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   641266篇
  免费   76287篇
  国内免费   423篇
  2018年   5403篇
  2016年   7189篇
  2015年   10193篇
  2014年   11643篇
  2013年   17213篇
  2012年   18823篇
  2011年   19346篇
  2010年   12988篇
  2009年   12075篇
  2008年   17265篇
  2007年   17815篇
  2006年   16730篇
  2005年   16068篇
  2004年   15622篇
  2003年   15394篇
  2002年   14893篇
  2001年   28586篇
  2000年   28802篇
  1999年   22711篇
  1998年   8048篇
  1997年   8688篇
  1996年   8241篇
  1995年   7821篇
  1994年   7773篇
  1993年   7833篇
  1992年   19367篇
  1991年   19227篇
  1990年   18351篇
  1989年   18164篇
  1988年   16716篇
  1987年   16147篇
  1986年   14920篇
  1985年   15078篇
  1984年   12589篇
  1983年   10860篇
  1982年   8403篇
  1981年   7655篇
  1980年   7267篇
  1979年   12039篇
  1978年   9565篇
  1977年   8895篇
  1976年   8326篇
  1975年   9163篇
  1974年   9787篇
  1973年   9552篇
  1972年   8656篇
  1971年   8006篇
  1970年   6900篇
  1969年   6654篇
  1968年   6026篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Immunization of cancer patients with tumor-specific antigenic peptides is currently being tested in several clinical studies. We have examined the induction of CTL responses in mice after various modalities of peptide vaccination, to explore protocols that could be applied to humans. Our first model antigen was P198, which results from a point mutation in a normal gene. While two immunizations with peptide P198 in SBAS-1c adjuvant induced measurable CTL responses in less than 10% of DBA/2 mice, the addition of IL-12 to the peptide adjuvant mixture resulted in high CTL responses in nearly all mice. This strong enhancing effect of IL-12 was observed with 1,000 and 300 units and decreased gradually as the doses were reduced to 30 units. When IL-12 was replaced by other cytokines acting on T cells or antigen-presenting cells, such as IFN-gamma, IL-2, IL-6, IL-7, GM-CSF or MCP-3, no significant enhancing effect was observed. The same effect of IL-12 was obtained with peptide P1A, which is a major tumor-specific antigen of mastocytoma P815 and is encoded by a gene that is specifically activated in tumors.  相似文献   
992.
993.
994.
995.
996.
Microbiological and biotechnological characteristics of intensification of aerobic processing of organic waste have been reviewed, with a view for revealing two types of correlations: (1) between the quality of the composts obtained and the microorganisms involved in composting and (2) between physicochemical parameters and consumer properties of the composts.  相似文献   
997.
The mesophilic and psychrotolerant microbiota of the air, soil, water, and bottom sediments of the Kinderlinskaya cave (South Urals, Russia) and the factors affecting the structure of microbial communities were investigated. The pattern of microbial distribution in soils was shown to depend on both the configuration of the cave and the level of recreational load. The lowest numbers of bacteria and micromycetes were found in the poorly visited, difficult-to-access sites. Coliform bacteria were revealed in all soil and sediment samples and in some water samples. Micromycetes belonged to 19 genera, with Geomyces pannorum as the dominant species. Air movement was shown to be the main factor affecting the density of the aerial microbiota.  相似文献   
998.
999.
The Rho‐associated (ROCK) serine/threonine kinases have emerged as central regulators of the actomyosin cytoskeleton, their main purpose being to promote contractile force generation. Aided by the discovery of effective inhibitors such as Y27632, their roles in cancer have been extensively explored with particular attention focused on motility, invasion and metastasis. Recent studies have revealed a surprisingly diverse range of functions of ROCK. These insights could change the way ROCK inhibitors might be used in cancer therapy to include the targeting of stromal rather than tumour cells, the concomitant blocking of ROCK and proteasome activity in K‐Ras‐driven lung cancers and the combination of ROCK with tyrosine kinase inhibitors for treating haematological malignancies such as chronic myeloid leukaemia. Despite initial optimism for therapeutic efficacy of ROCK inhibition for cancer treatment, no compounds have progressed into standard therapy so far. However, by carefully defining the key cancer types and expanding the appreciation of ROCK's role in cancer beyond being a cell‐autonomous promoter of tumour cell invasion and metastasis, the early promise of ROCK inhibitors for cancer therapy might still be realized.  相似文献   
1000.
The flowering time is the most susceptible period for primary infection of wheat heads byFusarium spp. During this period spores can be deposited into the opened wheat florets where they may later cause infections. We quantitatively explored the relationship between variables related to the flowering process and the infection level byFusarium graminearum in single spikelets. We imitated open (chasmogamous) and closed (cleistogamous) flowering by injecting well-defined amounts of spores into and between wheat florets. Applying the spores between the florets resulted in weaker disease symptoms and significantly lower amounts ofFusarium mycotoxins. With larger numbers of spores, the disease symptoms became more pronounced and the mycotoxin amounts per spikelet increased significantly. Our results indicate that the probability of primary infection is approximately proportional to the number of spores reaching the open florets during the flowering process. The breeding of wheat lines which flower partially or completely cleistogamously might reduce theFusarium susceptibility in wheat.  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