全文获取类型
收费全文 | 531篇 |
免费 | 25篇 |
专业分类
林业 | 76篇 |
农学 | 10篇 |
51篇 | |
综合类 | 21篇 |
农作物 | 17篇 |
水产渔业 | 78篇 |
畜牧兽医 | 269篇 |
园艺 | 6篇 |
植物保护 | 28篇 |
出版年
2023年 | 1篇 |
2022年 | 9篇 |
2021年 | 18篇 |
2020年 | 11篇 |
2019年 | 5篇 |
2018年 | 8篇 |
2017年 | 15篇 |
2016年 | 14篇 |
2015年 | 20篇 |
2014年 | 14篇 |
2013年 | 33篇 |
2012年 | 28篇 |
2011年 | 31篇 |
2010年 | 14篇 |
2009年 | 18篇 |
2008年 | 37篇 |
2007年 | 42篇 |
2006年 | 26篇 |
2005年 | 40篇 |
2004年 | 28篇 |
2003年 | 21篇 |
2002年 | 18篇 |
2001年 | 24篇 |
2000年 | 19篇 |
1999年 | 7篇 |
1998年 | 3篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1993年 | 1篇 |
1992年 | 3篇 |
1991年 | 5篇 |
1990年 | 3篇 |
1989年 | 6篇 |
1988年 | 5篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1982年 | 4篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1975年 | 1篇 |
1974年 | 3篇 |
1973年 | 1篇 |
1968年 | 1篇 |
1963年 | 1篇 |
排序方式: 共有556条查询结果,搜索用时 78 毫秒
51.
Nestlings of some brood parasitic birds evict hosts' eggs and young soon after hatching, thereby avoiding discrimination by hosts while monopolizing parental care. Eviction carries a cost, however, because lone parasitic nestlings attract a reduced provisioning rate. Here we describe a form of visual signaling used by the evicting Horsfield's hawk-cuckoo (Cuculus fugax) to obtain sufficient food. The chick displays a gape-colored patch on the wing to the host parents as they deliver food, simulating the gaping display of more than one nestling. 相似文献
52.
Sekitani T Noguchi Y Hata K Fukushima T Aida T Someya T 《Science (New York, N.Y.)》2008,321(5895):1468-1472
By using an ionic liquid of 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, we uniformly dispersed single-walled carbon nanotubes (SWNTs) as chemically stable dopants in a vinylidene fluoride-hexafluoropropylene copolymer matrix to form a composite film. We found that the SWNT content can be increased up to 20 weight percent without reducing the mechanical flexibility or softness of the copolymer. The SWNT composite film was coated with dimethyl-siloxane-based rubber, which exhibited a conductivity of 57 siemens per centimeter and a stretchability of 134%. Further, the elastic conductor was integrated with printed organic transistors to fabricate a rubberlike active matrix with an effective area of 20 by 20 square centimeters. The active matrix sheet can be uniaxially and biaxially stretched by 70% without mechanical or electrical damage. The elastic conductor allows for the construction of electronic integrated circuits, which can be mounted anywhere, including arbitrary curved surfaces and movable parts, such as the joints of a robot's arm. 相似文献
53.
Soybean 'Harosoy' is resistant to Cucumber mosaic virus soybean strain C (CMV-SC) and susceptible to CMV-S strain D (CMV-SD). Using enzyme-linked immunosorbent assay and Northern hybridization, we characterized the Harosoy resistance and found that CMV-SC did not spread systemically but was restricted to the inoculated leaves in Harosoy. Harosoy resistance was not controlled by either a dominant or recessive single gene. To dissect this system controlling long-distance movement of CMV in soybean, we constructed infectious cDNA clones of CMV-SC and CMV-SD. Using these constructs and the chimeric RNAs, we demonstrated that two viral components were required for systemic infection by the virus. The region including the entire 2b gene and the 5' region of RNA3 (mainly the 5' untranslated region) together were required. By quantitative trait locus (QTL) analysis using an F(2) population and the F(3) families derived from Harosoy and susceptible 'Nemashirazu', we also showed that at least three QTLs affected systemic infection of CMV in soybean. Our study on Harosoy resistance to CMV-SC revealed an interesting mechanism, in which multiple host and viral genes coordinately controlled viral systemic infection. 相似文献
54.
Norio Fukuzaki Tsuyoshi Ohizumi Kazuhide Matsuda 《Water, air, and soil pollution》2001,130(1-4):1673-1678
The geographical and temporal variations of chemical constituents in winter precipitation collected in the areas along the coast of the Sea of Japan (AASJ) were discussed by analyzing the data obtained in the 1st and 2nd National Acid Deposition Survey by Japan Environmental Laboratories Association. In western Tohoku (WT) and Hokuriku (HR) areas in AASJ, in spite of large amounts of precipitation in winter, concentrations of non sea salt (nss-)SO4 2? are not as low as the other areas, and nss-Ca2+ in these areas is lower than the other areas. As a result, H+ concentrations of precipitation in these areas are somewhat higher than other areas. From the temporal analysis of daily sampled data and back trajectory analysis of air mass, it was found that the concentrations of nss-SO4 2?, NO3 ?, NH4 + and nss-Ca2+ are correlatively varied when air mass come from the Asian Continent, showing higher concentrations at the western sites in AASJ and depending on the meteorological conditions such as the direction of in flow air mass. 相似文献
55.
Hiroshi Hara Moritsugu Kitamura Atsuko Mori Izumi Noguchi Tsuyoshi Ohizumi Sinya Seto Tadashi Takeuchi Teruyuki Deguchi 《Water, air, and soil pollution》1995,85(4):2307-2312
Precipitation chemistry in Japan was discussed on a wet-only sample database obtained in a nationwide survey from April 1989 to March 1993. Wet-only samples were collected at 29 stations over Japan on a biweekly basis. Commonly determined chemical parameters were measured in laboratories. The volume-weighted annual mean pH at each site ranged from 4.50 to 5.83 with a mean of 4.76. Concentration ranges and means (parenthesized) on an equivalent basis for major ions were as follows: nss-SO4
2–; 5.2–58.9 (38.6), NO3
–; 1.8–25.0 (14.1), NH4
+; 0.55–29.8 (18.3), nss-Ca2+; 2.0–34.5(14.2), Na+; 6.4–275.3 (49.1), Cl–; 13.7–322.4 (63.5) eq L–1. Acid-base relationships for Phase-II records were quantitatively discussed in terms of three measures: pH, fractional acidity, and our proposed pAi. 相似文献
56.
Diah Tri WIDAYATI Yasushige OHMORI Tsuyoshi WAKITA Katsuhiro FUKUTA 《Animal Science Journal》2003,74(4):261-267
An experimental model to study interspecific pregnancy using voles, Microtus arvalis, and green fluorescent protein gene‐induced transgenic mice is presented. Xenogeneic blastocysts from the vole were transferred into the uteri of pseudopregnant mice along with allogeneic blastocysts from green fluorescent protein gene‐induced transgenic mice. The uteri containing xeno‐allo combined transfers were examined from day 6 to 13 of gestation. Although the vole embryos implanted, the uteri containing vole embryos were smaller compared with those having allogeneic mouse embryos. On day 8, the uteri containing vole embryos hemorrhaged internally and no vole embryo was found in the pregnant uterus after day 11. Allogeneic mouse embryos developed normally despite the presence and abortion of the vole embryos. In uteri implanted with vole embryos, decidua were formed and numerous blood vessels were distributed around the embryo. Maternal blood cells infiltrated into the celomic cavity of the vole embryo through the discontinuous region of trophoblast. Periodic acid‐Schiff‐positive granulated metrial gland cells were remarkably increased in the decidual sites. These findings suggest that a disorder of embryo–maternal interaction might induce the appearance of numerous granulated metrial gland cells and rejection of the embryos. 相似文献
57.
Characteristics of Dorsal Lingual Papillae of the Bactrian Camel (Camelus bactrianus) 总被引:2,自引:0,他引:2
EErdunchaoluTakehana Yamamoto Kobayashi Cao BAIYIN Ueda & Tangkawattana 《Anatomia, histologia, embryologia》2001,30(3):147-151
The morphology of dorsal lingual papillae of the Bactrian camel (Camelus bactrianus) was studied by using light and scanning electron microscopy. Filiform and lenticular papillae were considered as mechanical papillae but fungiform and vallate papillae were considered as gustatory papillae. Filiform papillae were distributed mostly in the anterior two-thirds region of the tongue. Each filiform papilla consisted of one primary papilla and a few smaller secondary papillae. Lenticular papillae were distributed on the torus linguae. The larger papillae were arranged in two parallel lines medially whereas the smaller papillae were laterally located. Most of the fungiform papillae were found on the lateral margins of the anterior two-thirds of the tongue. These papillae were small and round. Intra-epithelial taste buds were located on the dorsal surface of each papilla. The vallate papillae were arranged in two rows on each rim of the torus linguae. Each round- and flat-shaped vallate papilla was surrounded by a prominent gustatory groove and an annular pad. A few taste buds were observed in the lateral epithelium of the papillae. The keratinization of the covering stratified squamous epithelium of the mechanical lingual papillae was relatively thicker than those of the gustatory papillae. The lingual papillae of the Bactrian camel exhibited some different characteristics from other domestic ruminants. These morphological characteristics of the tongue of the Bactrian camel might have evolved to assist the camel in prehension and manipulating of the inorganic stiff plants that grow in its environment and therefore might relate to the feed and feeding habits of the animal. 相似文献
58.
59.
N Fujikake H Togashi M Yamamoto K Arishima Y Ueda Y Eguchi 《Nippon juigaku zasshi. The Japanese journal of veterinary science》1989,51(2):416-424
The gubernaculum consists of the gubernacular cord connected with the vas deferens and the gubernacular bulb connected with the retroabdominal wall. The cord was first distinguished on day 15 of gestation. Its length reached the peak on day 16, followed by a reduction until day 18 to be almost constant thereafter. The bulb was first distinguished on day 16, and its length was steadily increased toward term. The testis began to descend with a reduced length of the cord. By day 19, the testis descended close to the caudal part of the bulb by the sharp bending of the cord. Microscopically, the bulb consisted at first of a centrally located mesenchymal mass and of a covering layer of myoblasts. Thereafter, the mesenchymal mass was gradually shifted toward the cranial part of the bulb, trailing loose mesenchymal tissue in the caudal part of the bulb. On day 19, the mass was decreased in cell population but increased in amount of collagen fibers. It is suggested that the testicular descent starts on day 16 together with the commencement of shortening of the gubernacular cord and enlargement of the gubernacular bulb. 相似文献
60.