全文获取类型
收费全文 | 106594篇 |
免费 | 5629篇 |
国内免费 | 64篇 |
专业分类
林业 | 3814篇 |
农学 | 3000篇 |
基础科学 | 699篇 |
12876篇 | |
综合类 | 18040篇 |
农作物 | 4037篇 |
水产渔业 | 4823篇 |
畜牧兽医 | 57362篇 |
园艺 | 1149篇 |
植物保护 | 6487篇 |
出版年
2018年 | 1483篇 |
2017年 | 1680篇 |
2016年 | 1512篇 |
2015年 | 1215篇 |
2014年 | 1612篇 |
2013年 | 4230篇 |
2012年 | 2799篇 |
2011年 | 3571篇 |
2010年 | 2298篇 |
2009年 | 2367篇 |
2008年 | 3441篇 |
2007年 | 3237篇 |
2006年 | 3119篇 |
2005年 | 2676篇 |
2004年 | 2626篇 |
2003年 | 2596篇 |
2002年 | 2414篇 |
2001年 | 3220篇 |
2000年 | 3349篇 |
1999年 | 2544篇 |
1998年 | 1018篇 |
1997年 | 999篇 |
1995年 | 1219篇 |
1994年 | 1053篇 |
1993年 | 1017篇 |
1992年 | 2244篇 |
1991年 | 2383篇 |
1990年 | 2249篇 |
1989年 | 2266篇 |
1988年 | 2104篇 |
1987年 | 2201篇 |
1986年 | 2245篇 |
1985年 | 2127篇 |
1984年 | 1726篇 |
1983年 | 1532篇 |
1982年 | 1015篇 |
1979年 | 1727篇 |
1978年 | 1381篇 |
1977年 | 1221篇 |
1976年 | 1256篇 |
1975年 | 1310篇 |
1974年 | 1619篇 |
1973年 | 1625篇 |
1972年 | 1540篇 |
1971年 | 1394篇 |
1970年 | 1359篇 |
1969年 | 1298篇 |
1968年 | 1173篇 |
1967年 | 1204篇 |
1966年 | 1103篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
181.
P L Vogel J Komtebedde D C Hirsh P H Kass 《Journal of the American Veterinary Medical Association》1999,214(11):1641-1643
OBJECTIVE: To detect contamination of wound sites from surgical handling of excised tissues during total ear canal ablation and lateral bulla osteotomy in dogs, and to compare susceptibility of bacterial isolates to cefazolin with susceptibility to other antimicrobial agents. DESIGN: Prospective clinical study. ANIMALS: 13 dogs. PROCEDURE: Dogs were treated surgically for otitis externa and media via total ear canal ablation and lateral bulla osteotomy. Specimens for aerobic bacterial culture were obtained from SC tissue immediately following skin incision, tissues excised from the osseous bulla (after transection of the horizontal ear canal and lateral bulla osteotomy), and from SC tissue prior to skin closure. Antimicrobial susceptibility of bacterial isolates to various antibiotics was determined by use of a broth dilution assay. RESULTS: There was a significant association between isolation of Streptococcus canis and Escherichia coli from specimens from the osseous bulla and specimens from the SC tissues prior to skin closure, indicating contamination of the SC tissues during surgery. Seventy percent of bacterial isolates were susceptible to cefazolin. CLINICAL IMPLICATIONS: Measures to limit bacterial contamination resulting from tissue handling during total ear canal ablation and lateral bulla osteotomy are necessary. Bacteriologic culture of tissue of the osseous bulla and determination of antimicrobial susceptibility are recommended. Administration of cefazolin alone may not be efficacious for antimicrobial prophylaxis. 相似文献
182.
A new nematode species, Rhabdochona longleyi sp. n. is described from the intestine of two species of blind catfishes, Trogloglanis pattersoni Eigenmann (type host) and Satan eurystomus Hubbs et Bailey (both fam. Ictaluridae, Siluriformes) from the subterranean waters (artesian wells penetrating San Antonio pool of Edwards Aquifer) of Texas, USA. It is characterized largely by the presence of only six anterior teeth in the prostom, simple deirids, by the shape and length of spicules (0.42 to 0.50 mm and 0.093-0.102 mm), shape of the tail tip (rounded), and by filamented eggs. R. longleyi probably adapted to the environment of the aquifer by utilizing available troglobitic crustaceans instead of aquatic insects as an intermediate host. 相似文献
183.
Schnell RJ Kuhn DN Brown JS Olano CT Phillips-Mora W Amores FM Motamayor JC 《Phytopathology》2007,97(12):1664-1669
ABSTRACT Production of cacao in tropical America has been severely affected by fungal pathogens causing diseases known as witches' broom (WB, caused by Moniliophthora perniciosa), frosty pod (FP, caused by M. roreri) and black pod (BP, caused by Phytophthora spp.). BP is pan-tropical and causes losses in all producing areas. WB is found in South America and parts of the Caribbean, while FP is found in Central America and parts of South America. Together, these diseases were responsible for over 700 million US dollars in losses in 2001 (4). Commercial cacao production in West Africa and South Asia are not yet affected by WB and FP, but cacao grown in these regions is susceptible to both. With the goal of providing new disease resistant cultivars the USDA-ARS and Mars, Inc. have developed a marker assisted selection (MAS) program. Quantitative trait loci have been identified for resistance to WB, FP, and BP. The potential usefulness of these markers in identifying resistant individuals has been confirmed in an experimental F(1) family in Ecuador. 相似文献
184.
Eurasian Soil Science - Sorption properties of humic acid (HA) preparations extracted from the peaty horizon of peat gley tundra soil (Histic Reductaquic Cryosols) are characterized. The kinetic... 相似文献
185.
186.
187.
Daniel D. Gallaher Kimberly J. Wood Cynthia M. Gallaher Leonard F. Marquart Alta M. Engstrom 《Cereal Chemistry》1999,76(1):21-24
The intestinal contents viscosities of oat-based breakfast cereals and muffins were examined. Male Sprague-Dawley rats were adapted for four days to a semipurified diet (AIN-76A). Following an overnight fast, the animals were meal-fed 5 g of either the AIN-76A diet (containing 5% cellulose), the AIN-76A diet containing 2% guar gum, whole-grain oat flour, one of five cereals (corn flakes, cooked oatmeal, uncooked oatmeal, cooked oat bran, or Cheerios), or one of two types of muffins (containing whole-grain oat flour or oatmeal). Two hours after presentation of the meal, the animals were killed, the small intestines removed, and the contents collected. The contents were centrifuged, and the viscosity values of the undiluted supernatants were determined. The supernatant viscosity from rats fed the AIN-76A diet was negligible (<5 mPa·sec), whereas that from rats fed guar gum was high (396 ± 117 mPa·sec). Of the cereals fed, corn flakes resulted in the lowest viscosity (<5 mPa·sec). However, all oat-based cereals resulted in high intestinal contents supernatant viscosity levels (cooked oatmeal 368 ± 128, uncooked oatmeal 307 ± 107, cooked oat bran 301 ± 85, Cheerios 199 ± 58, mPa·sec) with no statistically significant differences. The intestinal contents viscosity values for the whole-grain oat flour muffin and oatmeal muffin were 233 ± 52 and 111 ± 26 mPa·sec, respectively, a statistically significant difference (P < 0.05). This suggests that the form of the oat within a food may influence the degree of viscosity produced within the small intestine after that food is consumed. 相似文献
188.
189.
Twelve anestrous adult Greyhound bitches were used to study a regimen for induction of estrus. Once daily, 7 bitches were given diethylstilbestrol (DES; 5 mg, PO) until sanguineous vaginal discharge and vulvar edema were observed (designated as day 1 of proestrus) and for 2 days thereafter. If no response was elicited after 7 days, a doubled DES dose was given for up to an additional 7 days. Luteinizing hormone (5 mg, IM) was given on day 5 of proestrus, and follicle-stimulating hormone (10 mg, IM) was given on days 9 and 11 of proestrus. Bitches were bred once on day 13. Five bitches were used as a control group; they were given candy tablets for 7 days (first day on tablets, treatment day 1) and 0.9% NaCl (1.0 ml, IM) on treatment days 12, 16, and 18. The 7 bitches treated with DES had a mean proestrus period of 7.7 days and a mean estrus period of 5.7 days up to the day of mating. After mating, they had a mean gestation interval of 64 days and delivered a mean of 4 pups/litter. In 5 bitches, initial treatment with 5 mg of DES/day induced proestrus within 7 days; however, in 2 bitches, additional treatment with 10 mg of DES/day was needed for 5 and 6 days, respectively. Serum estradiol-17 beta and progesterone concentrations remained at base line during the period of DES treatment. Concentrations of both hormones increased after injection with luteinizing hormone and remained high for the next 4 days.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
190.
Assessment of defined antigens for the diagnosis of bovine tuberculosis in skin test-reactor cattle 总被引:17,自引:0,他引:17
Pollock JM Girvin RM Lightbody KA Clements RA Neill SD Buddle BM Andersen P 《The Veterinary record》2000,146(23):659-665
The continued use of purified protein derivative (PPD) tuberculin is considered to be the main factor which limits the specificity of diagnostic tests for bovine tuberculosis (TB). This study evaluated a whole blood interferon-gamma (IFN-gamma) assay and compared the diagnostic potential of PPD with two tuberculosis-specific antigens, ESAT-6 and MPB70. To provide estimates of sensitivity and specificity, responses were measured in 180 skin test-reacting cattle, of which 131 were confirmed as tuberculous, and in 128 cattle from TB-free herds. For the skin test reactors, there was a positive correlation between the IFN-gamma responses to PPD from Mycobacterium bovis (PPDB) and PPD from Mycobacterium avium (PPDA), indicating cross-reactivity between these complex antigens which are the basis of the skin test. In comparisons of the ESAT-6 IFN-gamma test with a PPD IFN-gamma test (using PPDB compared with PPDA), there was a decrease in sensitivity (76.3 per cent vs 89.3 per cent), but a clear increase in specificity (99.2 per cent vs 92.2 per cent). The provision of high specificity, even with lower sensitivity, offers major benefits for testing in areas with a low incidence of TB. 相似文献