全文获取类型
收费全文 | 2365篇 |
免费 | 310篇 |
国内免费 | 2篇 |
出版年
2022年 | 19篇 |
2021年 | 30篇 |
2019年 | 22篇 |
2018年 | 23篇 |
2017年 | 27篇 |
2016年 | 41篇 |
2015年 | 70篇 |
2014年 | 73篇 |
2013年 | 96篇 |
2012年 | 98篇 |
2011年 | 110篇 |
2010年 | 66篇 |
2009年 | 65篇 |
2008年 | 84篇 |
2007年 | 94篇 |
2006年 | 61篇 |
2005年 | 69篇 |
2004年 | 73篇 |
2003年 | 80篇 |
2002年 | 81篇 |
2001年 | 82篇 |
2000年 | 93篇 |
1999年 | 66篇 |
1998年 | 42篇 |
1997年 | 50篇 |
1996年 | 41篇 |
1995年 | 37篇 |
1994年 | 22篇 |
1993年 | 38篇 |
1992年 | 53篇 |
1991年 | 45篇 |
1990年 | 43篇 |
1989年 | 56篇 |
1988年 | 30篇 |
1987年 | 26篇 |
1986年 | 38篇 |
1985年 | 37篇 |
1984年 | 50篇 |
1983年 | 27篇 |
1982年 | 32篇 |
1981年 | 26篇 |
1980年 | 34篇 |
1979年 | 28篇 |
1977年 | 38篇 |
1976年 | 24篇 |
1975年 | 22篇 |
1974年 | 24篇 |
1973年 | 25篇 |
1972年 | 26篇 |
1970年 | 32篇 |
排序方式: 共有2677条查询结果,搜索用时 15 毫秒
21.
Kinetics of intracellular transport and sorting of lysosomal membrane and plasma membrane proteins 总被引:39,自引:25,他引:14 下载免费PDF全文
We have used monospecific antisera to two lysosomal membrane glycoproteins, lgp120 and a similar protein, lgp110, to compare the biosynthesis and intracellular transport of lysosomal membrane components, plasma membrane proteins, and lysosomal enzymes. In J774 cells and NRK cells, newly synthesized lysosomal membrane and plasma membrane proteins (the IgG1/IgG2b Fc receptor or influenza virus hemagglutinin) were transported through the Golgi apparatus (defined by acquisition of resistance to endo-beta-N-acetylglucosaminidase H) with the same kinetics (t1/2 = 11-14 min). In addition, immunoelectron microscopy of normal rat kidney cells showed that lgp120 and vesicular stomatitis virus G-protein were present in the same Golgi cisternae demonstrating that lysosomal and plasma membrane proteins were not sorted either before or during transport through the Golgi apparatus. To define the site at which sorting occurred, we compared the kinetics of transport of lysosomal and plasma membrane proteins and a lysosomal enzyme to their respective destinations. Newly synthesized proteins were detected in dense lysosomes (lgp's and beta-glucuronidase) or on the cell surface (Fc receptor or hemagglutinin) after the same lag period (20-25 min), and accumulated at their final destinations with similar kinetics (t1/2 = 30-45 min), suggesting that these two lgp's are not transported to the plasma membrane before reaching lysosomes. This was further supported by measurements of the transport of membrane-bound endocytic markers from the cell surface to lysosomes, which exhibited additional lag periods of 5-15 min and half-times of 1.5-2 h. The time required for transport of newly synthesized plasma membrane proteins to the cell surface, and for the transport of plasma membrane markers from the cell surface to lysosomes would appear too long to account for the rapid transport of lgp's from the Golgi apparatus to lysosomes. Thus, the observed kinetics suggest that lysosomal membrane proteins are sorted from plasma membrane proteins at a post-Golgi intracellular site, possibly the trans Golgi network, before their delivery to lysosomes. 相似文献
22.
Regional chromosomal assignment of human renin gene to 1q12----qter and use in linkage studies in Charcot-Marie-Tooth disease 总被引:2,自引:0,他引:2
L R Griffiths G A Nicholson D A Ross M B Zwi J G McLeod T Mohandas B J Morris 《Cytogenetics and cell genetics》1987,45(3-4):231-233
The gene for renin, previously mapped to human chromosome 1, was further localized to 1q12----qter using human-mouse somatic cell hybrid DNAs. The renin DNA probe used (lambda HR5) could detect a HindIII restriction fragment length polymorphism. When used in studies of 12 informative families, no linkage could be found between the renin gene and Charcot-Marie-Tooth disease. Furthermore, an association of any renin allele with hypertension was not apparent. 相似文献
23.
The first unequivocal example of a natural Trilurus helvelicus × T. vulgaris hybrid is described. The specimen was a male and discriminant analysis of physical characters indicated that it was morphologically intermediate between the parent species. A karyotype confirmed that the hybrid bore a haploid set of chromosomes from T. helveticus and a haploid set from T. vulgaris. Examination of the sex chromosomes showed that it was the result of mating between a male T. helveticus and a female T. vulgaris. As numerous mature sperm bundles were observed in both testes, the hybrid was therefore potentially fertile. 相似文献
24.
Plasmid expression and maintenance during long-term starvation-survival of bacteria in well water. 总被引:9,自引:7,他引:2 下载免费PDF全文
Strains of enteric bacteria and pseudomonads containing plasmid R388::Tnl721 (Tpr, Tcr) or pRO101 (Hgr, Tcr) were starved for over 250 days in sterile well water to evaluate effects of starvation-survival on plasmid expression and maintenance. Viable populations dropped to between approximately 0.1 and 1% of the initial populations. Escherichia coli(pRO101) and Pseudomonas cepacia(pRO101) lost both viability and plasmid expression at a lower rate than strains containing R388::Tnl721. Three patterns of host-plasmid interaction were detected: (i) no apparent loss of plasmid expression, (ii) loss of plasmid expression on initial recovery with subsequent expression upon resuscitation, and (iii) loss of capability to produce functional plasmid resistance. 相似文献
25.
PD Dr. G. F. Jirikowski J. F. Ramalho-Ortigao K. W. Kesse F. E. Bloom 《Histochemistry and cell biology》1990,94(2):187-190
Summary We recently described a nonradioactive method for in situ hybridization with 5-bromo-2-deoxyuridine (BrdU) labelled oligonucleotide
probes. An antibody to BrdU and immunocytochemistry were used in order to detect the hybridization signal. We have now applied
this method to semithin Epon sections, in order to hybridize consecutive sections through single cells with different probes
and to stain them with antibodies to neuropeptides. It could be shown that Epon embedding preserves mRNA well. In the present
study we used a BrdU labelled synthetic oligonucleotide probe complementary to a fragment of the vasopressin precursor and
an antibody to Arg-vasopressin. Vasopressin mRNA was demonstrable in a fraction of the vasopressin immunoreactive neurons
in the magnocellular nuclei. In addition some of the magnocellular neurons showed either hybridization or vasopressin immunostaining
only, perhaps indicating different stages of synthetic and secretory activity.
The method described seems to be a valuable tool for studying synthetic activity in peptidergic neurons on a single cell level.
The method might also have potential for in situ hybridization on the electronmicroscopical level. 相似文献
26.
27.
Process intensity of fixed bed glass sphere culture systems is increased considerably by replacing solid glass spheres with open pore glass spheres. This technique demonstrates the possibility of having a system capable of both volumetric and cell density scale up and being suitable for substrate attached and suspension cells. The yields achieved for a number of attached cell lines (approximately 107/ml) demonstrate an increase approaching one order of magnitude over solid glass spheres (approximately 106/ml). Also suspension cells were successfully entrapped in the open pore structure with similar yields. 相似文献
28.
Paul D Griffiths Jillian R Mann Philip J Darbyshire Anne Green 《BMJ (Clinical research ed.)》1988,296(6636):1583-1585
A pilot neonatal screening programme for haemoglobinopathies linked with screening for phenylketonuria and congenital hypothyroidism was reviewed. During 1978 to December 1986 137 000 neonates were tested. There were improvements in the detection rate and accuracy of diagnosis for homozygotes and mixed heterozygotes, mainly associated with the introduction of citrate agarose gel electrophoresis as a follow up procedure on all specimens showing any abnormality on the initial cellulose acetate electrophoresis.We recommend that the programme is continued on a service basis. 相似文献
29.
Huge increase in bacterivores on freshly killed barley roots 总被引:4,自引:0,他引:4
Abstract Adding fresh roots to intact soil cores resulted in marked increases in microbial and microfaunal activity at the resource islands. Microbial activity increased in two phases following root addition. Respiratory activity and concentration of respiratory enzyme (dehydrogenase) in soil adhering to the roots was very high during the first three weeks resulting in anaerobic conditions in the soil. After a period of low respiratory activity and enzyme content, these quantities increased from 6 to 20 weeks, but not enough to maintain anaerobic conditions. Numbers of protozoa peaked earlier than the nematodes. Based on yield coefficients of microbes and bacterivores, the increase in bacterivores was in accordance with root-induced respiration activity. In soil adhering to roots, numbers of bacterial grazers (protozoa and nematodes) were up to 80 and 30 times higher, respectively, than in the surrounding soil. This effect is up to 20 times higher than observed around live root systems, which may suggest that the rhizosphere effect on microbivores could for the major part result from the decomposition of dead segments of the root system. 相似文献
30.
There are many situations in which grain distributions resulting from in situ hybridization of radioactively labeled probes to unique genes should be subjected to a statistical analysis. However, the problems posed by analysis of in situ hybridization data are not straightforward, and no completely satisfying method is currently available. We have developed a procedure in which the major and any number of minor site(s) of hybridization may be specifically located and the significance of each tested. This Zmax procedure first tests the overall distribution for departure from randomness and then identifies significantly overlabeled whole chromosomes (or chromosome arms or other large segments), a process that may be repeated to pinpoint significantly overlabeled regions within these chromosomes. We describe in detail the derivation of the Zmax statistic, present tables of significant Zmax levels, and show with examples how Zmax is used in tests of significance of in situ hybridization data. 相似文献