全文获取类型
收费全文 | 10461篇 |
免费 | 961篇 |
国内免费 | 3篇 |
专业分类
11425篇 |
出版年
2021年 | 121篇 |
2020年 | 103篇 |
2019年 | 130篇 |
2018年 | 139篇 |
2017年 | 109篇 |
2016年 | 170篇 |
2015年 | 301篇 |
2014年 | 328篇 |
2013年 | 418篇 |
2012年 | 520篇 |
2011年 | 518篇 |
2010年 | 319篇 |
2009年 | 289篇 |
2008年 | 455篇 |
2007年 | 399篇 |
2006年 | 399篇 |
2005年 | 397篇 |
2004年 | 424篇 |
2003年 | 365篇 |
2002年 | 388篇 |
2001年 | 189篇 |
2000年 | 140篇 |
1999年 | 165篇 |
1998年 | 141篇 |
1997年 | 113篇 |
1996年 | 133篇 |
1995年 | 99篇 |
1994年 | 101篇 |
1993年 | 105篇 |
1992年 | 139篇 |
1991年 | 128篇 |
1990年 | 141篇 |
1989年 | 127篇 |
1988年 | 120篇 |
1987年 | 115篇 |
1986年 | 110篇 |
1985年 | 136篇 |
1984年 | 114篇 |
1983年 | 130篇 |
1982年 | 116篇 |
1981年 | 104篇 |
1980年 | 114篇 |
1979年 | 77篇 |
1978年 | 98篇 |
1977年 | 101篇 |
1976年 | 72篇 |
1974年 | 103篇 |
1973年 | 80篇 |
1972年 | 87篇 |
1971年 | 73篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
Granulocyte-mediated airway edema in guinea pigs 总被引:2,自引:0,他引:2
Sheppard D.; Scypinski L.; Horn J.; Gordon T.; Thompson J. E. 《Journal of applied physiology》1986,60(4):1213-1220
To determine the role of polymorphonuclear leukocytes (PMNs) in the airway edema that accompanies airway inflammation, we studied the effects of a 1-h exposure to 2 ppm toluene diisocyanate (TDI) on tracheal extravasation of Evans blue dye and on the concentration of PMNs in the tracheal wall. Tracheal Evans blue content was significantly increased by TDI exposure (53.6 +/- 8.0 micrograms/g tracheal tissue (mean +/- SE) for animals exposed to TDI and 16.3 +/- 2.0 for animals exposed to air, P less than 0.0025) as were both the intravascular and extravascular concentration of PMNs in tracheal sections (intravascular PMNs were 28.0 +/- 8.4 X 10(3) cells/mm3 for TDI and 1.5 +/- 1.5 X 10(3) for air, P less than 0.025, extravascular PMNs were 10.9 +/- 4.5 X 10(3) for TDI and 0 for air, P less than 0.05). PMN depletion with vinblastine or with hydroxyurea abolished both the increase in tracheal Evans blue extravasation and the increase in the concentration of intravascular and extravascular PMNs in animals exposed to TDI. PMN depletion with hydroxyurea did not significantly inhibit the increase in tracheal Evans blue extravasation caused by intravenous histamine. Administration of donor PMNs to animals depleted of PMNs with hydroxyurea reconstituted the TDI-induced increase in tracheal Evans blue extravasation (80.4 +/- 17.3 micrograms/g tissue (mean +/- SE) in animals exposed to TDI vs. 21.3 +/- 2.9 in animals exposed to air, P less than 0.025) and in the intravascular concentration of PMNs in tracheal sections [18.5 +/- 3.4 X 10(3) cells/mm3 (mean +/- SE) in animals exposed to TDI vs. 1.3 +/- 1.3 X 10(3) in animals exposed to air, P less than 0.0025].(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
82.
Antigenic structure of histone H2B 总被引:3,自引:0,他引:3
S Muller M Couppez J P Briand J Gordon P Sautière M H van Regenmortel 《Biochimica et biophysica acta》1985,827(3):235-246
Antigenic determinants of histone H2B were localized using a series of 23 overlapping fragments of H2B obtained either by chemical and enzymatic cleavage of the histone or by solid-phase peptide synthesis. The ability of peptides to bind H2B antibodies was measured in an enzyme-linked immunosorbent assay, using antisera directed against calf thymus and chicken erythrocyte H2B as well as four anti H2B monoclonal antibodies obtained from autoimmune mice. Seven antigenic determinants were localized in the H2B molecule in the vicinity of residues 1-11, 6-18, 15-25, 26-35, 50-65, 94-113 and 114-125. Two of these determinants (residues 6-18 and 26-35) were revealed only through the binding properties of antibodies isolated from autoimmune mice. The usual correlation between hydrophilicity and antigenicity was found to hold for four of the epitopes, and the N- and C-termini of H2B were both antigenically active. 相似文献
83.
Roy Greenhalgh J. David Miller Gordon A. Neish H. Bruno Schiefer 《Applied microbiology》1985,50(2):550-552
The isolation and characterization of 10 isolates of six Fusarium spp. from plant and soil samples collected in Southeast Asia is reported. The ability of these isolates to produce trichothecenes both in liquid cultures (CZ, GYEP, and MYRO) and on rice was assessed, and their toxigenic potential was examined by skin assay and gavage studies with culture filtrates. Although culture filtrates of all the isolates caused minor damage to test animals, only that of F. equiseti DAOM 189762 produced trichothecenes. 相似文献
84.
Amidation of C3 at the thiolester site: stimulation of chemiluminescence and phagocytosis by a new inflammatory mediator 总被引:4,自引:0,他引:4
D L Gordon R A Krueger P G Quie M K Hostetter 《Journal of immunology (Baltimore, Md. : 1950)》1985,134(5):3339-3345
We studied the ability of particle-bound and fluid-phase C3b monomers and monomeric amidated C3 (prepared by treatment of purified human C3 with ammonium chloride or methylamine) to stimulate chemiluminescence of human polymorphonuclear leukocytes (PMN) and monocytes and to promote phagocytosis in the absence of antibody. Particle-bound C3b evoked chemiluminescence from both PMN and monocytes, and fluid-phase C3b (0.5 mg/ml) elicited significant chemiluminescence from PMN but not from monocytes. Amidated forms of C3, both particle bound and fluid phase, were potent stimulators of chemiluminescence from phagocytic cells and caused a significantly greater response than did C3b. The phagocytosis of 1-micron microspheres by PMN and monocytes was enhanced by coating them with purified C3b in an antibody-free system. Microspheres coated with amidated C3 were avidly phagocytized, and to a greater degree than were C3b-coated microspheres. In a direct binding assay with tritiated monomeric C3b and amidated C3, the affinity of the PMN complement receptor type 1 for C3b (Ka = 4.9 X 10(7) L/M) was similar to that for amidated C3 (Ka = 5.7 X 10(7) L/M). However, there was a fourfold increase in the number of apparent binding sites for amidated C3. This increase did not reflect binding of amidated C3 to the complement receptor type 3, because blocking of CR3 with the monoclonal antibody OKM 10 failed to decrease binding of amidated C3. In sites of increased ammoniagenesis, such as the kidney in chronic renal failure, amidated C3 may play a role as an inflammatory mediator by stimulating oxidative metabolism in phagocytic cells. 相似文献
85.
Murine polyspecific antibodies. I. Monoclonal and serum anti-DNA antibodies cross-reactive with 2,4,6-trinitrophenyl derivatives 总被引:7,自引:0,他引:7
D Serban C Rordorf-Adam Y Z Sun J Gordon 《Journal of immunology (Baltimore, Md. : 1950)》1985,135(5):3122-3127
Six anti-DNA hybridoma autoantibodies were prepared by fusing spleen cells from unimmunized MRL/MpJ/lpr/lpr female mice with BALB/c myeloma cells. The monoclonal antibodies were analyzed by solid-phase ELISA for antigen-binding specificities. Three antibodies (62A2, 85A5, and 43B2) bound ssDNA, TNP-KLH, and recognized an epitope(s) present on insolubilized proteins such as BSA, KLH, ferritin, and insulin. The antibodies bound, with a marked preference, TNP-KLH, either soluble or insoluble. The other three antibodies (35A1, 32C5, and 39D2) bound only ssDNA. However, this binding was inhibited by free flavinic acid. None of the six antibodies bound either cardiolipin or proteoglycans, indicating that they do not recognize the repeating negatively charge units common to cardiolipin, proteoglycans, and DNA. All six monoclonal antibodies were purified by affinity chromatography with TNP-Sepharose. Moreover, both anti-DNA and anti-TNP antibodies from sera of nonautoimmune and autoimmune mice were purified easily on TNP-Sepharose. 相似文献
86.
D P Snider J Gordon M R McDermott B J Underdown 《Journal of immunology (Baltimore, Md. : 1950)》1985,134(6):4153-4162
To investigate the role of B cells and antibody in the immune response of mice to the murine intestinal parasite Giardia muris, we used mice treated from birth with rabbit anti-IgM antisera (aIgM). Such mice developed in serum and in gut secretions extreme Ig deficiency (IgM, IgA, and IgG) relative to control animals. The aIgM-treated mice showed no anti-G. muris antibody in serum or in gut wash material. Infections of G. muris in these mice were chronic, with a high load of parasite present in the small bowel, as reflected by prolonged cyst excretion (greater than 11 wk) and high trophozoite counts. In contrast, normal, untreated mice or NRS-treated animals developed anti-parasite IgA and IgG antibody in serum, demonstrated IgA antibody against the parasite in gut washings, and expelled the parasite within 9 wk. These effects of aIgM treatment on the murine response to primary infection with G. muris were demonstrated in two strains of mice: BALB/c and (C57BL/6 X C3H/He) F1. It was also observed that the response to G. muris infection in untreated animals was characterized by higher than normal total secretion of IgA into the gut and a concomitant increase in the serum polymeric IgA level. Mice treated with aIgM had a marked decrease of both monomeric and polymeric IgA in serum, and little detectable IgA in the intestinal lumen. These experiments provide the first demonstration that anti-IgM treatment suppresses a specific intestinal antibody response to antigen, and provide evidence that B cells and antibody play a role in the development of an effective response to a primary infection with G. muris in mice. 相似文献
87.
Summary A model has been developed for 5-nitroxide stearate, I(12,3), distribution in human erythrocyte ghosts which accurately predicts ESR spectral alterations observed with increased probe/total lipid (P/L) at 37°C. This spin probe occupies a class of high-affinity, noninteracting sites at low loading. Saturation occurs with increasing probe concentration, and, at higher loading, the probe inserts itself at initially dilute sites to form membranebound clusters of variable size. No low probe remains at high P/L where all I(12,3) clusters in a concentrated phase. This model allows determination of the dilute/clustered probe ratio, and shows that I(12,3) segregates in erythrocytes at what might otherwise be considered low P/L (e.g., 1/359). These findings validate the earlier use of empirical parameters to estimate probe sequestration in biological membranes. 相似文献
88.
Gordon Parry Eva Y. -H. Lee Deborah Farson Mike Koval Mina J. Bissell 《Experimental cell research》1985,156(2):487-499
We have investigated the influence of culture substrata upon glycosaminoglycans produced in primary cultures of mouse mammary epithelial cells isolated from the glands of late pregnant mice. Three substrata have been used for experiments: tissue culture plastic, collagen (type I) gels attached to culture dishes, and collagen (type I) gels that have been floated in the culture medium after cell attachment. These latter gels contract significantly. Cells cultured on all three substrata produce hyaluronic acid, heparan sulfate, chondroitin sulfates and dermatan sulfate but the relative quantities accumulated and their distribution among cellular and extracellular compartments differ according to the nature of the culture substratum. Notably most of the glycosaminoglycans accumulated by cells on plastic are secreted into the culture medium, while cells on floating gels incorporate almost all their glycosaminoglycans into an extracellular matrix fraction. Cells on attached collagen gels secrete approx. 30% of their glycosaminoglycans and assemble most of the remainder into an extracellular matrix. Hyaluronic acid is produced in significant quantities by cells on plastic and attached gels but in relatively reduced quantity by cells on floating gels. In contrast, iduronyl-rich dermatan sulfate is accumulated by cells on floating gels, where it is primarily associated with the extracellular matrix fraction, but is proportionally reduced in cells on plastic and attached gels. The results are discussed in terms of polarized assembly of a morphologically distinct basal lamina, a process that occurs primarily when cells are on floating gels. In addition, as these cultures secrete certain milk proteins only when cultured on floating gels, we discuss the possibility that cell synthesized glycosaminoglycans and proteoglycans may play a role in the maintenance of a differentiated phenotype. 相似文献
89.
Autophagic sequestration of [14C]sucrose introduced into isolated rat hepatocytes by electrical and non-electrical methods 总被引:2,自引:0,他引:2
Isolated rat hepatocytes were found to become permeable to [14C]sucrose at 0 degree C under three different conditions: Immediately following their liberation from the collagenase-perfused liver. Following a short incubation under hypoxic conditions. After electropermeabilisation. All three conditions were characterised by the formation of small protuberances (blebs) indicative of localised cell surface damage, and it is possible that the stretched plasma membrane of such blebs acted as a high-permeability region. Disappearance of blebs and restoration of normal plasma membrane impermeability could be achieved by a short (15 min) incubation at 37 degrees C. It could be shown that [14C]sucrose introduced into rat hepatocytes by non-electrical means was autophagically sequestered at the same rate as [14C]sucrose introduced electrically. In both cases the sequestration was inhibited by the specific autophagy inhibitor 3-methyladenine to a similar extent. The subcellular distribution of sequestered isotope in metrizamide/sucrose density gradients was found to be independent of the conditions of its introduction into cells. 相似文献
90.
Limited-host-range plasmid of Agrobacterium tumefaciens: molecular and genetic analyses of transferred DNA. 总被引:9,自引:4,他引:5 下载免费PDF全文
A tumor-inducing (Ti) plasmid from a strain of Agrobacterium tumefaciens that induces tumors on only a limited range of plants was characterized and compared with the Ti plasmids from strains that induce tumors on a wide range of plants. Whereas all wide-host-range Ti plasmids characterized to date contain closely linked oncogenic loci within a single transferred DNA (T-DNA) region, homology to these loci is divided into two widely separated T-DNA regions on the limited-host-range plasmid. These two plasmid regions, TA-DNA and TB-DNA, are separated by approximately 25 kilobases of DNA which is not maintained in the tumor. The TA-DNA region resembles a deleted form of the wide-host-range TL-DNA and contains a region homologous to the cytokinin biosynthetic gene. However, a region homologous to the two auxin biosynthetic loci of the wide-host-range plasmid mapped within the TB-DNA region. These latter genes play an important role in tumor formation because mutations in these loci result in a loss of virulence on Nicotiana plants. Furthermore, the TB-DNA region alone conferred tumorigenicity onto strains with an intact set of vir genes. Our results suggest that factors within both the T-DNA and the vir regions contribute to the expression of host range in Agrobacterium species. There was a tremendous variation among plants in susceptibility to tumor formation by various A. tumefaciens strains. This variation occurred not only among different plant species, but also among different varieties of plants within the same genus. 相似文献