全文获取类型
收费全文 | 35700篇 |
免费 | 2951篇 |
国内免费 | 763篇 |
出版年
2023年 | 289篇 |
2022年 | 321篇 |
2021年 | 759篇 |
2020年 | 681篇 |
2019年 | 780篇 |
2018年 | 1104篇 |
2017年 | 1018篇 |
2016年 | 1439篇 |
2015年 | 2164篇 |
2014年 | 2206篇 |
2013年 | 2784篇 |
2012年 | 3315篇 |
2011年 | 3133篇 |
2010年 | 1904篇 |
2009年 | 1667篇 |
2008年 | 2224篇 |
2007年 | 2072篇 |
2006年 | 1992篇 |
2005年 | 1705篇 |
2004年 | 1661篇 |
2003年 | 1441篇 |
2002年 | 1363篇 |
2001年 | 306篇 |
2000年 | 200篇 |
1999年 | 264篇 |
1998年 | 275篇 |
1997年 | 204篇 |
1996年 | 182篇 |
1995年 | 176篇 |
1994年 | 157篇 |
1993年 | 170篇 |
1992年 | 135篇 |
1991年 | 115篇 |
1990年 | 102篇 |
1989年 | 81篇 |
1988年 | 73篇 |
1987年 | 61篇 |
1986年 | 47篇 |
1985年 | 93篇 |
1984年 | 93篇 |
1983年 | 53篇 |
1982年 | 66篇 |
1981年 | 54篇 |
1980年 | 45篇 |
1979年 | 38篇 |
1978年 | 33篇 |
1977年 | 31篇 |
1976年 | 45篇 |
1975年 | 31篇 |
1973年 | 26篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
2.
We report the first cases of polygyny for the Bearded Vulture Gypaetus barbatus in the central Pyrenees, Spain. Although polyandry is frequent in the study area (31.8% of all reproductive units in 2016), we only observed the occurrence of three cases of polygyny over the period 1994–2017. Polygyny in Bearded Vultures is possibly a consequence of habitat saturation. 相似文献
3.
4.
Isabel Bandín Ysabel Santos Beatriz Magariños Juan L. Barja Alicia E. Toranzo 《FEMS microbiology letters》1992,94(1-2):105-110
The analysis of the membrane proteins and their antigenic properties in a group of 14 geographically diverse strains of Renibacterium salmoninarum revealed the existence of antigenic diversity within this species. Eleven isolates, including the type strain ATCC 33209, shared a similar protein profile with a major component of 57 kDa whereas three strains showed a common pattern with a major protein of 30 kDa. The quantitative agglutination tests and Western blotting assays seem to indicate the existence of serological heterogeneity, with two distinct groups being detected. 相似文献
5.
Gabriel Moreno Gonzalo Platas Fernando Peláez Marieta Bernedo Alba Vargas Antonio Daza Carmen Santamaría María Camacho Luis Romero de la Osa José Luis Manjón 《Mycological Progress》2008,7(1):41-47
Amanita curtipes and A. ponderosa are two Mediterranean taxa sharing a number of morphological features as well as their habitat. Their synonymy or variety
status has been proposed by several authors. To clarify this taxonomic issue we have sequenced the D1-D2 domains of the 28S
rRNA gene as well as the complete ITS1-5.8S-ITS2 region of several specimens of the two species collected in Spain, and aligned
these sequences with those from other Amanita species. Molecular phylogenetic analysis based on the two regions revealed that A. ponderosa and A. curtipes are clearly distinct species. The distribution of Amanita species in the phylogenetic trees was consistent with the division of the genus in subgenera and sections as proposed by
previous authors. Sequences of A. ponderosa and A. curtipes were grouped in a monophyletic cluster together with other species of the section Amidella. However, A. ponderosa was closer to other species in the section, such as A. peckiana and A. volvata, than to A. curtipes. We also indicate the macromorphological characters that are most useful to reliably distinguish A. ponderosa and A. curtipes. 相似文献
6.
Francisco Eduardo Martin-Cano Mercedes Caso-Agundez Cristina Camello-Almaraz Francisco Juan Santos María Teresa Espin Juan Antonio Madrid Adolfo Diez-Perez Pedro Javier Camello Maria Jose Pozo 《Journal of physiology and biochemistry》2017,73(1):77-87
Urinary bladder function consists in the storage and controlled voiding of urine. Translational studies require animal models that match human characteristics, such as Octodon degus, a diurnal rodent. This study aims to characterize the contractility of the detrusor muscle and the morphology and code of the vesical plexus from O. degus. Body temperature was measured by an intra-abdominal sensor, the contractility of detrusor strips was evaluated by isometric tension recording, and the vesical plexus was studied by electrical field stimulation (EFS) and immunofluorescence. The animals showed a diurnal chronotype as judged from core temperature. The myogenic contractile response of the detrusor muscle to increasing doses of KCl reached its maximum (31.04 mN/mm2) at 60 mM. In the case of cumulative dose–response of bethanecol, the maximum response (37.42 mN/mm2) was reached at 3.2 × 10?4 M. The response to ATP was clearly smaller (3.8 mN/mm2). The pharmacological dissection of the EFS-induced contraction identified ACh and sensory fibers as the main contributors to this response. The neurons of the vesical plexus were located mainly in the trigone area, grouped in big and small ganglia. Out of them, 48.1 % of the neurons were nitrergic and 62.7 % cholinergic. Our results show functional and morphological similarities between the urinary bladder of O. degus and that of humans. 相似文献
7.
Marina Lozano Almudena Estalrrich Luca Bondioli Ivana Fiore José‐Maria Bermúdez de Castro Juan Luis Arsuaga Eudald Carbonell Antonio Rosas David W. Frayer 《Evolutionary anthropology》2017,26(6):313-324
Fossil hominids often processed material held between their upper and lower teeth. Pulling with one hand and cutting with the other, they occasionally left impact cut marks on the lip (labial) surface of their incisors and canines. From these actions, it possible to determine the dominant hand used. The frequency of these oblique striations in an array of fossil hominins documents the typically modern pattern of 9 right‐ to 1 left‐hander. This ratio among living Homo sapiens differs from that among chimpanzees and bonobos and more distant primate relatives. Together, all studies of living people affirm that dominant right‐handedness is a uniquely modern human trait. The same pattern extends deep into our past. Thus far, the majority of inferred right‐handed fossils come from Europe, but a single maxilla from a Homo habilis, OH‐65, shows a predominance of right oblique scratches, thus extending right‐handedness into the early Pleistocene of Africa. Other studies show right‐handedness in more recent African, Chinese, and Levantine fossils, but the sample compiled for non‐European fossil specimens remains small. Fossil specimens from Sima del los Huesos and a variety of European Neandertal sites are predominately right‐handed. We argue the 9:1 handedness ratio in Neandertals and the earlier inhabitants of Europe constitutes evidence for a modern pattern of handedness well before the appearance of modern Homo sapiens. 相似文献
8.
9.
10.
Renato Richard Hilário Caroline Silva Lucas Silva Santos Jr Patrício Adriano da Rocha Raone Beltrão-Mendes Juan Ruiz-Esparza 《Studies on Neotropical Fauna and Environment》2017,52(2):168-172
We report predation of four birds while caught in mist nets and recommend some means of prevention. Two birds were attacked by Callitrhix jacchus and one by Saguinus midas. The predator in the fourth case was unidentified. These cases were relatively rare, affecting 0.4–4.4% of the captured birds. Two of the predated birds were caught more than 1 m above the ground and may have been accessed from branches. The other two were caught close to the ground. Reducing time intervals between net checks and cutting off branches close to nets may reduce bird predation in mist nets. 相似文献