全文获取类型
收费全文 | 2882篇 |
免费 | 199篇 |
国内免费 | 2篇 |
出版年
2022年 | 24篇 |
2021年 | 38篇 |
2020年 | 21篇 |
2019年 | 36篇 |
2018年 | 34篇 |
2017年 | 37篇 |
2016年 | 61篇 |
2015年 | 127篇 |
2014年 | 106篇 |
2013年 | 139篇 |
2012年 | 222篇 |
2011年 | 184篇 |
2010年 | 120篇 |
2009年 | 122篇 |
2008年 | 157篇 |
2007年 | 158篇 |
2006年 | 152篇 |
2005年 | 156篇 |
2004年 | 151篇 |
2003年 | 126篇 |
2002年 | 120篇 |
2001年 | 72篇 |
2000年 | 79篇 |
1999年 | 49篇 |
1998年 | 47篇 |
1997年 | 25篇 |
1996年 | 30篇 |
1995年 | 19篇 |
1994年 | 17篇 |
1993年 | 32篇 |
1992年 | 34篇 |
1991年 | 19篇 |
1990年 | 29篇 |
1989年 | 28篇 |
1988年 | 28篇 |
1987年 | 19篇 |
1986年 | 15篇 |
1985年 | 22篇 |
1984年 | 15篇 |
1983年 | 21篇 |
1982年 | 15篇 |
1980年 | 12篇 |
1979年 | 12篇 |
1978年 | 19篇 |
1976年 | 11篇 |
1975年 | 12篇 |
1974年 | 19篇 |
1973年 | 10篇 |
1972年 | 17篇 |
1971年 | 12篇 |
排序方式: 共有3083条查询结果,搜索用时 218 毫秒
101.
Swift Candice L. Brown Jennifer L. Seppälä Susanna O’Malley Michelle A. 《Journal of industrial microbiology & biotechnology》2019,46(9-10):1427-1433
Journal of Industrial Microbiology & Biotechnology - Anaerobic gut fungi are biomass degraders that form syntrophic associations with other microbes in their native rumen environment. Here,... 相似文献
102.
Paul M. Peterson Cristina Roquet Konstantin Romaschenko Yolanda Herrera Arrieta Alfonso Susanna 《植物分类学报:英文版》2022,60(3):621-629
A phylogeny based on the analysis of six DNA sequence markers (ITS, ndhA intron, rpl32-trnL, rps3, rps16 intron, and rps16-trnK) is used to infer ancestral areas and divergence times, and reconstruct the biogeographical history and evolution of 150 of the 183 (82%) species of Muhlenbergia. Our results suggest that the genus originated 9.3 mya in the Sierra Madre (Occidental and Oriental) in Mexico, splitting into six lineages: M. ramulosa diverging 8.2 mya, M. subg. Muhlenbergia at 5.9 mya, M. subg. Pseudosporobolus at 5.9 mya, M. subg. Clomena at 5.4 mya, M. subg. Bealia at 4.3 mya, and M. subg. Trichochloa at 1 mya, each of these with a high probability of Sierra Madrean origin. Our results further suggest that founder-event speciation from Sierra Madre to South America occurred independently multiple times in all five subgenera during the Pleistocene and late Pliocene. One long-distance dispersal event most likely originating from Central or Eastern North America to East and Central Asia occurred 1.6–1 mya in M. subg. Muhlenbergia. In our cladogram, members of M. subg. Trichochloa show little genetic resolution, suggesting very low levels of divergence among the species, and this may be a consequence of rapid radiation. 相似文献
103.
Herpesviruses maintain long-term infectivity without marked antigenic variation. They must therefore evade neutralization by other means. Immune sera block murine gammaherpesvirus-68 (MHV-68) infection of fibroblasts, but fail to block and even enhance its infection of IgG Fc receptor-bearing cells, suggesting that the antibody response to infection is actually poor at ablating virion infectivity completely. Here we analyzed this effect further by quantitating the glycoprotein-specific antibody response of MHV-68 carrier mice. Gp150 was much the commonest glycoprotein target and played a predominant role in driving Fc receptor-dependent infection: when gp150-specific antibodies were boosted, Fc receptor-dependent infection increased; and when gp150-specific antibodies were removed, Fc receptor-dependent infection was largely lost. Neither gp150-specific monoclonal antibodies nor gp150-specific polyclonal sera gave significant virion neutralization. Gp150 therefore acts as an immunogenic decoy, distorting the MHV-68-specific antibody response to promote Fc receptor-dependent infection and so compromise virion neutralization. This immune evasion mechanism may be common to many non-essential herpesvirus glycoproteins. 相似文献
104.
Neuronal specification is often seen as a multistep process: earlier regulators confer broad neuronal identity and are followed by combinatorial codes specifying neuronal properties unique to specific subtypes. However, it is still unclear whether early regulators are re-deployed in subtype-specific combinatorial codes, and whether early patterning events act to restrict the developmental potential of postmitotic cells. Here, we use the differential peptidergic fate of two lineage-related peptidergic neurons in the Drosophila ventral nerve cord to show how, in a feedforward mechanism, earlier determinants become critical players in later combinatorial codes. Amongst the progeny of neuroblast 5–6 are two peptidergic neurons: one expresses FMRFamide and the other one expresses Nplp1 and the dopamine receptor DopR. We show the HLH gene collier functions at three different levels to progressively restrict neuronal identity in the 5–6 lineage. At the final step, collier is the critical combinatorial factor that differentiates two partially overlapping combinatorial codes that define FMRFamide versus Nplp1/DopR identity. Misexpression experiments reveal that both codes can activate neuropeptide gene expression in vast numbers of neurons. Despite their partially overlapping composition, we find that the codes are remarkably specific, with each code activating only the proper neuropeptide gene. These results indicate that a limited number of regulators may constitute a potent combinatorial code that dictates unique neuronal cell fate, and that such codes show a surprising disregard for many global instructive cues. 相似文献
105.
106.
The larval pre-competency period and competency window are important in delimiting the potential dispersal distance for pelagic larvae of sessile marine fauna. Here, we provide evidence for morphological changes in the late planulae of Lophelia pertusa that have implications for their dispersal potential. Three weeks after spawning, the planulae gain functional cnidocysts, indicating that they are competent to settle at this time. Cnidae have been shown to be used for primary anchoring during settling, and before this time point, the larvae most probably do not have the ability to attach to a substrate in high flow conditions. The appearance of functional cnidae coincides with larvae gaining a flexible mouth that can be opened to the full width of the larva. The larval isorhizas differ the most from the adult polyps isorhizas, while the p- and b-mastigophores bear more resemblance to the adult homologues of similar size. The external and internal morphology of late planulae is further described with demonstration of long apical cilia and its effect on swimming agility, morphological changes of the ciliated cells in the larval mouth region and an internal nerve plexus. This study also indicates that L. pertusa planulae seek out cryptic spaces for settling. 相似文献
107.
Agatha A. van der Klaauw Sophie Croizier Edson Mendes de Oliveira Lukas K.J. Stadler Soyoung Park Youxin Kong Matthew C. Banton Panna Tandon Audrey E. Hendricks Julia M. Keogh Susanna E. Riley Sofia Papadia Elana Henning Rebecca Bounds Elena G. Bochukova Vanisha Mistry Stephen O’Rahilly Richard B. Simerly I. Sadaf Farooqi 《Cell》2019,176(4):729-742.e18
108.
Lange Alexander Schwieger Robert Plöntzke Julia Schäfer Stefan Röblitz Susanna 《Journal of mathematical biology》2019,78(3):579-606
Journal of Mathematical Biology - The reproductive cycle of mono-ovulatory species such as cows or humans is known to show two or more waves of follicular growth and decline between two successive... 相似文献
109.
Jason E. Chung Hannah R. Joo Jiang Lan Fan Daniel F. Liu Alex H. Barnett Supin Chen Charlotte Geaghan-Breiner Mattias P. Karlsson Magnus Karlsson Kye Y. Lee Hexin Liang Jeremy F. Magland Jeanine A. Pebbles Angela C. Tooker Leslie F. Greengard Vanessa M. Tolosa Loren M. Frank 《Neuron》2019,101(1):21-31.e5
110.
rac-Simendan, (±)-(R, S)-[[4-(1,4,5,6-tetrahydro-4-methyl-6-oxo-3-pyridazinyl)-phenyl]hydrazono]propanedinitrile, and the levorotatory enantiomer levosimendan, are drug candidates intended for the treatment of congestive heart failure. An enantiospecific high-performance liquid chromatographic (HPLC) method suitable for determination of the ratio of the enantiomer concentrations in blood plasma samples was developed. Direct resolution of the enantiomers was achieved by using a chiral β-cyclodextrin stationary phase in reversed phase mode. With an eluent containing 24–33% of methanol in a 0.5% (v/v) triethylammonium acetate buffer, pH 6.0, and a flow rate of 1 ml/min, a resolution (1.2–1.6) adequate for the determinations was achieved. By using UV detection, the relative concentration of the enantiomers in plasma was assessed down to 10 ng/ml. For the racemate, the results indicated a slightly enantioselective disposition and plasma protein binding in rat, dog, and man. The pure enantiomer, levosimendan, was found not to isomerize in vivo. © 1996 Wiley-Liss, Inc. 相似文献