全文获取类型
收费全文 | 12391篇 |
免费 | 1077篇 |
国内免费 | 2篇 |
出版年
2023年 | 53篇 |
2022年 | 93篇 |
2021年 | 253篇 |
2020年 | 161篇 |
2019年 | 209篇 |
2018年 | 261篇 |
2017年 | 223篇 |
2016年 | 367篇 |
2015年 | 605篇 |
2014年 | 688篇 |
2013年 | 808篇 |
2012年 | 996篇 |
2011年 | 1023篇 |
2010年 | 665篇 |
2009年 | 519篇 |
2008年 | 720篇 |
2007年 | 722篇 |
2006年 | 633篇 |
2005年 | 631篇 |
2004年 | 599篇 |
2003年 | 526篇 |
2002年 | 466篇 |
2001年 | 167篇 |
2000年 | 160篇 |
1999年 | 176篇 |
1998年 | 149篇 |
1997年 | 106篇 |
1996年 | 86篇 |
1995年 | 85篇 |
1994年 | 78篇 |
1993年 | 91篇 |
1992年 | 95篇 |
1991年 | 86篇 |
1990年 | 83篇 |
1989年 | 76篇 |
1988年 | 75篇 |
1987年 | 61篇 |
1986年 | 59篇 |
1985年 | 51篇 |
1984年 | 53篇 |
1983年 | 52篇 |
1982年 | 45篇 |
1981年 | 38篇 |
1980年 | 22篇 |
1979年 | 34篇 |
1978年 | 26篇 |
1977年 | 30篇 |
1976年 | 35篇 |
1975年 | 23篇 |
1973年 | 25篇 |
排序方式: 共有10000条查询结果,搜索用时 156 毫秒
921.
The forests surrounding Bossou, Guinea, are home to a small, semi-isolated chimpanzee community studied for over three decades [1]. In 1992, Matsuzawa [2] reported the death of a 2.5-year-old chimpanzee (Jokro) at Bossou from a respiratory illness. The infant's mother (Jire) carried the corpse, mummified in the weeks following death, for at least 27 days. She exhibited extensive care of the body, grooming it regularly, sharing her day- and night-nests with it, and showing distress whenever they became separated. The carrying of infants' corpses has been reported from a number of primate species, both in captivity and the wild [3-7] - albeit usually lasting a few days only - suggesting a phylogenetic continuity for a behavior that is poignant testament to the close mother-infant bond which extends across different primate taxa. In this report we recount two further infant deaths at Bossou, observed over a decade after the original episode but with striking similarities. 相似文献
922.
923.
Coassin S Schweiger M Kloss-Brandstätter A Lamina C Haun M Erhart G Paulweber B Rahman Y Olpin S Wolinski H Cornaciu I Zechner R Zimmermann R Kronenberg F 《PLoS genetics》2010,6(12):e1001239
Recent studies demonstrated a strong influence of rare genetic variants on several lipid-related traits. However, their impact on free fatty acid (FFA) plasma concentrations, as well as the role of rare variants in a general population, has not yet been thoroughly addressed. The adipose triglyceride lipase (ATGL) is encoded by the PNPLA2 gene and catalyzes the rate-limiting step of lipolysis. It represents a prominent candidate gene affecting FFA concentrations. We therefore screened the full genomic region of ATGL for mutations in 1,473 randomly selected individuals from the SAPHIR (Salzburg Atherosclerosis Prevention program in subjects at High Individual Risk) Study using a combined Ecotilling and sequencing approach and functionally investigated all detected protein variants by in-vitro studies. We observed 55 novel mostly rare genetic variants in this general population sample. Biochemical evaluation of all non-synonymous variants demonstrated the presence of several mutated but mostly still functional ATGL alleles with largely varying residual lipolytic activity. About one-quarter (3 out of 13) of the investigated variants presented a marked decrease or total loss of catalytic function. Genetic association studies using both continuous and dichotomous approaches showed a shift towards lower plasma FFA concentrations for rare variant carriers and an accumulation of variants in the lower 10%-quantile of the FFA distribution. However, the generally rather small effects suggest either only a secondary role of rare ATGL variants on the FFA levels in the SAPHIR population or a recessive action of ATGL variants. In contrast to these rather small effects, we describe here also the first patient with "neutral lipid storage disease with myopathy" (NLSDM) with a point mutation in the catalytic dyad, but otherwise intact protein. 相似文献
924.
O. Sanllorente R. L. Hammond F. Ruano L. Keller A. Tinaut 《Conservation Genetics》2010,11(5):1701-1710
Understanding levels of population differentiation and inbreeding are important issues in conservation biology, especially
for social Hymenoptera with fragmented and small population sizes. Isolated populations are more vulnerable to genetic loss
and extinction than those with extended continuous distributions. However, small populations are not always a consequence
of a recent reduction of their habitat. Thus, determining the history of population isolation and current patterns of genetic
variation of a species is crucial for its conservation. Rossomyrmex minuchae is a slave-making ant with patchy distribution in South Eastern Spain and is classified as vulnerable by the IUCN. In contrast,
the other three known species of the genus are presumed to show more uniform distributions. Here we investigate the genetic
diversity and population structure of R. minuchae and compare it with that found in two other species of the genus: R. anatolicus and R. quandratinodum. We conclude that although genetic diversity of R. minuchae is low, there is no evidence of a recent bottleneck, suggesting a gradual and natural fragmentation process. We also show
extreme population differentiation at nuclear and mitochondrial markers, and isolation by distance at a local scale. Despite
some evidence for inbreeding and low genetic variation within populations, we found almost no diploid males, a finding which
contrasts with that expected in inbred Hymenoptera with single locus complementary sex determination. This could mean that
sex is determined by another mechanism. We argue that continued low population size means that detrimental effects of inbreeding
and low genetic variation are likely in the future. We suggest that a policy of artificial gene flow aimed at increasing within
population variation is considered as a management option. 相似文献
925.
926.
Trincavelli ML Cuboni S Catena Dell'osso M Maggio R Klotz KN Novi F Panighini A Daniele S Martini C 《Purinergic signalling》2010,6(4):373-381
A(2A) adenosine receptors are considered an excellent target for drug development in several neurological and psychiatric disorders. It is noteworthy that the responses evoked by A(2A) adenosine receptors are regulated by D(2) dopamine receptor ligands. These two receptors are co-expressed at the level of the basal ganglia and interact to form functional heterodimers. In this context, possible changes in A(2A) adenosine receptor functional responses caused by the chronic blockade/activation of D(2) dopamine receptors should be considered to optimise the therapeutic effectiveness of dopaminergic agents and to reduce any possible side effects. In the present paper, we investigated the regulation of A(2A) adenosine receptors induced by antipsychotic drugs, commonly acting as D(2) dopamine receptor antagonists, in a cellular model co-expressing both A(2A) and D(2) receptors. Our data suggest that the treatment of cells with the classical antipsychotic haloperidol increased both the affinity and responsiveness of the A(2A) receptor and also affected the degree of A(2A)-D(2) receptor heterodimerisation. In contrast, an atypical antipsychotic, clozapine, had no effect on A(2A) adenosine receptor parameters, suggesting that the two classes of drugs have different effects on adenosine-dopamine receptor interaction. Modifications to A(2A) adenosine receptors may play a significant role in determining cerebral adenosine effects during the chronic administration of antipsychotics in psychiatric diseases and may account for the efficacy of A(2A) adenosine receptor ligands in pathologies associated with dopaminergic system dysfunction. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s11302-010-9201-z) contains supplementary material, which is available to authorized users. 相似文献
927.
Proteomics and systems biology to tackle biological complexity: Yeast as a case study 总被引:1,自引:0,他引:1
In this note we discuss how, by using budding yeast as model organism (as has been done in the past for biochemical, genetics and genomic studies), the integration of "omics" sciences and more specifically of proteomics with systems biology offers a very profitable approach to elucidating regulatory circuits of complex biological functions. 相似文献
928.
Lucero A. Ramón‐Luing Francisco J. Rendón‐Gandarilla Rosa E. Cárdenas‐Guerra Norma A. Rodríguez‐Cabrera Jaime Ortega‐López Leticia Avila‐González Claudia Angel‐Ortiz Carmen N. Herrera‐Sánchez Manuela Mendoza‐García Rossana Arroyo 《Proteomics》2010,10(3):435-444
Trichomonas vaginalis, a sexually transmitted parasite, has many cysteine proteinases (CPs); some are involved in trichomonal pathogenesis, express during infection, and antibodies against CPs have been detected in patient sera. The goal of this study was to identify the antigenic proteinases of T. vaginalis as potential biomarkers for trichomonosis. The proteases detected when T. vaginalis protein extracts are incubated without protease inhibitors, the trichomonad‐active degradome, and the immunoproteome were obtained by using 2‐DE, 2‐D‐zymograms, 2‐D‐Western blot (WB) assays with trichomonosis patient sera, and MS analysis. Forty‐nine silver‐stained spots were detected in the region of 200–21 kDa of parasite protease‐resistant extracts. A similar proteolytic pattern was observed in the 2‐D zymograms. Nine CPs were identified in the 30 kDa region (TvCP1, TvCP2, TvCP3, TvCP4, TvCP4‐like, TvCP12, TvCPT, TvLEGU‐1, and another legumain‐like CP). The major reactive spots to T. vaginalis‐positive patient sera by 2‐D‐WB corresponded to four papain‐like (TvCP2, TvCP4, TvCP4‐like, TvCPT), and one legumain‐like (TvLEGU‐1) CPs. The genes of TvCP4, TvCPT, and TvLEGU‐1 were cloned, sequenced, and expressed in Escherichia coli. Purified recombinant CPs were recognized by culture‐positive patient sera in 1‐D‐WB assays. These data show that some CPs could be potential biomarkers for serodiagnosis of trichomonosis. 相似文献
929.
3,6-Anhydro-1-(aryl or alkylamino)-1-deoxy-d-sorbitol derivatives have been prepared in four steps from isosorbide, a by-product from the starch industry. The inhibitory activities of these new compounds have been evaluated towards 13 glycosidases. A first lead-compound was identified, which inhibited β-N-acetylglucosaminidase from bovine kidney (82% inhibition at 1 mM). 相似文献
930.
Pedroso RS Lavrador MA Ferreira JC Candido RC Maffei CM 《Memórias do Instituto Oswaldo Cruz》2010,105(8):993-1000
The pathogenicity of Cryptococcus neoformans is heterogeneous and is associated with the expression of virulence factors. This study aimed to correlate the pathogenicity of C. neoformans var. grubii in BALB/c mice with in vitro virulence factors, fluconazole minimal inhibitory concentrations (MICs) and molecular profiles, before and after animal passage. Ten environmental isolates and one ATCC strain of C. neoformans var. grubii mating type α were evaluated. Most isolates (91%) killed 50% or more of the infected animals by day 24 postinfection and were recovered from the lungs and brains of surviving animals on days 7 and 14 postinfection. The burden of yeast in the lungs was more variable than that in the brain. The differences in the expression of virulence factors (growth at 37oC, presence and size of the capsule and production of melanin, urease, proteinase and phospholipase) by most isolates pre and postpassage in animals were not statistically significant. The fluconazole MICs in postpassaged lines differed by a one-dilution from the MIC of the corresponding prepassaged line for six isolates. Using molecular typing [polymerase chain reaction-fingerprinting with (GACA)4 and M13], eight isolates were identified as VNI and three as VNII. We concluded that different isolates with the same molecular and phenotypic profiles, including isolates that are markedly hypervirulent, span a wide range of virulence and there were no changes in virulence factors in the postpassaged lines when compared with the corresponding nonpassaged lines. 相似文献