首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   3591篇
  免费   277篇
  国内免费   142篇
  4010篇
  2024年   6篇
  2023年   18篇
  2022年   79篇
  2021年   97篇
  2020年   110篇
  2019年   113篇
  2018年   136篇
  2017年   89篇
  2016年   175篇
  2015年   245篇
  2014年   255篇
  2013年   276篇
  2012年   347篇
  2011年   322篇
  2010年   194篇
  2009年   179篇
  2008年   238篇
  2007年   200篇
  2006年   191篇
  2005年   142篇
  2004年   130篇
  2003年   92篇
  2002年   75篇
  2001年   31篇
  2000年   31篇
  1999年   26篇
  1998年   9篇
  1997年   16篇
  1996年   17篇
  1995年   12篇
  1994年   15篇
  1993年   10篇
  1992年   11篇
  1991年   13篇
  1990年   9篇
  1989年   14篇
  1988年   9篇
  1987年   8篇
  1984年   6篇
  1980年   4篇
  1978年   4篇
  1976年   6篇
  1975年   4篇
  1973年   4篇
  1971年   3篇
  1970年   3篇
  1969年   5篇
  1968年   3篇
  1967年   4篇
  1965年   4篇
排序方式: 共有4010条查询结果,搜索用时 15 毫秒
101.
102.
在云南省西南边境9县市捕获伊蚊属雌性成蚊16种19367只,用细胞法和乳鼠法分离病毒。从185批6491只白纹伊蚊中分离到病毒2株,从50批1605只剌扰伊蚊中分离到病毒2株,从23批772只窄翅伊蚊中分离到病毒2株,从4批103只阿萨姆伊蚊中分离到病毒1株。其它12种共10396只伊蚊的病毒分离物为阴性。分离到的7株病毒经免疫荧光、酶免疫、血凝抑制和中和试验鉴定,均为乙型脑炎病毒(JEvirus)。白纹伊蚊是野外竹林的优势蚊种。分析认为白纹伊蚊在当地乙型脑炎病毒保存和传播中起重要作用,刺扰伊蚊、窄翅伊蚊和阿萨姆伊蚊亦可参与该病毒的传播。  相似文献   
103.
Summary An inherited (maternal origin) 13/14 translocation with the nucleolus organizer regions eliminated and one centromere was found in an oligospermic man whose wife had had two spontaneous abortions. Meiotic studies revealed all stages of spermatogenesis with a trivalent configuration in diakinesis. Possible reasons for his subfertility and his mother's normal fertility are discussed.  相似文献   
104.
105.
Highly stretchable self‐powered energy sources are promising options for powering diverse wearable smart electronics. However, commercially existing energy sources are disadvantaged by tensile strain limitations and constrained deformability. Here, 1D thread‐based highly stretchable triboelectric nanogenerators (HS‐TENGs), a crucial step toward overcoming these obstacles, are developed based on a highly stretchable coaxial‐type poly[styrene‐b‐isoprene‐b‐styrene] (SIS) elastomer tube. Carbon conductive ink is injected into the SIS tube as a core 1D electrode that remains almost unaffected even under 250% stretching because of its low Young's modulus. To further facilitate power generation by the HS‐TENG, a composite of barium titanate nanoparticles (BaTiO3 NPs) and polydimethylsiloxane (PDMS) is coated on the initial SIS tube to modulate the dielectric permittivity based on variations in the BaTiO3 NPs volume ratio. The 1D PDMS/BaTiO3 NP composite‐coated SIS and a nylon 6‐coated 2D Ni–Cu conductive fabric are selected as triboelectric bottom and top layers, respectively. Woven HS‐TENGs textiles yield consistent power output under various extreme and harsh conditions, including folded, twisted, and washed states. These experimental findings indicate that the approach may become useful for realizing stretchable multifunctional power sources for various wearable electronics.  相似文献   
106.
目的:观察创伤后应激障碍(PTSD)对慢性不可预见性应激(CUS)抑郁模型的影响。方法:采用足底电击的方法建立大鼠创伤后应激障碍模型。成年雄性S-D大鼠40只随机分为四组(n=10):对照组(C组)、PTSD组、CUS组、PTSD+CUS组(P+C组)。在1、7、14、21天测量大鼠体重,并行糖水偏好和强迫游泳实验,在7、14、21天做条件性恐惧实验。结果:与C组相比,CUS组和P+C组体重增加缓慢,PTSD组体重正常。CUS组于第21天出现糖水消耗比例降低,强迫游泳不动时间增加。P+C组于第14天即出现上述抑郁表现。条件性恐惧实验中,PTSD组与PTSD+CUS组僵直时间显著增加,CUS组无明显变化。结论:创伤后应激障碍的动物更易产生抑郁表现。  相似文献   
107.
BackgroundThermodilution technique using a pulmonary artery catheter is widely used for the assessment of cardiac output (CO) in patients undergoing liver transplantation. However, the unclearness of the risk-benefit ratio of this method has led to an interest in less invasive modalities. Thus, we evaluated whether noninvasive bioreactance CO monitoring is interchangeable with thermodilution technique.MethodsNineteen recipients undergoing adult-to-adult living donor liver transplantation were enrolled in this prospective observational study. COs were recorded automatically by the two devices and compared simultaneously at 3-minute intervals. The Bland–Altman plot was used to evaluate the agreement between bioreactance and thermodilution. Clinically acceptable agreement was defined as a percentage error of limits of agreement <30%. The four quadrant plot was used to evaluate concordance between bioreactance and thermodilution. Clinically acceptable concordance was defined as a concordance rate >92%.ResultsA total of 2640 datasets were collected. The mean CO difference between the two techniques was 0.9 l/min, and the 95% limits of agreement were -3.5 l/min and 5.4 l/min with a percentage error of 53.9%. The percentage errors in the dissection, anhepatic, and reperfusion phase were 50.6%, 56.1%, and 53.5%, respectively. The concordance rate between the two techniques was 54.8%.ConclusionBioreactance and thermodilution failed to show acceptable interchangeability in terms of both estimating CO and tracking CO changes in patients undergoing liver transplantation. Thus, the use of bioreactance as an alternative CO monitoring to thermodilution, in spite of its noninvasiveness, would be hard to recommend in these surgical patients.  相似文献   
108.
109.
Chinese hamster ovary (CHO) and human embryonic kidney 293 (HEK293) cells are the most popular host cells for transient gene expression (TGE) of therapeutic proteins. These host cells require high transfection efficiency in order to enhance TGE. Heparan sulfate proteoglycan (HSPG) at the cell surface is known to regulate endocytosis for gene delivery. The HSPG expression in CHO DG44 and HEK293E cells was investigated in an effort to enhance the TGE. Immunostaining of HSPGs followed by confocal microscopy and flow cytometry analyses revealed that CHO DG44 cells possessed a higher amount of cell-surface and intracellular HSPGs than HEK293E cells. The mRNA levels of the representative enzymes involved in the HSPG biosynthesis in CHO DG44, which were determined by quantitative real time PCR, were quite different from those in HEK293E cells. Taken together, the results obtained here would be useful in improving TGE in CHO DG44 and HEK293E cells through genetic engineering of HSPG synthesis.  相似文献   
110.
Thaumatin‐like proteins (TLPs) share structural similarity with the sweet‐tasting thaumatin protein but exhibit antifungal activity by inhibiting growth of fungal pathogens. In a Tenebrio model, two TLP genes were identified by RNA‐sequencing analysis and genome sequencing. Both TmTLP1 and TmTLP2 genes contain 729 nucleotide sequences encoding 242 amino acid residues, including an initiation codon (ATG) and a termination codon (TAA). Interestingly, TmTLPs are proteins with 14 central cysteine residues that may have an important role in structure formation. These data will be used to characterize the innate immune functions of TmTLPs in Tenebrio molitor.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号