全文获取类型
收费全文 | 3233篇 |
免费 | 280篇 |
专业分类
3513篇 |
出版年
2023年 | 14篇 |
2022年 | 35篇 |
2021年 | 65篇 |
2020年 | 43篇 |
2019年 | 41篇 |
2018年 | 49篇 |
2017年 | 40篇 |
2016年 | 80篇 |
2015年 | 159篇 |
2014年 | 188篇 |
2013年 | 211篇 |
2012年 | 273篇 |
2011年 | 207篇 |
2010年 | 160篇 |
2009年 | 128篇 |
2008年 | 156篇 |
2007年 | 168篇 |
2006年 | 160篇 |
2005年 | 122篇 |
2004年 | 136篇 |
2003年 | 129篇 |
2002年 | 127篇 |
2001年 | 32篇 |
2000年 | 33篇 |
1999年 | 41篇 |
1998年 | 42篇 |
1997年 | 28篇 |
1996年 | 28篇 |
1995年 | 23篇 |
1994年 | 26篇 |
1993年 | 23篇 |
1992年 | 24篇 |
1991年 | 20篇 |
1990年 | 22篇 |
1989年 | 30篇 |
1988年 | 18篇 |
1987年 | 17篇 |
1986年 | 14篇 |
1985年 | 23篇 |
1984年 | 28篇 |
1983年 | 18篇 |
1982年 | 16篇 |
1981年 | 22篇 |
1980年 | 19篇 |
1979年 | 15篇 |
1978年 | 17篇 |
1977年 | 12篇 |
1976年 | 20篇 |
1974年 | 14篇 |
1971年 | 12篇 |
排序方式: 共有3513条查询结果,搜索用时 15 毫秒
51.
Wilton Marion Krogman 《American journal of physical anthropology》1976,45(3):531-537
The rise of two sub-specialties in Physical Anthropology traces back to the Anatomy Departments of Schools of Medicine in Germany and France during the nineteenth century. The study of human diversity in bones and bodies was largely by medically-trained anatomists. There developed Medical Anthropology and Dental Anthropology, employing osteometry and craniometry on the skeleton, somatometry and cephalometry on the living body. As a result cross-sectional studies gave way to longitudinal studies and X-ray techniques were added to purely mensurational procedures. In Medical Anthropology the specialties most directly concerned are pediatrics, plastic surgery, endocrinology, and orthopaedics. In Dental Anthropology the specialties most directly concerned are pedodontics, orthodontics, oral surgery, and prosthodontics. The contributions of Physical Anthropology to each is discussed. 相似文献
52.
53.
In order to obtain information about the conformational features of a 2′-O-methylated polyribonucleotide at the nearest neighbor level, a detailed nuclear magnetic resonance study of AmpA was undertaken. AmpA was isolated from alkali hydrolysates of yeast RNA, and proton spectra were recorded at 100 MHz in the Fourier transform mode in D2O solutions, 0.01 M, pH 5.4 and 1.5 at 25°C. 31P spectra were recorded at 40.48 MHz. Complete, accurate sets of nmr parameters derived for each nucleotidyl unit by simulation iteration methods. The nmr data were translated into conformational parameters for all the bonds using procedures developed in earlier studies from these laboratories. It is shown that AmpA exists in aqueous solution with a flexible molecular framework, which shows preferences for certain orientations. The ribose rings exist as a 2E ? 3E equilibrium with the —pA ribose showing a bias for the 3E pucker. The C(4′)—C(5′) bonds of both nucleotidyl units show significant preference (75–80%) to exist in gg conformation. The dominant conformer (80%) about C(5′)—O(5′) of the 5′-nucleotidyl unit is g′g′. Even though an unambiguous determination of the orientation of the 3′-phosphate group cannot be made, tentative evidence shows that it preferentially occupies g+ domains [O(3′)—P trans to C(3′)—C(2′)] in which the H(3′) —C(3′)—O(3′)—P(3′) dihedral angle is about 31°. There is reasonable evidence that the 2′-O-methyl preferentially occupies the domain in which the O(2′)—CH3 bond is trans to C(2′)—C(1′). Lowering of pH to 1.5, which results in protonation of both the adenine moieties, causes destacking of AmpA. Such destacking is accompanied by small, but real, perturbations in the conformations about most of the bonds in the backbone. A detailed comparison of the solution conformations of ApA and AmpA clearly shows that 2′-O-methylation strongly influences the conformational preference about the C(3′)—O(3′) bond of the 3′-nucleotidyl unit, in addition to inducing small changes in the overall ribophosphate backbone conformational equilibria. The effect of 2′-O-methylation is such that the C(3′)—O(3′) is forced to occupy preferentially the g+ domain rather than the normally preferred g? domain [O(3′)—P trans to C(3′)—C(4′)] in ApA. The data on ApA and AmpA further reveal that the extent of stacking interaction is less in AmpA compared to ApA. It is suggested that stacked species of AmpA exist as right-handed stacks where the magnitude of ω and ω′ about O(5′)—P and P—O(3′) is about 290°. The reason for the lesser degree of stacking in AmpA compared to ApA is intramolecular interaction between 2′-O-methyl and the flexible O(3′)—P—O(5′) bridge, the interaction causing some perturbation in the magnitudes of ω/ω′, causing destacking. The destacking will lead to an increase in χCN by a few degrees, causing an increase in 2E populations; the latter in turn will shift the 3′ phosphate group from g? to g+ domains. In short, a coupled series of conformational events is envisioned at the onset of destacking, made feasible by the interaction between the 2′-O-methyl group and the swivel O(3′)—P—O(5′) bridge. 相似文献
54.
Malory Randon Christophe Bonenfant Jacques Michallet Thierry Chevrier Carole Toïgo Jean-Michel Gaillard Marion Valeix 《Population Ecology》2020,62(2):244-257
In a context of changing carnivore populations worldwide, it is crucial to understand the consequences of these changes for prey populations. The recolonization by wolves of the French Vercors mountain range and the long-term monitoring (2001–2017) of roe deer in this area provided a unique opportunity to assess the effects of wolves on this prey. Roe deer was the main prey of wolves in the west Vercors mountain range during this recolonization. We compared roe deer abundance and fawn body mass in two contrasted areas of a wolf pack territory: a central area (core of the territory characterized by an intense use by wolves) and a peripheral area (used more occasionally). Roe deer population growth rates were lower in the central area between 2001 and 2006, resulting in a decline in roe deer abundance. Roe deer abundance substantially dropped in the two study areas after an extremely severe winter but the abundance of roe deer in the central area facing with wolves was slower to recover and remained at lower abundance levels for 6 years. Fawn body mass was consistently lower in the central area, varied similarly as roe deer abundance, and was not influenced by weather conditions or red deer population abundance. Altogether, the effects of wolves on roe deer in the central area occurred during a 10-year period following the establishment of wolves, through the interplay between wolf predation (before wolves started preying on red deer), harsh winter conditions and possibly naivety of prey to this recolonizing predator. 相似文献
55.
Kvin Magne Shengbin Liu Sophie Massot Marion Dalmais Halima Morin Richard Sibout Abdelhafid Bendahmane Pascal Ratet 《The Plant journal : for cell and molecular biology》2020,103(2):645-659
In cultivated grasses, tillering, spike architecture and seed shattering represent major agronomical traits. In barley, maize and rice, the NOOT‐BOP‐COCH‐LIKE (NBCL) genes play important roles in development, especially in ligule development, tillering and flower identity. However, compared with dicots, the role of grass NBCL genes is underinvestigated. To better understand the role of grass NBCLs and to overcome any effects of domestication that might conceal their original functions, we studied TILLING nbcl mutants in the non‐domesticated grass Brachypodium distachyon. In B. distachyon, the NBCL genes BdUNICULME4 (CUL4) and BdLAXATUM‐A (LAXA) are orthologous, respectively, to the barley HvUniculme4 and HvLaxatum‐a, to the maize Zmtassels replace upper ears1 and Zmtassels replace upper ears2 and to the rice OsBLADE‐ON‐PETIOLE1 and OsBLADE‐ON‐PETIOLE2/3. In B. distachyon, our reverse genetics study shows that CUL4 is not essential for the establishment of the blade–sheath boundary but is necessary for the development of the ligule and auricles. We report that CUL4 also exerts a positive role in tillering and a negative role in spikelet meristem activity. On the other hand, we demonstrate that LAXA plays a negative role in tillering, positively participates in spikelet development and contributes to the control of floral organ number and identity. In this work, we functionally characterized two new NBCL genes in a context of non‐domesticated grass and highlighted original roles for grass NBCL genes that are related to important agronomical traits. 相似文献
56.
Fanny Ruhland Marion Moulin Marina Choppin Joël Meunier Christophe Lucas 《Ecology and evolution》2020,10(12):5892-5898
In insect societies, the presence of reproductives or eggs has been shown to shape several biological traits in the colony members. Social interactions are one of these traits that involve modification of the communication system of the entire colony. Many studies described the role of chemical compounds and dominance behaviors in the presence of reproductive but vibratory behaviors received very few investigations. Yet, vibratory behaviors are ideal candidates, particularly for subterranean species like termites, as they could be quickly transmitted through the substrate and could be very diversified (origin, modulation). Here, we investigated whether the presence of reproductives/eggs affects the vibratory behavior (body‐shaking) of workers in the subterranean termite Reticulitermes flavipes. Our results reveal that the presence of reproductives or eggs triggers an increase of workers' body‐shaking, independent of their colony of origin after 24 hr. We hypothesize that vibratory communication could be used to transfer information about the presence of reproductives and eggs to the entire colony, suggesting that vibratory behaviors could serve as an important yet neglected mediator of social regulation. 相似文献
57.
Tserendorj Gegeensuvd Marinova Elena Lechterbeck Jutta Behling Hermann Wick Lucia Fischer Elske Sillmann Marion Märkle Tanja Rösch Manfred 《Vegetation History and Archaeobotany》2021,30(1):35-46
Vegetation History and Archaeobotany - A system of farming with an alternation of land use between being cultivated or left fallow as grassland (Feldgraswirtschaft) developed in southwestern... 相似文献
58.
Beatris Mastelic Nathalie Garçon Giuseppe Del Giudice Hana Golding Marion Gruber Pieter Neels Bernard Fritzell 《Biologicals》2013,41(6):458-468
Vaccination represents one of the greatest public health triumphs; in part due to the effect of adjuvants that have been included in vaccine preparations to boost the immune responses through different mechanisms. Although a variety of novel adjuvants have been under development, only a limited number have been approved by regulatory authorities for human vaccines. This report reflects the conclusions of a group of scientists from academia, regulatory agencies and industry who attended a conference on the current state of the art in the adjuvant field. Held at the U.S. Pharmacopeial Convention (USP) in Rockville, Maryland, USA, from 18 to 19 April 2013 and organized by the International Association for Biologicals (IABS), the conference focused particularly on the future development of effective adjuvants and adjuvanted vaccines and on overcoming major hurdles, such as safety and immunogenicity assessment, as well as regulatory scrutiny. More information on the conference output can be found on the IABS website, http://www.iabs.org/. 相似文献
59.
60.
Jennifer Dieppedale Gael Gesbert Elodie Ramond Cerina Chhuon Iharilalao Dubail Marion Dupuis Ida Chiara Guerrera Alain Charbit 《Molecular & cellular proteomics : MCP》2013,12(8):2278-2292
Francisella tularensis is a highly infectious bacterium causing the zoonotic disease tularemia. In vivo, this facultative intracellular bacterium survives and replicates mainly in the cytoplasm of infected cells. We have recently identified a genetic locus, designated moxR that is important for stress resistance and intramacrophage survival of F. tularensis. In the present work, we used tandem affinity purification coupled to mass spectrometry to identify in vivo interacting partners of three proteins encoded by this locus: the MoxR-like ATPase (FTL_0200), and two proteins containing motifs predicted to be involved in protein–protein interactions, bearing von Willebrand A (FTL_0201) and tetratricopeptide (FTL_0205) motifs. The three proteins were designated here for simplification, MoxR, VWA1, and TPR1, respectively. MoxR interacted with 31 proteins, including various enzymes. VWA1 interacted with fewer proteins, but these included the E2 component of 2-oxoglutarate dehydrogenase and TPR1. The protein TPR1 interacted with one hundred proteins, including the E1 and E2 subunits of both oxoglutarate and pyruvate dehydrogenase enzyme complexes, and their common E3 subunit. Remarkably, chromosomal deletion of either moxR or tpr1 impaired pyruvate dehydrogenase and oxoglutarate dehydrogenase activities, supporting the hypothesis of a functional role for the interaction of MoxR and TPR1 with these complexes. Altogether, this work highlights possible links between stress resistance and metabolism in F. tularensis virulence.Francisella tularensis is responsible for the disease tularamia in a large number of animal species. This highly infectious bacterial pathogen can be transmitted to humans in numerous ways (1, 2, 3), including direct contact with sick animals, inhalation, ingestion of contaminated water or food, or by bites from ticks, mosquitoes, or flies. Four different subspecies (subsp.) of F. tularensis that differ in virulence and geographic distribution exist, designated subsp. tularensis (type A), subsp. holarctica (type B), subsp. Novicida, and subsp. mediasiatica, respectively. F. tularensis subsp. tularensis is the most virulent subspecies causing a severe disease in humans, whereas F. tularensis subsp. holarctica causes a similar disease but of less severity (4). Because of its high infectivity and lethality, F. tularensis is considered a potential bioterrorism agent (5).F. tularensis is able to survive and to replicate in the cytoplasm of a variety of infected cells, including macrophages. To resist this stressful environment, the bacterium must have developed stress resistance mechanisms, most of which are not yet well characterized. We recently reported the identification of a novel genetic locus that is important for stress resistance and intracellular survival of F. tularensis (6). This locus was designated moxR because the first gene FTL_0200, encodes a protein belonging to the AAA+ ATPase of the MoxR family ((7) and references therein). The data obtained in that first study had led us to suggest that the F. tularensis MoxR-like protein might constitute, in combination with other proteins of the locus, a chaperone complex contributing to F. tularensis pathogenesis.To further validate this hypothesis and expand our initial observations, we here decided to perform tandem affinity purification (TAP),1 using a dual affinity tag approach coupled to mass spectroscopy analyses (8), to identify proteins interacting in vivo with three proteins encoded by the proximal portion of the moxR locus. For this, we chose as baits: the MoxR-like protein (FTL_0200) and two proteins bearing distinct motifs possibly involved in protein–protein interactions, FTL_0201 (Von Willebrand Factor Type A domain, or VWA) and FTL_0205 (tetratrichopeptide repeat or TPR). The three proteins were designated here for simplification, MoxR, VWA1, and TPR1; and the corresponding genes moxR, vwa1, and tpr1, respectively.VWA domains are present in all three kingdoms of life. They consist of a β-sheet sandwiched by multiple α helices. Frequently, VWA domain-containing proteins function in multiprotein complexes (9). TPR typically contain 34 amino acids. Many three-dimensional structures of TPR domains have been solved, revealing amphipathic helical structures (10). TPR-containing proteins are also found in all kingdoms of life. They can be involved in a variety of functions, and generally mediate protein–protein interactions. In the past few years, several TPR-related proteins have been shown to be involved in virulence mechanisms in pathogenic bacteria ((11) and references therein).Our proteomic approach allowed us to identify a series of protein interactants for each of the three moxR-encoded proteins. Remarkably, the protein TPR1 interacted with all the subunits of the pyruvate dehydrogenase (PDH) and 2-oxoglutarate dehydrogenase (OGDH) complexes. Furthermore, inactivation of tpr1 also severely impaired the activities of these two enzymes. Inactivation of tpr1 affected bacterial resistance to several stresses (and in particular oxidative stress), intramacrophagic bacterial multiplication and bacterial virulence in the mouse model. Functional implications and possible relationship between bacterial metabolism, stress defense, and bacterial virulence are discussed. 相似文献