全文获取类型
收费全文 | 40096篇 |
免费 | 3271篇 |
国内免费 | 5203篇 |
出版年
2023年 | 877篇 |
2022年 | 944篇 |
2021年 | 1370篇 |
2020年 | 1427篇 |
2019年 | 1997篇 |
2018年 | 1564篇 |
2017年 | 1394篇 |
2016年 | 1344篇 |
2015年 | 1300篇 |
2014年 | 2017篇 |
2013年 | 2811篇 |
2012年 | 1669篇 |
2011年 | 1841篇 |
2010年 | 1494篇 |
2009年 | 1929篇 |
2008年 | 1906篇 |
2007年 | 2088篇 |
2006年 | 1799篇 |
2005年 | 1682篇 |
2004年 | 1427篇 |
2003年 | 1356篇 |
2002年 | 1217篇 |
2001年 | 944篇 |
2000年 | 876篇 |
1999年 | 784篇 |
1998年 | 729篇 |
1997年 | 609篇 |
1996年 | 558篇 |
1995年 | 560篇 |
1994年 | 542篇 |
1993年 | 486篇 |
1992年 | 446篇 |
1991年 | 479篇 |
1990年 | 365篇 |
1989年 | 344篇 |
1988年 | 347篇 |
1987年 | 283篇 |
1986年 | 317篇 |
1985年 | 493篇 |
1984年 | 611篇 |
1983年 | 331篇 |
1982年 | 479篇 |
1981年 | 459篇 |
1980年 | 410篇 |
1979年 | 304篇 |
1978年 | 226篇 |
1977年 | 233篇 |
1976年 | 209篇 |
1975年 | 164篇 |
1973年 | 178篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
71.
Nicholas Shea 《Biology & philosophy》2007,22(3):313-331
There is ongoing controversy as to whether the genome is a representing system (Sterelny K., Smith K.C. and Dickson M. 1996.
Biol. Philos. 11: 377–403; Griffiths P.E. 2001. Philos. Sci. 68: 394–412). Although it is widely recognised that DNA carries
information, both correlating with and coding for various outcomes, neither of these implies that the genome has semantic
properties like correctness or satisfaction conditions (Godfrey-Smith P. 2002. In: Wolenski J. and Kajania-Placek K. (eds),
In the Scope of Logic, Methodology, and the Philosophy of Sciences, Vol. II. Kluwer, Dordrecht, pp. 387–400). Here a modified
version of teleosemantics is applied to the genome to show that it does indeed have semantic properties – there is representation
in the genome. The account differs in three respects from previous attempts to apply teleosemantics to genes. It emphasises
the role of the consumer of representations (in addition to their mode of production). It rejects the standard assumption
that genetic representation can be used to explain the course of an organism’s development. And it identifies the explanatory
role played by representational properties of the genome. A striking consequence of this account is that other inheritance
systems could also be representational. Thus, a version of the parity thesis is accepted (Griffiths P.E. 2001. Philos. Sci.
68: 394–412). However, the criteria for being an inheritance system are demanding, so semantic properties are not ubiquitous. 相似文献
72.
In the framework of the palaeogeographical reconstruction of the Western Taurus during Jurassic, the study of northern and eastern boundary of the Taurids started. Detailed facies analysis evidenced the position of the Barla Dag ramp between two elevated areas: the southern rimmed shelf extension of the platform system and the northern neritic-beach-land plain. In the basal biostratigraphical and ecological characteristics of the Balcikhisar volcano-sedimentary sequence, correlated with the Fele outcrop, one genus and three new species of foraminifers have been found: Sievoides kocyigiti n. gen., n. sp. and Mesoendothyra altineriana n. sp. from neritic environment, and Kurnubia feleensis n. sp. from rimmed shelf lagoon. Both carbonate sedimentary deposits are intercalated with spilitic-basalt pillow lava flows. The age of the new three species is Kimmeridgian, controlled by some foraminifer golden hooks. 相似文献
73.
74.
75.
76.
M.A. Mena M.J. Casarejos J.A. Rodríguez-Navarro I. Rodal J.G. de Yebenes 《FEBS letters》2009,583(1):168-174
Parkin mutations produce Parkinson’s disease (PD) in humans and nigrostriatal dopamine lesions related to increased free radicals in mice. We examined the effects of NP7, a synthetic, marine derived, free radical scavenger which enters the brain, on H2O2 toxicity in cultured neurons and glia from wild-type (WT) and parkin null mice (PK-KO).NP7, 5-10 μM, prevented the H2O2 induced apoptosis and necrosis of midbrain neuronal and glial cultures from WT and PK-KO mice. NP7 suppressed microglial activation and the H2O2 induced drop-out of dopamine neurons. Furthermore, NP7 prevented the increased phosphorylation of ERK and AKT induced by H2O2. NP7 may be a promising neuroprotector against oxidative stress in PD. 相似文献
77.
We isolated eight polymorphic microsatellites from the neotropical tree Luehea seemannii for gene flow and genetic structure studies. We used a streptavidin subtractive enrichment technique to develop a library of CA/GT repeats. Eight loci were screened for diversity from 96 individuals from Barro Colorado Island (BCI) and neighbouring Gigante peninsula in Panama. Luehea seemannii shows moderate levels of genetic diversity within these two populations. Allelic richness ranged from four to nine alleles and averaged 6.44 alleles per locus. Average expected heterozygosity was 0.65 on BCI and 0.60 on Gigante. Results are compared to microsatellite data from another wind‐dispersed gap colonizing species common in Panama. 相似文献
78.
Jan Dirk van Elsas Alexander V Semenov Rodrigo Costa Jack T Trevors 《The ISME journal》2011,5(2):367-183
In this review, our current understanding of the species Escherichia coli and its persistence in the open environment is examined. E. coli consists of six different subgroups, which are separable by genomic analyses. Strains within each subgroup occupy various ecological niches, and can be broadly characterized by either commensalistic or different pathogenic behaviour. In relevant cases, genomic islands can be pinpointed that underpin the behaviour. Thus, genomic islands of, on the one hand, broad environmental significance, and, on the other hand, virulence, are highlighted in the context of E. coli survival in its niches. A focus is further placed on experimental studies on the survival of the different types of E. coli in soil, manure and water. Overall, the data suggest that E. coli can persist, for varying periods of time, in such terrestrial and aquatic habitats. In particular, the considerable persistence of the pathogenic E. coli O157:H7 is of importance, as its acid tolerance may be expected to confer a fitness asset in the more acidic environments. In this context, the extent to which E. coli interacts with its human/animal host and the organism''s survivability in natural environments are compared. In addition, the effect of the diversity and community structure of the indigenous microbiota on the fate of invading E. coli populations in the open environment is discussed. Such a relationship is of importance to our knowledge of both public and environmental health. 相似文献
79.
The hypoglycemic agent, 2-tetradecylglycidic acid (TDGA), administered in vivo lowered the concentration of plasma glucose and ketone bodies but raised the concentration of liver and plasma triglycerides in 10-day-old suckling rats. Phospholipid and cholesterol content of the plasma and liver were unaffected by drug treatment. TDGA inhibited the in vivo oxidation of [1-14C]palmitate but not that of [1-14C]decanoate. In suckling rat liver perfusion, TDGA totally inhibited ketone body formation from palmitate and depressed ketone body production from decanoate by 20%. Liver ATP and ADP content in the presence of TDGA decreased although this was probably a reflection of the increased triglyceride content of the liver since the was the same as control livers. The results are discussed in relation to the diet and to the inhibition of carnitine acyl transferase in suckling rats. 相似文献
80.
Focal contacts of spreading platelets with the substratum 总被引:1,自引:0,他引:1
Contacts with glass substratum formed by the spreading rabbit platelets were examined by an antibody-exclusion method; monoclonal antibodies against 80 kD bovine serum protein were used. It was found that platelets form focal contacts in the course of spreading. The size of the largest focal contacts formed by platelets is smaller than that of the contacts formed by fibroblasts. The antibody-exclusion method revealed focal contacts of platelets much more clearly than interference reflection microscopy (IRM). The similarity of reactions involved in spreading platelets and of large nucleus-containing tissue cells is discussed. 相似文献