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   2388篇
  免费   217篇
  国内免费   5篇
  2021年   33篇
  2020年   19篇
  2019年   23篇
  2018年   38篇
  2017年   26篇
  2016年   57篇
  2015年   118篇
  2014年   122篇
  2013年   141篇
  2012年   214篇
  2011年   157篇
  2010年   101篇
  2009年   86篇
  2008年   119篇
  2007年   118篇
  2006年   131篇
  2005年   94篇
  2004年   98篇
  2003年   88篇
  2002年   66篇
  2001年   74篇
  2000年   59篇
  1999年   73篇
  1998年   27篇
  1997年   22篇
  1996年   12篇
  1995年   13篇
  1994年   19篇
  1993年   15篇
  1992年   34篇
  1991年   38篇
  1990年   31篇
  1989年   21篇
  1988年   21篇
  1987年   20篇
  1986年   26篇
  1985年   26篇
  1984年   13篇
  1983年   19篇
  1982年   19篇
  1981年   14篇
  1980年   16篇
  1979年   20篇
  1978年   18篇
  1977年   11篇
  1976年   17篇
  1975年   15篇
  1974年   11篇
  1973年   15篇
  1972年   13篇
排序方式: 共有2610条查询结果,搜索用时 15 毫秒
1.
2.

Purpose  

Though the development of biofuel has attracted numerous studies for quantifying potential water demand applying life cycle thinking, the impacts of biofuel water consumption still remain unknown. In this study, we aimed to quantify ecological impact associated with corn-based bioethanol water consumption in Minnesota in responding to different refinery expansion scenarios by applying a life cycle impact assessment method.  相似文献   
3.
4.
Study of the posterior abdominal epidermis in hypophysectomized/thyroidectomized male and female tokays following surgery, and subsequent androgen therapy, indicates that, contrary to a previous model, all aspects of β-gland differentiation are under direct androgenic control. On the other hand, another epidermal specialization, the digital foot-pad, shows a pattern of histogenesis directly comparable to that of β-glands, but is unaffected by androgens. These data are discussed with respect to the evolution of glandular epidermal specializations in gekkonid lizards and the possible role of androgens in modifying the control of cell differentiation in lizard epidermis.  相似文献   
5.
6.
Glycosaminoglycans (GAG) were isolated from rat renal glomerular basement membranes subjected to extraction with detergents, and were quantitatively analyzed using a recently described competitive binding assay that is specific for and sensitive to microgram amounts of chondroitin and heparan sulfate. Whereas crude membranes prepared by osmotic lysis contained only 6 micrograms/mg dry wt, subsequent treatment with Triton X-100 or deoxycholate (DOC) increased measureable GAG to about 17 and 34 micrograms/mg, respectively. Repeated freezing and thawing of isolated glomeruli also augmented measurable GAG content in subsequently osmotically lysed membranes to levels observed in Triton-treated membranes. DOC solubilized approximately equal to 15-20% of membrane-associated GAG. Chondroitin sulfate comprised approximately equal to 30% of total GAG, and all of the chondroitin sulfate but only 10% of the heparan sulfate was extracted from the insoluble matrix by DOC. The findings indicate that GAG content of glomerular basement membrane is several-fold higher than previously estimated, and that a substantial portion is bound to cell membrane lipids. The results further suggest two populations of GAG in basement membrane; one that is intercalated with adjacent cell membranes, and another that remains as an integral component of the insoluble matrix after detergent extraction.  相似文献   
7.
8.
A performance-based measure for assessing executive functions (EF) is useful to understand patients’ real life performance of EF. This study aimed to develop a performance-based measure of executive functions (PEF) based on the Lezak model and to examine psychometric properties (i.e., unidimensionality and reliability) of the PEF using Rasch analysis in patients with schizophrenia. We developed the PEF in three phases: (1) designing the preliminary version of PEF; (2) consultation with experts, cognitive interviews with patients, and pilot tests on patients to revise the preliminary PEF; (3) establishment of the final version of the PEF and examination of unidimensionality and Rasch reliability. Two hundred patients were assessed using the revised PEF. After deleting items which did not satisfy the Rasch model’s expectations, the final version of the PEF contained 1 practice item and 13 test items for assessing the four domains of EF (i.e., volition, planning, purposive action, and effective performance). For unidimensional and multidimensional Rasch analyses, the 4 domains showed good reliability (i.e., 0.77–0.85 and 0.87–0.90, respectively). Our results showed that the PEF had satisfactory unidimensionality and Rasch reliability. Therefore, clinicians and researchers could use the PEF to assess the four domains of EF in patients with schizophrenia.  相似文献   
9.
W P Sisk  G L Davis  D Kingsley  A T Chiu  T M Reilly 《Gene》1990,96(2):305-309
Segments of a cDNA encoding human plasminogen activator inhibitor type 1 (PAI-1) were subcloned into a highly regulated and inducible Escherichia coli expression system. A plasmid encoding the mature form of human endothelial PAI-1 produced a functional recombinant molecule, as indicated by its ability to inhibit tissue plasminogen activator's enzymatic activity. In contrast to PAI-1 isolated from human fibrosarcoma cells, the biological activity of the recombinant PAI-1 was not dependent on pretreatment with denaturing agents. A construct encoding a polypeptide lacking the first 80 amino acids of PAI-1 also produced elevated levels of the truncated recombinant protein. However, this truncated product was functionally inactive, indicating that an intact N terminus is required for activity.  相似文献   
10.
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