全文获取类型
收费全文 | 1154774篇 |
免费 | 132138篇 |
国内免费 | 673篇 |
出版年
2018年 | 9865篇 |
2016年 | 13770篇 |
2015年 | 19160篇 |
2014年 | 22477篇 |
2013年 | 32147篇 |
2012年 | 36096篇 |
2011年 | 36415篇 |
2010年 | 24723篇 |
2009年 | 23147篇 |
2008年 | 32781篇 |
2007年 | 33751篇 |
2006年 | 31603篇 |
2005年 | 30481篇 |
2004年 | 30139篇 |
2003年 | 28989篇 |
2002年 | 28268篇 |
2001年 | 51225篇 |
2000年 | 51616篇 |
1999年 | 41144篇 |
1998年 | 15133篇 |
1997年 | 15970篇 |
1996年 | 15119篇 |
1995年 | 14087篇 |
1994年 | 13907篇 |
1993年 | 13736篇 |
1992年 | 34573篇 |
1991年 | 33388篇 |
1990年 | 32642篇 |
1989年 | 31717篇 |
1988年 | 29299篇 |
1987年 | 28284篇 |
1986年 | 26157篇 |
1985年 | 26204篇 |
1984年 | 21810篇 |
1983年 | 18792篇 |
1982年 | 14678篇 |
1981年 | 13211篇 |
1980年 | 12563篇 |
1979年 | 20926篇 |
1978年 | 16612篇 |
1977年 | 15102篇 |
1976年 | 14070篇 |
1975年 | 15359篇 |
1974年 | 16660篇 |
1973年 | 16341篇 |
1972年 | 14755篇 |
1971年 | 13662篇 |
1970年 | 11760篇 |
1969年 | 11096篇 |
1968年 | 10110篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
942.
943.
944.
C57BL/6 nude beige mice (B6 nubq; no T cell, no NK activity) were used as recipients for the adoptive transfer of thymocytes from B6 gld mice (generalized lymphoproliferative disease) which are a model of systemic lupus erythematous. The [gld----nubg] chimeras showed several similarities with gld control mice including the T cell disorders (lymphoproliferation and Con A-response deficiency of splenocytes) and B cell disorders (hyperglobulinemia and elevated anti-single-stranded DNA antibody titers). This suggests that the gld lymphoproliferative disorder has a thymic origin (and does not result from an abnormally extrathymic T cell development) and that the gld T cells have an essential role for the emergence of the disorders of both the T and B cells. 相似文献
945.
The non-newtonian viscous and elasto-thixotropic properties of native and lyophilized pathological bronchial mucus and of polymer solutions (3% and 6% PIB in decalin) used as mucus analogs were analyzed using a cone-plate Carri-Med rheometer and a Couette viscoelastometer that we have specifically developed for measuring the rheological properties of bronchial mucus in clinical practice. The master curves obtained for apparent viscosity under steady conditions as a function of shear rates (gamma: 2.6 X 10(-3) to 6.9 X 10(1) sec-1) were fairly similar, whatever the apparatus used. Under transient conditions, at low shear rate (gamma less than 1.4 sec-1), PIB and mucus exhibited a typical viscoelastic behavior: the shear stress increased slightly up to a steady-state value. At higher gamma, a transitory overshoot of sigma characteristic of the elastothixotropic systems appeared. Such a behavior can be interpreted as resulting from structural changes such as formation and rupture of the three-dimensional network present in bronchial mucus as in polymer solutions. 相似文献
946.
Aggression occurs not only in males but also in females, however, under different sex-specific stimulus and endocrine conditions. After being housed with males, female rats exhibit frequent and intense aggressive behavior toward unfamiliar rats. However, the female residents primarily attack female intruder rats, while the male residents attack males and not females. Altering the hormonal condition of the intruders can modify the behavior that they provoke from the residents. Castration of the male intruders reduces aggression from male residents, but ovariectomy of the female intruders does not alter the behavior of the female residents. Treatment of the gonadectomized intruders with gonadal steroids significantly alters the response of the male residents. Resident-intruder aggressive behavior depends on the presence of the testes in the male residents but not on the ovaries or on lactation in the female residents. Even 7 weeks after ovariectomy the female residents continue to show aggressive behavior toward female intruders. In the same time period the castrated male residents show a marked decrease in aggressive and sexual behavior. 相似文献
947.
Prostaglandin (PG) stimulates female spawning behavior in goldfish and in some other teleosts in which female reproductive behaviors consist of postovulatory oviposition acts. This study examined the effects of PG on female sexual behavior in a teleost fish, Cichlasoma bimaculatum, in which female reproductive behaviors involve both preovulatory courtship and substrate cleaning behaviors, and post-ovulatory oviposition behavior. In females of established pairs, PGF2 alpha injection (5 micrograms, im) at any stage of the spawning cycle, or in the parental phase, rapidly induced substrate cleaning which soon merged into oviposition behavior (without egg release). These results support a role for PG in oviposition behavior of Cichlasoma. However, indomethacin (1 mg, ip), a PG synthesis inhibitor, did not block oviposition in ovulated females which had begun to spawn. Indomethacin may not have lowered PG levels sufficiently. Alternatively, as shown by J.J. Polder (1971, Neth. J. Zool. 21, 265), oviposition behavior may be induced or maintained by other factors associated with the spawning situation. 相似文献
948.
949.
950.