全文获取类型
收费全文 | 3299篇 |
免费 | 257篇 |
国内免费 | 118篇 |
专业分类
3674篇 |
出版年
2023年 | 44篇 |
2022年 | 67篇 |
2021年 | 96篇 |
2020年 | 91篇 |
2019年 | 105篇 |
2018年 | 86篇 |
2017年 | 84篇 |
2016年 | 100篇 |
2015年 | 105篇 |
2014年 | 133篇 |
2013年 | 209篇 |
2012年 | 104篇 |
2011年 | 128篇 |
2010年 | 84篇 |
2009年 | 140篇 |
2008年 | 144篇 |
2007年 | 126篇 |
2006年 | 130篇 |
2005年 | 112篇 |
2004年 | 112篇 |
2003年 | 86篇 |
2002年 | 90篇 |
2001年 | 82篇 |
2000年 | 81篇 |
1999年 | 61篇 |
1998年 | 91篇 |
1997年 | 57篇 |
1996年 | 65篇 |
1995年 | 66篇 |
1994年 | 71篇 |
1993年 | 65篇 |
1992年 | 70篇 |
1991年 | 57篇 |
1990年 | 56篇 |
1989年 | 33篇 |
1988年 | 54篇 |
1987年 | 47篇 |
1986年 | 37篇 |
1985年 | 66篇 |
1984年 | 31篇 |
1983年 | 32篇 |
1982年 | 44篇 |
1981年 | 29篇 |
1980年 | 24篇 |
1979年 | 11篇 |
1978年 | 14篇 |
1977年 | 8篇 |
1976年 | 7篇 |
1973年 | 9篇 |
1972年 | 9篇 |
排序方式: 共有3674条查询结果,搜索用时 15 毫秒
61.
鳜早期发育阶段骨骼肌纤维的增生与肥大生长 总被引:1,自引:1,他引:1
骨骼肌是鱼体的主要组成部分,也是衡量鱼体生长发育的重要指标.为了解鳜(Siniperca chuatsi)早期发育阶段骨骼肌纤维的生长发育特征,通过制作孵化后1 ~41日龄个体骨骼肌背右侧第一肌节石蜡切片,利用图像分析软件统计该肌节中肌纤维的数目和面积,分析了鳜骨骼肌纤维的增生和肥大生长特征.结果表明,鳜早期发育阶段骨... 相似文献
62.
Martin J. Scott Jennifer A. Lee Matthew S. Wake Kelly V. Batt Trevor A. Wattam Ian D. Hiles 《MABS-AUSTIN》2017,9(1):85-93
Bispecific antibodies (BsAbs) are emerging as an important class of biopharmaceutical. The majority of BsAbs are created from conventional antibodies or fragments engineered into more complex configurations. A recurring challenge in their development, however, is the identification of components that are optimised for inclusion in the final format in order to deliver both efficacy and robust biophysical properties. Using a modular BsAb format, the mAb-dAb, we assessed whether an ‘in-format’ screening approach, designed to select format-compatible domain antibodies, could expedite lead discovery. Human nerve growth factor (NGF) was selected as an antigen to validate the approach; domain antibody (dAb) libraries were screened, panels of binders identified, and binding affinities and potencies compared for selected dAbs and corresponding mAb-dAbs. A number of dAbs that exhibited high potency (IC50) when assessed in-format were identified. In contrast, the corresponding dAb monomers had ~1000-fold lower potency than the formatted dAbs; such dAb monomers would therefore have been omitted from further characterization. Subsequent stoichiometric analyses of mAb-dAbs bound to NGF, or an additional target antigen (vascular endothelial growth factor), suggested different target binding modes; this indicates that the observed potency improvements cannot be attributed simply to an avidity effect offered by the mAb-dAb format. We conclude that, for certain antigens, screening naïve selection outputs directly in-format enables the identification of a subset of format-compatible dAbs, and that this offers substantial benefits in terms of molecular properties and development time. 相似文献
63.
In the present paper we discuss the properties of a recently developed preparation of isolated neurosecretory nerve endings obtained from the rate neurohypophysis. These nerve terminals release two neurohormones, oxytocin and vasopressin, which are easily assayed by radioimmunoassay. Depolarization-induced secretion is dependent on the same parameters as those regulating release from the whole neural lobe. The isolated nerve endings can be permeabilized by means of digitonin; a treatment which gives direct access to the cytoplasm allowing the study of the minimal requirements for inducing neuropeptide release. Furthermore, some nerve endings are large enough to allow the use of the patch-clamp technique. In the present paper we present evidences which show that the isolated neurohypophysial nerve terminals represent a protent tool for studying the mechanism of stimulus-secretion. 相似文献
64.
Preet A Gupta BL Siddiqui MR Yadava PK Baquer NZ 《Molecular and cellular biochemistry》2005,278(1-2):21-31
Vanadium has been reported to have broad pharmacological activity both in vitro and in vivo. Vanadium compound, sodium orthovanadate, Na3VO4, is well known for its hypoglycaemic effects. However, Na3VO4 exerts these effects at relatively high doses (0.6 mg/ml) and exhibit several toxic effects. In the present study lower doses
of Na3VO4 (0.2 mg/ml) are combined with Trigonella foenum graecum seed powder (TSP), another hypoglycaemic agent, to reduce its toxicity without compromising its antidiabetic potential. The
efficacy of the lower doses of Na3VO4 has been investigated in restoring the altered glucose metabolism and histological structure in the sciatic nerves in 21
and 60 days alloxan diabetic rats. A portion of the glucose was found to be channelled from the normal glycolytic route to
polyol pathway, evident by the reduced hexokinase activity and increased polyol pathway enzymes aldose reductase and sorbitol
dehydrogenase activity causing accumulation of sorbitol and fructose in diabetic conditions. Ultrastructural observation of
the sciatic nerve showed extensive demylination and axonal loss after eight weeks of diabetes induction. Blood glucose levels
increased in diabetic rats were normalized with the lower dose of vanadium and Trigonella treatment. The treatment of the diabetic rats with vanadium and Trigonella prevented the activation of the polyol pathway and sugar accumulations. The sciatic nerves were also protected against the
structural abnormalities found in diabetes with Trigonella foenum graecum as well as Na3VO4. Results suggest that lower doses of Na3VO4 may be used in combination with TSP as an efficient antidiabetic agent to effectively control the long-term complications
of diabetes in tissues like peripheral nerve. 相似文献
65.
66.
家兔胫骨前肌肌纤维型的分布研究 总被引:2,自引:0,他引:2
根据家兔胫骨前肌的肌纤维起止、排列和神经支配特征,将该肌分为前、后两个亚体。利用家兔8例16侧胫骨前肌,按上述两个亚体分别取材,作恒冷箱冰冻横切,肌球蛋白ATP酶染色,将肌纤维分为Ⅰ型、ⅡA型、ⅡB型,检测各亚体的肌纤维型构成比例,肌束内肌纤维的分布特征,并用图象分析仪测量各亚体肌纤维横切面积和直径。结果发现,前、后亚体以Ⅱ型纤维居多,前亚体ⅡA型纤维高达35.4%,后亚体Ⅰ型纤维多达24.5%,两者的ⅡB型纤维均达50%左右。而左、右侧之间无差异,肌束周边部内Ⅰ型纤维仅占12.7~13.3%,ⅡB型纤维高达59.9~60.0%,说明受肌束膜压迫影响,ⅡB型肌纤维血供少,以适应无氧酵解的功能。各亚体的Ⅰ型纤维较细,Ⅱ型纤维较Ⅱ粗,A型与ⅡB型二者相似。作者认为,前亚体主要参与快速有力的足背屈运动,后亚体则维持踝关节的稳定,保持足弓的形状和弹性,以便适应该肌的站立、跑动和跳跃的功能。 相似文献
67.
Woo Seung Son Kyu-Sung Jeong Sang Min Lim Ae Nim Pae 《Bioorganic & medicinal chemistry letters》2019,29(10):1168-1172
Highly effective and safe drugs for the treatment of neuropathic pain are urgently required and it was shown that blocking T-type calcium channels can be a promising strategy for drug development for neuropathic pain. We have developed pyrrolidine-based T-type calcium channel inhibitors by structural hybridization and subsequent assessment of in vitro activities against Cav3.1 and Cav3.2 channels. Profiling of in vitro ADME properties of compounds was also carried out. The representative compound 17h showed comparable in vivo efficacy to gabapentin in the SNL model, which indicates T-type calcium channel inhibitors can be developed as effective therapeutics for neuropathic pain. 相似文献
68.
Mohammad ZuberKhalid Mahmood Zia Ijaz Ahmad BhattiTahir Jamil Fazal-ur-RehmanAli Rizwan 《Carbohydrate polymers》2012,87(4):2439-2446
A series of aqueous solutions of poly(vinyl alcohol) of various commercial products were prepared and applied onto the surfaces of cotton and blends of cotton/polyester fabrics. Fourier transform infrared spectrophotometer was used to confirm the molecular structure of the polyvinyl alcohol used. Performance tests such as colorfastness to rubbing (dry and wet) and colorfastness to washing were determined. The controlling variables affecting the performance properties of the finished substrate such as post-treatment with poly(vinyl alcohol) of various commercial trades, concentration and dilutions were studied. Crocking, washing and hue change of the treated dyed and printed fabrics is accompanied by the formation of semi-inter-penetrated network structure due to the presence of the hydroxyl (-OH) groups which make feasible to a number of grafting and physical cross linking reactions of polymer backbone. 相似文献
69.
A Method for Determining the Activity State of Hair Follicles 总被引:3,自引:0,他引:3
Allan J. Nixon 《Biotechnic & histochemistry》1993,68(6):316-325
A histological method is described for determining the proportion of growing hair follicles h skin samples. A variation of the Sacpic staining method, modified for bulk processing, produces high contrast staining of the principal tissue types present in skin. In particular, the inner root sheath is accentuated, facilitating detection of active follicles. Skin preparations from a range of species are used to illustrate structural characteristics of follicles viewed in cross section at various stages of the hair cycle and to establish criteria for classification of the state of activity of follicles. The hair cycle may be divided into quiescent and active states at the points of rapid transition (early pronanagen and mid catagen). Data from repeated skin biopsies from ferrets and goats are also used to demonstrate quantitative estimation of follicle activity, change in compound follicle size, and the relationship between follicle type and fiber medullation. 相似文献
70.
María álvarez-Viejo Yolanda Menéndez-Menéndez Jesús Otero-Hernández 《World journal of stem cells》2015,7(2):470-476
Mesenchymal stem cells, due to their characteristics are ideal candidates for cellular therapy. Currently, in culture these cells are defined by their adherence to plastic, specific surface antigen expression and multipotent differentiation potential. However, the in vivo identification of mesenchymal stem cells, before culture, is not so well established. Pre-culture identification markers would ensure higher purity than that obtained with selection based on adherence to plastic. Up until now, CD271 has been described as the most specific marker for the characterization andpurification of human bone marrow mesenchymal stem cells. This marker has been shown to be specifically expressed by these cells. Thus, CD271 has been proposed as a versatile marker to selectively isolated and expand multipotent mesenchymal stem cells with both immunosuppressive and lymphohematopoietic engraftment-promoting properties. This review focuses on this marker, specifically on identification of mesenchymal stem cells from different tissues. Literature revision suggests that CD271 should not be defined as a universal marker to identify mesenchymal stem cells before culture from different sources. In the case of bone marrow or adipose tissue, CD271 could be considered a quite suitable marker; however this marker seems to be inadequate for the isolation of mesenchymal stem cells from other tissues such as umbilical cord blood or wharton’s jelly among others. 相似文献