全文获取类型
收费全文 | 44249篇 |
免费 | 4512篇 |
国内免费 | 11篇 |
出版年
2023年 | 223篇 |
2022年 | 424篇 |
2021年 | 857篇 |
2020年 | 564篇 |
2019年 | 677篇 |
2018年 | 826篇 |
2017年 | 746篇 |
2016年 | 1227篇 |
2015年 | 2054篇 |
2014年 | 2218篇 |
2013年 | 2690篇 |
2012年 | 3325篇 |
2011年 | 3220篇 |
2010年 | 2100篇 |
2009年 | 1788篇 |
2008年 | 2495篇 |
2007年 | 2463篇 |
2006年 | 2312篇 |
2005年 | 2064篇 |
2004年 | 2002篇 |
2003年 | 1821篇 |
2002年 | 1770篇 |
2001年 | 665篇 |
2000年 | 619篇 |
1999年 | 637篇 |
1998年 | 450篇 |
1997年 | 365篇 |
1996年 | 346篇 |
1995年 | 356篇 |
1994年 | 316篇 |
1993年 | 312篇 |
1992年 | 419篇 |
1991年 | 359篇 |
1990年 | 359篇 |
1989年 | 367篇 |
1988年 | 368篇 |
1987年 | 339篇 |
1986年 | 268篇 |
1985年 | 298篇 |
1984年 | 303篇 |
1983年 | 269篇 |
1982年 | 262篇 |
1981年 | 231篇 |
1980年 | 212篇 |
1979年 | 217篇 |
1978年 | 185篇 |
1977年 | 185篇 |
1976年 | 183篇 |
1975年 | 198篇 |
1973年 | 170篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
The Murray River's 'Sea to Hume Dam' fish passage program: Progress to date and lessons learned 总被引:2,自引:0,他引:2
Since its commencement in 2001, a program to facilitate fish passage on a major stretch of Australia's longest river has installed eight structures, testing and modifying their design as they go. What are the results so far and what are the implications for future directions? 相似文献
53.
Antoine Wystrach Sebastian Schwarz Patrick Schultheiss Guy Beugnon Ken Cheng 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》2011,197(2):167-179
The Australian desert ant Melophorus bagoti often follows stereotypical routes through a cluttered landscape containing both distant panoramic views and obstacles (plants)
to navigate around. We created an artificial obstacle course for the ants between a feeder and their nest. Landmarks comprised
natural objects in the landscape such as logs, branches, and tussocks. Many ants travelled stereotypical routes home through
the obstacle course in training, threading repeatedly the same gaps in the landmarks. Manipulations altering the relations
between the landmarks and the surrounding panorama, however, affected the routes in two major ways. Both interchanging the
positions of landmarks (transpositions) and displacing the entire landmark set along with the starting position of the ants
(translations) (1) reduced the stereotypicality of the route, and (2) increased turns and meanders during travel. The ants
might have used the entire panorama in view-based travel, or the distal panorama might prime the identification and use of
landmarks en route. Despite the large data set, both options (not mutually exclusive) remain viable. 相似文献
54.
55.
Jean-Marie Delaissé Philippe Martin Marie-Françoise Verheyen-Bouvy Edmond-Jacques Nyns 《Biochimica et Biophysica Acta (BBA)/General Subjects》1981,676(1):77-90
The subcellular localization of the ω-hydroxylase of Saccharomycopsis lipolytica was assessed by the analytical fractionation technique, originally described by de Duve C., Pressman, B.C., Gianetto, R., Wattiaux, R. and Appelmans, F., and hitherto little, if at all, applied to yeast. Protoplasts were separated in six fractions by differential centrifugation. Some of these fractions were further fractioned by density gradient centrifugation. The distribution of ω-hydroxylase and 15 other constituents chosen as possible markers of its subcellular membranes has been established. ω-Hydroxylase resulted in being bound to a membrane that containes also cytochrome P-450 and NADPH-cytochrome c reductase. This membrane clearly differs from five other subcellular entities. (1) Mitochondria were characterized by particulate malate dehydrogenase, particulate Antimycin A-insensitive NADH-cytochrome c reductase, oligomycin-sensitive and K+-stimulated ATPase pH 9. (2) Most if not all of the catalase and urate oxidase is peroxisomal. (3) Free ribosomes account for most RNA. (4) Nucleoside diphosphatase is for the first time reported in a yeast and appears to belong to an homogeneous population of small membranes. (5) The soluble compartment contains magnesium pyrophosphatase, alkaline phosphatase, 5′-nucleotidase and part of the NADH-cytochrome c reductase. Latent arylesterase and ATPase pH7 have an unspecific distribution. Alkaline phosphodiesterase I has not been detected. 相似文献
56.
Martin T. R. Kuiper Marijke Holtrop Hans de Vries 《Molecular & general genetics : MGG》1988,213(2-3):519-528
57.
The clinical and laboratory findings in seven children with Kawasaki disease are reviewed. Four of the patients had the more complicated course that has characterized the cases diagnosed in North America. This suggests that the benign forms are often mistaken for other febrile illnesses. The patients were two girls and five boys ranging in age from 4 months to 7 years; six were Caucasian and one was a North American Indian. Fever, redness of the oral mucosa, an erythematous or scarlatiniform rash and cervical adenopathy were seen in all; six patients had the characteristic fingertip desquamation and nonexudative conjunctivitis. Cardiac involvement occurred in four patients, two of whom had coronary artery aneurysm or thrombosis. Arthritis or arthralgia was seen in six patients, and aseptic meningitis occurred in four. Of the three patients with jaundice two underwent laparotomy and excision of a hydropic gallbladder; one of them died from Klebsiella pneumoniae sepsis and disseminated intravascular coagulopathy. 相似文献
58.
59.
Martin Kaltenrieder 《Experimental & applied acarology》1990,9(3-4):267-278
The camel tick,Hyalomma dromedarii, exhibited positive scototaxis in an arena, e.g. it oriented towards a black or grey target in front of a white background. The degree of the scototactic response varied with the size and the elevation of the target, with its luminance contrast, with its shape and with the speed by which the target was moved: (1) the response to stationary and moving targets increased with increasing target size; (2) presentation of the targets at an elevation of 11o–15o induced the highest response; (3) the response decreased with decreasing luminance contrast of the target; (4) targets with the shape of a disk, a triangle standing on a vertex, a vertical bar or a silhouette of a dromedary caused high responses; a low response was observed when the target was a horizontal bar and there was no response to a striped pattern; (5) the smaller the size of a disk, the faster it had to be moved to elicit an optimum response.The smallest disk which elicited a significant response appeared under a visual angle of 4.8o for a thick at the starting point. The smallest dromedary-shaped silhouette which elicited a significant response corresponded to the silhouette of a real dromedary at a distance of 18 m. 相似文献
60.
Acquisition of Resistance to Extended-Spectrum Cephalosporins by Salmonella enterica subsp. enterica Serovar Newport and Escherichia coli in the Turkey Poult Intestinal Tract
下载免费PDF全文
![点击此处可从《Applied microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)