全文获取类型
收费全文 | 4630篇 |
免费 | 364篇 |
国内免费 | 3篇 |
专业分类
4997篇 |
出版年
2023年 | 12篇 |
2022年 | 42篇 |
2021年 | 78篇 |
2020年 | 48篇 |
2019年 | 60篇 |
2018年 | 62篇 |
2017年 | 72篇 |
2016年 | 131篇 |
2015年 | 212篇 |
2014年 | 217篇 |
2013年 | 299篇 |
2012年 | 385篇 |
2011年 | 378篇 |
2010年 | 256篇 |
2009年 | 225篇 |
2008年 | 294篇 |
2007年 | 322篇 |
2006年 | 296篇 |
2005年 | 248篇 |
2004年 | 265篇 |
2003年 | 235篇 |
2002年 | 215篇 |
2001年 | 44篇 |
2000年 | 37篇 |
1999年 | 56篇 |
1998年 | 69篇 |
1997年 | 45篇 |
1996年 | 40篇 |
1995年 | 47篇 |
1994年 | 39篇 |
1993年 | 35篇 |
1992年 | 28篇 |
1991年 | 27篇 |
1990年 | 27篇 |
1989年 | 19篇 |
1988年 | 14篇 |
1987年 | 13篇 |
1986年 | 12篇 |
1985年 | 20篇 |
1984年 | 8篇 |
1983年 | 4篇 |
1982年 | 7篇 |
1981年 | 10篇 |
1980年 | 5篇 |
1979年 | 5篇 |
1978年 | 5篇 |
1974年 | 3篇 |
1972年 | 5篇 |
1971年 | 3篇 |
1966年 | 4篇 |
排序方式: 共有4997条查询结果,搜索用时 0 毫秒
1.
Thorsten Thye Genevieve Scarisbrick Edmund N. L. Browne Margaret Amanua Chinbuah John Gyapong Ivy Osei Ellis Owusu-Dabo Stefan Niemann Sabine Rüsch-Gerdes Christian G. Meyer Rolf D. Horstmann 《PloS one》2009,4(7)
The gene of Cytotoxic T Lymphocyte-associated Antigen 4 (CTLA4), a negative regulator of T lymphocytes, contains a single-nucleotide polymorphism (SNP) at position +6230A->G (ct60A->G), which has been found associated with several autoimmune diseases and appears to reduce T-cell inhibitory activity. In Ghana, West Africa, we compared the frequencies of CTLA4 +6230 A/G and 6 haplotype-tagging SNPs in 2010 smear-positive, HIV-negative patients with pulmonary tuberculosis (TB) and 2346 controls matched for age, gender and ethnicity. We found no difference in allele frequencies between cases and controls. However, +6230A and a distinct CTLA4 haplotype and a diplotype comprising the +6230A allele were significantly less frequent among cases with large opacities in chest radiographs compared to those with small ones (Pcorrected [cor] = 0.002, Pcor = 0.00045, P = 0.0005, respectively). This finding suggests that an increased T-cell activity associated with the CTLA4 +6230G allele contributes to pathology rather than to protection in pulmonary TB. 相似文献
2.
Glucoraphasatin is an atypical glucosinolate mainly found in Raphanus sativus roots and sprouts. This review focuses on the chemistry, the occurrence, and the biological properties of glucoraphasatin. 相似文献
3.
Summary Conditioned culture medium from Daudi cells was used as a source of soluble H-Y antigen. Concentrated culture medium was labeled with 125I and then fractionated by gel filtration. Column fractions were assayed for the presence of H-Y antigen by urease-ELISA. H-Y antigen-containing fractions were then pooled and subjected to an improved immunoprecipitation protocol. Three predominant H-Y antigenic proteins were identified with estimated molecular weights of above 200,000, 50,000, and 20,000. 相似文献
4.
Abstract We have analyzed the sequence downstream of rpoN from Zcinetobacter calcoaceticus and identified an open reading frame encoding a protein with high similarity to UDP- N -acetylgucosamine 1-carboxyvinyl-transferase (MurZ). Multicopy plasmids encoding this enzyme conferred phosphomycin resistance to A. calcoaceticus . The polar effect of a rpoN mutation on the phosphomycin resistance level suggests that murZ is, in part, cotranscribed with rpoN . These observations confirm that A. calcoaceticus represents the first exceptin from a conserved genetic context of rpoN observed in several other Gram-negative bacteria. 相似文献
5.
Sabine Jell-Bahlsen 《Dialectical Anthropology》1988,13(2):199-207
Conclusion People have many names. But, changing one's name is no small thing. It can signify a major step in life or an embarrassing story, as in the last case.A person has a complex individual identity. His collective identity is clear from the moment he is conceived. He is one with a body of people, his kinsmen, who share one common ancestor and through him access to land and resources. The continuation of this group and its name is perpetuated through paternal descent.Kingroup membership ensures a person's place in life, his right to exist, eat, live and enjoy. But, who is he, apart from being a kinsman? Which kinsman is he? How are people going to interact with him? His individual identity will become clear through time. He is a re-incarnation of ancestor x. The circumstances of his birth were such. He behaves like this. He has these personal traits. This has happened to him. He has achieved that. There is no permanent role attached to an individual. He is neither bound to class nor caste. He is dynamic and changes constantly. His life is one of achievement, constant striving and upward mobility till death — when it all begins again. His name signals his state of being in time and existence.Sabine Jell-Bahlsen is an anthropologist and filmmaker. 相似文献
6.
Embryogenic suspension cultures of Abies alba were established using an embryogenic suspensor mass culture originating from the zygotic embryo in immature seed explants (Schuller et al. 1989). Protoplasts were isolated from the suspension material. The protoplasts were immobilized in alginate layers in order to follow the development of single protoplasts. During the first days of protoplast culture a modified Kao and Michayluk (1975) medium proved to be necessary for subsequent divisions. The formation of proembryos succeeded within 2–3 weeks when subcultured with a modified Schenk and Hildebrandt (1972) liquid medium. Light, enhanced sugar concentration, and the addition of abscisic acid led to the formation of slightly green torpedo-shaped somatic embryos after 6–8 weeks from protoplast isolation.Abbreviations ABA
abscisic acid
- BAP
N6-benzyladenine
- 2,4-D
2,4-dichlorophenoxyacetic acid
- ESM
Embryonal suspensor mass (Gupta and Durzan 1986)
- KM
Kao and Michayluk (1975)
- LP
(von Arnold and Eriksson 1977)
- MES
2-(N-morpholino)ethane-sulfonic acid
- NAA
1-naphthalene-acetic acid (sodium salt)
- PVP
polyvinylpyrrolidone
- SH
Schenk and Hildebrandt (1972)
- Tween 80
polyoxyethylene-sorbitan-monooleate 相似文献
7.
A unifying approach described by a random birth and death process which includes both environmental and demographic noise is introduced. It is shown that both of these noise sources play an essential role in extinction processes in general. The probability distribution of the lifetime of a population is determined and its dependence on the parameters of the model is discussed. Finally a population divided into subpopulations is modeled. The lifetime of this ensemble of subpopulations is compared to the lifetime of one large population. 相似文献
8.
Oliver Selberg Sabine Schlaak Hans J. Balks Alexander von zur Mühlen Manfred J. Müller 《European journal of applied physiology and occupational physiology》1991,63(6):417-423
The contribution of insulin (3.6 pmol.kg body mass-1.min-1) to adrenaline-induced (0.164 nmol.kg fat free mass-1.min-1) thermogenesis was studied in ten postabsorptive healthy volunteers using two sequential protocols. Variables considered were oxygen consumption as well as carbon dioxide production, heart rate, blood pressure, plasma concentrations of glucose, insulin, glycerol, free fatty acids, beta-HO-butyrate and lactate. Adrenaline increased plasma concentrations of glucose, glycerol, free fatty acids, and beta-HO-butyrate, and heart rate and metabolic rate during normo-insulinaemia [61.3 (SEM 6.6) pmol.l-1]. Similar effects were observed during hyperinsulinaemia [167.9 (SEM 18.7) pmol.l-1], but the effect of adrenaline on oxygen consumption was reduced. On average, metabolic rate increased by 12.9% during normo-insulinaemia and by 8.9% during hyperinsulinaemia. We concluded that relative hyperinsulinaemia resulted in decreased adrenaline-induced thermogenesis and therefore increased whole body anabolism. 相似文献
9.
Katrin Kausch Clemens R. Müller Tiemo Grimm Kenneth Ricker Marcella Rietschel Sabine Rudnik-Schöneborn Klaus Zerres 《Human genetics》1991,86(3):317-318
Summary Two recent articles have reported the linkage of a gene for recessive spinal muscular atrophy (SMA) on the chromosome region 5q11.2–13.3. Our data show no linkage of the dominantly inherited forms of SMA to this chromosome region. 相似文献
10.
Daniel Chappard Christian Alexandre Sabine Palle George Riffat 《Biotechnic & histochemistry》1986,61(2):93-96
Polyester fibers are not dissolved by either glycol methacrylate or methyl methacrylate. Commercial polyester wadding is consequently an advantageous material to use in getting precise orientation of tissue specimens during embedding in methacrylate. 相似文献