcus multilocularis in foxes (n=5600) evaluated in several Austrian surveys conducted between 1991 and 2004 were analysed for spatial and temporal differences. Data from early studies (1993-1997) in which the intestinal scraping technique (IST) was utilized were compared with data from recent (1999-2004) investigations, which made use of the shaking in a vessel technique (SVT), and it was assessed whether or not the infection rates of Austrian foxes had increased between the investigated intervals. In total, data from 85 districts are presented and both the retrospective and recent data are available from 39 of these districts. A Bayesian hierarchical model of parasite prevalences is presented which (i) accounts for differences in the sensitivity of IST and SVT, (ii) incorporates spatial auto-correlation between neighbouring districts, (iii) investigates the possibility of a temporal shift in the infection status of foxes, and (iv) quantifies uncertainty at each level of the model. The national average prevalence rates in the mid-1990s and at the turn of the millennium were 2.4% (95% confidence intervals 1.1-4.8) and 3.9% (95% confidence intervals 1.5-8.4) respectively. Above average prevalence rates were observed in the western and the northern parts of the country. Evidence is also presented for a temporal augmentation of the prevalence rates in some districts in the northern and eastern parts of the country. These findings are in concordance with several investigations in other European states where both newly emerged areas and elevated levels of transmission in existing endemic areas have been found. None of the districts investigated here showed significant evidence of a drop in prevalence. 相似文献
996.
Teankum K Pospischil A Janett F Bürgi E Brugnera E Hoelzle K Polkinghorne A Weilenmann R Zimmermann DR Borel N 《Veterinary microbiology》2006,116(1-3):149-157
Chlamydiae cause abortion and reproductive disorders in sows. Although organisms can infect the male genital tract, little is known about the disease situation in boars. Hence, we examined the prevalence of chlamydial infection in semen and genital tracts of boars. Samples collected from Swiss boars (group A: n=42), and boars from Germany (group B: n=39) were examined by bacteriology, LPS-ELISA, immunohistochemistry (IHC) and polymerase chain reaction (PCR). The latter methodology involved use of three PCR assays including 16Sig rDNA, IGS-S (intergenic spacer 16S/23S-Short) and IGS-L (intergenic spacer 16S/23S-Long) PCR for comparison methods. PCR sensitivity and the presence of potential PCR inhibitors were determined by spiking semen with Chlamydophila (Cp.) abortus DNA. Detection limits of the 16Sig and IGS-S PCR were 10 templates, while the IGS-L PCR was less sensitive (100 templates). Of 25 semen samples that were collected from group A, one semen sample was positive for Cp. psittaci and two were positive for Chlamydia-like organisms by 16Sig PCR. Screening of sera from Swiss boars revealed three animals with positive reactions in the LPS-ELISA, although we failed to detect chlamydiae within organs of these or sera-negative animals by IHC or IGS-S PCR. In group B, 10 ejaculates were positive for Chlamydia (C.) suis and two were positive for Chlamydia-like organisms by 16S PCR. The identification of DNA from Chlamydia-like organisms in semen from both groups of boars was surprising and a role for these bacteria in reproductive diseases requires further assessment. In conclusion, the prevalence of chlamydial infection was low in group A animals indicating that venereal transmission may not be significant for Chlamydia-associated reproductive diseases in pigs, although rare cases may occur. 相似文献
997.
1. In this study we investigated the residues of fluoroquinolone drugs (ciprofloxacin and pefloxacin) in the cloacal gland (a site of foam synthesis) and other tissues such as breast muscle, testes, brain, kidney and plasma. 2. Fifty-four healthy male Japanese quail were selected at random from a flock, maintained under uniform husbandry conditions and divided into three groups, each of 18 birds. Group I (control) received 1 ml vehicle (normal saline 0.9% (w/v) NaCl) daily for 12 d through the intraperitoneal route. Birds of groups II and III received ciprofloxacin and pefloxacin by the same route at the rate of 10 and 12 mg/kg body weight, respectively, every day for a similar period. 3. Birds from each group were killed, at 1, 5 and 10 d after the cessation of treatment, to collect the cloacal gland together with other tissues that were analysed for residual drugs. 4. Cloacal gland retained the maximum drug residues of ciprofloxacin (60%) and pefloxacin (80%) on d 10 compared with that on d 1 after drug withdrawal. The drug residues were found 60 and 80% in ciprofloxacin and pefloxacin groups, respectively, in the cloacal gland tissue even on d 10 after withdrawal of the treatment. 5. In the ciprofloxacin-treated group, all tissues except cloacal gland contained very small amounts of the drug residues on d 10 after treatment ended. In the pefloxacin group the cloacal gland, breast muscle and kidney retained a fairly high amount of drug even on d 10 after treatment ceased. No residues of pefloxacin were detectable in testes and brain throughout. 6. In conclusion, the cloacal gland in Japanese quail acted as the largest sink for the fluoroquinolone drugs. Ciprofloxacin was more widely distributed in different tissues and persisted for a shorter period than pefloxacin. 相似文献
998.
The objective of this study was to determine the effects of castration on short-term growth performance, hormone profiles, and behavior in pigs at 3, 6, 9, or 12 d of age. Ninety intact male pigs were assigned randomly to a treatment age by litter [3, 6, 9, or 12 d of age; n = 9 to 13 pigs per treatment (age) group]. Pigs within a single litter were then assigned to noncastrated (NC) or castrated (CAS) treatment groups according to BW. Pigs were nonsurgically fitted with jugular catheters, and blood samples were drawn immediately before castration (0 h) and at 0.5, 1, 1.5, 2, 24, and 48 h after castration. Body weights were obtained when pigs were catheterized and again at 24 and 48 h after castration. Serum samples were analyzed for cortisol, porcine corticosteroid-binding globulin, and dehydroepiandrosterone sulfate (DHEA-S). No differences were detected in initial BW of pigs, and there was no overall treatment effect on growth performance of pigs at 24 or 48 h posttreatment. A time x treatment interaction was detected (P < 0.01) for serum cortisol concentrations, such that cortisol was greater in CAS pigs than in NC pigs. No overall effect of age at castration was observed on cortisol concentrations. At 24 h after castration, serum cortisol concentrations returned to baseline in all treatment groups; however, at 48 h after castration, overall cortisol concentrations were elevated (P < 0.01) in the 6-, 9-, and 12-d-old pigs in both the CAS and NC groups compared with baseline concentrations. Total cortisol and porcine corticosteroid-binding globulin were used to calculate the free cortisol index (FCI). A time x treatment interaction was observed (P < 0.01) for FCI, such that FCI was greater in CAS males than in NC males. The FCI was also affected by age (P < 0.01). There was a time x treatment x age interaction (P < 0.01) for serum DHEA-S, such that DHEA-S concentrations decreased in CAS animals but increased in NC animals, and DHEA-S concentrations increased with age. During the first 2 h after castration, there was an overall age effect (P = 0.01) on the time that pigs spent standing, such that 3-d-old pigs stood more than 6-, 9-, or 12-d-old pigs. Treatment did not influence the time that pigs spent nursing, lying, standing, or sitting, although there was a trend (P = 0.08) for CAS pigs to be less active than NC pigs. These data indicate that castration is stressful regardless of age; however, the stress associated with handling seems to increase as pigs age. 相似文献
999.
1000.
Kristensen HH Perry GC Prescott NB Ladewig J Ersbøll AK Wathes CM 《British poultry science》2006,47(3):257-263
1. The effects of light source and intensity on leg health and performance of female ROSS 308 broiler chickens were investigated in a 2 x 2 experimental design (8 groups of 275 chicks) of two light sources (Osram biolux and Osram warm-white) and two light intensities (5 and 100 clux, adjusted to fowl-perceived illuminance). 2. At 41 d of age, body weight, gait-score, footpad dermatitis and hock-burn were measured on 50 birds from each light environment. In addition, weekly feed intake and body weight were determined on a group basis and mortality was recorded continuously. 3. The light environment did not affect the severity of the gait-score or hock-burns. The risk of moderate to severe lameness and hock-burns increased with body weight. Birds weighing more than 2400 g had an increased probability of moderate footpad lesions in biolux light. 4. Weight and gait-score, as well as gait-score and hock-burn were positively correlated. Podo-dermatitis was weakly correlated with hock-burn, which contradicts earlier findings. The light environment did not affect feed intake, body weight or mortality. 5. The light sources and intensities employed in this study did not adversely affect production or leg health of broiler chickens reared semi-commercially. 相似文献