全文获取类型
收费全文 | 40725篇 |
免费 | 3211篇 |
国内免费 | 1313篇 |
出版年
2023年 | 504篇 |
2022年 | 536篇 |
2021年 | 1172篇 |
2020年 | 1423篇 |
2019年 | 1846篇 |
2018年 | 1580篇 |
2017年 | 1095篇 |
2016年 | 1071篇 |
2015年 | 1412篇 |
2014年 | 2349篇 |
2013年 | 2597篇 |
2012年 | 1490篇 |
2011年 | 1999篇 |
2010年 | 1443篇 |
2009年 | 1911篇 |
2008年 | 2041篇 |
2007年 | 2007篇 |
2006年 | 1932篇 |
2005年 | 1693篇 |
2004年 | 1473篇 |
2003年 | 1265篇 |
2002年 | 1053篇 |
2001年 | 758篇 |
2000年 | 747篇 |
1999年 | 587篇 |
1998年 | 556篇 |
1997年 | 520篇 |
1996年 | 552篇 |
1995年 | 638篇 |
1994年 | 649篇 |
1993年 | 566篇 |
1992年 | 582篇 |
1991年 | 508篇 |
1990年 | 482篇 |
1989年 | 421篇 |
1988年 | 371篇 |
1987年 | 347篇 |
1986年 | 286篇 |
1985年 | 338篇 |
1984年 | 375篇 |
1983年 | 223篇 |
1982年 | 363篇 |
1981年 | 266篇 |
1980年 | 226篇 |
1979年 | 209篇 |
1978年 | 134篇 |
1977年 | 131篇 |
1976年 | 120篇 |
1973年 | 89篇 |
1972年 | 68篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
Classic polycystic ovary syndrome (PCOS) is a high-risk phenotype accompanied by increased risks of reproductive and metabolic abnormalities; however, the local metabolism characteristics of the ovaries and their effects on germ cell development are unclear. The present study used targeted metabolomics to detect alterations in the intermediate metabolites of follicular fluid from classic PCOS patients, and the results indicated that hyperandrogenism but not obesity induced the changed intermediate metabolites in classic PCOS patients. Regarding the direct contact, we identified mitochondrial function, redox potential, and oxidative stress in cumulus cells which were necessary to support oocyte growth before fertilization, and suggested dysfunction of mitochondria, imbalanced redox potential, and increased oxidative stress in cumulus cells of classic PCOS patients. Follicular fluid intermediary metabolic profiles provide signatures of classic PCOS ovary local metabolism and establish a close link with mitochondria dysfunction of cumulus cells, highlighting the role of metabolic signal and mitochondrial cross talk involved in the pathogenesis of classic PCOS. 相似文献
33.
34.
Summary The ability of myogenic cells to migrate perpendicular to the long axis of freely autografted muscles was examined. Rat extensor digitorum longus muscles were divided, and one half was devitalized by repeated freezing in liquid nitrogen while the other half was kept viable in physiologic saline. The halves were reunited with sutures and grafted back into the original muscle bed. At intervals between 5 and 25 days the grafts were removed and examined histologically for the presence of myotubes within the devitalized region. Myotubes were first seen in the devitalized half 10 days postgrafting with the maximum number of myotubes observed after 12 to 15 days. These results indicate that myogenic cells are capable of migration perpendicular to the long axis of the muscle fibers in an autograft. 相似文献
35.
Summary The Drosophila ninaC mutation produces small rhabdomeres with the axial filament of the microvillar cytoskeleton reduced or missing. Using post-embedding immunogold labelling of LR White-embedded eyes, we show that several alleles of this mutation retain positive anti-actin immunoreactivity in the rhabdomeres, comparable to that of wild-type flies. 相似文献
36.
K. Sasikala Ch.V. Ramana P. Raghuveer Rao M. Subrahmanyam 《FEMS microbiology letters》1990,72(1-2):23-28
Abstract Photoproduction of hydrogen, nitrogenase activity (acetylene reduction) and hydrogenase activity (methylene blue dye reduction) were studied in free and alginate immobilized whole cells of a purple non-sulfur photosynthetic bacterium Rhodobacter sphaeroides O.U. 001. Four-fold increase in hydrogen production, two-fold increase in nitrogenase activity and 1.2-fold increase in the hydrogenase activity were observed in immobilized cells compared to free cells. Effect of various inhibitors (CO and C2 H2 ) and electron donor (H2 ) on the above three functions by free and immobilized cells has also been studied. 相似文献
37.
38.
Neil A. Littlefield Bruce S. Hass Lynda J. McGarrity Suzanne M. Morris 《Cell biology and toxicology》1991,7(3):203-214
The effects of magnesium (Mg) restriction on cell growth and the cell cycle were determined in transformed (TRL-8) and non-transformed (TRL-12-15) epithelial-like rat liver cells. Cells were cultured in RPMI 1640 medium in which the Mg concentration was reduced to 0.5, 0.1, and 0 × the concentration in the regular RPMI 1640 media (100mg/l). Cell growth in the transformed cells was not influenced by the Mg restriction as greatly as in the non-transformed cell line. Transit through the cell cycle also exhibited an independence of the Mg in the medium in the transformed cells. When transformed cells were grown for two generations in Mg-limited medium, the growth rate slowed to a rate similar to that demonstrated by the non-transformed cells. Analysis by flow cytometry showed that transit through the cell cycle was minimally slowed in Mg deficient transformed cells; however, transit through the G1 and S phases in the non-transformed cells was slowed. The TRL-8 cells in Mg-limited medium resulted in fewer nuclei in G1 with subsequent increases in the percentages of S-phase nuclei. The TRL 12-15 cells reacted oppositely with the number of G1 nuclei increased and the number of S-phase nuclei decreased. In respect to growth, these results show that epithelial cells respond in a similar manner to Mg-limitation as do fibroblast cells. The transformed cells exhibited a level of independence from Mg in respect to growth, reproduction, and cell-cycle kinetics. 相似文献
39.
40.
Ali Golchin Simzar Hosseinzadeh Masumeh Staji Masoud Soleimani Abdolreza Ardeshirylajimi Arash Khojasteh 《Journal of cellular biochemistry》2019,120(9):15410-15421
Electrospun composite scaffolds show high ability to be used in regenerative medicine and drug delivery, due to the nanofibrous structure and high surface area to volume ratio. In this study, we used nanofibrous scaffolds fabricated by chitosan (CS), poly(vinyl alcohol) (PVA), carbopol, and polycaprolactone using a dual electrospinning technique while curcumin (Cur) incorporated inside of the CS/PVA fibers. Scaffolds were fully characterized via scanning electron microscopy, water contact angle, tensile measurement, hydration, protein adsorption, and wrinkled tests. Furthermore, viability of the buccal fat pad-derived mesenchymal stem cells (BFP-MSCs) was also investigated using MTT assay for up to 14 days while cultured on these scaffolds. Cell cycle assay was also performed to more detailed evaluation of the stem cells growth when grown on scaffolds (with and without Cur) compared with the culture plate. Results demonstrated that Cur loaded nanofibrous scaffold had more suitable capability for water absorption and mechanical properties compared with the scaffold without Cur and it could also support the stem cells viability and proliferation. Cur release profile showed a decreasing effect on BFP-MSCs viability in the initial stage, but it showed a positive effect on stem cell viability in a long-term manner. In general, the results indicated that this nanofibrous scaffold has great potential as a delivery of the Cur and BFP-MSCs simultaneously, and so holds the promising potential for use in various regenerative medicine applications. 相似文献