全文获取类型
收费全文 | 1561篇 |
免费 | 76篇 |
国内免费 | 27篇 |
专业分类
1664篇 |
出版年
2023年 | 15篇 |
2022年 | 21篇 |
2021年 | 41篇 |
2020年 | 25篇 |
2019年 | 26篇 |
2018年 | 26篇 |
2017年 | 26篇 |
2016年 | 23篇 |
2015年 | 35篇 |
2014年 | 89篇 |
2013年 | 71篇 |
2012年 | 65篇 |
2011年 | 111篇 |
2010年 | 77篇 |
2009年 | 75篇 |
2008年 | 68篇 |
2007年 | 92篇 |
2006年 | 88篇 |
2005年 | 54篇 |
2004年 | 59篇 |
2003年 | 41篇 |
2002年 | 47篇 |
2001年 | 34篇 |
2000年 | 13篇 |
1999年 | 20篇 |
1998年 | 25篇 |
1997年 | 16篇 |
1996年 | 20篇 |
1995年 | 24篇 |
1994年 | 24篇 |
1993年 | 24篇 |
1992年 | 22篇 |
1991年 | 33篇 |
1990年 | 21篇 |
1989年 | 13篇 |
1988年 | 14篇 |
1987年 | 18篇 |
1986年 | 15篇 |
1985年 | 8篇 |
1984年 | 15篇 |
1983年 | 8篇 |
1982年 | 23篇 |
1981年 | 11篇 |
1980年 | 15篇 |
1979年 | 14篇 |
1978年 | 9篇 |
1977年 | 7篇 |
1976年 | 9篇 |
1973年 | 11篇 |
1970年 | 6篇 |
排序方式: 共有1664条查询结果,搜索用时 15 毫秒
21.
Igor M. Samokhvalov 《Cell cycle (Georgetown, Tex.)》2012,11(16):2965-2966
Comment on: Tanaka Y, et al. Proc Natl Acad Sci USA 2012; 109:4515-20. 相似文献
22.
23.
Dr. Jack L. Haar 《Cell and tissue research》1977,184(1):113-119
Summary Mouse visceral yolk sac has been organ cultured from 9 days of gestation, a time prior to the thymus being lymphoid, until 12 days of gestation, a time after which the thymus is lymphoid. During the culture period the endodermal epithelial cells survived well, erythropoiesis diminished, endothelial-lined cavities formed in the mesodermal mass, and cells developed which have been classified as large, medium and small immunocyte precursors. The cytoplasm of the immunocyte precursors contains polysomes, spherical mitochondria, a few profiles of rough endoplasmic reticulum, occasional granules and a large Golgi complex. This study offers morphological support for the yolk sac origin of immunocyte precursors in the mouse which may seed the thymus and liver.Supported by NIH Grant AI 13486-01 相似文献
24.
滋补肾阴方与温补肾阳方对卵巢切除所致骨质疏松大鼠治疗作用的对比研究 总被引:3,自引:1,他引:3
目的 对比观察滋补肾阴方与温补肾阳方对卵巢切除所致骨质疏松大鼠的治疗作用 ,以探讨它们之间的疗效是否存在差异。方法 将雌性Wistar大鼠 4 9只随机分为正常对照组、假手术组、卵巢切除组、滋阴组 (灌服生药含量为 1 0 5g ml的滋补肾阴方 ,按每 10 0g体重 0 7ml剂量 )、补阳组 (灌服生药含量为 0 78g ml的温补肾阳方 ,按每 10 0g体重 0 7ml剂量 )。于造模 3个月后开始给药 ,1次 日 ,连续 6d ,休息一天后 ,再连续灌服 6d。给药 2个月后 ,将大鼠处死 ,取胫骨行不脱钙骨切片 ,甲苯胺蓝染色 ,对其进行骨组织形态计量。结果 切除卵巢 5个月后 ,大鼠胫骨TBV %显著降低 ,TRS %以及TFS %、AFS %、MAR、BFR、OSW和mAR皆显著增高 ,给大鼠灌服滋阴补肾方和温补肾阳方 2个月后 ,均能使上述指标发生逆转 ,但程度有所不同 ,温补肾阳方的效果要明显优于滋补肾阴方。结论 滋补肾阴方与温补肾阳方对卵巢切除所致的骨质疏松均有明显的治疗作用 ,但温补肾阳方的疗效要优于滋阴补肾方。 相似文献
25.
Julien Gonzalez Sofia Mouttalib Christine Delage Denis Calise Jean-José Maoret Jean-Philippe Pradère Julie Klein Bénédicte Buffin-Meyer Betty Van der Veen Israel F. Charo Peter Heeringa Johan Duchene Jean-Loup Bascands Joost-Peter Schanstra 《Biochemical and biophysical research communications》2013
Most end-stage renal disease kidneys display accumulation of extracellular matrix (ECM) in the renal tubular compartment (tubular interstitial fibrosis – TIF) which is strongly correlated with the future loss of renal function. Although inflammation is a key event in the development of TIF, it can also have a beneficial anti-fibrotic role depending in particular on the stage of the pathology. Chemokines play an important role in monocyte extravasation in the inflammatory process. CCL2 has already been shown to be involved in the development of TIF but CCL7, a close relative of CCL2 and able to bind to similar receptors, has not been studied in renal disease. We therefore studied chemokine CCL7 in a model of unilateral ureteral obstruction (UUO)-induced TIF. We observed that the role of CCL7 differs depending on the stage of the pathology. In early stages (0–8 days), CCL7 deficient (CCL7-KO) mice displayed attenuated TIF potentially involving two mechanisms: an early (0–3 days) decrease of inflammatory cell infiltration followed (3–8 days) by a decrease in tubular ECM production independent of inflammation. In contrast, during later stages of obstruction (10–14 days), CCL7-KO mice displayed increased TIF which was again associated with reduced inflammation. Interestingly, the switch between this anti- to profibrotic effect was accompanied by an increased influx of immunosuppressive regulatory T cells. In conclusion, these results highlight for the first time a dual role for CCL7 in the development of renal TIF, deleterious in early stages but beneficial during later stages. 相似文献
26.
27.
《Saudi Journal of Biological Sciences》2022,29(2):831-839
The survival reduction after transplantation limited the clinical uses of stem cells so the current study explored preconditioning adipose-derived stem cells (ADMSCs) and all-trans retinoic acid (ATRA) effects on cisplatin that caused acute kidney injury (AKI). One hundred and fifty Sprague–Dawley male rats were distributed into five groups: control group; Cisplatin (CIS) group; CIS and ATRA group; CIS and ADMSC group, and CIS, ATRA, and ADMSCs group. Ten rats were euthanized after 3rd, 7th, and 11th days from CIS injection. Renal function, molecular studies, and histopathological analysis were studied. The preconditioning of ADMSCs with ATRA increased the viability of the cells which was reflected in the amelioration of kidney functions after CIS injection by the significant reduction of serum creatinine, microalbuminuria, as well as NO, and the significant rise of creatinine clearance, as well as SOD compared to the group of cisplatin. ATRA also supported ADMSCs by a significant down-regulation of caspase-3, il-6 and TGFβ1, and a significant up-regulation of HIF1, VEGF and CD31 compared to group of cisplatin which reversed the cisplatin effect. ATRA increased renoprotective properties of ADMSCs against cisplatin- induced AKI by reducing the apoptosis, inflammation, and stimulating angiogenesis. 相似文献
28.
Syun'iti Iwao 《Population Ecology》1963,5(1):44-50
A method for estimating the rate of population interchange between two areas is described in this paper. It is applicable to the case where the sampling ratios and the survival factors of the populations on two areas are different from each other. From the marking-and-recapture data taken at three successive occasions, we can obtain the estimates of emigration factors, total survival factors over two areas and the ratio of surviving migrants to the total survivors over the two areas, for each of two populations initially living on different areas. 相似文献
29.
The phylogenetic distribution,anatomy and histology of the post‐cloacal bones and adnexa of geckos 下载免费PDF全文
Post‐cloacal bones of gekkotans may be present as a single (medial) pair, two pairs (medial and lateral), or may be lacking. We, herein, demonstrate that the presence of a single medial pair is the ancestral condition for the Gekkota, that the lateral pair is of sporadic occurrence within and between families, except for the Eublepharidae where it is universal, and that absence is also of sporadic occurrence except for the Sphaerodactylidae where it is the ancestral condition. Adult male Tokay geckos (Gekko gecko) possess only the medial pair of bones, and these exhibit a regionally‐specific expression of woven, fibrolamellar, and lamellar bone, and an enclosed medullary cavity. Females and small juvenile males lack bony elements but exhibit a conspicuous band of dense connective tissue located about the anterior and lateral margins of the cloacal sacs. As males grow and attain sexual maturity, the medial post‐cloacal bones condense in this band of dense connective tissue, and are thus shown to be dermal ossifications, similar to osteoderms but with muscular associations (although this is also known for crocodylians). Based upon ontogenetic data we set forth a scenario to explain the loss of the medial post‐cloacal bones in various lineages. Differential staining of the cloacal sacs failed to reveal any specialized glandular structures. Investigation of the post‐cloacal spurs shows them to be associated with cellular connective tissue of a type similar to that found in the vicinity of the medial post‐cloacal bones. This suggests that the lateral post‐cloacal bones may also be dermal bones, but histological evidence is needed to corroborate this. J. Morphol. 277:264–277, 2016. © 2015 Wiley Periodicals, Inc. 相似文献
30.