首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1812篇
  免费   96篇
  国内免费   1篇
  2021年   20篇
  2020年   9篇
  2019年   14篇
  2018年   15篇
  2016年   28篇
  2015年   49篇
  2014年   47篇
  2013年   158篇
  2012年   84篇
  2011年   71篇
  2010年   36篇
  2009年   40篇
  2008年   73篇
  2007年   78篇
  2006年   69篇
  2005年   68篇
  2004年   70篇
  2003年   73篇
  2002年   60篇
  2001年   57篇
  2000年   79篇
  1999年   65篇
  1998年   21篇
  1997年   18篇
  1996年   15篇
  1995年   15篇
  1994年   11篇
  1993年   17篇
  1992年   44篇
  1991年   43篇
  1990年   42篇
  1989年   53篇
  1988年   38篇
  1987年   44篇
  1986年   24篇
  1985年   30篇
  1984年   13篇
  1983年   14篇
  1982年   20篇
  1981年   10篇
  1980年   8篇
  1979年   22篇
  1978年   15篇
  1977年   18篇
  1976年   16篇
  1975年   14篇
  1974年   9篇
  1973年   8篇
  1971年   9篇
  1969年   8篇
排序方式: 共有1909条查询结果,搜索用时 15 毫秒
11.
ICGN is a strain of spontaneous nephrotic mice with nonproliferative glomerular lesions. It was derived from an outbred Yok: ICR colony in our laboratory. The renal disease constantly occurred in animals of the first to the tenth generations (greater than 13.0%; 70 days of age). When affected males were mated with unaffected females, the incidence of the disease in their offspring was 38.8% (n = 49) at 70 days after birth. When both parents were affected, their offspring were all affected (n = 12). The disease evenly progressed in both sexes. It usually began 40 to 150 days after birth and death occurred within two months after onset. The animals usually showed sufficient reproductive ability as long as unaffected females were used for mating.  相似文献   
12.
A 43-year-old woman with isolated ACTH deficiency in association with transient thyrotoxicosis is reported. The initial evaluation revealed that plasma ACTH and cortisol did not respond to corticotropin-releasing hormone (CRH) in the presence of hyperthyroxinemia and hyperprolactinemia. During the replacement therapy with dexamethasone, she developed transient hypothyroxinemia with persistent hyperprolactinemia. Although thyroid open biopsy did not show any evidence of autoimmune thyroiditis or subacute thyroiditis, the data appear to provide other evidence of a possible relationship between acute adrenal insufficiency and transient thyroid dysfunction.  相似文献   
13.
Conditioned medium of a human bladder carcinoma cell line (J82) was found to induce tissue factor synthesis in cultured human umbilical vein endothelial cells (HUVEC). A protein present in the J82 conditioned medium was partially purified by FPLC using a combination of MONO Q and Superose 6 columns. The bladder carcinoma-derived cytokine (BCDC) exhibited a Mr of 22 kDa by gel permeation HPLC. Polyclonal antibody against either interleukin-1, tumor necrosis factor, or transforming growth factor-beta failed to inhibit the ability of the conditioned medium to induce HUVEC tissue factor activity, suggesting that this tumor cell line secretes a novel cytokine responsible for HUVEC tissue factor induction.  相似文献   
14.
Cloned cDNA encoding the so-far uncharacterized alpha-3 subunit of rat brain Na+,K+-ATPase (Hara et al. (1987) J. Biochem. 102, 43-58, Shull et al. (1986) Biochemistry 25, 8125-8132) was incorporated into a vector carrying the SP6 promoter. The mRNA produced in vitro was injected into Xenopus oocytes with the mRNA encoding the Na+,K+-ATPase beta subunit of Torpedo electroplax. Increased Na+,K+-ATPase activity in the oocyte membrane was observed. This newly expressed activity was inhibited by ouabain (Ki = 1.5 x 10(-7) M), suggesting that the alpha-3 subunit of rat brain Na+,K+-ATPase is a highly ouabain-sensitive catalytic subunit.  相似文献   
15.
1H NMR spectra of a GDP/GTP-binding domain of human c-Ha-ras gene product (residues 1-171) in which glutamine-61 was replaced by leucine [ras(L61/1-171) protein] were analyzed. By one-dimensional and two-dimensional homonuclear Hartmann-Hahn spectroscopy and nuclear Overhauser effect (NOE) spectroscopy of the complex of the ras(L61/1-171) protein and GDP, the ribose H1', H2', H3', and H4' proton resonances of the bound GDP were identified. The guanine H8 proton resonance of the bound GDP was identified by substituting [8-2H]GDP for GDP. The dependences of the H1' and H8 proton resonance intensities on the duration of irradiation of the H1', H2', H3', and H8 protons were measured. By numerical simulation of these time-dependent NOE profiles, the conformation of the protein-bound GDP was elucidated; the guanosine moiety takes the anti form about the N-glycosidic bond with a dihedral angle of chi = -124 +/- 2 degrees and the ribose ring takes the C2'-endo form. Such an analysis of the conformation of a guanine nucleotide as bound to a GTP-binding protein will be useful for further studies on the molecular mechanism of the conformational activation of ras proteins on ligand substitution of GDP with GTP.  相似文献   
16.
Summary There have been few reports stating that monoclonal antibody alone inhibits human solid tumor growth in vivo. The present study demonstrated that monoclonal antibody S1 (IgG2a), which recognized the antigenic determinant of the carbohydrate moiety, showed antibody-dependent cell (or macrophage)-mediated cytotoxicity (ADCC or ADMC) in conjunction with murine splenocytes of both BALB/c and athymic mice. In vivo experiments demonstrated that the antibody S1 clearly prolonged the survival of athymic mice which had been inoculated with a human liver carcinoma cell line. In addition, the antibody S1 significantly suppressed the human hepatoma line transplanted s.c. into nude mice. 125I-Labeled monoclonal antibody S1 revealed that the antibody accumulated significantly in the tumor mass. Many mononuclear cells were observed surrounding tumor cells when the antibody was given. This model system might be useful for analyzing the ADCC (or ADMC) mechanism in vivo.  相似文献   
17.
A cell line (JAMH17+) resistant to 8-azaguanine was established from a human T-cell leukemia virus type 1 related virus (simian T-cell leukemia virus-1) positive Japanese macaque cell line. Lymphoblastic cell lines were established from the peripheral blood mononuclear cells of humans, hominoids, and several species of macaques by coculture with JAMH17+ in hypoxanthine-aminopterin-thymidine medium. HTLV-1 specific antigen was detected in some of the established cell lines. Phenotypic analysis showed that several cell lines of crab-eating macaques expressed Leu11a antigen, which is a marker of human natural killer cells.  相似文献   
18.
The subcellular distribution of asparagine:oxo-acid aminotransferase (EC 2.6.1.14) in rat liver was examined by centrifugation in a sucrose density gradient. About 30% of the homogenate activity after the removal of the nuclear fraction was recovered in the peroxisomes, about 56% in the mitochondria, and the remainder in the soluble fraction from broken peroxisomes. The mitochondrial asparagine aminotransferase had identical immunological properties with the peroxisomal one. Glucagon injection to rats resulted in the increase of its activity in the mitochondria but not in the peroxisomes. Immunological evidence was obtained that the enzyme was identical with alanine:glyoxylate aminotransferase 1 (EC 2.6.1.44) which had been reported to be identical with serine:pyruvate aminotransferase (EC 2.6.1.51) (Noguchi, T. (1987) in Peroxisomes in Biology and Medicine (Fahimi, H. D., and Sies, H., eds) pp. 234-243, Springer-Verlag, Heidelberg). The same results as described above were obtained with mouse liver. All of alanine:glyoxylate aminotransferase 1 in livers of mammals other than rodents, which cross-react with the antibody against rat liver alanine:glyoxylate aminotransferase 1, had no asparagine aminotransferase activity.  相似文献   
19.
We have determined the genomic structure of the fosB gene and shown that it consists of 4 exons and 3 introns at positions also found in the c-fos gene. By deletion analysis we have characterized a region upstream of the TATA box which is the promoter region of the gene. Several consensus sequences have been identified, including an SRE and AP-1 binding site whose relative positions are identical to those in the 5' upstream region of the c-fos gene. We have also shown that FosB and c-Fos can downregulate the activity of the fosB promoter to a similar extent. The fosB gene is located in the [A1-B1] region of mouse chromosome 7.  相似文献   
20.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号