全文获取类型
收费全文 | 1924篇 |
免费 | 125篇 |
国内免费 | 2篇 |
专业分类
2051篇 |
出版年
2023年 | 16篇 |
2022年 | 20篇 |
2021年 | 41篇 |
2020年 | 28篇 |
2019年 | 38篇 |
2018年 | 39篇 |
2017年 | 47篇 |
2016年 | 65篇 |
2015年 | 77篇 |
2014年 | 91篇 |
2013年 | 142篇 |
2012年 | 136篇 |
2011年 | 132篇 |
2010年 | 69篇 |
2009年 | 89篇 |
2008年 | 112篇 |
2007年 | 108篇 |
2006年 | 84篇 |
2005年 | 91篇 |
2004年 | 94篇 |
2003年 | 90篇 |
2002年 | 78篇 |
2001年 | 26篇 |
2000年 | 26篇 |
1999年 | 29篇 |
1998年 | 15篇 |
1997年 | 9篇 |
1996年 | 8篇 |
1995年 | 18篇 |
1994年 | 15篇 |
1993年 | 13篇 |
1992年 | 9篇 |
1991年 | 17篇 |
1990年 | 16篇 |
1989年 | 14篇 |
1988年 | 5篇 |
1987年 | 14篇 |
1986年 | 10篇 |
1985年 | 13篇 |
1984年 | 7篇 |
1983年 | 13篇 |
1981年 | 6篇 |
1980年 | 14篇 |
1978年 | 8篇 |
1977年 | 6篇 |
1976年 | 4篇 |
1975年 | 5篇 |
1974年 | 4篇 |
1973年 | 5篇 |
1966年 | 5篇 |
排序方式: 共有2051条查询结果,搜索用时 0 毫秒
81.
Image processing,diagnostic information extraction and quantitative assessment in pathology 总被引:1,自引:1,他引:0
Santinelli A Mazzucchelli R Colanzi P Tinca A Montironi R 《Journal of cellular and molecular medicine》2002,6(1):93-106
As we enter the information age we hold strong beliefs in the benefits of digital technology applied to pathology: numerical representation offers objectivity . Digital knowledge may indeed lead to significant information discovery, and, processing systems might be designed to allow a true evolution of capabilities. Questions arise whether the methodology underlying quantitative analysis provides the information that we need and whether it is appropriate for some of the problems encountered in diagnostic and prognostic histopathology. While one certainly would not dispute the value of statistical procedures, the clinical needs call for individual patient targeted prognosis. 相似文献
82.
Maria Antonietta Stazi Rodolfo Cotichini Valeria Patriarca Sonia Brescianini Corrado Fagnani Cristina D'Ippolito Stefania Cannoni Giovanni Ristori Marco Salvetti 《Twin research》2002,5(5):382-386
The unique opportunity given by the "fiscal code", an alphanumeric identification with demographic information on any single person residing in Italy, introduced in 1976 by the Ministry of Finance, allowed a database of all potential Italian twins to be created. This database contains up to now name, surname, date and place of birth and home address of about 1,300,000 "possible twins". Even though we estimated an excess of 40% of pseudo-twins, this still is the world's largest twin population ever collected. The database of possible twins is currently used in population-based studies on multiple sclerosis, Alzheimer's disease, celiac disease, and type 1 diabetes. A system is currently being developed for linking the database with data from mortality and cancer registries. In 2001, the Italian Government, through the Ministry of Health, financed a broad national research program on twin studies, including the establishment of a national twin registry. Among all the possible twins, a sample of 500,000 individuals are going to be contacted and we expect to enrol around 120,000 real twin pairs in a formal Twin Registry. According to available financial resources, a sub sample of the enrolled population will be asked to donate DNA. A biological bank from twins will be then implemented, guaranteeing information on future etiological questions regarding genetic and modifiable factors for physical impairment and disability, cancers, cardiovascular diseases and other age related chronic illnesses. 相似文献
83.
Plasmepsin II is a key enzyme in the life cycle of the Plasmodium parasites responsible for malaria, a disease that afflicts more than 300 million individuals annually. Since plasmepsin II inhibition leads to starvation of the parasite, it has been acknowledged as an important target for the development of new antimalarials. In this paper, we identify and characterize high-affinity inhibitors of plasmepsin II based upon the allophenylnorstatine scaffold. The best compound, KNI-727, inhibits plasmepsin II with a K(i) of 70 nM and a 22-fold selectivity with respect to the highly homologous human enzyme cathepsin D. KNI-727 binds to plasmepsin II in a process favored both enthalpically and entropically. At 25 degrees C, the binding enthalpy (DeltaH) is -4.4 kcal/mol and the entropic contribution (-TDeltaS) to the Gibbs energy is -5.56 kcal/mol. Structural stability measurements of plasmepsin II were also utilized to characterize inhibitor binding. High-sensitivity differential scanning calorimetry experiments performed in the absence of inhibitors indicate that, at pH 4.0, plasmepsin II undergoes thermal denaturation at 63.3 degrees C. The structural stability of the enzyme increases with inhibitor concentration in a manner for which the binding energetics of the inhibitor can quantitatively account. The effectiveness of the best compounds in killing the malaria parasite was validated by performing cytotoxicity assays in red blood cells infected with Plasmodium falciparum. EC50s ranging between 6 and 10 microM (3-6 microg/mL) were obtained. These experiments demonstrate the viability of the allophenylnorstatine scaffold in the design of powerful and selective plasmepsin inhibitors. 相似文献
84.
Cavestany D Cibils J Freire A Sastre A Stevenson JS 《Animal reproduction science》2003,77(3-4):141-155
To examine the outcomes of adding medroxyprogesterone acetate (MAP) to the ovsynch protocol with the traditional ovsynch protocol in both cycling and anoestrus cows, and to evaluate a resynchronisation protocol, 742 cows averaging more than 40 days postpartum were assigned to the following four treatments: (1) ovsynch (OVS): day 0: GnRH; day 7: PGF2alpha; day 9: a similar dose of GnRH; day 10: timed artificial insemination (TAI), approximately 16-20h later; (2) ovsynch+MAP (MAP): the same ovsynch protocol plus an intravaginal insert made of polyurethane sponge impregnated with 300mg of MAP immediately after the first GnRH treatment and on day 7, at the time of the PG treatment, the sponge was removed; (3) resynchronisation (MAP+ODB): 1mg of oestradiol benzoate (ODB) on day 13 after TAI and a new sponge impregnated with MAP was inserted and; on day 20, 1mg of ODB was given and the sponge removed; and (4) no resynchronisation (No MAP): only oestrus detection and AI at any repeat oestrus detected after TAI. Progesterone was measured in milk samples collected on days -17, -10, -3, 13 and 20 (TAI=day 0). Based on milk P4 at days -17 and -10, 27.4% of the cows were still anoestrus. At PG injection, 67.7% of the cycling and 21.3% of the anoestrus cows had elevated P4. Farm, days postpartum and parity variations were detected in both cases. On day 20 after TAI 42.6% of cycling and 8.3% of the anoestrous cows had elevated P4. Pregnancy rates were similar in both pre-breeding treatments (20%), but interactions (P<0.001) were detected between treatment and cycling activity (for anoestrous cows: MAP=34.9%; OVS=11.1%. Average interval from TAI to subsequent AI was 37+/-3 days. Resynchronisation resulted in more (P<0.001) cows in oestrus between days 18 and 25 after TAI. Conception rate in the MAP+ODB treatment was lower (P<0.05) than the No MAP group (22.8% versus 47.4%). It was concluded that the addition of a progestin to the ovsynch protocol resulted in increased pregnancy rates of cows treated during anoestrus. The benefit of including MAP with the ovsynch protocol for cycling cows is equivocal. 相似文献
85.
86.
Concha MI Molina S Oyarzún C Villanueva J Amthauer R 《Fish & shellfish immunology》2003,14(3):259-273
Antimicrobial proteins and peptides play an important role in the primary defence of epithelial barriers in vertebrates and invertebrates. Here we report the detection of the apolipoproteins A-I and A-II in the epidermis and epidermal mucus of the carp (Cyprinus carpio L.) by immunohistochemistry and Western blot analysis. Both apolipoproteins are major constituents of high density lipoprotein and have been shown to display antiviral and antimicrobial activity in mammals. Therefore the aim of this study was to evaluate if they could be part of the innate immune system of teleost fish. A cDNA clone containing most of the coding region for carp apoA-I was isolated and used as a probe to demonstrate the expression of apoA-I gene in the skin. In addition, mucus apoA-I was shown to be associated to small particles that could correspond to nascent HDL. Finally, affinity purified plasma HDL displayed bactericidal activity in vitro against a non-pathogenic Escherichia coli strain, suggesting a defensive role for HDL and its associated proteins in the carp epidermis and mucus. 相似文献
87.
The ubiquitin-like hPLIC proteins can associate with proteasomes, and hPLIC overexpression can specifically interfere with ubiquitin-mediated proteolysis (Kleijnen et al., 2000). Because the hPLIC proteins can also interact with certain E3 ubiquitin protein ligases, they may provide a link between the ubiquitination and proteasomal degradation machineries. The amino-terminal ubiquitin-like (ubl) domain is a proteasome-binding domain. Herein, we report that there is a second proteasome-binding domain in hPLIC-2: the carboxyl-terminal ubiquitin-associated (uba) domain. Coimmunoprecipitation experiments of wild-type and mutant hPLIC proteins revealed that the ubl and uba domains each contribute independently to hPLIC-2-proteasome binding. There is specificity for the interaction of the hPLIC-2 uba domain with proteasomes, because uba domains from several other proteins failed to bind proteasomes. Furthermore, the binding of uba domains to polyubiquitinated proteins does not seem to be sufficient for the proteasome binding. Finally, the uba domain is necessary for the ability of full-length hPLIC-2 to interfere with the ubiquitin-mediated proteolysis of p53. The PLIC uba domain has been reported to bind and affect the functions of proteins such as GABAA receptor and presenilins. It is possible that the function of these proteins may be regulated or mediated through proteasomal degradation pathways. 相似文献
88.
Freire CA Cavassin F Rodrigues EN Torres AH McNamara JC 《Comparative biochemistry and physiology. Part A, Molecular & integrative physiology》2003,136(3):771-778
To evaluate trends in the osmoregulatory behavior of neotropical, palaemonid shrimps, we investigated osmotic and ionic regulatory patterns in five species of Palaemon or Macrobrachium. The species' life histories depend on saline water to differing degrees, their habitats ranging from the marine/intertidal (P. northropi), through estuaries (P. pandaliformis) to coastal, freshwater streams (M. olfersii, M. potiuna) and inland, continental river systems (M. brasiliense). Hemolymph osmolality, chloride, sodium and magnesium concentrations were measured in shrimps exposed to experimental media ranging from fresh water (<0.5 per thousand ) to concentrated seawater (42 per thousand ) for up to 10 days. The marine and estuarine Palaemon species exhibit well-developed hyper/hypo-osmotic, sodium and chloride regulatory capabilities in mid-range salinities, tending to hyperconform in low salinities. The freshwater Macrobrachium species show variable hyperosmotic, sodium and chloride regulatory capacities, tending to hypoconform or unable to survive at higher salinities. All species hyper-regulate magnesium in fresh water, but hyporegulate strongly in saline media. Palaemonids from the saline habitats show the strongest osmoregulatory capabilities, and fresh water may have been gradually invaded by ancestral species with similar regulatory capacity. However, this regulatory plasticity has been lost to varying degrees in extant freshwater species. 相似文献
89.
90.
Brenner RR 《Prostaglandins, leukotrienes, and essential fatty acids》2003,68(2):151-162
Animal biosynthesis of high polyunsaturated fatty acids from linoleic, alpha-linolenic and oleic acids is mainly modulated by the delta6 and delta5 desaturases through dietary and hormonal stimulated mechanisms. From hormones, only insulin activates both enzymes. In experimental diabetes mellitus type-1, the depressed delta6 desaturase is restored by insulin stimulation of the gene expression of its mRNA. However, cAMP or cycloheximide injection prevents this effect. The depression of delta6 and delta5 desaturases in diabetes is rapidly correlated by lower contents of arachidonic acid and higher contents of linoleic in almost all the tissues except brain. However, docosahexaenoic n-3 acid enhancement, mainly in liver phospholipids, is not explained yet. In experimental non-insulin dependent diabetes, the effect upon the delta6 and delta5 desaturases is not clear. From all other hormones glucagon, adrenaline, glucocorticoids, mineralocorticoids, oestriol, oestradiol, testosterone and ACTH depress both desaturases, and a few hormones: progesterone, cortexolone and pregnanediol are inactive. 相似文献