全文获取类型
收费全文 | 2561篇 |
免费 | 162篇 |
国内免费 | 14篇 |
出版年
2023年 | 17篇 |
2022年 | 52篇 |
2021年 | 142篇 |
2020年 | 64篇 |
2019年 | 64篇 |
2018年 | 72篇 |
2017年 | 68篇 |
2016年 | 92篇 |
2015年 | 132篇 |
2014年 | 171篇 |
2013年 | 188篇 |
2012年 | 186篇 |
2011年 | 165篇 |
2010年 | 123篇 |
2009年 | 93篇 |
2008年 | 107篇 |
2007年 | 125篇 |
2006年 | 106篇 |
2005年 | 83篇 |
2004年 | 75篇 |
2003年 | 70篇 |
2002年 | 70篇 |
2001年 | 52篇 |
2000年 | 49篇 |
1999年 | 49篇 |
1998年 | 12篇 |
1997年 | 17篇 |
1996年 | 15篇 |
1995年 | 17篇 |
1994年 | 10篇 |
1993年 | 13篇 |
1992年 | 25篇 |
1991年 | 11篇 |
1990年 | 12篇 |
1989年 | 10篇 |
1988年 | 18篇 |
1987年 | 6篇 |
1986年 | 7篇 |
1985年 | 8篇 |
1984年 | 16篇 |
1983年 | 12篇 |
1982年 | 13篇 |
1980年 | 8篇 |
1978年 | 11篇 |
1976年 | 8篇 |
1975年 | 6篇 |
1974年 | 8篇 |
1973年 | 8篇 |
1971年 | 6篇 |
1967年 | 9篇 |
排序方式: 共有2737条查询结果,搜索用时 15 毫秒
151.
152.
An understanding of the immunomodulating effects of anti-microbial regimens on recombinant interleukin-2 (rIL-2) induced peripheral leukocyte function, i.e. lymphokine-activated killer (LAK)-cell efficacy, would be clinically useful in the selection of commonly employed bone marrow transplantation (BMT) antibiotics to avoid post-transplant complications and optimize anti-microbial, anti-viral, anti-tumor therapies. In this report we evaluated the modulatory effects of a number of antibiotics used in BMT on LAK-cell cytotoxicities, in vitro. Our data showed that, even at serum trough titer, amphotericin B was significantly (P < or =0.05) immunostimulatory, whereas gentamicin, imipenem, and piperacillin, individually, were significantly (P < or =0.05) immunosuppressive. Statistical analysis detected no modulation due to aztreonam, amikacin, cotrimoxazole, or ceftazidime, or any of the six cephalosporins tested at molar equivalent concentration. We conclude that certain antibiotics may be more suitable for infection prone BMT hosts. 相似文献
153.
Khan IA Reddy BV Mahboob M Rahman MF Jamil K 《Indian journal of experimental biology》2002,40(2):162-168
Acute and sub-acute toxic effects of a novel phosphorothionate coded as RPR-II on testis of albino rats were studied. In acute study rats received a single dose of 12.3 mg/kg of RPR-II and sacrificed after 24 hr. For sub-acute study 0.58 mg/kg/day was administered orally to rats for 10 and 21 days. Acute exposure of rats to RPR-II brought no change either in the gonadosomatic index (GSI) or in the structure of testis or in the serum levels of testosterone. Testis glutathione (GSH) level and glutathione S-transferase (GST) activity was significantly decreased whereas, acid phosphatase (AcP) levels increased significantly at 24 hr post-treatment. On 7th day (withdrawal period) after the cessation of the treatment the GSH, GST, AcP, and AkP levels reached to near control. The sub-acute study revealed a significant decrease in GSI on 10th and 21st day of the treatment. In contrast, a time-dependent and significant increased in GSH level and GST activity was observed on 100th and 21st day of post-treatment, except GSH level on 10th day, which was declined. Due to RPR-II treatment the testis AcP and alkaline phosphatase (AkP) levels were significant at both 10th and 21st day of medication but AcP levels were increased whereas AkP levels decreased. The histopathological studies on day 10th showed considerable loss of spermatozoids in testis and at 21st day complete derangement of cellular organization was observed. Testosterone levels decreased significantly on 10th day and remained significantly low at 21st day. However, withdrawal studies showed a recovery in testis of rat treated with RPR-II. GST, GSH, GSI, AcP and AkP values recovered, testosterone levels were also well recovered but recovery in testis structure remained at a low profile. The present study suggests that RPR-II may cause testicular toxicity in rats affecting the normal functioning of testis and it also gave some new information in withdrawal studies. 相似文献
154.
Rahman N Dunstan M Teare MD Hanks S Edkins SJ Hughes J Bignell GR Mancini G Kleijer W Campbell M Keser G Black C Williams N Arbour L Warman M Superti-Furga A Futreal PA Pope FM 《American journal of human genetics》2002,71(4):975-980
Juvenile hyaline fibromatosis (JHF) is an autosomal recessive condition characterized by multiple subcutaneous nodular tumors, gingival fibromatosis, flexion contractures of the joints, and an accumulation of hyaline in the dermis. We performed a genomewide linkage search in two families with JHF from the same region of the Indian state of Gujarat and identified a region of homozygosity on chromosome 4q21. Dense microsatellite analyses within this interval in five families with JHF who were from diverse origins demonstrate that all are compatible with linkage to chromosome 4q21 (multipoint LOD score 5.5). Meiotic recombinants place the gene for JHF within a 7-cM interval bounded by D4S2393 and D4S395. 相似文献
155.
Steroid hormone mimics: molecular mechanisms of cell growth and apoptosis in normal and malignant mammary epithelial cells 总被引:2,自引:0,他引:2
Anti-estrogen (anti-E2) therapy with E2 receptor antagonists has a significant benefit in women with breast cancer, but it may also increase the risk for developing hormone-independent breast cancer for which there is no therapy similar to that used in hormone-dependent breast cancer. Therefore, there is a significant interest in the development of compounds that may provide therapeutic benefit for hormone-independent breast cancer without untoward risks and adverse effects. The estrogen receptor (ER) modulators with both agonistic as well as antagonistic properties may, thus, be exploited for the development of the next generation of compounds for the prevention and/or treatment of breast cancer. In this article, we have discussed the clinical indications, risks, benefits and mechanisms of action of ER modulators and related compounds, particularly indole-3-carbinol (I3C), which may open new avenues for the prevention and/or treatment of breast cancer. 相似文献
156.
157.
Nor?Aini?Abdul?Rahman Yoshihito?Shirai Kazuyuki?ShimizuEmail author Mohd?Ali?Hassan 《Biotechnology and Bioprocess Engineering》2002,7(5):281-288
RecombinantEscherichia coli strain harboring the λp
R-p
L promotor and heterologus poly-β-hydroxybutyrate (PHB) biosynthesis genes was used to investigate the effect of culture conditions
on the efficient PHB production. The expression ofphb genes was induced by a temperature upshift from 33°C to 38°C. The protein expression levels were measured by using two-dimensional
electrophoresis, and the enzyme activities were also measured to understand the effect of culture temperature, carbon sources,
and the dissolved oxygen (DO) concentration on the metabolic regulations. AcetylCoA is an important branch point for PHB production.
The decrease in DO concentration lowers the citrate synthase activity, thus limit the flux toward the TCA cycle, and increase
the flux for PHB production. Since NADPH is required for PHB production, the PHB production does not continue leading the
overproduction of acetate and lactate. Based on these observations, a new operation was considered where DO concentration
was changed periodically, and it was verified its usefulness for the efficient PHB production by experiments. 相似文献
158.
Morgan-Ryan UM Fall A Ward LA Hijjawi N Sulaiman I Fayer R Thompson RC Olson M Lal A Xiao L 《The Journal of eukaryotic microbiology》2002,49(6):433-440
The structure and infectivity of the oocysts of a new species of Cryptosporidium from the feces of humans are described. Oocysts are structurally indistinguishable from those of Cryptosporidium parvum. Oocysts of the new species are passed fully sporulated, lack sporocysts. and measure 4.4-5.4 microm (mean = 4.86) x 4.4-5.9 microm (mean = 5.2 microm) with a length to width ratio 1.0-1.09 (mean 1.07) (n = 100). Oocysts were not infectious for ARC Swiss mice, nude mice. Wistar rat pups, puppies, kittens or calves, but were infectious to neonatal gnotobiotic pigs. Pathogenicity studies in the gnotobiotic pig model revealed significant differences in parasite-associated lesion distribution (P = 0.005 to P = 0.02) and intensity of infection (P = 0.04) between C. parvum and this newly described species from humans. In vitro cultivation studies have also revealed growth differences between the two species. Multi-locus analysis of numerous unlinked loci, including a preliminary sequence scan of the entire genome demonstrated this species to be distinct from C. parvum and also demonstrated a lack of recombination, providing further support for its species status. Based on biological and molecular data, this Cryptosporidium infecting the intestine of humans is proposed to be a new species Cryptosporidium hominis n. sp. 相似文献
159.
The frequency and characteristics of highly thermophilic bacteria in cool soil environments 总被引:4,自引:0,他引:4
Following enrichment at 70 degrees C and 80 degrees C, five highly thermophilic aerobic eubacteria have been isolated from cool soil environments. These organisms show a temperature range for growth of 40-80 degrees C and have optimal and very high growth rates around 70 degrees C with generation times less than 30 min. All isolates are narrow rods, which stain Gram-negative, but have a Gram-positive cell wall structure and only one of five isolates is a spore former. All cultures contain a small proportion of previously unreported extremely long flexuous rods, which can be seen to divide eventually. Biochemical testing of five strains reveals a significant ability to utilize alkanes and some aromatic hydrocarbons. Using polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) of 16S rDNA the five strains were differentiated into three categories, which paralleled the biochemical results. 16S rDNA sequences showed high similarity with thermophilic Bacillus species now reclassified as Geobacillus. These bacteria are present in high numbers in apparently all soils and the question is raised of how these organisms, which are apparently unable to grow at the temperatures experienced in these cool soils, are so prominent. 相似文献
160.