全文获取类型
收费全文 | 1744篇 |
免费 | 122篇 |
出版年
2023年 | 8篇 |
2022年 | 19篇 |
2021年 | 37篇 |
2020年 | 17篇 |
2019年 | 23篇 |
2018年 | 32篇 |
2017年 | 30篇 |
2016年 | 48篇 |
2015年 | 80篇 |
2014年 | 95篇 |
2013年 | 102篇 |
2012年 | 137篇 |
2011年 | 122篇 |
2010年 | 83篇 |
2009年 | 80篇 |
2008年 | 113篇 |
2007年 | 96篇 |
2006年 | 93篇 |
2005年 | 81篇 |
2004年 | 62篇 |
2003年 | 76篇 |
2002年 | 56篇 |
2001年 | 44篇 |
2000年 | 24篇 |
1999年 | 34篇 |
1998年 | 10篇 |
1997年 | 15篇 |
1996年 | 13篇 |
1995年 | 9篇 |
1994年 | 10篇 |
1993年 | 15篇 |
1992年 | 11篇 |
1991年 | 19篇 |
1990年 | 19篇 |
1989年 | 12篇 |
1988年 | 19篇 |
1987年 | 20篇 |
1986年 | 14篇 |
1985年 | 15篇 |
1984年 | 8篇 |
1983年 | 12篇 |
1982年 | 4篇 |
1981年 | 4篇 |
1979年 | 3篇 |
1978年 | 6篇 |
1977年 | 4篇 |
1975年 | 6篇 |
1974年 | 3篇 |
1973年 | 4篇 |
1967年 | 3篇 |
排序方式: 共有1866条查询结果,搜索用时 31 毫秒
101.
Phagocytosis by neutrophils, macrophages, and other professional phagocytes requires rapid remodeling of actin. Early phagosomes are surrounded by a rim of F-actin that is disassembled during phagosomoal maturation. Breakdown of periphagosomal F-actin and phagolysosome fusion are calcium dependent processes in neutrophils interacting with serum-opsonized prey, but appears to be calcium independent in macrophages interacting with serum- or IgG-opsonized prey. In the present study, we found that calcium was necessary for phagocytosis, breakdown of periphagosomal F-actin, and phagosomal maturation in J774 macrophages interacting with unopsonized prey. We also observed that lipophosphoglycan (LPG) from Leishmania donovani promastigotes required calcium to exert its inhibitory effect on macrophage phagocytosis and periphagosomal F-actin breakdown. We conclude that calcium is essential for phagocytosis, depolymerization of periphagosomal F-actin, and phagosomal maturation in J774 macrophages interacting with unopsonized prey, as well as for proper functioning of LPG. 相似文献
102.
103.
A Rab8-specific GDP/GTP exchange factor is involved in actin remodeling and polarized membrane transport
下载免费PDF全文
![点击此处可从《Molecular biology of the cell》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The mechanisms mediating polarized delivery of vesicles to cell surface domains are poorly understood in animal cells. We have previously shown that expression of Rab8 promotes the formation of new cell surface domains through reorganization of actin and microtubules. To unravel the function of Rab8, we used the yeast two-hybrid system to search for potential Rab8-specific activators. We identified a coil-coiled protein (Rabin8), homologous to the rat Rabin3 that stimulated nucleotide exchange on Rab8 but not on Rab3A and Rab5. Furthermore, we show that rat Rabin3 has exchange activity on Rab8 but not on Rab3A, supporting the view that rat Rabin3 is the rat equivalent of human Rabin8. Rabin8 localized to the cortical actin and expression of Rabin8 resulted in remodeling of actin and the formation of polarized cell surface domains. Activation of PKC by phorbol esters enhanced translocation of both Rabin8 and Rab8-specific vesicles to the outer edge of lamellipodial structures. Moreover, coexpression of Rabin8 with dominant negative Rab8 (T22N) redistributes Rabin8 from cortical actin to Rab8-specific vesicles and promotes their polarized transport to cell protrusions. The C-terminal region of Rabin8 plays an essential role in this transport. We propose that Rabin8 is a Rab8-specific activator that is connected to processes that mediate polarized membrane traffic to dynamic cell surface structures. 相似文献
104.
105.
Wallenius K Wallenius V Sunter D Dickson SL Jansson JO 《Biochemical and biophysical research communications》2002,293(1):560-565
Recently we found that interleukin-6 (IL-6) knockout mice develop mature-onset obesity and that a single intracerebroventricular (ICV) injection of IL-6 increases energy expenditure. In the present study we investigated if chronic ICV treatment with IL-6 can suppress body fat mass. IL-6 was injected ICV daily for two weeks to rats fed a high-fat diet. IL-6 treatment but not saline treatment decreased body weight by 8.4% and decreased the relative weights of mesenteric and retroperitoneal fat pads. Consistent with this, circulating leptin levels were decreased by 40% after IL-6 treatment but not after saline treatment. Average food intake per day was decreased in the IL-6 treated group compared to the saline treated rats. IL-6 treatment did not change hepatic expression of the acute-phase protein haptoglobin, serum levels of insulin or insulin-like growth factor-I, or the weights of the heart, liver, kidneys, adrenals, and spleen. We conclude that centrally administered IL-6 can decrease body fat in rats without causing acute-phase reaction. 相似文献
106.
Susceptibility to tebufenozide and methoxyfenozide of beet armyworm [Spodoptera exigua (Hübner)] from the southern United States and Thailand was determined through exposure of first and third instars to dipped cotton leaves. Among the field populations evaluated, tebufenozide LC50 values for first and third instars, respectively, ranged from 0.377 to 4.41 and 4.37-46.6 microg (AI) /ml of solution. Methoxyfenozide LC50 values for first and third instars of field populations ranged from 0.058 to 0.487 and 0.601-3.83 microg (AI)/ml of solution. A Thailand field strain exhibiting reduced susceptibility to both compounds was subjected to intense laboratory selection for three nonconsecutive generations. At the LC50 and LC90, selected Thailand strains were 45-68 times and 150-1,500 times less susceptible to tebufenozide and 340-320 times and 120-67 times less susceptible to methoxyfenozide as first and third instars, respectively, when compared with the laboratory reference strain. Among the U.S. field populations evaluated, ones from Belle Glade, FL, and Florence, SC, were generally the most susceptible and ones from Maricopa and Parker, AZ, were the least susceptible. Selection of the Thailand field strain with tebufenozide reduced susceptibility to both compounds, and selection of Thailand strains previously pressured with either compound further reduced susceptibility to both, suggesting at least some commonality of resistance mechanism. Characterization of this resistance will provide information that will be helpful for pro-active management of resistance for this valuable group of insecticides. 相似文献
107.
Apoptosis within bovine follicular cells and its effect on oocyte development during in vitro maturation 总被引:10,自引:0,他引:10
Developmental competence of oocytes is compromised if they originate from atretic follicles. Apoptosis is the underlying process of atresia. Apoptotic changes in follicular cells are thought to influence the outcome of IVF. The aim of this study was to investigate apoptosis in different compartments of single bovine follicles (follicular wall, granulosa and cumulus cells (CC)) in relation to COC morphology, and to determine whether the addition, in vitro, of exogenous follicular cells from atretic follicles to maturing cumulus oocyte complexes (COCs) influenced the development of oocytes.Antral follicles were dissected from bovine ovaries and opened to obtain COCs and free floating granulosa cells (GC). The COCs were classified according to morphology. Apoptosis was determined in cumulus and granulosa cells and in homogenates of the remaining follicular wall.For every morphological class of COCs, a large variability of apoptotic expression was found in all follicle compartments. Follicular wall apoptosis was not correlated to COC morphology or to the percentage of apoptotic granulosa or cumulus cells. In grade 1 (best morphology) COCs, the degree of apoptosis in granulosa cells was comparable to cumulus cell apoptosis (P<0.01). The overall expression of apoptosis in granulosa cells of follicles containing grade 3 COCs (median+/-median absolute deviation: 37.8+/-13.8%) was significantly higher (P<0.05) than in follicles with grade 1 (22.7+/-10.4%) or grade 2 COCs (20.0+/-17.0%). About 48.3% of grade 3 COCs possessed strongly apoptotic cumulus cells compared to 27.8 and 28.2% of grade 1 or grade 2 COCs, respectively. Nonapoptotic cumulus complexes were observed in grades 1 and 2 COCs only.Adding exogenous follicular cells from atretic follicles to bovine COCs (grades 1 and 2) during in vitro maturation (IVM) had no impact on fertilization, blastocyst formation or hatching after IVF. This is of particular practical relevance to embryo production after ovum pick up (OPU), as during this process, good quality COCs are cultured together with simultaneously collected slightly atretic COCs. 相似文献
108.
Checker mallows (Sidalcea, Malvaceae) constitute a western North American genus of annuals and perennials that have been regarded as taxonomically difficult because of complex patterns of morphological variation putatively stemming from hybridization and polyploidy. In recent molecular phylogenetic investigations extensive polymorphism was observed in the internal and external transcribed spacers (ITS and ETS) of 18S-26S nuclear ribosomal DNA for some Sidalcea samples. To resolve the evolutionary basis for this polymorphism and to readdress the evolutionary impact of hybridization in Sidalcea we cloned and sequenced the polymorphic DNAs and included the clones in phylogenetic analyses together with direct sequences of non-polymorphic samples. The positions of cloned spacer sequences in the phylogenetic trees suggest that S. reptans and two subspecies of S. malviflora may have been influenced by past hybridization with lineages of the "glaucescens" clade. Polymorphic sequence patterns in other taxa may be a result of extensive interbreeding within young clades, in keeping with the minimal sequence divergence, largely overlapping geographic distributions and morphology, and ploidy variation in these groups. Other possible explanations for polymorphic sequences in members of Sidalcea include slow concerted evolution relative to mutation rates, incomplete lineage sorting, and recent pseudogene formation. 相似文献
109.
Dijana?Krsti? Teodora?Jankovi? Katarina??avikin-Fodulovi?Email author Neboj?a?Menkovi? Dragoljub?Grubi?i? 《In vitro cellular & developmental biology. Plant》2003,39(2):203-207
Summary The qualitative and quantitative composition of secondary metabolites was studied in the shoots and roots of Centaurium pulchellum cultured in vitro. Secoiridoids (gentiopierin, swertiamarin, and sweroside) and xanthones (methylbellidifolin, demethyleustomin, and deccussatin)
were isolated. Sweroside was found to be the major secoiridoid compound in the aerial parts of plants growing in nature. while
swertiamarin dominated in plants cultured in vitro. In roots of all plants, genciopicrin was the major compound. Xanthone demethyleustomin was the major compound both in the
shoots and roots of plants growing in nature and cultured in vitro. Different sugars (glucose, fructose, and sucrose) added in different concentrations in the medium affected the production
of secondary compounds. 相似文献
110.
Ruta Aldonyte Lennart Jansson Eeva Piitulainen Sabina Janciauskiene 《Respiratory research》2003,4(1):1-8