全文获取类型
收费全文 | 698篇 |
免费 | 143篇 |
出版年
2022年 | 7篇 |
2021年 | 13篇 |
2018年 | 11篇 |
2017年 | 16篇 |
2016年 | 14篇 |
2015年 | 23篇 |
2014年 | 16篇 |
2013年 | 20篇 |
2012年 | 24篇 |
2011年 | 27篇 |
2010年 | 17篇 |
2009年 | 19篇 |
2008年 | 22篇 |
2007年 | 30篇 |
2006年 | 29篇 |
2005年 | 24篇 |
2004年 | 20篇 |
2003年 | 22篇 |
2002年 | 19篇 |
2001年 | 22篇 |
2000年 | 25篇 |
1999年 | 16篇 |
1998年 | 14篇 |
1997年 | 8篇 |
1996年 | 12篇 |
1995年 | 8篇 |
1994年 | 10篇 |
1993年 | 9篇 |
1992年 | 22篇 |
1991年 | 23篇 |
1990年 | 13篇 |
1989年 | 21篇 |
1988年 | 19篇 |
1987年 | 9篇 |
1986年 | 23篇 |
1985年 | 14篇 |
1984年 | 14篇 |
1983年 | 11篇 |
1982年 | 15篇 |
1981年 | 12篇 |
1980年 | 11篇 |
1979年 | 9篇 |
1978年 | 10篇 |
1977年 | 10篇 |
1976年 | 12篇 |
1972年 | 6篇 |
1971年 | 6篇 |
1970年 | 7篇 |
1969年 | 6篇 |
1968年 | 9篇 |
排序方式: 共有841条查询结果,搜索用时 15 毫秒
121.
122.
Giuliano Bandoli Ulderico Mazzi Bruce E. Wilcox Silvia Jurisson Edward Deutsch 《Inorganica chimica acta》1984,95(4):217-223
Five-coordinate technetium(V) complexes of the form TcO(L)Cl where L is one of the two tridentate Schiff base ligands N-(2-oxidophenyl)salicylideneiminate or N-(2-mercaptophenyl)salicylideneiminate have been synthesized and characterized. These neutral complexes precipitate from methanol upon reaction of the Schiff base ligand with TcOCl4?. A single crystal X-ray structure determination shows that the chloro [[N-(2-oxidophenyl)salicylideneiminato](2?)-N,O,O′]oxotechnetium(V) complex, [TcO(C13H9NO2)Cl], formula weight 362, has a distorted square pyramidal coordination geometry with the oxo ligand in the axial position. The steric requirements of the oxo group cause the Tc atom to be displayed 0.67 Å out of the mean equatorial plane of the other four donor atoms. This complex crystallizes in the monoclinic space group P21/a with a = 13.423(6) Å, b = 12.570(5) Å, c = 7.769(3) Å, β = 106.53(5)°, V = 1256.7(9) Å3, and Z = 4. The structure has been refined to R = 0.047 for 1775 observed reflections. 相似文献
123.
124.
Soluble Antigens of Vaccinia-infected Mammalian Cells: III. Relation of “Early” and “Late” Proteins to Virus Structure 总被引:1,自引:1,他引:0
下载免费PDF全文
![点击此处可从《Journal of virology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The structural proteins of vaccinia virus can be divided into two classes on the basis of their times of synthesis in the infected cell. The production of one of these classes of proteins begins prior to the onset of viral deoxyribonucleic acid (DNA) replication. These are referred to as "early" proteins. Synthesis of the second class of structural proteins follows the onset of viral DNA replication; hence, the term "late" proteins for this class. We are able, by immunological procedures, to identify three "early" virus-structural proteins. These materials, when incorporated into virions, appear to be associated with the "core" of the virion and do not elicit production of virus-neutralizing antibody. It would seem, therefore, that those virus-structural proteins synthesized early in the course of infection act as internal components of the virion. The "late" proteins may be subdivided into two groups on the basis of certain physical properties and molecular weight differences. The first of these groups, comprised of at least two proteins, corresponds to the classical LS antigens and elicits production of neutralizing antibodies. These proteins, when incorporated into virions, are found only in the outer ("coat") fraction of the virion. The second group of "late" antigens, also comprised of two proteins, termed the G antigens, do not elicit synthesis of neutralizing antibody. One of these proteins is associated with the virus "core"; the other is found in the "coat" fraction of the virion and appears to occupy an intermediary, subsurface position. Procedures suitable for the isolation of the G antigens are described, in addition to the partial characterization of these antigens. 相似文献
125.
The staining schedule was developed for a study of the mycorrhizae of red pine, Pinus resinosa Ait. From 70% alcohol, sections are stained in a saturated solution of chlorazol black E in 70% alcohol, 10-30 min; free dye removed by washing in 95% alcohol; stained 18-24 hr in Pianese III-b; rinsed in 95% alcohol, acidified by the addition of 2 ml of saturated aqueous picric acid per 100 ml, 3-4 changes or until the last change is pale yellow or light green; and rinsing in 95% alcohol to remove the acid. If the acid fuchsin is too intense, a cautious differentiation with 95% alcohol containing 1-3% of a 0.1 N solution of NaOH is made. If too much chlorazol black is removed, the effect can be compensated by overstaining with this dye at the beginning of the process. Sections are dehydrated, cleared, and covered in the usual manner. This stain has applications to plant tissues generally, and is particularly effective for meristematic tissues. It shows details of cytoplasmic structures and gives sharp delineation of primary cell walls. 相似文献
126.
Building strong relationships between conservation genetics and primary industry leads to mutually beneficial genomic advances
下载免费PDF全文
![点击此处可从《Molecular ecology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Stephanie J. Galla Thomas R. Buckley Rob Elshire Marie L. Hale Michael Knapp John McCallum Roger Moraga Anna W. Santure Phillip Wilcox Tammy E. Steeves 《Molecular ecology》2016,25(21):5267-5281
Several reviews in the past decade have heralded the benefits of embracing high‐throughput sequencing technologies to inform conservation policy and the management of threatened species, but few have offered practical advice on how to expedite the transition from conservation genetics to conservation genomics. Here, we argue that an effective and efficient way to navigate this transition is to capitalize on emerging synergies between conservation genetics and primary industry (e.g., agriculture, fisheries, forestry and horticulture). Here, we demonstrate how building strong relationships between conservation geneticists and primary industry scientists is leading to mutually‐beneficial outcomes for both disciplines. Based on our collective experience as collaborative New Zealand‐based scientists, we also provide insight for forging these cross‐sector relationships. 相似文献
127.
Sampling large geographic areas for rare species using environmental DNA: a study of bull trout Salvelinus confluentus occupancy in western Montana 总被引:1,自引:0,他引:1
下载免费PDF全文
![点击此处可从《Journal of fish biology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
K. S. McKelvey M. K. Young W. L. Knotek K. J. Carim T. M. Wilcox T. M. Padgett‐Stewart M. K. Schwartz 《Journal of fish biology》2016,88(3):1215-1222
This study tested the efficacy of environmental DNA (eDNA) sampling to delineate the distribution of bull trout Salvelinus confluentus in headwater streams in western Montana, U.S.A. Surveys proved fast, reliable and sensitive: 124 samples were collected across five basins by a single crew in c. 8 days. Results were largely consistent with past electrofishing, but, in a basin where S. confluentus were known to be scarce, eDNA samples indicated that S. confluentus were more broadly distributed than previously thought. 相似文献
128.
129.
Rand R. Wilcox 《Biometrical journal. Biometrische Zeitschrift》2000,42(3):335-347
The paper suggests an exploratory method for studying curvature, within the context of robust regression, using an analog of the approached developed by Doksum and Samarov (1995). The strategy begins by approximating the regression surface using a proposed generalization of the so‐called running interval smoother. The generalization consists of estimating the span via arobust measure of scale associated with the residuals. This approximation can then be used to measure linearity using a robust analog of a measure considered by Doksum and Samarov. The results are illustrated with data from a study on predicting reading ability. 相似文献
130.
Worthington Wilmer J Elkin C Wilcox C Murray L Niejalke D Possingham H 《Molecular ecology》2008,17(16):3733-3751
Many organisms occupy heterogeneous landscapes that contain both barriers to movement as well as corridors that facilitate dispersal. The extent to which such features determine population connectivity will depend on the mechanisms utilized by organisms to disperse. Here we examined the interaction between landscape structure and dispersal in the endemic aquatic snail, Fonscochlea accepta , in the fragmented artesian spring ecosystem of arid central Australia. We used frequentist and Bayesian analyses of microsatellite data to identify population structure and immigration for 1130 snails sampled from 50 springs across an entire spring complex. We introduce a modified isolation-by-distance analysis to test hypotheses about how populations are clustered and to distinguish the most likely dispersal pathways within and between those clusters. Highly significant differences in F ST values and significant isolation-by-distance patterns were detected among springs across the entire complex, while Bayesian assignment tests revealed the presence of two hierarchical levels of spring clustering. Clusters were defined by the spatial aggregation of springs, dynamic aquatic habitat connections between springs and the ecology of the snails. Bayesian immigrant identification and our modified isolation-by-distance analysis revealed that dispersal occurs at two geographical scales via two very different mechanisms. Short range dispersal (usually ≤ 300 m) occurs via active movement facilitated by aquatic connections among springs while long-range dispersal (≥ 3 km) is likely facilitated by an animal vector (phoresy). These results underline the importance of both dispersal mode and landscape structure in influencing connectivity rates and patterns among populations. 相似文献