全文获取类型
收费全文 | 1092篇 |
免费 | 57篇 |
国内免费 | 1篇 |
专业分类
1150篇 |
出版年
2023年 | 11篇 |
2022年 | 11篇 |
2021年 | 15篇 |
2020年 | 17篇 |
2019年 | 27篇 |
2018年 | 46篇 |
2017年 | 31篇 |
2016年 | 35篇 |
2015年 | 74篇 |
2014年 | 59篇 |
2013年 | 88篇 |
2012年 | 92篇 |
2011年 | 89篇 |
2010年 | 53篇 |
2009年 | 40篇 |
2008年 | 52篇 |
2007年 | 77篇 |
2006年 | 59篇 |
2005年 | 46篇 |
2004年 | 33篇 |
2003年 | 44篇 |
2002年 | 38篇 |
2001年 | 9篇 |
2000年 | 10篇 |
1999年 | 19篇 |
1998年 | 3篇 |
1997年 | 4篇 |
1996年 | 6篇 |
1995年 | 6篇 |
1994年 | 5篇 |
1993年 | 2篇 |
1992年 | 4篇 |
1991年 | 9篇 |
1990年 | 2篇 |
1989年 | 4篇 |
1988年 | 4篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1983年 | 5篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 6篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 2篇 |
1973年 | 1篇 |
排序方式: 共有1150条查询结果,搜索用时 0 毫秒
161.
Karowicz-Bilinska A Plodzidym M Krol J Lewinska A Bartosz G 《Redox report : communications in free radical research》2008,13(5):237-240
The levels of urinary hydrogen peroxide and thiobarbituric acid reactive substances have been compared during the menstrual cycle of 12 regularly menstruating women. Higher level of both indices of oxidative stress (normalized with respect to creatinine content) were found in the luteal phase of the cycle. These results give further evidence for the usefulness of urinary hydrogen peroxide and thiobarbituric acid reactive substances as potential biomarkers of oxidative stress and for the antioxidant action of estrogens. 相似文献
162.
Brain regeneration from pluripotent stem cells in planarian 总被引:3,自引:0,他引:3
Agata K Umesono Y 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》2008,363(1500):2071-2078
How can planarians regenerate their brain? Recently we have identified many genes critical for this process. Brain regeneration can be divided into five steps: (1) anterior blastema formation, (2) brain rudiment formation, (3) pattern formation, (4) neural network formation, and (5) functional recovery. Here we will describe the structure and process of regeneration of the planarian brain in the first part, and then introduce genes involved in brain regeneration in the second part. Especially, we will speculate about molecular events during the early steps of brain regeneration in this review. The finding providing the greatest insight thus far is the discovery of the nou-darake (ndk; ‘brains everywhere’ in Japanese) gene, since brain neurons are formed throughout the entire body as a result of loss of function of the ndk gene. This finding provides a clue for elucidating the molecular and cellular mechanisms underlying brain regeneration. Here we describe the molecular action of the nou-darake gene and propose a new model to explain brain regeneration and restriction in the head region of the planarians. 相似文献
163.
The distribution and diversity of copepods of the genus Calanus were investigated in Hornsund Fjord (on the southwest coast of Spitsbergen) in summer 2001. The Bhattacharya method was used
to sort individuals by species based on their prosome length. The established prosome length boundary values for the Calanus copepodid stages coincided with those defined for the Calanus species from Kongsfjorden (on the northwest coast of Spitsbergen). The predominant species in the main and inner fjord basins
was Calanus glacialis, whereas Calanus finmarchicus was the prevailing species outside Hornsund. Younger copepodid stages (CI–CIII) of both species concentrated in the surface
water layers (0–50∼70 m), while older copepodids (CIV–CVI females) that were ready for wintering stayed in deep layers (50∼70 m
to bottom). Calanus hyperboreus was present in low numbers, predominantly as CIV, and in Hornsund deep water layers. The distribution and diversity of Calanus species complied with the notion that the marine fauna in Hornsund is of a more Arctic character than in Kongsfjorden, a
fjord 260 km to the north on the west coast of Spitsbergen. 相似文献
164.
165.
166.
Jos Luis Gonzlez‐Snchez María Teresa Martínez‐Larrad Cristina Fernndez‐Prez Agata Kubaszek Markku Laakso Manuel Serrano‐Ríos 《Obesity (Silver Spring, Md.)》2003,11(5):603-605
Objective : To investigate the effect of the K121Q plasma cell membrane glycoprotein (PC‐1) polymorphism on the components of the insulin resistance syndrome in a population‐based nationwide multicenter study in Spain. Research Methods and Procedures : The subjects of the study were 293 nonrelated adults (44.7% men and 55.3% women) ages 35 to 64 years randomly chosen from a nationwide population‐based survey on obesity and related conditions, including insulin resistance and cardiovascular risk factors. Obesity‐related anthropometric measurements included blood pressure, oral glucose tolerance test, lipid profile (total cholesterol, high‐density lipoprotein‐ and low‐density lipoprotein‐cholesterol, and triglycerides), plasma leptin, insulin levels by radioimmunoassay, and insulin resistance (homeostasis model assessment). K121Q PC‐1 genotypes were determined by restriction fragment‐length polymorphism‐polymerase chain reaction. Results : Overall Q allele frequency was 0.14, with no differences between obese and nonobese individuals (0.15 vs. 0.13). After adjustment for sex, age, BMI, and degree of glucose tolerance, the Q allele was associated with high plasma leptin and triglyceride levels, but not with insulin resistance. Discussion : The results showed that the K121Q PC‐1 polymorphism in the Spanish population has no significant impact on insulin sensitivity. 相似文献
167.
Agata Bia?oszewska Justyna Niderla-Bielińska Anna Osiecka-Iwan Claudine Kieda 《Cellular immunology》2009,258(2):197-203
Normal chondrocytes are targets for natural killer (NK) cells. Since the mechanism of this phenomenon remains unknown, the present study was aimed at testing whether it is associated with chondrocyte-specific phenotype defined as ability of cartilage cells to produce sulfated glycosaminoglycans (GAG) and express collagen II and aggrecan mRNA. Lysis of rat epiphyseal chondrocytes by syngeneic spleen mononuclear cells (SMCs) was evaluated by 51Cr-release assay. Loss of chondrocyte phenotype following long-term culture resulted in their decreased susceptibility to lysis. Similar effect was also observed after suppression of chondrocyte phenotype by TNF. On the other hand, stimulation of cartilage-specific matrix component synthesis by IGF-1 resulted in increased chondrocyte killing and exogenous chondroitin sulfate A stimulated NK cell-mediated cytotoxicity against chondrocytes and human K562 cells. This suggests that chondrocyte susceptibility to lysis by NK cells depends on chondrocyte-specific phenotype, especially sulfated GAG production. 相似文献
168.
D'Agata V Tiralongo A Castorina A Leggio GM Micale V Carnazza ML Drago F 《Neurochemical research》2009,34(2):327-332
Patients affected by autosomic recessive juvenile parkinsonism (ARJP) exhibit parkin gene mutations with brain decrease in
dopamine D2/D3 binding sites. To date, there are no data indicating whether the reduction in dopamine D3 receptors (DRD3)
may be associated with the expression of specific parkin variants. In the present study we investigated parkin expression
profile in DRD3 knock-out mice brains. RT-PCR analysis was performed to assess qualitative changes in parkin isoforms’ distribution
pattern and in exons’ expression both in wild type controls and dopamine D3 receptor’s knock-out mice. Real-time PCR was performed
to quantify single exons mRNA. Results demonstrated that exons 1, 2, 4, 6, 7, 8, were more expressed in wild type compared
to dopamine D3 receptor KO mice brains while some other (3, 9, 10) were lower expressed. The expression levels of exons 5,
11 and 12 did not change in both animal groups. Our analysis was confirmed by western blot, which showed that parkin protein
levels were influenced by the absence of DRD3. 相似文献
169.
Giuseppe Grasso Ashley I. Bush Roberta D’Agata Enrico Rizzarelli Giuseppe Spoto 《European biophysics journal : EBJ》2009,38(4):407-414
Solid-support based assays offer several advantages that are not normally available in solution. Enzymes that are anchored
on gold surfaces can interact with several different molecules, opening the way to high throughput array format based assays.
In this scenario, surface plasmon resonance (SPR) and mass spectrometry (MS) investigations have often been applied to analyze
the interaction between immobilized enzyme and its substrate molecules in a tag-free environment. Here, we propose a SPR-MS
combined experimental approach aimed at studying insulin degrading enzyme (IDE) immobilized onto gold surfaces and its ability
to interact with insulin. The latter is delivered by a microfluidic system to the IDE functionalized surface and the activity
of the immobilized enzyme is verified by atmospheric pressure/matrix assisted laser desorption ionization (AP/MALDI) MS analysis.
The SPR experiments allow the calculation of the kinetic constants involved for the interaction between immobilized IDE and
insulin molecules and evidence of IDE conformational change upon insulin binding is also obtained. 相似文献
170.
Pluronic block copolymers have been shown to sensitize cancer cells resulting in an increased activity of antineoplastic agents. In the current study we examined a new application of Pluronic bioactivity in potentiating hyperthermia-induced cancer cell injury. DHD/K12/TRb rat adenocarcinoma cells were exposed to low-grade hyperthermia at 43 degrees C with or without Pluronic P85 or Pluronic L61. A range of Pluronic doses, pre-exposure and heat exposure durations were investigated, and the test conditions were optimized. Treatment efficacy was assessed by measurement of intracellular ATP and mitochondrial dehydrogenase activity. Both P85 and L61 in synergy with heat reduced cell viability appreciably compared to either heat or Pluronic alone. Under optimal conditions, P85 (10 mg/ml, 240 mins) combined with 15 mins heat reduced intracellular ATP to 60.1 +/- 3.5% of control, while heat alone and P85 without heat caused a negligible decrease in ATP of 1.2% and 3.8%, respectively. Similarly, cells receiving 120 mins pre-exposure of L61 (0.3 mg/ml) showed reduction in intracellular ATP to 14.1 +/- 2.1% of control. Again, heat or L61 pre-exposure alone caused a minor decrease in levels of intracellular ATP (1.5% and 4.4%, respectively). Comparable results were observed when viability was assessed by mitochondrial enzyme activity. Survival studies confirmed that the loss of viability translates to a long-term reduction in proliferative activity, particularly for L61 treated cells. Based on these results, we conclude that Pluronic is effective in improving hyperthermic cancer treatment in vitro by potentiating heat-induced cytotoxicity in a concentration and time dependent manner. 相似文献