全文获取类型
收费全文 | 595篇 |
免费 | 39篇 |
国内免费 | 100篇 |
出版年
2023年 | 21篇 |
2022年 | 23篇 |
2021年 | 48篇 |
2020年 | 32篇 |
2019年 | 25篇 |
2018年 | 27篇 |
2017年 | 25篇 |
2016年 | 25篇 |
2015年 | 21篇 |
2014年 | 30篇 |
2013年 | 46篇 |
2012年 | 29篇 |
2011年 | 21篇 |
2010年 | 14篇 |
2009年 | 34篇 |
2008年 | 26篇 |
2007年 | 33篇 |
2006年 | 36篇 |
2005年 | 19篇 |
2004年 | 23篇 |
2003年 | 21篇 |
2002年 | 27篇 |
2001年 | 15篇 |
2000年 | 13篇 |
1999年 | 5篇 |
1998年 | 8篇 |
1997年 | 6篇 |
1996年 | 9篇 |
1995年 | 7篇 |
1994年 | 6篇 |
1992年 | 5篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 5篇 |
1985年 | 4篇 |
1984年 | 4篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 6篇 |
1979年 | 2篇 |
1978年 | 5篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有734条查询结果,搜索用时 15 毫秒
691.
Abstract Two native microbial consortia were isolated from the soil and drainage in the phosphate mines, and their abilities to solubilize low-grade rock phosphate (RP) in two different culture media, namely Pikovskaya (PKV) and National Botanical Research Institute’s phosphate (NBRIP) medium, respectively, were estimated. Results showed that the two microbial consortia could grow steadily in the solution and continuously released soluble phosphate from the RP during 14?d of experiments. This process was accompanied by a drop in pH of the solution. The microbial consortium isolated from the soil achieved the largest release of soluble phosphate and pH reduction in the PKV medium among the four microbial consortia named PS, NS, PD, and ND, respectively. Fourier transform infrared spectroscopy (FTIR) analysis of RP indicated that hydroxyl, alkyl C-H bond, amide, and carboxyl were involved in the RP solubilization, and significant changes of them were observed after the experiments. The four microbial consortia were sampled before and after the experiments for the analysis of their bacterial and fungal community structures by Illumina MiSeq sequencing. Results showed that the relative diversities and abundances of the dominant bacteria and fungi varied with different sampling sources (soil and drainage) and culture media (PKV and NBRIP medium). 相似文献
692.
Richard A. Osgood 《Hydrobiologia》1988,169(1):69-76
A mechanism for the upward translocation of phosphorus by flake-forming Aphanizomenon is hypothesized. Aphanizomenon germinates on oxic sediments and rises into the water column, then the flakes diurnally migrate. Observations from Spring Lake, Minnesota, U.S.A., indicate that Aphanizomenon translocates phosphorus to the summertime epilimnion. However, the observations cannot discriminate between which of two mechanisms related to Aphanizomenon flakes, upon germination or with subsequent diurnal migrations, is more important. 相似文献
693.
V. I. Grebenshchikova N. A. Kitaev E. E. Lustenberg V. I. Medvedev I. S. Lomonosov A. N. Karchevskii 《Contemporary Problems of Ecology》2009,2(1):12-21
Preliminary estimates of the abundance of uranium and its distribution among different environmental components (bedrock, soil, bottom sediments, surface water) in Pribaikal’e are reported. This element is widespread in the environment of this region. In some anomalous zones the uranium content many times exceeds the regional background level. A dual, natural and industrial, genesis of anomalous fields was established. The redistribution of uranium between different components of the environment of Pribaikal’e is quite essential. 相似文献
694.
Online Monitoring of Solid-Phase Peptide Syntheses on Glass-Type Surfaces Using White Light Interference 总被引:1,自引:0,他引:1
Hans-Martin Haake Rolf Tünnemann Andreas Brecht Volkhard Austel Günther Jung Günter Gauglitz 《Analytical biochemistry》2002,300(2):107-112
Label-free optical detection methods are of particular value for the investigation of biomolecular interactions. A label-free method based on reflectometric interference spectroscopy is described which enables both the on-line monitoring of solid phase peptide syntheses and subsequently the determination of antibody binding to these peptides without cleavage from the support. The method uses SiO(2) transducers that were modified with diaminopolyethylene glycol. The stepwise coupling of different amino acids to the transducer surface was investigated and the complete monitoring of the synthesis of a viral epitope was performed. The success of the synthesis was proven via binding of a specific monoclonal antibody to the transducer-bound product. In order to demonstrate specificity the binding was inhibited with the same peptide epitope added in solution. The approach is attractive especially in the field of high throughput screening since both the synthesis and the interaction with the biological receptor can be monitored using the same technique. 相似文献
695.
696.
V. I. Mitashov 《Russian Journal of Developmental Biology》2005,36(4):240-246
Studies have been considered, which concern identification of regulatory genes in adult newts and their expression during retinal and lens regeneration. B.L. Astaurov repeatedly urged to join efforts of geneticists and embryologists in studies of the mechanisms underlying biological phenomena. This was also true for studies of regeneration. Such studies became possible only after introduction of molecular biology methods. Studies of the mechanisms underlying regeneration have been recently carried out jointly by geneticists and developmental biologists. This review presented at the conference dedicated to the 100th anniversary of B.L. Astaurov deals with these aspects in studies of regeneration.__________Translated from Ontogenez, Vol. 36, No. 4, 2005, pp. 292–299.Original Russian Text Copyright © 2005 by Mitashov. 相似文献
697.
698.
Christoph F. Richter Christopher J. Lortie Tamara L. Kelly Alessandro Filazzola Krystal A. Nunes Raani Sarkar 《Ecology and evolution》2021,11(8):3616
Teaching ecology effectively and experientially has become more challenging for at least two reasons today. Most experiences of our students are urban, and we now face the near immediate and continuing need to deliver courses (either partially or wholly) online because of COVID‐19. Therefore, providing a learning experience that connects students to their environment within an ecological framework remains crucial and perhaps therapeutic to mental health. Here, we describe how prior to the pandemic we adapted our field‐based laboratories to include data collection, analysis, and interpretation, along with the development of a citizen‐science approach for online delivery. This design is simple to implement, does not require extensive work, and maintains the veracity of original learning outcomes. Collaboration online following field data collection in ecology courses within the context of cities offers further options to adapt to student experience levels, resource availability, and accessibility, as well as bringing instructors and students together to build an open well‐curated data set that can be used in ecology courses where no laboratories are available. Finally, it promotes an open collaboration among ecology instructors that can drive lasting conversations about ecology curriculum. 相似文献
699.
700.
《Anthrozo?s》2013,26(3):287-300
ABSTRACTMainland Portugal is not renowned for having been a whaling nation of significance. However, preliminary studies have brought to light enough historical references to suggest that whaling occurred from at least the 13th century, and the present work identifies 38 historical sources documenting whale use or whaling on the Portuguese coast between 1201 and 1728. A peak of whale-related sources occurred during the 13th and 14th centuries, and almost all Portuguese accounts are contemporary to those found from the French and Spanish Basque countries, such that the beginning of the whaling activity seems to be coeval. No geographical cluster of whaling activities can be established—they seem to have been unevenly scattered along the entire coastline. Nor can a chronological north–south movement of coastal whaling activities be discerned. The geographical and chronological patterns give support to the assumption that whaling was not introduced to Portugal by the Basques, who are known to have spread westward from the French Labourd (11th century), via Golf of Biscay, to Asturias, and southward to Galicia (14th century). Rather, Portuguese whale use seems to have originated independently of Basque influence. Several of the sources specify “black whales” as the target species. This is consistent with modern knowledge about the distribution and migration patterns of North Atlantic right whales during Basque medieval and early modern whaling. The Portuguese sources are not clear as to numbers of whales taken, nor to the whaling technology used, but the activity was sufficiently well organized and developed to warrant the levying of tithes in the feudal system of 13th-century Portugal. 相似文献