全文获取类型
收费全文 | 160805篇 |
免费 | 8138篇 |
国内免费 | 85篇 |
专业分类
林业 | 8782篇 |
农学 | 5540篇 |
基础科学 | 1146篇 |
19320篇 | |
综合类 | 26093篇 |
农作物 | 7410篇 |
水产渔业 | 9037篇 |
畜牧兽医 | 77003篇 |
园艺 | 2672篇 |
植物保护 | 12025篇 |
出版年
2018年 | 4310篇 |
2017年 | 4464篇 |
2016年 | 2968篇 |
2015年 | 1683篇 |
2014年 | 1999篇 |
2013年 | 5411篇 |
2012年 | 4530篇 |
2011年 | 6760篇 |
2010年 | 4901篇 |
2009年 | 4139篇 |
2008年 | 5913篇 |
2007年 | 5930篇 |
2006年 | 4386篇 |
2005年 | 4138篇 |
2004年 | 4043篇 |
2003年 | 4091篇 |
2002年 | 3935篇 |
2001年 | 4695篇 |
2000年 | 4580篇 |
1999年 | 3692篇 |
1998年 | 1465篇 |
1997年 | 1488篇 |
1996年 | 1393篇 |
1995年 | 1748篇 |
1994年 | 1578篇 |
1993年 | 1512篇 |
1992年 | 3154篇 |
1991年 | 3279篇 |
1990年 | 3326篇 |
1989年 | 3324篇 |
1988年 | 3061篇 |
1987年 | 3133篇 |
1986年 | 3224篇 |
1985年 | 3089篇 |
1984年 | 2606篇 |
1983年 | 2312篇 |
1982年 | 1577篇 |
1981年 | 1471篇 |
1980年 | 1427篇 |
1979年 | 2318篇 |
1978年 | 1909篇 |
1977年 | 1626篇 |
1976年 | 1443篇 |
1975年 | 1543篇 |
1974年 | 2075篇 |
1973年 | 2088篇 |
1972年 | 2056篇 |
1971年 | 1816篇 |
1970年 | 1714篇 |
1969年 | 1573篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
951.
I Egerszegi W Hazeleger J Rátky P Sarlós B Kemp E Bouwman L Solti K-P Brüssow 《Reproduction in domestic animals》2007,42(4):441-444
The aim of the study was to compare how different feeding levels affect the ovarian potential of follicular development and oocyte maturation in response to superovulatory treatment in native Mangalica (M, n = 17) compared with Landrace (L, n = 20) pigs. Gilts of both breeds were fed high-energy (HI-2.5 kg) or low-energy (LO - 1.25 kg) feed during oestrus synchronization (15 days of Regumate feeding) till the time of oocyte aspiration (Day 6 after Regumate). Follicular growth was stimulated by the administration of 1000 IU equiue choriou gonadotropiu (eCG) 24 h after Regumate treatment, and ovulation was induced by injection of 750 IU human choriou gonadotropiu (hCG) 80 h after eCG administration. Ultrasound (US) investigation was done three times (4-10 h before, and 40-44 and 72-74 h after eCG administration) for the observation of follicular development. Oocyte and follicular fluid (FF) were collected endoscopically 34 h after hCG injection. Cumulus-oocyte complexes were evaluated, their morphology determined, and thereafter fixed and stained for chromatin evaluation. Oocytes were classified as meiosis-resumed (germinal vesicle breakdown, diakinesis, metaphase I to anaphase I) or matured (telophase I and metaphase II). FF concentrations of oestradiol and progesterone were measured by validated radioimmunoassays. In L gilts, differences were observed between HI and LO in the number of preovulatory follicles (32.3 +/- 10.5 vs 17.1 +/- 12.3, p < 0.05), but not in M (25.3 +/- 2.9 vs 28.8 +/- 7.3, p > 0.05). Initial follicular growth was not affected by feeding levels; however, preovulatory follicle size was larger in M (7.1 +/- 0.9 and 6.9 +/- 1.1 mm vs 5.7 +/- 0.7 and 5.5 +/- 0.8 mm; p < 0.05). No differences were obtained with relation to mature chromatin configuration in both breeds (L gilts: HI - 70% and LO-67% vs M gilts: HI - 67% and LO - 63%). A twofold higher oestradiol concentration was detected in FF of HI-M and LO-M (29.6 +/- 6.8 and 30.9 +/- 10.3 ng/ml respectively) compared with that of L (16.9 +/- 9.7 and 17.9 +/- 3.6 ng/ml, respectively; p < 0.05). The mean FF progesterone level was nearly fivefold higher in M (2020.4 +/- 1056 and 1512.2 +/- 1121.8 ng/ml) compared with L (386.2 +/- 113.7 and 298.8 +/- 125.9 ng/ml, p < 0.05). The results indicate an influence of the feeding of altered energy on the number of recruitable preovulatory follicles in modern Landrace but not in native Mangalica breed. Moreover, the follicular steroid hormone milieu differs between Landrace and Mangalica gilts but not depending on feeding levels. Oocyte maturation was not affected by diet. 相似文献
952.
The innate immune system is essential for host defence and is responsible for early detection of potentially pathogenic microorganisms. Upon recognition of microbes by innate immune cells, such as macrophages and dendritic cells, diverse signalling pathways are activated that combine to define inflammatory responses that direct sterilisation of the threat and/or orchestrate development of the adaptive immune response. Innate immune signalling must be carefully controlled and regulation comes in part from interactions between activating and inhibiting signalling receptors. In recent years, an increasing number of pattern recognition receptors (PRRs), including C-type lectin receptors and Toll-like receptors (TLRs), has been described that participate in innate recognition of microbes, especially through the so called pathogen-associated molecular patterns (PAMPs). Recent studies demonstrate strong interactions between signalling through these receptors. Whereas useful models to study these receptors in great detail in the murine and human system are now emerging, relatively little is known regarding these receptors in companion and farm animals. In this review, current knowledge regarding these receptors in species of veterinary relevance is summarised. 相似文献
953.
Detailed behavioural observations were made of broiler breeder chicks after their beaks had been trimmed by an automated infrared treatment at one day of age or by the traditional hot-blade method at one day or seven days, or after they had been sham-trimmed or left untreated. Observations took place immediately after the treatments and at regular intervals until six weeks of age; beak length and bodyweight were also measured regularly. There were no significant effects on the behaviour of the chicks in the first hour after trimming or in the subsequent six weeks. Variability in beak length was low within the treatments and there was significant regrowth, but it was least in the birds that had been hot-blade trimmed at seven days. Both beak-trimming methods were associated with small but significant reductions in bodyweight, with the hot-blade-treated birds being more affected. 相似文献
954.
Simpson BS Landsberg GM Reisner IR Ciribassi JJ Horwitz D Houpt KA Kroll TL Luescher A Moffat KS Douglass G Robertson-Plouch C Veenhuizen MF Zimmerman A Clark TP 《Veterinary therapeutics : research in applied veterinary medicine》2007,8(1):18-31
Canine separation anxiety is a common behavioral problem presented to veterinarians. Associated behaviors are distressing to both dog and owner, have the potential to disrupt the human-companion animal bond, and may lead to euthanasia. The results of this study demonstrate the clinical efficacy and safety of Reconcile (fluoxetine, 1 to 2 mg/kg/day [0.45 to 0.91 mg/lb/day]), in conjunction with behavior management, for the treatment of canine separation anxiety. The beef flavored chewable formulation was palatable to treated dogs and easy to administer. This study provides to veterinarians and owners valuable information about an effective separation anxiety treatment plan that combines use of Reconcile with behavior modification. 相似文献
955.
Hayes AM Gregory SP Murphy S McConnell JF Patterson-Kane JC 《The Journal of small animal practice》2007,48(5):288-291
An 11-year-old, female, spayed cocker spaniel was presented with dysphonia caused by a solitary laryngeal mass. Excisional biopsy was performed, and a diagnosis of plasmacytoma was made on the basis of histological examination. Further investigations showed no signs of systemic involvement. Coarse fractionated radiation therapy failed to control the tumour. Therapy was successfully instituted with a conventional combination chemotherapy protocol over a period of 14 months. The dog remains disease free 30 months after diagnosis. Most solitary, extramedullary plasmacytomas in dogs arise in the gastrointestinal tract, with fewer reports in other sites. The larynx is an uncommon sight of involvement in any species, and to the authors' knowledge, this is the first report of this tumour type in the canine larynx. In contrast to the therapeutic benefits reported in humans, the combination of surgery and radiation therapy was unsuccessful in this case, although sustained remission was gained following chemotherapy. 相似文献
956.
957.
J. Verner P. Humpolíek & A. Knoll 《Zeitschrift für Tierzüchtung und Züchtungsbiologie》2007,124(2):81-85
Summary Porcine myogenic differentiation genes ( MYOD ) family play a key role in growth and muscle development and are therefore considered as candidate genes for meat production traits. The objective of the study was to investigate the polymorphisms at four loci belonging to the MYOD genes family and analyse their associations with variation in meat production traits in Czech pig breeds. To verify the associations between the polymorphisms and the selected meat traits, altogether 254 pigs, including full- and half-sibs, of Large White and Landrace breeds were tested. The studied meat characteristics were weight of neck, loin, shoulder and ham, lean meat content (LMC), backfat thickness, intramuscular fat (IMF), remission, dry matter content and test daily gain. Statistically significant associations were observed between MYOG gene and fat and neck weight, and between MYF5 gene and IMF and LMC. High significant differences were observed between genotypes AA and AB of MYOD1 in IMF and between genotypes AB and BB of MYF5 in loin weight. 相似文献
958.
Jahnke A Hirschberger J Fischer C Brill T Köstlin R Plank C Küchenhoff H Krieger S Kamenica K Schillinger U 《Journal of veterinary medicine. A, Physiology, pathology, clinical medicine》2007,54(10):599-606
Despite aggressive pre- or postoperative treatment, feline fibrosarcomas have a high relapse rate. In this study, a new treatment option based on immune stimulation by intra-tumoral delivery of three feline cytokine genes was performed. The objective of this phase-I dose-escalation study was to determine a safe dose for further evaluation in a subsequent phase-II trial. Twenty-five client-owned cats with clinical diagnosis of fibrosarcoma - primary tumours as well as recurrences - entered the study. Four increasing doses of plasmids coding for feIL-2, feIFN-gamma or feGM-CSF, respectively, were previously defined. In groups I, II, III and IV these doses were 15, 50, 150 and 450 microg per plasmid and a corresponding amount of magnetic nanoparticles. Two preoperative intra-tumoral injections of the magnetic DNA solution were followed by magnetofection. A group of four control cats received only surgical treatment. Side effects were registered and graded according to the VCOG-CTCAE scale and correlated to treatment. Statistical analyses included one-way anova, post hoc and Kruskal-Wallis tests. ELISA tests detecting plasma feIFN-gamma and plasma feGM-CSF were performed. One cat out of group IV (450 microg per plasmid) showed adverse events probably related to gene delivery. As these side effects were self-limiting and occurred only in one of eight cats in group IV, this dose was determined to be well tolerable. Altogether six cats developed local recurrences during a 1-year observation period. Four of these cats had been treated with dose IV. Regarding these observations, a subsequent phase-II trial including a representative amount of cats should be tested for the efficacy of dose IV as well as dose III. 相似文献
959.
Snow LC Newson SE Musgrove AJ Cranswick PA Crick HQ Wilesmith JW 《The Veterinary record》2007,161(23):775-781
Recent outbreaks of the H5N1 strain of avian influenza in Europe have highlighted the need for continuous surveillance and early detection to reduce the likelihood of a major outbreak in the commercial poultry industry. In Great Britain (gb), one possible route by which H5N1 could be introduced into domestic poultry is through migratory wild birds from Europe and Asia. Extensive monitoring data on the 24 wild bird species considered most likely to introduce the virus into GB, and analyses of local poultry populations, were used to develop a risk profile to identify the areas where H5N1 is most likely to enter and spread to commercial poultry. The results indicate that surveillance would be best focused on areas of Norfolk, Suffolk, Lancashire, Lincolnshire, south-west England and the Welsh borders, with areas of lower priority in Anglesey, south-west Wales, north-east Aberdeenshire and the Firth of Forth area of Scotland. These areas have significant poultry populations including a large number of free-range flocks, and a high abundance of the 24 wild bird species. 相似文献
960.
Hyperlipidaemia refers to an increased concentration of lipids in the blood. Hyperlipidaemia is common in dogs and has recently emerged as an important clinical condition that requires a systematic diagnostic approach and appropriate treatment. Hyperlipidaemia can be either primary or secondary to other diseases. Secondary hyperlipidaemia is the most common form in dogs, and it can be a result of endocrine disorders, pancreatitis, cholestasis, protein‐losing nephropathy, obesity, as well as other conditions and the use of certain drugs. Primary hyperlipidaemia is less common in the general canine population but it can be very common within certain breeds. Hypertriglyceridaemia of Miniature Schnauzers is the most common form of primary hyperlipidaemia in dogs but other breeds are also affected. Possible complications of hyperlipidaemia in dogs include pancreatitis, liver disease, atherosclerosis, ocular disease and seizures. Management of primary hyperlipidaemia in dogs is achieved by administration of ultra low‐fat diets with or without the administration of lipid lowering drugs such as omega‐3 fatty acids, fibrates, niacin and statins. 相似文献