全文获取类型
收费全文 | 30676篇 |
免费 | 15905篇 |
国内免费 | 2篇 |
专业分类
46583篇 |
出版年
2023年 | 47篇 |
2022年 | 159篇 |
2021年 | 515篇 |
2020年 | 2240篇 |
2019年 | 3786篇 |
2018年 | 3900篇 |
2017年 | 4162篇 |
2016年 | 4210篇 |
2015年 | 4217篇 |
2014年 | 3908篇 |
2013年 | 4371篇 |
2012年 | 2082篇 |
2011年 | 1808篇 |
2010年 | 3212篇 |
2009年 | 1979篇 |
2008年 | 933篇 |
2007年 | 516篇 |
2006年 | 465篇 |
2005年 | 484篇 |
2004年 | 434篇 |
2003年 | 430篇 |
2002年 | 430篇 |
2001年 | 357篇 |
2000年 | 278篇 |
1999年 | 220篇 |
1998年 | 72篇 |
1997年 | 59篇 |
1996年 | 63篇 |
1995年 | 52篇 |
1994年 | 37篇 |
1993年 | 33篇 |
1992年 | 60篇 |
1991年 | 61篇 |
1990年 | 58篇 |
1989年 | 66篇 |
1988年 | 48篇 |
1987年 | 51篇 |
1986年 | 45篇 |
1985年 | 44篇 |
1984年 | 42篇 |
1983年 | 51篇 |
1982年 | 37篇 |
1980年 | 29篇 |
1979年 | 42篇 |
1977年 | 35篇 |
1975年 | 27篇 |
1974年 | 28篇 |
1972年 | 35篇 |
1968年 | 26篇 |
1967年 | 23篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
211.
Effects of adults body size and larvae diet on the fecundity and percent fertility of eggs laid by Xylotrechus arvicola (Coleoptera: Cerambycidae) females,insect pest in Spanish vineyards 下载免费PDF全文
Álvaro Rodríguez‐González Horacio J. Peláez Óscar González‐López Sara Mayo Pedro A. Casquero 《Entomological Research》2018,48(2):83-91
Xylotrechus arvicola is a pest of grape in some vine‐producing regions of the Iberian Peninsula. Biological parameters and relationships (fecundity and percent fertility of eggs in relationship to body size) of females obtained in the laboratory and captured in vineyards were studied. In laboratory conditions, the mean developmental time of larvae ranged from 384 to 392 days and pupal stage varied between 12 to 14 days. Body size (BS) of X. arvicola females was significantly bigger than males. Fecundity was greater in the laboratory (147 eggs) than in the field (50 eggs) females, but the percent fertility of the laboratory eggs was lower (16 eggs). Laboratory females showed a bigger relationship between the production of eggs and BS than females captured in vineyards. Wild females (PDO Ribera del Duero and Tierra de León) had a positive relationship between the percent fertility of eggs and the BS. No correlation between the percent fertility of eggs and the BS was displayed by females captured in PDO Toro, but these females had a higher percent fertility (53 eggs) than the others PDO's. These biological parameters and relationships studied suggest that the artificial diet may lack certain essential nutrients that vine varieties can provide that favor the fertility of eggs. This explains why wild females have the potential to become a problem pest in the Tempranillo grape variety, with bilateral cordon and bush vines training systems that have the highest incidence of this cerambycid. 相似文献
212.
Tai‐Wen Lin Chi‐Chih Chen Shu‐Mei Wu Yu‐Ching Chang Yi‐Chuan Li Yu‐Wang Su Chwan‐Deng Hsiao Hsin‐Yang Chang 《The Plant journal : for cell and molecular biology》2019,99(1):128-143
In mammals and yeast, tail‐anchored (TA) membrane proteins destined for the post‐translational pathway are safely delivered to the endoplasmic reticulum (ER) membrane by a well‐known targeting factor, TRC40/Get3. In contrast, the underlying mechanism for translocation of TA proteins in plants remains obscure. How this unique eukaryotic membrane‐trafficking system correctly distinguishes different subsets of TA proteins destined for various organelles, including mitochondria, chloroplasts and the ER, is a key question of long standing. Here, we present crystal structures of algal ArsA1 (the Get3 homolog) in a distinct nucleotide‐free open state and bound to adenylyl‐imidodiphosphate. This approximately 80‐kDa protein possesses a monomeric architecture, with two ATPase domains in a single polypeptide chain. It is capable of binding chloroplast (TOC34 and TOC159) and mitochondrial (TOM7) TA proteins based on features of its transmembrane domain as well as the regions immediately before and after the transmembrane domain. Several helices located above the TA‐binding groove comprise the interlocking hook‐like motif implicated by mutational analyses in TA substrate recognition. Our data provide insights into the molecular basis of the highly specific selectivity of interactions of algal ArsA1 with the correct sets of TA substrates before membrane targeting in plant cells. 相似文献
213.
214.
215.
Molecular basis of the differential interaction with lithium of glycine transporters GLYT1 and GLYT2
Pérez-Siles G Morreale A Leo-Macías A Pita G Ortíz AR Aragón C López-Corcuera B 《Journal of neurochemistry》2011,118(2):195-204
Glycine synaptic levels are controlled by glycine transporters (GLYTs) catalyzing Na(+)/Cl(-)/glycine cotransport. GLYT1 displays a 2:1 :1 stoichiometry and is the main regulator of extracellular glycine concentrations. The neuronal GLYT2, with higher sodium coupling (3:1 :1), supplies glycine to the pre-synaptic terminal to refill synaptic vesicles. In this work, using structural homology modelling and molecular dynamics simulations of GLYTs, we predict the conservation of the two sodium sites present in the template (leucine transporter from Aquifex aeolicus), and confirm its use by mutagenesis and functional analysis. GLYTs Na1 and Na2 sites show differential cation selectivity, as inferred from the action of lithium, a non-transport-supporting ion, on Na(+)-site mutants. GLYTs lithium responses were unchanged in Na1-site mutants, but abolished or inverted in mutants of Na2 site, which binds lithium in the presence of low sodium concentrations and therefore, controls lithium responses. Here, we report, for the first time, that lithium exerts opposite actions on GLYTs isoforms. Glycine transport by GLYT1 is inhibited by lithium whereas GLYT2 transport is stimulated, and this effect is more evident at increased glycine concentrations. In contrast to GLYT1, high and low affinity lithium-binding processes were detected in GLYT2. 相似文献
216.
The membrane topology of Escherichia coli FtsW, a 46-kDa essential protein, was analyzed using a set of 28 ftsW-alkaline phosphatase (ftsW-phoA) and nine ftsW-beta-lactamase (ftsW-bla) gene fusions obtained by in vivo and in vitro methods. The alkaline phosphatase activities or resistance pattern of cells expressing the FtsW-PhoA or FtsW-Bla fusions confirmed only eight out of 10 transmembrane segments predicted by computational methods. After comparison with the recent topology of Streptococcus pneumoniae FtsW, we could identify all the fusions in absolute agreement with the predicted model: N-terminal and C-terminal ends in the cytoplasm, 10 transmembrane segments and one large loop of 67 amino acids (E240-E306) located in the periplasm. 相似文献
217.
Globalization has changed the habitats of various species, resulting in harmful pest invasion. Among these pests, Metcalfa pruinosa has caused worldwide economic and hygienic damage in both urban and agricultural/forested areas. It has been reported that prediction of pest distribution is key to the management of pest prevention. Hence, this study aimed to predict the potential geographic distribution of M. pruinosa under the current climate and under a climate change scenario. CLIMEX, modeling software that analyzes the habitat suitability of a target species based on comprehensive climatic and physiological data, was used mainly to establish a map of predictive distribution of M. pruinosa at present and in the future. Based on our simulations, we predict that M. pruinosa will tend to extend its distribution northward in North America and Europe. We conclude that climate change could result in M. pruinosa invasion in a northward direction, suggesting the need for a thorough system of control and prevention. 相似文献
218.
219.
Development of simple sequence repeat (SSR) markers for the assessment of gene flow between sea beet (Beta vulgaris ssp. maritima) populations 总被引:1,自引:0,他引:1
A. N. Cureton M. J. Burns B. V. Ford‐Lloyd H. J. Newbury 《Molecular ecology resources》2002,2(4):402-403
Molecular markers can be used to estimate gene flow indirectly by monitoring the relative frequency of alleles in adjacent populations. Sea beet (Beta vulgaris ssp. maritima) is a wild plant species found along the coastlines of many European countries and is closely related to cultivated beets. A set of six simple sequence repeat (SSR) markers that are polymorphic in UK populations have been developed for sea beet to assess the problems of indirect measurement of gene flow in these populations. 相似文献
220.