全文获取类型
收费全文 | 4539篇 |
免费 | 310篇 |
国内免费 | 2篇 |
专业分类
林业 | 303篇 |
农学 | 128篇 |
基础科学 | 36篇 |
819篇 | |
综合类 | 851篇 |
农作物 | 195篇 |
水产渔业 | 233篇 |
畜牧兽医 | 1842篇 |
园艺 | 109篇 |
植物保护 | 335篇 |
出版年
2023年 | 31篇 |
2022年 | 34篇 |
2021年 | 67篇 |
2020年 | 77篇 |
2019年 | 82篇 |
2018年 | 96篇 |
2017年 | 89篇 |
2016年 | 110篇 |
2015年 | 79篇 |
2014年 | 120篇 |
2013年 | 197篇 |
2012年 | 229篇 |
2011年 | 284篇 |
2010年 | 178篇 |
2009年 | 149篇 |
2008年 | 254篇 |
2007年 | 244篇 |
2006年 | 258篇 |
2005年 | 239篇 |
2004年 | 189篇 |
2003年 | 221篇 |
2002年 | 181篇 |
2001年 | 75篇 |
2000年 | 81篇 |
1999年 | 84篇 |
1998年 | 45篇 |
1997年 | 39篇 |
1996年 | 40篇 |
1995年 | 34篇 |
1994年 | 29篇 |
1993年 | 32篇 |
1992年 | 39篇 |
1991年 | 54篇 |
1990年 | 49篇 |
1989年 | 47篇 |
1988年 | 33篇 |
1987年 | 60篇 |
1986年 | 40篇 |
1985年 | 58篇 |
1984年 | 38篇 |
1983年 | 46篇 |
1982年 | 25篇 |
1981年 | 22篇 |
1980年 | 24篇 |
1979年 | 34篇 |
1978年 | 25篇 |
1976年 | 26篇 |
1973年 | 27篇 |
1970年 | 24篇 |
1969年 | 31篇 |
排序方式: 共有4851条查询结果,搜索用时 15 毫秒
971.
R. D. Almada C. Sandoval K. E. Keller R. R. Martin P. D. S. Caligari 《Plant pathology》2013,62(2):428-435
Wild and cultivated Fragaria chiloensis ssp. chiloensis (Fcc) plants were collected at different locations in southern Chile in order to determine the current viral status of this native strawberry. The following aphidborne viruses (ABVs): Strawberry mild yellow edge virus (SMYEV), Strawberry mottle virus (SMoV), Strawberry crinkle virus (SCV) and Strawberry vein banding virus (SVBV), were found in wild and cultivated Fcc plants, but severe symptoms were not associated with viral infection. Furthermore, partial gene sequences of these ABV isolates were determined and displayed a high degree of conservation with virus isolates reported previously. In addition, partial gene sequences of SCV and SVBV from southernmost South American populations of Fcc are described for the first time. High‐throughput parallel sequencing (Illumina) of double‐stranded RNA was used to provide viral profiles of Fcc from different locations. Although strong evidence of novel viruses affecting Fcc was not found, it was confirmed that ABVs are the most frequent viruses affecting this subspecies. The information provided will help in the development of high‐quality molecular tools for virus detection and control in Fcc. 相似文献
972.
Leigh G. Griffiths MA VETMB DSAS MRCVS Martin Sullivan BVMS PHD DVR MRCVS Turlough O''Neill MVB MACVSC MRCVS Stewart W. J. Reid BVMS PHD. MRCVS 《Veterinary radiology & ultrasound》2003,44(2):210-213
The tympanic bullae of 20 previously healthy cadaver animals were randomly filled with sterile saline or air. The heads were positioned using tape ties and a rostrocaudal open mouth radiograph taken. The resulting radiographs were assessed by a blinded ECVDI diplomate, with each tympanic bulla being recorded as being either air or fluid filled. Ultrasound examination of the bullae was performed, by a blinded assessor, using a B-mode 5 mHz sector probe (Sonotron-VingMed Sound A/S, PO Box 141, N3191, Horten, Norway) operating at 3 mHz. Each bulla was recorded as being either air or fluid filled. Results of radiography and ultrasonography were each compared to the actual status of the bulla in a chi square analysis. Sensitivity of radiography was 80%, with specificity of 65%. Ultrasonographic sensitivity was 100% and specificity 100%. Ultrasonography may in future provide a cheap, noninvasive, rapid and widely available method for diagnosing otitis media in clinical cases. 相似文献
973.
Sibylle Kneissl Dr. Med. Vet. Alexander Probst Dr. Med. Vet. Martin Konar Mag. Med. Vet. 《Veterinary radiology & ultrasound》2004,45(6):520-522
A series of low-field magnetic resonance images of the normal canine middle and inner ear are presented to serve as a reference. A completely balanced steady-state gradient echo pulse sequence with a slice thickness of 0.9 mm can be used to acquire images of the relevant structures within and neighboring the inner ear. These were the cochlear duct, semicircular ducts, vestibule, facial and vestibulocochlear nerves, as well as the temporal sinus. Within the middle ear, no applied sequence was able to allow identification of the auditory ossicles or the tympanic membrane. 相似文献
974.
975.
G Pugliesi SC Scolari FS Mesquita M Maturana Filho ER Araújo D Cardoso JN Sales I Martin M Sá Filho CM Bertan M Binelli 《Reproduction in domestic animals》2014,49(4):e35-e39
This short communication reports the impact of endometrial biopsies, uterine flushings and follicular fluid aspiration procedures at day 6 post artificial insemination (AI) on pregnancy rates. In Experiment 1, cows were timed AI (TAI) and assigned to the following treatment groups: control (n = 37), uterine flushing (n = 35) and endometrial biopsy (n = 38). On day 30 post AI, pregnancy rates were 40.5%, 33% and 28.5%, respectively (p > 0.1). Pregnancy rate on day 60 was lower (p < 0.004) in flushed cows than in the controls. In Experiment 2, oestrus was detected and cows were assigned to flushing (n = 32) or biopsy (n = 33) treatments 6 days after AI, which resulted in pregnancy rates of 31% and 36%, respectively (p > 0.1). In Experiment 3, cows were, 6 days after TAI, randomly assigned to the following treatments: control (n = 84) or aspiration of the largest follicle (n = 73). Pregnancy rates on day 30 post AI were 63.5% for the control group and 53% for the aspirated group (p > 0.1). In conclusion, uterine flushing and endometrial biopsy negatively affect pregnancy rates, but neither procedure can be considered to be incompatible with pregnancy maintenance. Follicular aspiration during pregnancy does not interact with pregnancy success. The amount and quality of samples obtained are compatible with the use of cellular and molecular analysis of uterine variables from cows that failed or succeeded on maintaining pregnancy. 相似文献
976.
H D Martin 《Journal of the American Veterinary Medical Association》1986,189(10):1332-1333
A female cockatiel had a 2-week history of abdominal distention, lethargy, and diarrhea. The cockatiel had a history of frequent egg-laying, and the owner suspected that she was egg-bound. A solid mass was removed through the cloaca and found to be a concretion of urates that had formed within a hernial pouch of the caudal abdominal musculature. Diagnosis was aided by contrast radiography, and surgery was performed. However, the abdominal hernias recurred 16 months later. The continual egg-laying probably predisposed this bird to hernia formation. Abdominal hernias in birds may be a consequence of continual egg-laying and associated hormonal effects leading to a weakening of abdominal musculature. 相似文献
977.
Gnos E Hofmann BA Al-Kathiri A Lorenzetti S Eugster O Whitehouse MJ Villa IM Jull AJ Eikenberg J Spettel B Krähenbühl U Franchi IA Greenwood RC 《Science (New York, N.Y.)》2004,305(5684):657-659
The lunar meteorite Sayh al Uhaymir 169 consists of an impact melt breccia extremely enriched with potassium, rare earth elements, and phosphorus [thorium, 32.7 parts per million (ppm); uranium, 8.6 ppm; potassium oxide, 0.54 weight percent], and adherent regolith. The isotope systematics of the meteorite record four lunar impact events at 3909 +/- 13 million years ago (Ma), approximately 2800 Ma, approximately 200 Ma, and <0.34 Ma, and collision with Earth sometime after 9.7 +/- 1.3 thousand years ago. With these data, we can link the impact-melt breccia to Imbrium and pinpoint the source region of the meteorite to the Lalande impact crater. 相似文献
978.
Martin GS 《Journal of the American Veterinary Medical Association》2000,217(12):1870-1877
OBJECTIVE: To evaluate effects of sex, fracture configuration, affected limb, and screw placement on outcome of Thoroughbreds with condylar fractures involving the third metacarpal or metatarsal bone. DESIGN: Cohort study. Animals-56 horses. PROCEDURE: Age, sex, affected limb, fracture configuration, fracture length, fracture fragment width, and distance of the most distal screw from the articular surface were analyzed in logistic regression models. RESULTS: Females were more likely to have displaced fractures and race in fewer races after surgery than males. Sex and fracture configuration were associated with number of postoperative races. Among horses that returned to racing, those with thicker fracture fragments were 11 times as likely as horses with thinner fracture fragments to win a race after surgery. Horses with longer fractures and older horses had fewer postoperative races. Horses in which the most distal screw had been placed further from the joint surface had more races. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that female horses with displaced condylar fractures and male horses with nondisplaced condylar fractures are more likely to be referred for treatment. The effect of sex on outcome for these horses cannot be clearly separated from the effect of fracture configuration. When adjusted for fracture configuration, males were 6 times as likely as females to race after surgery. When adjusted for sex, horses with nondisplaced fractures were 17 times as likely as horses with displaced fractures to race after surgery. Results suggest that the most distal screw should be placed above the epicondylar fossa. 相似文献
979.
980.
Camila Trevisan Pereira Fabio Luiz Navarro Marques Jamie Williams Benedicto Wlademir De Martin Pedro Primo Bombonato 《Veterinary radiology & ultrasound》2008,49(5):487-491
Lymphoscintigraphy is the technique of choice for sentinel lymph node detection in women with early breast cancer, but there is limited information evaluating the value of this technique in animals. We investigated mammary lymphatic drainage in 25 young female mongrel dogs by intramammary injection of 18.5 MBq of 99mTc-dextran (70,000 Da). Lymph node anatomical referencing was obtained using an external marker, bone scintigraphy, or scintiscanning the body contour. Cranial and caudal thoracic mammary glands drained into the cranial sternal lymph node and axillary lymph center. The cranial thoracic mammary gland also drained into the superficial cervical lymph node in two of five animals. The cranial abdominal gland was drained by the axillary lymph center. The caudal abdominal mammary gland was drained by the superficial inguinal lymph node in all animals and simultaneously by medial iliac lymph nodes in four of five animals. In one dog, this mammary gland was also drained by the mediastinal and the superficial cervical lymph nodes. The inguinal mammary gland was drained by superficial inguinal lymph nodes and simultaneously via the medial iliac lymph node in one animal. Lymphatic communications between lymph nodes were identified in 11 of 25 (44%) animals. 99mTc-dextran mammary lymphoscintigraphy was easy and rapid to perform and may provide valuable information for further studies. 相似文献