全文获取类型
收费全文 | 2606篇 |
免费 | 122篇 |
国内免费 | 2篇 |
出版年
2023年 | 6篇 |
2022年 | 11篇 |
2021年 | 24篇 |
2020年 | 16篇 |
2019年 | 24篇 |
2018年 | 24篇 |
2017年 | 48篇 |
2016年 | 40篇 |
2015年 | 80篇 |
2014年 | 91篇 |
2013年 | 154篇 |
2012年 | 141篇 |
2011年 | 140篇 |
2010年 | 101篇 |
2009年 | 102篇 |
2008年 | 162篇 |
2007年 | 137篇 |
2006年 | 159篇 |
2005年 | 145篇 |
2004年 | 161篇 |
2003年 | 153篇 |
2002年 | 156篇 |
2001年 | 59篇 |
2000年 | 55篇 |
1999年 | 65篇 |
1998年 | 33篇 |
1997年 | 28篇 |
1996年 | 24篇 |
1995年 | 17篇 |
1994年 | 22篇 |
1993年 | 33篇 |
1992年 | 31篇 |
1991年 | 30篇 |
1990年 | 25篇 |
1989年 | 27篇 |
1988年 | 20篇 |
1987年 | 22篇 |
1986年 | 23篇 |
1985年 | 22篇 |
1984年 | 11篇 |
1983年 | 10篇 |
1982年 | 18篇 |
1981年 | 13篇 |
1980年 | 8篇 |
1979年 | 7篇 |
1978年 | 8篇 |
1977年 | 6篇 |
1976年 | 6篇 |
1971年 | 4篇 |
1970年 | 6篇 |
排序方式: 共有2730条查询结果,搜索用时 15 毫秒
61.
Both the floral biology and morphometrics of two Japanese species of AsianDisporum (sectionEudisporum) are presented. These two species,D. sessile andD. smilacinum, represent extremes in both floral morphology and divergence in pollination within the section. The inverted flowers ofD. sessile have an elongate floral tube formed by the imbrication of the oblanceolate tepals. The tepal bases are modified into well developed, saccate nectaries. The stamens have rigid, vertical filaments which tightly encircle the ovary-style axis, and extrorse anthers located within a floral cavity which can accommodate a large pollinator (cross-pollination). The stigma is exserted and the depth of its cleft formation constant.D. smilacinum, in contrast, has an open, nodding campanulate flower with lanceolate tepals which have only shallow nectaries at their bases. The stamens have widely divergent filaments with versatile anthers that have laterally introrse dehiscence (wind and/or self-pollination). The depth of the stigma cleft is variable. For both species, the pattern of differential UV absorption and reflectance is similar. It is suggested on morphological grounds and by pollinator observation, thatD. sessile with a high energy flower requiring specialized visitors represents a more advanced condition than that observed inD. smilacinum, which is more generalized and primitive. Seasonal herbivore pressure on the tepal nectaries ofD. sessile is discussed in relation to its pollination. 相似文献
62.
The floral biology ofErythronium japonicum has been studied from two approaches: a reinvestigation of its floral morphology and a pollinator case history. The perianth,
differentiated into a sepal and petal cycle, has a tubular, but free arrangement basally around a slightly stipitate ovary.
The two cycles of stamens with dimorphic filaments are positioned by the differently lobed auricles of the mature sepals and
petals. These auricles also form a trap-lid mechanism for the inverted nectary which also has passageways. The perianth parts
are highly UV absorbant due to the presence of flavonoids. This pattern contrasts strikingly with the purple trident basal
guide lines so prominent in the visible spectrum. The weakly protandrous flowers also have exserted styles, thus functioning
to exclude its own pollen and insure outbreeding. These floral adaptations are related specifically to the pollination behavior
ofXylocopa appendiculata, and in general to the floral evolution within the genusErythronium.
This work was supported in part by the U.S.-Japan Cooperative Science Program Grant GF-41367 and Grant-in-Aid No. 934053 from
the Ministry of Education, Japan. 相似文献
63.
64.
In this paper, four fungi collected in Nansei Islands are reported. One is Strasseria garciniae, which must be transferred to the genus Phyllosticta. This fungus was collected in Okinawa Main Island and Iriomote Island. The other three fungi are newly added to the Japanese fungal flora. Phyllosticta ghaesembillae on Codiaeum variegatum and Cercospora asplenii on Asplenium antiquum were collected in Yoron Island. The last one, Coniella australiensis on Eucalyptus robusta was collected in Okinawa Main Island. Their morphology and symptoms on the host plant are described, with some mycological notes. 相似文献
65.
Alberto Kawano K.P. Gunaga K.M.J. Menon 《Biochimica et Biophysica Acta (BBA)/General Subjects》1975,385(1):88-100
A cell suspension was prepared from immature rat ovaries by treatment with trypsin and collagenase. The isolated cells were capable of converting [8-14C]adenine to cyclic [14C]AMP and the rate of this conversion was stimulated in vitro by luteinizing hormone and human chorionic gonadotropine, but not by prolactin, norepinephrine, dopamine or albumin. The accumulation of progesterone was also measured in these cells by radioimmunoassay. In vitro addition of luteinizing hormone stimulated the accumulation of radioimmunoassayable progesterone. The conversion of [8-14C]adenine to cyclic [14C]AMP showed a rapid increase during the first 30 min of the incubation period when luteinizing hormone was added to the incubation medium. Progesterone accumulation in response to the same dose of luteinizing hormone showed a lag period for the first 30 min of incubation after which there was an increase up to 2 h. The luteinizing hormone-induced progesterone accumulation was sensitive to puromycin, but there was no effect on the luteinizing hormone-induced increase in cyclic [14C]AMP formation from [8-14C]-adenine. Actinomycin D also inhibited the luteinizing hormone-induced progesterone accumulation, with no effect on cyclic AMP formation. The results suggest that the luteinizing hormone-induced progesterone accumulation in rat ovarian interstitial cell suspension is preceded by an increased accumulation of cyclic AMP and that the accumulation of steroid under the influence of luteinizing hormone involve processes sensitive to puromycin and antinomycin D. 相似文献
66.
67.
Matsumoto Narihisa Mototake Yoh-ichi Kawano Kenji Okada Masato Sugase-Miyamoto Yasuko 《Journal of computational neuroscience》2021,49(3):251-257
Journal of Computational Neuroscience - Feed-forward deep neural networks have better performance in object categorization tasks than other models of computer vision. To understand the relationship... 相似文献
68.
Takemura Aya Matsumoto Junya Hashimoto Ryota Kawano Kenji Miura Kenichiro 《Journal of computational neuroscience》2021,49(3):273-282
Journal of Computational Neuroscience - When two-frame apparent motion stimuli are presented with an appropriate inter-stimulus interval (ISI), motion is perceived in the direction opposite to the... 相似文献
69.
70.
Ben?Jomàa-Jemili?Mariem Teruyo?ItoEmail author Meng?Zhang Jingxun?Jin Shanshuang?Li Boutiba-Ben?Boubaker?Ilhem Hammami?Adnan Xiao?Han Keiichi?Hiramatsu 《BMC microbiology》2013,13(1):2