全文获取类型
收费全文 | 28935篇 |
免费 | 3691篇 |
国内免费 | 3篇 |
出版年
2021年 | 260篇 |
2018年 | 289篇 |
2017年 | 261篇 |
2016年 | 477篇 |
2015年 | 758篇 |
2014年 | 832篇 |
2013年 | 1069篇 |
2012年 | 1301篇 |
2011年 | 1202篇 |
2010年 | 774篇 |
2009年 | 744篇 |
2008年 | 1103篇 |
2007年 | 1088篇 |
2006年 | 1004篇 |
2005年 | 967篇 |
2004年 | 946篇 |
2003年 | 949篇 |
2002年 | 918篇 |
2001年 | 918篇 |
2000年 | 912篇 |
1999年 | 771篇 |
1998年 | 398篇 |
1997年 | 374篇 |
1996年 | 350篇 |
1995年 | 319篇 |
1994年 | 320篇 |
1993年 | 334篇 |
1992年 | 682篇 |
1991年 | 630篇 |
1990年 | 611篇 |
1989年 | 661篇 |
1988年 | 563篇 |
1987年 | 603篇 |
1986年 | 476篇 |
1985年 | 565篇 |
1984年 | 479篇 |
1983年 | 385篇 |
1982年 | 399篇 |
1981年 | 358篇 |
1980年 | 328篇 |
1979年 | 435篇 |
1978年 | 382篇 |
1977年 | 339篇 |
1976年 | 313篇 |
1975年 | 334篇 |
1974年 | 381篇 |
1973年 | 361篇 |
1972年 | 306篇 |
1971年 | 285篇 |
1970年 | 247篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
3.
4.
5.
6.
A polymorphism was identified in the bovine butyrophilin (BTN) gene by digesting poly-merase chain reaction products with the restriction enzyme Hae III. This polymorphism was segregating in a Holstein-Friesian sire selected as part of an ongoing study directed towards the identification of quantitative trait loci affecting milk composition. Screening of a half-sib family established for the heterozygous sire allowed the localization of BTN to bovine chromosome 23 (BTA23). 相似文献
7.
8.
D H Broide C M Smith S I Wasserman 《Journal of immunology (Baltimore, Md. : 1950)》1990,145(6):1838-1844
As elevated bronchoalveolar lavage (BAL) fluid histamine levels are noted in patients with pulmonary fibrosis (PF), we assayed BAL fluid from 16 patients with PF for the presence of a histamine releasing factor (HRF). HRF activity was assayed by measuring release of the preformed mast cell-derived mediators, histamine, or beta-hexosaminidase (beta-hex) from a purified population of IL-3 dependent mouse bone marrow derived mast cells (MBMMC) or human blood basophils. Mean BAL cell free histamine levels in the patients with PF was 1226 +/- 1349 pg/ml, whereas BAL histamine levels in a comparison group of six non-PF patients was 118 +/- 60 pg/ml. HRF was significantly elevated in BAL fluid of patients with PF (mean beta-hex release 24.5 +/- 12.9%; range 6.8 to 52.4%) compared to the non-PF group of patients (mean beta-hex release 7.9 +/- 7.7%; range 1.8 to 20.7%). The PF HRF not only degranulated MBMMC, but also induced the generation of the arachidonic acid metabolite leukotriene C4 from MBMMC (24.6 +/- 4.2 ng leukotriene C4/10(6) MBMMC). The PF HRF did not appear to be a cytokine previously identified in BAL fluid of patients with PF (i.e., platelet derived growth factor or insulin growth factor-1) or a human cytokine able to degranulate human basophils (i.e., IL-1, or granulocyte-macrophage-CSF) as these recombinant human cytokines did not induce MBMMC beta-hex release. Physicochemical characterization of the HRF revealed that it was relatively heat stable, pronase sensitive and on Sephadex G-75 and G-200 column chromatography had an apparent molecular mass of 30 to 50 kDa. The ability of PF BAL to induce beta-hex release from MBMMC was not dependent on IgE as unsensitized or lactic acid treated MBMMC release similar amounts of beta-hex compared to MBMMC sensitized with IgE. Thus, BAL fluid of patients with PF contains an HRF that induces beta-hex release from MBMMC via an IgE-independent mechanism. The presence of the HRF could explain elevated BAL histamine levels in patients with PF. 相似文献
9.
10.
Purification of unactivated progesterone receptor and identification of novel receptor-associated proteins 总被引:14,自引:0,他引:14
Progesterone receptor complexes were purified from crude cytosol in a rapid, gentle, one-step procedure using anti-receptor monoclonal antibodies covalently attached to an agarose resin. Five nonreceptor proteins specifically co-purified with unactivated avian progesterone receptor; these proteins had molecular masses of approximately 90, 70, 54, 50, and 23 kDa. The 90- and 70-kDa proteins have been previously identified as the 90-kDa heat shock protein and a member of the 70-kDa heat shock protein family, respectively. The 54-, 50-, and 23-kDa proteins have not been previously described as associated with avian progesterone receptor. Two-dimensional gel electrophoresis revealed charge heterogeneities for all five proteins. Except for p70, each could be dissociated from receptor by salt, a process inhibited by sodium molybdate. However, molybdate was not required for protein association with receptor in low ionic strength. Following progesterone treatment in vivo p70 still co-purified with cytosolic receptor although the other affiliated proteins were reduced, suggesting hormone-dependent dissociation in conjunction with receptor activation. One of the proteins, p54, displayed in vitro hormone-dependent dissociation which was not prevented by molybdate. 相似文献