全文获取类型
收费全文 | 4253篇 |
免费 | 300篇 |
出版年
2024年 | 4篇 |
2023年 | 27篇 |
2022年 | 70篇 |
2021年 | 125篇 |
2020年 | 95篇 |
2019年 | 88篇 |
2018年 | 131篇 |
2017年 | 112篇 |
2016年 | 169篇 |
2015年 | 247篇 |
2014年 | 281篇 |
2013年 | 284篇 |
2012年 | 342篇 |
2011年 | 351篇 |
2010年 | 252篇 |
2009年 | 198篇 |
2008年 | 241篇 |
2007年 | 233篇 |
2006年 | 211篇 |
2005年 | 186篇 |
2004年 | 144篇 |
2003年 | 139篇 |
2002年 | 113篇 |
2001年 | 53篇 |
2000年 | 47篇 |
1999年 | 52篇 |
1998年 | 29篇 |
1997年 | 26篇 |
1996年 | 16篇 |
1995年 | 12篇 |
1994年 | 17篇 |
1993年 | 10篇 |
1992年 | 24篇 |
1991年 | 25篇 |
1990年 | 21篇 |
1989年 | 20篇 |
1988年 | 23篇 |
1987年 | 16篇 |
1986年 | 11篇 |
1985年 | 19篇 |
1984年 | 11篇 |
1983年 | 12篇 |
1982年 | 8篇 |
1981年 | 8篇 |
1980年 | 13篇 |
1978年 | 4篇 |
1973年 | 5篇 |
1972年 | 3篇 |
1968年 | 3篇 |
1967年 | 3篇 |
排序方式: 共有4553条查询结果,搜索用时 31 毫秒
881.
The genus Foenobethylus Kieffer from Southeastern Asia is studied, and seven species are recognized. Four previously described species are analyzed and had their known distribution broadened: F. gracilis Kieffer, F. elongatus Várkonyi and Polaszek, F. emiliacasellae Várkonyi and Polaszek, and F. thomascokeri Várkonyi and Polaszek. Two new species are described and illustrated, F. sharkeyi sp. nov. is characterized by having the metatrochanter without spine and the metafemur with acute proximal spine; and F. pyramidis sp. nov. is characterized by having the metatrochanter with one spine and the metafemur with two spines. The following new combination is established: F. thaianus comb. nov. from Parascleroderma because it has the metafemur with two proximal spines. An update world key to the species of genus is provided. 相似文献
882.
Squamates are found in a wide range of habitats and show a corresponding diversity of morphologies that can often be correlated with locomotor mode. The evolution of a snake‐like body form, frequently associated with fossoriality, from a typical lacertiform morphology involves changes in the morphology of vertebrae, girdles, and limbs; the changes are mainly manifested by the reduction or loss of limbs and body elongation. In this study, we describe the axial and appendicular skeletons of six closely related gymnophthalmid species. Three of them show a lizard‐like morphology, with a four‐digit forelimb and a five‐digit hindlimb, and the other three show a snake‐like morphology associated with a burrowing habit, with reduced limbs and a longer body in comparison to the former three species. We show that vertebral morphology is similar among the six species, with the differences being accounted for by an increase in the number of vertebrae and by the structural reduction of girdles and limbs in the snake‐like species. Skeletal morphology provides valuable information on locomotion type, physiology, diet, and other biological features. The burrowing morphology usually involves accentuated reduction of girdle and limb elements, reflecting an undulating type of locomotion in which the limbs play little or no role in propelling the body; in contrast, well‐developed limbs and girdles indicate a greater reliance on the limbs for body propulsion. Limb reduction is frequent among vertebrates, but many different phenotypes are found in species exhibiting some kind of reduction, indicating that different mechanisms and evolutionary pressures may be involved in generating the diverse morphologies. J. Morphol. 274:845–858, 2013. © 2013 Wiley Periodicals, Inc. 相似文献
883.
884.
885.
Juliana S. Ruas Edilene S. Siqueira-Santos Ignacio Amigo Erika Rodrigues-Silva Alicia J. Kowaltowski Roger F. Castilho 《PloS one》2016,11(3)
The maximal capacity of the mitochondrial electron transport system (ETS) in intact cells is frequently estimated by promoting protonophore-induced maximal oxygen consumption preceded by inhibition of oxidative phosphorylation by oligomycin. In the present study, human glioma (T98G and U-87MG) and prostate cancer (PC-3) cells were titrated with different concentrations of the protonophore CCCP to induce maximal oxygen consumption rate (OCR) within respirometers in a conventional growth medium. The results demonstrate that the presence of oligomycin or its A-isomer leads to underestimation of maximal ETS capacity. In the presence of oligomycin, the spare respiratory capacity (SRC), i.e., the difference between the maximal and basal cellular OCR, was underestimated by 25 to 45%. The inhibitory effect of oligomycin on SRC was more pronounced in T98G cells and was observed in both suspended and attached cells. Underestimation of SRC also occurred when oxidative phosphorylation was fully inhibited by the ATP synthase inhibitor citreoviridin. Further experiments indicated that oligomycin cannot be replaced by the adenine nucleotide translocase inhibitors bongkrekic acid or carboxyatractyloside because, although these compounds have effects in permeabilized cells, they do not inhibit oxidative phosphorylation in intact cells. We replaced CCCP by FCCP, another potent protonophore and similar results were observed. Lower maximal OCR and SRC values were obtained with the weaker protonophore 2,4-dinitrophenol, and these parameters were not affected by the presence of oligomycin. In permeabilized cells or isolated brain mitochondria incubated with respiratory substrates, only a minor inhibitory effect of oligomycin on CCCP-induced maximal OCR was observed. We conclude that unless a previously validated protocol is employed, maximal ETS capacity in intact cells should be estimated without oligomycin. The inhibitory effect of an ATP synthase blocker on potent protonophore-induced maximal OCR may be associated with impaired metabolism of mitochondrial respiratory substrates. 相似文献
886.
Stephen E. P. Smith Anya T. Bida Tessa R. Davis Hugues Sicotte Steven E. Patterson Diana Gil Adam G. Schrum 《PloS one》2012,7(9)
Protein-protein interactions (PPI) mediate the formation of intermolecular networks that control biological signaling. For this reason, PPIs are of outstanding interest in pharmacology, as they display high specificity and may represent a vast pool of potentially druggable targets. However, the study of physiologic PPIs can be limited by conventional assays that often have large sample requirements and relatively low sensitivity. Here, we build on a novel method, immunoprecipitation detected by flow cytometry (IP-FCM), to assess PPI modulation during either signal transduction or pharmacologic inhibition by two different classes of small-molecule compounds. First, we showed that IP-FCM can detect statistically significant differences in samples possessing a defined PPI change as low as 10%. This sensitivity allowed IP-FCM to detect a PPI that increases transiently during T cell signaling, the antigen-inducible interaction between ZAP70 and the T cell antigen receptor (TCR)/CD3 complex. In contrast, IP-FCM detected no ZAP70 recruitment when T cells were stimulated with antigen in the presence of the src-family kinase inhibitor, PP2. Further, we tested whether IP-FCM possessed sufficient sensitivity to detect the effect of a second, rare class of compounds called SMIPPI (small-molecule inhibitor of PPI). We found that the first-generation non-optimized SMIPPI, Ro-26-4550, inhibited the IL-2:CD25 interaction detected by IP-FCM. This inhibition was detectable using either a recombinant CD25-Fc chimera or physiologic full-length CD25 captured from T cell lysates. Thus, we demonstrate that IP-FCM is a sensitive tool for measuring physiologic PPIs that are modulated by signal transduction and pharmacologic inhibition. 相似文献
887.
Jerónimo Merino Juliana Piña Alberto F. Errazu Verónica Bucalá 《Soil & Sediment Contamination》2003,12(3):417-441
Morphological and chemical changes exhibited by different types of soils heated to different final temperatures are reported. Beds of soils were heated (in a helium atmosphere) from ~20°C to final temperatures, ranging from between 200 to 900°C, simulating ex situ thermal treatments in a nonoxidizing media. Structural changes exhibited by the soil samples during the treatments were analyzed by SEM, measurement of surface area, and measurement of particle porosity. The soil chemical transformations were quantified by means of soil weight loss, light gases yields, and carbon conversion. Soils with low organic matter content do not undergo important structural and chemical changes during the thermal treatment. On the other hand, soils with high organic carbon content suffer significant chemical modifications and, as a consequence, noticeable structural transformations. Indeed, for thermal treatments of about 900°C, weight losses as high as 22?wt%, final surface area of one order of magnitude higher than its original value (untreated soil), and changes of porosity as high as 27% were found for soils of high organic matter content. Simple mathematical equations are proposed to predict the soil weight loss and particle porosity as a function of the treatment temperature. The models provide a good fit to the experimental data. 相似文献
888.
Camila B. Piantino Juliana M. Sousa-Canavez Marta Bellodi-Privato Miguel Srougi Luiz Heraldo Camara-Lopes Gilka Jorge Figaro Gattás Fernanda de Toledo Gonçalves Cintia Fridman Katia R. M. Leite 《In vitro cellular & developmental biology. Animal》2010,46(2):123-130
One of the main obstacles for understanding biological events involved in cancer is the lack of experimental models for in
vitro studies especially for prostate cancer (PC).There are a limited number of PC cell lines being the majority originated
from metastatic tumors mostly acquired from American Tissue Cell Culture which demands importation an expensive and bureaucratic
process. Also it is well known that there are ethnic differences between populations concerning the behavior of tumors and
the research based on cell lines derived from Brazilians should be interesting. Our aim was to develop tumor cell lines from
primary PC. 相似文献
889.
Rui Fil de Oliveira Vitor A Carvalho Almada Maria Gil de Fátima Gil 《Environmental Biology of Fishes》1993,36(4):337-343
Synopsis About two hundred Macrorhamphosus scolopax were observed in a large tank and their behavior was videotaped for subsequent analysis. When not disturbed, the fish moved slowly in a head-down position. Spawning in the tank took place in the last two hours before dark. Courting males change color and actively interact aggressively with other males. They push against each other while swimming in parallel or they charge their opponents with their erected dorsal spine directed at them. Courtship begins near the bottom. After following and swimming parallel to the female the two fish unite tightly by their caudal peduncle, with their ventral regions in close proximity and rise slowly in the water column. During the ascent, the genital papilla of the female extends repeatedly and contacts the genital region of the male. 相似文献