全文获取类型
收费全文 | 735篇 |
免费 | 13篇 |
专业分类
748篇 |
出版年
2021年 | 9篇 |
2020年 | 11篇 |
2019年 | 8篇 |
2018年 | 29篇 |
2017年 | 13篇 |
2016年 | 24篇 |
2015年 | 19篇 |
2014年 | 31篇 |
2013年 | 129篇 |
2012年 | 27篇 |
2011年 | 31篇 |
2010年 | 43篇 |
2009年 | 43篇 |
2008年 | 20篇 |
2007年 | 19篇 |
2006年 | 19篇 |
2005年 | 15篇 |
2004年 | 16篇 |
2003年 | 36篇 |
2002年 | 38篇 |
2001年 | 11篇 |
2000年 | 14篇 |
1999年 | 11篇 |
1998年 | 6篇 |
1997年 | 3篇 |
1996年 | 6篇 |
1995年 | 12篇 |
1994年 | 10篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1990年 | 5篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1987年 | 4篇 |
1985年 | 4篇 |
1984年 | 3篇 |
1983年 | 5篇 |
1982年 | 6篇 |
1981年 | 8篇 |
1980年 | 2篇 |
1979年 | 6篇 |
1977年 | 7篇 |
1976年 | 7篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1973年 | 4篇 |
1972年 | 2篇 |
1970年 | 2篇 |
1968年 | 3篇 |
1960年 | 2篇 |
排序方式: 共有748条查询结果,搜索用时 0 毫秒
1.
Corynebacterium equi IFO 3730 was found to oxidize a wide variety of sec-alcohols, including alkanols, substituted alkanols, alkenols and cyclic alcohols, in moderate to high yields. Among them, the sec-alcohols which have longer carbon chains were oxidized more smoothly than those with smaller numbers of carbon. Although both enantiomers of unsymmetrically disubstituted carbinols were oxidized, the S form of 2-dodecanol was converted to the corresponding ketone a little faster than the other enantiomer. 相似文献
2.
3.
Kôichi Takinami Hiroshi Okada Toshinao Tsunoda 《Bioscience, biotechnology, and biochemistry》2013,77(12):858-863
It has been found that although Brevibacterium lactofermentum No. 2256 is incapable of accumulating l-glutamic acid in a biotin sufficient medium, it produces a large quantity of the acid in the presence of sucrose fatty acid ester. In a biotin deficient medium, however, the ester brought the unfavorable diminution of l-glutamic acid accumulation caused by the decrease of glucose consumption in an incubation period. The undesirable effects were practically lost when the ester was added to the culture medium after more than eight hours in the course of incubation. This fact suggests that the ester is concerned with the growth of microorganism. It is very interesting to elucidate the interrelation between sucrose fatty acid ester and biotin. For the maximum accumulation of l-glutamic acid corresponding increase in amount of the ester to the increasing concentration of biotin was necessary. The proportional relation did not extend to excedingly high levels of the two implicating factors. The further observations concerning the effects of the individual fatty acid esters such as sucrose stearate remain unsatisfactory. 相似文献
4.
We examined sleeping site selection by chimpanzees (Pan troglodytes) in the Ugalla savanna woodland area, western Tanzania, from 1994 to 2012. We established 488 km of line transects and recorded 379 chimpanzee beds within 30 m perpendicular to the transects. Comparisons between 60 × 60 m2 quadrats containing new and recent beds and the remaining quadrats without beds along the transects indicated that evergreen forests accounted for disproportionately more area in quadrats with beds than in those without beds during both the dry and rainy seasons. In Ugalla, chimpanzees coexist with lions (Panthera leo) and leopards (Panthera pardus). They may sleep in forests to reduce predation risk by these carnivores, as trees are dense and the canopy is high and closed. The angle of slope was steeper in quadrats containing beds than in those without beds during the dry season, whereas the angle was less steep in quadrats with beds than in those without beds during the rainy season. Additionally, fewer beds were found further from forests. The distance between beds and forests during the dry season was shorter than that during the rainy season. Chimpanzees may sleep in or near forests and on slopes because of water pools in the valley forests along the slopes during the dry season. Quadrats with beds were at slightly higher altitude than those without beds during the rainy season; however, the difference was not significant during the dry season. The number of beds found in or close to feeding trees was not related to the fruiting period. Sleeping site selection by chimpanzees may be affected by predation pressure and water availability in the savanna woodland area. 相似文献
5.
6.
Masanori Tachikawa Go Ozeki Takanori Higuchi Shin‐ichi Akanuma Kazuhiro Tsuji Ken‐ichi Hosoya 《Journal of neurochemistry》2012,123(5):750-760
An increasing level of prostaglandin (PG) E2 is involved in the progression of neuroinflammation induced by ischemia and bacterial infection. Although an imbalance in the rates of production and clearance of PGE2 under these pathological conditions appears to affect the concentration of PGE2 in the cerebrospinal fluid (CSF), the regulatory system remains incompletely understood. The purpose of this study was to investigate the cellular system of PGE2 production via microsomal PGE synthetase‐1 (mPGES‐1), the inducible PGE2‐generating enzyme, and PGE2 elimination from the CSF via the blood–CSF barrier (BCSFB). Immunohistochemical analysis revealed that mPGES‐1 was expressed in the soma and perivascular sheets of astrocytes, pia mater, and brain blood vessel endothelial cells, suggesting that these cells are local production sites of PGE2 in the CSF. The in vivo PGE2 elimination clearance from the CSF was eightfold greater than that of d ‐mannitol, which is considered to reflect CSF bulk flow. This process was inhibited by the simultaneous injection of unlabeled PGE2 and β‐lactam antibiotics, such as benzylpenicillin, cefazolin, and ceftriaxone, which are substrates and/or inhibitors of organic anion transporter 3 (OAT3). The characteristics of PGE2 uptake by the isolated choroid plexus were at least partially consistent with those of OAT3. OAT3 was able to mediate PGE2 transport with a Michaelis–Menten constant of 4.24 μM. These findings indicate that a system regulating the PGE2 level in the CSF involves OAT3‐mediated PGE2 uptake by choroid plexus epithelial cells, acting as a cerebral clearance pathway via the BCSFB of locally produced PGE2. 相似文献
7.
Akifumi Makita Yasuo Konno Noboru Fujita Ken′ichi Takada Etsuji Hamabata 《Ecological Research》1993,8(2):215-224
The recovery process of aSasa tsuboiana population after a mass flowering and death in 1977 was investigated by 15 years of observation in the Hira Mountains, Kinki
district, western Japan. Seed production was high (6600–13 800 seeds m−2 inSasa plots and 3900 seeds m−2 in a forest plot) but emergent seedling density was low (14–21 seedlings m−2), probably because of seed predation byMicrotus montebelli occurring between seed shedding and the next spring. The seedling density had decreased further by the next year and theS. tsuboiana population recovered from only a limited number of seedlings. In spite of such a low initial density, theS. tsuboiana population was able to regenerate successfully and attained the previous full stand height in 7–16 years.Miscantbus sinensis invaded and delayed the recovery ofS. tsuboiana in one plot, butS. tsuboiana became dominant as it caught up with the height ofM. sinensis. Seedling growth patterns, such as frequent tillering, the onset of rhizome extension in the early stage of seedling growth
and frequent culm production from rhizomes, played important roles in the successful regeneration ofS. tsuboiana. 相似文献
8.
Two interesting microfungi are described as new to Japan:Talaromyces galapagensis (anam.Penicillium galapagense), isolated from soil in Shizuoka; andPenicillium megasporum, isolated from marine sludge in Nagasaki. Some observations are recorded, particularly on ascomatal initials ofT. galapagensis, which are similar to those described forTalaromyces flavus.(48): Kaneko, S., Mycoscience 36: 359–360, 1995. 相似文献
9.
Aspergillus taichungensis isolated from a soil sample collected in Taiwan is described as a new species. The new species is characterized by its restricted growth on Czapek's and malt extract agars and its white to light yellow colonies, radiate conidial heads, smooth and often diminutive conidiophores, hemispherical to elongate vesicles with biseriate aspergilla (conidiogenous cells), globose, micro-verrucose conidia and dark brown sclerotia. The species somewhat resemblesA. versicolor, A. terreus andA. flavipes, but differs in cultural and morphological details, and is considered to represent an interface species in the subgenusNidulantes. 相似文献
10.
Effect of roasting on ochratoxin A level in green coffee beans inoculated with Aspergillus ochraceus
Haruo Tsubouchi Katsuhiko Yamamoto Kazuo Hisada Yoshio Sakabe Shun- ichi Udagawa 《Mycopathologia》1987,97(2):111-115
The heat stability of ochratoxin A in green coffee beans inoculated with Aspergillus ochraceus was studied. Heat treatment (roasting) at 200 °C for 10 or 20 min reduced the levels of ochratoxin A by only 0–12% in the dried whole beans. Almost all of the ochratoxin A was infused into the coffee decoction when the roasted samples were ground and extracted with boiling water. Therefore, the reduction of ochratoxin A concentration of contaminated coffee beans by roasting under these conditions is ineffective. 相似文献