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   6176篇
  免费   462篇
  国内免费   2篇
  6640篇
  2024年   5篇
  2023年   36篇
  2022年   121篇
  2021年   190篇
  2020年   112篇
  2019年   157篇
  2018年   209篇
  2017年   178篇
  2016年   207篇
  2015年   350篇
  2014年   373篇
  2013年   443篇
  2012年   550篇
  2011年   526篇
  2010年   299篇
  2009年   255篇
  2008年   367篇
  2007年   381篇
  2006年   298篇
  2005年   269篇
  2004年   259篇
  2003年   212篇
  2002年   215篇
  2001年   73篇
  2000年   83篇
  1999年   59篇
  1998年   41篇
  1997年   38篇
  1996年   34篇
  1995年   17篇
  1994年   13篇
  1993年   16篇
  1992年   23篇
  1991年   26篇
  1990年   22篇
  1989年   16篇
  1988年   10篇
  1987年   12篇
  1986年   15篇
  1985年   10篇
  1984年   18篇
  1983年   6篇
  1980年   10篇
  1979年   6篇
  1977年   6篇
  1975年   7篇
  1974年   9篇
  1973年   6篇
  1972年   8篇
  1960年   4篇
排序方式: 共有6640条查询结果,搜索用时 0 毫秒
1.
The involvement of gibberellins in the control of flowering of sunflower was studied by direct application of GA3 to the apex of the plants, analysis of the endogenous levels of gibberellin-like substances at different plant ages, and indirectly by the application of paclobutrazol, an inhibitor of gibberellin synthesis. GA3 speeded-up flower initiation and floral apex development. The time of GA3 application was more critical than the amount of GA3 applied. The endogenous levels of gibberellin-like compounds increased significantly by day 15 after sowing. The application of paclobutrazol markedly delayed floral initiation and this effect was also depedent on plant age. Both GA3 and paclobutrazol had their greatest effects between 10 and 20 days after sowing suggesting that an increase in gibberellins in that time period plays a role in floral initiation.  相似文献   
2.
3.
4.
Wound healing capability is inextricably linked with diverse aspects of physical fitness ranging from recovery after minor injuries and surgery to diabetes and some types of cancer. Impact of the microbiome upon the mammalian wound healing process is poorly understood. We discover that supplementing the gut microbiome with lactic acid microbes in drinking water accelerates the wound-healing process to occur in half the time required for matched control animals. Further, we find that Lactobacillus reuteri enhances wound-healing properties through up-regulation of the neuropeptide hormone oxytocin, a factor integral in social bonding and reproduction, by a vagus nerve-mediated pathway. Bacteria-triggered oxytocin serves to activate host CD4+Foxp3+CD25+ immune T regulatory cells conveying transplantable wound healing capacity to naive Rag2-deficient animals. This study determined oxytocin to be a novel component of a multi-directional gut microbe-brain-immune axis, with wound-healing capability as a previously unrecognized output of this axis. We also provide experimental evidence to support long-standing medical traditions associating diet, social practices, and the immune system with efficient recovery after injury, sustained good health, and longevity.  相似文献   
5.
Almeida AP 《Theriogenology》1987,27(2):329-335
A comparison between different superovulatory treatments in dairy cattle was carried out at a commercial embryo transfer unit in Israel. Both pregnant mare serum gonadotrophin (PMSG) and follicle stimulating hormone (FSH) were used, either alone or combined with Syncromate B (SMB). The use of PMSG + SMB significantly decreased the number of corpora lutea present at the time of embryo collection 7 d after insemination, as compared with other treatment regimens. Consequently, a significantly lower number of ova was found in those animals treated with PMSG + SMB. Better superovulatory responses were obtained when FSH, rather than PMSG, was used, regardless of whether they were administered alone or combined with SMB. It was clear that the use of SMB combined either with PMSG or FSH resulted in poorer responses than when either gonadotrophin was used alone.  相似文献   
6.
7.
G-11 staining in Turner's syndrome with mos 45,X/46,X,r(?)   总被引:2,自引:0,他引:2  
Mos 45,X/46,X,r(?) in 4 patients with Turner's syndrome and no signs of virilization, and in one pair of monozygotic twins, one of them with clitoral hypertrophy, was studied using combined cytogenetic techniques and specially G-11 staining for the characterization of the X or Y origin of the rings. In all 6 patients the ring was G-11 positive, attesting its Y origin. Both twins were operated and bilateral streak gonads with a bilateral nodule of testicular tissue were found. Similar small rings were also studied in one patient with mos 46,XX/46,X,r(X) and in one nonvirilized Turner's syndrome patient with a larger ring; in these two cases the ring was G-11 negative. It seems that the small rings occasionally found in Turner's syndrome are more frequently from Y origin and therefore prophylactic gonadectomy should be considered.  相似文献   
8.
Summary A family of unstable mutations at the cut locus in Drosophila melanogaster was obtained under the conditions of hybrid dysgenesis (Gerasimova 1981, 1982). The in situ hybridization experiments have shown that, in the original unstable ct MR2 mutation, the 7B region of the X chromosome (where cut is located) contains a mobile dispersed genetic element, mdg4. All other unstable ct mutations derived from ct MR2 including visible and lethal alleles and unstable ct + reversions, also contain mdg4 in the 7B region. The X chromosomes of the parent strain (wild type) do not contain mdg4 at all. All stable revertants derived from ct MR2, from other unstable ct mutations, or from ct lethals lost mdg4 from the 7B region. The ct MR2 X chromosome does not contain P-elements, although a few copies are present in the autosomes. The instability of the ct MR2./ct MR2 strain remained at a high level for 50 generations (1.5 years) and then rapidly decreased. A new cross with an MRh12/Cy strain (originally used for dysgenesis induction and containing a number of P-elements) increased the instability to a level exceeding the original one. The data strongly suggest that unstable ct mutations in our system are induced by transpositions of mdg4, possibly activated by P-elements.  相似文献   
9.
Insulin and C-peptide (free insulin and C-peptide in insulin-treated patients) were measured after glucose stimulation in nine Type II diabetics on chlorpropamide, eleven insulin-treated maturity-onset diabetics and in 8 normal controls. Dissociation between C-peptide and insulin response to glucose was observed in several diabetics. The relation between incremental molar areas under C-peptide and insulin curves, after glucose challenge (delta CPR - delta IRI/delta CPR) were used to evaluate the hepatic insulin extraction in all but the insulin-treated diabetics. The lower insulin requirements and better control of the short-duration insulin-treated maturity-onset diabetics in relation to the long-term ones could not be explained either by the residual insulin secretion or by the level of "insulin antibodies". The chlorpropamide-responsive patients presented higher insulin levels after the glucose challenge and a lower hepatic insulin extraction than the non-responsive ones.  相似文献   
10.
Seventy patients with diverticular disease of the colon were treated with a high-residue, low-sugar diet including unprocessed bran. Follow-up for an average of 22 months showed marked relief of symptoms in 62 patients. Bowel habit was restored towards normal and abdominal discomfort relieved. Only seven patients were unable to give up the use of laxatives. Eight patients did not tolerate the bran diet, and one of these needed surgical treatment. None of the 62 patients who took the diet needed surgery.  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