全文获取类型
收费全文 | 14699篇 |
免费 | 1240篇 |
国内免费 | 25篇 |
出版年
2022年 | 104篇 |
2021年 | 213篇 |
2020年 | 140篇 |
2019年 | 169篇 |
2018年 | 258篇 |
2017年 | 223篇 |
2016年 | 305篇 |
2015年 | 425篇 |
2014年 | 547篇 |
2013年 | 856篇 |
2012年 | 809篇 |
2011年 | 777篇 |
2010年 | 466篇 |
2009年 | 448篇 |
2008年 | 646篇 |
2007年 | 690篇 |
2006年 | 628篇 |
2005年 | 655篇 |
2004年 | 605篇 |
2003年 | 573篇 |
2002年 | 575篇 |
2001年 | 442篇 |
2000年 | 480篇 |
1999年 | 439篇 |
1998年 | 173篇 |
1997年 | 147篇 |
1996年 | 136篇 |
1995年 | 158篇 |
1994年 | 140篇 |
1993年 | 145篇 |
1992年 | 344篇 |
1991年 | 245篇 |
1990年 | 261篇 |
1989年 | 257篇 |
1988年 | 363篇 |
1987年 | 221篇 |
1986年 | 184篇 |
1985年 | 173篇 |
1984年 | 133篇 |
1983年 | 128篇 |
1982年 | 89篇 |
1981年 | 96篇 |
1979年 | 107篇 |
1978年 | 91篇 |
1977年 | 63篇 |
1976年 | 65篇 |
1975年 | 64篇 |
1974年 | 89篇 |
1973年 | 67篇 |
1972年 | 63篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
Paradoxical decrease of an adipose-specific protein, adiponectin, in obesity 总被引:189,自引:0,他引:189
942.
Yamazaki T Yahagi S Nakamura K Yamane K 《Biochemical and biophysical research communications》1999,258(1):211-214
Small cytoplasmic RNA (scRNA) is a metabolically stable homologue of mammalian SRP RNA that contains an Alu-like domain. The Bacillus subtilis histone-like protein HBsu can bind this domain. We demonstrate here that repressing the level of HBsu results in slow growth and the accumulation of precursor of beta-lactamase fusion proteins having the signal sequence of alkaline protease, penicillin binding protein 5* (PBP5*) or CGTase. The degree of the translocation defect varied among the various signal sequences tested. A pulse-chase experiment showed that processing the alpha-amylase signal sequence is significantly inhibited in HBsu-depleted cells. Northern blot analysis indicated that repressing the HBsu gene induces scRNA upregulation, indicating that the defective translocation of presecretory proteins is not due to a reduced scRNA level. The data presented here suggest that HBsu plays a pivotal role in SRP function rather than simply stabilizing the other SRP components such as scRNA. 相似文献
943.
944.
Effects of transforming growth factor-beta signaling on chondrogenesis in mouse chondrogenic EC cells, ATDC5 总被引:6,自引:0,他引:6
Kawai J Akiyama H Shigeno C Ito H Konishi J Nakamura T 《European journal of cell biology》1999,78(10):707-714
Cellular condensation of chondroprogenitors is a distinct cellular event in chondrogenesis. During this process, N-cadherin mediates cell-cell interactions responsible for the initial stage of cellular condensation and subsequently fibronectin contributes to cell-matrix interactions mediating a progression of chondrogenesis. We previously showed that chondrogenesis in mouse chondrogenic EC cells, ATDC5, was induced, at a high incidence in the presence of insulin, through formation of cellular condensation. In this study, we took advantage of the sequential progression of chondrogenesis in ATDC5 cells and evaluated, in vitro in these cells, the role of endogenous transforming growth factor (TGF)-beta in chondrogenesis. ATDC5 cells expressed TGF-beta2 mRNA at a cellular condensation stage. The treatment of undifferentiated ATDC5 cells with anti-TGF-beta32 neutralizing antibody inhibited the accumulation of Alcian blue stainable proteoglycan in a dose-dependent manner. Transfection of a dominant-negative mutant of mouse TGF-beta type II receptor to undifferentiated ATDC5 cells completely inhibited cellular condensation. Moreover, exogenously administered TGF-beta2 upregulated the expression of fibronectin and type II collagen (a phenotypic marker gene of chondrogenesis) mRNAs and downregulated that of N-cadherin mRNA in time- and dose-dependent manners. These results indicate that TGF-beta stimulates chondrogenesis via initiation of cellular condensation by transition from an initial N-cadherin-contributing stage to a fibronectin-contributing stage during processes of chondrogenesis in ATDC5 cells. 相似文献
945.
Small cell carcinoma is a rare neoplasm in the esophagus. To evaluate cell proliferation activity and its underlying mechanisms in this tumor, we examined immunohistochemically 5 cases of small cell carcinoma of the esophagus (SCCE) for expressions of tumor suppressor proteins, oncoproteins and cell proliferation markers including p53, p21WAF1/CIP1, retinoblastoma (Rb) protein, bcl-2, Ki-67 and PCNA, and compared the results with those of 5 cases of small cell carcinoma of the lung (SCCL) and 10 cases of squamous cell carcinoma of the esophagus (SQCE). The prevalence and labeling index of p53-immunoreactivity tended to be higher in SCCE (4/5; 56.6%) and SCCL (4/5; 79.9%) than in SQCE (6/10; 48.8%). Expression of p21WAF1/CIP1 was observed in 2 of 10 cases of SQCE. In contrast, its expression could not be detected in any cases of SCCE and SCCL examined. Expression of Rb protein was observed in 9 out of 10 cases of SQCE, but not in any cases of SCCE and SCCL. SCCE and SCCL showed more frequent and intense immunoreactivity for bcl-2 than SQCE. In expression of cell proliferation markers (Ki-67 and PCNA), no remarkable difference was observed among SCCE, SCCL and SQCE. These results suggest that SCCE and SCCL could share some genetic alternations including mutation of p53, loss of Rb gene and overexpression of bcl-2, and these may be related to the similar biological potentials between the two. Furthermore, SCCE was different from SQCE in expression of Rb protein and bcl-2, and these two types of esophageal carcinoma could arise through different molecular mechanisms. 相似文献
946.
947.
Cryosections and whole-mount preparations of the guinea pig small intestine and colon were single or double immunolabeled
using the anti-c-Kit and protein gene product 9.5 antibodies. Immunolabeled specimens were observed under a confocal laser
scanning microscope. The main findings of the present study are: (1) the distribution and profiles of three-dimensional structures
of c-Kit-positive cellular networks in the small intestine and colon, and (2) the anatomical relations of c-Kit-positive cells
to the enteric nerves in the layers. In the small intestine, c-Kit-positive cellular networks were observed at levels of the
deep muscular plexus and myenteric plexus. The c-Kit-positive cellular networks ran along or overlay the nerve fibers at the
deep muscular plexus, while they showed the reticular structures intermingled with the nerve elements at the myenteric plexus.
In the colon, c-Kit-positive cellular networks were observed at levels of the submuscular plexus and myenteric plexus, and
were further identified within the circular and longitudinal muscle layers as well as in the subserosal layer. In the circular
muscle layer, c-Kit-positive cells surrounded the associated nerve fibers and extended several long processes toward the adjacent
c-Kit-positive cells. The c-Kit-positive cellular networks within the longitudinal muscle layer as well as in the subserosal
layer were not associated with the nerve fibers. In the layers of the intestinal wall with c-Kit-positive cells, the cellular
networks of the interstitial cells were identified in ultrastructure. The characteristic profiles of c-Kit-positive cellular
networks provide a morphological basis upon which to investigate the mechanisms regulating intestinal movement.
Received: 14 July 1998 / Accepted: 2 September 1998 相似文献
948.
Zeller R Haramis AG Zuniga A McGuigan C Dono R Davidson G Chabanis S Gibson T 《Cell and tissue research》1999,298(1):85-93
Formin was originally isolated as the gene affected by the murine limb deformity (ld) mutations, which disrupt the epithelial-mesenchymal interactions regulating patterning of the vertebrate limb autopod. More
recently, a rapidly growing number of genes with similarity to formin have been isolated from many different species including fungi and plants. Genetic and biochemical analysis shows that formin family members function in cellular processes regulating either cytokinesis and/or cell polarisation. Another common feature
among formin family members is their requirement in morphogenetic processes such as budding and conjugation of yeast, establishment of
Drosophila oocyte polarity and vertebrate limb pattern formation. Vertebrate formins are predominantly nuclear proteins which control polarising activity in limb buds through establishment of the SHH/FGF-4
feedback loop. Formin acts in the limb bud mesenchyme to induce apical ectodermal ridge (AER) differentiation and FGF-4 expression in the posterior
AER compartment. Finally, disruption of the epithelial-mesenchymal interactions controlling induction of metanephric kidneys
in ld mutant embryos indicates that formin might function more generally in transduction of morphogenetic signals during embryonic pattern formation.
Received: 24 September 1998 / Accepted: 30 September 1998 相似文献
949.
950.