全文获取类型
收费全文 | 2510篇 |
免费 | 144篇 |
国内免费 | 3篇 |
出版年
2023年 | 21篇 |
2022年 | 26篇 |
2021年 | 71篇 |
2020年 | 66篇 |
2019年 | 65篇 |
2018年 | 75篇 |
2017年 | 77篇 |
2016年 | 110篇 |
2015年 | 113篇 |
2014年 | 142篇 |
2013年 | 171篇 |
2012年 | 202篇 |
2011年 | 199篇 |
2010年 | 108篇 |
2009年 | 99篇 |
2008年 | 103篇 |
2007年 | 115篇 |
2006年 | 98篇 |
2005年 | 94篇 |
2004年 | 89篇 |
2003年 | 80篇 |
2002年 | 71篇 |
2001年 | 39篇 |
2000年 | 31篇 |
1999年 | 24篇 |
1998年 | 11篇 |
1997年 | 10篇 |
1996年 | 8篇 |
1995年 | 9篇 |
1994年 | 18篇 |
1993年 | 10篇 |
1992年 | 21篇 |
1991年 | 20篇 |
1990年 | 19篇 |
1989年 | 12篇 |
1988年 | 19篇 |
1987年 | 10篇 |
1986年 | 18篇 |
1985年 | 15篇 |
1984年 | 10篇 |
1983年 | 7篇 |
1982年 | 18篇 |
1981年 | 13篇 |
1980年 | 11篇 |
1979年 | 18篇 |
1978年 | 16篇 |
1977年 | 12篇 |
1976年 | 11篇 |
1974年 | 10篇 |
1968年 | 8篇 |
排序方式: 共有2657条查询结果,搜索用时 15 毫秒
1.
Sohel Md Mahmodul Hasan Akyuz Bilal Konca Yusuf Arslan Korhan Gurbulak Kutlay Abay Murat Kaliber Mahmut Cinar Mehmet Ulas 《Mammalian genome》2020,31(9-12):309-324
Mammalian Genome - Maternal nutrition during pregnancy is one of the major intrauterine environmental factors that influence fetal development by significantly altering the expression of genes that... 相似文献
2.
Demet Tademir Ayegül Karaküük‐yidoan Mustafa Ulali Tuba Takin‐Tok Emne Eln Oru‐Emre Hasan Bayram 《Chirality》2015,27(2):177-188
A series of new chiral thiosemicarbazones derived from homochiral amines in both enantiomeric forms were synthesized and evaluated for their in vitro antiproliferative activity against A549 (human alveolar adenocarcinoma), MCF‐7 (human breast adenocarcinoma), HeLa (human cervical adenocarcinoma), and HGC‐27 (human stomach carcinoma) cell lines. Some of compounds showed inhibitory activities on the growth of cancer cell lines. Especially, compound 17b exhibited the most potent activity (IC50 4.6 μM) against HGC‐27 as compared with the reference compound, sindaxel (IC50 10.3 μM), and could be used as a lead compound to search new chiral thiosemicarbazone derivatives as antiproliferative agents. Chirality 27:177–188, 2015. © 2014 Wiley Periodicals, Inc. 相似文献
3.
Analysis of shear wave propagation in skin; application to an experimental procedure 总被引:1,自引:0,他引:1
An analysis of an experimental procedure used to determine age-related changes in the skin was performed. The experiment is based on the propagation of a shear wave through the skin. The analysis of the experiment was used to determine the effects of parameters such as properties of the skin and subcutaneous fat, skin thickness and experimental conditions on the propagation. Computer simulations showed that at lower frequencies (less than 1000 Hz), measured results depended strongly on skin thickness, while at higher frequencies (2000 Hz) the results were relatively insensitive to both skin thickness and the properties of the subcutaneous fat. Results also depended upon the distance between the applied shear disturbance and the measurement point. The analysis suggests that higher frequency (2000 Hz) experimental results are more indicative of mechanical properties of skin than lower frequency (less than 1000 Hz) results. 相似文献
4.
5.
6.
Kazim Sahin Mehmet Tuzcu Cemal Orhan Hasan Gencoglu Mustafa Ulas Mustafa Atalay Nurhan Sahin Armagan Hayirli James R. Komorowski 《Biological trace element research》2012,150(1-3):291-296
The objective of this experiment was to investigate the effects of supplemental chromium picolinate (CrPic) and chromium histidinate (CrHis) on nuclear factor-kappa B (NF-??B p65) and nuclear factor (erythroid-derived 2)-like 2 (Nrf2) signaling pathway in diabetic rat brain. Nondiabetic (n?=?45) and diabetic (n?=?45) male Wistar rats were either not supplemented or supplemented with CrPic or CrHis via drinking water to consume 8???g elemental chromium (Cr) per day for 12?weeks. Diabetes was induced by streptozotocin injection (40?mg/kg i.p., for 2?weeks) and maintained by high-fat feeding (40?%). Diabetes was associated with increases in cerebral NF-??B and 4-hydroxynonenal (4-HNE) protein adducts and decreased in cerebral nuclear factor of kappa light polypeptide gene enhancer in B cells inhibitor, alpha (I??B??) and Nrf2 levels. Both Cr chelates were effective to decrease levels of NF-??B and 4-HNE protein adducts and to increase levels of I??B?? and Nrf2 in the brain of diabetic rats. However, responses of these increases and decreases were more notable when Cr was supplemented as CrHis than as CrPic. In conclusion, Cr may play a protective role in cerebral antioxidant defense system in diabetic subjects via the Nrf2 pathway by reducing inflammation through NF-??B p65 inhibition. Histidinate form of Cr was superior to picolinate form of Cr in reducing NF-??B expression and increasing Nrf2 expression in the brain of diabetic rats. 相似文献
7.
The complete nucleotide sequence of a mobile element from Trypanosoma brucei is presented along with the sequence of its target site, which shows that the insertion has generated a 7 base pair direct repeat. The cloned copy of the element is a dimeric structure, one end of each monomer consisting of a stretch of 14 A residues preceded by a putative trypanosome polyadenylation signal. Six base pairs of DNA of unknown origin are found in the dimer between the two copies of the element. Evidence suggests that the element is present in the genome mainly as a monomer whose sequence is conserved across several species of trypanosome. The element contains an open reading frame encoding the same 160 amino acid protein in both sequenced copies and is extensively transcribed from both strands. 相似文献
8.
Maurice Jay Bernard Voirin Aurangzeb Hasan Jean-François Gonnet Marie-Rose Viricel 《Biochemical Systematics and Ecology》1980,8(2):127-132
A survey of the leaves and flowers of 62 representatives of the tribe Loteae (Leguminosae) showed the presence of several classes of flavonoids: flavonol 7-methyl ethers (rhamnocitrin, rhamnetin), 8-O-substituted flavonols (gossypetin, limocitrin, sexangularetin, corniculatusin), 3′,4′,5′-tri-O-substituted flavonols (myricetin, mearnsetin, syringetin, laricitrin), proanthocyanidins and flavone-C-glycosides. The trisubstitution of the B-ring and the 8-O-substitution of the A-ring allow the definition of a major group including the genera Dorycnium, Bonjeania, Lotus and Tetragonolobus. The presence of proanthocyanidins and 7-O-methylation determine a second group consisting of the genus Anthyllis. Finally, Securigera, on the basis of its flavonoid chemistry, appears to be rather remote from other members of the tribe. 相似文献
9.
10.
In this study, polyethylenimine (PEI) binding to DNA was examined by isothermal titration calorimetry. Two types of binding modes were found to describe the interactions between these polyelectrolytes in buffers and in water. One type of binding involves PEI binding to the DNA groove because the enthalpy change of this binding mode is positive, and PEI is deprotonated to bind to DNA. Another likely binding mode involves external binding of PEI to the DNA phosphate backbone, accompanied with DNA condensation. The enthalpy change is negative and PEI is protonated when it binds to DNA in this mode. The intrinsic enthalpy change of first binding mode is 1.1 kJ/mol and −0.88 kJ/mol for the second binding mode. This result implies that the PEI is rearranged from the groove to the phosphate backbone of DNA when DNA is condensed. The mechanism of DNA condensation caused by PEI is discussed in this study. 相似文献